molding polyurethane?

I would like to duplicate some bushings, about 1" OD, with a ball socket ID,
blind hole.
Can this be molded in polyurethane in a small shop?
I foresee doing about 100 per run.
Rex in Fort Worth
Reply to
Rex B
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Yes, and quite easily, since you can mold it in something as simple as Plaster of Paris.
It's available in a wide variety of hardnesses (durometers), as a two-part thermoset resin system. You'll find suppliers all over the Web.
The resin isn't cheap.
Ed Huntress
Reply to
Ed Huntress
Try BJB Enterprises, lots of products and helpful folks. I have done tons of this, and its not hard at all.
Paul
Reply to
sandiapaul
I assume you're thinking of flexible liquid resin, gravity pour? You may need multiple molds unless you don't need them in a hurry. A fast resin may gel in 2 min. but may not be stable to demold for an hour or so. Are you machining the mold or thinking epoxy or silicone? Silicone molds begin to change after repeated castings, so if tolerences are tight, you may not get 100 from one mold. I think the first step is to determine the properties you require for the finished bushing, then find a resin that satisfies those requirements. Then you will know the viscosity, cure time, and temperature. That will give you a hint at what type of mold is required. Good luck,
Reply to
Billy Hiebert
|I assume you're thinking of flexible liquid resin, gravity pour? You |may need multiple molds unless you don't need them in a hurry. A fast |resin may gel in 2 min. but may not be stable to demold for an hour or |so. Are you machining the mold or thinking epoxy or silicone? Silicone |molds begin to change after repeated castings, so if tolerences are |tight, you may not get 100 from one mold. I think the first step is to |determine the properties you require for the finished bushing, then find | a resin that satisfies those requirements. Then you will know the |viscosity, cure time, and temperature. That will give you a hint at |what type of mold is required. Good luck, |-- |Billy Hiebert |HIEBERT SCULPTURE WORKS |Small Part Injection Molding |
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Thanks for this and the other responses. Looks like it's do-able, and I need to do some research and experiment a bit,
Rex in Fort Worth
Reply to
Rex B
Devcon. $25 seems to be about the minimum for a 1lb kit. Oh, yes, you need to use it quickly after mixing, its very difficult if you decide to use less than the whole 1lb at one sitting, and there does not appear to be any way to stop small bubbles being included in the mix while hand mixing (important if you plan on doing further shaping operations after molding).
I used to spin parts on the lathe. Durometer 90+ cuts pretty nice, similar to plastic.
Reply to
Scott Moore

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