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With the emergence of modern technologies in manufacturing processes, companies need to adapt themselves to these technologies to stay competitive. Additive Manufacturing is one of the upcoming technologies which will bring major changes to the manufacturing process. AM (Additive Manufacturing) offers flexibility in design, production size, customization, etc., Even though there are numerous advantages from the implementation of AM technologies less than 2% of the manufacturing industries use them for production. The purpose of the thesis was to study the impact of AM on manufacturing industries in 5-10 years and the barriers it is facing for widespread diffusion. Additionally, its impact on Sustainability aspects is also studied. A literature review was conducted to understand the current AM processes, their applications in different manufacturing sectors, their impact on business strategies, operations, and Product Life cycle. From the study, it was concluded that AM technologies are still in their maturing state and has a lot of uncertainties that it must overcome. The most notable barriers being implementation costs, limited materials, and protection of Intellectual property. The thesis also presents the projection for AM in 2030. AM is advantageous for Environmental and Economic sustainability with very little research on Societal sustainability.

Wire and arc additive manufacturing (WAAM) is a manufacturing method using a numerical controlled motion system and a welding system to additively manufacture three dimensional components. The motion system is programmed from three dimensional computer aided design model data (3D-CAD) of the intended geometry which is then sliced in to layers and welded on additively. There are seven process categories within additive manufacturing (AM), each with their own benefits and drawbacks. One of these process categories is directed energy deposition (DED) which uses an energy source to melt material onto a build plate. Instead of filling the build plate with material and selectively melting or sintering the material, DED only deposit material which is to be melted. WAAM is a process within the DED process category. BAE Systems Hägglunds manufactures relatively large components with requirements for mass reduction. Hägglunds has therefor invested in a WAAM laboratory, for testing and investigation on how to utilize this technology to their advantage. During the master thesis a geometrical correlation between the overhang angle and the material deposition on the edges of the overhangs has been found. A slicing strategy utilising this correlation has proven useful in combatting an issue where the top surface of a parallelepiped ends up unwantedly not parallel to the substrate plate. This master thesis has also increased the capability from 30° to 45° overhang angle. A numeric simulation of cooling times in the WAAM process has been developed. The simulation had a maximum error of one minute or about 69 % longer measured than simulated cooling time at worst case.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24849号 / 工博第5166号 / 新制||工||1987(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 泉井, 一浩, 教授 松原, 厚, 教授 平山, 朋子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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The overall goal of this research work is to enhance the capabilities of large-format, polymer material extrusion, additive manufacturing (AM) systems. Specifically, the aims of this research are to (1) Construct, and develop a robust workflow for, a large-format, robotic, AM system; (2) Develop an algorithm for determining and relaying proper rotation commands for 5 degree of freedom (DoF) multi-axis deposition; and (3) Create a method for printing a removable support material in large-format AM. The development and systems-integration of a large-format, pellet-fed, polymer, material extrusion (ME), AM system that leverages an industrial robotic arm is presented. The robotic arm is used instead of the conventional gantry motion stage due to its multi-axis printing ability, ease of tool changes for multi-material deposition and/or subtraction, and relatively small machine footprint. A novel workflow is presented as a method to control the robotic arm for layer-wise fabrication of parts, and several machine modifications and workflow enhancements are presented to extend the multi-axis manufacturing capabilities of the robot. This workflow utilizes existing AM slicers to simplify the motion path planning for the robotic arm, as well as allowing the workflow to not be restricted to a single robotic deposition system. To enable multi-axis deposition, a method for generating tool orientations and resulting deposition toolpaths from a geometry's STL file was developed for 5-DoF conformal printing and validated via simulation using several different multi-DOF robotic arm platforms. Furthermore, this research proposes a novel method of depositing a secondary sacrificial support material was created for large-format AM to enable the fabrication of complex geometries with overhanging features. This method employs a simple tool change to deposit a secondary, water-soluble polymer at the interfaces between the part and supporting structures. In addition, a means to separate support material into smaller sections to extend the range of geometries able to be manufactured via large-format AM is presented. The resultant method was used to manufacture a geometry that would traditionally be considered unprintable on conventional large-format AM systems. / Master of Science / Additive manufacturing (AM), also known as 3D printing, is a method of manufacturing objects in a layer-by-layer technique. Large-format AM is typically defined as an AM system that can create an object larger than 1 m3. There are only a few manufacturers in the world of these systems, and all currently are built on gantry-based motion stages that only allow movement of the printer in three principal axes (X, Y, Z). The primary goal of this thesis is to construct a large-format AM system that uses a robotic arm to enable printing in any direction or orientation. The use of an industrial robotic arm enables printing in multiple planes, which can be used to print structures without support structures, print onto curved surfaces, and to purt with curved layers which produces a smoother external part surface. The design of the large-format AM system was validated through successful printing of objects as large as 1.0x0.5x1.2 m, simultaneous printing of a sacrificial support material to enable overhanging features, and through completing multi-axis printing. To enable multi-axis printing, an algorithm was developed to determine the proper toolpath location and relative orientation to the part surface. Using a part's STL file as input, the algorithm identifies the normal vector at each movement command, which is then used to calculate the required tool orientation. The tool orientations are then assembled with the movement commands to complete the multi-axis toolpath for the robot to perform. Finally, this research presents a method of using a second printing tool to deposit a secondary, water-soluble material to act as supporting structures for overhanging and bridging part features. While typical 3D printers can generally print sacrificial material for supporting overhangs, large-format printers produce layers up to 25 mm wide, rendering any support material impossible to remove without post-process machining. This limits the range of geometries able to be printed to just those with no steep overhangs, or those where the support material is easily reachable by a tool for removal. The solution presented in this work enables the large scale AM processes to create complex geometries.

