Modeling of the ultrasound-assisted ejection in micro injection molding

In this paper, an ultrasound-aided ejection system was designed and tested for various polymers and mold topographies. The use of ultrasound vibration aims at decreasing the ejection friction by reducing its adhesion component, which is controlled by the real contact area developed in the filling phase of the injection molding process. The experiments indicate that the ultrasound vibration reduces the ejection friction up to a maximum of 16%. The effect depends on the polymer used and it increases for rougher mold surface. Moreover, the dependence of ejection friction on mold surface roughness, melt viscosity and elastic modulus at ejection was modeled using the experimental data.