It's very hard to say anything without actually seeing the mold(s)
in question. Are these the same molds that worked in the past? If
they are new molds they may need more vents cut or if they are molds
of castings then the shirkage might be too much. If they are the same
are they hard? I'd be very hesitant to play too much with the heat,
burnt wax is no good for anything and then you have to clean out the
whole pot. (I have about 5 years experience doing wax injection BTW.)
Take the time to get to know your wax injector so that is not a
Just in case lets go over the basics.
Always let the injector heat up thoroughly before starting, let the
Always powder the mold, esspecially the vents and release cuts.
(Always get rid of excess powder.)
Always apply even presure to the mold plates (however you choose to,
hands or clamps. There are some exceptions I make for poorly made
molds but those are rare exceptions)
Always hold the mold that little bit longer then you think you need
to. (I recommend books on CD for this job)
Always be sure what you are doing has been consistant for at least
three waxes before trying to diagnose a problem.
Always make sure the wax is solid all the way through before
releasing it from the mold.
How many molds are you trying?
And yes I find the blue plast-o-wax to be a really good work horse
all around injection wax, has good flow into to tight spaces and not
bad for chunkier patterns either.