Vacuum Forming Question

[elkamino]

For anyone into vacuum forming I need your help. I have a pretty awesome set up for vacuum forming however, I still have trouble pulling the eye sockets on a helmet. I've drilled relief holes but the center points above the nose keep coming out weak. I have since gone to using a positive mold to push the eyes in but requires a two person operation.

 

BTW..when I go back and heat it with a heat gun during suction, the pull actually gets worse.

 

Any engineers have input?

[Chefhawk[501st]]

Any chance of some pictures of what you are talking about to make things clearer???

 

 

 

 

 

cheers

[elkamino]

In the center where the eyes come together, they never fully define leaving only a shallow recess where they come to a point. Sorry for the poor picture.

[journeymanprotector]

I don't have experience vac-forming myself, but here's an idea if no one has a better one:

 

Maybe put a relief hole in the center of that center area? It'll create a dimple, but you can fill the pulled piece with a tiny amount of bondo or something. If you plan to repaint the helmet, no one will notice.

 

If you're not repainting it would be trickier, unless you could match a gloss white paint to it.

 

Probably not incredibly helpful, but thought I'd throw it out there.

 

Phil

[elkamino]

I don't have experience vac-forming myself, but here's an idea if no one has a better one:

 

Maybe put a relief hole in the center of that center area? It'll create a dimple, but you can fill the pulled piece with a tiny amount of bondo or something. If you plan to repaint the helmet, no one will notice.

 

If you're not repainting it would be trickier, unless you could match a gloss white paint to it.

 

Probably not incredibly helpful, but thought I'd throw it out there.

 

Phil

 

I am planning on using ABS so a filler would not work, however, the ABS does not show a dimple if I use up to a 3/32 drill bit. Not a bad suggestion Phil, thank you.

[Chefhawk[501st]]

Sounds like your over heating the plastic and its stretching over that point.

How do you judge temperature, is by time or by droop/sag?

 

Also plastics like paint vary slightly , even from the same manufacturer.

 

Try different times and compare the results.

Also make the holes a touch bigger (eye sockets)toward the centre ridge.

 

 

 

keep us posted.

 

hope this helps

 

 

cheers

[elkamino]

I made some progress last night. I was actually under heating the plastic. As for judgment, I just eye up the sag for heating time.

 

Right now I am testing using styrene which shouldn't pose as much of a problem as it is turning out to be. ABS and styrene are basically doing the same thing.

 

I really think this is a engineering issue related to where and how large the relief vents are. It seems the smaller the relief vent the better the suction...I guess this relates to the equation PV=nRT.....man I should've paid more attention in class.