Numerical and experimental evaluation of a conformally cooled H13 steel injection mould manufactured with selective laser melting

Additive manufacturing (AM) techniques such as selective laser melting (SLM) can enable the construction of injection moulding (IM) tools with conformal cooling channels that significantly improve performance through higher cooling uniformity and reduced cycle times. Design of IM cooling systems is typically achieved using commercial IM numerical modelling software originally developed for conventionally cooled mould designs. However, the accuracy of IM modelling software in predicting the performance of SLM manufactured tools with conformal cooling, across a range of moulding materials and processing conditions, has not been thoroughly evaluated in the literature. Furthermore, the SLM manufacturability and mechanical properties of tool steels typically applied in IM, such as AISI H13, are not well documented. This work addresses these deficiencies through the following: quantification of SLM H13 material properties, in particular fatigue strength which has not been previously reported; design and manufacture of a mould tool with easily exchangeable conventionally and conformally cooled inserts; and subsequent experimental validation of IM simulation software predictions under a range conditions. Result of mechanical testing showed SLM H13 parts to offer lower mechanical properties in the as-built condition compared to conventional materials; however, these increased substantially following residual stress reduction with heat treatment. Evaluation of the temperature prediction accuracy of IM numerical models showed generally high accuracy for conformally cooled SLM tools, although marginally lower when compared to conventionally cooled moulds. The outcomes of this work offer designers typical material property data for SLM manufactured H13 tooling, as well as an indication of the expected prediction accuracy of current commercial IM simulation software when applied to conformally cooled SLM tooling.