Screws vs Belt Drive
Screw drive is a different technology all together than belt drive. Screw drive is more difficult to implement, and would not be part of a reduced construction set based on the belt-driven Universal Axis, thus screw drive is not recommended for OSE's minimalist construction set approach. The Universal was intended as a 3 axis machine with Prusa bed configuration (moving bed) for education and production of small parts. That is no good for real industrial productivity. If you are interested in a real production machine, you need to get away from a moving bed and go to a frame with gantry like D3D Pro. On a prusa style printer, once you get about 6-8" tall, you can't print any more because the thing wobbles too much. So you would not be able to print tubing or plastic lumber. We are moving up to 3 meter tall machines - so the Universal geometry of moving bed is not applicable there. The other disadvantage of threaded spindle is they are not scalable linearly in cost, so it will get expensive for larger machines, and you cannot use 4 of them on larger machines because they bind up if they are not perfectly lined up. So it's a more difficult technology to work with. The whole Prusa/Lulzbot geometry of moving bed is just a bad design - not suitable for high performance industrial productivity, but only hobby and limited production use. The limits of belt drive for high precision are currently about 200 lb, but that should be sufficient for even heavy machining purposes (to an extent) using 50 and 75 mm diameter rods. So to make things like engines and hydraulics, we intend on using belt drive, and will switch to threaded drive is belt is not acceptable for industrial productivity on a small scale.
- Force calculations for determining belt limits indicate 100 lb force at 10 micron precision. Good, but limited to heavy duty applications outside of the most force-intensive operations. See GT2_Belts#Force