Additive Manufacturing (AM), commonly known as 3D printing, represents manufacturing technology that creates objects layer by layer based on 3D model data. AM technologies have capabilities that provide engineers with new design opportunities outside the constraints of traditional subtractive manufacturing. These capabilities of AM have made it attractive for manufacturing components in the space industry., where parts are often bespoke and complex. In particular, Laser Powder Bed Fusion (LPBF) has attracted attention due to its ability to produce components with the part properties required for space applications. Additionally, the precision of the laser enables the production of innovative near-net shape and low-weight part designs.  However, due to the powdered metal material, the LPBF process is categorised with rough surfaces in the as-built state. The extent and effect of surface roughness are closely linked to geometrical design variables, including build orientation, overhangs, support structure, and build parameters; hence the more intricate the design, the more difficult the removal of this roughness. Consequently, the as-built surface for most applications is too rough and could adversely affect proprieties, i.e., fatigue. Hence, practical Design for AM (DfAM) supports should be developed that understand how design factors, such as surface roughness, will impact a part’s performance. This thesis therefore presents literature reviews on research related to LPBF surface roughness and design support, exploring the trends in managing surface roughness and investigations on the characteristics of design support. Additionally, through a space industry case study, a proposed process involving additive manufacturing design artefacts (AMDAs) is considered to investigate and describe the relationship between design, surface roughness, and performance. The review found that, in general, research focuses on the relationship between surface roughness and LPBF build parameters, material properties, or post-processing. There is very little support for design engineers to consider how surface roughness from an AM process affects the final product (less than 1% of the review articles). In investigating surface roughness, the AMDA process identified characteristics that impact roughness levels and geometric adherence to part design. Additionally, twelve characteristics of design support were identified and considered to review the AMDA process. The process aided the evaluation of design uncertainties and provided indications of part performance. However, iterations of the process can be required to clarify product-specific design uncertainties. Though, the designer obtains a better understanding of their design and the AM process with each iteration. The inclusion of the requirement to set evaluation criteria for artefacts was recommended to develop the AMDA process as design support.

<p>  </p> <p>This thesis is motivated by the author’s observation that no systematic methodology is available to characterize and model mechanical behaviors of 3D printed parts in terms of their elastic modulus and critical loading capacities. Note that the more controlled and steadier printing process is, the easier the mechanical properties parts can be predicted. This research focuses on the methods for the prediction and validation of mechanical properties of 3D printed parts, and the focus is the responses of the printed parts subjected to tensile loads. The mathematic models are derived to characterize the mechanical properties of a part along three principal directions, and the models are validated experimentally by following the American Society for Testing and Materials (ASTM) D638 testing standards. It is assumed that a unidirectional plane stress occurs to each lamina to (1) simplify a compliance matrix with a size 3 by 3 and (2) characterize the mechanical properties by the elastic modules and strengths in three principal directions. Two mathematical models are developed using the experimental data from the classical laminate theory and finite element analysis (FEA) by the SolidWorks. Both of the developed models are used to predict the ultimate tensile strength and Young’s modulus of the specimens that are printed by setting different raster angles on different layers. This thesis work aims to (1) gain a better understanding of the impact of printing parameters on the strengths of printed parts and (2) explore the feasibility of using the classical laminate theory to predict the mechanical properties of the parts printed with different raster angles and patterns. To validate the proposed mathematic models, parts by FDM are tested by following the ASTM testing standards; moreover, it testifies if the selected ASTM-D638 is suitable to test 3D printed parts by FDM. </p>

