Additive Manufacturing Capabilities Research Articles

Multiscale Study on Effect of Humidity on Shape Memory Polymers Used in Three-Dimensional Printing

Abstract Shape memory polymers (SMP) are used in the three-dimensional (3D) printing field for different applications such as soft robotics or medical devices. Although this technology has expanded the capabilities of additive manufacturing, there still exists fundamental questions regarding the optimum condition for manufacturing these 3D-printed parts. Various factors play a crucial role in the final quality of printed parts, such as deposition orientation, percentage infill, or environmental conditions. In this paper, we study the effect of humidity on commercially available shape memory polymers (SMPs) (NinjaFlex©) at both micro- and macroscale. By performing a 3D computational fluid dynamic model for the printing environment, it is found there are significant temperature and humidity fluctuations around the hot-end and printing bed. Macroscale characterization through ASTM D638 tensile testing shows that for humidity levels higher than 60%, there is a 5–10% reduction in the strength of the material (ultimate strength and tangent modulus). This study is verified by microscale characterization performed with atomic force microscopy on thin films. It is shown that in addition to the effect of humidity on the stiffness of materials, there is an effect on the loss moduli of the matter as well. As humidity increases, these polymers become more viscoelastic. Simultaneously, it is shown higher humidity levels cause increased micro-level surface roughness, which can be the cause for the strength reduction for higher humidities.

Favoring Complexity: A Mixed Methods Exploration of Factors That Influence Concept Selection When Designing for Additive Manufacturing

Abstract The capabilities of additive manufacturing (AM) open up designers’ solution space and enable them to build designs previously impossible through traditional manufacturing (TM). To leverage this design freedom, designers must emphasize opportunistic design for AM (DfAM), i.e., design techniques that leverage AM capabilities. Additionally, designers must also emphasize restrictive DfAM, i.e., design considerations that account for AM limitations, to ensure that their designs can be successfully built. Therefore, designers must adopt a “dual” design mindset—emphasizing both, opportunistic and restrictive DfAM—when designing for AM. However, to leverage AM capabilities, designers must not only generate creative ideas for AM but also select these creative ideas during the concept selection stage. Design educators must specifically emphasize selecting creative ideas in DfAM, as ideas perceived as infeasible through the traditional design for manufacturing lens may now be feasible with AM. This emphasis could prevent creative but feasible ideas from being discarded due to their perceived infeasibility. While several studies have discussed the role of DfAM in encouraging creative idea generation, there is a need to investigate concept selection in DfAM. In this paper, we investigated the effects of four variations in DfAM education: (1) restrictive, (2) opportunistic, (3) restrictive followed by opportunistic (R-O), and (4) opportunistic followed by restrictive (O-R), on students’ concept selection process. We compared the creativity of the concepts generated by students to the creativity of the concepts they selected. The creativity of designs was measured on four dimensions: (1) uniqueness, (2) usefulness, (3) technical goodness, and (4) overall creativity. We also performed qualitative analyses to gain insight into the rationale provided by students when making their design decisions. From the results, we see that only teams from the restrictive and dual O-R groups selected ideas of higher uniqueness and overall creativity. In contrast, teams from the dual R-O DfAM group selected ideas of lower uniqueness compared with the mean uniqueness of ideas generated. Finally, we see that students trained in opportunistic DfAM emphasized minimizing build material the most, whereas those trained only in restrictive DfAM emphasized minimizing build time. These results highlight the need for DfAM education to encourage AM designers to not just generate creative ideas but also have the courage to select them for the next stage of design.

Candidate Core Designs for the Transformational Challenge Reactor

Early cycle activities under the Transformational Challenge Reactor (TCR) program focused on analyzing and maturing four reactor core design concepts: two fast-spectrum systems and two thermal-spectrum systems. A rapid, iterative approach has been implemented through which designs can be modified and analyzed and subcomponents can be manufactured in parallel over time frames of weeks rather than months or years. To meet key program initiatives (e.g., timeline, material use), several constraints—including fissile material availability (less than 250 kg of HALEU), component availabilities, materials compatibility, and additive manufacturing capabilities—were factored into the design effort, yielding small (less than one cubic meter in volume) cores with near-term viability. The fast-spectrum designs did not meet the fissile material constraint, so the thermal-spectrum systems became the primary design focus. Since significant progress has been made on advanced moderator materials (YHx) under the TCR program, gas-cooled thermal-spectrum systems using less than 250 kg of HALEU that occupy less than 1 m3 are now feasible. The designs for two of these systems have been evolved and matured. In both thermal-spectrum design concepts, bidirectional coolant flow is used. Coolant flows down through YHx moderator elements and is reversed in a bottom manifold and core support structure, and then flows up though or around the fuel elements. The main difference between the two thermal-spectrum design concepts is the fuel elements—one uses traditional UO2 ceramic fuel, and the other uses UN-bearing TRISO fuel particles embedded inside a SiC matrix. Core neutronics and thermal performance for these systems are assessed and summarized herein.

