Layer-by-Layer Strand Deposition Machine: Crump, 1992

S. Scott Crump patented this machine in 1992, US 5,121,329. A computer slices a CAD design into layers. A dispensing head melts a material just above its solidification temperature and lays it down through a small nozzle, one layer at a time, on a base plate that moves under it in X and Y, while the head steps up in Z after each layer. Each layer solidifies almost at once and bonds to the one below. In one version a pneumatic piston pushes a solid rod into the head; in the version built here, drive rollers pull a flexible strand, about 1/16 inch thick, off a reel, so the rate the strand advances sets how much material flows. Any material that bonds to the layer below as it solidifies can be used, such as waxes, thermoplastic resins and metals.