This thesis investigates the differences in the design process when developing a product for additive manufacturing (AM) compared to traditional manufacturing methods, such as CNC machining. In recent years, additive manufacturing (AM), including metal-based laser powder bed fusion (L-PBF), has gained popularity, leading to increased adoption by companies. The design process for AM, particularly in the context of metals, differs compared to for traditional manufacturing methods. L-PBF, being a method based on highly concentrated laser beam fusion, offers a higher level of design freedom, enabling the creation of intricate shapes, internal structures, and varying wall thicknesses. In contrast, traditional manufacturing methods based on subtractive processes impose limitations on design possibilities due to tooling and machining constraints. Adapting to L-PBF requires designers to reconsider, re-think and redesign parts specifically for AM, taking into account factors suchas cost, knowledge requirements and build volume limitations. The application of L-PBF extends to various industries, including aerospace and performance automobiles. Designing for L-PBF opens up new possibilities for product development by leveraging the advantages of AM, such as design flexibility and topology optimization. Topology optimization allows for the creation of lightweight components while maintaining structural integrity. However, transitioning from traditional manufacturing to L-PBF presents challenges, requiring designers to navigate the unique considerations and constraints associated with AM. This research aims to enhance the understanding of the design process for AM, with a specific focus on L-PBF, and its implications for product development. By exploring the differences between AM and traditional manufacturing methods, this study contributes to the broader adoption and effective implementation of AM technologies in various manufacturing sectors. / Detta arbete undersöker skillnaderna i designprocessen vid utveckling av produkter för additive manufacturing (AM) jämfört med traditionella tillverkningsmetoder, såsom CNC bearbetning. På senare år har additiv tillverkning (AM), inklusive Laser Powder Bed Fusion (L-PBF), blivit populärt och allt fler företag använder sig av tekniken. Designprocessen för AM, skiljer sig jämnfört med för traditionella tillverkningsmetoder. L-PBF erbjuder en hög grad av designfrihet och möjliggör avancerade former, interna strukturer och varierande väggtjocklekar. I kontrast begränsar traditionella tillverkningsmetoder, som bygger på subtraktiva processer, designmöjligheterna på grund av verktygs- och bearbetningsbegränsningar. Att anpassa sig till L-PBF kräver att designers omprövar och omdesignar delar specifikt för AM och tar hänsyn till faktorer som kostnad, kunskapskrav och begränsningar i byggvolymen. Användningen av L-PBF sträcker sig till olika branscher, inklusive luft- och rymdindustrin samt prestandabilar. Att designa för L-PBF öppnar upp nya möjligheter för produktutveckling genom att utnyttja fördelarna med AM, såsom designflexibilitet och topologioptimering. Topologioptimering möjliggör skapandet av lätta komponenter samtidigt som den strukturella integriteten bibehålls. Övergången från traditionell tillverkning till L-PBF innebär dock utmaningar och kräver att designers hanterar de unika övervägandena och begränsningarna som är förknippade med AM. Denna forskning syftar till att förbättra förståelsen för designprocessen för AM, med särskilt fokus på L-PBF, och dess implikationer för produktutveckling. Genom att utforska skillnaderna mellan AM och traditionella tillverkningsmetoder bidrar denna studie till en bredare användning och effektiv implementering av AM-teknologier inom olika tillverkningssektorer.

<p>    An all-additive manufacturing technique was developed to print piezoelectrically active polymeric materials, primarily poly(vinylidene fluoride) (PVdF), for use in pressure sensors in soft robotics. The research proceeded in three stages. The initial stage used Fused Deposition Modeling (FDM) and electric poling independently to create piezoelectric PVdF pressure sensors. The second stage merged FDM and electric poling processes. The third stage introduced electrospinning to create flexible, high-output piezoelectric PVdF materials, which were combined with three-dimensional (3D) printed soft structures for stretchable pressure sensors.</p> <p>    The main achievement of the research was the development of the Electric Poling-assisted Additive Manufacturing (EPAM) technique, combining electric poling and FDM 3D printing to print piezoelectric materials with custom structures at lower costs. β-phase in semicrystalline PVdF materials is mainly responsible for piezoelectricity. A higher β-phase content results in superior sensor performance. This technique was evaluated by measuring the piezoelectric output voltage of the printed PVdF films, and β-phase content was quantified using Fourier-transform Infrared spectroscopy (FTIR). The developed EPAM technique was combined with Direct Ink Writing (DIW), becoming a hybrid 3D printing technique. This is the first demonstration of applying a hybrid printing technique to print piezoelectric PVdF-based sensors directly. The sensor was constructed using FDM printed PVdF film as the dielectric sandwiched between two parallel DIW printed silver electrodes. The PVdF sensors have both piezoelectric pressure sensing and capacitive temperature sensing functionalities. The application of the capacitive temperature sensor was demonstrated by applying heating-and-cooling cycles while measuring the capacitance as a function of temperature at a constant frequency, showing improved sensitivities at higher frequencies (i.e., 105 Hz) after dielectric polarization.</p> <p>    The third stage of research was motivated by the need for soft piezoelectric pressure sensors for soft robotics. Challenges were twofold: requiring soft piezoelectric materials with high coefficients for excellent sensors and fabrication techniques to incorporate soft materials into designed structures. Inspired by the EPAM technique, a method combining electrospinning and DIW was used to create soft piezoelectric PVdF/thermal plastic polyurethane (TPU) blend microfiber-based pressure sensors. The soft sensor was integrated with an FDM printed soft structure for a stretchable pressure sensor with both piezoelectric sensing and capacitive sensing mechanisms.</p>

