Moulds in Casting of Plastics and Thermoforming Plastics today are larger serving as substitute material in the field of tooling and prototype parts but are being used as engineering materials in their own lights and in many applications, they are doing better job then any other material could do, some authorities claim that the rapid advancement of plastic tooling would have been impossible without the versatility of the epoxyresin. Plastic tooling offers several advantages over conventional metal tooling. These includes: 1. Lowest cost 2. Less time. 3. Light weight, easily handled and used. 4. Easy modification for design changes and rework.