Evaluation of the effects of the print parameters in additive manufacturing process for dimensional control of printed parts using a traceable coordinate measuring machine

Abstract

Until now, selective laser melting (SLM) process has become more extensive as one of the useful additive manufacturing (AM) techniques. During the course of AM process, there are a number of print parameters (e.g., laser power, hatch spacing, scanning speed, powder layer thickness, scanning strategy, beam offset, X-axis scaling , Y-axis scaling and Z-axis scaling and etc) affecting the dimensional accuracy of final part printed. Among these parameters, four print parameters (beam offset, X-axis scaling, Y-axis scaling and Z-axis scaling) have direct effects. The aim of this study is to investigate the influence of the four SLM print parameters on dimensional accuracy of parts fabricated from Inconel 718 alloy. Specific artefacts were designed for AM process and related measurements were conducted using a high accurate coordinate measuring machine (CMM) traceable to the International System of Units (SI) of metre. The CMM measured results were analyzed to demonstrate how the four print parameters result in dimension variation due to adjustment of the print parameters. It was found both external and internal diameters of the artefact are changing in an opposite direction with the beam offset setting. The measured results show: (1) there is a good linearity of the dimensions (6 mm to 30 mm) to a beam offset within ± 0.1 mm. The 0.1 mm change of beam offset could systematically introduce 0.2 mm change in external and internal dimensions; (2) both linear dimension and form error (e.g., cylindricity) are sensitive to the X-axis scaling , Y-axis scaling and Z-axis scaling. The dimensional accuracy of AM printed parts could be optimized by the adjustments of these setting parameters in AM machine.