articles+ search results

The potential of digital twin (DT) technology to revolutionize industry by enabling virtual simulations of physical systems in real-time has garnered significant attention in recent years. DTs have been widely applied in the manufacturing field to solve various problems, such as shopfloor resource optimization, layout design, commissioning, monitoring, and supervisory control. Cloud-based DT (CBDT) is an emerging concept and shows promise in achieving enhanced remote accessibility, data processing and analysis capabilities, and scalability. However, current CBDT research is still very limited and mainly focuses on theoretical framework that leverages cloud computing advantages in data processing aspects. Yet, practical implementation with technical details for creating a CBDT of a complex manufacturing system is rarely reported, and the interactions between cloud infrastructure and DT modeling and visualization are scarcely investigated. To fill the gaps, this paper first proposes a general CBDT framework for supporting smart manufacturing services. This framework features the integration of modularized cloud intelligence, DT modeling, and DT visualization to achieve enhanced remote accessibility. Moreover, a prototyping system that entails the CBDT-enabled remote monitoring and control services is implemented for a legacy robotic assembly system to partially showcase the process of the proposed framework. The usefulness and remote accessibility of the developed CBDT-based prototype system is further demonstrated with web-based functionalities such as assembly job status update, real-time 3-dimensional DT visualization and simulation of assembly tasks, and remote feedback control over the physical system. Lastly, the prototype system is built upon open-source toolkits (e.g., WebGL) and low-cost commercial software platforms (e.g., Unity and Google Cloud Platform), which could potentially open new opportunities for aiding small-to-medium companies for digital transformation. Future works and limitations are also discussed in the end. [ABSTRACT FROM AUTHOR]

Additive manufacturing of polymers is used for rapid prototyping and in specific applications for the fabrication of final products. As the application range grows to the industrial sector, functional parts require better mechanical properties and tighter tolerance ranges. Short-fiber reinforced polymers can handle higher stresses and significantly less deformation than raw AM polymers, but their surface roughness and viscoelastic behavior are poorly understood. The authors perform the dynamical mechanical analysis, line, and surface roughness characterization of fused filament fabricated composites in this work. Mainly, Onyx, a short carbon-filled fiber nylon thermoplastic composite, was used in three different build orientations: flat, on-edge, and upright. Then, the effect of build orientation on the viscoelastic and roughness properties is discussed. Results showed that despite using the same raw material, printing direction has a moderate impact on the viscoelastic behavior and a significant effect on the surface roughness of the part. For instance, a difference of 25 °C in the Tg was observed between the on-edge and upright build orientation, with the latter the highest. Also, the flat print orientation presented the lowest values in the z-roughness of all the three build orientations analyzed. [ABSTRACT FROM AUTHOR]

FUSED deposition modeling, RESPONSE surfaces (Statistics), MATHEMATICAL models, THREE-dimensional printing, SCANNING electron microscopy, and DENSITY

3D printing technology has revolutionized free-form construction and customization demand through its ease of use, fast production, accurate, regulated deposition, and flexibility with soft functional materials. Fused deposition modeling (FDM) is an ideal technique for the 3D printing of plastics. The low cost, high prototyping precision, and ease of use make it a popular additive manufacturing process. The dimensional stability, quality, functionality, and properties of printed specimens are all affected by the process parameters used in the FDM technology. As such, the present work investigates the effect of the infill pattern and infill density on the PETG mechanical characteristics. The work also finds the optimum parameters to enhance the mechanical properties using the response surface methodology (RSM). Scanning electron microscopy (SEM) was used to study micro-surface defects under different processing conditions. Based on the tensile strength experiments, the concentric pattern was recorded to have the highest UTS, E, and yield values compared to the other designs, at 28.53 MPa, 0.81 GPa, and 20.00 MPa, respectively. In contrast, from compression analysis, the highest compression strength and compression modulus (24.03 MPa and 3.71 GPa, respectively) were obtained for the triangular infill pattern, which absorbs more compressive force compared with the other patterns. Meanwhile, it was also observed that increasing the density from 25 to 75% improves mechanical properties. The RSM analysis reveals the significant parameters for both testing methodologies with mathematical models to predict the properties with 95% certainty. [ABSTRACT FROM AUTHOR]

FUSED deposition modeling, 3-D printers, RAPID prototyping, POLYLACTIC acid, THREE-dimensional printing, and ADDITIVES

Additive manufacturing creates the desired models by adding layers on top of each other. Features such as production flexibility, rapid prototyping, and ease of usage of this technique as compared to traditional techniques play important roles in its widespread industrial applications. However, additive manufacturing also has several shortcomings including inadequate surface quality and dimensional accuracy. Hybrid manufacturing, on the other hand, is a method that emerged in an attempt to solve the problems associated with additive manufacturing. In this study, the deficiencies caused by fused deposition modelling were eliminated with the integration of machining. A hybrid manufacturing machine was produced by adding a cutting tool and DC motor to the 3D printer. All layers were first printed with the 3D printer and then processed with machining, and then the manufacturing was completed. Polylactic acid (PLA) and carbon fibre-reinforced PLA were produced using hybrid manufacturing. The effects of production temperature and layer thickness on surface quality and dimensional accuracy were investigated. As a result of the findings, the production advantages that hybrid manufacturing contributes to these parameters are emphasized. The positive effects of the hybrid approach on dimensional and surface quality have been demonstrated. [ABSTRACT FROM AUTHOR]

ALUMINUM, ALUMINUM sheets, POLYMERS, TOOL-steel, and MATERIAL plasticity

In this research the authors tested the performance of polymer punches, filled with short carbon fibres, produced with fused filament fabrication technology for aluminium sheet deep drawing. An experimental campaign was designed to investigate the geometry accuracy of 99th produced cup and the punches wear mechanism. Results demonstrated that polymer punches are subjected to elastic and plastic deformation that affects cup radius and depth. However, the tolerance comparison with cup produced by conventional steel tools is in a range of tenth of micron; consequently, these punches can withstand the small batch or customised production of one hundred parts. [ABSTRACT FROM AUTHOR]

INVESTMENT casting, SHAPE memory alloys, LIQUID metals, CENTRIFUGAL force, HEAT transfer coefficient, and VIRTUAL prototypes

Comparisons between virtual prototyping and experimental results are notably beneficial for the development of investment casting processes. In this research, such a comparison aimed to study the castability of a Cu-Al-Mn shape memory alloy (SMA) in a modified centrifugal investment casting process that uses centrifugal force to inject the molten metal into the mold. Virtual prototyping was numerically simulated using the ProCAST software applying a rectangular mesh part design. The real and virtual parts were examined for mold filling (castability), pore formation, and solidification time. Using Whitlook's methodology, it was possible to validate the model created in the ProCAST software to simulate the modified investment casting process, detecting results regarding filling, solidification, and porosity with a high degree of accuracy and reliability. In addition to the validation of the developed model, this work also presents estimated values for interface heat transfer coefficient (IHTC) of the metal/mold of aluminum bronze (Cu-Al and Cu-Al-Mn) alloys poured by gravity and centrifugation into plaster molds. Among the obtained values, the IHTC for the 86.7Cu-7.9Al-5.4Mn SMA were estimated at 535 W/m2 K when poured by centrifugal force and 75 W/m2 K by gravity. Ultimately, it was possible to verify that Cu-Al-based shape memory alloy presents a high castability and a low cooling rate. [ABSTRACT FROM AUTHOR]

VIRTUAL prototypes, PRODUCTION planning, MANUFACTURING processes, PREDICTION models, and DESIGN

Multi-material additive manufacturing (MMAM) offers new opportunities to realize components with more integrated features and functionalities in reduced manufacturing costs by eliminating assembly processes. However, the weak mechanical bond between different materials often results in unexpected weakness sections that reside around the multi-material boundary interface. Thus, strengthening the boundary interface is critical to enabling the wide application of MMAM processes in production. Our work approaches this challenge by introducing a new virtual prototyping method to strengthen MMAM parts by facilitating the design and planning process. In our work, a computational part strength prediction model is built, and this model is used to quickly and realistically predict the mechanical strength of a part design within the context of its manufacturing plan. This enables fast iteration of redesigns to create parts that can be directly printed with improved strength. Compared to the commonly used design of experiment-based approaches, this new virtual prototyping method offers a more time and cost-efficient solution that delivers better designs in a shorter design cycle and with no material wastage by eliminating the need for physical test printing. [ABSTRACT FROM AUTHOR]

ORBITS (Astronomy), FIBERS, INJECTION molding, HEALING, BENDING strength, LASERS, LASER therapy, and FRACTOGRAPHY

Fused filament fabrication is one of the most widely used additive manufacturing processes for producing thermal plastic polymer materials due to the affordable cost and capability to build objects with complex structures. However, parts fabricated with this process exhibit lower mechanical strength when compared to parts manufactured using traditional methods. In this work, an in-process orbiting laser healing technique is developed and implemented on a 3D printer to enhance mechanical strength by improving interlayer adhesion. The orbiting laser assembly can position and align the laser-heated spot before the change of nozzle direction occurs, ensuring that the previous layer is heated prior to material deposition. This laser-heating technique increases the bending strength along the build direction by 40% and reaches 88.9% of the strength along the longitudinal direction. With this technique, the displacement at fracture also increased by 54.3% compared to control sample. The thermal profile of the melting pool and fracture surface was further characterized using a thermal camera and SEM to support the effect of laser heating on polymer microstructure, respectively. Due to its enhanced print quality and lower cost, this technique has the potential to expand the application field of fused filament fabrication to small batch and series production that are currently dominated by injection molding, as well as the high-quality prototyping field. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, MODELS & modelmaking, POLYLACTIC acid, HONEYCOMB structures, MOLECULAR force constants, METAMATERIALS, and METAHEURISTIC algorithms

This research aims at enhancing the performance of scale-model scooter decks by investigating various architected cellular metamaterial and bio-inspired core structure designs, such as honeycomb, tetrachiral, re-entrant, arrowhead, and star-shaped arrangements. An initial effort is made toward the design and rapid prototyping of small-scale deck with a uniform honeycomb core structure. More specifically, polylactic acid is utilized to fabricate complex structures via fused filament fabrication technique. Investigation is then focused on its mechanical performance, such as its bending properties obtained through a three-point bending test. Simulations are also conducted with different core configurations using a geometrically non-linear finite element method which is implemented. Experiments are carried out to verify the numerical results. After validation, various patterns are modeled, and eventually, it is observed that the functionally graded arrowhead structure has the best bending resistance, compared to other bio-inspired and mechanical metamaterial structures. At a constant force of 845 N, the functionally graded arrowhead design lowers the deflection in the middle of the scale model of scooter deck by up to 14.7%, compared to the uniform arrowhead structure. Furthermore, comparing the tetrachiral and functionally graded arrowhead configurations at a constant force, a 30% reduction in central deflection was observed. Due to the lack of similar results and designs in the specialized literature, this work could potentially advance the state-of-the-art scooter core designs and provide designers with architectures that could enhance the performance and safety of scooters. [ABSTRACT FROM AUTHOR]

3D printing by fused filament fabrication (FFF) can produce complicated products often used for prototyping. The major challenge for this technology is the production of functional parts with suitable mechanical properties. It is possible to improve the mechanical properties of the parts produced with FFF by correctly selecting and combining the process parameters. In this research, acrylonitrile butadiene styrene plus (ABS plus) samples with three variable parameters, including infill density, layer thickness, and raster angle, were printed to evaluate the ultimate tensile strength (UTS) and fracture strain in the tensile test. The two-dimensional digital image correlation (2D-DIC) technique measured the full-field surface strain. Before starting the test, the appropriate contrast of the sample surface was ensured using a histogram. The results were validated and predicted using response surface methodology (RSM). Prediction of the results using the quadratic model reveals that the mean error obtained for UTS and fracture strain was 2.96% and 2.87%, respectively. The analysis of variance (ANOVA) was used to validate the model. Also, the effect of the individual and interaction parameters on the response was examined. The raster angle parameter, directly related to transferring the load to the sample, was recognized as the most crucial parameter affecting both responses. The optimization results to maximize UTS and fracture strain values indicate 73.42% infill density, 0.227 mm layer thickness, and 0° raster angle, leading to UTS of 34.92 MPa and fracture strain of 3.59%. Finally, the field emission scanning electron microscope (FESEM) is employed to investigate the failure mechanism in the samples. [ABSTRACT FROM AUTHOR]

MULTIDISCIPLINARY design optimization, TECHNOLOGICAL innovations, NEW product development, and MICE

Additive manufacturing has seen remarkable growth in recent years and a rising evolution of industrial applications for direct manufacturing. Many industries are looking to adopt this technology to take advantage of its benefits, such as design freedom and component mass reduction. However, design teams need to gain the experience, training, and design knowledge that allow them to consider the capabilities of this new technology. Existing design methodologies for additive manufacturing only consider a subset of the design process. Most research studies focus on either design heuristics, or design principles, or design rules, and do not provide a structuring and comprehensive design methodology tailored to additive manufacturing. This paper aims to provide designers and companies with a systematic and creative integrated design methodology in a user-centered approach. The benefits and constraints of AM are structured for greater understanding, through the design heuristics, principles, and design rules related to the process. Furthermore, we integrate visualization and prototyping throughout the process to ensure product quality and user fidelity. Hence, this study aims to provide a new methodology for product design for AM that covers the entire process, from the requirement to production. The proposed user-centered methodology integrates the different stakeholders, throughout the project life cycle. Finally, we evaluate the proposed methodology by designing a left-handed mouse as a case study. Novice designers for new product development with AM can also use this solution. [ABSTRACT FROM AUTHOR]

ROBOTIC welding, INTELLIGENT sensors, OPTICAL scanners, LAXATIVES, DIGITAL twins, LASER measurement, and SMALL business

The aim of this paper is to describe the methods used to adapt the robotic system as well as the design, simulation, digitization, and verification of the robotic workplace for intelligent welding of small-scale production. Small-scale production in small and medium-sized enterprises is characterized by a high level of type variability of products. It was a requirement to design and verify a robotic positioning and welding workplace with a high degree of ability to automatically adapt to processing of various objects. This paper deals with the design and verification of robotic smart systems that contribute to variability of a robotic workplace for intelligent welding of small-scale production such as positioning and holding of the to-be-welded parts by two synchronized robotic manipulators, robotic welding, robotic picking systems using 3D scanners, 2D laser scanner measurement of gap geometry, and quick-change system of robotic grippers with a force-torque sensor. Before testing the robotic manipulation and robotic welding of products of various sizes and shapes, the design of the workplace was verified using its digital twin. The robotic workplace for intelligent welding of small-scale production also includes tools for digitization. [ABSTRACT FROM AUTHOR]

LASER deposition, FERRITIC steel, RESIDUAL stresses, SURFACE roughness, HIGH temperatures, and LASER beam cutting

