Anyone casting plastic parts from cnc tooling

[guru_florida]

Hi,

Anyone have experience creating tooling for casting plastic parts, in my case mostly electronic enclosures without using high pressure injection molding?

I am thinking that a resin mixture would work, but I haven't played with it yet. Perhaps I could rig some sort of pressure injection for resin but I dont have the equipment or a big budget for injection molding using typical plastic pellets.

How do we do plastic casting on a budget?

Thanks,
Colin

[graver1]

I'm just passing thru here, but there are many options to get a plastic part w/ 2 part epoxy, urethane,and special mixes. What size parts? How many? molding from a rigid mold requires a lot more care than making a model, casting a silicone rubber mold, and making parts from that I have made molds for architects scale models w/ the rubber molds. There are 2 part epoxies that are almost the same as any of the injectable plastics. Good luck. LL. Dallas.

[blackbeard52]

I agree with graver1...the best bet for this type of non injection on a budget is silicone mold and two part resin...I have seen dinosaur bones (most are cast in museums of this type of material) and very ornate accurate replicas made using resin.

Bob

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[High Seas]

Ditto what blackbeard52 said.
Smooth-On products are great for the mold - and you can find casting resins on eBay pretty cheap too.
I have used cnc'd masters (plug) for several silicone molds and then cast the product in resin.
Jim

[guru_florida]

Thanks to everyone so far for thier feedback.

I have some of the good quality silicone rubber mold material laying around. It is good for things like bones, or say in my case a few years ago, small robotic parts. However, now I want to mold a few electronic enclosures, about 30 or so. The size would be no larger than 5 x 8 inches. The issue is I suspect the flexible mold material can *not* produce the thin walled, hollowed out enclosures well. Am I right or wrong?

If a flexible silicon mold can produce thin walled enclosures maybe that is the way to go. I can produce my positive master on my cnc machine and make a few flexible negative flexible molds from that and maybe 10 positive enclosures from each of the flexible molds before they become too warped.

On a side note, someday I would like to make an injection molding machine. I finished my CNC machine, I have plans to make a PCB fab station with through-plating, the injection molding would make a nice trifecta! My long term goals are prototype and small-run fabrication cell/modules.

Colin

[blackbeard52]

I typically make a master then paint on the silicone to be sure to get all the detail. once that is done (1/4 - 1/2 inch) I lay a fiberglass mothermold on that to support the silicone. it is very cost effective this way and I can replicate anything to basic tolerances. But I have not tried to make anything that required a close tolerance. I however did produce a camera housing and it came out very well and closed to a very tight fit and all was needed was a water seal for outdoor use... made about 200 of these right out of the mold. they come out a little hot so you could even fast form the fit over a mandrel or tolerance master. smooth-on is a product I have not used but is very compatable with what I did use. the company that manufactured the resins and mold materials of that day are out of the business and on other ventures. They used to be called Sinair out of Nashville, TN.

Oh and on the mothermold it can be reused to make additional castings

Bob

[guru_florida]

Thanks for the info blackbeard. I will give that a try. If you made 200 camera housings then it should work for me no problem. The tolerances are not close really, I am sure no more than what you needed for your enclosures.

[blackbeard52]

the great thing is I made a wood master and painted the exterior with a textured paint to hide inperfections/repairs/mods. Came out very professional...I sold these to a large internet video company using it for traffic monitoring... they were in the field for more than 2 years before they upgraded to video streaming. I had made a screw on lens cover and utilized a dome from one of those cheap security cameras. It had a screw on ring. I cut the thread and hot glued it to the master and after molding the housing it screwed on with no problems. These were in direct weather conditions from 90+ degrees to 15 F and never failed. Ok I am blowing my horn but it was a great solution all the same.

Bob

[guru_florida]

Ok I am blowing my horn but it was a great solution all the same.
Bob

Ahhh, I love to hear it!!! I hope I get similar results.

Colin