Marshall Brain's Blog

Have you ever been in one of those situations where you have a plastic part and you need to make a copy of it? For example, I have a toy that contains a plastic gear that is trashed (several teeth broken off). The toy contains another gear that is identical and is in good shape. How do you make a copy of the good gear so you can replace the bad gear?

The answer is: Make a silicone rubber mold of the good gear, and then cast a copy of it using urethane resin.

Here's a nice set of videos that shows you the entire process:

Casting plastic parts with silicone molds