Increasing application of Additive Manufacturing (AM) in industrial production demands product reimagination (assemblies, subsystems) from an AM standpoint. Simulation driven design tools play an important part in achieving this with design optimization subject to the capabilities of AM technologies. Therefore, the bus frames department (RBRF) in Scania CV AB, Södertälje wanted to examine the synergies between topology optimization and Design for AM (DfAM) in the context of this thesis. In this thesis, a methodology is developed to establish a DfAM framework involving topology optimization and is accompanied by a manufacturability analysis stage. A case study implementation of this developed methodology is performed for validation and further development. The case study replaces an existing load bearing cross member with a new structure optimized with respect to weight and manufacturing process. It resulted in a nearly self supporting AM friendly design with improved stiffness along with a 9.5% weight reduction, thereby proving the benefit of incorporating topology optimization and AM design fundamentals during the early design phase. / Ökad användning av Additive Manufacturing (AM) i industriell produktion kräver ett nytänkade av produkter (enheter, delsystem) ur AM-synvinkel. Simuleringsdrivna designverktyg spelar en viktig roll för att nå detta med designoptimering med hänsyn taget till AM-teknikens möjligheter. Därför ville bussramavdelningen (RBRF) på Scania CV AB, Södertälje undersöka synergierna mellan topologioptimering och Design för AM (DfAM) i detta examensarbete. I examensarbetet utvecklas en metodik för att skapa en DfAM-ramverk som involverar topologioptimering och åtföljs av ett tillverkningsanalyssteg. En fallstudieimplementering av denna utvecklade metodik utförs för validering och fortsatt utveckling. Fallstudien ersätter en befintlig lastbärande tvärbalk med en ny struktur optimerad med avseende på vikt och tillverkningsprocess. Det resulterade i en nästan självbärande AM-vänlig design med förbättrad styvhet tillsammans med en viktminskning på 9,5 %, vilket visar fördelen med att integrera topologioptimering och grundläggande AM-design tidigt i designfasen.

In product manufacturing, assembly approximately represents 50% of the total work hours. Therefore, an efficient and fast assembly system is crucial to get competitive advantages at the global market and have the right product quality. Today, the verification of the assembly system is mostly done by utilizing software based simulation tools even though limitations have been identified. The purpose of this thesis is to identify when the use of additive manufacturing technology could be used in assessing the feasibility of the assembly system design. The research questions were threefold. First, identifying limitations that are connected with the used assembly simulation tools. Secondly, to investigate when additive manufacturing can act as a complement to these assembly simulations. Finally, to develop a framework that will assist the decision makers when to use additive manufacturing as a complement to assembly simulations. The researchers used the method of case study combined with a literature review. The case study collected data from semi-structured interviews, which formed the major portion of the empirical findings. Observations in a final assembly line and the additive manufacturing workshop provided valuable insights into the complexity of assembly systems and additive manufacturing technologies. In addition, document studies of the used visualization software at the case company resulted in an enhanced understanding of the current setting. The case study findings validate the limitations with assembly simulations described in theory. The most frequent ones are related to visibility, positioning, forces needed for the assembly operator, and accessibility between different parts. As both theory and case study findings are consistent in this respect, simulation engineers should be conscious of when to find other methods than simulation for designing the assembly system. One such alternative method is the utilization of additive manufacturing. The thesis outlines a number of situations where additive manufacturing indeed could act as a complement to assembly simulation. The authors argue that the results and findings to a large degree are applicable to other industries as the automotive sector is very global and competitive in nature and encompasses a large variety of complex assembly operations. A structured framework was also developed that could act as a decision support. The framework takes into account three dimensions that are crucial for the decision; (1) the assembly simulation limitation, (2) the context of the assembly and which parts are involved and (3) the possible limitations of additive manufacturing in the specific context. This impartial decision framework could help companies with complex assembly systems to know when to use additive manufacturing, as well as for which parts and subparts additive manufacturing is applicable. To increase the longevity of the decision framework, new improvements of assembly simulation tools and additive manufacturing technologies, respectively, should be incorporated in the framework.

Bone and cartilage constructs are often plagued with mechanical failure, poor nutrient transport, poor tissue ingrowth, and necrosis of embedded cells. However, advances in computer aided design (CAD) and computational modeling enable the design of scaffolds with complex internal michroarchitectures and the a priori prediction of their transport and mechanical properties, such that the design of constructs satisfying the needs of the tissue environment can be optimized. The goal of this research is to investigate the capability of additive manufacturing technologies to create designed microarchitectured tissue engineering scaffolds for bone and cartilage regeneration. This goal will be achieved by pursuing the following two objectives: (1) the manufacture of bioresorbable thermoplastic scaffolds by selective laser sintering (SLS) (2) and the manufacture of hydrogel scaffolds by large area maskless photopolymerization (LAMP). SLS is a laser based additive manufacturing method in which an object is built layer-by-layer by fusing powdered material using a computer-controlled scanning laser. LAMP is a massively parallel ultraviolet curing-based process that can be used to create hydrogels from a photomonomer on a large-scale (558x558mm) while maintaining extremely high feature resolution (20µm). In this research, SLS is used to process polycaprolactone (PCL) and composites of PCL with hydroxyapatite (HA) for bone tissue engineering applications while LAMP is used to process polyethylene glycol diacrylate (PEGDA) which can be used for hard and soft tissue applications.

