Selective Laser Sintering Process Research Articles

Ammonium polyphosphate and pentaerythritol as a flame-retardant system for polyamide 12 in selective laser sintering

Abstract This study investigates the incorporation of an intumescent flame-retardant system, based on a intumescent combination of ammonium polyphosphate (APP) and pentaerythritol (PER), into polyamide 12 (PA12) for selective laser sintering (SLS). The influence of processing parameters and filler content on the mechanical and fire properties of the manufactured components is analyzed. Particle size analysis and powder density measurements were conducted to assess the powder characteristics, revealing impact on the powder density of the mixtures. DRIFT measurements show that the flame-retardant additives require only minor adjustments to the energy input during SLS processing. Manufacturing was conducted with different energy densities, to assess the ideal manufacturing parameters. DSC and ATR measurements indicate that the addition of the flame-retardant system alters the crystallization behavior of PA12, promoting the formation of the α-modification and influencing the crystal morphology. Tensile tests demonstrate that while Young’s modulus remains comparable to that of non-flame-retardant PA12, the tensile strength and elongation at break are reduced. LOI testing confirms the effectiveness of the flame-retardant system, with increasing additive fractions leading to improved flame retardancy. Cone calorimeter measurements reveal a significant reduction in both total heat released (THR) and peak heat release rate (pHRR) with the incorporation of the APP-PER system, highlighting its effectiveness in mitigating heat release and suppressing flame propagation during combustion.

4D printing of multiscale filler–reinforced thermoplastic polyurethane nanocomposites with electro-activated shape memory properties

ABSTRACT Four-dimensional printing of shape memory materials has been developed to dynamically control the shapes of printed structures for applications such as self-deployable structures, actuators, and sensors. Herein, a novel electro-activated shape memory nanocomposite material for the selective laser sintering (SLS) process is developed. The nanocomposite powder incorporates a new type of multiscale hybrid filler, consisting of carbon fibres and carbon nanotubes (CNTs), with CNT-coated thermoplastic polyurethane nanocomposite powders. The shape recovery process of the nanocomposite with a 20 wt% hybrid-filler addition is almost four times faster when triggered by electric currents than that triggered by the direct heating method and exhibits a higher shape recovery ratio. A remotely and selectively controlled smart component is fabricated to demonstrate the potential applications of the novel nanocomposites. This work provides a promising solution to achieve function–structure integration through SLS for future high-tech applications.

The effect of mechanical properties on polymer deformation and flow suspension in the Selective Laser Sintering process

The effect of mechanical properties on polymer deformation and flow suspension in the Selective Laser Sintering process

Optimization of porosity and strength of selective laser-sintered polyamide porous scaffolds useful in bone tissue engineering

Purpose This study aims to focus on optimization of process parameters for porosity and strength of polyamide porous bone scaffolds fabricated via selective laser sintering (SLS) process. Design/methodology/approach Taguchi’s design of experiment approach with L18 orthogonal array (OA) has been used to optimize the process parameters. Five process and four response parameters have been considered for this study. Initially, minimum size of the pores that can be depowdered was identified. Then, porous CAD models of test specimen to measure porosity and strength were designed in Solidworks® software and fabricated using EOSINT P395 m/c. Signal-to-noise ratio and analysis of variance were used to identify the optimal levels of parameters and statistical significance of the parameters. Findings Among five parameters, powder refresh rate, build chamber temperature and layer thickness were found to have significant influence on all the response parameters, whereas build orientation and build position were found insignificant for all the responses. The Taguchi’s confirmation test validated the results of the study with maximum deviation of 5.8% for compressive strength. Comparison of predicted and experimental values revealed a satisfactory predictability of all the developed linear regression models. Originality/value This study reveals optimal set of parameters for SLS of the polyamide porous bone scaffolds. The optimal set of parameters may be used by other researchers to get enhanced combination of strength and porosity while fabricating porous scaffolds.

The Cardiff Eye Shape Analysis Protocol (CESAP): Producing a digital representation of the anterior ocular surface.

The Cardiff Eye Shape Analysis Protocol (CESAP): Producing a digital representation of the anterior ocular surface.

