Toward pharmaceutical selective laser sintering 3D printing - a thermal and temperature-dependent analysis perspective.

Lithium-ion Batteries Fabricated Entirely with Additive Manufacturing Craig Milroy1,2, Tim Phillips1, Abhimanyu Bhat1,3, David Bourell1, Joseph Beaman1 1Department of Mechanical Engineering, University of Texas, Austin; 2Texas Research Institute, Austin; 3Evonik/Structured Polymers, Inc.There is an immediate need for disruptive battery manufacturing technologies that enable novel architectures and improve energy density by reducing packaging, interconnect, and integration requirements. Most conventional batteries are packaged in rigid metal containers with a restricted range of cell geometries and form factors; this poses major challenges for minimizing footprint and integrating batteries into small spaces. Additive manufacturing (AM) methods fabricate parts layer-by-layer by precisely assembling materials according to digitized instructions, and offer a means for simplified, top-down battery production, which provides enormous freedom to create innovative two-dimensional (2D) and 3D electrode architectural designs, customize battery form factor, and enable on-demand manufacturing. As such, AM offers a paradigm shift in electrochemical device design and manufacturing to accommodate novel geometries, improve energy density, and reduce costs. However, AM is still an emerging field, and while there have been numerous reports describing the use of AM techniques to produce components for batteries and supercapacitors, the vast majority of these efforts have focused on single components (typically the electrodes), rather than on complete systems comprising printed electrodes, separators, and cases.In this presentation, we describe methods to fabricate all necessary components of coin and pouch cells for functional prototype lithium-ion (Li-ion) batteries, using a variety of AM techniques. For example, functional graphite anodes, and cathodes based on nickel-manganese-cobalt oxide (NMC) and lithium iron phosphate (LFP), were fabricated with pneumatic extrusion, screen printing, and selective laser sintering (SLS); polymeric separators were fabricated with SLS; cases/enclosures were fabricated with SLS and direct metal laser sintering (DMLS), and metal components (e.g., foils and tabs) were fabricated with DMLS.We also utilized AM as a rapid-prototyping tool to implement novel component design approaches that improve battery performance, for example:(1) we identified improved electrode configurations by fabricating a wide range of free-standing anodes and cathodes (i.e., electrodes that do not contain or require a metal current collector) using a range of SLS fabrication parameters, then quantified the internal electrode structure/porosity with X-ray computed tomography (XCT) analyses, and used the XCT data to investigate the relationship between AM build parameters and electrochemical performance;(2) we fabricated separators with SLS using a variety of materials (i.e., polypropylene, aluminum oxide, polypropylene-polyethylene copolymer, polyether ether ketone (PEEK), polyester, and blends of these materials). SLS is well-suited to producing porous films, since spherical particles can be lightly melted to create a continuous object with ample void space, minimal membrane thickness, and maximum planar uniformity by preconditioning the printing powders (to prevent clumping), and using a machined build-plate to limit powder depth.The cycle performance of NMC-based cathodes fabricated with extrusion/direct-write and screen-printing was essentially identical to tape-cast (control) cathodes; however, the extrusion-printed cathodes exhibited more pronounced capacity-fade, and there was evidence of electrode-maturation processes, indicating the need for further optimization. The electrochemical performance of LFP-based cathodes fabricated with SLS was found to depend strongly on build setpoints and discharge rate, but exhibited robust extended cycle performance for > 300 cycles.The capacity of graphite-based anodes increased steadily over the first ~20 cycles, and strongly depended on post-SLS processing methods and the charge/discharge rate. We attribute this to the properties of the binder used in the SLS process, and to electrode maturation processes.Printed separators were tested with either tape-cast NMC-based cathodes or additively manufactured anodes/cathodes, and were cycled continuously at rates between C/5 and 2C. Specific capacity was stable and consistent at all rates, and remained above 100 mAh g-1 with no observable capacity fade for any of the rates below 2C. Extended cycling at C/1.5 stable (or even increasing) capacity for approximately 85 cycles, at which point slight capacity fade began.We evaluated the cooperative functionality of printed components (i.e., printed electrodes and separators) in both half-cell and full cell configurations (this work is ongoing). Cells containing an SLS-fabricated separator and a screen-printed NMC cathode charged at C/10 and discharged at C/5 delivered reversible capacity ~160 mAh g-1 for 100 cycles.We will also present ongoing work that uses additive manufacturing to produce flexible batteries and batteries with conformal form-factors. Figure 1

