The Sander ModelMaker product is produced and distributed by Sanders Prototype, Inc. of Wilton, NH, USA. Smooth cosmetic surface quality can be achieved by pre-tracing the perimeter of a layer prior to filling in the interior. The supporting wax material is deposited at the same time as the thermoplastic. A schematic is shown below:
Both the thermoplastic material (Protobuild) and the wax support material (Protosupport) are proprietary materials of Sanders.