2-Part Epoxy Resin molding. Traps/ Tips?

Factual Questions
21

First of all thanks for all of the great stuff here !!! My head’s spinning. ( Partially from the heat, and partially because my Universal Translator fried last week so some of MonkeyMensch’s finest points are lost to me. :wink:

I need extremely light, extremely rigid, drillable. Relatively easy to mix and pour. Takes spray paint REALLY well. Colleagues who have dived into this world recommended 2 part Epoxy.

I’ve abandoned injection molded plastics.

Won’t the Vacuum Chamber kill that problem as long as I use a slow-hardening mix?

Fundamental issues here. We’re talking about an initial production run of 40 pieces, +/— . If it is successful, I’ll be making 100-200 per run.
My colleague who is also an inventor/ designer in our industry did the CAD work on SolidWorks and printed the 1st Prototype for me. It’s a start. It took 23 hours. While I’m not in a hurry, that’s a bit insane. On the OTHER hand, a negative space is required inside of the part and molding may be wicked complex because of that. I’m poking at various solutions to that issue.

So yes, I could 3D print all of them. His printer was about $ 1, 100.00. Outsourcing this job would cost a fortune. I’d buy the printer and run it 24/7 for more than a month. Likely NOT the best was to do this.

I misspoke. Yes, a semi-rigid silicone mold is totally the way to go with this design.

This is in fact a brilliant idea. I don’t care if there’s a seam afterwards. A small orbital sander will beat that, and the part will be 100% painted anyway. I worry most about the strength of the glue.

sljhoei ~bils ldskhguain Cemntte.

There’s no need to belabor the point, you know. :smiley:

Superb question. This will be my….uh….sixth accessory for my little corner of the Film Industry over the last 31 years. They’ve always done okay, some have done amazingly well. This item goes beyond usefulness just to professional Steadicam Operators and into the realm of any Digital Cinema camera setup. I know better than to have stars in my eyes. That said, I’m meeting with a Patent Attorney to do the Search and file a Design Patent Claim to protect this one. So yeah. If it takes off and passes my rigorous and somewhat violent tests in the field, it could do well. Not tens of thousands of units worldwide, but in the best outcome? 200-500 per year.

~ Snip ~ Sounds like my first marriage. :smiley: Based on the contours of this design, I am led to believe that a vacuum chamber used after the pour, and while it slowly sets up, will be successful in the removal of bubbles.

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Then I suggest you work out the economics of the alternative processes on those figures rather than on your initial run.

23

I cannot afford to. The economics of a run like that lead me towards injection molding the items.

An injection mold would be stunningly expensive. If this fails I’m out what- $ 5-10,000 ?

24

I’m guessing for a part of the dimensions you want $10,000 is at the floor of the pricing. See here and here.
(My expertise in the area–a summer in college spent working in a plastics molding plant, making parts that range in size from plastic gears for hand-held drills to Tupperware ladles to one-piece dashboards for Mack trucks. So not on the side of pricing the molds but on the side of seeing what massive complex chunks of steel they are.)

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Yeah. This isn’t nearly so massive, but it has some complex negative space needs.

26

Things like that (not knowing the exact specifics of your part) can be done with a hard mold by having moving parts in it–part is shoved in from the side while plastic is injected, pulled out again when the plastic is released. But I’m guessing that would add A LOT to the price of the mold. Better to break it down into a series of parts that have no undercuts or complex mold requirements and possibly ultrasonicly weld them together. (There was a task when I worked where a part had to have a brass thingy with threads to hold a screw had to be inserted. You put the plastic part on a base, put the brass part on something a little like a drill press, lowered the welder and it vibrated the brass fitting into the cold plastc part like a knife sinking into butter.)

27

I suspect that the epoxy you will be using is more viscous than polyester resin, but I nearly ruined a vacuum pump once when trying to remove the bubbles from a pour in a mold. I filled the mold with resin, there was a neck at the top to provide a bit of excess resin, then put it in the bell jar and started the pump. As soon as the pressure in the jar dropped, resin came bubbling out of the mold and down into the pump inlet, resulting in the oil seal for the pump getting contaminated. As someone else pointed out later, there was a perfectly good vacuum respirator sitting in the cupboard that I should have used instead.

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Translated: Don’t pour the resin in your mouth.