Two types of additive manufacturing (AM) techniques, fused filament fabrication (FFF) and selective laser sintering (SLS), were employed to fabricate specimens from three widely used AM polymers: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyamide (PA): the first two using FFF and PA using SLS. The single‐edge notch bending (SENB) test was employed to measure the mode‐I fracture toughnesses of bulk and AM specimens in three directions relative to the printing direction. Unlike their bulk counterparts, AM polymers exhibited anisotropic fracture toughness. The degree of anisotropy in FFF‐PLA was much larger than FFF‐ABS and SLS‐PA. The smallest fracture toughness value for each AM polymer was achieved along the transverse printing direction. Different AM techniques affect fracture toughness differently. For instance, FFF is shown to increase PLA's plastic deformation, while SLS reduces PA's ductility. The decrease in fracture toughness is consistently observed when transitioning from bulk polymers to AM ones, reaching as much as 75%. This study provides insights into the fracture toughness of AM parts made via popular plastics, which are crucial for designing structural parts using FFF and SLS processes.

Selective Photo-Thermal Conversion of Tungsten Oxide Sol Precursor for Electrochromic Smart Window Applications

With the demand for complex, individualized and functionalized products with respect to constantly decreasing life cycles, additive manufacturing processes such as the process of selective laser sintering (SLS) has increasingly been of industrial interest. These processes are being used more and more to produce models, prototypes and partially finished products made of plastic, metal or ceramic and require neither a tool nor a form. Affected by decreasing installation spaces and increasing functional densities, flexible methods for circuit board application and their combination with additive manufacturing are in the focus of electronic industry research activities. In the context of this article both a thermoplastic polymer polybutylene terephthalate (PBT) which has been prepared to defined powder fractions with cryogenic milling, and the established and commercially available SLS material (PA12, PA2200) were the subject of a dry coating process with LDSadditives. Subsequently, these LDS-powders were processed with SLS to form test specimens. Finally their surface was structured and metallized through the LPKF-LDS-process (Laser-Direct- Structuring). Based on these metallized specimens, the metallization was studied as a function of an LDS-additive filling ratio. To uncover positive synergy effects from additively manufacturing the polymer body, the metallization was analyzed in terms of shape and adhesive strength.

The process that combines selective laser sintering (SLS) and cold isostatic pressing (CIP) can manufacture nearly fully dense metal components with complex geometries. However, the SLS component will shrink to a significant extent during the CIP process. The modified cam-clay model was used to describe the constitutive equation of porous stainless-steel SLS components. The densification process of SLS porous components was simulated using the finite element method. The visual distributions of shape change, displacement, density, and stress were obtained, which showed that SLS components shrank with the same shape as the original design over the CIP process. In addition, a relative uniform density distribution appeared in cold isostatic pressed components. The experiment measurements displayed that the shrinkage rate of SLS components during the CIP process in height direction was a little higher than that on the forming plane due to the layer-by-layer manufacturing process of SLS. On the forming plane, the dimensional errors between simulations and experiments for the cuboid and the gear components are lower than 1% and 3%, respectively. However, the errors in height direction of the two components increase to the range of 6% and 9%.

