At 11:54 AM 3/22/2009, Steve wrote:
>The plastic would tend to seal down and prevent a good vacuum from
>being pulled all across the surface,
i've never had a problem with that in over 20 years, but since my
vacuum tables have a grid of holes across the entire surface, the
vacuum path is along the entire perimeter of the board. but i will
say that professional screenprinting exposure machines have a piece
of string about like a venetian blind cord anchored near the vacuum
outlet hole and this is laid across the substrate out of any artwork
path and acts like a wick or 'tunnel' for the air to escape during
the pump down. these professional machines (i own several different
kinds) have a highly flexible rubber blanket that pulls the substrate
against the thick rigid glass. Oh, i also use a vacuum pump from an
old offset press, but it'll take a decent time interval to wear out a
motor in a shop vac and you can find them cheap all the time in yard
sales/goodwill stores.
William Alford
GI Motility Medical Research Page
http://alford.grimtrojan.com/ [Non-text portions of this message have been removed]