Hi Ray,
I’ve used the Model Maker for a few years and know how
frustrating the first few tries can be. One of the tricks to
casting a patterned sheet is spruing- use one sprue for every
half-inch of area. It sounds like a lot of cleanup, and it is,
but it will help to get the casting complete. Also, it sounds
as if your flask is getting some thermal shock; heating or
cooling too fast. You’ll probably find that thin wall castings
are more susceptible to thermal shock, so try extending your
burnout time to produce a smoother thermal curve.
Last, remember " Cups up", as I heard recently in this forum,
when investing. My production crew loved that term. The small
open areas in the pattern act just like large ones in a regular
casting, so be sure to leave a way for the gases in the
investment to escape when investing. Oh, I have never gotten a
decent casting from the polymer which can supposedly be burnt
out. It cracks the investment every time, aside from smelling
horrible during burnout. Good luck, hope this helps. Metalsmth