LOL you are not supposed to suck the glass down!
The vacuum exposure units I have seen use a flexible clear plastic
cover (like clear plastic tablecloth) to hold down the films.
Usually it's like this (top to bottom):
upper part (hinged)
{lid
UV tubes
glass
}
Vacuum cover
{thin frame with plastic film, hinged separately.
}
lower part (fixed)
{glass with hole in corner for vacuum
UV tubes
bottom of case
}
You slap on the film stack, flip down the vacuum cover, engage the
vacuum, check alignment, flip down the top part with the upper
exposure tubes, and start the timer.
For a vacuum pump you can use an old fridge compressor (get it at the
recycling place already disconnected). It has very decent vacuum. A
diaphragm pump (fish tank) would likely also suffice.
ST
On Sun, Mar 22, 2009 at 3:44 AM, DJ Delorie <dj@...> wrote:
>
> Just a note about today's task. I scrounged some tubing and made some
> adapters, got some scrap rubber gasket material, and converted my UV
> exposure box to vacuum hold-down. I used a 1/4" wide strip of rubber
> sticky-backed gasket material around the edge, drilled a hole in from
> the front and up into the space within the gasket, and made a wooden
> adapter (stopper) to connect the shop-vac to the tubing.
>
> I didn't feel much "suck" on the end of the tube with my finger, but
> the first time I hooked it up and tested it I saw the glass bow in so
> much I feared it would break! I just need to find out if I can run
> the shop vac with low air flow for the 5.5 minutes it takes to do an
> exposure.
>
> What I decided to do is keep a stack of card stock (half-sheets) to
> prop up the board to keep it just a little below the height of the
> 1/8" gaskets, so that the glass doesn't bend that much, but not so
> much that the film isn't held tightly to the board. I'll have to run
> some tests with a dial indicator.
>
> I can't find my vacuum gauge, though. I was thinking of making a new
> adapter that allowed some air to flow through to the vacuum to keep it
> from overheating, but without knowing how much vacuum it's drawing I
> have no way of knowing how much extra flow I can afford. Anyone else
> have any idea how much vacuum is needed to hold the film down, or
> other tips?
>
> Now that I have a temperature controlled laminator to put films on (it
> wants 240F, not the 320F the laminator used to do) and a vacuum to
> hold them down, maybe tomorrow I'll try making some spirals too :-)
>
>
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