ZX-Axis Gantry rough movement / binding

Hey team!

Really excited, got my Longmill Mk2 this week after ordering at Christmas. Over the last few days built my table, etc, and excitedly dug into the big box today!

Not even 10 mins into assembly and I’ve run into an issue. Manual and Chris’s video both state that the ZX-Axis gantry is smooth and doesn’t bind. Mine is quite the opposite, it requires a decent amount of force to get moving, and from top to bottom will feel very rough and bind in several places.

I don’t want to go fiddling around too much yet and mess up any pre-set alignment, and on the forums I found a thread regarding an Mk1 gantry with a picture post about re-calibrating the gantry so the axis runs smooth, however I couldn’t find anything regarding the MK2.

Hopefully I can sort this out myself without having to wait another few days before a replacement could be sent.

Thanks all in advance!

Check the ‘anti-backlash nuts’, it been my experience that most of the time that is the problem. Also make sure the table is square. Try running the gantry all the way to the end of it’s run and let it bump against the end of the rails. It makes a lot of noise but will aid in alignment of the gantry.

Good luck and as always let us know what worked and did not work.

I’m having a similar issue with the ZX Axis on my new MK2 48x30, but only headed away from the motor (traveling right) during the last 50% of travel. Rapid travel back to X0 had no unexpected noise.

I’ve tracked it down to the anti-backlash nut as well. If I loosen it, I barely get any noise heading out but obviously there’s a lot of X-axis slop. Everything is square, the v-wheels are adjusted correctly, I’ve applied graphite to the lead screw, and I’ve bumped the gantry into the rails.

I ended up positioning the gantry about 25% away, tightening down the anti-backlash nut and barely engaging the “backlash adjustment bolt”. This eliminated 90% of the noise in Rapid movement and it doesn’t bind at all.

If someone has any other suggestions, please let me know. Unless I put a fixture out there, I probably won’t be cutting at that distance often but I want to make sure I’m not missing something that will bite me later.


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Update: I put a long allen key into the backlash adjustment bolt so it sticks out just shy of the gantry. When I run the gantry out to the right, it makes “the noise”. If I put pressure on the allen key, it goes away.

I don’t know if it’s possible to misalign the x-axis lead screw when threading it in through the anti-backlash nut, but I may try and reinstall to see if that helps.

Not 100% quiet but here’s what I ended up doing:

I disassembled the x-axis lead screw and removed the anti-backlash nut. Using a clamp, I slowly squeezed the “finger” of the nut so it bent in a little and left it for a bit. After removing the clamp, I used the adjustment bolt to shift the finger back out so it was straight-ish and reassembled everything. A little more tweaking of the bolt and there’s just a slight squeaking during rapid/corner movements.

I plan on running some break-in code and will update if anything goes awry.