Metal-laminated tooling provides a fast and cheap manufacturing concept. In this study, laser metal deposition (LMD) is used for reducing and eliminating the stair step effect in a metal-laminated bending die. Preheating could decrease the undesired residual stresses in additive manufacturing, thus a systematical analysis of the effect of preheating of the laminae on the surface quality and mechanical properties of the bending die is performed. Ferritic steel sheets (S355 MC) with a thickness of 2 mm are laser cut and stacked up to manufacture the laminated bending die with a radius of 6 mm. The sheets are joined and the stair steps are filled with LMD with stainless steel powder 316L-Si. The initial temperature of the tool sheets (substrates), beside room temperature, is elevated up to 300 °C. The effect of the preheating on the surface roughness, shape deviation, hardness, and residual stresses of the die are investigated. The mean height of the surface increases by 59% at elevated temperatures. However, the tensile residual stress parallel to the weld direction at the middle of the deposited area decreases only around 25%. The functionality of the forming tools manufactured by this method is proven by bending of DC06 and HC380LA sheets. [ABSTRACT FROM AUTHOR]

NUMERICAL control of machine tools, RAPID prototyping, CONTINUITY, GEOMETRIC modeling, THREE-dimensional modeling, MACHINING, and METAL cutting

Efficient and productive manufacturing of freeform shapes requires a suitable three-dimensional CAD model at the entrance to the CAM system. The paper deals with the impact of NURBS or B-spline CAD model geometric continuity on the accuracy and productivity of 5-axis ball-end milling of freeform surfaces. The relationship between a different order of CAD model geometric continuity and the quality of the toolpath generated in CAM system is analysed and demonstrated on an example of a Blisk blade profile. In order to reveal the effect of CAD geometry on the quality of the machined surface, linear interpolation of cutter location points, i.e. piecewise linear discrete toolpath, is considered. Also, no further smoothing of the toolpath is applied. The distance of the cutter location points is commonly used as the indicator of toolpath quality. In addition, the discrete curvature of a linear discrete toolpath is introduced here, and its dependence on the curvature and continuity of the underlying CAD model is demonstrated. In this paper, it is shown that increasing the order of CAD model geometric continuity significantly eliminates sharp changes in the distance of cutter location points, and smoothes the discrete curvature of the toolpath. Finally, it is experimentally verified that increasing the continuity of the CAD model from G0 to G3, while maintaining the same cutting conditions, leads to an increase in workpiece accuracy and a reduction in machining time, without the need to smooth the toolpath generated in the CAM system. [ABSTRACT FROM AUTHOR]

ONTOLOGIES (Information retrieval), FLEXIBLE manufacturing systems, PRODUCT life cycle, INTERNET, and MANUFACTURING processes

The new generation of smart manufacturing technology enables upgrading within the manufacturing industry, as well as increase the complexity of manufacturing systems. The integration of information and ontology across the full life cycle of a product involves multi-scientific and multi-disciplinary dimensions. It requires a deep integration of industry chain enterprises in the process of domain ontology sharing and digital asset collaboration to achieve an efficient "new demand → existing ontology → innovation → new product → new ontology" agile manufacturing paradigm transfer. A digital-twin and ontology collaboration framework based on the industrial internet identification and resolution system (I3R system) is presented in this paper. Taking flexible manufacturing system (FMS) as an example, the four core key technologies required in this framework are described in detail: (1) a generic digital-twin modeling approach for the full life cycle of FMS; (2) ontology for the full life cycle of FMS; (3) digital-twin data collection technology for human-cyber-physical system (HCPS) in smart manufacturing; (4) distributed collaboration framework based on I3R. To illustrate in detail how the proposed methods and techniques can be applied in reality, we show different application scenarios based on the proposed methods and techniques in the various stages of the full FMS life cycle. Meanwhile, the implementation method of the I3R system-based digital-twin collaborative prototyping platform for industry chain cooperative enterprises is discussed, as well as the idea of its derived top-level application. [ABSTRACT FROM AUTHOR]

RAPID prototyping, MACHINING, SURFACE roughness, IMPELLERS, MACHINERY, DEEP drawing (Metalwork), and SHEET metal work

In the deformation machining (DM) approach, the machining and incremental forming operations are combined to utilize the strengths of the two processes to produce monolithic components with thin structures using a single setup. DM offers a high degree of flexibility to manufacture monolithic components in comparison to conventional techniques. Some freeform monolithic products are difficult to machine with the 3-axis machining approach due to restricted entry of the tool in certain portions of the geometry. This paper presents a novel double-sided deformation machining (DSDM) technique to manufacture freeform double-sided monolithic components. As a test case, a double-sided monolithic impeller-shaped structure with freeform blades is manufactured with the proposed technique. For this, first, a blank is machined to create the required structure and blades of desired thickness. These machined structures are used as preforms for the incremental forming (bending) of the blades to the final shape. As the existing commercial toolpath development packages are not compatible with the DM process, a novel feature-based double-sided combined machining-forming toolpath is developed for the DSDM operation. Here, the blades are deformed separately and sequentially. This avoids the collision issue and achieves a faster forming operation. To evaluate the quality of the monolithic components developed, a few response parameters, like the process forces, the geometrical accuracy in terms of springback, and the surface roughness, are reported. [ABSTRACT FROM AUTHOR]

ELBOW joint, COMPLIANT behavior, HUMAN-robot interaction, ELBOW, LEGAL motions, and COMPLIANT mechanisms

New technological advances are changing the way robotics are designed for safe and dependable physical human–robot interaction and human-like prosthesis. Outstanding examples are the adoption of soft covers, compliant transmission elements, and motion control laws that allow compliant behavior in the event of collisions while preserving accuracy and performance during motion in free space. In this scenario, there is growing interest in variable stiffness actuators (VSAs). Herein, we present a new design of an anthropomorphic elbow VSA based on an architecture we developed previously. A robust dynamic feedback linearization algorithm is used to achieve simultaneous control of the output link position and stiffness. This actuation system makes use of two compliant transmission elements, characterized by a nonlinear relation between deflection and applied torque. Static feedback control algorithms have been proposed in literature considering purely elastic transmission; however, viscoelasticity is often observed in practice. This phenomenon may harm the performance of static feedback linearization algorithms, particularly in the case of trajectory tracking. To overcome this limitation, we propose a dynamic feedback linearization algorithm that explicitly considers the viscoelasticity of the transmission elements, and validate it through simulations and experimental studies. The results are compared with the static feedback case to showcase the improvement in trajectory tracking, even in the case of parameter uncertainty. [ABSTRACT FROM AUTHOR]

CLASS A metals, SURFACE finishing, RAPID prototyping, SURFACE texture, ENVIRONMENTAL risk, METAL powders, and POWDERS

Additive manufacturing (AM) has transformed the way of manufacturing metallic parts due to its ability of rapid prototyping, customization, reduced waste, and cost-effectiveness for small-batch manufacturing, and it has been increasingly replacing milling and molding processes. Directed energy deposition and powder-based fusion AM are the major classes of metal AM technologies, which are already well-established to print high-volume and small complex parts, respectively. However, the increasing demand for the fabrication of small devices, due to the miniaturization trend that is occurring in several industries fields, requires the development of specialized metal AM systems with the ability to increase the resolution of the printed parts. Thus, micro-metal additive manufacturing (MMAM) systems are now being developed using a scaling-down approach of the currently well-established metal AM technologies. In this review, a state-of-art analysis of the existing body of knowledge including the existing MMAM technologies, process parameters, and main results associated with MMAM was compiled and critically discussed. A surface texture index is defined, and a comparison of the trade-off between surface finishing and the building rate was performed considering the metal AM processes and the already developed scaled-down technologies. Additionally, other important aspects of the process (e.g., cost-related, health, environmental risks) are discussed. [ABSTRACT FROM AUTHOR]

KETONES, POLYETHER ether ketone, RAPID prototyping, YOUNG'S modulus, DIFFERENTIAL scanning calorimetry, and POLYLACTIC acid

Fused filament fabrication (FFF) is an additive manufacturing (AM) technology which is rapidly progressing from production of prototypes to manufacture of customized end use parts for the automotive, biomedical, and aerospace industries. The properties of manufactured parts have been proven to be dependent on not only the material's inherent properties but importantly the FFF process parameters. Commodity thermoplastics such as acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) have been on the forefront of FFF research since its development. However, as FFF technology progresses from rapid prototyping to rapid manufacturing, understanding the behaviour of high-performance engineering thermoplastics in this process is imperative. While previous studies have investigated the effects of FFF process parameters on polyether ether ketone (PEEK) and polyetherimide (PEI), more limited research has been performed on polyether ketone ketone (PEKK) despite its widespread applications in the biomedical and aerospace industries. This study investigated the effects of process parameters including build orientation, infill pattern, number of contours and raster angle on the tensile properties of PEKK. Tensile test results showed significant variations in Young's modulus and elongation at break. Statistical analysis was performed which determined the optimum process parameters to maximize tensile properties and revealed that build orientation was the most significant parameter, followed by number of contours. Fractography showed differences in failure mode and ductility among the sample groups. Analysis using differential scanning calorimetry (DSC) showed that the difference in percentage crystallinity among sample groups was not significant and thus the varied tensile properties was improbable to be due to differences in crystallinity developed within the specimens. Further analysis revealed that a variation in FFF process parameters can cause differences in percentage, size and location of porosity which in turn affects mechanical properties. [ABSTRACT FROM AUTHOR]

FUSED deposition modeling, THREE-dimensional printing, COORDINATE measuring machines, RAPID prototyping, and ENGINEERING design

Despite the large diffusion of additive manufacturing, and markedly fused filament fabrication, some quality aspects of the 3D printed parts have not been dealt with sufficiently. This applies particularly to geometric accuracy and the influence process parameters have on it. The paper describes an experiment in which 27 copies of a part were manufactured by means of a desktop fused filament fabrication device while manipulating layer thickness, printing speed, and number of contours. The effect of such process parameters on five typologies of geometric deviations and the duration of the printing process was assessed. While all the process parameters showed effects on both the printing time and some geometric deviations, the number of contours resulted as the most critical factor. The paper includes a proposal to optimize geometric accuracy and the rapidity of the process, which foresees the maximization of the number of contours, the minimization of the layer thickness, and the use of an intermediate value for printing speed. [ABSTRACT FROM AUTHOR]

FABRICATION (Manufacturing) and POLYMERS

As a promising technology capable of transforming the conventional manufacturing techniques, the use of additive manufacturing (AM) has span beyond the prototyping it was initially known for, and its use is currently revolutionising the future of the manufacturing and research world. A review of some of the advances made in the additive manufacturing of polymers and their composites is presented in this paper. Some of the advantages and disadvantages of the different AM techniques used in polymer composites (PC) fabrications are presented, and the different areas of applications of the AM fabricated PC are highlighted. Also highlighted are some of the potentials and challenges associated with the fabrication of components using 4D printing. Finally, the paper presents the prospects and the endless opportunities that abound with the AM of polymeric materials. [ABSTRACT FROM AUTHOR]

METAL stamping, SHEET metal, FIBER-reinforced plastics, STRAIN rate, RAPID tooling, and THREE-dimensional printing

3D printed polymer composite materials offer a cost-effective and rapid tooling option for prototyping, and low-cost, low-volume sheet metal forming applications. Due to the high anisotropy in mechanical properties of 3D printed composites, accurate characterization and finite element modeling of the material become paramount for successful design and application of these forming tools. This paper presents experimental characterization of 3D printed fiber–reinforced polymer composite material at various strain rates. A homogenized material model with orthotropic elasticity and the Hill 1948 anisotropic yield criterion were then calibrated based on these experimental data. Finite element simulations of the stamping of high-strength steel sheets using composite tooling were performed, and tool deformation was predicted and compared with experimental measurements. FE simulation results were in good agreement with stamping experiments performed with polymer tooling. It was found that the anisotropy and strain rate sensitivity of 3D printed polymer composites play a significant role in their performance as tooling materials. [ABSTRACT FROM AUTHOR]

FREE surfaces, SIMPLE machines, RAPID prototyping, SPLINES, PROBLEM solving, DATA structures, and SPLINE theory

Ultra-precision turning technology (UPT) plays a critical role in optical freeform surface manufacturing. There are researches focusing on solving problems of UPT tool path generation of freeform surfaces, but most of them are regardless of surface boundary contours. It is not convenient to generate path to machine complex structural parts with more surfaces simultaneously if boundary contours are ignored. To further improve UPT machining capacity, in our study, how to solve the UPT path generation problem about freeform surface with free boundary contours, which is called double free face (DFF), is focused. The Archimedean spiral is generated and discrete to driving point sequence, which is similar to the previous studies. Innovative contents are described as below. First, data structure of DFF topology is proposed, which contains expressions of the surfaces and boundary contours. And then, the surface projection and boundary wire projection algorithms are designed to calculate the projected tool location point. When the projected point is a tangential contact to the surface, this point is cutting point, and when the tool is projected to the contour wire or not projected to any geometry element, the point is not cutting point. How to judge whether the projected point is inside the face or outside is introduced. Third, the transition path is calculated by interpolating the two adjacent cutting paths using iterative cubic spline interpolation method to ensure enough movement smoothness. Finally, tool paths of case DFFs are generated and machined to verify the effectiveness of this proposed UPT path generation strategy. [ABSTRACT FROM AUTHOR]

MICROFLUIDIC devices, RAPID prototyping, SURFACE energy, MANUFACTURING processes, SURFACE roughness, and CELL separation

Generally, machining of polymeric microfluidic devices is a one-step manufacturing process. It is economical compared to lithography and can be used for batch production and rapid prototyping. However, surface properties are modified during machining due to the viscoelasticity property of polymers and the mechanical nature of fractures. In this present work, the manufacturing capability of the mechanical micromachining process of polymers has been explored. Surface characteristics like surface roughness, surface energy, and burr formation are investigated. Surface quality is chosen as a contributing factor for defining the manufacturing capability as it is one of the significant factors influencing the physics of fluid flow in microchannels. In the present work, several manufacturing methods, such as 3D printing, hot embossing, photolithography, and mechanical micromachining, were considered. The surface energy of various surfaces machined using the abovementioned methods is evaluated and compared. It has been observed that mechanical micromachining is the most suitable methods as they have less wettability with lower surface energy. Further investigations are carried out by machining microfluidic devices using polymethylmethacrylate (PMMA) and polycarbonate (PC) materials, as they are extensively used in biomedical applications. Surface roughness was measured on the PMMA and PC surfaces after milling. The surface roughness values and surface energies are used for evaluating the suitability of the machining process to fabricate microfluidic devices. Microfluidic devices with serpentine channels were machined on PMMA with a depth of 50 µm and width of 200 µm for evaluating inertial focusing in the channels. These devices were further evaluated for blood cell separation at different dilution rates. It is observed that PMMA is the preferable choice for fabricating microfluidic devices using mechanical micro-milling. [ABSTRACT FROM AUTHOR]

HIGH strength steel, CLAMPS (Engineering), and SHEET metal

Flexible Roll Forming (FRF) allows the forming of components with a variable cross section along the length of the component. However, the process has only limited application in the automotive industry due to wrinkling in the flange which currently prevents the forming of high strength steels and limits the part shape complexity. This paper presents a new forming technology, Incremental Shape Rolling (ISR), where a pre-cut blank is clamped between two dies, and then a single forming roll is used to incrementally form the material to the desired shape. The new process is similar to some Incremental Sheet Forming (ISF) approaches but with the difference that Incremental Shape Rolling (ISR) allows the manufacture of longitudinal components from high strength metal sheets. In this work, a numerical model of the ISR of a straight section is developed. Experimental prototyping trials are performed and are used to validate the numerical model which is then applied to analyse the new forming process. The results show that in ISR, tensile residual strains are developed in the flange. Flange wrinkling is observed and directly linked to the number of forming passes that are used in the process. [ABSTRACT FROM AUTHOR]

