We initially created these molds to create plastic body parts. We had issues heating large pieces of plastic and instead tried using fiberglass. Sadly we didn't use a proper mold release and the parts were permanently bonded with the fiberglass.
A friend of mine wanted to do a Super Smash Bros. cosplay, and we decided a Rob the Robot would be a nice touch. We threw this together over 2 weekends, so it wasn't particularly durable. It was made from a Powerwheels go-cart and foam core panels. The arms raised and lowered and rotated at the shoulders.