Investigation into the shrinkage in Z-direction of components manufactured by selective laser melting (SLM)

Abstract

The change in phase of the material from powder to liquid and then to solid is accompanied by a shrinkage in the metal volume, which becomes an inherent restraint during the selective laser melting (SLM) process. In order to improve the accuracy of SLM-processed parts, a three-factor, three-level, and multi-response experiment was designed; the influence of the process parameters like laser power, scanning speed, and layer thickness on the relative density and shrinkage ratio in Z-direction was investigated by the response surface methodology, and then optimized process parameters were derived from a multi-objective optimization. The result indicates that the laser power has a major effect on the shrinkage ratio in Z-direction, followed by scanning speed and then layer thickness. Then the dimension and shape accuracy of SLM-processed parts can be improved by the dimension compensation, which can help to limit the accuracy in Z-direction in ±0.8 %, and roundness of column and hole in ±1 %. Based on this study, the relationship between process parameters and accuracy in Z-direction of SLM-processed parts was revealed and thus, corresponding measures can be taken to improve the accuracy.