Im working on a mold that i had some chips comming out of it so i filled it with filler and sanded it smooth.im wondering can i hit that small spot its like 1/4 wide 2in long with some spray can paint and sand it with like 1200 sand paper and then wax and release it.the parts are gettin painted when their done but im just worried about it pulling up.
thanks
personally, i sanded the filler, then waxed it and used it like that. im afraid that if i paint just one spot, the paint either wont sit down, because of waxes or “too smooth areas” around, or will unstick when demoulding.
Body filler might be ok on a mold that won’t be used too much.
It would be better to use gelcoat to fill that area, and sand it smooth. You’ll get a consistent finish, and the patch will have the same CTE.
CTE? wazzat?
I repair my epoxy molds with epoxy surface coat; then i repair my polyester gel coat molds with polyester tooling gel coat.
I’ve used it in molds before, and had poor results.
It seems that it’s just too pourous, no matter how much it’s polished, no matter how fine it’s sanded, and no matter how much it’s waxed, it’s going to have release issues, for me, at least.
Coefficient of Thermal Expansion.
Different materials have different properties. So use the same material.
Sweet - A forum member in my State.
I’ve used bondo a few times on molds but the molds were only being used once or twice, low temp cures 150F max and the parts were being painted. Now i didn’t have any issue with that but i have seen molds were it was used as a long term fix and it eventually pulled out. the thing you have to remember about body filler/bondo is that after it see’s a little heat it will shrink with cause you to have cracks that need to be filled constantly. Like someone said earlier, for a cheap fix the best thing to do is to take some gelcoat mix it with some cavosil till it’s the consistancy of penut butter and use that just like you would the bondo except there’s no need for painting just sand and polish. Now if you don’t have any gelcoat or your mold wasn’t made with gelcoat you could use epoxy resin in it’s place. Ok thats my 2 cents
I have also had trouble in the past with rattle can paints reacting with the gel coats.Better to use 2 pack or something like polyester lacquer,durabuild etc
Wow I will have to try that!
I usually sand the defect so I get a clean area, wipe it with aceton, add few drops of gelcoat inside the defect (same color as the mold’s) and tape it on top of it with clear tape in order to get a straight edge with less sanding. I previously used filler but it didn’t last for too long… Hope this helps!
^^ but I would also drill a small holes thru it, drip gel coat into the hole until it comes out the back, tape over it and then fill the top up and tape over that too…acts like rivet.
I always used different color gels for the repair so I always know where the repair was. Is there a particular reason why you use same color or is just your preference?
Good point, but in my classroom we only use black tooling gel coat so we knew that it was mainly used for tooling…plus black tools shows better on sprayed on color gel coat for thickness and eveness…at lest for open molding.
No special reason,just for looks, knowing where the repair was helps though 