Re: Popcorn RP

From: Tom Richards (
Date: Sat Feb 05 2000 - 23:06:56 EET

But how can we cause the expanding material to stop at the 3D CAD surface of
the part we're fabbing WITHOUT the need for a mold??? If we can answer that
we're on to something great.

At 10:11 AM 2/5/00 -0500, you wrote:
>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
>For more information about the rp-ml, see

For more information about the rp-ml, see

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