If there is a plastic out there that I like, but I just want it in a smaller size than anyone else makes it...how would I go about doing that? I figure I would need a custom plastic mold? Would there be some kind of way to just mold the big size plastic and then shrink it somehow?

You can make a master like you want then build yourself a mold.  You use several different materials for the master.  Molds can be made from silicone, fiberglass resin, and plaster of paris just to name a few.  There are bait making sites where you can get lots of info about how to do it.

4 hours ago, Jig Man said:

You can make a master like you want then build yourself a mold.  You use several different materials for the master.  Molds can be made from silicone, fiberglass resin, and plaster of paris just to name a few.  There are bait making sites where you can get lots of info about how to do it.

 

Thanks for the reply.. I understand I can make a mold. Like the silicone ones for example, I could just drop a plastic in there I like, create the mold, and then create exact copies......but how do I make exact copies of a 5 inch craw to a 1 inch craw for example? 

14 hours ago, Jonas Staggs said:

Would there be some kind of way to just mold the big size plastic and then shrink it somehow?

You'd basically have to create a new master for the mold.

 

I use to make copies of parts for plastic scale models using molds and casting plastic - to create something identical in looks but smaller, I'd have to hand-carve a new master. Mold making materials aren't designed to shrink to a smaller size.