CNC Wood router Inconsistent Depth

[Ty-fii]

I have a CNC wood router that with Mach 3 and Keling stepper motors. The stepper motor controlling the z-axis movement (Part# KL34h2120-42-8A) will not go to the same depth consistently. Randomly as the router plunges into the material (mostly 3/4" plywood), it will not go to the depth programmed in the G-code. Sometimes it will cut an entire sheet of parts just fines, and the next sheet will only go partway through on some or all of the parts.

I have verified the g-code is correct and the machine is properly grounded. I have done ghost runs with no material and seen the same results. My thought now is to get a new Keling stepper motor to see if the one I have is damaged. Otherwise I would think the problem could be the stepper drivers. Is there a way I can test the motor without buying another one? Any way to test the driver?

[bobsch]

Start by checking all your wiring. Make sure each pair is twisted properly and all the grounds are tight.

If all you steppers are the same, swap two of them and see if the problem stays with the z-axis or follows the motor. That will tell you if the motor is bad. Speaking of motors, are all your power leads to the drivers each connected to the power supply and not daisy-chained?

[ger21]

What kind of drives are you using? What voltage?

What is your velocity and accel set to?