scholarly journals Numerical Model and Experimental Validation for Laser Sinterable Semi-Crystalline Polymer: Shrinkage and Warping

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1373 ◽  
Author(s):  
Jiang Li ◽  
Shangqin Yuan ◽  
Jihong Zhu ◽  
Shaoying Li ◽  
Weihong Zhang
Keyword(s):  
Heat Transfer ◽  
Selective Laser Sintering ◽  
Dimensional Accuracy ◽  
Polymeric Materials ◽  
Crystalline Polymer ◽  
Raw Material ◽  
Critical Issues ◽  
Mechanical Models ◽  
Powder Fusion ◽  
Polymer Shrinkage

Shrinkage and warping of additive manufacturing (AM) parts are two critical issues that adversely influence the dimensional accuracy especially in powder bed fusion processes such as selective laser sintering (SLS). Powder fusion, material solidification, and recrystallization are the key stages causing volumetric changes of polymeric materials during the abrupt heating–cooling process. In this work, the mechanisms of shrinkage and warping of semi-crystalline polyamide (PA) 12 in SLS are well investigated. Heat-transfer and thermo-mechanical models are established to predict the process-dependent shrinkage and warping. The influence of raw material- and laser-related parameters are considered in the heat-transfer and thermo-mechanical models. Such models are established considering the natural thermal gradient and dynamic recrystallization, which induce internal strain and volumetric change. Moreover, an experimental design via orthogonal approach is introduced to validate the feasibility and accuracy of the proposed models. Finally, the quantitative relationships of process parameters with product shrinkage and warping are established; the dimensional accuracy in part-scale can be well predicted and validated with printed parts in a real experiment.

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

scholarly journals Selective Laser Sintering (SLS) and Post-Processing of Prosopis Chilensis/Polyethersulfone Composite (PCPC)

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3034
Author(s):  
Aboubaker I. B. Idriss ◽  
Jian Li ◽  
Yangwei Wang ◽  
Yanling Guo ◽  
Elkhawad A. Elfaki ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Particle Distribution ◽  
Low Cost ◽  
Selective Laser Sintering ◽  
Single Layer ◽  
Dimensional Accuracy ◽  
Laser Sintering ◽  
Raw Material ◽  
Post Processing ◽  
Prosopis Chilensis

The range of selective laser sintering (SLS) materials is currently limited, and the available materials are often of high cost. Moreover, the mechanical strength of wood–plastic SLS parts is low, which restricts the application of a SLS technology. A new composite material has been proposed to address these issues, while simultaneously valorizing agricultural and forestry waste. This composite presents several advantages, including reduced pollution associated with waste disposal and reduced CO2 emission with the SLS process in addition to good mechanical strength. In this article, a novel and low-cost Prosopis chilensis/polyethersulfone composite (PCPC) was used as a primary material for SLS. The formability of PCPC with various raw material ratios was investigated via single-layer experiments, while the mechanical properties and dimensional accuracy of the parts produced using the various PCPC ratios were evaluated. Further, the microstructure and particle distribution in the PCPC pieces were examined using scanning electron microscopy. The result showed that the SLS part produced via 10/90 (wt/wt) PCPC exhibited the best mechanical strength and forming quality compared to other ratios and pure polyethersulfone (PES), where bending and tensile strengths of 10.78 and 4.94 MPa were measured. To improve the mechanical strength, post-processing infiltration was used and the PCPC-waxed parts were enhanced to 12.38 MPa and 5.73 MPa for bending and tensile strength.

Formability of the Layer Additive Ceramic Part

2008 ◽  
Vol 594 ◽  
pp. 241-248 ◽  
Author(s):  
Fwu Hsing Liu ◽  
Yunn Shiuan Liao ◽  
Hsiu Ping Wang
Keyword(s):  
Surface Roughness ◽  
Laser Scanning ◽  
Selective Laser Sintering ◽  
Single Layer ◽  
Dimensional Accuracy ◽  
Scanning Speed ◽  
Laser Sintering ◽  
Single Line ◽  
Laser Scanning Speed ◽  
Silica Slurry

The material in powder state has long been used by selective laser sintering (SLS) for making rapid prototyping (RP) parts. A new approach to fabricate smoother surface roughness RP parts of ceramic material from slurry-sate has been developed in this study. The silica slurry was successfully laser-gelling in a self-developed laser sintering equipment. In order to overcome the insufficient bonding strength between layers, a strategy is proposed to generate ceramic parts from a single line, a single layer, to multi-layers of gelled cramic in this paper. It is found that when the overlap of each single line is 25% and the over-gel between layers is 30%, stronger and more accurate dimensional parts can be obtained under a laser power of 15W, a laser scanning speed of 250 mm/s, and a layer thickness of 0.1 mm. The 55:45 wt. % of the proportion between the silica powder and silica solution results in suitable viscosity of the ceramic slurries without precipitation. Furthermore, the effects of process parameters for the dimensional accuracy and surface roughness of the gelled parts are investigated and appropriate parameters are obtained.

