Xy axis changing during project

Im brand new to cnc world… I’ve only done a few small things where I’ve used only one bit now Im doing a two tool project with raised lettering and raised border … the first pass goes as planned cutting the letter edges out and then the pause to change from 1/8 to 1/4 to cutv out all the material in the pocket. I try to be careful changing the bit and zeroing out the z axis… then hit Resume… after two failed attempts with it obviuosly shift ing xy zero… which i blamed on myself. The third attempt the cutting resumed what seemed like correctly but after 10 mins it finished an area lifted to go to new area to pocket out and it has moved the x axis about 1/2 inch and starts to cut the letters… any suggestions? After the pause should i use the auto touchplate and rezero everything?

Hi @curtw40 - the most likely thing I can think of there is a loose x axis coupler - so the motor sometimes spins, but the connection to the lead screw slips. It’s an easy fix - just tighten the coupler nut.

The only other thought is that you might be stalling the motor on the cut - but that’s quite unlikely unless you are really trying to remove a lot of material - you would definitely hear the router struggling.

Let us know what you find!

Ok like i said im brand new to cnc …i took you advice… the connectors seemed tight…BUT i notice when moving my router back and forth on the x axis when close to middle of machine it starts to work… like something is binding… and accually stops the machine.
Tried a zero reset and moved it around to it made the binding noise again and it stopped… ash’s i could see the x axis numbers still moving. I believe that’s the problem obviuosly but how does one stop the binding?

I had the same problem and found that I had the couplers to tight. I let them off a bit and all was good, good luck, bob

Eyeball the mechanical moving parts, or find a friend with some mechanical skill to help you. Pay special attention to whether the problem always occurs in the same place on the axis or if it changes. Careful observation has been invaluable as I’ve been breaking into this arena. If the axis is a screw drive or has linear bearings or a rail, look to see if the they are extra dirty or damaged in that region.

Its brand new… only done a couple small projects… but noticed it binding a little since set up… it always occurs on the right side of the x axis

The following assumes that your machine is a LongMill or at least a screw drive with an anti-backlash nut similar to this one. Oh what a cute face!

It could be that the anti-backlash nut is too tight or not aligned straight. Either of these conditions could cause the machine to bind. To make sure the nut is aligned with threaded rod you can loosen anti-backlash nut’s mounting bolts a bit and jog the axis a little back and forth and then tighten the bolts back up.

The method I use to adjust the third bolt on the nut, the one that closes the gap to take up the backlash goes like this. I first back the bolt out until I can feel and hear, if it’s quiet, the play in the anti-backlash nut by grabbing the XZ carriage and wiggling it side to side. Your trying to feel the nuts threads hitting the left and right sides of the thread gap. Then tighten the nut slowly until that play is gone.

I read somewhere on the website about the backlash like you posted…i lossened off the two bolts a half turn… and the binding had stopped… like you posted i believe that was the issue… tks for your help


Welcome to the group Curtis! I forgot to welcome you earlier.

That’s good news and I’m happy to help. Make sure the mounting bolts are still snug enough that they don’t loosen during operation. You don’t want them falling out during a carve. It’s good to check nuts and bolts for tightness and inspect your mill on a regular basis to make sure all is well. That and try to keep it clean, wipe any buildup off the rails that the wheels run on, vacuum the threaded rods etc regularly. And once in a while, not every cleaning, I put a drop or two of 3in1 oil on the linear bearings for the Z axis.

Be safe and have fun with your machine!

@curtw40 I have moved your topic to the machine help category and marked it solved my @_Michael

Have fun with your LM. Please post your projects in the Show Off category.