Selective Laser Sintering (SLS) of poly(ether ether ketone) (PEEK), a high-performance polymer, presents significant challenges due to its narrow processing window, high melting temperature, and low thermal conductivity in powder form. The successful fabrication of highly functional, dense components necessitates precise control over the intricate thermal and fluid dynamics governing the PEEK sintering process. However, experimental and single-physics modeling approaches are often insufficient to capture these transient multi-physics phenomena. This study introduces a novel two-dimensional (2D) multi-physics Finite Element Analysis (FEA) model to simulate the SLS processing of PEEK powder. This study realistically models the transient thermal and fluid behaviour during the SLS process and evaluates the effect of fundamental parameters such as laser power and scanning speed by incorporating combined multi-physical phenomena such as heat transfer, fluid dynamics, and phase transformations. Although optimum thermal profiles are obtained at an Energy Density (ED) of 0.03 J/mm², it has been determined that ED is not the single factor in understanding the thermal behavior. The results show that scan speed significantly regulates heat accumulation and thermal gradients. Slower scanning speeds promote high heat buildup and surface degradation at low powers, while higher speeds limit thermal penetration, increasing the temperature difference between the top and bottom surfaces. This computationally efficient 2D multi-physics approach improves understanding of PEEK laser sintering mechanisms, providing quantitative information for rapid and effective parameter identification in high-performance polymer additive manufacturing.

Selective Laser Sintering (SLS) is an Additive Manufacturing (AM) technology that is receiving considerable attention in the scientific and industrial communities due to its great ability to efficiently produce functional and complex parts. The present work aims to fabricate a real prototype via SLS, such as a hose reel for industrial applications, using polyamide 11 (PA11) as a starting material. Characterization of the PA11 powder properties was first carried out from a thermal and morphological viewpoint to determine the powder's thermal stability by TGA, the sintering window and degree of crystallinity by DSC, and the microstructure by SEM, PSD, and XRD analyses. The results revealed that PA11 has a 45-micron average particle size, circularity close to 1, and a Hausner ratio of 1.17. Together, these parameters ensure that PA11 powder flows smoothly, packs uniformly, and forms dense and defect-free layers during the SLS process, directly contributing to high part quality, dimensional precision, and stable process performance. The printability of the PA11 was optimized for the realization of 3D-printed parts for industrial applications. Finally, the quality of the printed samples and the mechanical and thermal performance were investigated. Several PA11-based parts were fabricated via SLS, showing a high level of complexity and definition, ideal for industrial applications, as confirmed by the predominantly green areas of the colored maps of X-CT. A complete prototypal case for a hose reel was assembled by using the parts realized, and it was chosen as a technological demonstrator to verify the feasibility of PA11 powder in the production of industrial professional components.

Bu çalışmada, bir gaz türbin motoruna ait kompresör palesinin, Ti6Al4V alaşımından Eklemeli Üretim (EÜ) yöntemiyle üretimi ve boyutsal doğrulama ölçümleri gerçekleştirilmiştir. Havacılık endüstrisinde yaygın kullanılan Direkt Metal Lazer Sinterleme (DMLS) yöntemi seçilmiştir. İmalattan sonra her bir palede 87 adet olmak üzere toplam 174 yüzey ölçümü gerçekleştirilmiştir. Ölçümlerde, katı modele oranla, 1 Nu’lı palede ortalama +0,0944/-0,0809 mm arasında, 2 Nu’lı palede ortalama +0,1093/-0,0978 mm değişim olduğu belirlenmiştir. Her iki paledeki geometrik değişimin birbiri ile tutarlı sonuçlar verdiği gözlemlenmiştir. Sonuç olarak, bir uçar-parçanın uçağa takılmasına yönelik uçuşa elverişlilik çalışmaları konusuna girmeden, bir gaz türbin motoru kompresör palelerinin Ti6Al4V alaşımından EÜ yöntemi ile üretilebileceği ortaya konulmuştur.

