I need some advice on how to cure a problem I am experiencing with
my injected wax models. I am ending up with what appears to be an
"Orange Peel" effect on my models which I suspect is due to
excessive talc as a release agent. However if I use no talc the
models tend to have a wavy look to the wax which is probably due to
the wax dragging against the rubber. I have tried using a silicon
mold release spray instead of the talc but have not been able to
generate models without the wavy effect. My set up is as follows:
Using a low temp injection wax (155 degrees F) 2. Using low
pressure to fill the mold (all detail is filled with very little wax
fanning out into the vents which leads me to believe that the
injection pressure is correct). 3. Using an RTV silicon mold rubber.
I dust the mold with the powdered talc (dusting into the vents) and
then blow out as much as I can. After this I usually make two to
three models before dusting again. The first model usually has a lot
of the orange peel effect. The next model has less, and a third
usually starts to drag in the mold.
I would appreciate it greatly if someone could give me some ideas to
try out to eliminate this problem. The orange peel is somewhat
difficult to remove from the wax and very difficult to remove from
the finished castings.
Not to sound flippant, try bumping the wax temp a bit and if still
problems, bump the pressure. Also you might try a Teflon release
rather than a “standard” silicon release. Lastly, silicon molds
really should not need any release at all. One more thought, try a
different injection wax, our favorite is Serria Red but it is really
not available anymore in the “old” formula anyway. Just a couple of
suggestions.
Ralph, with an RTV silicone mold you should not need spray release.
I would try increasing the wax temp slowly, and or warming the molds
by placing them on top of the injector. Whatever you are using for a
temp. indicator may not be accurate. I would also slowly increase the
pressure. Sounds like the wax is hardening to quickly. Frank Goss
Try something a little different. Use investment instead of talc.
I’ve done several hundred molds over the years and find it works an
order of magnitude better over talc. It’s a lot finer. I make a
ponce of fine cloth filled with investment and gently dab it onto to
mold. Brush are blow off the mold (I do both). I usual reject the
first model, but there after I’m good to go. Any excess investment on
the wax rinses right off. The remaining powder in the mold acts in
vents only and doesn’t remain on the wax.
I use Rio Grand’s pink wax. I inject at a high pressure at the
recommended temperature.
The description of your problems make me think your wax temp is to
cold for your molds. Try increasing your pressure. Then try
increasing the temp a little at a time.
I lay pieces of 14 gage wire in the end of my buckle molds. The wire
is placed almost into the design of the mold. The wires provide an
escape for theair in the mold.
Try something a little different. Use investment instead of talc.
I've done several hundred molds over the years and find it works
an order of magnitude better over talc. It's a lot finer. I make a
ponce of fine cloth filled with investment and gently dab it onto
to mold. Brush are blow off the mold (I do both).
Unless you have great ventilation you are putting a fair amount of
micron size silica in the air you are breathing. This is not good,
it can lead to silicosis.
Good point James. Something I never thought about. A cure would be
to do within my dust collector hood and / or a shop vac. I contend
though, that investment works a whole heck of a lot better than talc.
The point though is to find super fine particles of some sort to use
on the mold. I’ve thought about using the activated carbon powder
used to clean Rhodium solutions but creates way too much of a mess.
I’m open to any other suggestions. I do have a industrial hood I
invest and cast under so not all bad as I now work. Thanks for the
heads up.
Jim is right and talc isn’t exactly healthy either, I switched to
corn starch years ago. At least it is biodegradable and works great
for a mold release as well.