Tensile loading response of strut-based mechanical metamaterials fabricated using selective laser sintering process

Tensile loading response of strut-based mechanical metamaterials fabricated using selective laser sintering process

Progress on High-Performance PEEK Material for 3D Printing

Amidst the rising demand for lightweight, sturdy, and durable materials across various industries, the research emphasizes the widespread application of polyetheretherketone (PEEK) due to its superior characteristics. This paper inquiry scrutinizes the advanced potential of three-dimensional printing utilizing high-performance PEEK material, with a concentrated examination of the Fused Deposition Modeling (FDM) and Selective Laser Sintering (SLS) methodologies. These technologies have been verified to fabricate complex structures and customized components accurately. The analysis investigates how key printing parameters such as printing temperature, bed temperature, laser power, and scanning speed influence the mechanical properties and microstructure of PEEK components. Nonetheless, the study acknowledges the difficulties encountered with FDM and SLS processes, including high-temperature operations, insufficient adhesion, warping deformation, and inconsistent powder density challenges. Addressing these issues is essential to fully harness the advantages of 3D printing with PEEK material. The paper proposes several avenues for future research aimed at mitigating these challenges, such as optimizing printing parameters to enhance stability and component quality, developing improved thermal management systems and print bed surface treatments to boost adhesion and minimize warping, exploring material research for additional 3D printing substances, and refining models based on empirical data to enhance printing precision and efficiency. This study underscores the considerable potential of 3D printing with high-performance PEEK material to transform manufacturing processes, facilitating the production of high-performance components with complex geometries and customized designs, thereby promoting innovation across various industries.

Selective Laser Sintering: Processing, Materials, Challenges, Applications, and Emerging Trends

Selective laser sintering (SLS) has revolutionized manufacturing by enabling the production of intricate designs with enhanced flexibility and material efficiency. The present review delves into the SLS process, its compatibility with materials such as polymers, metals, and composites, and its influence on microstructure, mechanical properties, and overall performance. It addresses challenges like dimensional accuracy, surface finish, and residual stress while highlighting applications across various industries. Additionally, the review explores emerging trends, including hybrid manufacturing and the integration of artificial intelligence, to shape future developments in SLS technology.

Chess-like Pieces Realized by Selective Laser Sintering of PA12 Powder: 3D Printing and Micro-Tomographic Assessment.

The paper highlights the realization of 3D-printed parts with complex geometries, such as chess-like pieces, using polyamide 12 (PA12) as polymeric powder via selective laser sintering (SLS). The research activity focuses on the study of the powder printability, the optimization of the printing parameters, and the tomographic evaluation of the printed objects. Morphological analyses were carried out to study the PA12 powder microstructure considering that SLS required specific particle size distribution and shape, able to guarantee a good flowability necessary to take part in a sintering process. DSC and TG analyses were performed to determine the sintering window and the crystallinity degree, and to evaluate the thermal stability of the PA12 powder due to the importance of the powder processability for the SLS process. The novelty lies in the realization of chess-like pieces very challenging to print via SLS due to their different and highly detailed structures, and the in-depth analysis of the dimensional accuracy evaluated by micro-tomography. The 3D-printed samples obtained show high printing quality and dimensional stability. The μ-CT analysis also confirms the key role of the object shape and section changes on the final porosity of the chess-like pieces.

Performance evaluation of developing electrical discharge machining tools through 3D-printed mould using selective laser sintering and expanding its applications in developing free-form tools

In the current study, an attempt has been made to find the optimum parameters for electroplating three-dimensional (3D) casted low melting point alloys. The electroplated profile is used as a tool in an electric discharge machining setup. A selective laser sintering process is used for 3D printing the mould in two halves. The mould parts are 3D scanned to find out the dimensional deviation. The low melting point alloy (LMPA) is cast in the mould. The surface roughness of the mould and the pattern are measured. Electroplating the casted LMPA sample is carried out in three stages in search of optimum parameters for getting stable copper deposits. The thickness of copper deposits under varying conditions is measured. The microstructures of cast alloys and copper deposits are analysed using a scanning electron microscope. The casted alloy and copper composition is verified through energy dispersive spectroscopy mapping and X-ray diffraction technique. The developed electric discharge machining electrode successfully performs the machining on the workpiece, and its performance is compared with that of a solid copper tool. The information gained is transferred to prepare the free-form tool using the developed path and is tested on the implant-shaped workpiece.

