Owing to the fact that moulding methods are not suitable for prototyping due to the high cost of tooling, plastic and rubber prototyping is sometimes seen as a specialist service - however, it is absolutely necessary if manufacturers want to avoid costly errors at a later stage. Prototyping allows you to test the feasibility of a design before stumping up for expensive tooling, ironing out any potential problems before the project goes into full production.
Prototyping of plastic and rubber parts is often carried out via machining, or even 3D printing. In other instances, less costly methods of plastic forming - such as vacuum forming - may be used. The techniques used to produce prototype plastic and rubber components will depend on the design requirements and the material.
Some companies will offer both plastic & rubber prototyping as well as full production moulding, meaning that you can keep the entire process with one supplier. Others will offer prototyping as a specialist service.