articles+ search results

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]

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]

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]