Homebrew PCBs

Hi,

I'm fabricating my own vacuum chamber right now.  I'm using a 
pressure cooker and 2 venturi pumps (PneuAire) connected to a 
ordinary shop air compressor.  I'm waiting for a reply from Maesco 
for prices on their vacuum dial indicators.

The 9L. pressure cooker was on sale at Canadian Tire for $55, about 
the same price on EBay for a used unit.  Once I perfect the process, 
I'm buying a 2nd pressure cooker, cutting the bottom on the 1st unit 
and having it welded on top of the 2nd one.

That way I can expand my capacity and retain the existing plumbing.  
The pumps and dial indicator are mounted on the existing holes in the 
lid.

The nice feature of the pressure cooker is the quick release 
mechanism.  I was considering cutting & welding 2 barbecue tanks 
together, but I'd have to fabricate a sealing section.

About degassing liquid plastics, unless I read wrong you have 2 
alternatives (I'm not sure if this applies to other liquids):

1. place the unpoured mix in a vacuum chamber.
2. place the cast along with the poured mix in a high-pressure 
chamber.

Robert
:)

(sorry if this info was already discussed, I haven't read the entire 
thread and I'm searching for Silkscreen information, this topic just 
caught my eye)

Note: www.SmoothOn.com is an excellent source is materials for 
casting.  I use liquid plastic #326 for my casings.


> you don't vacuum the mold, you need a small vacuum chamber in which 
you  
> put the container of silicone or whatever you want to use to cast. 
the  
> vacuum makes the bubbles HUGH and causes them to rise to the 
surface,  
> effectively de-gassing the liquid. then you take the liquid out and 
cast  
> with it.
> Of course you can also vacuum the un-cured mold and pattern just 
after  
> casting if it fits into the chamber.
> 
> You can join <http://groups.yahoo.com/group/casting/> for more 
information.
> I was looking into it a short while back, but decided it is too 
expensive  
> and i have enough stuff to do right now. But it opens a lot of  
> possibilities...
> 
> ST