The latest version (v5.1) of Sigmasoft Virtual Molding simulation software for injection molding now for the first time allows for simultaneous simulation of the flow of the injected melt and of the cooling media. This improvement is said to make predictions of mold thermal behavior even more precise.
Until now, the cooling channels were assumed to have a uniform heat-transfer coefficient throughout the mold. But ignoring the effects of water flow in complex cooling circuits leads to less accurate molding predictions, according to Sigma Engineering GmbH in Germany (represented here by Sigmasoft Virtual Molding, Schaumburg, Ill.).
New Sigmasoft v.5.1 calculates local cooling performance based on coolant flow rate and clearly identifies areas of poor cooling caused by flow stagnation in the channels. As shown in the accompanying images, the new version shows not only coolant velocity in the channels, but also the local changes in direction of flow in those channels.
One benefit of improved thermal simulation of mold performance is ability to better optimize process setup for maximum productivity. For example, take a case in which the mold-open time for part removal was reduced by 7 sec. That would appear to have a significant potential economic effect for the molder. However, the shorter mold-open time also means less heat radiation from the mold face, so the mold remains hotter when the next shot is injected. That, in turn, requires 2 sec longer cooling time to reach the desired safe ejection temperature. So the net savings is only 5 sec. Further iterations of the simulation would be necessary to determine optimum ratio of mold-open time to cooling time.
Editor PickFor Better Warpage Simulation, Consider the Whole Molding Process
Which way will it warp, and how much? To get an accurate prediction, you have to look at the whole mold and the whole process, over several cycles.