Unstable Z axis

Hi All,
I got my Longmill 12x12 6 months back. I put it all together now, it seems to be working great on the X and Y-axis perfectly, but not on the Z-axis. It seems like whenever I run my code the cuts never go down to the depth I want and afterward if I click on “Go to Zero Z” it never goes back to the right height.

Not sure what kind of software issue can cause this?

I thought this might be because of a hardware problem. So I made the CNC cut in the air, after completing the cut I checked the Z zero height, it seems to be wrong. I thought it might be some kind of issue is the setup or wiring which is causing the Z-axis to slip. So I made the ZYX move randomly by clicking in the control panel. This time it seems like Z returns to proper height when I press “Go to Zero Z” .

Does anyone has any idea on how to fix this issue.
Thanks in advance

@victor Welcome to the forum! I am positive someone here will be able to assist you with your difficulty. You could also contact Sienci directly. I am sure they would assist you as well. Me, I am just a “patiently waiting “ person. Meaning I ordered my unit and awaiting its arrival.

Please take a minute to post the solution to your problem. It may help other users too.

Be Safe!

@victor Check to make sure your bit when installed in the router can reach the surface of your spoil board. Your Z may be bottoming out during the cut which would mess things up pretty well.

I would also make sure all of your connectors are tight on the coupler to the Z stepper motor , the belt from the stepper motor to the lead screw at the top of the Z Axis is tight as well.

Finally, make sure your bit is securely in the collet (tightened with the two wrenches, not using the push button) and not slipping when cutting.

@stevendq Thanks I will check those things today. Although, if I make the CNC run any G-code on air it seems to lose Z-Axis height.

That sounds like loose connectors either at the stepper motor/lead screw coupler or the belt to stepper motor isn’t tight enough. I am sure others may chime in with more hp.

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@victor Welcome to the group, Bir. As you’ve already seen, it takes not time at all for members here to jump in to offer help.

If I understand, you can use the GUI to jog all axes and when you return to zero, everything is fine. However, when you run gcode, even when cutting in air, Z does not return to 0.

Can you tell us what CAD/CAM software you are using? What post processor are you using in that software? Can you post gcode where the problem is showing up?