I have a Rio Vacuum/casting machine which has one table for both
investing and vacuuming. The pad to be used for investing came with
an off- center cross shaped slit cut into it.
When de-airing the bowl of investment I was told by one person to
put the bowl in the center of the pad. As the slit is to one side of
the pad, this means that the pad and the bowl are over the hole in
the caster which is used for vacuuming.
Another person told me that this is incorrect placing of the bowl,
and that it should be placed off-center on the table, and that I
should cut an additional slit in the center of the pad so that there
will not be any build up of vacuum under the pad. In other words,
there should be two slits in the pad–one off-center, and the other
directly in the center.
My questions boils down to — What is the purpose of the slit? and
Should the bowl be placed over the slit?
Before I do any unnecessary surgery, or ruin my caster I would like
some expert advice.