Automatic cooling channel design for injection moulds

Abstract

During the injection moulding process, local differences in pressure and temperature lead to different shrinkage over the part. This inhomogeneous shrinkage can lead to internal stresses, which are compensated by an undesirable warpage of the part. A sophisticated design of the cooling channels can avoid most of these problems. In previous research, it was shown that a locally adjusted temperature distribution on the cavity surface leads to less warpage of the part. In order to achieve this temperature distribution, an adapted cooling channel design is necessary. This design process is not possible with an analytical calculation but is the result of an iterative and numerical optimisation process. In this paper, a simulative approach for an automatic cooling channel layout via an inverse heat conduction problem is presented. Based on previous results, the methodology is adapted to three-dimensional problems. This approach brings the local heat and cooling demand of the part in equilibrium based on the postulate of a locally homogeneous material density. By this methodology, a proper cooling channel design close to the mould surface is determined. Simulations show a significant reduction of warpage by at least 22 % which will be validated by experimental results.