Impact of Micro Milling Strategy on the Demolding Forces in Micro Injection Molding

The quality and the integrity of complex 3D micro injection molded parts can be influenced by the efficiency of the demolding phase. During demolding, the forces that take place at the component-tool interface due to adhesion and friction need to be overcome. Deep cores are a particularly critical geometry for the ejection, because of the shrinkage of the polymer onto the mold. These conditions are exacerbated in the case of multi-layer microfluidic devices, where several arrays of through holes are required and they cannot have draft angles. Decreasing the ejection forces can significantly contribute to improve ejection systems design and help guaranteeing the structural integrity of the moldings. In this work, the influence of mold micro milling strategy on the demolding forces was studied, using a specifically designed geometry of the cavity. The relation between mold manufacturing strategy and the demolding force profile was studied by varying process parameters. The results provide useful information regarding the effect of the micro milling strategy on the demolding conditions in micro injection molding.