RAPID prototyping, TITANIUM powder, ELECTRON beams, ALLOY powders, ALUMINUM composites, LASER beams, MANUFACTURING processes, and TENSILE strength

In this work, aluminum 6061-based powder blend feedstocks with reactive Ti-B/C additions were employed in two different additive manufacturing processes, laser powder bed fusion (L-PBF) and electron beam freeform fabrication (EBF3), to create micro- and nanoscale ceramic and intermetallic inoculants in situ and to examine the effect of feedstock inoculant content on microstructure and mechanical properties. Products of the reaction synthesis process were identified with X-ray diffraction and energy-dispersive spectroscopy to include Al3Ti, TiC, and TiB2. Electron back-scatter diffraction revealed significant grain refinement up to 74 × , mitigation of solidification cracking, and formation of an equiaxed grain structure with the addition of just 2 vol.% inoculant. Inoculants formed in situ were seen to induce approximately 5 × more grain refinement than pre-existing inoculants. The highest ultimate tensile strength and Young's modulus of 368 ± 2 MPa and 92.8 ± 1.6 GPa, respectively, were achieved at 10 vol.% inoculant in the L-PBF process. Strengthening mechanism calculations and the tensile data suggest a higher strengthening contribution via modulus mismatch and Orowan strengthening from the particles created by reaction synthesis than from Hall–Petch strengthening through grain refinement. [ABSTRACT FROM AUTHOR]

MACHINE learning, MACHINE parts, STANDARD deviations, TENSILE strength, RANDOM forest algorithms, and RAPID prototyping

Laser-based directed energy deposition (L-DED) is a rising field in the arena of metal additive manufacturing and has extensive applications in aerospace, medical, and rapid prototyping. The process parameters, such as laser power, scanning speed, and layer thickness, play an important role in controlling and affecting the properties of DED fabricated parts. Nevertheless, both experimental and simulation methods have shown constraints and limited ability to generate accurate and efficient computational predictions on the correlations between the process parameters and the final part quality. In this paper, two data-driven machine learning algorithms, Extreme Gradient Boosting (XGBoost) and Random Forest (RF), were applied to predict the tensile behaviors including yield strength, ultimate tensile strength, and elongation (%) of the stainless steel 316L parts by DED. The results suggest that both models successfully predicted the tensile properties of the fabricated parts. The performance of the proposed methods was evaluated and compared with the Ridge Regression by the root mean squared error (RMSE), relative error (RE), and coefficient of determination (R2). XGBoost outperformed both Ridge Regression and Random Forest in terms of prediction accuracy. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, SHAPE memory polymers, RAPID prototyping, DISRUPTIVE innovations, SELF-healing materials, MATERIALS science, and SPACE environment

3D printing is a constantly expanding technology that represents one of the most exciting and disruptive production possibilities available today. This technology has gained global recognition and garnered considerable attention in recent years. However, technological breakthroughs, particularly in the field of material science, continue to be the focus of research, particularly in terms of future advancements. The 3D printing techniques are employed for the manufacturing of advanced multifunctional polymer composites due to their mass customization, freedom of design, capability to print complex 3D structures, and rapid prototyping. The advantages of 3D printing with multipurpose materials enable solutions in challenging locations such as outer space and extreme weather conditions where human involvement is not possible. Each year, numerous research papers are published on the subject of imbuing composites with various capabilities such as magnetic, sensing, thermal, embedded circuitry, self-healing, and conductive qualities by the use of innovative materials and printing technologies. This review article discusses the various 3D printing techniques used in the manufacture of polymer composites, the various types of reinforced polymer composites (fibers, nanomaterials, and particles reinforcements), the characterization of 3D printed parts, and their applications in a various industries. Additionally, this review discussed the limitations of 3D printing processes, which may assist future researchers in increasing the utility of their works and overcoming the shortcomings of previous works. Additionally, this paper discusses processing difficulties, anisotropic behavior, stimuli-responsive characteristics (shape memory and self-healing materials), CAD constraints, layer-by-layer appearance, and void formation in printed composites. Eventually, the promise of maturing technology is discussed, along with recommendations for research activities that are desperately required to realize the immense potential of operational 3D printing. [ABSTRACT FROM AUTHOR]

DIGITAL image correlation, METAL fibers, RAPID prototyping, POISSON'S ratio, METAL powders, FINITE element method, and DIGITAL images

Recently, metals have been processed with fused filament fabrication (FFF) printers, in the form of mixture of metal powder and a polymeric binder. This new area of additive manufacturing is called metal-fused filament fabrication (metal FFF), and it is characterized by several advantages: low cost of manufacturing for small batches, ease of use, lower cost of energy and lower risks compared to the main metal additive manufacturing technologies. Being a novel technique, it is of great importance to understand the mechanical behaviour of the fabricated parts to reach the potential applications. In this work, the mechanical response of parts printed by metal FFF was analysed by means of digital image correlation (DIC) technique. This latter allowed to better highlight the anisotropic mechanical behaviour of the FFF parts when varying some 3D printing parameters, such as building orientation and number of wall layers and enabled a complete characterization of material useful for numerical calculation and finite element analysis. With this aim, 316L stainless steel filament and a consumer 3D printer were used for the fabrication of tensile test specimens. Three different building orientations and three different numbers of wall layers were evaluated. Results obtained from the tensile tests conducted with the DIC system highlighted the anisotropy of the strain behaviour when varying building orientation and printing strategy. More in details, flatwise and sideways configurations returned higher values of tensile strength, elongation at break and Poisson's ratio compared to upright one, while the increase of number of wall layers, in some cases, caused a decrease of the mechanical properties. [ABSTRACT FROM AUTHOR]

3-D printers, HALL effect transducers, DETECTORS, MACHINE learning, COMPUTER printers, and MAGNETS

Desktop fused filament fabrication (FFF) 3D printers have been growing in popularity among hobbyist and professional users as a prototyping and low-volume manufacturing tool. One issue these printers face is the inability to determine when a defect has occurred rendering the print unusable. Several techniques have been proposed to detect such defects, but many of these approaches are tailored to one specific fault, use expensive hardware, and/or use machine learning algorithms which can be sensitive to ambient conditions making them unreliable. This paper proposes a novel, low-cost system, named MTouch, to accurately detect millimeter-scale defects that tend to make prints unusable. MTouch uses an actuated contact probe designed with a low-power solenoid, magnet, and hall effect sensor. This sensor is used to check for the presence, or absence, of the printed object at specific locations. The MTouch probe demonstrated 100% accurate readings, which was significantly higher than the 74% achieved using a repurposed commercially available bed leveling touch probe (the BLTouch). Additionally, algorithms were developed to detect common print failures such as layer shifting, bed separation, and filament runout using the MTouch probe. In head-to-head testing against a commercially available print defect detection system (The Spaghetti Detective), the MTouch was able to detect faults 44% faster on average while only increasing the print time by 8.49%. In addition, MTouch was able to detect faults The Spaghetti Detective was unable to identify such as layer shifting and filament runout/jam. [ABSTRACT FROM AUTHOR]

DIGITAL twins, FUSED deposition modeling, 3-D printers, RAPID prototyping, VIRTUAL machine systems, and WEB-based user interfaces

Additive manufacturing is often used in rapid prototyping and manufacturing, allowing the creation of lighter, more complex designs that are difficult or too expensive to build using traditional manufacturing methods. This work considers the implementation of a novel digital twin ecosystem that can be used for testing, process monitoring, and remote management of an additive manufacturing–fused deposition modeling machine in a simulated virtual environment. The digital twin ecosystem is comprised of two approaches. One approach is data-driven by an open-source 3D printer web controller application that is used to capture its status and key parameters. The other approach is data-driven by externally mounted sensors to approximate the actual behavior of the 3D printer and achieve accurate synchronization between the physical and virtual 3D printers. We evaluate the sensor-data-driven approach against the web controller approach, which is considered to be the ground truth. We achieve near-real-time synchronization between the physical machine and its digital counterpart and have validated the digital twin in terms of position, temperature, and run duration. Our digital twin ecosystem is cost-efficient, reliable, replicable, and hence can be utilized to provide legacy equipment with digital twin capabilities, collect historical data, and generate analytics. [ABSTRACT FROM AUTHOR]

GLOBAL optimization, RAPID prototyping, ENGINEERING design, INJECTION molding, MANUFACTURING processes, GENETIC algorithms, and CHEMICAL molding

Injection molding (IM) is a versatile manufacturing process capable of rapid prototyping and mass-producing high-quality polymer parts. The present study mainly investigates the challenge of designing multiple molding gates on the complex arbitrary part surface in 3D. Currently, this problem is a challenge in mold design and engineering experience still plays an important role in designing the molding gates. To reduce the human intervention in the design process, the present study proposed a novel methodology with the following major steps: 1) using Poisson disk sampling (PDS) to preselect candidate gate locations automatically within the suitable gating region specified by designers; 2) using a space-filling initialization strategy and efficient global optimization to find the optimal gate locations. In the present setting, the molding gate design problem is formalized as a discrete optimization problem. The PDS is employed to construct the discrete solution space and EGO is used to efficiently search through a large solution space for the best design. To further promote optimization efficiency, a parallel implementation of EGO is also proposed. The effectiveness of the proposed methods is validated in two design cases. The results demonstrate the proposed EGO and Parallel EGO method is superior that the Genetic Algorithm (GA) and Surrogate Optimization (SO). Moreover, the proposed Parallel EGO converges faster than all other alternatives. [ABSTRACT FROM AUTHOR]

FOOT orthoses, FLEXIBLE manufacturing systems, RAPID prototyping, MACHINE learning, PSYCHOLOGICAL feedback, ELECTRONIC data processing, and TIME management

Mold design and construction is typically the most time-consuming and costly process in the fabrication of custom freeform product surfaces. Reconfigurable molds reduce this time and cost; however, some opportunities for improvement in reconfigurable systems are still possible in design by reducing system complexity and reconfigure time for a target application. A novel "multi-actuated optimized reconfigurable freeform surface (MORFS)" mold is proposed for the following key targets to (1) design the system for a targeted application, e.g., custom foot orthoses (CFOs), (2) reduce system complexity, (3) reduce system reconfigure time, and (4) ensure accuracy. The MORFS design process involves the following steps: (1) data processing, segmentation, normalization, and dimensionality reduction; (2) design of a novel mechanical subassembly; (3) development of a finite element (FE) flexible shell model of the manufacturing surface mold; (4) design optimization; and (5) development of a machine learning (ML)-based feedback control algorithm. The developed MORFS mold is 29% less complex, and 60% faster as compared with the benchmark study while maintaining the desired accuracy, i.e. mean error ≤ 1 mm. Furthermore, the accuracy of the optimized MORFS mold is also increased up to 39% as compared with the unoptimized configuration. The mechanical subassembly of the MORFS mold is improved by conducting design optimization, i.e., the number of actuators is reduced. Furthermore, the system reconfigure time is reduced significantly by using the FE model based ML control algorithm. The proposed design methodology ensured the desired accuracy of the surface construction for a target application. This case study is limited to the construction of freeform surfaces for CFOs; however, the proposed MORFS design methodology may be used to improve the time, complexity, and cost aspects of manufacturing in different areas including aerospace, automotive, biomechanics, and civil. [ABSTRACT FROM AUTHOR]

MARTENSITIC stainless steel, STEEL walls, MANUFACTURING processes, THERMAL properties, STAINLESS steel, METALS, and WIRE

Additive manufacturing is often seen as a novel alternative compared to well-consolidated, subtractive, and formative manufacturing processes. Its presence in the industrial environment is rapidly increasing, and its performance and flexibility may be the answer for present-day fabrication challenges, combining solutions to minimize environmental impacts without losing competitiveness or product quality. Arc welding-based additive manufacturing (also known as wire arc additive manufacturing, WAAM) has been gaining prominence in the current Industry 4.0 scenario. For the advancement of this technology, multiple output analysis of the pertinent welding processes is essential, especially regarding studies applied to materials such as high-strength and high-cost steels. In this paper, a study was conducted with the AISI 420 alloy and CMT variants of the GMAW process applied to additive manufacturing of thin walls, comparing them with conventional GMAW process. The welding processes and deposited welds used were analyzed on electrical, thermal, morphological, and metallurgical aspects. In the end, CMT Advanced and CMT Pulse variants stood out as opposite extremes, whereby CMT Advanced presented the best performance in relation to wall height and heat input. CMT and conventional GMAW produced good and significantly similar results, highlighting the stability of CMT. [ABSTRACT FROM AUTHOR]

SHEET metal, METALWORK, SHEET metal work, AEROSPACE industries, MICROELECTRONICS, and WATER jets

Nowadays the development of innovative processes is a major challenge for industries which want to prototype functional workpieces. Incremental sheet forming (ISF) is a good alternative for sheet metal prototyping to ensure flexibility, accuracy of the part produced, and cost effectiveness. A derived process, the Water Jet Incremental Sheet Forming (WJISF), has been undergoing development since 2001 and this paper purpose to give its state of the art. Different eclectic industrial fields could be concerned by WJISF process: automotive, micro-electronics, medical, and aerospace industry, for example. As the ISF process, the WJISF device needs a multi-axial machine, but it also needs a pressure pump with a sufficient flow rate and pressure. In an environmental point of view, this process can be seen as a "green" one giving that the water can be recycled and there is no lubricant. A general methodology has been defined to rigorously investigate this process and focus on researchers' teams, technological feasibility, numerical simulations, machine-tool uses, and real parts manufacturing. The study presented here provides summarizing evidence, especially technological windows, which give quick view of the actual knowledges and will help scientists and industrials to find WJISF parameters related to their needs. A lot of simple tests have been carried out with numerical and experimental comparisons. Nevertheless, few real parts have been manufactured, and the complex shape obtained by WJISF remains a scientific field to explore. [ABSTRACT FROM AUTHOR]

FUSED deposition modeling, MOLDING materials, FLEXURAL strength, INJECTION molding, GLASS fibers, FLEXURE, and CARBON fibers

Vacuum casting (VC) is a promising technique used for the production of functional plastic parts due to its fast production of high-quality prototypes. However, the mechanical properties of the fabricated products are affected by the composition of the molding materials. Additive manufacturing (AM) is also widely applied for low-volume prototyping applications. However, the mechanical properties of the fabricated products are affected by both build directions and printing angles. To investigate the difference in flexural strength of parts between vacuum casting and fused deposition modeling, glass fiber (GF) and carbon fiber (CF) are added to the matrix materials of polyurethane (PU) for improving the flexural strength of the molded products and three different printing angles and two build directions were applied in AM process. It was found that the flexure strength of the specimen fabricated by VC is generally greater than that of the specimen fabricated by AM. The highest flexure strength of the specimen fabricated by VC is 141 MPa, whereas the highest flexure strength of the specimen fabricated by FDM is only 102.7 MPa. The addition of short GF to the PU will increase the flexural strength. The flexural strength can be increased by about 41% when the PU is added with 4 wt.% short GF. The flexural strength can be increased by about 4.8% when the PU is added with 1 wt.% long GF. In contrast to above results, the flexural strength will be reduced when the PU is added with more than 2 wt.% long GF. On the contrary, the flexural strength can not be improved when the short CF or long CF is added to the PU. Finally, the flexural strength of the plastic prototype made by VC technology is superior to that of the plastic prototype made by FDM since the mechanical properties of the plastic prototype made by the FDM are affected by the build direction and printing angle. [ABSTRACT FROM AUTHOR]

