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Trouble with a light charm mold

Anybody have any suggestions on wax injection? Does anybody know of any
technical references on mold modification(venting)?

Cutting vents are something you have to let the mold talk to you. When you
inject the mold and pull the wax and it did not fill was it in an area
where the air could not escape? Such as letters (Flat top) in most cases
you have to make a cut in the face of it to get it to fill. At a 90?
intersection. This is where one surface meets another, side to top. Always
use a new or very very sharp blade, one that has not even touched metal
with the cutting surface.In most cases vent to the outside so air can get
on out…But for surface vents only as much as you need. This is very hard
to explain but easy to do. Just do not be afraid to make cuts. As in
casting when you are spruing an item up to cast and the thought of, have I
put enough spruing on this. The Rule of thumb( When in doubt add more)
Also with a small charm you may be putting to much pressure on the out
side while injecting, you may have to let it flash and then do some wax
work… JB.

If the charm has no undercuts and if you are making a lot of them, a
metal mold is the way to go. You will get perfect fill and detail
reproduction and no shrinkage. The plastic patterns produced from a
metal mold will not distort and have unlimited shelf life.

Brett Gober
Freedom Design and Contracting

Venting works in some cases.I do have to agree with JB,on outside
pressure(or in some cases,mold shrinkage or just too thin of a master
pattern).This is particularly true with flat pieces.A little trick you may
want to try is cutting a piece of index card the size of the mold,cut out
a rectanglar piece in the center,leaving a 8 or 10mm border(or a
circle,etc. in a larger size and general location of the piece).Place it
in between the mold plate and the mold,and inject.This will allow the mold
to expand, just a little more.Give it a try.Hope this is of help.

Christian Grunewald
Precision Modelmaking