Different processes are optimized for different materials. A carpenter, a machinist, and a bronze sculptor have different tooling and workflows.
Also, we need to distinguish between 2D, 2D+1, and 3D form factors for the end object.
- flat sheets of wood into more-or-less 2D FlatPack parts: rotary tool, laser, hand tools
- long chunks of lumber into grid beam: drill press
- scrap wood, dead trees, etc. into lumber:
- Metal: rotary tool, plasma, electro-chemical etching, non-ferrous metal casting
- PCB: rotary tool, innumerable -- Automated Circuitry Making lists a few techniques
- Soldering parts onto a PCB is much easier with a HotplateReflowTechnique -- rather than with any kind of toolhead-mounted soldering iron.
- Plastic: reprap, rotary tool, laser,
- Shape Deposition Manufacturing is much easier if you have 2 toolheads attached to a single machine so you can quickly alternate back and forth between them -- a milling head and a plastic extruder -- rather than 2 separate machines, a mill and a plastic extruder.
- flat sheets of acrylic: Laser Cutter
- Bronze, aluminum, silver, and similar metals: rotary tool (maybe), lost wax casting, High Temperature Metal Casting
- Epoxy-Granite: cold casting
- Glass: lost wax casting
- Pewter: low temperature Casting
- Wax/Plastic: RepRap, rotary tool, hand tools, casting.
- liquid photopolymer can be converted into solid plastic using DLP or laser
- thin sheets of paper, aluminum foil or other metal foil, plastic film, sliced-up recycled soda containers, etc. can be converted to arbitrary 3D shapes using laminated object manufacturing (LOM) ... Compliant Linear Motion Mechanism 1 and FlatPack mention such lamination ... other discussion of lamination on the RepRap forums ...
MaterialsScience discusses the various materials people have printed from a RepRap, or at least tried to print. Frame material discusses the various materials people have considered using to build a RepStrap.