Good to know.  Going to have to give this a shot.  Sounds like fun after 
all.  Anyone else building one of these things?  If so, contact me off list.

-Shawn

Falcon Wireless Tech Support - KF4HAZ wrote:

> 14.x PSI is normal atmospheric pressure here on earth, x varies slightly with altitude and baro.
> So that is the limit, vacuum is usually expressed in bar or  inches mercury.
> 1 bar=14.6psi=30inches mercury if memory serves correctly this would be the theoretical absolute vacuum.
> In practice if you can get 29 inches vacuum you are doing very good.
> 
> KF4HAZ - Lonnie
> 
> ----- From: "Shawn Wilton" <shawn@
> 
> 
>>David, can you get some pictures from your buddy, perhaps a few more 
>>details.  What sort of vacuum are we looking at?  100's of PSI's, or what?
>>
>>-Shawn
>>
>>David P Harris wrote:
>>
>>>My friend does plexiglass forming.  Wooden frame, kitchen oven element 
>>>for heater.  Large air-tanks connected to a pump.  These are pumped out, 
>>>then a valve opens and the vacuum forming happens very quickly. David
>>>
>>>Roland wrote:
>>>
>>>
>>>>>BTW, the hard parts of vacuum forming seem to be the matter of an 
>>>>>oven big
>>>>>enough for the work and creating a vacuum source (or is it sink?) with
>>>>>enough volume to draw down the material before the material cools out 
>>>>>of the
>>>>>plastic condition...
>>>>>  
>>>>
>>>>
>>>>Hi
>>>>I've watched vacuum forming done, and it was a very simple set-up. They
>>>>were forming polystyrene(not foam!)
>>>>The positive/pattern was simple wood fabrications, and there was no oven,
>>>>rather a big element and a few fans blowing the air down. I think the
>>>>vacuum part was just an industrial blower, as a sucker.
>>>>
>>>>The force required will depend on the temperature, depth of draw 
>>>>required,
>>>>thickness of sheet, resolution of pattern. Although a nice convoluted
>>>>surface can be obtained, the edges always pose a problem, same with
>>>>fibreglass moulds. Trimming them to an exact size, and polishing to hide
>>>>the work, is almost impossible.
>>>>
>>>>
>>>> 
>>>>
>>>>
>>>>>A home vacuum cleaner arrangement is not really up to the task. 
>>>>>Besides, my
>>>>>earlier experiments with home vacuums lead me to believe a lot of air 
>>>>>FLOW
>>>>>is essential to avoid toasting the motors.
>>>>>  
>>>>
>>>>
>>>>maybe a powerful blower and a venturi will be better??
>>>>
>>>>Regards
>>>>Roland Jollivet
>>>>
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>>>> 
>>>>
>>>
>>>
>>>
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