POLYETHER ether ketone, COMPUTER simulation, POLYLACTIC acid, RAPID prototyping, TEMPERATURE, HEAT transfer, and FUSED deposition modeling

Material extrusion additive manufacturing is one of the widely used rapid prototyping technology, which produces parts with complex shapes and structures by continuous deposited strands. In previous studies, the influence of process parameters on product performance was experimentally studied, while morphological evolutions of strands, particularly considering the temperature variation, were not well understood. In this study, the mesostructure formed by parallel strands during continuous non-isothermal deposition flows was comprehensively studied by numerical simulations and experimental methods. The numerical model simulated the complete process of flow, deposition, bonding, and heat transfer for the representative materials, polyether ether ketone (PEEK), and polylactic acid (PLA). The quantitative comparison of the strands cross-sectional size measured by experiments and simulations was presented, and the results were consistent. The results showed that increasing the reheating temperature can considerably improve the strand-to-strand bonding. The effects of gap distance, printing speed, and strand-to-strand distance on the mesostructures of PEEK and PLA were comprehensively investigated and compared. Additionally, the simulation and experiment results provided detailed information regarding the porosity and bonding degree, which significantly affects product performance. [ABSTRACT FROM AUTHOR]

WRINKLE patterns, FINITE element method, STRENGTH of materials, and SHEET-steel

Roll forming is increasingly used in the automotive industry for the manufacture of structural and crash components from ultra-high-strength steel (UHSS). Springback and end flare are common shape defects in roll forming and increase with material strength. The conventional roll forming process is limited to the manufacture of components with a uniform cross section while flexible roll forming can produce parts with variation in width and depth. In this paper, the flexible roll forming of an automotive component from three different high-strength sheets of steel is investigated. The experiments are carried out with a flexible roll forming prototyping facility and combined with finite element analysis. The study shows that the flexible roll forming of high-strength automotive components is possible. Springback and end flare depend on the material strength and the forming sequence and can be reduced with a flexible forming approach where the material is first overbent followed by bending back. Wrinkling of the flange was observed but the severity of wrinkling reduced with an increasing number of forming passes. [ABSTRACT FROM AUTHOR]

BIOCERAMICS, 3-D printers, DENTURES, BIOMEDICAL materials, and THREE-dimensional printing

The introduction of ceramic materials in the medical field is becoming a vital necessity because of its stable physicochemical characteristics, high biocompatibility, and good osteoconductivity. On the contrary, machining ceramic components is difficult, owing to their extreme hardness and brittleness. Additive manufacturing (AM) technologies are an appropriate alternative to obtain the complex shapes of implants, which can have porous structures. Thus, since the development of 3D printing, direct ink writing (DIW) is one of the most promising and inexpensive techniques for shaping free-form ceramic medical components such as prostheses or dental implants from liquids or pastes. However, the assurance of performance criteria of the extrusion system for simultaneous usage becomes the major challenge for most direct ink writing (DIW) platforms, for instance for printing large parts, for multi-material printing, to decrease printing time, and to increase efficiency in terms of motor usage and weight of the extruders. To address the current deficiencies, a new extrusion system is designed for a 3D printing machine for ceramics that is compatible with different low-cost, open-source 3D printers. The proposed extrusion model enables printing with a loader with different syringes simultaneously, without stopping the operational process while switching the syringe. It adopts three subsystems. The automatic syringe loading system, which is operational to manually receive several syringes of the same or different volumes, allows the syringe feeding system to be loaded and unloaded once the syringe is empty. The syringes are automatically transferred to the holding system using an arm. The holding system allows the fixing of the syringe in order to perform printing with ceramic material. Pugh concept analysis was used to select the optimum design shape. After that, the 3D CAD environment was used to combine the strength of Pugh's method and the design space. This brings a new concept into the mechanical design field for 3D printers, which is in line with the technological trends prevalent in the industry. [ABSTRACT FROM AUTHOR]

MARAGING steel, MECHANICAL heat treatment, RIETVELD refinement, CARBON steel, HEAT treatment, and FACTORIAL experiment designs

Maraging steels (MS) are widely used materials for heavy-duty applications and are considered an alternative to carbon hardened steels when high strength and good toughness is needed. Their processing through additive manufacturing (AM) technologies offers additional high-value opportunities, for instance, in the rapid prototyping or fabrication of tooling and inserts, and in the repair of molds and dies as well as in maintenance applications. This work studied the maraging 300 steel (18Ni-300) deposited by the laser cladding (LC) process. The experimental design was based on a 23-full factorial design used to determine the optimum processing windows, using a constant powder feed rate. After that, samples with optimal process parameters were manufactured to determine the influence of deposition strategy and aging heat treatments on structural and mechanical properties (i.e., macrohardness). Results indicated the influence of crucial process parameters (i.e., laser power, velocity, and laser spot size) on the track's geometrical characteristics. The processing windows also revealed that particular combinations of these parameters' values produced LC tracks with the minimum dilution with either maximum height or maximum width, which is desirable for manufacturing and repair applications. Although the as-built samples did not show significant differences in their hardness, they showed a considerable difference in their austenitic phase content due to a combined effect between the sample's geometry and deposition pattern. Aging heat treatments between 460 and 490 °C (4–8 h) resulted in the maximum hardness value (~55HCR) with an austenite content below 6 wt% calculated by Rietveld analysis. Finally, SEM and EDS analysis were carried out; it was found that the austenite located in the boundaries of the solidification structures is rich in Mo, Ti, and Ni for the samples in the as-built condition, while for the samples with aging, the highest content of austenite rich in Ni and Mo was obtained with aging at 530 °C. [ABSTRACT FROM AUTHOR]

METALLIC wire, GAS metal arc welding, WIRE, RAPID prototyping, and ULTRAMICROELECTRODES

Wire arc additive manufacturing (WAAM) is well suited for the manufacture of sizeable metallic workpieces featuring medium-to-high geometrical complexity due to its high deposition rate, low processing conditions limit, and environmental friendliness. To enhance the current capability of the WAAM process for fabricating structures with complex geometry, this paper proposes a robot-based WAAM strategy adapted specifically for fabricating freeform parts with wire structures composed of multiple struts. Contributions in this work include: (i) The study of bead modelling, which establishes optimal welding parameter selection for the process; (ii) the novel manufacturing strategy, including the adaptive slicing methodology and height control system for accurately depositing every single strut; and (iii) detailed manufacturing procedures for multi-strut branch intersections as well as the collision-free path planning to control the overall fabrication process. To verify the effectiveness of this proposed WAAM approach, two complex wire structures were fabricated successfully, indicating the feasibility of the proposed fabrication strategy. [ABSTRACT FROM AUTHOR]

FUSED deposition modeling, RAPID prototyping, EXTRUSION process, RAPID tooling, MANUFACTURING processes, and FINITE element method

Additive manufacturing has evolved from a rapid prototyping tool to a set of manufacturing processes for functional parts. One of their most outstanding features is the ability to build complex geometry parts. However, their industrial application is limited because these parts exhibit heterogeneous and porous micro/mesostructures with anisotropic behavior. These structural characteristics, mainly porosity, are strongly related to the building parameters. In this work, a computational multiscale homogenization approach was implemented to determine the mechanical properties of unidirectional and criss-cross mesostructures generated by a material extrusion process (MEP). Representative volume elements (RVE) for simplified and real-like pore geometries were created to model the mesostructures and to perform the multiscale analysis. Stiffness tensor for each RVE was obtained and graphically represented to observe the mechanical properties as a function of the orientation. A great influence of the pore geometry on mechanical properties was observed. Finally, by comparing with experimental data, the results obtained were validated. [ABSTRACT FROM AUTHOR]

DRAWING (Metalwork), SHEET metal, MASS production, METALWORK, RAPID prototyping, and SHEET metal work

Due to the change from mass production to mass personalized production and the resulting intrinsic product flexibility, the automotive industry, among others, is looking for cost-efficient and resource-saving production methods to combining global just-in-time production. In addition to geometric manufacturing flexibility, additive manufacturing offers a resource-saving application for rapid prototyping and small series in predevelopment. In this study, the FDM process is utilized to manufacture the tooling to draw a small series of sheet metal parts in combination with the rubber pad forming process. Therefore, a variety of common AM polymer materials (PETG, PLA, and ABS) is compared in compression tests, from which PLA is selected to be applied as sheet metal forming die. For the rubber pad forming process, relevant processing parameters, i.e., press force and rubber cushion hardness, are studied with respect to forming depth. The product batch is examined by optical evaluation using a metrological system. The scans of the tool and sheet metal parts confirm the mechanical integrity of the additively manufactured die from polymer and thus the suitability of this approach for small series in sheet metal drawing processes, e.g., for automotive applications. [ABSTRACT FROM AUTHOR]

FUNCTIONALLY gradient materials, FINITE element method, MATHEMATICAL optimization, FOAM, PHENOMENOLOGICAL biology, and STRUCTURAL optimization

Weight reduction is one of the main concerns when designing any component as it reduces material cost and green house gas emissions, among other aspects. Several numerical approaches exist in the literature with the objective of having any component with known mechanical loading become optimized in terms of mass minimization and stiffness maximization. Thus, the objective of this work is the development of optimized structures maintaining the same geometry by means of cellular materials, namely the gyroid infill, and generating functionally graded cellular structures with higher stiffness-to-weight ratio. Remodelling algorithms based on biological phenomena, namely bone growth, as well as Bi-evolutionary structural optimization (BESO) were employed to obtain the density map allowing the material functional gradient distribution. Smoothing functions were tested as a possibility of enhancing stiffness as abrupt density changes are avoided. The gyroid infill was characterized in order to create a phenomenological law based on bone remodelling laws. The gyroid law was implemented on the analysis FEMAS (opens-source, academic and educational FEM and meshless method software) software which presented the density map as an output. Each gradient consisted on areas at a similar density being concatenated into one solid. The different solids, at different density levels, are assembled thus creating the material functional gradient. Lastly, simulations consisted on three distinct and benchmark flexural load cases. Specimens were printed using FFF technology in PLA (E = 3145 MPa, ν = 0.3) having then been tested experimentally according to the appropriate load case. Numerical results correlated with the experimental results in terms of accuracy between theoretical and experimental stiffness where there was a greater accuracy for the specimens subject to a Four-Point bending load case, where only a 16% gap was verified between numerical and experimental flexural stiffness. [ABSTRACT FROM AUTHOR]

INDUSTRY 4.0, CONCURRENT engineering, MANUFACTURING processes, FACTORIES, VIRTUAL prototypes, SHARED workspaces, and OFFSHORE wind power plants

Smart manufacturing, tailored by the 4th industrial revolution and forces like innovation, competition, and changing demands, lies behind the concurrent evolution (also known as co-evolution) of products, processes and production systems. Manufacturing companies need to adapt to ever-changing environments by simultaneously reforming and regenerating their product, process, and system models as well as goals and strategies to stay competitive. However, the ever-increasing complexity and ever-shortening lifecycles of product, process and system domains challenge manufacturing organization's conventional approaches to analysing and formalizing models and processes as well as management, maintenance and simulation of product and system life cycles. The digital twin-based virtual factory (VF) concept, as an integrated simulation model of a factory including its subsystems, is promising for supporting manufacturing organizations in adapting to dynamic and complex environments. In this paper, we present the demonstration and evaluation of previously introduced digital twin-based VF concept to support modelling, simulation and evaluation of complex manufacturing systems while employing multi-user collaborative virtual reality (VR) learning/training scenarios. The concept is demonstrated and evaluated using two different wind turbine manufacturing cases, including a wind blade manufacturing plant and a nacelle assembly line. Thirteen industry experts who have diverse backgrounds and expertise were interviewed after their participation in a demonstration. We present the experts' discussions and arguments to evaluate the DT-based VF concept based on four dimensions, namely, dynamic, open, cognitive, and holistic systems. The semi-structured conversational interview results show that the DT-based VF stands out by having the potential to support concurrent engineering by virtual collaboration. Moreover, DT-based VF is promising for decreasing physical builds and saving time by virtual prototyping (VP). [ABSTRACT FROM AUTHOR]

RAPID prototyping, RAPID tooling, TOOL-steel, and MECHANICAL properties of condensed matter

Hybrid moulds are an increasingly considered alternative for prototype series or short production runs. This type of tools resorts on the use of Rapid Prototyping and Tooling (RPT) to produce the moulding elements (blocks or other inserts). This study was developed using a hybrid injection mould with exchangeable moulding elements that were produced by additive manufacturing (AM), namely vacuum epoxy casting, stereolithography and ProMetal. A full steel tool was also used as a reference. The processing conditions for the polypropylene moulded parts using the hybrid mould were monitored for pressure, temperature and ejection force. The hybrid mould performance was assessed in terms of pressure and temperature evolution during the injection cycle and the AM moulding elements for physical integrity. The data from the polypropylene moulded parts and the moulding inserts are compared with structural and rheological simulations using ANSYS Workbench and MOLDEX 3D. The results show that the hybrid mould performance and the structural integrity of the moulding elements depend on the properties of the materials used. The moulding shrinkage, when resin cores are used, is also affected by the core deformation caused by the injection pressure. [ABSTRACT FROM AUTHOR]

RAPID prototyping, JEWELRY industry, PARAMETRIC modeling, 3-D printers, CASE studies, and STEREOLITHOGRAPHY

The new research and technologies that have ensured the digitalization of industries and the introduction of smart manufacturing are still characterized by poorly studied processes. In particular, communication and integration between different platforms, which form the ecosystem of smart manufacturing, are subject to various communication problems. The research conducted and propounded in this article is based on the implementation of an integrated manufacturing system that involves parametric modeling, optimization, and additive manufacturing. The ecosystem analyzed guarantees communication between IT platforms such as Rhino-Grasshopper, for parametric modeling, and PreForm, slicing software for Formlab's stereolithographic 3D printers. For this purpose, C# scripts have been implemented in order to solve optimization problems in 3D modeling of objects and to guarantee integration between the two platforms. The latter script is configured as a real add-in for Rhino whose advantages are easily demonstrated thanks to the large number of recursive operations that are automated. [ABSTRACT FROM AUTHOR]

INTERSECTION numbers, ALGORITHMS, TOPOLOGY, TRIANGLES, COMPUTATIONAL geometry, and INTERSECTION graph theory

