Fails to mention the P3Steel, an extremely rigid Prusa i3 variant that uses laser-cut steel frame parts. The P3Steel frame, because it is laser-cut from steel, is:
- Comparably inexpensive.
- Extremely rigid and strong.
- Simple finishing (light sanding + acrylic paint).
- Very easy and quick to assemble (less than 30 minutes, using a single small tool).
- Does not require any adjustments.
- All parts fit precisely together, thanks to the precision of the laser-cutting process.
- Can be laser-cut out of stainless or regular carbon steel (3mm thickness), the result being exactly the same.
- Steel is a stable material with zero warping, much less expansion/contraction than aluminum with temperature changes, and does not absorb humidity like wood.
- Finally, I would add that the P3Steel frame is compact and rather good looking, but these are subjective qualities of the design, not really related to the choice of material. Another quality of the P3Steel design is that it requires fewer 3D printed parts compared to the original Prusa i3 design.
Summarizing, I am suggesting here that steel is indeed a very good choice for the frame material for a RepRap 3D printer, provided that the printer's design makes correct use of its qualities as a material, as exemplified by the P3Steel.