A machined substrate hybrid additive manufacturing strategy for injection moulding inserts

In recent years, advances in metal additive manufacturing (AM) technology make the fabrication of complex conformal cooling channels for injection mould possible. However, poor surface finish, inadequate dimensional accuracy, and high manufacturing costs impede the technology to be adopted in the mould-making industry as an alternative. In this study, a time-efficient machined substrate hybrid AM strategy was developed for the fabrication of injection mould inserts using a hybrid additive-subtractive powder bed fusion process. The primary goal is to reduce AM build and post-processing time. Pre-machined support-free substrate blocks with position alignment and referencing features for subsequent machining operations were used for the additive manufacturing and high-speed machining processes. Four mould inserts, selected from a production injection mould, were redesigned with conformal cooling channels and fabricated in a metal powder bed fusion system using the standard AM practice and the proposed hybrid-build method. In comparison with the standard AM practice, a considerable saving in processing time was attained, but with a slight compromise in tensile strength. Through optical microscopy (OM) and scanning electron microscopy (SEM), a strong fusion bonding can be seen at the interface boundary between the additive powder and machined substrate. This new strategy will provide mould performance enhancement at reduced manufacturing costs for the plastic products manufacturing industry.