While I applaud your intention to build a machine out of the junk you have lying around (I tend to think that way myself) I'm not sure that what you've got really adds up to a 3D printer. It sounds like a promising start to a CNC mill, though. A 3D printer, unlike a mill, doesn't really encounter much resistance to moving, but it wants to move fast, with the ability to change directions quickly. Generating a lot of inertia by using heavy components like those massive ballscrews will work against you, I'd think. Even the weight of those heavy rails on the driven axis will be a lot to start and stop, especially when you add the weight of whatever you're mounting them to.

NEMA 43 motors are also overkill for a project like this; they typically have very high inductance, which means they need a lot of voltage supplied to achieve their optimum speed. This one http://jssmotor.en.made-in-china.com...h-4-Wires.html , for instance, has 16mH inductance, which means it really wants 128v, which is more than most drivers (especially inexpensive ones) will tolerate. They generate a lot of torque, but you don't need that for a printer. Most printers use NEMA 17 motors for good reasons...

I don't know where you came up with the requirement of 160,000 steps/sec. Most printers can rapid at about 120mm/sec (actual printing is usually slower), but that works out (assuming you have a normal stepper with 200 steps/rev and 8mm pitch screws) to 3,000 steps per second. Even if you go with 10x microstepping to combat resonance issues, that's still just 30,000 microsteps/second. How fast did you expect to run this thing? If you really want your motors to go really fast without loss of torque, you should consider servos instead of steppers. But even a servo would have trouble spinning at 48,000 RPM, which is what 160,000 steps per second times 60 divided by 200 works out to. Maybe you'd want a spindle that went that fast on your mill, but if you attached that to one of those ballscrews and let it rip, get out of the way quick - you'll be launching components of your build through the wall..

I like the idea of building it in a welded aluminum cube, though. I'd say keep reading up on 3D printers - there's a reason they're built the way they are. You might buy a cheap one just to get familiar with the way they work, and then launch into a building project that uses components that are appropriate to the task. Here's a source for the glass: http://www.sandysindustrialglass.com...33-sheet-copy/

Andrew Werby
www.computersculpture.com