small parts with reaction injection molding (RIM)

[faings70]

Can very small parts be made with reaction injection molding?
For example, very small gears (5mm in diameter).
What about small enclosures the size to a cigarette box?

They have to be fairly precise (dimensionally stable) in order to preserve snap fitting.

I may need to manufacture a large variety of parts (but with low volumes for each part) injection molding may not be cost effective and manually casting may be too slow.

Will low pressure or high pressure RIM be best?

Thanks.

 

[MikeHalloran]

When last I tried it, decades ago, RIM couldn't reliably reproduce features smaller than ~3mm in size, and required secondary operations to get a nice finish. The gears you've shown would lie outside its capabilities AFAIK.

Tiny parts like that would be producible in a small mold made of steel or maybe aluminum. I don't ordinarily recommend 'insert molds', but they might be appropriate for your variety.

I used to partner with a guy who did low volume stuff for reasonable prices with small simple molds and precise choreography, but he's not available anymore.

I suggest limiting yourself to nylon or acetal.


Mike Halloran
Pembroke Pines, FL, USA

 

[Demon3]

Have you considered 3D printing the parts? It's well suited to small production runs. See:

http://www.stratasys.com

and

http://store.makerbot.com/

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

http://www.phantomplastics.com

Webinars on plastics, fillers & impact modification:

http://www.plastictraining.com

 

[cowski]

If the parts are simple with small production runs, you may also consider

http://www.protolabs.com