There is no restriction on the methods and materials used to make a prototype in unit R108.
The prototype can be made from modelling materials (e.g. modelling foam, balsa wood), or more substantial engineering materials (e.g. metals and plastics). It is important however that candidates demonstrate a range of prototype-making skills using tools and equipment safely, following a production plan.
Where rapid prototyping is used to make parts of, or even the whole prototype, then it is essential that candidates show the process of using CAD/CAM to program the machine along with safe setup and operation.