Surface quality evaluation of non-sintered powder layers in Selective Laser Sintering by 3D scanning

Abstract

In Selective Laser Sintering, powders of various materials are deposited layer by layer in order to form 3D objects of complex geometries via sintering or melting by a concentrated laser source. The evaluation of the quality of the non-sintered powder layer is of paramount importance, because it is among the parameters that influence the mechanical properties of the finished part, such as tensile strength and density. In order to monitor the quality of the non-sintered powder layer various methods have been suggested that are either invasive resulting in the destruction of the layer, or unable to provide an accurate measure of the layer’s quality, notably estimation of surface roughness and layer thickness distribution. In this paper, these disadvantages are tackled by a method of optical evaluation of powder surface quality by means of 3D white light scanning. The process is fast, non-invasive and quantitative. A case study is provided to prove its applicability in a prototype SLS machine. The details of the method are explained and indicative surface roughness measurements are given, followed by ANOVA concerning contribution of recoating cylinder rotary speed as main control factor of the surface roughness of the compacted powder layer.