A constructive solid geometry-based generative design method for additive manufacturing

The unique capability of additive manufacturing (AM) to deal with complex geometries drives the traditional topological optimization and lightweight design to a new paradigm. However, AM constraints are still hard to integrate into the optimization procedure, and the multiple conflict design objectives are difficult to handle when making decisions. In addition, the computation cost is usually high. To solve these problems, this paper proposes a new generative design method with a manufacturing validation so that the designer’s decision-making is more efficient. This method first uses a CSG (constructive solid geometry)-based technique to generate and represent topology geometries with smooth boundaries and parametric control. Then, a genetic algorithm is used to operate the CSG geometries in order to search for optimal solutions. Finally, a set of finite optimal non-dominated design solutions on the Pareto front are located and presented for the designer’s further decision making. The proposed method can generate a large quantity of qualified optimal alternative solutions with smooth geometric boundaries but the computation cost is less. It is promising to design qualified solutions, especially for lightweight structure design, in AM. Several demonstration examples and comparison case studies with existing methods in literature are presented at the end of this paper to show the advantages.

A Tuneable, Photocurable, Poly(Caprolactone)-Based Resin for Tissue Engineering-Synthesis, Characterisation and Use in Stereolithography.

Stereolithography is a useful additive manufacturing technique for the production of scaffolds for tissue engineering. Here we present a tuneable, easy-to-manufacture, photocurable resin for use in stereolithography, based on the widely used biomaterial, poly(caprolactone) (PCL). PCL triol was methacrylated to varying degrees and mixed with photoinitiator to produce a photocurable prepolymer resin, which cured under UV light to produce a cytocompatible material. This study demonstrates that poly(caprolactone) methacrylate (PCLMA) can be produced with a range of mechanical properties and degradation rates. By increasing the degree of methacrylation (DM) of the prepolymer, the Young’s modulus of the crosslinked PCLMA could be varied from 0.12–3.51 MPa. The accelerated degradation rate was also reduced from complete degradation in 17 days to non-significant degradation in 21 days. The additive manufacturing capabilities of the resin were demonstrated by the production of a variety of different 3D structures using micro-stereolithography. Here, β-carotene was used as a novel, cytocompatible photoabsorber and enabled the production of complex geometries by giving control over cure depth. The PCLMA presented here offers an attractive, tuneable biomaterial for the production of tissue engineering scaffolds for a wide range of applications.

Novel polymer materials systems to expand the capabilities of FDM™-type additive manufacturing

The work presented here describes the efforts conducted in the past decade by the Polymer Extrusion Lab at The University of Texas at El Paso in the area of novel materials development for fused deposition modeling (FDM™)-type additive manufacturing platforms. We discuss efforts in the development of application-specific materials systems as well as the development of materials whose physical properties can be enhanced by FDM™-type processing. Additional efforts in the area of hybrid composite materials, sustainable materials, and shape-memory polymers are discussed. Aspects related to materials characterization are also highlighted.

Of Narrow Windows and Acrobats: COVID-Responsiveness and Knock-Ons via Additive Manufacturing Capabilities

This research investigates the institutional factors that have driven firms equipped with additive manufacturing (AM) capabilities to repurpose those capabilities as part of the COVID-19 pandemic response. We also examine factors that affected the response outcomes as well as the overall lessons learned from engaging in the pandemic response. Critically, in each of these considerations, we seek to understand the role played by specific AM design capabilities. To answer these questions, we adopted an inductive theory building approach, leveraging a two-wave multiple case study design, to study the research questions. Our rich examination of 33 cases, each entailing interviews with multiple representatives conducted both in the Spring and late Fall of 2020, reveals that core/COVID-19 product similarities and regulatory familiarity are important drivers of participation, along with the unambiguous presence of demand pressure. High usage of generative design (GD), a category of computational technologies enabling novel and optimized design options, appears to compensate for lower levels in part similarity and regulatory familiarity. Firms making COVID-19-related parts, particularly those with extensive GD experience, also report the value of both AM agility and supply chain partners much more frequently than firms that did not participate and are far less likely to cite revelations of inventory risk during the pandemic. Taken together, our study informs both research and practice regarding the potential for GD experience to facilitate resource pivoting during pandemics and related crises, as well as its spillover effects regarding broader experiential learning.

