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Expectations from Casters and Cutting rubber molds


I swore to myself that I was not going to respond to any more of
these threads. I was going to be a lurker forever but now I have
broken my word to me for just a quickie. Most people have high
expectations of casters and most contract casters program their ovens
and build their trees to maximize their profit and not necessarily
maximize your quality. Of course they consider it but if it comes to
optimizing their profit or your surface finish being a little rough,
what do you think is going to happen. Usually they don’t have to
finish it so weight in and out does not get fed back to
them. Do you specify the alloy, flask temperature, and metal
temperature for your styles? If possible, it’s a thought but it
would depend on their hardware.

The main reason I am responding to this is about parting lines on
molds and castings. I’ll offer one small trick that I use when I am
teaching a new mold cutter. First I put them in the grinding area
for a week and give them the worst stuff so they can suffer the
cleanup and wasted time. Next, I have them think and discuss with
them where would be a good place to put the parting lines so that it
is most beneficial for the ease and profitability of removal. Then I
have them take a fine tipped permanant marker and draw where they
want the parting line to be on the model before the mold is packed.
This fine black line transfers to the mold rubber during
vulcanization and provides a good guide for the beginning mold
cutter and sometimes for the experienced mold cutter. Then I have
them clean up the castings from that mold. Then I start teaching
them how to pack and cut molds. Some very interesting mold cutting
tricks have evolved from newly frustrated people with no mold cutting

Mold cutting is still one of the things that I really love to do.
Even though I know that it is a science, I still enjoy doing it as an
art form and find it very relaxing. Until I poke my finger that is.
A buddy of mine from Italy (Hubert Schuster) did a very good paper
this year at the Santa Fe Symposium on mold cutting and rubber
properties. It was not an article for the beginner but if you have a
little experience, it is great. You might want to consider buying
the book. It’s available through Rio if your interested.

Best Regards,
J. Tyler Teague
JETT Research