scholarly journals The Effect of Layer-by-Layer Building in Selective Laser Sintering on the Performance of Polymer-Based THz Optical Systems

2021 ◽  
Author(s):  
Gabriel Moagar-Poladian ◽  
Catalin Tibeica
Keyword(s):  
Selective Laser Sintering ◽  
Data File ◽  
Laser Sintering ◽  
Optical Systems ◽  
Layer By Layer ◽  
Optical Behaviour ◽  
Optical Elements ◽  
Full Wave ◽  
Manufacturing Technologies ◽  
Electromagnetic Calculations

Abstract Additive manufacturing technologies have reached a point where ready-to-use items are directly produced from a PC-stored data file. Among these technologies, selective laser sintering has become a mature technology able to fabricate complex geometric structures using a variety of materials. Despite the versatility of this technology, it also has some drawbacks. One of those limitations, of major concern for building optical elements, is the step-like structure of the surface specific to the layer-by-layer building. In our paper, we present extensive full-wave electromagnetic calculations that consider the effect of those steps on the optical behaviour of refractive lenses made for the THz spectral domain. Our results show that at least up to 1.5 THz, the additively manufactured, stepwise lens behaves very close to its ideally smooth surface counterpart.

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.

Structure and Mechanical Properties of PCL/PG Devices Prepared by Selective Laser Sintering for Drug Delivery Applications

2013 ◽  
Author(s):  
Gean V. Salmoria ◽  
Priscila Klauss ◽  
Carlos R. M. Roesler ◽  
Luiz Alberto Kanis
Keyword(s):  
Drug Delivery ◽  
Selective Laser Sintering ◽  
Rapid Prototype ◽  
Laser Sintering ◽  
Laser Beams ◽  
Powder Materials ◽  
Layer By Layer ◽  
Medical Field ◽  
Rapid Prototype Process ◽  
Drug Delivery Devices

Selective laser sintering (SLS) is a rapid prototype process that creates objects, layer by layer, using infrared laser beams to process powder materials [1–8]. In recent years, the SLS process has shown great prominence in the medical field, and several researchers have conducted studies showing a wide diversity of materials and applications, such as the manufacture of porous drug delivery devices (DDDs) [9–12].

STUDY OF THE PROPERTIES A FRAGMENT OF THE HYDRAULIC CIRCUIT OF THE SPACECRAFT, OBTAINED BY MEANS OF ADDITIVE TECHNOLOGIES

2020 ◽  
pp. 11-19
Author(s):  
I. E. Mal’tzev ◽  
A. A. Basov ◽  
M. A. Borisov ◽  
A. V. Bystrov
Keyword(s):  
Selective Laser Melting ◽  
Experimental Work ◽  
Heat Exchangers ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Additive Technologies ◽  
Laser Fusion ◽  
Layer By Layer ◽  
Laser Melting ◽  
Hydraulic Circuits

The article discusses the course and results of experimental work on the initial study of the possibility of using one of the varieties of additive technologies – the method of layer-by-layer selective laser melting (SLM) in the manufacture of elements of heat exchangers and hydraulic circuits of spacecraft. Traditional manufacturing techniques for hydro-control elements and spacecraft heat exchangers are based on machining and high-temperature vacuum soldering, leading to a long cycle and high manufacturing costs. As an alternative, the method of layer-by-layer selective laser melting can be considered as a manufacturing method using a three-dimensional model of the product and not requiring additional equipment. This method is based on sequential layer-by-layer fusion of a metal powder with previous fused product layers under the action of a laser beam forming a local region of liquid melt. The article describes experimental work to assess the possibility of using the selective laser melting method. Assessed weld-ability of a sample made by selective laser fusion technology with tips made by traditional technology. Directions for testing the method of selective laser sintering on real structures of heat exchanging units of spacecraft have been determined. A technique is proposed and the results of a study of a sample synthesized by selective laser sintering are presented. Based on the results obtained, an analysis is made of the prospects for using this method in the production of elements of hydraulic circuits and heat exchange units of spacecraft.

The Influence of Classical and Modern Manufacturing Technologies on the Properties of Metal Dental Bridges

2013 ◽  
Vol 583 ◽  
pp. 163-168 ◽  
Author(s):  
Mihai Cosmin Cotrut ◽  
Sorin Ciuca ◽  
Florin Miculescu ◽  
Iulian Vasile Antoniac ◽  
Mihai Tarcolea ◽  
...  
Keyword(s):  
Elemental Composition ◽  
Conventional Method ◽  
Corrosion Behavior ◽  
Artificial Saliva ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Parallel Analysis ◽  
Two Samples ◽  
Modern Manufacturing ◽  
Manufacturing Technologies

This paper aims to characterize two dental bridges made from Co-Cr alloy, the first one obtained by the conventional method (casting) and the second one by Selective Laser Sintering technique (SLS). The elemental composition, microstructure, hardness and corrosion behavior in artificial saliva were investigated, allowing a parallel analysis of this two samples obtained with the two methods mentioned above.

