ULS 6.60 Laser Cutter: Z-axis issues

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Once in a great while, we'll have some kind of issue with the Z-axis system on the ULS 6.60 laser cutter. It somehow gets itself into a state where the physical position of the Z-axis doesn't correspond to the internal software's idea of where it should be - and cycling the power, or attempting to position the Z-axis using the front panel controls or even recalibrating the machine doesn't get you out of this situation.

If this happens, you should definitely stop reading this article and get a local expert to help out!

This page is here to help jog the memories of local experts!

The ULS firmware is notoriously buggy here. The firmware maintains an internal, non-visible, non-user-adjustable counter register of where it thinks the Z-axis physically is, and stops you if you try to move further even if the limit switches did not yet trip. Confusingly, this is not the number you see on the LCD.

There appears to be two ways to fix this:

Unplugging the Z-axis Stepper

According to Danny Miller: The fix is to pull off the Z-stepper's power cable so it thinks it's moving but it's not.


  • Do not remove or reattach the stepper cable while the machine is powered up.
  • Don't pull the cable itself or the white part of the housing, pull the RED part of the cable end housing out of the pin socket on the stepper.
  1. Power down the machine.
  2. Pull the stepper power cable.
  3. Power up.
  4. Jog the Z axis DOWN 5" (the axis will fail to move, this is the point).
  5. Its internal position register will now think it's 5" below the upper limit.
  6. Power down
  7. Reattach the cable.
  8. Power up. The firmware will think it's 5" below the upper limit and will allow you to travel 3" up until the upper hardware limit switch engages.

Total firmware reset

According to Martin Bogomolni:

I talked to Darryl at Universal Laser Systems. He recommends we do the following procedure once. This will reset the entire 6.60's CPU (onboard) settings and allow it to re-calibrate the Z axis position:

  1. Turn the 6.60 System On
  2. Go into the UCP ( Universal Laser Control Panel ) System tab
  3. Type CTRL-F9
  4. You will see a white rectangular box. Enter the passcode "wade007"
    Reset CPU?
  5. Machine will turn off after about 15 sec
  6. Unplug the USB cable from the PC
  7. Re-connect the USB cable to a different USB port
  8. Go back into the UCP Viewer Tab
  9. Remove Vector Cutting Table
  10. Home Z from the Viewer Tab

The table should go completely to the bottom of the laser cutter, trip the limit switch, and then home.