One of the risks of reworking any type of mold — whether it’s vacuum or injection mold or wax injection — is the risk of scraping your original tool. Making sure you've got good information to start is paramount.
Pat Barrett from Sherpa Design and Applied CAx explains from our CMM and programming room a procedure we use to help rework mold tools.
On this particular project we were provided 4 of the same mold cavities and needed to rework them to put in some inserts and add additional features that weren't there before.
We were given the original molds and the CAD data they thought the molds were built with. The molds were built somewhere else, a long time ago, so first thing we wanted to do was verify that the mold data matches the CAD data and that's what we did on our CMM. In doing this we discovered there was about a 50000th discrepancy on the outside surfaces of the tool as compared to the CAD data.
We take our CMM data and the numbers go into NX, where we do all of our CAD and CAM work, and we modify the original CAD data which we were given a STEP file. NX's tool set and synchronous modeling allows us to quickly and easily move surfaces, and update them. Any NC toolpaths that we've built onto those surfaces are going to automatically going to update as well.
Because we have 4 of these tools to do, we run a verification inspection on the CMM, go in and update our synchronous modeling features, repost our NC code, and then we're off and running building the inserts and modifying these tools.
The first one of course is always a little dicey, but the next 3 are moving along real well, and thanks to NX CAD and NX CAM this project is going to go ahead very well.