To date, slicing algorithms for additive manufacturing is the most effective for favourable triangular mesh topologies; worst-case models, where a large percentage of triangles intersect each slice plane, take significantly longer to slice than a like-for-like file. In larger files, this results in a significant slicing duration, when models are both worst cases and contain more than 100,000 triangles. The research presented here introduces a slicing algorithm which can slice worst-case large models effectively. A new algorithm is implemented utilising an efficient contour construction method, with further adaptations, which make the algorithm suitable for all model topologies. Edge matching, which is an advanced sorting method, decreases the number of sorts per edge from n total number of intersections to two, alongside additional micro-optimisations that deliver the enhanced efficient contour construction algorithm. The algorithm was able to slice a worst-case model of 2.5 million triangles in the 1025s. Maximum improvement was measured as 9400% over the standard efficient contour construction method. Improvements were also observed in all parts in excess of 1000 triangles. The slicing algorithm presented offers novel methods that address the failings of other algorithms described in literature to slice worst-case models effectively. [ABSTRACT FROM AUTHOR]

3-D printers, POLYLACTIC acid, DIGITAL image correlation, MODULUS of rigidity, MANUFACTURING processes, and YOUNG'S modulus

3D printing by fused filament fabrication (FFF) provides an innovative manufacturing method for complex geometry components. Since FFF is a layered manufacturing process, effects of process parameters are of concern when plastic materials such as polylactic acid (PLA), polystyrene and nylon are used. This study explores how the process parameters, e.g. build orientation and infill pattern/density, affect the mechanical response of PLA samples produced using FFF. Digital image correlation (DIC) was employed to get full-field surface-strain measurements. The results show the influence of build orientation and infill density is significant. For on-edge orientation, the tensile strength and Young's modulus were 55 MPa and 3.5 GPa respectively, which were about 91% and 40% less for the upright orientation, demonstrating a significant anisotropy. The tensile strength and Young's modulus increased with increasing infill density. In contrast, different infill patterns have no significant effect. Considering the influence of build orientation, based on the experimental results, a constitutive model derived from the laminate plate theory was employed. The material parameters were determined by tensile tests. Results demonstrated a reasonable agreement between the experimental data and the predictive model. Similar anisotropy to tension was observed in shear tests; shear modulus and shear strength for 45° flat orientation were about 1.55 GPa and 36 MPa, whereas for upright specimens they were about 0.95 GPa and 18 MPa, respectively. The findings provide a framework for systematic mechanical characterisation of 3D-printed polymers and potential ways of choosing process parameters to maximise performance for a given design. [ABSTRACT FROM AUTHOR]

ROBOTICS, TACTILE sensors, OPTICAL fiber detectors, FIBER Bragg gratings, MANUFACTURING processes, OPTICAL gratings, and ARTIFICIAL skin

Modern industrial processes aim for the continuous production of small volumes tailored to the customer's needs. Machines and robotic platforms have to be more and more adaptable, flexible, and able to cope with complex scenarios where sensing and manipulation capabilities are the key technology to succeed. The literature has plenty of capacitive, resistive, piezoelectric, and piezoresistive sensors used as tactile or force sensors. All of them present some drawbacks like non-linear behavior, sensitivity to temperature or electromagnetic noise, and hysteresis, among others. Other sensing systems are bulky and hard to integrate, sometimes jeopardizing the dexterity and manipulability of the gripper. In this context, the manuscript proposes fiber Bragg grating (FBG) optical fiber as a tactile sensing element to capture the interaction forces during material handling and object manipulation since it has numerous advantages compared with the other sensing devices. The work also offers a methodology to easily integrate the fiber in industrial grippers and introduces a set of tests useful to characterize the sensors. Custom gripper fingers have been realized in rapid prototyping to present a pictorial example of such an integration. Finally, the essay presents some experiments that assess the capability of a tactile sensor based on FBG optical fiber showing as it can correctly perceive the contact forces (NRMSE = 0.75%) and can recognize the material of the object that is being manipulated. The authors believe that the application of optical fiber sensor as tactile feedback can be useful in industrial scenarios to enable complex manipulation activities. [ABSTRACT FROM AUTHOR]

CLOSED loop systems, RAPID prototyping, and MANUFACTURING processes

Additive manufacturing encompasses a set of low-cost and highly versatile tools used to prototype and fabricate three-dimensional (3D) objects with ease. In most of the additive manufacturing techniques, materials are deposited layer by layer until a 3D object is reproduced. Several additive manufacturing techniques have been developed in the previous decade, and the application of additive manufacturing has increased in various industrial sectors. However, there are still drawbacks associated with additive manufacturing techniques, necessitating further study and development. In this study, we review the techniques and materials used in additive manufacturing. The vast majority of additive manufacturing processes are still based on open-loop control or implement some local controllers for specific variables (such as temperature), making them susceptible for errors. This study presents a review of the different additive manufacturing techniques, examples of academic and commercial efforts to improve the control systems for additive manufacturing, as well as the application of additive manufacturing in different fields such as aerospace, electronics, arts, and biomedical. The article ends highlighting the advantages of utilizing a closed-loop control system in additive manufacturing and discussing the work needed for further development. [ABSTRACT FROM AUTHOR]

RAPID prototyping, INVESTMENT casting, ELECTRIC metal-cutting, MANUFACTURING processes, ELECTRODES, FEASIBILITY studies, MACHINING, and FABRICATION (Manufacturing)

This study fabricates a roughing electrode of electrical discharge machining (EDM) using a rapid prototyping (RP) system and investment casting technology, which reduces the overall time that is required for fabrication and the cost of the manufacturing process for a selected electrode. Pro/E (3D CAD) software is used to design the electrode prototype, which has a complex appearance, and to transform the CAD model into stereolithography (STL) format. An RP machine (Zcorp 402 3DP) is used to construct a gypsum-based powder model. After a sealing process using the permeation of resin, the water resistance and strength of the gypsum-based material are increased. The manufacturing process then involves creating a wax model with a gypsum electrode that is strengthened by resin permeation by casting a vulcanized silicone molding. The brass electrode is fabricated using investment casting technology. The results of an EDM test show that the brass electrodes with RP that are manufactured perform well and the total time that is required to machine the EDM electrode using RP is 15.8% less than the time that is required for a CNC machining process. [ABSTRACT FROM AUTHOR]

SHOE design, EXPERIMENTAL design, HEEL (Anatomy), NEW product development, REVERSE engineering, MANUFACTURING processes, NANOFABRICATION, and FOOT orthoses

Digital techniques are a strategic tool to design new commercial products, reducing time and waste. This is particularly relevant for shoe manufacturing and, in particular, for high-heeled shoes, for which a trade-off between comfort and attractiveness is difficult to achieve. This paper offers a new set of tools to design high-heeled shoes that exploits the synergies between modeling and experiments, aiming at predicting the comfort of such products, improving the manufacturing process by optimizing the design step. As a case study, two actual commercial 11-cm-heel shoe models, differentiated by the openness of the front side, were used to deploy the digital design procedure. A finite-element model was implemented by combining the outcomes from reverse engineering techniques, to reconstruct the foot and shoe topologies, and the experimental characterization of the materials used for the final shoe products. Pressure maps on the toes and the footbed were used as benchmarks for a comparison with experiments, made with commercial sensorized insoles. Non-uniform pressures for both shoe models were observed, with highest values for the closed-shaped specimen that presented peaks of ≈ 160 kPa on the footbed and ≈ 140 kPa on the external toes. The here presented digital approach has the potential to improve the design process that will not require the traditional fabrication of countless handicraft prototypes, saving time and the associated prototyping costs. Finally, although this work focused on a niche of the shoe market, this approach may be extended to other products, which customization has a key role in the manufacturing process. [ABSTRACT FROM AUTHOR]

FOCUSED ion beams, OPTICAL glass, MATERIALS science, RAPID prototyping, SEMICONDUCTOR materials, and OPTICAL fibers

Focused ion beam (FIB) milling is widely used in fields such as the semiconductor industry and materials science research. The direct writing and small feature size also make FIB milling attractive for rapid prototyping of novel photonic structures. In this manuscript, we describe in detail a FIB milling procedure which enables high-resolution fabrication of complex micro- and nanostructures with precise geometry control. Two different procedures (for 2D and 3D structures) are described and implemented on the tip of a glass optical fiber for fabricating diverse structures embedded on or below the tip surface. The procedures described here can be easily adjusted and implemented on any conductive or non-conductive substrate. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, LASER beams, LASERS, POWDERS, and BULK solids

Laser powder–based directed energy deposition (DED) is a specific additive manufacturing process that offers an effective way to fabricate parts via simultaneous delivery of powders and laser beam. It has been developing greatly in the recent decades and being widely used for manufacturing, prototyping, and repairing. Complex physical events take place during the manufacturing process and have great impacts on its overall performance. To build high-quality parts through the laser powder–based DED process, its physical insights and process parameters need to be understood and optimized, for which modeling provides an efficient way. This article gives a review of the modeling work for the laser powder–based DED process, in which the models developed for powder stream and its interaction with laser beam, melt-pool, and bulk heating are discussed in detail. Different modeling approaches and methods towards overall and specific physical processes of the laser powder–based DED are analyzed and compared. Suggestions towards the modeling are also given at the end. [ABSTRACT FROM AUTHOR]

MACHINING, MANUFACTURED products, COST control, CONSTRUCTION materials, PRODUCT costing, and ELECTROCHEMICAL cutting

In this competitive world, industries are looking for smart technologies to compete; these technologies help R&D people to explicit the ideas and bring the product to the market at shorter lead times and with affordable cost. Each AM machine has its own unique capabilities in manufacturing a product, utilising materials, material intake and wastages. Machine and material costs are the significant parameters, which play a major role in cost estimation of the prototypes. Costs of both machine and materials are prime factors in AM and it can be helpful for cost reduction due to their uniqueness. However, an alternate strategy is being concentrated on process optimization and consumption of material to reduce the overall cost of the prototype. In this paper, multi criterion decision making (MCDM) technique, namely, best-worst method (BWM), was adopted to select the suitable material for the product. This is along with the end user expectations in AM. In the initial phase, the suitable machine to be selected from the available machines is based on the parameters like cost, accuracy, variety of materials and material wastage. From the variety of materials, the suitable material was selected based on the respondent requirement. The criteria that influenced more in the overall cost of the product manufacture through AM is identified and used. According to BWM, the criteria to be selected by the decision maker based on the respondent expectations are identified. In BWM method, pairwise comparisons are carried out between the best and worst criterion suggested by the decision makers, as that it leads to the selection of the suitable material. Here, a demonstration of such a selection is detailed; this is certainly based on the respondent requirements. The result attained through the proposed methodology can be varied based upon the respondent requirements and further machine availabilities. In conclusion, the end result helps to identify the suitable machine and build materials for the prototype to be produced based on the respondent requirements. [ABSTRACT FROM AUTHOR]

ELECTRIC metal-cutting, LASER sintering, SELECTIVE laser sintering, METALLIC composites, OPEN-circuit voltage, COPPER electrodes, WORKPIECES, and X-ray spectrometers

Nowadays, additive manufacturing (AM)-based rapid prototyping (RP) is used as a convenient route for making tool electrodes required in electrical discharge machining (EDM). AM enables direct fabrication of complex shaped EDM electrode in comparatively less time in contrast to subtractive machining processes. In this study, an EDM electrode is prepared directly by selective laser sintering (SLS) process using metal matrix composite of aluminium (Al), silicon (Si) and magnesium (Mg). To study the performance of the prepared RP tool electrode in electrical discharge machining, titanium is used as workpiece material and EDM-30 oil as dielectric medium during machining. The performance of the prepared tool electrode is compared with conventional copper and graphite tool electrodes. Experiments have been conducted changing EDM process parameters viz. open circuit voltage (V), peak current (Ip), duty cycle (τ) and pulse duration (Ton) along with three tool electrodes such as RP, graphite and copper tool electrodes. The performance measures considered during the experimental study are material removal rate (MRR), tool wear rate (TWR), average surface roughness (Ra), white layer thickness (WLT), surface crack density (SCD) and micro-hardness (MH) on white layer. SEM and EDX of the machined surface reveal that tool material is generally eroded and deposited on the machined surface with formation of metal carbides. However, tool erosion is more pronounced in case of RP tool electrode. XRD analysis reveals the formation of titanium carbides on the machined surface resulting in increase in the micro-hardness of white layer. Discharge current and tool type are found to be significant parameters influencing the performance measures considered in the study. The surface produced when machined with RP tool electrode exhibits superior surface characteristics while graphite tool electrode produces better MRR and TWR. [ABSTRACT FROM AUTHOR]

RAPID prototyping, MANUFACTURING processes, FUSED deposition modeling, RESIDUAL stresses, and BOX-Jenkins forecasting

This paper proposes a novel data-driven approach for predicting and optimizing the additive manufacturing process parameters. The integrated scheme consists of three popular algorithms: (1) group method for data handling (GMDH) as the engine of neural networks, (2) autoregressive integrated moving average (ARIMA) for characterizing spatial collinearity of the multiple response, and (3) indirect optimization on the basis of self-organization (IOSO) to adopt the emerged correlated multi-response optimization problem. As a numerical case study, a computer-generated fused deposition modeling data tested the introduced algorithms. The finite element (FE) simulation model consists the multi-layer residual stresses as targets, in respect of printing speeds as process parameters. The residual stresses predicted by the low-order integrated ARIMA-GMDH variants correlate well with the FE simulations. This approach provides a viable data-driven alternative for computationally based rapid prototyping and additive manufacturing processes. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, RAPID prototyping, PRINTING, and BEHAVIOR

Although 3D printing was invented in 1984, it was not until recent years that it captured the imagination of everyone from industry experts to at-home hobbyists. Three-dimensional printing, also known as additive manufacturing or rapid prototyping, constructs an object by accumulating materials layer by layer. In recent years, 3D printing technology has been dramatically developed with respect to materials, printer, and process, which laid a foundation for 4D printing. Four-dimensional printing is the targeted evolution of the 3D-printed structure, concerning shape, property, and functionality. The object is produced by 3D printing firstly. Then, the object can self-deform, self-assemble, self-disassemble, self-repair, and change property or functionality over time when the external stimuli are imposed on it. This review mainly introduces the stimulus, types of shape-shifting behaviors, mechanisms of deformation, and applications of 4D printing. [ABSTRACT FROM AUTHOR]

SHAPE memory alloys, SHAPE memory effect, PREDICTION models, ARTIFICIAL neural networks, and LASERS

Shape memory alloys (SMAs) have been applied for various applications in the fields of aerospace, automotive, and medical. Nickel-titanium (NiTi) is the most well-known alloy among the others due to its outstanding functional characteristics including superelasticity (SE) and shape memory effect (SME). These particular properties are the result of the reversible martensite-to-austenite and austenite-to-martensite transformations. In recent years, additive manufacturing (AM) has provided a great opportunity for fabricating NiTi products with complex shapes. Many researchers have been investigating the AM process to set the optimal operational parameters, which can significantly affect the properties of the end-products. Indeed, the functional and mechanical behavior of printed NiTi parts can be tailored by controlling laser power, laser scan speed, and hatch spacing having them a crucial role in properties of 3D-printed parts. In particular, the effect of the input parameters can significantly alter the mechanical properties such as strain recovery rates and the transformation temperatures; therefore, using suitable parameter combination is of paramount importance. In this framework, the present study develops a prediction model based on artificial neural network (ANN) to generate a nonlinear map between inputs and outputs of the AM process. Accordingly, a prototyping tool for the AM process, also useful for dealing with the settings of the optimal operational parameters, will be built, tested, and validated. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, THREE-dimensional display systems, LITHOGRAPHY, INDUSTRIAL marketing, SURFACE finishing, AIRCRAFT industry, and AEROACOUSTICS

