Homebrew PCBs

Hi, i can't really see a point in using vacuum in two rigid flat
surfaces. Two glass parts seems to be used just with springs without the
need of vacuum. Professional vacuum tables use glass under and a really
well design plastic above, its not entirely flat, has a matrix of small
relief squares, its a strong plastic but will perfectly shape to your
board. Maybe can be bought as spare part for this machines.

The vacuum table i have used (professional) work with a pressure of
-0.7bar (1 bar = 100kPa ~ 1atmosphere, Pa is SI unit) , but half seems
enough. To lift the plastic cover we had to wait until the pressure came
to zero again!

About the calibration hole, can also be done regulating the power or rpm
of your vacuum motor pump. A hole from the vacuum table to pump (series)
will not work, but from pump to free air (parallel) yes. (professional
regulators have a weight above/closing this hole, and the pressure
depends on this weight). One source of vacuum pump could be a hot air
solder station, once i opened mine and it has two ends to fit rubber
tubes on the air pump, one air out other air in, but the stupid Chinese
manufactor broke the air in end...

Simao

On Sun, 2009-03-22 at 07:16 +0000, warrenbrayshaw wrote:
> DJ Delorie wrote:
> 
> > 
> > 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.
> > 
> >
> 
> Sounds like you need a calibrated hole :)
> 
> Just like a domestic vacuum cleaner, have a hole in the vacuum pipe to
> reduce the effective vacuum.
> 
> Warren
> 
> 
> 
> 
>