Nema 17 sputtering (starts, grinds, starts again.)

Hello, I am trying to set up a cnc machine from scratch. I am using grbl shield 3.0 with arduino uno and 24V/15A power supply. I have 6 nema 17 motors (3 sets connected in series) drawing 0.4A (each motor) for a total of 0.8A on one 8825 driver. I have set the potentiometer to the correct voltage which I have worked out to be 400mV for both motors together. Both motors spin initially and then begin to sputter and idle until the end of the cycle (even on short bursts of 25mm motion). I am having the same problem even when running one motor at a time on its own driver. I had originally thought this was occuring because the original 4988 was underpowered, although I am now having similar problems with the larger driver. Anyone know if it’s my power supply? The motors are rated at 12VDC/phase, and I am running it on 24V 15A power supply. Could this be the issue? I have attempted to play with all grbl shield controller settings with no avail. Should also mention that when I turn the acceleration mm/s2 down to 1 the motors grind a little but make it through the cycle as opposed to when it is set to 10mm/s2. Also my second question is does anyone know how to return setting values to original state or where I can find a chart for the small grbl shield for arduino uno? Can’t find it anywhere. Thanks for your time.

Full step have not micro stepped.


I am sorry you are getting that behavior from your stepper motors. We do not make or carry any grbl shields, so we cannot help you with the settings on yours. However, we can help you troubleshoot your DRV8825 drivers. To begin that, can you simplify your setup further and remove one DRV8825 driver from your grbl shield so that you can test it? To do the test, you can connect !RESET and !SLEEP to 5V on your Arduino Uno and your 24V supply across VIN and ground. Be sure your Arduino and the stepper motor driver share a common ground (i.e. connect GND on the driver to GND on the Uno). Then you can use a multimeter to check if you are getting any voltage across any of the output pints (A1, A2, B1, or B2) and GND. If you are not getting any voltages, can you send pictures that clearly show the stepper motor driver and your connections?

As for your question about using a 24V supply for a 12V stepper motor, no, I do not expect that to be an issue. You can read more about why in this FAQ from the DRV8825 product page.

By the way, in your initial setup you mentioned you are connecting sets of two stepper motors in series, but the way you are calculating the total current draw is not correct (the current you calculated is what would be drawn if the stepper motor coils were connected in parallel).