Research on impact behaviour and silicon insert fracture phenomenon in microinjection moulding

Silicon insert is a promising tool for microinjection moulding (MIM). However, its fracture problem induced by impact in MIM creates a bottleneck for application. The purpose of this paper is to investigate the impact behaviour in MIM and the effect on the fracture of silicon inserts. The finite element method is utilised to calculate the crack propagation of silicon inserts with pressure load and thermal load in the MIM process. The simulation result shows that the crack propagation is more easily induced by the increase of pressure load, while the temperature change has little effect on the crack propagation. An experimental platform, including a novel rotatable insert mould, is developed to investigate the dynamic pressure in the MIM process. The result shows that both the maximum pressure and the maximum loading rate occur in the initial period of MIM process. It indicates that the silicon insert is more prone to fracture at the beginning of the MIM process, and spatial pressure peaks are observed in the cavity as well. The nearly consistent distribution between the peak positions and the insert fracture zones shows that the pressure distribution is quite relevant to the fracture of the silicon insert. The result is helpful because it reveals the fracture phenomenon of silicon inserts.