Cut Passes shifting To the left

I am at a slight loss on where to look to fix this issue. I am cutting out topo maps. The first three have worked out great with no issues. Today in cutting out my fourth map I have run into an issue. After cutting each pass the the next one shifts to the left. so what is suppose to be a 4"x7" map is slowing moving about .063 to the left making it longer. Height is correct and stays correct. I have remade the design, deleted the old g code and tried new g code. As a test I cut a 4x7 rectangle and the came out square with no issues. Tried circle no problem. Any ideas on where to look to try and figure this out. My next plan is to try a different computer. Thank you in advance for your help.

This is probably a mechanical problem — please check all the usual culprits:

  • Pulley set screws: — be sure to check all axes/pulleys including Z.
  • V wheels / eccentric nuts:
  • Z-axis:
    • Belt drive: Belt tension — the Z-axis should be guitar string tight (but careful not to bend the motor shaft): on deep cuts it may help to remove one spring from the Z-axis temporarily (which side doesn’t matter), esp. if one hasn’t added a spoilboard on top of the wasteboard — it also helps to install the router as low as possible (installing the Makita adapter upside down will help). Some folks have found it helps to remove bolts which won’t stay tensioned (M4 Z-axis tension bolt, various V wheels with eccentric nuts), apply a thin bead of threadlock along the length of the threads, then reinstalling. See the video at: Note that the X-axis motor is held in place on standoffs and if those bolts are loose this can cause belt tension issues.
    • HDZ — make certain that it can move for its entire extent (the coupler provides a good point to turn it) when the power is off, check that dust caps are all in place and not interfering with movement
    • Z-Plus — verify that it can move from top–bottom

It is also important to be sure that the collet is correctly tightened, the endmill fits correctly and doesn’t slip, and the router is mounted securely in the mount, and that the mount doesn’t shift. Note than endmill pullout can happen gradually, especially when profiling against tall walls.[4]

Also feeds and speeds may be a consideration: and see for concepts on this and for a testing technique and see the series #MaterialMonday: #MaterialMonday on YouTube

Beyond that it’s usually a matter of calibration and squaring the machine c.f., and and

Thank you I will check all of those. Not sure of it means anything but I ran a old one and it wasn’t as bad but it happened on the opposite direction. I have attached a couple of photos to help descripe my issue.

Thank you. I think it was a combo problem. I found that the belt had been run over by the v wheels and damaged one edge and that both set screws where miss. I feel confident that is the problem. Thanks for your help


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