Analysis of Potential Materials for Local Production Using Additive Manufacturing. A Case for the Rail Industry

In the rail industry, unavailability of spare parts can have negative implications such as downtime and financial losses. Long lead times can be experienced in the process of replacing a broken spare part. Some of the parts are expensive to produce in-house because of the tooling costs. It can be time consuming to wait for suppliers to replace the part especially if the part is not produced locally. Proper maintenance of vehicles requires spare parts to be available timeously. The use of Additive Manufacturing (AM) to print spare parts on demand is a quicker and flexible approach when compared to conventional manufacturing methods. The aim of this study is to investigate the material application of Wire Arc Additive Manufacturing (WAAM) in the local production of a typical rail part. Taking advantage of the flexibility offered by the WAAM process, three alternative high performance materials. are considered to reduce the weight, improve functional performance and service life of the part. The performance of all the three materials are tested and analysed using the FEM software. The results of this study are useful in providing guidance on the development of a suitable AM based process chain for producing the part. This demonstrates the capability of AM as a suitable approach for enabling local sustainable production of spare parts for the rail industry.

Characterisation of powder and microstructure, density and surface roughness for additively manufactured stent using medical grade ASTM F75 cobalt chromium (CoCrMo) by selective laser melting (SLM) technology

ABSTRACT This paper explains and demonstrates the capabilities of Metal Additive Manufacturing (MAM) technology in producing intricate stent structure with a customise design by using ASTM F75 Cobalt-Chromium (CoCrMo) powder. Current commercialise stent in the market is rigid in size and geometries and the cost of tooling and manufacturability are increased once the other stent production is replaced. The design, process parameter, powder characterisation, part density and microstructure were investigated and thus exploring the potential area of MAM process for future proof stent manufacturing. Average density achieved for the seven (7) additive-manufactured stents was within 92– 97%, whereas the shrinkage is in between 0.31% and 0.61% (diameter) and 0.03–0.05% (height) respectively. The average surface roughness achieved are 4.1 µm (highest peak) whereas the lowest peak was 365.1 nm. The suggested model of the stent was taken from the third-party vendor and fabrication was carried out using EOSINT M280 metal printer with the aid of Materialise Magics 19.0 software for support generation.

Sensitivity of Micromilling Responses to Grain Variations in Wire Arc Additively Manufactured Aluminum Alloy 4043

Abstract Given the recent trend toward hybrid processing involving the integration of wire arc additive manufacturing (WAAM) and machining capabilities, this paper aims to identify and correlate microstructural variations observed in wire arc additively manufactured aluminum alloy 4043 workpieces to their specific micromilling responses. This is done with the explicit goal of assessing the feasibility of using micromilling responses to detect microstructural variations in WAAM workpieces. As part of this effort, variations in the interlayer cooling time are used to induce changes in the microstructure of a thin-wall WAAM workpiece. The microstructures are first characterized using in-process thermographic imaging, optical microscopy, polarized light microscopy, and indentation. Micromilling slotting experiments are then conducted on different regions within the workpiece. The findings suggest that cutting force signals are the premier candidate for in situ extraction of information regarding microstructural variations within WAAM workpieces. In particular, in situ analysis of the cutting force frequency spectrum can provide critical information regarding dominant failure mechanisms related to the underlying microstructure. Other key micromilling responses such as surface roughness, burr formation, and tool wear also correlate well with the underlying microstructural variations. While these early stage findings hold promise, future research efforts spanning multiple metal alloys systems and micromachining processes are needed to mature the proposed concept.

New Feedstock System for Fused Filament Fabrication of Sintered Alumina Parts.

Only a few 3D-printing techniques are able to process ceramic materials and exploit successfully the capabilities of additive manufacturing of sintered ceramic parts. In this work, a new two component binder system, consisting of polyethyleneglycol and polyvinylbutyral, as well stearic acid as surfactant, was filled with submicron sized alumina up to 55 vol.% and used in fused filament fabrication (FFF) for the first time. The whole process chain, as established in powder injection molding of ceramic parts, starting with material selection, compounding, measurement of shear rate and temperature dependent flow behavior, filament fabrication, as well as FFF printing. A combination of solvent pre-debinding with thermal debinding and sintering at a reduced maximum temperature due to the submicron sized alumina and the related enhanced sinter activity, enabled the realization of alumina parts with complex shape and sinter densities around 98 % Th. Finally the overall shrinkage of the printed parts were compared with similar ones obtained by micro ceramic injection molding.

