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Painting fiberglass plug / mold for forming styrene?

 
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RFC
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Joined: 22 Aug 2011
Posts: 19
Location: Western PA

PostPosted: Wed Sep 07, 2011 5:35 pm    Post subject: Painting fiberglass plug / mold for forming styrene? Reply with quote

Hello,
I am new to vacuum forming but understand the process.
I would like to home produce / thermoform .020" flock covered styrene to make display case liners that are about 8" x 12" and 1" deep.
Using a sample liner that I wanted to duplicate, I made my first plug ( terminology?) by layering the inside back of the original with Tiger hair fiberglass.
Removed the plug and now filling the voids and air pockets with glazing putty.
What I would like to know is after the plug is filled and sanded, can I paint with lacquer primer progressively sanding with finer grit paper
to achieve a semi glossy surface?
Would the last step be to wax the plug before using? Will lacquer stand up to the heat of styrene forming?
Thank you for your help, Bob
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jdougn
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Joined: 18 Mar 2009
Posts: 697
Location: Louisville KY area

PostPosted: Wed Sep 07, 2011 7:55 pm    Post subject: Reply with quote

Hello Bob & welcome to the forum.

There are other guys here with a lot more experience but I'll throw in my .o2 here. Most paint and primer will not handle a lot of heat and will pull off on the back of hot plastic. For what you're doing you might try using straight bondo body filler since it will handle heat and sand smooth. In my limited experience, the resin used with regular fiberglass will get soft when it gets hot. Also, if the glazing putty you're using is a pre-mixed product then I've had bad results with it too. The stuff I tried was a dark red, much darker than regular bondo. However, I form 3/16" ABS which takes a lot of heat and cools slowly so it puts a lot of heat into the mold.

Which side of the plastic is going to be the finished surface? The side against the mold or away from the mold? If the finished surface of the plastic is against the mold then the mold does need to be flawless. Hot plastic will pick up the slightest imperfection even the grain in plywood or dust specks will show up.

I've not used a kitchen oven to heat plastic so others will be able to answer that one much better.
hope this helps,
DougN
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RFC
Newbie


Joined: 22 Aug 2011
Posts: 19
Location: Western PA

PostPosted: Wed Sep 07, 2011 8:15 pm    Post subject: Reply with quote

Thanks Doug,

I was afraid you were going to say that. I have my mold filled with dark red glazing putty and several coats of gray lacquer primer. Yes, it looks great, but I had a feeling the hot plastic would melt the paint. Guess I can sand it all off back to the fiberglass. I wish there was something to spray the mold with that would not melt.

And to answer your other question, my good side of the molded part is away from the form or plug. There will be depressions to hold tools. The good side is flocked.

I will wait to see what others come up with. Thanks, Bob
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jdougn
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Joined: 18 Mar 2009
Posts: 697
Location: Louisville KY area

PostPosted: Thu Sep 08, 2011 9:33 am    Post subject: Reply with quote

I'd also be real interested in hearing how the flocked plastic form for you. It's not something I've done.
dn
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