Re: Popcorn RP

From: Jim Mallos (
Date: Mon Feb 07 2000 - 04:06:54 EET

Lex Lennings wrote:

> The idea is fascinating, a great deal of which is caused by the visionary
> subject line that you use: one day RP will be just as cheap, easy to use
> and generally accepted as popcorn.

Dear Lex,

A bubble growing from a microscopic laser-made defect has a natural
leveraging of means that might bring that day closer. The computer and
laser, in effect, only scribble orders when programming foam---the grunt
work is done later by ordinary oven heat and the energy of compressed

For some guestimates assume we wish to program foam by laser pitting a
100-micron thick polymer film (which will then be wound up for puffing.)
Assume the pattern of pits averages 100 micron spacing on a square
grid---this gives 1E9 pits/liter before puffing. If we puff to 5:1 in
volume, the foam has 200E6 pits/l.

Assume each pit has a volume equivalent to a cube 10 microns on a side,
or 1E-9 cm3. Assume the laser energy cost of such a pit is 1000 cal/cm3
( 4200 J/cm3.) Each pit then requires 4.2 E-6 J, and the 200 million
pits in a liter of foam requires 840 J.

Under these assumptions a 1kw laser pulsed at 200 MHz could program foam
at one liter per second. Ordinary-sized parts could be programmed in a
few seconds (of course the heating/puffing step would take much longer.)
This is about three orders of magnitude more productive than methods
that make the laser do the actual work.

Jim Mallos

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