Metal Additive Manufacturing: Considering the Relationship Between Alloy and Application

Abstract Case studies from a range of industries illustrate how advanced additive manufacturing capabilities optimize both material performance and value. The materials discussed are Inconel 718, Ti-6Al-4V, aluminum F357, and Hastelloy X.

Additive creativity: investigating the use of design for additive manufacturing to encourage creativity in the engineering design industry

ABSTRACT The capabilities of additive manufacturing (AM) enable designers to generate and build creative solutions beyond the limitations of traditional manufacturing. However, designers must also accommodate AM limitations to minimize build failures. Several researchers have proposed design tools and educational interventions for integrating design for AM (DfAM) in engineering design. However, there is a need to investigate the effect of DfAM training on industry professionals’ use of these techniques and its subsequent effects on the creativity of their designs. In this paper, we present a workshop-based study in which industry professionals were sequentially introduced to opportunistic and restrictive DfAM. Participants were also given a DfAM task, with short idea generation sessions conducted between each content lecture. The participants’ designs and their DfAM and creative self-efficacies were compared from before to after receiving DfAM training. The results show that DfAM training successfully increased participants’ restrictive DfAM self-efficacy; however, no changes were seen in their opportunistic DfAM or creative self-efficacies. Further, the results show an increase in the uniqueness and overall creativity of the participants’ designs, but no significant changes were seen in the initially high usefulness of the designs. These findings suggest that DfAM training presents an opportunity to encourage creative idea generation.

A legend reborn: Additive manufacturing creates Wootz-Damascus steel

Artisans in ancient India melted iron with woodchips as sources of carbon in clay crucibles and produced a hypereutectoid steel (C content ∼1.5% by weight) called Wootz steel. Their technique, perfected over centuries, resulted in steels of high strength and ductility. These steels were traded in Damascus and spread to many countries, which turned them into swords of amazing performance with aesthetically pleasing wavy patterns on the surface. Combining the expertise of researchers at the Max Planck Institute for Iron Research in alloy design with that in laser processing by a team at the Fraunhofer Institute for Laser Technology, a new Damascus-like steel has now been created by additive manufacturing (AM), commonly known as three-dimensional (3D) printing. The key to the success of this work, as reported in a recent issue of Nature (doi:10.1038/s41586-020-2409-3), is the innovative use of the digital capabilities of AM to introduce a controlled hierarchical structure without the need for post-treatment.

Transformational Challenge Reactor preconceptual core design studies

In the nuclear industry, a manufacturing-informed design approach has the potential to yield the most benefit from advanced manufacturing. By leveraging advanced materials, data science, and rapid testing and deployment, manufacturing-informed design can drive down costs and development times, ultimately improving future commercial viability. This approach is being demonstrated in the US Department of Energy Office of Nuclear Energy (DOE-NE) Transformational Challenge Reactor (TCR) program. Preconceptual design activities for TCR have been focused on analyzing and maturing four reactor core design concepts: two fast-spectrum and two thermal-spectrum systems. The designs were iteratively modified and analyzed, and subcomponents were manufactured in parallel over weeks instead of months or years. To meet key program initiatives (e.g., timeline and material use), several constraints—including fissile material availability, component availability, materials compatibility, and additive manufacturing capabilities—were factored into the design effort, yielding small cores less than one cubic meter in volume with near-term viability.The TCR program has made significant progress on development of advanced moderator materials such as yttrium hydride, advancing the feasibility of gas-cooled thermal spectrum systems using less than 250 kg of high-assay low enriched uranium (HALEU) and occupying less than 1 m3. Each of the two resulting thermal designs uses a different fuel form: traditional UO2 ceramic fuel and tristructural isotropic (advanced TRISO) fuel particles embedded inside a SiC matrix. Core neutronics and thermal performance for these systems were assessed and summarized. Evaluation of the performance metrics for these two moderated designs has yielded the downselected TCR design: a TRISO-fueled and yttrium hydride moderated gas-cooled reactor.

3D printed deformable sensors.