Stereolithography (SLA)-based three-dimensional (3D) printing is widely used in both industrial and consumer markets for prototyping and concept validation. It also plays an important role in aircraft industry as it offers advantages in surface finish and high precision. Despite the extensive usage, the combination of large volume, high resolution, and high speed is hard to achieve. This paper presents a 3D printing technology that allows a UV projector to continuously cure resin while scanning over the build area. To print large objects, 3D models are sliced into layer-by-layer, high-resolution image "maps". Each "map" is further divided into sub-region images that are dynamically exposed to the photocurable materials and synchronized with the scanning of the projector, causing a still exposure pattern to appear on the build area. Therefore, large objects with delicate details can be printed layer-by-layer. As such, customized build volumes on a large scale (greater than 1 m3) can be achieved with micro-scale features. Along with a wiping system, this technique is compatible with various materials, leading to the direct manufacturing of final parts from photocurable materials. Furthermore, this technique shows advantages over existing large-scale DLP printing methods regarding both printing speed and material flexural properties. This technique can be implemented at design workflow in the aerospacing industry by facilitating design communication, validation, pre-production, and even assisting in producing final parts. [ABSTRACT FROM AUTHOR]

VIRTUAL reality, COMPUTER-aided design, SOFTWARE development tools, COLLISIONS (Physics), FEATURE extraction, and INDUSTRY 4.0

Assembly validation is a key part of product design. Current methods, such as physical prototyping are time-consuming and do not offer immediate validation results. Assembly motion simulation systems have been proposed as a solution to this problem. However, widespread adoption of such systems is hindered due to their ties to proprietary computer aided design (CAD) software or expensive and often cumbersome hardware. Recently, virtual/augmented reality (VR/AR) technologies and simulation have been heralded as two of the key enabling factors of Industry 4.0. Collective interests in these technologies by industry and community have brought many low-cost software and hardware tools to the market, which opens a gateway to achieving assembly validation at a much lower cost. This paper presents an assembly validation system that is independent of CAD packages, interoperable and implemented using relatively low-cost and commercially available hardware and software tools. The system features intuitive bare-hand manipulation of part models through a virtual hand model that tracks the hands. Collision detection and physics modelling allow for hand-part and part-part interactions to be natural, thus validating assembly interactions. An assembly feature extraction algorithm has also been implemented to analyse the planar face features of the part models to detect possible mating assembly features between parts concerned. A constraint management system considers identified mating features and determines the allowable motion of parts once constraints are applied and removed. Pulling force is used to facilitate the removal of constraints. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, LABOR costs, INDUSTRY 4.0, VIRTUAL reality, COST accounting, VIRTUAL reality software, and MIXED reality

Digital manufacturing concept is gaining a lot of attention and popularity due to its enormous benefits. It is considered as one of the pillars or component of Industry 4.0. With the advancements in technology, digital manufacturing is becoming a reality rather than a concept only. It is applied to various stages of the manufacturing process such as design, prototyping, and assembly training. Virtual reality (VR) is a cog in a wheel of digital manufacturing. It can be used in various phases of manufacturing. Planning and conducting assembly operations account for the majority of the cost of a product. It is difficult to design and train assembly operations during the early stages of product design. Assembly is a vital step in manufacturing, so firms provide training to their employees and it costs them time and money. Therefore, this research work extends VR applications in manufacturing by integrating concepts and studies from training simulations to the evaluation of assembly training effectiveness and transfer of training. VR provides a platform for "learning by doing" instead of learning by seeing, listening, or observing. A series of user-based evaluation studies are conducted to ensure that the virtual manufacturing assembly simulation provides an effective and efficient means for evaluating assembly operations and for training assembly personnel. Different feedback cues of VR are implemented to evaluate the system. Moreover, several case studies are used to assess the effectiveness of VR-based training. The results of the study reveal that participants trained by VR committed fewer errors and took lesser time in actual product assembly when compared against the participant from traditional or baseline training group. [ABSTRACT FROM AUTHOR]

INDUSTRIAL robots, MANUFACTURING processes, REINFORCEMENT learning, MULTISENSOR data fusion, RAPID prototyping, INDUSTRY 4.0, and ROBOTS

In recent years, the applications of industrial robots are expanding rapidly due to Industry 4.0 oriented evolutions, ranging from automobile industry to almost all manufacturing domains. As demands with rapid product iterations become increasingly fluctuant and customized, the assembly process of industrial robots faces new challenges including dynamic reorganization and reconfiguration, ubiquitous sensing, and communication with time constraints, etc. This paper studies the industrial robot assembly process modeling, planning, and scheduling based on real-time data acquisition and fusion under the framework of advanced shop-floor communication and computing technologies such as wireless sensor, actuator network, and edge computing. Taking the assembly of industrial robots as the specific object, the multi-agent model of industrial robot assemble process is established. Then, the encapsulation, communication, and interaction of agents with real-time data acquisition and fusion are studied. Based on multi-agent reinforcement learning approach, an intelligent planning and scheduling algorithm for industrial robot assembly is proposed, and a simulation case is presented to demonstrate the proposed model and algorithm. [ABSTRACT FROM AUTHOR]

ELASTOMERS, THERMOPLASTICS, THERMOPLASTIC composites, POLYETHYLENE terephthalate, FRACTOGRAPHY, ULTIMATE strength, and POLYMERS

Due to the layer-by-layer nature of additive manufacturing, fabricated parts suffer from an anisotropic behavior with reduced mechanical performance when compared to traditional manufacturing. One specific mechanical property, folding endurance, requires both low flexural strength and simultaneously high elongation to achieve the flexibility needed to sustain repetitive bending. The present work provides an analysis of selected thermoplastics' flexural capacity, including nylon (PA), polyethylene terephthalate (PETG), polylactide (PLA), thermoplastic polyurethane (TPU), polypropylene (PP), polyethylene (PE), and a TPR blend (ABSMG94: SEBS-g-MA 25:75), in order to evaluate the maximum number of folding cycles and load capacity sustained by a living hinge. A fractographic analysis was performed using scanning electron microscopy and computed tomography. Similar to the performance of injected molded products, the experimental results demonstrated that three of the tested materials behaved well in the context of a large number of folding cycles prior to an eventual detachment into two pieces; TPR blend, 244,424 cycles; PP endured one million cycles; and TPU, more than two million cycles, while the remaining materials failed to survive more than 1000 cycles. The hinges failure analysis revealed a wide variety of fracture morphologies and failure modes. In regard to the load capacity, PLA, PETG, and nylon provided the highest results in the ultimate strength of an axial static force applied (790.61 N, 656.06 N, and 652.75 N respectively), while the TPR blend was the highest (398.44 N) of the elastomeric materials (PP, TPU, and TPR blend). The evaluated materials demonstrated enough flexibility for use in specific applications such as stretchable electronics and wearable applications. [ABSTRACT FROM AUTHOR]

FOIL stamping, BORON steel, SCANNING electron microscopes, LOW temperatures, HARDNESS testing, and TENSILE tests

This paper demonstrates the promise of a new low-temperature hot stamping process with pre-cooling for 22MnB5 boron steels. It is the first time for the new process being successfully implemented for producing an automotive demonstrator component assisted with thorough experimental studies. The studies mainly include hot forming experiments carried out on an industrial prototyping line, post-form examinations, and in-die quenching tests. Automotive B-Pillar components with two designed drawing depths (50 and 64 mm) were hot stamped at a wide range of temperatures and forming speeds, through both the conventional hot stamping processes and the new processes with pre-cooling applied. For the as-formed B-Pillars, 3D shape scanning was conducted to investigate the thickness distribution of the components; uniaxial tensile testing, hardness testing, and scanning electron microscopes (SEM) observation were conducted to assess the final mechanical properties and microstructures. To understand the benefit of the low-temperature hot stamping in reducing cycle time, a separate set of in-die quenching experiments were designed and carried out, with combinations of three different process parameters: workpiece start quenching temperature, initial tool temperature, and die-workpiece contact pressure. The results of this work confirmed that low-temperature hot stamping could be performed successfully in producing complex-shaped components, such as automotive B-Pillars, with much reduced cycle time. [ABSTRACT FROM AUTHOR]

AUGMENTED reality, INDUSTRY 4.0, OPTICAL head-mounted displays, GAS industry, and MANUFACTURING processes

Augmented Reality (AR) is one of the nine key technologies of Industry 4.0 and one of the most promising innovation accelerators that in the next years will bring smart factories to a higher level of efficiency. In this context, the paper presents an AR tool that improves and increases the efficiency of data collection and exchange of information among different professional figures involved in the design and production processes of products for the oil and gas sector. In fact, prototyping and labour-intensive activities usually require modifications and improvements to be made on-site that should be sent as feedback to the technical office. To this end, the proposed AR tool supports workers at the workplace to easily detect and annotate design variations made during their working activities and furthermore to formalize and automate the collecting and transferring of this data to the designers in order to prevent loss of information. Field experimentation has been carried out with end-users to evaluate their acceptance by means usability studies, based on objective and subjective metrics, and personal interviews. Experimental results show that the proposed AR tool provides medium-to-high levels of usability and has been positively accepted by all the participants involved in the study. [ABSTRACT FROM AUTHOR]

WAGES, MACHINE tools, DIAMOND turning, RAPID prototyping, OPTICS, MACHINING, and HYPERSPECTRAL imaging systems

Advancements in diamond turning technology with tool servo configurations enables the generation of precise freeform surfaces. However, the profile accuracy is mainly limited due to non-availability of an efficient tool path compensation techniques and precise alignment methods. The aim of this study is focused on developing a tool path compensation routine for slow tool servo machining of freeform optics. A seven-order polynomial freeform surface, designed for hyperspectral imaging is selected for experimentation. Alignment strategy by utilizing the available fiducials is presented to ensure the precise re-mounting of surface during machining and metrology. The contact type profilometer is used to measure the fabricated surface by taking 25 numbers of two-dimensional raster scans at an interval of 0.5 mm. The scans are then stitched to get the 3D surface measurement. The residual form error map is used to compensate the tool path. Significant reduction in form error, i.e., from peak to valley (PV) of 9.27 to 0.75 μm with surface finish (Ra) of 11.82 nm, is achieved by performing four machining iterations of compensation. The simulation studies are also presented to investigate the effects of various misalignments on manufacturing accuracies. The developed compensation process is effective for fast convergence of form error and to manufacture the precise freeform optics for various imaging and non-imaging applications. [ABSTRACT FROM AUTHOR]

3-D printers, THREE-dimensional printing, MANUFACTURING processes, EXTRUSION process, PRINT materials, and RAPID prototyping

Since the advent of 3D printing in the mid-1980s, additive manufacturing has grown steadily and found numerous applications across all types of industries. More recently, the industry has seen a spur of growth as the terms of the original patents expired and new companies entered the market. While there exist several different methods of additive manufacturing, polymer-based material extrusion 3D printing (also known as fused filament fabrication) has become one of the most widely used ones due to its lower cost, ease of use, and versatility. While development has greatly expanded the material availability and improved the quality of prints, material extrusion 3D printers have often faced a challenge in physical scaling. There are inherent design hurdles to the extrusion process when the print starts to grow larger. This paper aims to study the market landscape of extrusion-based 3D printing technology for polymer-based material as well as challenges faced in upscaling this technology for industrial applications. A prototype large-scale material extrusion 3D printer has been designed, constructed, and then tested to gain experimental data on large-scale 3D printing using thermoplastic polymers as a printing material. Results of testing and experimentation verified certain key design elements and how they can improve large-scale 3D printing. Testing also revealed how large diameter nozzles for the hot end introduce challenges not seen in small-scale 3D printers. This paper also seeks to consolidate available information pertaining to large-scale 3D printing into one comprehensive document. [ABSTRACT FROM AUTHOR]

STAINLESS steel, IRON & steel plates, LASERS, LASER beams, and RAPID prototyping

Laser forming is an innovative technique that uses a defocused laser beam to form sheet metal by thermal stresses rather than external forces. This offers excellent and promising potential applications in rapid prototyping, straightening, aligning, and adjusting of macro/micrometallic components. However, the undesirable edge effects in laser forming reflect that the bending angle is not constant along the scanning line. This paper presents an analytical study of edge effects in laser bending of AISI 304 stainless steel plate. Experimental and numerical investigations aimed at understanding the effects of the triangular beam geometry with different aspect ratios were clearly demonstrated. A validated thermal model was developed, and different sets of FE simulations were carried out by varying heat input values and aspect ratio of laser beam with constant scanning speed. It is evident that triangular beam with highest aspect ratio was preferable to produce a higher bending angle with lesser edge effect at higher power intensity. It is found that triangular beam geometries are more effective in minimizing the bending angle variation compared with the circular beam. [ABSTRACT FROM AUTHOR]

VIBRATION tests, AUTOMOBILE supply stores, AIRPLANE testing, COST analysis, ERROR analysis in mathematics, and MANUFACTURING industries

Single-point incremental forming has potential applications in prototyping and custom part manufacture for a range of industries including automotive and aerospace. For components with vertical walls, multiple passes are required to achieve a reasonable residual strain distribution and to accommodate large material strains without failure. In this paper, various multistage strategies were evaluated experimentally, and a complex C-channel fixture designed for aircraft vibration testing was successfully manufactured. Design guidelines for flat-base geometries are provided along with the rules for high-quality toolpath generation. A separate set of experiments was conducted comparing hemispherical and flat tools, and a flat tool was selected as being the most suitable for flat-base parts. The typical thickness variation developed in components and a geometrical error analysis are also presented. The response of the developed component to annealing and effect of this process on final geometrical errors are also reported. Cost analyses from design to development stage of the component are also presented. This work will be of practical interest to anyone seeking to bridge the gap between prototyping and large-scale production for complex flat-bottomed part geometries with single-point incremental forming. [ABSTRACT FROM AUTHOR]

HYDROSTATIC stress, RAPID prototyping, TECHNOLOGY, SURFACE roughness, AGRICULTURAL technology, and COMMERCIAL product testing

This study proposed and evaluated a highly precise method employing various diameters and shapes of punch to manufacture right-angled square-bodied products. In this method, a trough is not only engraved on the die but also designed into the punch. Five diameters and shapes of the punch were collocated with a circular trough around the square shape of a die cavity. In the tests, a ram descended to a fixed level, and part of the billet was forced into the trough without touching its bottom. This causes high hydrostatic stress on the cutting edge of the die. The pressure substantially reduces the occurrence of fractures in test products. The punch with a square trough engraved on its face produced a product with favorable shape and precision compared with other punch shapes. The results revealed that the proposed method can produce a product with a long and burnished surface with a roughness of 0.02–0.12 μm. The tolerance band for the width and thickness ranges from IT1 to IT3, and that for the right angle is 0.02–0.06°. The proposed method is a new rapid prototyping technology and has greater levels of precision than conventional manufacturing methods. [ABSTRACT FROM AUTHOR]

