Re: Popcorn RP

From: Jim Mallos (
Date: Sat Feb 05 2000 - 17:11:08 EET

Michael Hirschmann wrote:
> Thanks, I enjoyed that. There is a well established technology that is
> currently used for the production of expanded poly styrene parts (Styrofoam)
> that mimics popcorn. Pellets of styrene are impregnated with a propellant
> (pentane), and are then expanded by heating (usually with steam). Shape is
> determined by constraining the pellets in a mold, causing fusing at the
> expanded cell borders of the hot plastic.

It's worth adding that the same puffing process and various propellants
can be used with any thermoplastic. Nature puffs the lightweight
boulders that eject from volcanoes by the same process.

  Wonder where that might go for
> fabbing large Styrofoam parts?

If this does prove to be a practical RP process (a big "if"), it will
always have the advantage that objects are programmed when they are much
smaller than their final size.

This would not just apply to things we think of as being made from foam.
Many familiar large objects have a low bulk density. Someday it might be
possible to "puff" a car from a plastic kernel small enough to fit
inside another car's trunk---the famous scene in "Goldfinger" played in

Jim Mallos

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