Evaluating process parameters of SLS part of polyamide-12 recycled powder using RSM

Abstract Selective laser sintering (SLS) is a highly flexible rapid prototyping (RP) technology which can use a wide range of powdered materials to generate high quality complex geometries directly from digital models. The SLS process uses a laser to sinter selected areas of powdered materials to produce solid objects layer by layer, according to the 2D data obtained from CT scan or MRI imaging techniques. This paper presents research work for evaluating the effect of process parameters on impact toughness and surface roughness of the part manufactured on Farsoon SS402P SLS from recycled ageing FS 3300PA which is PA-12 based powder and standard operating parameters using Response Surface Methodology (RSM) design of experiments. Impact tests have been performed as per the ASTM D6110 standard using recommendations from ISO 179-2. According to the results, effect of process parameters are successfully analyzed by employing impact toughness and surface roughness tests. Based on the results of the ANOVA analysis, impact toughness increases with increasing laser power (4.467 j/cm2 at 72.5 watts). Similarly, it is also clear from the results that the region with the lowest laser power, high layer thickness, and 90-degree orientation had the lowest surface roughness (3.46 μm).

Study on the mechanical properties of PES-HmA samples printed by selective laser sintering under various pre-heating conditions

The purpose of this study is to investigate the influence of pre-heating characteristics on the mechanical properties and forming process of selective laser sintering (SLS) printed PES-HmA samples. An experimental setup with four heating tubes was designed to study the pre-heating temperature distribution on the powder bed. The pre-heating temperature distribution on the powder bed was captured using a thermal imaging camera. A method for evaluating pre-heating temperature distribution based on the average and standard deviation of surface temperature was proposed. The heating tube installation position was optimized using a response surface experiment study based on the temperature distribution evaluation. By optimizing the installation position of the tubes, the temperature distribution on the powder bed tends to become uniform. The effect of pre-heating temperature value and distribution on the mechanical properties of the SLS printed PES-HmA samples was also experimentally investigated. The cross sectional microstructure of the printed samples were examined by scanning electron microscope to analyze the layer formation process at different pre-heating temperature. By increasing the pre-heating temperature from 70°C to 100°C, the material diffusion at the layers interface was improved, which made the tensile strength of sample increased by 376%, and the flexural strength increased by 224%.

Analysis of small plastic gears manufactured by SLS printing

Selective laser sintering (SLS) is an additive manufacturing method. During the production, the equipment sinters powdered material and binds this material together to create a solid structure. SLS 3D printers use a laser as the power and heat source. During the manufacturing process, the laser is aimed automatically at points in space defined by the 3D model. Since in the past we have worked on the manufacturing of small plastic gears by other additive techniques (FDM, stereolithography) and on the determination of their accuracy, in this article we determined the same characteristics for the SLS process.

Enhanced SiC/NFG/Ni ternary composite microwave absorbing materials with micro-network structures produced by selective laser sintering

Enhanced SiC/NFG/Ni ternary composite microwave absorbing materials with micro-network structures produced by selective laser sintering

Thermomechanical Assessment of Recovered PA12 Powders with Basalt Filler for Automotive Components

Additive manufacturing processes allow for precise and efficient production, but it is estimated that one-third of the materials used results in waste. Further improvement in a sustainable perspective could come from the ability to manage these scraps and from the exploration of different routes for recovery and reuse. The Selective Laser Sintering process is particularly sensitive to this issue due to the waste ratio which can reach a very high quantity of not-sintered virgin powders. In this research study, recovered PA12 powders, preliminarily characterized through thermal and mechanical analysis, were mixed with 15% basalt powder to improve their aspect and thermomechanical resistance. The influence of basalt powder (BP) on mechanical properties as well as on the thermal stability of polyamide12 (PA12) powder composites was investigated. A study conducted on mechanical properties showed that polymeric composites’ stiffness and hardness were influenced by adding filler, thus improving mechanical parameters. On the other hand, the application of thermogravimetric analysis allowed us to determine the composite’s thermal stability. The objective is to obtain a recovered fully biobased material that could be used to substitute the petroleum-derived polymeric ones currently employed in the production of interiors and shells in the automotive sector.

