Back to Ganoksin | FAQ | Contact

A thought on mold cutting


#1

You can make mold locks the size of the Rock of Gibraltar and still
have mold lines, sound familiar? One good way to reduce mold lines in
injected waxes is to make sure that the final cuts to the model are
parallel to the mold. If the cut lines around the model slope up or
down, any pressure on the mold will cause the 2 surfaces to slip a
little past each other. The flatter the surfaces next to the model,
the less the slippage.

– Spike Cornelius Portland, Or. RC ArtMetal


#2

Spike, My experience is that there has to be enough cuts to allow
air to escape. I probably have more

cuts in my rubber molds than you have ever seen, and I get great
results. I cast sterling silver for other metal artists, as well as
my own line.I cut the sprue off, grind where the sprue was, and
tumble finish. Very rarely do any pieces have mold lines to remove.
All my customers are happy.

I made an offer on this forum to make molds for 12 people, e-mail
first. If you have mold lines,

I might be able to help. Saves so much time!

I did not understand what you said about parallel to the mold. My
cuts are quite zig zag, about 1/4 inch deep, and act as mold locks.

I have 2000 molds. Most have barely disernable lines.

Richard Hart


#3
One good way to reduce mold lines in injected waxes is to make sure
that the final cuts to the model are parallel to the mold. If the
cut lines around the model slope up or down, any pressure on the
mold will cause the 2 surfaces to slip a little past each other.
The flatter the surfaces next to the model, the less the slippage. 

For the same reason, I like the outer cuts around the mold, which I
do first, to be centered on the molds edge, about 1/8 to 1/4 inch in,
and in that flat plane. Then regular corner mold locks, and various
wavey cuts (to act as additional “surface” mold locks), but then also
the cuts right at the model itself, to be smooth and as level as
possible. Doing this to the outer edges also helps make sure the
mold doesn’t distort along the sides, which would drag the insides
with them.

Peter