Slide lubricant, bad alignment or not enough torque ?

[Muzzer]

Also check the maximum step frequency and / or the minimum pulse width (similar thing). If you have it set too high frequency / too short pulse width, some of them may not get through to the driver. Try running at lower max frequency to see if this is an issue. I don't use steppers any more but last time I did, this was the issue causing me stalling / lost steps. Those settings would be in your controller, not the driver.

[Robinwales]

Also check the maximum step frequency and / or the minimum pulse width (similar thing). If you have it set too high frequency / too short pulse width, some of them may not get through to the driver. Try running at lower max frequency to see if this is an issue. I don't use steppers any more but last time I did, this was the issue causing me stalling / lost steps. Those settings would be in your controller, not the driver.

Please can you explain frequency ?
Thanks for the reply

[Muzzer]

Dunno what software you are using to drive the stepper drives but in the systems I use (LinuxCNC and Centroid), you can select the maximum pulse repetition rate for the steps. If you try to drive the stepper drives with too high a frequency, the input circuitry (usually optocouplers) can't process them consistently. IIRC, I've seen options for 100kHz and 200kHz, possibly higher (I don't recall right now).

The default for Centroid seems to be 200,000 steps per second (200kHz) and I know from experience that the Chinesium stepper driver I tried didn't work consistently with that until I reduced it to one of the lower settings. Have a look and see if you can see an option to reduce that in your system.

This is different to max velocity, as you may find the required step frequency to achieve max velocity is above what the driver can process, depending on your number of steps per rev, ballscrew pitch etc.