Standard atmospheric pressure is 14.7 PSI.  Standard barometric pressure=20
is 29.92  inches of Hg.  Both are specified at 0=B0 C at sea level.  24 o=
r=20
25 inHg is fairly easy to accomplish But I doubt you would need to be=20
that low for vacuum forming.

We got called to repair an old vacuum sealing machine several years=20
ago.  The guy's machine was a flat table with the work area having holes=20
in it as was described by someone else.  The product was laid out on a=20
cardboard sheet with holes punched in it then plastic sheet=20
(polyethylene?) was stretched over a frame above the work area.  Then a=20
heater came on to heat the plastic until it drooped, at which time the=20
frame was lowered and the vacuum pump came on.  It seems the vacuum pump=20
wasn't much more than a squirrel cage blower like those from an old=20
furnace.  Check the cold air return on your furnace.  It has a pretty=20
good air flow, and they're not real expensive...especially if you can=20
find one that was a scrapper.

The heater was an IR type like we now see in some warehouses or other=20
large volume work areas.

REB

Shawn Wilton wrote:

> 8x2.  You mean one of those massive propane tanks people in the=20
> country usually have?
>
>
> David P Harris wrote:
>
>> Shawn-
>> 28 mmHg  with a 8x2'  propane tank --- the initial rush is to make=20
>> sure a good seal happens. He said for smaller parts with polystyrene,=20
>> you can use a old barbeque propane tank with a new valve on it and=20
>> attached to a air compressor.
>> No pictures, but essentially a flat square board with lots of holes,=20
>> a frame around it, and a chamber below attached to your vacuum.  Set=20
>> the plastic on top and then heat with a heat gun or hair dryer until=20
>> sagging, then let 'er rip.
>> David
>>
>>
>

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