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2. DIRECTIONS
Spruing: Follow instructions
of the alloy manufacturer with respect to the spruing technique.
Leave at least 1/4-inch space between the top of the pattern
and the top of the casting ring. Also leave enough space between
patterns and also from ring.
Mixing: Mix investment mechanically
under vacuum for 30 to 45 seconds at 400 rpm. Hold the mix
under vacuum for 30 to 45 seconds and then pour into the casting
ring from its sides under gentle vibration.
Paint the patterns with MAXIFILM,
the finest debubblizer for vacuum mixing and investing, to
reduce the surface tension on the patterns.
Metal Casting Rings: Line
the casting ring with a suitable liner. Use thicker or double
liner when casting a longer span bridge. Allow casting ring
to bench set for 30 minutes.
Burnout: Scrape away investment
skin at the top of the ring to allow gases to escape freely
during burnout procedure.
After bench set for 30 minutes place the casting ring into
a burnout oven.
Slow Burnout: Raise temperature
to 1400 F (760 C) to 1700 F (930 C) degree slowly over at
least 60 minutes, longer for larger molds. Use a burnout
temperature recommended by the alloy manufacturer.
Casting: Heat soak the flask
for 30 minutes, longer if there are several flasks in the
oven, before casting. Add 15 minutes soaking time for each
additional flask in the burnout oven. Cast as usual.
In general semi-precious alloys should
be cast at 760 to 840 degrees C, whereas the non-precious
alloys should be cast at 850 to 930 degree C.
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