Longmill 30x30 G0 Command

Hi Folks, just checking to see if anyone else has experienced this issue or may be able to offer some insights.

Symptom description:

  • Maximum travel speed along the x-axis stalls as in the linked videos below.

Troubleshooting attempted:

  • First noticed gcode files choking the x-axis on G0 commands (maximum speed)
  • Eliminated gcode potential error by setting x-axis zero point to the far right and using UGC Sender to “Return to Zero”. This is illustrated in the video.
  • When x-axis comes to a screaming halt, used my fingers to check tension on the lead screw; moves freely and shows no signs of binding.
  • X-axis lead screw was checked for any looseness, none detected; lock/screw nut tight.
  • Checked for slippage on the x-axis motor, none detected
  • Only occurs along the x-axis from left to right (right to left was checked with no problem).
  • Symptom does not occur at normal feed speeds
  • Symptom does not occur at same location along x-axis

When the symptom is about to occur, it seems like the z-axis mount or the lead screw may be hitting a resonant frequency and causing vibration just before the screaming occurs. This is noticeable in the video.

I’ll keep testing and in the meantime, if anyone has any ideas on this, please chime in.



Wire not plugged in properly. Check all your connections and push on them really hard. Its surprising how hard you have to push. One side may be in not the other. Pull them out and replug them.

Thanks Greg, appreciate the input. Rechecked all wires wires on both ends of the connectors (for all motors, power, etc.) and no issues found; also validated the that the screw-in terminals were snug and properly catching the wire. Ran test again and no joy.

As it usually is with myself, awoke last night around 03:00 and had an eureka moment. When I finally regained consciousness this morning, went to the machine and slacked off the eccentric nuts by just a hair. Issue appears to be resolved. The x-axis rollers on on the z-axis assembly may have been just a bit too tight. Ran a bazillion tests and no repeat has occurred of the symptom.

I’ll keep an eye on it and report of the symptom reoccurs, but am reasonably confident that the eccentric nuts were just a tad too tight.


Awe there ya go. Seams I tightened up the screws that go into the anti kickback block a little too tight too. Caused me all kinds of trouble. Andy Lee fixed it up for me just right.

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I added a slight amount of tension on the x-axis anti-backlash nut as well, and seems to have completely resolved the issue.


It’s a backlash bolt (not a nut) on the z-axis assembly, as illustrated in the picture below: