Boy, skipping steps without the belts on is pretty hard to do.
Have you set the current on the drv8825s? They are not set properly out of the box. Too low and it will skip a lot. Too high and the drivers will go into thermal shutdown (in my experience, they shut down for longer than a few seconds, but who knows?)
Are you sure your wiring is right? Try it with just a motor wired directly to the mks.
It is very odd to have skipped steps while it is just wiggling around without resistance.
If you have a multimeter, measuring the voltage at the power supply could give you a clue. If you’re using much more current than the supply can handle, it will dip a lot. Anything over about 9V should be fine for the steppers though.
Regarding 24V psu, does your mks support that? I know the ramps doesn’t. At least not stock.
I’m wondering if what I’m seeing isn’t skipped steps but rather an issue with Marlin. Is there somewhere I can get an older version of the MPCNC Marlin?
To answer your questions:
vref is set to 0.7v (1.4A) which seemed pretty appropriate for these steppers.
I re-connected just a single stepper to each driver and I’m seeing the same behavior.
The MKS is rated for use at 24V although I wasn’t 100% sure about the drivers themselves. They haven’t burnt up yet so fingers crossed.
I’m using a 5A power supply so I don’t think there is an issue there. I tried running just a single driver and stepper motor and it didn’t change anything. I also tried using a different 12V power supply and that does the same thing.