This study investigates the influence of tooth layer orientation on the bending fatigue behaviour of Nylon 12 spur gears manufactured by a selective laser sintering process in an ‘on-edge’ configuration. The test gears were submitted to single tooth bending fatigue tests, and the thermal response of gears was recorded using Infrared thermography. The surface morphology of failed teeth was examined using microscopy. The effect of tooth layer orientation on the fatigue strength of selective laser sintering gears was evaluated by testing each tooth configuration. The tooth configurations with the highest and lowest strength were 40° and 160°, respectively. The performance of selective laser sintering gears was compared with that of injection moulded Nylon 66 gears. The injection moulded, selective laser sintering 40°, and selective laser sintering 160° gear teeth were tested at multiple loads to investigate the high cycle fatigue and low cycle fatigue behaviour. The bending fatigue life was highest for the injection moulded gears in both low cycle fatigue and high cycle fatigue regimes. The surface temperature was higher in selective laser sintering gears, with 160° configuration exhibiting the highest temperature. The difference between the temperatures of selective laser sintering 40° configuration and injection moulded gear magnified as the applied load increased. Consequently, the strength of the selective laser sintering 40° configuration with respect to injection moulded gear deteriorated in the low cycle fatigue region. Fractography indicated that crack propagation in selective laser sintering 40° and selective laser sintering 160° configurations were cross-laminar and inter-laminar, respectively. In the cross-laminar mode of propagation, the crack propagation was impeded by the layer structure. However, the crack propagation was expedited in the inter-laminar mode, as the crack path was along the interlayer region, which presents a path of least resistance.

An increasing demand for additively manufactured polymer composites with optimized mechanical properties is manifesting in different industries such as aerospace, biomedical, and automotive. Laser sintering (LS) is an additive manufacturing method that has the potential to produce reinforced polymers, which can meet the stringent requirements of these industries. For the development of a commercially viable LS nylon-based composite material, previous research studies worldwide have focused on adding glass beads to the powder material with the goal to produce fully dense parts with properties more representative of injection molded (IM) thermoplastic composites. This led to the development of a commercially available glass bead-filled polyamide 12 (PA12) powder. Although this powder has been on the market for quite a while, an in-depth comparison of the mechanical behavior of laser sintered versus IM glass bead-filled PA12 is lacking. In this study, laser-sintered glass bead-filled PA12 samples were built in different orientations and compared to IM counterparts. After sample production, the mechanical performance of the produced LS and IM parts was tested and compared to evaluate the quasistatic and dynamic mechanical performance and failure mechanisms at different load levels. In addition, the glass bead-filled PA12 properties were also compared to those of standard (unfilled) LS PA12 to assess whether glass beads actually improve the mechanical performance and fatigue lifetime of the final LS samples, as suggested in literature. Results in this work present and explain the increased stiffness but decreased fatigue life of glass bead-filled polyamide parts made by LS and IM. This research can be regarded as a "benchmark" study, in which samples produced from commercially available, filled and unfilled, PA12 powder grades are compared for both LS and conventional production techniques.

Purpose Semi-crystalline polymers such as polyamide-12 can be used for selective laser sintering (SLS) to make near-fully dense plastic parts. At present, however, the types of semi-crystalline polymers suitable for SLS are critically limited. Therefore, the purpose of this paper is to investigate the processibility of a new kind of semi-crystalline polypropylene (PP) with low isotacticity for SLS process. Design/methodology/approach The SLS processibility of the PP powder, including particle size and shape, sintering window, degree of crystallinity and degradation temperature, was evaluated. Effects of the applied laser energy density on the surface micromorphology, density, tensile strength and thermal properties of SLS-built PP specimens were studied. Findings The results show that the PP powder has a nearly spherical shape, smooth surfaces, an appropriate average particle size of 63.6 μm, a broad sintering window of 21 oC and low crystalline degree of 30.4 per cent comparable to that of polyamide-12, a high degradation temperature of 381.8°C and low part bed temperature of 105°C, indicating a very good SLS processibility. The density and the tensile strength first increase with increasing laser energy density until they reach the maximum values of 0.831 g/cm3 and 19.9 MPa, respectively, at the laser energy density of 0.0458 J/mm2, and then decrease when the applied laser energy density continue to increase owing to the degradation of PP powders. The complex PP components have been manufactured by SLS using the optimum parameters, which are strong enough to be directly used as functional parts. Originality/value This paper provides a new knowledge for this field that low-isotacticity PPs exhibit good SLS processibility, therefore increasing material types and broadening the application of SLS technology.

