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Re: Fabricating plastic parts?

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4/27/2000 5:40 PM

Re: Fabricating plastic parts?

You know, the moment I used the word "shrinkage", George Costanza was EXACTLY what came to mind. I thought I'd allude to it, but then figured it might not enjoy widespread comprehension and be misinterpreted in some way. Apparently, Steve, we think alike. Now all I'm waiting for is someone to talk about their floating bridge and note that "it...moved". Or talk about replacing pickups and mention that "he took....IT...OUT".

But enough about this. These pretzels are making me thirsty. :-)

:-)

4/27/2000 5:08 AM
Don Symes	Is there still such a thing as a vacuuform?

4/28/2000 8:45 PM

Polyester casting resin has little or no shrinkage, or those rattlesnake heads and scorpions would look even sillier. Cheaper than epoxy, too.

However, you can get "Sculpy" or "Fima" plastic modelling clay in crafts stores (in a zillion colors, even) mold it to shape (like with a rolling pin) and once it's to shape, bake it in an oven to harden it to plastic. Again, little or no shrinkage.

"Milliput" modeller's compound is a kneadable epoxy based two part intended for accurate molding.

Most of the kneadable two part repair epoxies in hardware and auto stores will shrink little or none, as they're intended for uses like patching gas tanks and boat hulls underwater. Can't have shrinkage there!

With a vaccum pump (I got mine at ebay, $30), a wooden plug form and a heat lamp, you can heat/vaccum form acrylic sheet as accurately as you have the patience for.

You can make a styrofoam male part, cover it with fiberglas cloth and epoxy from either a boat repair kit or a rusted fender repair kit, then eat away the foam with lacquer thinner, then trim and spray paint the resultant tray.

Actually, my preference is to machine a female mold from tool steel, put a sheet of aluminum and an ounce of C4 on it, and lower it into a well. When you ignite the C4, the aluminum is formed *very accurately* into the shape of the mold.

This last requires a large garage, though. Depending on where you live, there may be local ordinances or special permits required, so check with you local authorities first. ;-)

;-)

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