Coating Vacuum Form Bucks

[ZeroVisibilite]

I'm Having a problem with the paint I used on my vac bucks bubbling and peaing just proir to forming. I use a vertical oven so the heat is blasing down through the plastic onto the buck. This has caused damage to the bucks. every time I form I have to sand the bubbles down smooth.
What are most of you using to prevent this. I know the clam shell guys shouldnt have this problem.
The bucks are made from Pine and MDF with spot filler and bondo under the primer. I used sandable primer.
Maybe some high temp paint would work but I would like to hear from some of you

Greg

 

[tubachris85x]

Im just starting to learn this process of buck making from MDF, but is it really necessary to paint the buck after priming it?

-tubachris

 

[ZeroVisibilite]

I don't know, But the primer is what bubbling on mine. Maybe my oven is just to close to the buck. I just lowerd it about 5 inches. It also has a forming heat so you can keep the heat on when the sheet is beeing pulled. i kept that on this time. That might be the prob. I was just wondering if anyone had any simelar problems
Greg

 

[tubachris85x]

Im sure that if you raise your oven up a bit higher that it will stop having this issue. I dont think also that you really need to have the oven that close either to have good pulls.


-tubachris

 

[drcrash]

I use an aluminum cookie sheet as a heat shield. It reflects IR back up to the plastic. That has the nice side-benefit of giving you double-sided heating.

What kind of primer do you use, that's peeling?

 

[drcrash]

By the way, professionals often make bucks out of epoxy with various fillers and/or finish them with epoxy. Epoxies are generally pretty heat-tolerant. (And some epoxies are very heat tolerant.)

You can make a bondo-like sandable putty with epoxy resin and glass or phenolic microballoon filler, but I don't know where to get pre-mixed stuff like bondo. (Bondo is just polyester resin with microballoons, IIRC.)

 

[CGClone]

I know of several guys who coat their bucks with outdoor grill paint. Its made for high heat resistance and sands well. Just something to think about.