I'm having a bit of an issue with three of these motors:
Vexta PK266-02A NEMA 23 stepper motor Interinar Electronics
I'm running them in bipolar parallel, and when increasing the current all the way to max on my stepper driver boards (2amps) with the potentiometer they start to make a vibrating whining noise, and then eventually start to pulse on and off slower and slower.
When I run they machine in this state the motors will actually pulse on and off, move stop moving, start again, adjusting the current changes the frequency of the pulse.
these are the drivers I'm using:
Pololu - A4983 Stepper Motor Driver Carrier with Voltage Regulators
I'm driving them with a 24volt, 6.5amp supply
any hints?