I have a 570 oz-in bipolar stepper motor (4 wire). I'm driving it through a SainSmart ST-4045-A1 driver. The stepper is pulling loads varying from 6-12 lbs, and movement is done via a 1" spindle that wraps/unwraps a 1.1mm braided steel wire from the spindle. The cable being used (from driver to motor) is a 4-wire shielded cable, and is about 10 feet long.
I can't get the motor to move reliably in full-step mode - I've tried various combinations of speed, acceleration, etc, but it won't reliably move in full-step mode, especially when pulling a load. In microstep mode (I've tried 1/2 -1/16 microstepping modes) I can get it to do full steps (ie, not microsteps) and multiple-step moves, the catch is, when I move in one of these 1/n fractional modes, movements only occur reliably in increments of n - effectively eliminating the finer positioning that I was looking for with microstepping. (Multiple-step moves are increasingly smoother in the microstepping modes, but bottom line, I can only make an individual move in full-step increments. So, in 1/2 step mode, I have to make a minimum of a 2-step move to get movement. In 1/4 step mode, I need to make a minimum of a 4-step move, and when pulling load, these multi-step moves seem to generally behave in increments of n - I see missed steps if I try to move in some increment other than n.) I have tried many combinations of current (set at the driver), speed and acceleration (set in software), and both 12v and 24v supplies, all with the same effect.
I'm trying to figure out if this is a driver problem, a wiring problem, a stepper problem, and application problem (ie, the load and/or cable/pulley system - the cable moves freely, BTW, but clearly load seems to play a role), or if this is really how things work, and I'm just confused.
Thoughts/suggestions? If any additional information can be provided to help puzzle this out, please let me know.
Thanks!