<p>Extrusion Deposition Additive Manufacturing (EDAM) is a process in which fiber-filled thermoplastic polymers pellets get molten in the extruder and deposited onto a build plate in a layer-by-layer basis. The use of short fiber composite for EDAM has enabled large-scale 3D printing structures and tools for traditional composite manufacturing processes. Successful EDAM production critically depends on the understanding of the process-structure-property relationship. Especially on the bonding between the beads which is of paramount importance in additive manufacturing since it affects primarily the fracture and strength characteristics of the printed part. Bonding is influenced mainly by the temperature history and the contact between the beads. Both of which is dependent on the fiber orientation within the bead induced by the flow deformation that occurs according to the printing parameters. This study aims to investigate and model the complex relationship between the printing conditions and inter-bead bonding in the lateral direction.</p> <p>A framework was developed to facilitate this aim, and it contains a fusion bonding model that couples the time-temperature history and the bead-to-bead contact interface. Four deposition parameters were studied: the nozzle height, ratio of the print velocity to extrudate velocity, bead-to-bead spacing, and layer time. First, a deposition flow model was developed, utilizing the anisotropic viscous flow model and smooth particle hydrodynamic finite element formulation, to predict the fiber orientation state across the deposited bead and the bead-to-bead interface for the given set of deposition parameters. Next, the effect of printing conditions on the temperature history of the bead was discovered by utilizing the heat transfer process simulation in ADDITIVE3D. Third, the experimental characterization procedure for mode I fracture toughness in the lateral direction was developed, and the fracture toughness was characterized using linear elastic fracture mechanics principles. Lastly, the phenomenological model for non-isothermal lateral fusion bonding was characterized using the bead contact interface, temperature history, and fracture toughness properties. This work showed a comprehensive effort in fusion bonding modeling while also presented a valuable process-structure-property-performance relationship in EDAM.  Guidance on the selection of printing conditions and strategy can be made using the developed model to print higher-strength parts.  </p>

Over the 1980’s, the introduction of Additive Manufacturing (AM) technologies has provided alternative methods for the fabrication of complex three-dimensional (3D) synthetic bone tissue implant scaffolds. However, implants are still unable to provide post surgery feedback. Implants often loosen due to mismatched mechanical properties of implant material and host bone. The aim of this PhD research is to fabricate an integrated strain gauge that is able to monitor implant strain for diagnosis of the bone healing process. The research work presents a method of fabricating electrical resistance strain gauge sensors using rapid and mask-less process by experimental development (design of experiment) using the nScrypt 3Dn-300 micro dispensing direct write (MDDW) system. Silver and carbon electrical resistance strain gauges were fabricated and characterised. Carbon resistive strain gauges with gauge factor values greater than 16 were measured using a proven cantilever bending arrangement. This represented a seven to eight fold increase in sensitivity over commercial gauges that would be glued to the implant materials. The strain sensor fabrication process was specifically developed for directly fabricating resistive strain sensor structures on synthetic bone implant surface (ceramic and titanium) without the use of glue and to provide feedback for medical diagnosis. The reported novel approach employed a biocompatible parylene C as a dielectric layer between the electric conductive titanium and the strain gauge. Work also showed that parylene C could be used as an encapsulation material over strain gauges fabricated on ceramic without modifying the performance of the strain gauge. It was found that the strain gauges fabricated on titanium had a gauge factor of 10.0±0.7 with a near linear response to a maximum of 200 micro strain applied. In addition, the encapsulated ceramic strain gauge produced a gauge factor of 9.8±0.6. Both reported strain gauges had a much greater sensitivity than that of standard commercially available resistive strain gauges.

Cellular metals exhibit combinations of mechanical, thermal and acoustic properties that provide opportunities for various implementations and applications; light weight aerospace and automobile structures, impact and noise absorption, heat dissipation, and heat exchange. Engineered cell topologies enable one to control mechanical, thermal, and acoustic properties of the gross cell structures. A possible way to manufacture complex 3D metallic cellular solids for mass production with a relatively low cost, the investment casting (IC) method may be used by combining the rapid prototyping (RP) of wax or injection molding. In spite of its potential to produce mass products of various 3D cellular metals, the method is known to have significant casting porosity as a consequence of the complex cellular topology which makes continuous fluid's access to the solidification interface difficult. The effects of temperature on the viscosity of the fluids were studied. A comparative cost analysis between AM-IC and additive manufacturing methods is carried out. In order to manufacture 3D cellular metals with various topologies for multi-functional applications, the casting porosity should be resolved. In this study, the relations between casting porosity and processing conditions of molten metals while interconnecting with complex cellular geometries are investigated. Temperature, and pressure conditions on the rapid prototyping – investment casting (RP-IC) method are reported, thermal stresses induced are also studied. The manufactured samples are compared with those made by additive manufacturing methods.