[CNCwoodMan]

When you hear that high pitched whine of the stepper, and it doesn't turn, that means the stepper has stalled out. Either the torque needed to move the axis is far greater than the available torque, or the stepper is having resonance issues. While it's possible that there may be resonance due to some compliance in the belt, I think it's more a matter of not having enough torque available.

See, that pinion acts somewhat like a gear multiplier; or in other words, it spreads the motor torque out over a greater distance - exactly pi times the pitch diameter of the pulley. This in turn forces you to use a high step multiplier to gain back some "resolution" and smoothness. But this creates another dilemma where the torque decreases at each microstep. And also, while the controller can command a move to the drive, the stepper may not necessarily turn because it has to reach the next microstep that has enough torque to overcome the weight and friction of the particular axis. So that possibly could explain some of the "jumping" witnessed.

In ye olden days, the hobby stepper drives were not as sophisticated as today's, and we'd add either a weighted disk, or home-made "rattler" damper, or purchase a viscous damper, to alleviate resonance in the stepper. This would require a rear shaft, which your steppers do not have. Today's drives have electronic damping. Again, I don't think this is a resonance issue. Those steppers are only rated to 175oz-in stall torque, and they're at a mechanical disadvantage direct-driving that pulley. Easily.

The way I see it, you have three choices. The most expensive is probably the easiest - source NEMA23 planetary gearheads with a reduction ratio of 7:1 to 10:1. You can get them for under $100 each, and you can just bolt your steppers to them and the gearheads to where your steppers are now. You'll have to modify the pinions to fit the new shafts or purchase new pinions.

The second choice would be to make your own belt reduction setup. I think this would be rather difficult compared to the first option, but it would be cheaper as the cost would be sweat equity.

The final option, which I'm not the keenest on, is find the strongest NEMA23 steppers you can (I believe that's 570oz-in) and pair them with the smallest pinions that will fit the shaft. This is not ideal as you'll still have the resolution issue, and if there was a resonance issue, it may be worse with the larger stepper.

Appreciate all the info! That was really helpful in understand the RCA of the issues. However, seems as though I have now created another problem for myself as you can see in the other post!!!!