Process repeatability and sources of error in indirect SLS of aluminium

Purpose - The purpose of this paper is to investigate the accuracy and repeatability of the indirect selective laser sintering of aluminium process. Design/methodology/approach - This work characterised the shrinkage of indirect SLS aluminium parts during the various stages of production. Standard scale parts were measured using a Giddings and Lewis co-ordinate measuring machine in both the green and infiltrated condition. Findings - The experiments conducted show that most accuracy is lost during the furnace cycle and that the greatest loss of accuracy occurred in the Z dimension. Additionally the position of parts within the part bed in both X, Y and Z is shown to influence accuracy, with smaller parts being built closer to the edge of the bed later in the build. These results have been interpreted as being a result of the phenomenon of "Z-growth". Finally, the research shows that the overall accuracy of the indirect selective laser sintering of aluminium process is comparable with many existing processes such as investment casting. Originality/value - Before any new material can be accepted, there is a need to not only fully characterise the dimensional accuracy attainable, but also to gain a thorough understanding of the processes that contribute to the inaccuracies. This paper addresses this need.