scholarly journals Process Phenomena and Material Properties in Selective Laser Sintering of Polymers: A Review

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 183
Author(s):  
Federico Lupone ◽  
Elisa Padovano ◽  
Francesco Casamento ◽  
Claudio Badini
Keyword(s):  
Material Properties ◽  
Complex Geometry ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Laser Source ◽  
Layer By Layer ◽  
Powder Bed ◽  
Complex Process ◽  
And Performance ◽  
Physical Phenomena

Selective laser sintering (SLS) is a powder bed fusion technology that uses a laser source to melt selected regions of a polymer powder bed based on 3D model data. Components with complex geometry are then obtained using a layer-by-layer strategy. This additive manufacturing technology is a very complex process in which various multiphysical phenomena and different mechanisms occur and greatly influence both the quality and performance of printed parts. This review describes the physical phenomena involved in the SLS process such as powder spreading, the interaction between laser beam and powder bed, polymer melting, coalescence of fused powder and its densification, and polymer crystallization. Moreover, the main characterization approaches that can be useful to investigate the starting material properties are reported and discussed.

Evolution of Direct Selective Laser Sintering of Metals

2011 ◽  
Vol 383-390 ◽  
pp. 6252-6257
Author(s):  
Francesco Cardaropoli ◽  
Fabrizia Caiazzo ◽  
Vincenzo Sergi
Keyword(s):  
Complex Geometry ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Layer By Layer ◽  
Metal Powders ◽  
Additive Process ◽  
Operator Experience ◽  
Critical Phases ◽  
Time Required

Direct Metal Selective Laser Sintering (DMSLS) is a layer-by-layer additive process for metal powders, which allows quick production of complex geometry parts. The aim of this study is to analyse the improvement of DMSLS with “EOSINT M270”, the new laser sintering machine developed by EOS. Tests were made on sintered parts of Direct Metal 20 (DM20), a bronze based powder with a mean grain dimension of 20 μm. Different properties and accuracy were evaluated for samples manufactured with three different exposure strategies. Besides mechanical properties, the manufacturing process was also examined in order to evaluate its characteristics. The quality of laser sintered parts is too affected by operator experience and skill. Furthermore, critical phases are not automatic and this causes an extension of time required for the production. Due to these limitations, DMSLS can be used for Rapid Manufacturing, but it is especially suitable to few sample series.

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.

A Switched Adaptive Model for Layer-to-Layer Selective Laser Melting With Varying Laser Paths

2020 ◽  
Author(s):  
Xin Wang ◽  
Douglas A. Bristow ◽  
Robert G. Landers
Keyword(s):  
Feedback Control ◽  
Selective Laser Melting ◽  
Optical Sensors ◽  
Laser Source ◽  
Layer By Layer ◽  
Adaptive Model ◽  
Laser Melting ◽  
Powder Bed ◽  
Complex Process ◽  
Solid Part

Abstract Selective Laser Melting (SLM) is an additive manufacturing technique that uses a moving laser source to melt and solidify an area of a powder bed by scanning over the area with a laser beam, thus, fabricating a solid part layer by layer. Although SLM can print complex geometries that are difficult to achieve by machining, quality and repeatability of a printed part are still two challenges that must be addressed. These challenges arise due to the complex physical transformation of the metal powder and the lack of mature process control schemes. Researchers often use optical sensors for the feedback control of SLM processes. Since fast motion of laser beams may not allow real time feedback control given the large quantity of data to be processed, some researchers have applied layer-to-layer control, i.e., collecting data during the fabrication of an entire layer and then updating process parameter profiles for the next layer. In this paper, by specifying the input and output as laser power and peak temperature, a parameter adaption model is used to estimate the unknown input-output model, which is difficult to evaluate analytically due to complex process physics. In addition, laser paths in SLM usually vary to create more isotropic parts than can be achieved with constant laser paths. The variation of laser paths results in varying local thermal histories. To handle the common situation where laser paths are varying from layer to layer, a switched model is designed and trained by a Parameter Adaption Algorithm (PAA). In a simulation of an overhang part with a constant cross-section and varying laser paths, the switched adaptive model shows the ability to achieve a desired output profile and also better performance if more switched gains are utilized.

Selective Laser Sintering of Resin-Coated Sands—Part I: The Laser-Material Interaction

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Fabrizio Quadrini ◽  
Loredana Santo
Keyword(s):  
Focal Spot ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Laser Source ◽  
Layer By Layer ◽  
Sintering Process ◽  
New Approach ◽  
Laser Material ◽  
Definition Of ◽  
Material Interaction

Selective laser sintering of precoated sands is a process utilized to produce molds and cores for rapid casting by adding sand layer by layer and heating it using a laser beam. During the process, the resin flows and binds the grains; subsequently, an oven is used for the postcuring treatment to complete the curing of the resin. The aim of this paper was to study the laser-material interaction using a diode laser to directly obtain the material consolidation. It was the first step in the definition of a new approach for process investigation and innovation. Two main aspects were investigated with the laser source in a standstill position: first, the influence of the laser power, the location of the focal spot, and the exposure time on sand consolidation; second, the shape and dimension of cured samples depending on the process parameters. The experimental data, in terms of weight and size of the hardened sands, were analyzed, and a master curve was found. In Part II of this paper the selective laser sintering process will be implemented to produce shells.

scholarly journals Effects of Positioning Conditions on Material Properties In Powder bed Fusion Additive Manufacturing

