An Automated Laser Control Technique for Improving Powder Bed Temperature Uniformity in Selective Laser Sintering

2018 ◽  
pp. 239-249
Author(s):  
T. Phillips ◽  
L. Zhang ◽  
S. Fish ◽  
J. Beaman
Keyword(s):  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Control Technique ◽  
Temperature Uniformity ◽  
Powder Bed ◽  
Bed Temperature ◽  
Laser Control

scholarly journals Setting the Optimal Laser Power for Sustainable Powder Bed Fusion Processing of Elastomeric Polyesters: A Combined Experimental and Theoretical Study

Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 385
Author(s):  
Ruben Vande Ryse ◽  
Mariya Edeleva ◽  
Ortwijn Van Stichel ◽  
Dagmar R. D’hooge ◽  
Frederik Pille ◽  
...  
Keyword(s):  
Laser Power ◽  
Theoretical Study ◽  
Selective Laser Sintering ◽  
Polymeric Materials ◽  
Thermoplastic Elastomer ◽  
Processing Parameters ◽  
Operating Conditions ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Bed Temperature

Additive manufacturing (AM) of polymeric materials offers many benefits, from rapid prototyping to the production of end-use material parts. Powder bed fusion (PBF), more specifically selective laser sintering (SLS), is a very promising AM technology. However, up until now, most SLS research has been directed toward polyamide powders. In addition, only basic models have been put forward that are less directed to the identification of the most suited operating conditions in a sustainable production context. In the present combined experimental and theoretical study, the impacts of several SLS processing parameters (e.g., laser power, part bed temperature, and layer thickness) are investigated for a thermoplastic elastomer polyester by means of colorimetric, morphological, physical, and mechanical analysis of the printed parts. It is shown that an optimal SLS processing window exists in which the printed polyester material presents a higher density and better mechanical properties as well as a low yellowing index, specifically upon using a laser power of 17–20 W. It is further highlighted that the current models are not accurate enough at predicting the laser power at which thermal degradation occurs. Updated and more fundamental equations are therefore proposed, and guidelines are formulated to better assess the laser power for degradation and the maximal temperature achieved during sintering. This is performed by employing the reflection and absorbance of the laser light and taking into account the particle size distribution of the powder material.

Physical Modeling for Selective Laser Sintering Process

2017 ◽  
Vol 17 (2) ◽  
Author(s):  
Arash Gobal ◽  
Bahram Ravani
Keyword(s):  
Physical Modeling ◽  
Large Scale ◽  
Selective Laser Sintering ◽  
Powdered Material ◽  
Laser Sintering ◽  
Industrial Applications ◽  
Transient Temperature ◽  
Sintering Process ◽  
Powder Bed ◽  
Selective Heating

The process of selective laser sintering (SLS) involves selective heating and fusion of powdered material using a moving laser beam. Because of its complicated manufacturing process, physical modeling of the transformation from powder to final product in the SLS process is currently a challenge. Existing simulations of transient temperatures during this process are performed either using finite-element (FE) or discrete-element (DE) methods which are either inaccurate in representing the heat-affected zone (HAZ) or computationally expensive to be practical in large-scale industrial applications. In this work, a new computational model for physical modeling of the transient temperature of the powder bed during the SLS process is developed that combines the FE and the DE methods and accounts for the dynamic changes of particle contact areas in the HAZ. The results show significant improvements in computational efficiency over traditional DE simulations while maintaining the same level of accuracy.

Design and Modeling of a Microscale Selective Laser Sintering System

2016 ◽  
Author(s):  
Nilabh Roy ◽  
Anil Yuksel ◽  
Michael Cullinan
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Feature Size ◽  
Powder Bed ◽  
Metal Additive Manufacturing ◽  
Wave Nature ◽  
Field Radiation ◽  
Metal Additive

