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.

Towards in-situ process monitoring in selective laser sintering using optical coherence tomography

2016 ◽  
Author(s):  
Guangying Guan ◽  
Zeng H. Lu ◽  
Matthias Hirsch ◽  
Ruth Goodridge ◽  
David T. D. Childs ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Process Monitoring ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Optical Coherence

scholarly journals Evaluation of selective laser sintering processes by optical coherence tomography

2015 ◽  
Vol 88 ◽  
pp. 837-846 ◽  
Author(s):  
Guangying Guan ◽  
Matthias Hirsch ◽  
Zeng Hai Lu ◽  
David T.D. Childs ◽  
Stephen J. Matcher ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Optical Coherence ◽  
Sintering Processes

scholarly journals In situ process monitoring in selective laser sintering using optical coherence tomography

2018 ◽  
Vol 57 (04) ◽  
pp. 1 ◽  
Author(s):  
Michael R. Gardner ◽  
Adam Lewis ◽  
Jongwan Park ◽  
Austin B. McElroy ◽  
Arnold D. Estrada ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Process Monitoring ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Optical Coherence

3D Human cartilage surface characterization by optical coherence tomography

2015 ◽  
Vol 60 (19) ◽  
pp. 7747-7762 ◽  
Author(s):  
Nicolai Brill ◽  
Jörn Riedel ◽  
Robert Schmitt ◽  
Markus Tingart ◽  
Daniel Truhn ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Surface Characterization ◽  
Optical Coherence ◽  
Cartilage Surface ◽  
Human Cartilage

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 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.

Establishment of Laser Sintering Technique for Titanium Powder

2007 ◽  
Vol 534-536 ◽  
pp. 465-468 ◽  
Author(s):  
Hideshi Miura ◽  
Hiroyuki Maeda ◽  
Makoto Uemura ◽  
Teruie Takemasu ◽  
Masaaki Otsu
Keyword(s):  
Tensile Strength ◽  
Mechanical Strength ◽  
Surface Texture ◽  
Titanium Powder ◽  
Adhesive Bonding ◽  
Bending Strength ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Maximum Tensile Strength

This paper investigates the characteristic of single-layered and multi-layered compacts made by selective laser sintering using titanium powder. The surface texture and tensile strength were investigated by using single-layered compacts. There were few defects in surface of specimen laser sintered in vacuum, and the roughness was smoother than that of the specimen laser sintered in argon. Maximum tensile strength of single-layered compact laser sintered in vacuum was about 200MPa. The shrinkage and mechanical strength were investigated by using multi-layered compacts. There was a unique tendency in the shrinkage of multi-layered compacts, which the density was around 75% and the adhesive bonding was not observed between layers, resulted in 70MPa of maximum bending strength and 50MPa of maximum tensile strength.

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