Building free-form thin shell parts using supportless extrusion-based additive manufacturing
TL;DR: In this paper, a neural network-based compensated trajectory generation scheme was proposed to build accurate thin shell parts using supportless extrusion-based additive manufacturing (SILAM) by dynamically reorienting the build-platform.
Abstract: Conventional material extrusion additive manufacturing is capable of building complex structures. Overhanging features require the use of support structures. Printing the support structure requires additional time and material. Conventional processes need time to remove support material and may lead to degraded surface finish. The use of support structures can be avoided by dynamically reorienting the build-platform. This paper presents a novel approach to build accurate thin shell parts using supportless extrusion-based additive manufacturing. We describe the layer slicing algorithm, the tool-path planning algorithm, and the neural network-based compensated trajectory generation scheme to use a 3 degree of freedom build-platform and a 3 degree of freedom extrusion tool to build accurate thin shell parts using two manipulators. Such thin shell parts cannot be built without supports by previous supportless AM processes. We illustrate the usefulness of our algorithms by building several thin shell parts.
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TL;DR: A critical review of the state of art materials in the categories such as metals and alloys, polymers, ceramics, and biomaterials are presented along with their applications, benefits, and the problems associated with the formation of microstructures, mechanical properties, and controlling process parameters.
Abstract: Additive Manufacturing (AM) is the significantly progressing field in terms of methods, materials, and performance of fabricated parts. Periodical evaluation on the understanding of AM processes and its evolution is needed since the field is growing rapidly. To address this requirement, this paper presents a detailed review of the Additive Manufacturing (AM) methods, materials used, and challenges associated with them. A critical review of the state of art materials in the categories such as metals and alloys, polymers, ceramics, and biomaterials are presented along with their applications, benefits, and the problems associated with the formation of microstructures, mechanical properties, and controlling process parameters. The perspectives and the status of different materials on the fabrication of thin-walled structures using AM techniques have also been discussed. Additionally, the main challenges with AM techniques such as inaccuracy, surface quality, reinforcement distribution, and other common problems identified from the literature are presented. On the whole, this paper provides a comprehensive outlook on AM techniques, challenges, and future research directions.
95 citations
TL;DR: This paper presents a new lattice infill structure generation algorithm, which is able to achieve both the self-supporting condition for the infills and the support-free requirement at the boundary surface of the part, and proposes a printing sequence optimization algorithm for determining a collision-free order of printing of the connected lattices infills.
Abstract: In additive manufacturing, infill structures are commonly used to reduce the weight and cost of a solid part. Currently, most infill structure generation methods are based on the conventional 2.5-axis printing configuration, which, although able to satisfy the self-supporting condition on the infills, suffer from the well-known stair-case effect on the finished surface and the need of extensive support for overhang features. In this paper, based on the emerging continuous multi-axis printing configuration, we present a new lattice infill structure generation algorithm, which is able to achieve the self-supporting condition for both the infills and the boundary surface of the part. The algorithm critically relies on the use of three mutually orthogonal geodesic distance fields that are embedded in the tetrahedral mesh of the solid model. The intersection between the iso-geodesic distance surfaces of these three geodesic distance fields naturally forms the desired lattice of infill structure, while the density of the infills can be conveniently controlled by adjusting the iso-values. The lattice infill pattern in each curved slicing layer is trimmed to conform to an Eulerian graph so to generate a continuous printing path, which can effectively reduce the retractions of the nozzle during the printing process. In addition, to cater to the collision-free requirement and to improve the printing efficiency, we also propose a printing sequence optimization algorithm for determining a collision-free order of printing of the connected lattice infills, which seeks to reduce the air-move length of the nozzle. Ample experiments in both computer simulation and physical printing are performed, and the results give a preliminary confirmation of the advantages of our methodology.
21 citations
Cites background from "Building free-form thin shell parts..."
...[24] developed an algorithm to print accurate thin-shell parts with no support....
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TL;DR: Li et al. as mentioned in this paper proposed a new lattice infill structure generation algorithm based on the emerging continuous multi-axis printing configuration, which is able to achieve both the self-supporting condition for the infills and the support-free requirement at the boundary surface of the part.
Abstract: In additive manufacturing, infill structures are commonly used to reduce the weight and cost of a solid part. Currently, most infill structure generation methods are based on the conventional 2.5-axis printing configuration, which, although able to satisfy the self-supporting condition on the infills, suffer from the well-known stair-case effect on the finished surface and the need of extensive support for overhang features. In this paper, based on the emerging continuous multi-axis printing configuration, we present a new lattice infill structure generation algorithm, which is able to achieve both the self-supporting condition for the infills and the support-free requirement at the boundary surface of the part. The algorithm critically relies on the use of three mutually orthogonal geodesic distance fields that are embedded in the tetrahedral mesh of the solid model. The intersection between the iso-geodesic distance surfaces of these three geodesic distance fields naturally forms the desired lattice of infill structure, while the density of the infills can be conveniently controlled by adjusting the iso-values. The lattice infill pattern in each curved slicing layer is trimmed to conform to an Eulerian graph so to generate a continuous printing path, which can effectively reduce the nozzle retractions during the printing process. In addition, to cater to the collision-free requirement and to improve the printing efficiency, we also propose a printing sequence optimization algorithm for determining a collision-free order of printing of the connected lattice infills, which seeks to reduce the air-move length of the nozzle. Ample experiments in both computer simulation and physical printing are performed, and the results give a preliminary confirmation of the advantages of our methodology.
16 citations
22 Jun 2021
TL;DR: In this paper, the authors present a motion planning method to support the manufacturing realization of designed toolpaths for multi-axis additive manufacturing, where problems of singularity and collision are considered in an integrated manner to improve the motion therefore the quality of fabrication.