Recent decades have witnessed significant advancements in additive manufacturing (AM) of polymer composites, leading to the development of material systems with intricate architecture and composition. Selective laser sintering (SLS), among various AM methods, offers numerous advantages such as high mechanical strength in printed parts, recyclability of unused powders, and the ability to print large batches without support structures. Moreover, SLS has remarkably succeeded in fabricating electrically conductive polymer composites (ECPCs) with exceptional functional performance which is attributed primarily to the formation of a segregated filler network along the powder particle boundaries. This review aims to delve into SLS for processing polymer-based materials, examining consolidation mechanisms and process parameters, specifically highlighting advancements in electrically conductive polymer composites with a focus on piezoresistive strain-sensing materials and self-sensing structures. Furthermore, the review seeks to elucidate the complex process-structure-property relationships in SLS 3D printed polymer composites, providing an exhaustive overview of the current state-of-the-art in piezoresistive polymer composites.

An n-type Bi2Te3-based thermoelectric material Bi2Te2.85Se0.15 was prepared through an SLS (Selective Laser Sintering) process with E12/Bi2Te2.85Se0.15 as composite powder (weight ratio 1:7), from which E12 was degreased after the SLS process. It was studied the effect of laser power, scanning speed and scanning interval on the density and thermoelectric properties of the sintered samples. The laser power was found the most important influential factor, while the scanning interval was the second and the scanning speed the least. The maximum dimensionless thermoelectric figure of merit ZT is about 0.88 in the condition when the laser power, scanning interval and scanning speed were 20 W, 0.26 mm and 3000 mm s−1, respectively.

Additive manufacturing (AM) can be used without the need of any moulds or tooling, and are very suitable for manufacturing one-piece or small batches of with complex external shapes and internal structures within a short lead time, which are difficult to make or even cannot be fabricated by the tooling and machining processes. The manufacturing of metal parts by sand casting method is a tedious process when considering low volume manufacturing where it took lot of time, design cost, material cost etc., In this paper, the web gland component has been prepared using stainless steel by varying the different process parameters such as scan spacing, laser power and layer thickness in selective laser sintering (SLS) process. By using vickers hardness tester, the hardness and the microstructure of component also analyzed and it is compared with the same component properties prepared by using sand casting process. From the comparative result, it was found that the hardness of material increases by 12.5% on sintered part than casting part.

Additive Manufacturing (AM) has recently attracted huge attentions as a technology for the next generation of industry. Particularly for the manufacturing purposes, various aspects of AM are being studied and applied, such as prototypes for assembly tests, jig production, and actual parts manufacturing. Selective Laser Sintering (SLS) using polyamide is easy to apply to various industries, such as its superior mechanical properties and higher design freedom, but design that takes into account variation in dimensions after manufacture often leads to costly and time-consuming problems. As a way to reduce deformation in the production process, previous studies approached experimentally about the effects of thermal deformation or residual stress on deformation. This is difficult to apply to a specimen of various shapes and sizes and also has limitations as a common solution to dimensional inaccuracies. To propose a solution for mitigating shape deformation of AM part, this paper focused on the effect of phase change of material among various processing parameters that cause shape deformation and tries to present an analytic model. Modeling on the melting and sintering phenomena of powder was presented using Euler-Bernui beam equation. The proposed model was verified by measuring the density variation of manufactured AM components and analyzing the correlation between the degree of contraction and the energy density. Factors such as layer thickness, part thickness, and part placement height were identified to have significant effects on the actual deformation. It is also confirmed that dimensional accuracy of parts that show large deformation by bending has increased by 64.2% when a calibration model is applied through manufacturing of actual parts. Time and cost can be saved for industrial application of AM by applying this proposed calibration model. In addition, by using this model more efficiently in the CAD design process, dimensional accuracy can be enhanced.