In current production systems, automation and handling of workpieces is often solved by use of vacuum technology. Most production systems use vacuum ejectors which generate vacuum from compressed air by means of the Venturi effect. However, producing vacuum with compressed air is significantly less efficient than using other principles. To minimize the energy costs of pneumatic vacuum generation or to make full use of the energy available, it is important that the inner contour of the nozzle is shaped precisely to suit the specific application - also the system\'s flow conduction needs to be optimal and the flow losses have to be minimized. This paper presents a method for optimally designing pneumatic vacuum generators and producing them economically even at very low lot sizes in order to keep the operation costs low and address other concerns (such as noise emissions) as well.

Scanning Laser Epitaxy (SLE) is a new laser-based layer-by-layer generative manufacturing technology being developed in the Direct Digital Manufacturing Laboratory at Georgia Tech. SLE allows creation of geometrically complex three-dimensional components with as-desired microstructure through controlled melting and solidification of stationary metal-alloy powder placed on top of like-chemistry substrates. The proposed research seeks to garner knowledge about the fundamental physics of SLE through simulation-based studies and apply this knowledge for hot section turbine component repair and ultimately extend the process capability to enable one-step manufacture of complex gas turbine components. Prior methods of repair specifically for hot-section Ni-base superalloys have shown limited success, failed to consistently maintain epitaxy in the repaired part and suffered from several mechanical and metallurgical defects. The use of a fine focused laser beam, close thermal control and overlapping raster scan pattern allows SLE to perform significantly better on a range of so-called “non-weldable” Ni-base superalloys. The process capability is expanded further through closed-loop feedback control of melt pool temperature using an infra-red thermal camera. The process produces dense, crack-free and epitaxial deposit for single-crystal (SX) (CMSX4), equiaxed (René-80, IN 100) and directionally solidified (DS) (René-142) Ni-based superalloys. However, to enable consistent and repeatable production of defect-free parts and future commercial implementation of the technology several concerns related to process capabilities and fundamental physics need to be addressed. To explore the process capability, the fabricated components are characterized in terms of several geometrical, mechanical and metallurgical parameters. An active-contour based image analysis technique has been developed to obtain several microstructural responses from the optical metallography of sample cross-sections and the process goes through continuous improvement through optimization of the process parameters through subsequent design of experiments. The simulation-based study is aimed at developing a multiphysics model that captures the fundamental physics of the fabrication process and allows the generation of constitutive equations for microstructural transitions and properties. For this purpose, a computational fluid dynamics (CFD) finite-volume solver is used to model the melting and solidification process. The development work also focuses on studying process response to different superalloy materials and implementing a multivariate statistical process control that allows efficient management and optimization of the design parameter space. In contrast to the prior work on single-bead laser scan, the model incorporates the raster scan pattern in SLE and the temperature dependent local property variations. The model is validated through thermal imaging data. The flow-thermal model is further tied to an empirical microstructural model through the active-contour based optical image analysis technique, which enables the identification of several microstructural transitions for laser beam describing a raster scan pattern. The CFD model can effectively be coupled with finite element solver to assess the stress and deformation and can be coupled with meso-scale models (Cellular Automata) to predict different microstructural evolutions. The research thus allows extending the SLE process to different superalloy materials, performs statistical monitoring of the process, and studies the fundamental physics of the process to enable formulation of constitutive relations for use in closed-loop feedback control; thus imparting ground breaking capability to SLE to fabricate superalloy components with as-desired microstructures.

ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV / Functionally testing missiles in the All Up Round (AUR), a configuration that consists of a complete system packaged in its flight worthy state, requires the use of test sets along with constituent conformal equipment for interfacing. During developmental testing, telemetry (TM) sections are integrated within an AUR missile. These test sets monitor TM unit performance while maintaining form, fit, and function; therefore, resulting in complete data confidence. Initiating TM functional tests permit a capability in verifying that TM sections have been integrated properly. Safety being a priority, in order to attenuate RF radiation leakage while providing repeatable test capabilities in the near-field, antenna couplers are fabricated as a shielding interface between the user and radiating source and a coupling interface between an AUR missile and the test set. Generally, antenna couplers are composed of metallic bodies which require machine shop fabrication. The process of getting machined parts can take up to several months which can delay delivery schedules. With the availability of 3D printing capabilities and methods in metalizing various materials, a novel approach to fabricating antenna couplers has been explored. The use of modeling Software Packages (Computer Aided Design and Electromagnetic Solvers) and additive printing play key roles in reducing the development cycle time while saving costs, decreasing weight, and sustaining performance. This paper will detail the efforts using 3D printing capabilities in the development and fabrication of an antenna coupler with several examples cited herein.