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.

scholarly journals Optimization of SLS forming parameters in the dimensional accuracy of formed parts

2021 ◽  
Vol 233 ◽  
pp. 01069
Author(s):  
Hong ZHU ◽  
Gaoyan HOU
Keyword(s):  
Process Parameters ◽  
Selective Laser Sintering ◽  
Dimensional Accuracy ◽  
Scanning Speed ◽  
Axis Deviation ◽  
Reference Standard ◽  
Optimal Process ◽  
Molded Part ◽  
Formed Part ◽  
Powder Forming

In selective laser sintering powder forming, the performance and dimensional accuracy of the formed part are affected by the process parameters. Different materials have different process parameters, and there is still no reference standard for PA materials. To solve this problem, in response to this problem, PA2200 material was selected, and the influence of scanning interval and scanning speed on the dimensional accuracy of the formed part was analyzed. Through theoretical analysis and experiments, the optimal process parameters were obtained. The best combination of parameters is a scanning speed of 4000mm/s, a scanning interval of 0.5mm, and the size of the molded part has a X-axis deviation -0.35%, a Y-axis deviation -0.4%, and a Z-axis deviation -0.25%.

scholarly journals Epoxy resin filled with primary and secondary raw material – useable in agriculture

2014 ◽  
Vol 60 (No. 4) ◽  
pp. 165-171 ◽  
Author(s):  
P. Valášek ◽  
J. Kejval ◽  
M. Müller
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Epoxy Resin ◽  
Filler Particle ◽  
Polymeric Materials ◽  
Raw Material ◽  
Nano Particles ◽  
Inorganic Particles ◽  
Increase Wear Resistance ◽  
Secondary Raw Material

Hard inorganic particles in the interaction with polymeric materials increase wear resistance. Also reactoplastics are suitable for filling with micro- and nano-particles for a purpose of some mechanical properties optimization. The paper compares chosen mechanical properties – hardness, wear resistance and tensile characteristics of epoxy resin filled with artificial corundum with various middle particles sizes and their ratio combination. Mentioned systems can be used in a sphere of the agricultural production at renovation of machine parts, they can serve for creating resistant layers on machines, floors and grillages at the same time. The aim of the carried out experiment is to compare the properties of reactoplastics filled with a primary and secondary raw material and to define an optimum ratio of the filler particle size relating to a given mechanical quality. The artificial corundum was chosen as the primary material, the waste corundum from the process of material mechanical treatment was chosen as the secondary one.    

scholarly journals Waste Electrical and Electronic Equipment: A Review on the Identification Methods for Polymeric Materials

Recycling ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 32 ◽  
Author(s):  
Grigorescu ◽  
Grigore ◽  
Iancu ◽  
Ghioca ◽  
Ion
Keyword(s):  
Polymeric Materials ◽  
Industrial Applications ◽  
Complete Characterization ◽  
Electronic Equipment ◽  
Raw Material ◽  
Identification Methods ◽  
Material Resources ◽  
Characteristic Values ◽  
Materials Used

Considering that the large quantity of waste electrical and electronic equipment plastics generated annually causes increasing environmental concerns for their recycling and also for preserving of raw material resources, decreasing of energy consumption, or saving the virgin materials used, the present challenge is considered to be the recovery of individual polymers from waste electrical and electronic equipment. This study aims to provide an update of the main identification methods of waste electrical and electronic equipment such as spectroscopic fingerprinting, thermal study, and sample techniques (like identification code and burning test), and the characteristic values in the case of the different analyses of the polymers commonly used in electrical and electronic equipment. Additionally, the quality of the identification is very important, as, depending on this, new materials with suitable properties can be obtained to be used in different industrial applications. The latest research in the field demonstrated that a complete characterization of individual WEEE (Waste Electric and Electronic Equipment) components is important to obtain information on the chemical and physical properties compared to the original polymers and their compounds. The future directions are heading towards reducing the costs by recycling single polymer plastic waste fractions that can replace virgin plastic at a ratio of almost 1:1.

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