Question for our plastics or molding experts - epoxy casting molds

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.
Option 2. --------- Plastic mold CNC cut pockets in a ~30mm thick slab Dowels adjacent recess to locate frame that aligns the electronics. Is there a plastic that epoxy won't stick to - no release agent needed? Nylon? UHMWPE? Maybe $$ Teflon? I imagine a silicone or urethane mold may not be rigid enough.
Any suggestions? Recommendations? Thanks!
Background: Prototypes have been cast in a mold made from epoxy and a aerosol mold release used. It works ok, we ended up making the mold 2 parts as the completed parts were a little hard to remove.
*The electronics is sat into a 130mm x 50mm x 20mm (5"x2"x3/4") mold *Their is heaps of draft on the mold for easing release. *Epoxy poured into the mold. *After 24 hours they are de-molded.
*These will be made in batches of say 30 to 100 at a time. *We are happy Doing say 6 at a time with a 24 hr turn around. *Mold may be 6 units wide or 6 individual molds.
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On Tuesday, November 3, 2015 at 8:04:14 AM UTC-5, A2 wrote:

I would try UHMWPE. It will be almost as good as Teflon as far as getting the mold to release the part. And it is quite a bit cheaper than Teflon. I would think it would be good for production molds.
Dan
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On 3/11/2015 9:17 PM, snipped-for-privacy@krl.org wrote:

Thanks, I'll chase up a sample of UHMWPE and do some adhesion / release tests.
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The machining marks (undercuts) will make the part want to stay in the mold even if it doesn't stick. Polishing will be a lot of work. If the mold material is rigid then be sure to have a healthy draft angle (maybe 4 degrees or more).
--sp
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Best regards,
Spehro Pefhany
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On 3/11/2015 10:40 PM, Spehro Pefhany wrote:

I'm starting to think aluminium might be the best as we know we can get a polished finish. Not so sure we can get this with UHMWPE.
I was wondering if aluminium molds are routinely coated with something like that used on non stick fry pans.
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On Tuesday, November 3, 2015 at 11:30:55 PM UTC-5, A2 wrote:

You might try UHMWPE anyway. You have to have very sharp cutters and take off about .1 mm on the final pass. And you may be able to flame polish the UHMWPE. Unfortunately flame polishing oxidises the surface and that is not good for releasing the part from the mold.
UHMWPE is a lot cheaper than aluminume, so it might work out. You can find heaps of posts about using PE for molds on the internet all posted by people with more experience that I have.
Dan
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Polyvinyl acetate = Glue Polyvinyl alcohol = Mould release
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Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
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