Optimization of Process Parameters Applied to a Prototype Selective Laser Sintering System

2017 ◽  
Author(s):  
Abass Enzi ◽  
James A. Mynderse
Keyword(s):  
Mathematical Model ◽  
Surface Roughness ◽  
Response Surface Methodology ◽  
Response Surface ◽  
Crack Width ◽  
Selective Laser Sintering ◽  
Optimal Solution ◽  
Laser Sintering ◽  
Powder Layer ◽  
Layer By Layer

Selective laser sintering is an additive manufacturing technique that uses a high power laser to sinter or melt powder layer by layer to build 3D shapes. This paper focuses on creating a mathematical model of the crack width and surface roughness that occur during the selective laser sintering process. Response surface methodology is used to build and determine a mathematical model. Five variables at five levels are selected: forward step, side step, speed, platform temperature and layer depth. Based on response surface methodology, 32 experiments are used to determine the mathematical model of two selective laser sintering defects: crack width and surface roughness. Next, a genetic algorithm is used to determine the optimal solution to minimize crack width and surface roughness of the part. Results show that the five selected parameters have an effect on the target defects as confirmed by the resulting main effects plots, interaction plots, and contour plots. An optimal set of parameters is determined for future use.

Slot-Die Coating Operability Window for Nanoparticle Bed Deposition in a Microscale Selective Laser Sintering Tool

2020 ◽  
Vol 8 (4) ◽  
Author(s):  
Dipankar Behera ◽  
Daniel Liao ◽  
Michael A. Cullinan
Keyword(s):  
Film Thickness ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Metal Nanoparticle ◽  
Coating Process ◽  
Layer By Layer ◽  
Experimental Conditions ◽  
Slot Die Coating ◽  
Layer Deposition ◽  
Slot Die

Abstract This work seeks to develop a fundamental understanding of slot-die coating as a nanoparticle bed deposition mechanism for a microscale selective laser sintering (μ-SLS) process. The specific requirements of the μ-SLS process to deposit uniform sub-5 μm metal nanoparticle films while enabling high throughput fabrication make the slot-die coating process a strong candidate for layer-by-layer deposition. The key challenges of a coating system are to enable uniform nanoparticle ink deposition in an intermittent layer-by-layer manner. Identifying the experimental parameters to achieve this using a slot-die coating process is difficult. Therefore, the main contribution of this study is to develop a framework to predict the wet film thickness and onset of coating defects by simulating the experimental conditions of the μ-SLS process. The single-layer deposition characteristics and the operational window for the slot-die coating setup have been investigated through experiments and two-dimensional computational fluid dynamics simulations. The effect of coating parameters such as inlet speed, coating speed, and coating gap on the wet film thickness has been analyzed. For inlet speeds higher than the coating speed, it was found that the meniscus was susceptible to high instabilities leading to coating defects. Additionally, the study outlines the conditions for which the stability of the menisci upstream and downstream of the slot-die coater can affect the uniformity and thickness range of the coating.

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.

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 Loose powder detection and surface characterization in selective laser sintering via optical coherence tomography

2016 ◽  
Vol 472 (2191) ◽  
pp. 20160201 ◽  
Author(s):  
Guangying Guan ◽  
Matthias Hirsch ◽  
Wahyudin P. Syam ◽  
Richard K. Leach ◽  
Zhihong Huang ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Surface Texture ◽  
Surface Characterization ◽  
Selective Laser Sintering ◽  
Variable Density ◽  
Laser Sintering ◽  
Layer By Layer ◽  
Optical Coherence ◽  
Surface Profiling ◽  
Loose Powder

Defects produced during selective laser sintering (SLS) are difficult to non-destructively detect after build completion without the use of X-ray-based methods. Overcoming this issue by assessing integrity on a layer-by-layer basis has become an area of significant interest for users of SLS apparatus. Optical coherence tomography (OCT) is used in this study to detect surface texture and sub-surface powder, which is un-melted/insufficiently sintered, is known to be a common cause of poor part integrity and would prevent the use of SLS where applications dictate assurance of defect-free parts. To demonstrate the capability of the instrument and associated data-processing algorithms, samples were built with graduated porosities which were embedded in fully dense regions in order to simulate defective regions. Simulated in situ measurements were then correlated with the process parameters used to generate variable density regions. Using this method, it is possible to detect loose powder and differentiate between densities of ±5% at a sub-surface depth of approximately 300 μm. In order to demonstrate the value of OCT as a surface-profiling technique, surface texture datasets are compared with focus variation microscopy. Comparable results are achieved after a spatial bandwidth- matching procedure.

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