LASERS, CERAMIC materials, MANUFACTURING processes, and CAD/CAM systems

Quasi-tangential laser processing, also called laser turning, is increasingly applied for various applications. Specifically, its ability to generate complex geometries with small feature sizes at high precision and surface quality in hard, brittle, and electrically non-conductive materials is a key benefit. Due to the geometric flexibility, the process is well suited for prototyping in hard-to-machine materials such as ceramics, carbides, and super-abrasives. However, the lack of advanced software solutions for this novel process hitherto limited the exploitation of the potential. Here, we discuss a unique computer-aided manufacturing approach for synchronous 7-axes laser manufacturing with quasi-tangential strategies. This gives the peerless possibility to process arbitrary geometries, which cannot be manufactured with conventional techniques. A detailed description of the path calculation with derivation and procedures is given. The generated machine code is tested on a laser manufacturing setup consisting of five mechanical and two optical axes. Following, a processed cylindrical ceramic specimen with a continuously varying profile along a helical path is presented. The profile is constituted by a rectangular over half-spherical to a triangular groove with defined pitch on the helix. This demonstrator provides the validation of the presented CAM solution. Measurements of the produced specimen show high adherence with the target geometry and an average deviation below 10 μm. [ABSTRACT FROM AUTHOR]

RAPID prototyping, SHEET-steel, ELECTRIC currents, TITANIUM, and SHEET metal

Single point incremental forming (SPIF) is an emerging forming process for rapid prototyping and manufacturing of complex components from sheet metals. Recently, the use of electric current for the local resistance heating of the deformation area has attracted much attention in SPIF. In order to further study the electric hot incremental sheet forming (EHISF), in the present research, the effect of utilizing various lubricants on the formability of Ti-6Al-4V, AA6061, and DC01 sheet metals is experimentally investigated by forming a truncated cone under different feed rates, vertical pitches, and electric currents. To this end, the Taguchi design of experiment (DOE) and the analysis of variance (ANOVA) are employed. The results showed that the formability of Ti-6Al-4V and AA6061 sheets can be improved using the EHISF. For both the sheets, the lubricant and the electric current have significant effects on the maximum achievable forming depth. In addition, the formability of the DC01 sheet is highly affected by the lubricant and the feed rate. The results of the DC01 sheet showed that at the considered wall angle, the maximum forming depth in the EHISF does not change, compared to the cold SPIF, but the thickness distribution of the formed part at a higher temperature is more uniform. [ABSTRACT FROM AUTHOR]

RESIDUAL stresses, POWDERS, RESIDUAL stresses measurement, TOOL-steel, MELTING, and LASER beams

The occurrence of residual stresses in selective laser melting (SLM) presents challenges that limit the capability of the process to manufacture parts at industrial scale. These stresses can have irreversible effects such as warping and cracking of parts during and post manufacturing. One of the most important SLM parameters that should be controlled carefully in order to effectively manage residual stresses is the scanning strategy. This study presents an evaluation of four different scanning strategies, namely the island, successive, successive chessboard and least heat influence (LHI) scanning strategies with respect to their influence on residual stresses and distortions. All the scanning strategies were investigated by melting single tracks on tool steel substrates without powder. Measurement of residual stresses was performed on selected positions on the substrates before and after exposure to the laser beam using the x-ray diffraction technique. The successive chessboard scanning strategy was found to contribute to the least average residual stresses, and lowered residual stress by up to 40% relative to the default island scanning strategy. Further to this, the influence of the successive chessboard and island scanning strategies on distortions was evaluated. Similar to the residual stress findings, the successive chessboard contributed to lower form deviations compared to the island strategy. The scanning strategies were also evaluated based on their impact on total scanning times, with the successive chessboard strategy showing slightly lower scanning time than that for the island and LHI chessboard strategies. [ABSTRACT FROM AUTHOR]

RAPID prototyping, MANUFACTURING processes, SPLINES, SIMPLE machines, DEVELOPMENTAL biology, and PROSPECTING

For successful development of the intelligent manufacturing of freeform surfaces using STEP-CNC with online toolpath generation capability, it is required to make a choice of the optimal representation of a 3D model which will be used for machining. Traditionally, most existing CAD-CAM systems use NURBS to design freeform surfaces and to perform toolpath generation in order to machine them. The introduction of T-splines to CAD systems and some reported results of using them in manufacturing makes it possible to consider T-splines, or more generally T-NURCCs (Non-Uniform Rational Catmull-Clark Surfaces with T-junctions), as a good solution for the development of the STEP-NC-based manufacturing of freeform surfaces because of their advantages over NURBS. Therefore, this paper gives an overview of the main arguments in favor of choosing the T-spline surface representation for integration within STEP-CNC systems. We examine the prospects for T-splines to become an integral part of modern manufacturing systems, and highlight some important properties of T-splines which are the most beneficial for manufacturing processes. The paper presents the results of the development of a complete T-spline-enabled STEP-CNC system which can strategically support online toolpath generation for three-axis ball end machining of simple T-spline surfaces using four different freeform strategies defined in ISO 14649-11. These results represent the implementation of the first stage of the development process of intelligent STEP-CNC systems, and in the future more research is needed in this direction. [ABSTRACT FROM AUTHOR]

ALUMINUM alloys, WAGES, ROBOTIC path planning, SHEET metal, and RAPID prototyping

Incremental sheet forming (ISF) is a new and rapid forming process which produces parts without using specific die. One of the key challenges is geometric accuracy especially for complex sheet metal parts. In the presented work, a typical non-axisymmetric part of AA5052 with stepped feature was studied through orthogonal experiments with 4 parameters in 4 levels to determine the optimal process parameters for better geometric accuracy. Based on the optimum process parameters, the strategy on further reducing geometric deviation was investigated, and the compensation was made on each tool path during multi-pass incremental forming. The intermediate configurations were designed to avoid the interaction of different features and improve the smoothness of material flow. Based on the proposed methodology, the geometric accuracy of non-axisymmetric part with stepped feature has been obviously improved, particularly at the stepped feature. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, CONCEPTUAL design, FREQUENCY selective surfaces, METAL coating, ROBOTICS, SURGICAL robots, and MEDICAL robotics

In this paper, a novel concept of robotic manipulator is developed for direct additive manufacturing on non-planar surfaces. The application scenario is the metal coating of the internal surface of radome systems, using frequency selective surface patterns. The manipulator is presented from the design, modeling, and control point of view. It is developed following an application-driven approach, meaning that the requirements from the application and the additive manufacturing technology are translated into the design specifications of the robotic system. Simulation results demonstrate that the proposed control strategy based on a decentralized architecture is satisfactory to accurately control the motion of the robotic mechanisms along the trajectory foresees by the direct additive manufacturing task. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, THREE-dimensional display systems, TECHNOLOGY, and MANUFACTURING processes

In 2014, NASA, in partnership with Made In Space, Inc., launched the first 3D printer to the International Space Station (ISS). Results of the first phase of operations for this mission demonstrated the use of the fused filament fabrication (FFF) process for 3D printing in a microgravity environment. Previously published results indicated differences in density and mechanical properties of specimens printed in microgravity and those manufactured with the printer prior to its launch to ISS. Based on extensive analyses, these differences were hypothesized to be a result of subtle changes in manufacturing process settings rather than a microgravity influence on the FFF process. Phase II operations provided an opportunity to produce additional specimens in microgravity, evaluate the impact of changes in the extruder standoff distance, and ultimately provide a more rigorous assessment of microgravity effects through control of manufacturing process settings. Based on phase II results and a holistic consideration of phase I and phase II flight specimens, no engineering-significant microgravity effects on the process are noted. Results of accompanying material modeling efforts, which simulate the FFF process under a variety of conditions (including microgravity), are also presented. No significant microgravity effects on material outcomes are noted in the physics-based model of the FFF process. The 3D Printing in Zero G Technology Demonstration Mission represents the first instance of off-world manufacturing. It represents the first step toward transforming logistics for long-duration space exploration and is also an important crew safety enhancement for extended space missions where cargo resupply is not readily available. This paper presents the holistic results of phase I and II on-orbit operations and also includes material modeling efforts. [ABSTRACT FROM AUTHOR]

ELECTRIC heating systems and REVERSE engineering

The single-point incremental forming process is an emerging process, which presents an alternative to the conventional sheet metal-forming processes like stamping and drawing. It is known to be perfectly suited for prototyping and small series. The incremental forming process offers the possibility of manufacturing medical prosthesis or implants specific to each patient, which are more comfortable and guarantee better performance. A reverse engineering approach associated with single-point incremental forming process in order to produce a titanium prosthesis of human skull is developed. It allows guaranteeing the high degree of customization required. In this paper, several novel warm forming experimental setup equipped with instruments to measure efforts and temperature monitoring is proposed. This new warm setup is feasible and makes it easy to monitor force and temperature sheet at forming; it gives it the ability to be exploited in the industry of manufacturing titanium alloy medical shapes. The real geometry of a skull prosthesis is re-constructed from a laser scanning technique, and specific treatments are performed until a CAD model is obtained. From it, the forming punch trajectories have been defined, and skull prostheses are manufactured using the technology of single-point incremental forming in titanium material at different temperatures. [ABSTRACT FROM AUTHOR]

CASTING (Manufacturing process), RAPID prototyping, STAINLESS steel, POLYSTYRENE, LASER sintering, and STEREOLITHOGRAPHY

Rapid casting is the product of digital, information, and optimization of casting technology. It mainly includes rapid prototyping and virtual manufacturing. In order to shorten the production cycle of a stainless steel closed impeller casting, the wax pattern was made by high impact polystyrene (HIPS) with a selective laser sintering and photosensitive resin with stereolithography (SL). In order to prevent the formation of shrinkage defects, different gating systems designed to examine the molten metal flow and solidification behavior during the pouring and solidification process. The results show that pouring temperature is 1550 °C and pouring speed is 0.75 m/s, which is favorable for filling impeller castings, and can avoid casting defects. The optimized gating system prevented surface shrinkage and interior defects. The optimized gating systems have been verified by experiment, and the rapid casting has been realized based on 3D printing wax pattern and simulation optimization. This rapid casting can reduce processing time and costs, and enhance casting quality in the foundry industry. [ABSTRACT FROM AUTHOR]

CLOUD computing, THREE-dimensional printing, RAPID prototyping, MANUFACTURING processes, and RESEARCH & development

At present, some service platforms for 3D manufacturing encounter problems, including the low level of integration with digital design ability, the single character of cooperative printings, the uneven distribution of 3D printing resources, and the high 3D design requirements of users. To overcome these issues, a cloud service platform for the seamless integration of digital design and rapid prototyping manufacturing was established using ASP.NET, WebGL, WebSocket, and SQL Server in combination with C# language and JavaScript. The goals were to realize a design and rapid prototyping of mechanical equipment parts that are browser based and provide online digital design services, such as the parametric design of key parts, downloading of models, format conversion, and virtual assembly. The client application layer, server processing layer, database layer, and working machine end application layer of this cloud 3D printing platform were set up. The result of the design module could be printed remotely in 3D. Practical application showed that the platform could effectively improve the R&D and design speed of the parts and components of the mechanical equipment and reduce the effort of designers. In particular, this platform would be suitable for users without a 3D design background. The design and rapid prototyping parts of the platform satisfied the dimensional precision required by enterprises, which provides an important basis for the further verification of the design correctness for small- and medium-sized enterprises and has high application value. [ABSTRACT FROM AUTHOR]

RELIABILITY in engineering, VIRTUAL prototypes, MULTIBODY systems, ANALYTICAL mechanics, and FAILURE mode & effects analysis

The reliability analysis is a quantification of the sources of failures in a product, with emphasis on the most significant contributors towards the overall product unreliability. As the reliability analysis of complex products is very crucial for analyzing the behavior of the products, many researches have been focused on it in recent decades with a result of many valuable contributions. However, current researches always focus on rigid product, while the product is always a rigid-flexible coupling multibody system, which could affect the accuracy of reliability analysis. This paper is devoted to virtual prototyping-based approach to a fuzzy Failure Mode, Effects, and Criticality Analysis (FMECA) with the consideration of rigid-flexible coupling virtual prototyping model. This paper discussed proposed approach in detail with three steps: the traditional FMECA method, the fuzzy FMECA method, and the rigid-flexible coupling-based analysis for FEMCA. The cold heading machine is given as an example which demonstrates that the methodology is helpful to reliability analysis. The physical prototyping is also carried out to demonstrate the product reliability. [ABSTRACT FROM AUTHOR]

AUTOMOTIVE engineering, FINITE element method, STRENGTH of materials, CAST-iron, and THREE-dimensional printing

Lightweight engineering is a current topic in mechanical industry. The mass reduction is a common design objective to reduce product cost and environmental impacts. Virtual prototyping tools are widely applied to study new lightened solutions and check the compliance with regulations and standards. However, an integrated approach, involving simulations and life-cycle analysis, is necessary to support design optimization and decision-making. The scope of this study concerns the definition of an Ecodesign approach to support the lightweight engineering of cast iron parts through the redesign of the product shape. In particular, this paper deals with the optimization of a ductile cast iron manhole. The test case shows a redesign method which considers structural analysis with environmental impacts. The structural analysis has been evaluated using a finite element method tool. In particular, the simulation results have been compared and validated with physical tests. The environmental analysis is based on the methodology provided by the standardized ISO 14040:2006 and ISO 14044:2006. The proposed LCA study considers the phases of manufacturing and transport related to one ductile iron product. The described manufacturing phase is related to a Chinese foundry which produces roughly 12,000 tons of ductile cast-iron castings. The results show the possibility to achieve about 20% of mass reduction for one casting. Considering such mass decreasing, the related reduction in terms of carbon emission is about 7%. Summarizing, this paper shows a design approach to integrate the structural improvements with the reduction of the environmental impacts related to a lighter weight casting. [ABSTRACT FROM AUTHOR]

MICROSTRUCTURE, MECHANICAL properties of metals, THREE-dimensional printing, DIRECT metal laser sintering, and TENSILE strength

Additive manufacturing (AM) started as a rapid prototyping (RP) technology to aid in visualizing and validating designs in the design process. However, with the recent improvements in metal AM parts, functional parts can be manufactured using laser-based AM. Currently, metal AM parts have comparable mechanical properties to traditional manufacturing parts. 15-5PH stainless steel and Inconel 718 are two of the most commonly used metals in laser-based AM, and they have a high modulus of elasticity and tensile strength and can be precipitate hardened to increase their strength and hardness by heat treatment. These properties make 15-5PH stainless steel and Inconel 718 suitable for many industrial applications such as aerospace and automotive. However, due to the nature of AM, AM parts usually suffer from anisotropy. In this paper, the mechanical properties such as tensile strength, modulus of elasticity, yield strength, and ductility are investigated at various elevated temperatures up to 350 °C and compared with the mechanical properties at room temperature using specimens printed in three different orientations to capture the effect on the anisotropy. In addition to that, the microstructure of the specimens is studied to investigate the influence of elevated temperature on the specimens. [ABSTRACT FROM AUTHOR]

POLYLACTIC acid, FUSED deposition modeling, CARBON-black, GRAPHENE, and TEMPERATURE coefficient of electric resistance

