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Thread: Mold construction

  1. #1
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    Mold construction

    I need to make a mold from a car body, and the body is somewhat fragile. The car body is of thin gauge aluminum construction. My concern is removing the mold without damaging the aluminum underneath. In my experience, it takes some force to get the mold to release.

    Any ideas would be greatly appreciated.

    Thanks, David

  2. #2
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    there was some tai in one of the threads about using silicone for molding a car body, I will try and find the thread for you

  3. #3
    Senior Member MacGyver's Avatar
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    David,
    A fiberglass mold doesn’t need much force to remove as long as you prepare it correctly. I have made molds from original Ferrari aluminum panels without any issues at all. Use many coats of mold wax on the original panels and a fewcoats of PVA. If I think there is any chance of an undercut or a section that will be hard to de-mold I add a flange just to make sure it will come apart easy. Primarily, I just use a quick blast of compressed air to de-mold and they pop right off.
    Last edited by MacGyver; 04-19-2012 at 10:05 AM.

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    get some wide packaging tape not masking and stick it to the panel then glass over it let it go of and remove the mold wont be perfect because of were the tape over laps

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    Thanks for the suggestions. I always use several coats of mold release wax followed by a coat of PVA or PTFE. I have not tried several coats of PVA, and I have not tried using compressed air. I have always made molds off bucks that I felt free to whack away at until the mold came free. I'm running an experiment today with a head rest mold, to see how compressed air works to release the part. I'm thinking 30psi.

    David

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    Hi guys, saw a post somewhere the other day on a fibreglass site, the guy used standard air line clip on fittings, and bonded them into the back of the mold as he laid down the mold, he placed a small piece of tape over the hole to stop the resin from clogging the hole, after its all dry he supplied air to the various air line fittings and the air just pushs the mold away from the original panels, i have not tried it my self but it looked like it should work.
    Regards
    Lambolex

  7. #7
    Senior Member MacGyver's Avatar
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    I have done something similar in the past. Although I just glued little blocks of foam on areas of the part I was copying in areas that were going to be cut out anyway such as marker light locations and etc. Once the mold was made I drilled a inch or so hole into the little block of foam. Hold my rubber tipped air blower tight up against it and shoot in a blast of air. Sometimes it works real well when you are trying to get the mold to let go.

  8. #8
    Senior Member MacGyver's Avatar
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    Quote Originally Posted by #67 View Post
    Thanks for the suggestions. I always use several coats of mold release wax followed by a coat of PVA or PTFE. I have not tried several coats of PVA, and I have not tried using compressed air. I have always made molds off bucks that I felt free to whack away at until the mold came free. I'm running an experiment today with a head rest mold, to see how compressed air works to release the part. I'm thinking 30psi.

    David
    Depending on the original part will determine how much PVA I use. I had copied some OEM plastic parts before and used about 6 + coats of PVA before applying the gelcoat. The PVA keeps the harsh Gelcoat from getting into the plastic and melting it.

    30 PSI will do almost nothing. You will need more like 100 - 130 PSI

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