31 Aug 09 14:00
I am designing a 4 cavity mold. The parts are rings that are 1.5" OD, 1.25 ID by .375 thick molded of 325 valox (PBT). My customer would like to see the gates on the ID of this part. He machines these and from his experience if we were to subgate on the OD there can be a visual mark where the gate was after machining.
I am not sure what the best approach is to solving this problem.
I am wondering if I could use a 3 plate mold and drop down to the center of each cavity with a sprue gate and then from there use a small runner to a subgate into the ID of the part but I have never seen this approach used and I am afraid it would give me problems because of the 3 required drops in size to get to the part (nozzle, sprue gate, and subgate). Is this a legitimate concern?
I could use a Hot Runner Mold, but am afraid the cost would be too much.
The other option that I see is a conventional runner with an edge gate on the OD of the part. This gate could be bigger and thus possibly would not show the marks after machining. I am guessing that the material is compacting at the gate and this could be reduced by adjusting the molding process.
Does anyone have any thoughts or suggestions?
SW 2008 SP3.0