This study characterizes the microstructure and temperature dependence of resistance of two commercially available electrically conductive polylactic acid (PLA) composites for fused deposition modeling (FDM): PLA-carbon black and PLA-graphene. No microstructural changes were observed between the filament and the printed parts; however, the resistivity of the filament was found to drop by four to six times upon FDM. Also, compared to the resistivity of individual extruded wire, the resistivity of the printed parts was found to be up to 1500 times higher for PLA-graphene and up to 300 times higher for PLA-carbon black. The raw PLA-carbon black filament and printed wire showed a positive temperature coefficient of resistance (α) value between ~ 0.03 and 0.01 °C−1, which makes them more suitable for sensor development. The raw PLA-graphene filament and printed wire did not exhibit a significant α, which makes them more suitable for printing wires. However, the parts made with multilayer FDM exhibited a negative or a negligible α up to a certain temperature prior to exhibiting a positive α; further, these α values were significantly lower than those obtained for the filaments before or after extrusion. These findings enable proper selection of commercial conductive FDM filaments for enabling quicker prototyping of electronics and sensors. [ABSTRACT FROM AUTHOR]

SHEET metal, SPRINGBACK (Elasticity), DIES (Metalworking), MACHINING, and MANUFACTURING processes

Sheet metal structures produced by bending are extensively used in a wide variety of industries. Rapid production of such workpieces is well sought after for low production volume demands. An effective and practical way to reduce springback is through compensating die dimensions, which has proved to be economic for large production scenario. However, in the environment of rapid production, part dimensions and/or material composition change frequently and hence new dies have to be designed and made to address these changes even if they are minor. Such situation inevitably incurs significant effort and high expenditure on determining appropriate die dimensions and fabricating new dies, and therefore imposes both time and financial burdens on producing angular sheet metal workpieces particularly at very low production volumes. This paper presents an effective and economic way of prototyping sheet metal workpieces with angular dimensional accuracy maintained, however without the need of creating new dies. The methodology extends from the author's previous work on angular dimension improvement as reported by Li and Sekar (Proceedings of the 2016 Manufacturing Science and Engineering Conference, MSEC2016, 2016) to the rapid prototyping of sheet metal structures and process planning of bending-machining hybrid process. Three case studies are provided in the paper and the outcome shows that the methodology is capable of prototyping angled sheet metal workpieces with existing dies that are not designed nor compensated for the prototype models. [ABSTRACT FROM AUTHOR]

TISSUE engineering, CRYSTALLOGRAPHIC shear, BIOACTIVE glasses, MICROSTRUCTURE, and FABRICATION (Manufacturing)

This paper reports a study on the development of bioactive glass powders for biofabrication of scaffolds by an additive manufacturing technique, three-dimensional printing (3DP). Several formulations of the glass were developed from the CaO·P2O5·TiO2 system and prepared on the basis of the results for the commercial powder characterization (average particle size, particle size distribution, microstructural and crystallographic analysis). For printing the glass models in the prototyping machine, a virtual model defined as the “standard model” was produced in commercial powder, and a systematic study of the relevant processing parameters (binder composition, formulation of powder, saturation level in the shell and core, bleed compensation, and printed layer thickness) was carried out in order to determine the most suitable conditions for the fabrication of porous structures for tissue engineering applications. The printed glass models were sintered through specific thermal programs and then characterized in terms of dimensions, structure, morphological features, and mechanical properties. Finally, the sintered models were submitted to mineralization tests in simulated physiological media. In this work, it was demonstrated that it is possible to use a printing machine to manufacture 3DP glassy porous structures with suitable features for tissue engineering applications as temporary scaffolds. The mechanical properties of the produced structures and its mineralization capability in physiological fluids suggest that they have potential to be used in bone tissue regeneration under low load-bearing situations. [ABSTRACT FROM AUTHOR]

INTRAOCULAR lenses, MANUFACTURING processes, TREATMENT of cataracts, REFRACTIVE errors, and RAPID prototyping

Intraocular lens implantation surgery is the only approach for cataract treatment at present. Apart from removing the cloudy lens, correction of refractive errors becomes the second main function of intraocular lenses. This paper systematically summarizes the intraocular lenses in terms of its material, design, manufacturing and evaluation. The next generation of intraocular lenses with customized freeform surfaces is highlighted from the lens design viewpoint. The status of processing and measurement methods is presented for both current intraocular lenses and future freeform lenses. Finally, the research perspectives are outlined. [ABSTRACT FROM AUTHOR]

MACHINING, SCHEDULING, MATHEMATICAL decoupling, and RAPID prototyping

The feedrate scheduling of parametric interpolator is one of the most important factors for a high-performance CNC machining, since it directly concerns the machining efficiency, machining accuracy, and cutting stability. In this paper, an adaptive feedrate scheduling method with limited contour error and axis jerks is proposed for free-form contour machining based on a strategy of moving knot sequence. The analytical relations between dynamic contour error and feedrate are first derived explicitly, and then the formula of maximum feedrate limit under confined contour error and axis jerks is yielded using a numerical decoupling scheme. Consequently, the maximum feedrate limit satisfying the above constraints is obtained for each predefined parametric segment of the tool path. Further, a bidirectional scanning algorithm is employed to globally adjust the local minimum feedrate values of all feedrate segments. On the basis of feedrate segments with local minimum value and maximum recommendation value, an exact knot sequence configuration method for the B-spline curve, which is used to express the initial feedrate profile, is proposed. Finally, a simple feedrate relaxation algorithm is performed to generate the final feedrate profile with entirely limited contour and axis jerks by utilizing a strategy of moving knot sequence. The proposed feedrate scheduling method is validated by several typical experimental tests, and the results demonstrate the effectiveness and reliability of the proposed method. [ABSTRACT FROM AUTHOR]

BEVEL gearing, GEOMETRY, FABRICATION (Manufacturing), MANUFACTURING processes, and THREE-dimensional printing

The growth of additive manufacturing technology allows the fabrication of complete functional devices with complex geometries with ease and low cost. This technology allows the fabrication of pieces that could not be made in the past with traditional manufacturing techniques, in this case, bevel gears with exact spherical involute (ESI). Focusing on this issue, this paper presents a method for the geometric design and fabrication of practical industrial-like ESI bevel gears with variable surface detail. The definition of the tooth profiles on back cones is proposed introducing a projection procedure for straight and spiral toothing. An in-house-developed software package was developed to test the method, and a pair of plastic examples were fabricated on a generic 3D printer. A comparison between the fabricated pinion and its STL model was conducted for validation purposes. Mean deviations of 0.22 and 0.15mm were obtained for the whole model and for the contact surfaces comparison, respectively. Thus, the fabrication of bevel gears using AMT is achieved, and can be implemented to a specific application using a particular additive manufacturing technique. [ABSTRACT FROM AUTHOR]

RAPID prototyping, COMPUTER-aided process planning, PRODUCTION planning, MILLING machinery, and MILLING-machines

Feature recognition is an important function of computer-aided process planning (CAPP) system. The freeform feature recognition works performed so far have resulted in successful classification and recognition of freeform surface-based features, but the works do not classify and recognize freeform volumetric features. The research works like automatic generation of delta volume (DV) for volumetric features, finishing, and roughing process were successful when applied to regular form parts, but generated a complex DV for roughing process when applied to freeform parts. Also, the DV generation works do not generate DV for freeform features. So an effort is made (i) to newly classify freeform volumetric features and develop an algorithm to automatically generate DV for freeform volumetric features; (ii) to automatically recognize freeform volumetric features by a set of conditions and colour coding concept; and (iii) to determine the level of complexity and milling machine selection. The problem of complex DV is overcome by generation of sub-delta volume for transition (SDVT). The algorithm is able to recognize freeform volumetric features and the DV’s quantitative data, exploded view, and labelling will aid the downstream activities of CAPP system. The algorithm validation result shows a percentage error of 0.005% for complex part like impeller. [ABSTRACT FROM AUTHOR]

SHEET metal, ULTRASONICS, VIBRATION (Mechanics), METALWORK, and RAPID prototyping

The incremental sheet forming (ISF) is an innovative dieless forming process featured with high formability and short lead time which is suitable for rapid prototyping and small volume production. The integration of ultrasonic (US) vibration into the ISF process can significantly reduce the forming force and bring other benefits. In this work, the impacts of process parameters including the sheet material, US power, feeding speed, and tool diameter, on force reduction and temperature increment were studied. The force reduction contains two components—the stress superposition-induced force reduction and acoustic softening-induced force reduction. The stress superposition-induced force reduction was analyzed by finite element simulation while the total force reduction was detected by experiments since currently, the unknown mechanism of the acoustic softening cannot be modeled. The temperature increment was measured by a high-speed infrared camera. The results show that the force reduction can go up to 56.58% and the temperature increment can be as high as 24.55 °C. In general, the material with a higher yield stress results in a higher force reduction and a higher temperature increment. A higher US power or a lower feeding speed can significantly enhance the force reduction and the interface temperature increment. The tool with a smaller diameter has a comparable effect as a larger tool, but a larger vibration amplitude is required. [ABSTRACT FROM AUTHOR]

MACHINING, MACHINE tools, RAPID prototyping, K-means clustering, and MANUFACTURING processes

Due to the geometric complexity, tool orientations usually change dynamically during freeform surface machining with 5-axis machine tool. As the kinematic performance of the rotary axes is usually weaker than that of the linear axes, the real cutting speed is difficult or even impossible to reach the desired level, which further leads to low machining efficiency. This paper presents a region-based 3 + 2-axis machining toolpath generation method with 5-axis machine tool. The surface is first divided into several preliminary sub-surfaces using K-means clustering algorithm. A post processing procedure is then carried out to optimise the preliminary sub-surfaces to ensure the machinability. For each sub-surface, gouging-/collision-free tool orientations are first calculated and then the optimal combination of the fixed tool orientation and the feed direction is determined by maximising the average machining strip width for toolpath generation. The proposed method is tested by a case surface and the comparisons to some other traditional methods are also provided. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, COMPUTER scheduling, PARTICLE swarm optimization, QUADRATIC programming, and RAPID prototyping

The problem of service matching and scheduling in cloud manufacturing (CMfg) is complex for different types of manufacturing services. 3D printing, as a rapidly developing manufacturing technology, has become an important service form in the CMfg platform due to its characteristics of personalized manufacturing. How to solve the task scheduling problem for distributed 3D printing services in CMfg needs further research. In this paper, a service transaction model of 3D printing services in CMfg is built. Based on the service transaction model, we propose 3D printing service matching strategies and matching rules of different service attributes, including model size, printing material, printing preciseness, task cost, task time, and logistics. To reduce the delivery time of tasks from service suppliers to service demanders, a 3D printing service scheduling (3DPSS) method is proposed to generate optimal service scheduling solutions. In 3DPSS, optimization objective, constraints, and optimization algorithm are presented in detail. Experimental results show that the average task delivery time of 3DPSS is shorter than that of typical scheduling methods, such as particle swarm optimization, pattern search, and sequential quadratic programming, when the amounts of tasks change. [ABSTRACT FROM AUTHOR]

COMPUTER-aided design, ALGORITHMS, TOPOLOGY, HOLES, and RAPID prototyping

The existing method to determine the parting direction for core and cavity of two-plate mold is usually limited to decided types of direction. This limitation reduces the capability of the existing method to select the best parting direction for a 3D CAD model of an object. This paper introduces a new algorithm for another alternative that overcomes the limitation and takes less computational time by using the boundary representation (B-rep) of a visibility map to determine the parting direction. By extracting the geometric and topological information of a visibility (V) map, a B-rep entity is created to represent the V-map, which replaces the existing method that uses convex hull algorithms. To illustrate the capability of the algorithm, the 3D CAD model of objects with regular and freeform faces, holes, protrusion, and depression is presented. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, COMPUTER-aided design, MANUFACTURING processes, RAPID prototyping, and ROBOTICS

Additive manufacturing (AM, generally called 3D printing) has attracted great research interests due to its ability to build complex shapes. It transforms design files to functional products through slicing and material accumulation. Typically, the planar slicing strategy is used in AM to convert CAD model into accumulating layers. However, when building overhang structures and curved parts, it often needs support structures and generates a large number of planar layers, which lead to the fact that it spends more time in manufacturing. To reduce the need for support structures and decrease the number of layers, this paper presents two nonplanar slicing approaches: a decomposition-based curved surface slicing strategy and a transformation-based cylinder surface slicing method. The former is implemented based on STEP models and the latter is capable of slicing mesh models. The feasibility of the proposed methods are validated by printing two parts with a robotic fused deposition modelling system. [ABSTRACT FROM AUTHOR]

SURFACE roughness, THREE-dimensional printing, MANUFACTURED products, RAPID prototyping, and SURFACES (Technology)

A theoretical formula for surface roughness of layer-based manufactured parts in additive manufacturing is developed considering a more accurate definition of the centerline by minimizing the total arithmetic deviations of the actual surface profile. The developed model is experimentally validated, and it is compared with those that are used in common practices. Considering the uncontrolled process variables and the complexity of the numerical solutions, the analytical and experimental results show satisfying agreement. A methodology is also developed to decide whether the objective surface slope is feasible with the current number of layers and how the layers need to be laid down to achieve the desired surface accuracy. The methodology yields more accurate small features on the surfaces of the layer-based manufactured products. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, EXTRUSION process, MATHEMATICAL optimization, HIGH energy forming, and RAPID prototyping

A problem with the planning solutions for the additive manufacturing material extrusion process is a lack of optimization strategies to improve upon the standard raster and contour tool paths. Bead deposition tool paths can cause unwanted voids, which in turn creates a set of potential failure points within the finished product. This paper aims to identify, minimize, and manage void regions during the tool path generation. The goal is to minimize voids in each layer and to prevent stacked void regions, i.e., avoid creating an internal chimney. Material extrusion processes, with a wide selection of nozzle sizes (0.4 to 21 mm), are considered suitable candidates for this solution. The mathematical model is established based on the component geometry and the available build options for a given machine-material configuration. A C++ program has been developed to select a set of standard (available) tool path parameters to determine the optimal output process variables (bead width, raster angle, and the overlap percentage). Case studies are presented to show the merits of this approach. [ABSTRACT FROM AUTHOR]

THREE-dimensional printing, MANUFACTURING processes, HOOKS, BAGS, FUSED deposition modeling, and RAPID prototyping

This paper deals with design for manufacturing (DFM) approach for additive manufacturing (AM) to investigate simultaneously the different attributes and criteria of design and manufacturing. The integrated design approach is provided in the product definition level and it gradually maps the customer requirements to the final product model. The main contribution of this paper is an interface processing engine that is an interface between the product model and manufacturing model. This study uses the Skin-Skeleton approach to model the first definition of the product and model the material flow of AM technology as the manufacturing process. This engine is developed through analysis of all AM technologies and identification of their parameters, criteria, and drawbacks. In order to evaluate some product and process parameters, a multi-objective problem is formulated based on the analysis of all AM technologies; production time and material mass are optimized regarding mechanical behavior of the material and roughness of product. The approach is validated by a case study through a bag hook example. From its requirement specification to the proposed approach, this article defines an optimized product and its manufacturing parameters for fused deposition modeling (FDM) technology. [ABSTRACT FROM AUTHOR]