The development of micro and nanoscale additive manufacturing methods in metals and ceramics is important for many applications in the aerospace, medical device, and electronics industries. Unfortunately, most commercially available metal additive manufacturing tools have feature-size resolutions of greater than 100 μm, which is too large to precisely control the microstructure of the parts they produce. A few research-grade metal additive manufacturing tools do exist, but their build rate is generally too slow for commercial applications. Therefore, this paper presents a new microscale selective laser sintering (μ-SLS) that can be used to improve the minimum feature-size resolution of metal additively manufactured parts by up to two orders of magnitude, while still maintaining the throughput of traditional additive manufacturing processes. In order to achieve this goal, several innovative design features like the use of (1) ultra-fast lasers, (2) a micro-mirror based optical system, (3) nanoscale powders, and (4) a precision spreader mechanism, have been implemented. The micro-SLS system is capable of achieving build rates of approximately 1 cm3/hr while achieving a feature-size resolution of approximately 1 μm. This paper will also present new molecular scale models that have been developed for the micro-SLS to quantify and certify the micro-SLS build process. Modeling of the micro-SLS process is challenging, because most macroscale models of the SLS process contain assumptions that are no longer valid when the size of the particles that are being sintered is smaller than the wavelength of the laser being used to sinter them. Therefore, in modeling the micro-SLS process we must account for the wave nature of light and can no longer rely on the ray tracing models commonly used to model the SLS process. Also, heat transfer in the micro-SLS process is dominated by near-field radiation due to the diffraction of the light off the nanoparticles in the powder bed and the ultrafast lasers that are used in the micro-SLS system. This means that the assumptions of heat transfer by conduction and far-field radiation in the macroscale SLS systems are no longer valid for the micro-SLS system. Finally, the agglomeration of nanoparticles in the powder bed must be accurately modeled in order to precisely predict the formation of defects in the final parts produced. Overall, the goal of this modeling effort is to be able to predict the quality of a part produced using any given processing conditions, in order to produce parts that are “born certified” and do not need to be tested post fabrication.

Selective Laser Sintering of Tissue Engineering Scaffolds Using Poly(L-Lactide) Microspheres

2007 ◽  
Vol 334-335 ◽  
pp. 1225-1228 ◽  
Author(s):  
Wen You Zhou ◽  
S.H. Lee ◽  
Min Wang ◽  
W.L. Cheung
Keyword(s):  
Tissue Engineering ◽  
Porous Scaffold ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Porous Scaffolds ◽  
Tissue Engineering Scaffolds ◽  
Water Emulsion ◽  
Bed Temperature ◽  
Oil In Water Emulsion ◽  
Polyamide Powder

This paper reports a study on the modification of a commercial selective laser sintering (SLS) machine for the fabrication of tissue engineering scaffolds from small quantities of poly(L-lactide) (PLLA) microspheres. A miniature build platform was designed, fabricated and installed in the build cylinder of a Sinterstation 2000 system. Porous scaffolds in the form of rectangular prism, 12.7×12.7×25.4 mm3, with interconnected square and round channels were designed using SolidWorks. For initial trials, DuraFormTM polyamide powder was used to build scaffolds with a designed porosity of ~70%. The actual porosity was found to be ~83%, which indicated that the sintered regions were not fully dense. PLLA microspheres in the size range of 5-30 μm were made using an oil-in-water emulsion solvent evaporation procedure and they were suitable for the SLS process. A porous scaffold was sintered from the PLLA microspheres with a laser power of 15W and a part bed temperature of 60oC. SEM examination showed that the PLLA microspheres were partially melted to form the scaffold. This study has demonstrated that it is feasible to build tissue engineering scaffolds from small amounts of biomaterials using a commercial SLS machine with suitable modifications.

Experimental investigations of curling phenomenon in selective laser sintering process

2016 ◽  
Vol 22 (2) ◽  
pp. 405-415 ◽  
Author(s):  
Alkhair Almabrouk Mousa
Keyword(s):  
Glass Bead ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Experimental Investigations ◽  
Rapid Manufacturing ◽  
Material System ◽  
Geometric Accuracy ◽  
Sintering Process ◽  
Content Type ◽  
Bed Temperature

Purpose This paper aims to investigate the curling behaviour of selective laser sintered polyamide/glass bead composites with changes in material compositions, part bed temperature, powder base thickness, laser power and layer cooling time. Design/methodology/approach The Taguchi parameter design method (design of experiments, DOE) and analysis of variance (ANOVA) technique were applied in the investigation to determine the optimal process parameter settings. Findings The results of statistical analysis and ANOVA provided evidence for the effectiveness of filler content and its surface treatment on reducing the amount of curling. Research limitations/implications Warping and curling phenomena is one of several aspects of this work that can be pursued further. The present investigation could be expanded to explore other fillers and interface adhesion using other modifiers. Experiments could be conducted with other complicated geometries, various sizes, different positions and locations to widen the knowledge base of geometric accuracy of selective laser sintering process. Practical implications This experimental work is beneficial for materials development and accuracy characterisation in rapid manufacturing techniques. The experimental techniques adopted are readily transferable to virtually any material system used in rapid manufacturing. Originality/value Although many materials have been developed, there is still a need for research into new materials. This work demonstrates that it is possible to improve the geometric accuracy of selective laser sintered components from glass bead- filled polyamide 12 and achieve near-zero curling by adding rigid multiphase-coated particle to the material system.

