On Wed, 4 Nov 2015 15:25:43 -0700, "Bob La Londe"
wrote:

"Ed Huntress" wrote in message
.. .
On Wed, 4 Nov 2015 12:35:24 +0800, A2 wrote:

On 4/11/2015 10:49 AM, Bob La Londe wrote:
"A2" wrote in message
...
I'm working on a job where we are epoxy encapsulating some electronics.

My question - what to use for a pilot production mold?

Option 1.
---------
Aluminum
CNC cut pockets
Dowels adjacent recess to locate frame that aligns electronics to
0.5mm
Release coated mold - PTFE / Teflon?
Use release agent? Hope to avoid.


I was recently asked to quote a job like this although they used a
different
material than epoxy and injected it. PVA mold release was used. Teflon
pins, and silicone o-rings protected display screens, harness sockets,
and
mounting holes. Aluminum makes a decent mold for this sort of thing,
but
because its rigid you do need to do a little planning to make sure your
part
will demold ok, like tapered sides, etc.

Yep, have heaps of draft on the part.

We were hoping to totally avoid a release agent but we might need some.
I'll check out the PVA release. It looks like its available locally here.

PVA is a pretty standard release agent for epoxy, polyester, and some
other liquid resins. With a new mold, standard practice is to spray or
dip one coat; let it dry; then spray or dip another one. After a few
uses, one coat usually works.

It's a pain in the rear for any kind of production. I've worked with
it on projects small enough to fit in your hand, and as large as
36-foot boats. Hopefully, one of the other solutions will work for
you, but PVA is pretty reliable. It's not perfect, but it generally
does the job.

--
Ed Huntress

It was recently brought to my attention that there is a PVA glue also. Lots
of things I don't know. That was one of them. The person who pointed it
out to me had tried it as a mold release with mixed to poor results on a
printed plastic mold. Appraently the PVA glue didn't stick to his mold very
well. I suspect not much would stick to his plastic mold very well. I
think I would stick with PVA sold as a mold release.

This is one to be careful about. PVA can refer to polyvinyl acetate
(wood glue), or polyvinyl alcohol (a polymer release agent.)

--
Ed Huntress