2021 ◽  
Author(s):  
Mevlüt Yunus Kayacan ◽  
Nihat Yılmaz
Keyword(s):  
Additive Manufacturing ◽  
Material Properties ◽  
Layer By Layer ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Cooling Rates ◽  
Powder Bed ◽  
Manufacturing Technologies ◽  
Average Size ◽  
Hardness Values

Abstract Among additive manufacturing technologies, Laser Powder Bed Fusion (L-PBF) is considered the most widespread layer-by-layer process. Although the L-PBF, which is also called as SLM method, has many advantages, several challenging problems must be overcome, including part positioning issues. In this study, the effect of part positioning on the microstructure of the part in the L-PBF method was investigated. Five Ti6Al4V samples were printed in different positions on the building platform and investigated with the aid of temperature, porosity, microstructure and hardness evaluations. In this study, martensitic needles were detected within the microstructure of Ti6Al4V samples. Furthermore, some twins were noticed on primary martensitic lines and the agglomeration of β precipitates was observed in vanadium rich areas. The positioning conditions of samples were revealed to have a strong effect on temperature gradients and on the average size of martensitic lines. Besides, different hardness values were attained depending on sample positioning conditions. As a major result, cooling rates were found related to positions of samples and the location of point on the samples. Higher cooling rates and repetitive cooling cycles resulted in microstructures becoming finer and harder.

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.

Additive Manufacturing of Nickel-Based Super Alloys for Aero Engine Applications

2020 ◽  
pp. 48-70
Author(s):  
Raja A. ◽  
Mythreyi O. V. ◽  
Jayaganthan R.
Keyword(s):  
Additive Manufacturing ◽  
Complex Geometry ◽  
Source Parameters ◽  
Raw Material ◽  
Layer By Layer ◽  
Powder Bed ◽  
Complex Design ◽  
Direct Energy ◽  
Second Phases ◽  
Metal Addition

Ni based super alloys are widely used in engine turbines because of their proven performance at high temperatures. Manufacturing these parts by additive manufacturing (AM) methods provides researchers a lot of creative space for complex design to improve efficiency. Powder bed fusion (PBF) and direct energy deposition (DED) are the two most widely-used metal AM methods. Both methods are influenced by the source, parameters, design, and raw material. Selective laser melting is one of the laser-based PBF techniques to create small layer thickness and complex geometry with greater accuracy and properties. The layer-by-layer metal addition generates epitaxial growth and solidification in the built direction. There are different second phases in the Ni-based superalloys. This chapter details the micro-segregation of these particles and its influence on the microstructure, and mechanical properties are dependent on the process influencing parameters, the thermal kinetics during the process, and the post-processing treatments.

Control-Oriented Modeling and Repetitive Control in In-Layer and Cross-Layer Thermal Interactions in Selective Laser Sintering

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Dan Wang ◽  
Tianyu Jiang ◽  
Xu Chen
Keyword(s):  
High Performance ◽  
Selective Laser Sintering ◽  
Repetitive Control ◽  
Three Dimensional ◽  
Process Variations ◽  
Laser Sintering ◽  
Laser Source ◽  
Cross Layer ◽  
Modeling And Control ◽  
Melt Pool

Abstract Although laser-based additive manufacturing (AM) has enabled unprecedented fabrication of complex parts directly from digital models, broader adoption of the technology remains challenged by insufficient reliability and in-process variations. In pursuit of assuring quality in the selective laser sintering (SLS) AM, this paper builds a modeling and control framework of the key thermodynamic interactions between the laser source and the materials to be processed. First, we develop a three-dimensional finite element simulation to understand the important features of the melt pool evolution for designing sensing and feedback algorithms. We explore how the temperature field is affected by hatch spacing and thermal properties that are temperature-dependent. Based on high-performance computer simulation and experimentation, we then validate the existence and effect of periodic disturbances induced by the repetitive in- and cross-layer thermomechanical interactions. From there, we identify the system model from the laser power to the melt pool width and build a repetitive control algorithm to greatly attenuate variations of the melt pool geometry.

scholarly journals Laser-based additively manufactured polymers: a review on processes and mechanical models

2020 ◽  
Vol 56 (2) ◽  
pp. 961-998
Author(s):  
Roberto Brighenti ◽  
Mattia Pancrazio Cosma ◽  
Liviu Marsavina ◽  
Andrea Spagnoli ◽  
Michele Terzano
Keyword(s):  
Process Parameters ◽  
Mechanical Performance ◽  
Selective Laser Sintering ◽  
Theoretical Models ◽  
Raw Material ◽  
Laser Source ◽  
Mechanical Resistance ◽  
Layer By Layer ◽  
Influence Of Process Parameters ◽  
Mechanical Models

Abstract Additive manufacturing (AM) is a broad definition of various techniques to produce layer-by-layer objects made of different materials. In this paper, a comprehensive review of laser-based technologies for polymers, including powder bed fusion processes [e.g. selective laser sintering (SLS)] and vat photopolymerisation [e.g. stereolithography (SLA)], is presented, where both the techniques employ a laser source to either melt or cure a raw polymeric material. The aim of the review is twofold: (1) to present the principal theoretical models adopted in the literature to simulate the complex physical phenomena involved in the transformation of the raw material into AM objects and (2) to discuss the influence of process parameters on the physical final properties of the printed objects and in turn on their mechanical performance. The models being presented simulate: the thermal problem along with the thermally activated bonding through sintering of the polymeric powder in SLS; the binding induced by the curing mechanisms of light-induced polymerisation of the liquid material in SLA. Key physical variables in AM objects, such as porosity and degree of cure in SLS and SLA respectively, are discussed in relation to the manufacturing process parameters, as well as to the mechanical resistance and deformability of the objects themselves. Graphic abstract

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