Selective Laser Sintering of Polymers: Process Parameters, Machine Learning Approaches, and Future Directions

Selective laser sintering (SLS) is a bed fusion additive manufacturing technology that facilitates rapid, versatile, intricate, and cost-effective prototype production across various applications. It supports a wide array of thermoplastics, such as polyamides, ABS, polycarbonates, and nylons. However, manufacturing plastic components using SLS poses significant challenges due to issues like low strength, dimensional inaccuracies, and rough surface finishes. The operational principle of SLS involves utilizing a high-power-density laser to fuse polymer or metallic powder surfaces. This paper presents a comprehensive analysis of the SLS process, emphasizing the impact of different processing variables on material properties and the quality of fabricated parts. Additionally, the study explores the application of machine learning (ML) techniques—supervised, unsupervised, and reinforcement learning—in optimizing processes, detecting defects, and ensuring quality control within SLS. The review addresses key challenges associated with integrating ML in SLS, including data availability, model interpretability, and leveraging domain knowledge. It underscores the potential benefits of coupling ML with in situ monitoring systems and closed-loop control strategies to enable real-time adjustments and defect mitigation during manufacturing. Finally, the review outlines future research directions, advocating for collaborative efforts among researchers, industry professionals, and domain experts to unlock ML’s full potential in SLS. This review provides valuable insights and guidance for researchers in regard to 3D printing, highlighting advanced techniques and charting the course for future investigations.

3D printing of high-stiffness and high-strength glass fiber reinforced PEEK composites by selective laser sintering

3D printing of high-stiffness and high-strength glass fiber reinforced PEEK composites by selective laser sintering

Towards the Reuse of Fire Retarded Polyamide 12 for Laser Sintering.

The control of powder aging during Selective Laser Sintering (SLS) processing is one of the challenges to be overcome for the implementation of this technique in serial production. Aging phenomena, because of the elevated temperatures and long processing times, need to be considered when a fraction of the polymer powders present in the build chamber and not used to manufacture the parts are reused at various times. The aim of this study was to investigate the influence of successive reuse of blends of pure Polyamide 12 and its blends with two types of flame retardants (FR): ammonium polyphosphate (APP) and zinc borate (ZB). The composition of the blends was 70/30 (wt/wt) PA 12/FR. Four successive processing stages have been carried out by collecting the remaining powder blend each time. The powders were re-used using the same processing parameters after sieving. DSC measurements showed that the incorporation of FRs entailed a reduction in the processing window up to 4 °C; nevertheless, no further reduction was noted after aging. The TGA curves of aged blends of powders were also similar for pure PA 12 and PA 12 with FR. In addition, initial and reused powders presented a higher degree of crystallinity than the specimens processed from the powders. The heterogeneous character of the PA 12 after LS processing or reprocessing was shown through Pyrolysis Combustion Flow Calorimetry (PCFC) and cone calorimeter (CC) tests. FTIR analysis also showed that post-condensation reactions have occurred. The mode of action of the flame retardants was clearly seen on HRR curves at both tests. The first reuses of PA 12 powders entailed a significant reduction in time to ignition at the cone calorimeter (150 for the initial material to around 90 s for the reused material), indicating the formation of short polymer chains. Only in the case of zinc borate was it noticed that re-used powder was detrimental to the fire performance because of a strong increase in the value of pHRR (between 163 and 220 kW/m2 for reused material instead of 125 kW/m2 for the initial one).

Simulation of the selective laser sintering/melting process of bioactive glass 45S5

Simulation of the selective laser sintering/melting process of bioactive glass 45S5

3D-printed Biomimetic Bioactive Glass Scaffolds for Bone Regeneration in Rat Calvarial Defects.

The pore geometry of scaffold intended for the use in the bone repair or replacement is one of the most important parameters in bone tissue engineering. It affects not only the mechanical properties of the scaffold but also the amount of bone regeneration after implantation. Scaffolds with five different architectures (cubic, spherical, x, gyroid, and diamond) at different porosities were fabricated with bioactive borate glass using the selective laser sintering (SLS) process. The compressive strength of scaffolds with porosities ranging from 60% to 30% varied from 1.7 to 15.5 MPa. The scaffold’s compressive strength decreased significantly (up to 90%) after 1-week immersion in simulated body fluids. Degradation of scaffolds is dependent on porosity, in which the scaffold with the largest surface area has the largest reduction in strength. Scaffolds with traditional cubic architecture and biomimetic diamond architecture were implanted in 4.6 mm diameter full-thickness rat calvarial defects for 6 weeks to evaluate the bone regeneration with or without bone morphogenetic protein 2 (BMP-2). Histological analysis indicated no significant difference in bone formation in the defects treated with the two different architectures. However, the defects treated with the diamond architecture scaffolds had more fibrous tissue formation and thus have the potential for faster bone formation. Overall, the results indicated that borate glass scaffolds fabricated using the SLS process have the potential for bone repair and the addition of BMP-2 significantly improves bone regeneration.