by kbob » Sun Nov 11, 2012 11:41 pm
400 steps per revolution will require your controller to run faster for a given motor speed. If you're planning to use an FPGA or DSP, that is probably not an issue. If you are using a PC parallel port or other software-driven step pulses, it may well be.
Also note that you need steppers whose shaft sticks out both ends, and the BOM assumes your motors have a 5mm shaft. I bought steppers with a 1/4" shaft and had to get different pulleys and couplers to compensate.
400 SPR also has an advantage, at least theoretically: At 200 SPR, full steps (not microsteps) are about 1/125th of an inch apart. I expect that to lead to irregular engraving when using higher than 125 DPI as the Y motor drifts back toward its full step position. (My motor control is not finished, so that's speculative. Hopefully someone with first hand experience can confirm/deny.)
Bob
"If you didn't code it, it will never own you." (-: