Bill,
In our molding operation (high voltage output coils) we have learned several
things by trial and error. First of all do not have perpendicular sides,
use angled or tapered sides (we call it a "draft angle"). Our coils are
"centered" in the mold using either FR4 spacers that have been super glued
to the coil, the coil is mounted by standoffs, or the coil is supported by
the tapered center pin of the mold (which later becomes the hole for the
ferrite core). All of our molds are made out of aluminum except for the R&D
experiments which are made with a Dow Corning Sylastic material. This stuff
works great for a few cycles before becoming too hard to work with. It also
must be compressed with enough force to prevent leakage at curing
temperatures of 60°C. This can cause some undesirable dimensional shift
(read smaller parts) in finished dimensions. Keeping the molds
exceptionally clean and well coating with release seems to help.
Not a whole lot scientific here, but it has been working well for us in our
production quantities.
Phil Nutting
Manufacturing Engineer
Kaiser Systems, Inc.
-----Original Message-----
From: Kasprzak, Bill (sys) USX [mailto:[log in to unmask]]
Sent: Monday, July 16, 2001 11:51 AM
To: [log in to unmask]
Subject: [TN] Recommendations for developing a mold
Hello all,
I am involved with a project that requires that I encapsulate a pc board in
mold so that when completed, it will be a ring with an ID of 1.37" and an OD
of 1.64". The ring will be .13" thick and .35" tall. There will be six, 28
AWG wires exiting the finished potted assembly. The potting compound will be
Emerson & Cumings 2651-40 with Catalyst 11.
I have a basic 3 piece mold that works OK, but the pieces only
reflect what the final product should look like. It takes a little work to
get the mold apart even though mold release is used. The cure for the
potting is 8 - 16 hours at 180 deg F
What I'm looking for is any tricks and hints that should be incorporated
into the mold design that would facilitate easy processing. What I mean is
to make it easier to pour the material, easy to assemble into the mold, easy
to take apart, etc. etc. Right now the whole process just seems to be crude
and messy. Maybe, that's just the nature of the beast.
Any and all responses appreciated. Thanks.
Bill Kasprzak
Moog Inc., Electronic Assembly Engineering
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