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Author Topic: Z axis values changing, stepper not moving  (Read 1793 times)

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Z axis values changing, stepper not moving
« on: January 05, 2014, 10:50:10 PM »
Hi all,

I'm back with another problem! I've managed to get hold of a PC that doesn't make my steppers clunk and things are mostly going ok.

The major problem now appears to be the z axis stepper skipping steps. It's now happened 7 times in random spots while running the same Gcode and I've been getting weird side effects in Mach3 afterwards. For 3 of the attempts, I immediately hit the RESET button and jogged the z-axis. However, jogging doesn't work... the Z coordinates are changing on the main Mach screen but the stepper doesn't move. For the other 4 times, the jog button works but my auto zeroing tool doesn't. The failing Gcode in the auto-zero tool is G31 Z-3 F20. In addition to that, G0 and G1 don't move the steppers either. In all cases, the Z coordinates change in the Mach3 GUI.

From reading through this forum, I think the coordinates in Mach3 are called DRO? I'm not sure if that's correct because I don't know what DRO even stands for.

If it's at all helpful, I'm getting strange scratching/screeching noises from any stepper motor plugged into the controller board's Z axis. I'm using a Gecko 540 and I'm in contact with those guys seeing if it's something worth investigating. In the mean time, I was thinking of re-configuring my cnc to use a different physical stepper controller for the Z axis but wasn't sure if it's possible. My machine has 2 steppers for the long X axis setup in slave mode with the stepper controller labelled A being the slave controller. I can easily disconnect that second X axis ballscrew/stepper (A axis) from the Y axis and only drive the X axis using the one stepper (the driving ballscrew wouldn't be centred though, it's to the left of the machine). I would then use the stepper controller labelled A as the new Z axis. This would eliminate the Z axis controller and I could test the same Gcode and see what happens. I'm just not 100% sure how to do it.


Thanks for reading, hopefully someone can make sense of it all.

Offline Hood

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Re: Z axis values changing, stepper not moving
« Reply #1 on: January 06, 2014, 03:01:25 AM »
Try reducing the Velocity and Accel for your Z by 20% or so.
Also might be worth trying in Sherline mode.
The axis not responding whilst the DROs ( Digital Read Out is what it is short for) is strange, as that kind of suggests something may be interfering with your port or possibly some fault with hardware.
Testing with a scope would be the easiest way to diagnose.
Hood