There is a machine called a Thermo form machine which was designed
to copy pages of Braille.  I figured that it was very similar to a blister
packer because it did much the same thing.  It had a perforated table
with a vacuum pump under it, a large clamp which went around the periphery
of the work, and an oven which did look a lot like a toaster oven.  The oven
would reach a preset temperature and start cycling on and off.  There was
a timer control which one set that controlled the amount of, shall we say,
cooking time for the plastic.

        Using the machine involved placing the master on the perforated
screen, a blank sheet of plastic over the master and then locking the clamp.
It was then necessary to slide the oven over the work and wait until the timer
timed out.  At that moment, the vacuum pump started and sucked the now
almost molten plastic down over the master.

        The trick was to set the timer just right or you either got no
copy at all (too little heat), or a badly wrinkled sheet (too much).

        I used this machine in the early seventies so my memory of some
details is a little fuzzy.  This type of system, however, would be a piece
of cake for a PIC.  I remember that the timer in the system I used was a
conventional mechanical device with a synchronous motor so one would have to
make a 60 or 50 HZ version depending upon where it was used.

        When it was tuned just right, it captured amazing surface detail
of whatever was under the sheet.

Martin McCormick