Thermal optimization of deterministic porous mold inserts for rapid heat cycle molding

In this work a porous mold insert with a regular deterministic geometry was developed and its design was optimized by means of numerical simulations to maximize the heat exchange in Rapid Heat Cycle Molding (RHCM) between water and the cavity surface, without impairing the mold structural integrity. Compared to previous fluid convection technologies, such as steam heating and pressurized water in metal foam inserts, the optimized porous inserts performance is significantly higher, having a maximum heating rate of 7 °C/s and a mean heating rate of 6 °C/s. A testing mold with the optimized porous inserts was developed to validate the numerical simulations and to characterize the RHCM influence on the surface quality of fiber-reinforced polypropylene parts. Parts surface roughness decreases increasing mold temperature, packing pressure and injection rate. Moreover an increase of mold temperature attenuates the effect of injection rate on roughness. Therefore, with this RHCM technology it is possible to obtain a high quality fiber-reinforced part even at low injection speed.