Thermomechanical Evaluation of Thermoplastics Injection Cycle Effects in Aluminium Moulds Using the Finite Element Method

The mould stiffness becomes more relevant during the packing stage, therefore predicting the mould mechanical behaviour when submitted to the loading cycles of the injection process is essential to the tooling project. Some loading sources are more likely to damage the tooling, such as the holding pressure, the clamping force, and the thermal stress. Considering the mould thermal cycle is important, evaluating heat exchange by conduction between the part and the mould, the free convection with the surrounding air and the forced convection with the cooling fluid. The aluminium’s thermal and mechanical properties are significantly different than steel ones, which change the injection cycle and its capability to resist the injection load cycles. This justifies the need to evaluate the differences in the use of both steel and aluminium materials in the mould design. This paper proposes numerical simulations making use of finite element method to assess the effects of the injection moulding loads on aluminium moulds, through outputs such as temperature profile, the stress state, and parting line openings. The results are compared to numerical results obtained for steel moulds. The results show that the difference between the mould’s materials properties significantly changes the injection moulding conditions and the mould design, particularly the cooling system efficiency. These aspects are fundamental to make guidance to required modifications on the aluminium moulds, allowing the mould mechanical project and cooling system optimization to perform the best in terms of the part quality and process productivity.