Stepper Motor Issue on MechMate CNC

[peter22]

Hi everyone,

I’ve run into a problem with my MechMate CNC and I’m hoping someone here has seen this before or can point me in the right direction.

The setup:

MechMate CNC (custom build)

Stepper motors: NEMA 34 (8.5Nm)

Drivers: Leadshine DM860A

Controller: Ethernet SmoothStepper + Mach3

Power supply: 68V DC, 10A

The issue:
Out of nowhere, one of my stepper motors (Y-axis slave) started stalling and skipping steps intermittently during cutting. It sounds rough, like it’s fighting against resistance, but mechanically everything moves freely by hand. The motor also gets noticeably hotter than the others after a few minutes.

What I’ve tried so far:

Swapped the driver with another axis → problem stays with the motor

Checked wiring and connections → all solid, no broken wires

Reduced acceleration and velocity in Mach3 → helps a little, but still skips

Checked motor shaft for binding → smooth when rotated by hand

Verified motor tuning and current settings → seem correct

Questions:

Could the stepper motor be partially damaged (e.g., demagnetized or winding issue)?

Is there a good way to test the motor without special equipment?

Could this be a sign of failing insulation or internal short?

Any help or suggestions would be greatly appreciated. I’d prefer not to replace the motor unless I’m sure it’s the cause.

Thanks in advance!