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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]

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]

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]

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]