View Full Version : Help/suggestions for undercut tooling

10-30-2013, 10:32 AM
Hi all.

I need to form a part with a pretty serious undercut, and I was hoping someone could give me some tips and/or suggestions on tooling design to accomplish this.

Here is a picture of the part in question:


The edge you see there protrudes about 3/4" from the part.

I have some ideas about how to go about making the tool, but I don't want to go and re-invent the wheel only to discover there was a much better/simpler way to do it.

Basically, I'm thinking of designing the tool so that the pictured section is detachable and comes off with the part when I pull it, either via some sort of rail system or with a few strong magnets.

Does that sound practical? How do you all go about dealing with undercuts? Any and all tips are welcome.

Other relevant info:

- the tool will be made out of RenShape tooling board
- the part will be formed using 0.125" Kydex 100
- machining the undercut isn't an issue, only finding a way to allow the formed part to be removed vertically (our ovens pull the tool straight down out of the formed part)

Thanks in advance!

p.s. Is "undercut" the correct term for this sort of thing?

10-30-2013, 10:55 AM
OP here again.

New idea which might be much simpler: what if I just made the whole tool detach from the vacuum box? The shape of the part is such that I think it I could just hinge the far end and that would allow the part to release. Any thoughts?


11-01-2013, 08:45 PM
if that is the whole part in the drawing then you can. just hinge the non undercut side so the undercut part lifts up with the plastic which changes the angle and comes right out of the plastic. I've been able to get a 1 inch+ undercut part off of my friends molds that way.

edit just re-read your post and yep pulling straight up will require hinging to get the material off the mold but you'll have to check and see how high the mold goes when the material is being removed so that you don't have an issue with the material holding frame and or shuttle if it's automatic. hopefully it pulls down enough for the part to come out and the mold to drop back down into position

11-29-2013, 12:25 AM
This part isn't trapped. All you need to do is establish the proper plane to get it off the tool. Slide the part left and the undercut clears the tool then lift.. You get there by rotating the tool so the flat end of the part is either on or quite near the parting plane AND so the undercut face of the part has a prolongation under it connecting it to the parting plane. Mold the part, release the clamping frame, pop positive pressure on the mold and the part blows off while moving to the left... Lets keep it simple...