The ability to directly print compliant biomedical devices on live human organs could benefit patient monitoring and wound treatment, which requires the 3D printer to adapt to the various deformations of the biological surface. We developed an in situ 3D printing system that estimates the motion and deformation of the target surface to adapt the toolpath in real time. With this printing system, a hydrogel-based sensor was printed on a porcine lung under respiration-induced deformation. The sensor was compliant to the tissue surface and provided continuous spatial mapping of deformation via electrical impedance tomography. This adaptive 3D printing approach may enhance robot-assisted medical treatments with additive manufacturing capabilities, enabling autonomous and direct printing of wearable electronics and biological materials on and inside the human body.

Characterisation of elemental analysis, carbon sulphur analysis and impact test of stent manufacturing using medical grade ASTM F75 cobalt chromium (CoCrMo) by selective laser melting (SLM) technology

ABSTRACT This paper explains and demonstrates the capabilities of metal additive manufacturing (MAM) technology in producing intricate stent structure with a customise design by using ASTM F75 cobalt chromium powder. The elemental analysis (EDX-SEM), carbon sulphur analysis and Impact Test are being develop and tested and thus exploring the potential area of MAM process for future proof stent manufacturing. By alternatively switching to MAM, the step of production can be minimised and thus customisation of stent can be carried out according to the patient’s need. The suggested model of the stent was taken from the third-party vendor and fabrication was carried out using EOSINT M280 metal printer with the aid of Materialise Magics 19.0 software for support generation.

In Situ Nanocomposite Fabrication for RF Electronics Applications With Additive Manufacturing

Using additive manufacturing (AM), in this article, we show the dynamic mixing of polymer ceramic composite materials during the 3-D printing process. Using this in situ mixing strategy, we print polyimide and barium titanate (BaTiO 3) nanocomposite films with variable levels of ceramic loading. This is accomplished with multimaterial aerosol jet printing. The relative dielectric constant and loss tangent of these composite materials are characterized using two ring resonator circuits designed for the first resonance below 12 and 110 GHz, respectively. This yields material characterization results from the X-band to the W-band. We use these results to estimate the ceramic loading by volume in the composites. In addition, we use scanning electron microscopy and energy-dispersive X-ray spectroscopy to characterize the dispersion and ceramic loading of the composite films. Using this process, we demonstrate a range of relative dielectric constants from 3.1 to 8.9. To demonstrate the capabilities of this process, a continuous gradient of material is also shown in a printed film. Finally, we demonstrate a slightly modified process in order to lower the loss characteristics of the printed films to provide insight into the loss mechanisms. By mixing composites in situ, we are able to dynamically alter the ceramic loading of the printed material without formulating multiple inks and pattern 3-D structures without the use of photosensitive materials. This allows us to manufacture material gradients and patterns that would otherwise be impractical to fabricate using conventional microfabrication. Using composite mixing in place adds a new dimension to the flexibility and capability of AM.

SUPPORTING ADDITIVE MANUFACTURING TECHNOLOGY DEVELOPMENT THROUGH CONSTRAINT MODELLING IN EARLY CONCEPTUAL DESIGN: A SATELLITE PROPULSION CASE STUDY

AbstractFunction and constraints modelling are implemented to design two gridded ion thrusters for additive manufacturing (AM). One concept takes advantage of AM design freedom, disregarding AM limitations and is not feasible. The other concept considers AM limitations and is manufacturable and feasible. Constraints modelling highlights AM capabilities that can be improved, showing where future investment is needed. Constraints representation can also support the creation of technology development roadmaps able to identify areas of AM technologies that must be improved.

Design, fabrication and validation of an improved coil for induction dilatometry

Dilatometry is a versatile tool to investigate thermal expansion or phase transformations in various materials based on the length changes upon heating and cooling. Since most modern thermal processes tend to take place at high heating and cooling rates it can be demonstrated that a large longitudinal temperature gradient within dilatometric samples impedes the accurate investigation of physical mechanisms. In this study we investigate how an instrumental advancement of the induction heating system can be implemented in a dilatometric setup in order to mitigate the temperature gradient and its effect on the measured length change for a wide range of heating rates. For this purpose a numerical method for heating design optimization using a FEM simulation of the dilatometric experiment is developed and validated. The presented heating component design method in combination with additive manufacturing capabilities allows for a more accurate and flexible method of detecting dilatation in a dilatometric setup. Extreme temperature differences of 140∘C for a maximum heating rate of 800∘C/s could be reduced by 15-45% within the sample using new optimized instrumentation. This leads to a more profound and exact interpretation of dilatometric data for high heating rates and complex time temperature profiles.