Abstract: Multi-axis additive manufacturing enables high flexibility of material deposition along dynamically varied directions. The Cartesian motion platforms of these machines include three parallel axes and two rotational axes. Singularity on rotational axes is a critical issue to be tackled in motion planning for ensuring high quality of manufacturing results. The highly nonlinear mapping in the singular region can convert a smooth toolpath with uniformly sampled waypoints defined in the model coordinate system into a highly discontinuous motion in the machine coordinate system, which leads to over-extrusion/ under-extrusion of materials in filament-based additive manufacturing. The problem is challenging as both the maximal and the minimal speeds at the tip of a printer head must be controlled in motion. Moreover, collision may occur when sampling-based collision avoidance is employed. In this letter, we present a motion planning method to support the manufacturing realization of designed toolpaths for multi-axis additive manufacturing. Problems of singularity and collision are considered in an integrated manner to improve the motion therefore the quality of fabrication.
12 citations
TL;DR: A user-interactive modeling and fabricating framework using sweeping lines as the design tool for ceramic printing, which integrates the ceramic printing constraints like self-supporting and collision-free in the modeling stage and proposes a customized method for generating the printing file.
12 citations
References
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Book•
01 Jan 2009
TL;DR: Gibson et al. as discussed by the authors presented a comprehensive overview of additive manufacturing technologies plus descriptions of support technologies like software systems and post-processing approaches, and provided systematic solutions for process selection and design for AM Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing.
Abstract: Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing deals with various aspects of joining materials to form parts. Additive Manufacturing (AM) is an automated technique for direct conversion of 3D CAD data into physical objects using a variety of approaches. Manufacturers have been using these technologies in order to reduce development cycle times and get their products to the market quicker, more cost effectively, and with added value due to the incorporation of customizable features. Realizing the potential of AM applications, a large number of processes have been developed allowing the use of various materials ranging from plastics to metals for product development. Authors Ian Gibson, David W. Rosen and Brent Stucker explain these issues, as well as: Providing a comprehensive overview of AM technologies plus descriptions of support technologies like software systems and post-processing approaches Discussing the wide variety of new and emerging applications like micro-scale AM, medical applications, direct write electronics and Direct Digital Manufacturing of end-use components Introducing systematic solutions for process selection and design for AM Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing is the perfect book for researchers, students, practicing engineers, entrepreneurs, and manufacturing industry professionals interested in additive manufacturing.
3,087 citations
TL;DR: Future directions such as the "print-it-all" paradigm, that have the potential to re-imagine current research and spawn completely new avenues for exploration are pointed out.
Abstract: Additive manufacturing (AM) is poised to bring about a revolution in the way products are designed, manufactured, and distributed to end users. This technology has gained significant academic as well as industry interest due to its ability to create complex geometries with customizable material properties. AM has also inspired the development of the maker movement by democratizing design and manufacturing. Due to the rapid proliferation of a wide variety of technologies associated with AM, there is a lack of a comprehensive set of design principles, manufacturing guidelines, and standardization of best practices. These challenges are compounded by the fact that advancements in multiple technologies (for example materials processing, topology optimization) generate a "positive feedback loop" effect in advancing AM. In order to advance research interest and investment in AM technologies, some fundamental questions and trends about the dependencies existing in these avenues need highlighting. The goal of our review paper is to organize this body of knowledge surrounding AM, and present current barriers, findings, and future trends significantly to the researchers. We also discuss fundamental attributes of AM processes, evolution of the AM industry, and the affordances enabled by the emergence of AM in a variety of areas such as geometry processing, material design, and education. We conclude our paper by pointing out future directions such as the "print-it-all" paradigm, that have the potential to re-imagine current research and spawn completely new avenues for exploration. The fundamental attributes and challenges/barriers of Additive Manufacturing (AM).The evolution of research on AM with a focus on engineering capabilities.The affordances enabled by AM such as geometry, material and tools design.The developments in industry, intellectual property, and education-related aspects.The important future trends of AM technologies.
1,792 citations
TL;DR: Contour crafting (CC) is a recent layered fabrication technology that has a great potential in automated construction of whole structures as well as subcomponents and will most probably be one of the very few feasible approaches for building structures on other planets, such as Moon and Mars.
784 citations
TL;DR: A direct transcription method is presented that reduces finding the globally optimal trajectory to solving a second-order cone program using robust numerical algorithms that are freely available.
Abstract: This paper focuses on time-optimal path tracking, a subproblem in time-optimal motion planning of robot systems. Through a nonlinear change of variables, the time-optimal path tracking problem is transformed here into a convex optimal control problem with a single state. Various convexity-preserving extension are introduced, resulting in a versatile approach for optimal path tracking. A direct transcription method is presented that reduces finding the globally optimal trajectory to solving a second-order cone program using robust numerical algorithms that are freely available. Validation against known examples and application to a more complex example illustrate the versatility and practicality of the new method.
451 citations
TL;DR: In this paper, the authors reviewed various slicing approaches developed for tessellated as well as actual CAD models for laminated manufacturing and compared them with real CAD models with different slice thickness.
Abstract: Layered manufacturing (LM) or rapid prototyping is a process in which a part is produced using layer‐by‐layer addition of the material. In LM, slicing of the CAD model of a part to be produced is one of the important steps. Slicing of CAD model with a very small slice thickness leads to large build time. At the same time if large slice thickness is chosen, the surface finish is very bad due to staircasing. These two contradicting issues namely reduction in build time and better surface quality have been a major concern in laminated manufacturing. This contradiction has led to the development of number of slicing procedures. The present paper reviews various slicing approaches developed for tessellated as well as actual CAD models.
350 citations