3D Modeling of Additive Manufacturing Process: The Case of Polymer Laser Sintering

2020 ◽  
Author(s):  
Lan Zhang ◽  
M'hamed Boutaous ◽  
Shihe Xin ◽  
Dennis A. Siginer
Keyword(s):  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Heat Diffusion ◽  
Laser Scattering ◽  
Transient Phenomena ◽  
Powder Bed ◽  
Process Characteristics ◽  
Polymer Powder ◽  
Volume Method ◽  
Air Diffusion

Abstract This work focusses on studying multiphysical transient phenomena in polymer powders occurring during selective laser sintering in polymers powders. Multiple phenomena stemming from the interaction of the laser with the polymer powder bed and the transfer of the laser power to the powder bed including laser scattering and absorption, polymer heating, melting, coalescence, densification, and the variation of the material parameters with the temperature are simulated via the modified Monte Carlo-ray tracing method coupled with the Mie theory. A finite volume method is adopted for the heat transfer. The model couples heat diffusion, melting, coalescence and densification of the polymer grains, and the crystallization kinetics during the cooling steps. Laser intensity is concentrated on the surface of the material contrary to the predictions of the Beer-Lambert law. Laser acting on thermoplastic material cause the polymer powder melt, coalescence between melted grains, air diffusion versus densification, crystallization and volume shrinkage. All these processes are simulated by a series of multiphysical models. The reliability of the modeling is tested by comparison with experiments in the literature, and a parametric analysis is performed, based on the process characteristics such as laser sweep speed, its intensity and shape, polymeric grain size among others. Several recommendations to optimize the process are proposed.

Rapid Manufacturing Using Infiltration Selective Laser Sintering

2008 ◽  
Author(s):  
David L. Bourell ◽  
Phani Vallabhajosyula ◽  
Brooke Stevinson ◽  
Ssuwei Chen ◽  
Joseph J. Beaman
Keyword(s):  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Rapid Manufacturing ◽  
Solid Model ◽  
Powder Bed ◽  
Freeform Fabrication ◽  
Dimensional Changes ◽  
Linear Dimensions ◽  
Plastic Powder ◽  
Computer Controlled

Selective Laser Sintering (SLS) is tooless, computer-controlled layerwise additive manufacturing using a laser and a powder bed. The scanning laser locally melts the surface of a powder bed selectively, followed by deposition of a fresh layer of powder and repetition of the process. SLS has been developed for plastic powder. Creation of non-metallics and metal parts is more challenging. One approach is to mix the master powder with a transient binder. SLS melts the binder which wets the master powder, creating a green part. Subsequent post-processing is required to either remove the binder or convert it to a usable form. The last step is infiltration with a molten substance. Fundamentals of infiltration theory will be reviewed. A study of dimensional changes associated with various stages of processing reveals that overall linear dimensions vary less than one percent compared to the computer solid model. Several examples demonstrating the utility of an infiltration approach to freeform fabrication will be presented. These include silicon carbide with a phenolic binder, infiltrated with silicon; graphite with a phenolic binder infiltrated with epoxy; and tool steel with a proprietary low-ash binder infiltrated with cast iron.

scholarly journals Simulation of the Heat Laser of the Selective Laser Sintering Process of the Polyamide12

2021 ◽  
Vol 297 ◽  
pp. 01050
Author(s):  
Hanane Yaagoubi ◽  
Hamid Abouchadi ◽  
Mourad Taha Janan
Keyword(s):  
Heat Flux ◽  
3D Printing ◽  
Selective Laser Sintering ◽  
3D Models ◽  
Laser Sintering ◽  
Laser Source ◽  
Sintering Process ◽  
Powder Bed ◽  
Source Models ◽  
Flux Diffusion

Laser sintering sintering is one of the most widely used 3D printing technologies, in which it transforms 3D models into authentic parts with generally excellent workmanship, the test today is to ensure the unmatched nature of the item produced, therefore hypothetically to understand and predict the thermal history in this process, the thermal models must be exact and fair, In this article, the consideration will be focused on the different models of heat flux diffusion, in the bibliography, some formulas Numbers that describe the transport of the heat source out of the powder bed have been found. A comparison between its laser source models will be established. The re-modeling takes place in MATLAB using the parameters of polyamide12.

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