A major MIM processor wanted to produce a case with a long, cylindrical cavity. This cavity was to be achieved by a core in the mold. On the first trials, the core was deforming significantly and perforating the molded case.
A core deformation simulation with SIGMASOFT® was performed to understand the causals of this phenomenon. It was clear that the thermal expansion of the core, as well as the unbalanced pressure along the core, where producing an excessive deformation which compromised the tolerances of the case cavity molded.
Different concepts of tempering for the core where compared. In a first approach, a water tempering was proposed. A thermal simulation demonstrated that while the problem seemed to be reduced, the heat retrieved by the water tempering was still not enough to minimize the thermal expansion. A second proposal was to replace the water for copper inserted under pressure into the core. In this way, excellent contact between the steel core and the copper insert was guaranteed. Water was used on the base of the copper insert. The copper insert, immersed in water, proved to remove more effectively the heat out of the core on each cycle and to minimize the core thermal expansion, so that the part finally had a better dimensional stability.