Wonder what is happening here?

Ran the machine yesterday and there was a deviation in the first pass in the Y axis. Subsequent passes were fine and the part is the right size.

Here is a photo showing what happened.

It is cutting a hole here in this instance and the outside final cut for the hole is spot on. I did not use a finishing pass on this hole.

Any suggestions? I reused G code from the first version of the boat seat and it was fine.


Is that cut-out an entire part? Do you have holding tabs? To me, it looks like the part cut-out moved a little bit.

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No, just the first cut / ie the first pass went slightly angled. The rest of it is fine and I did remember to put the tabs on this time… Here are a couple of more photos I did not realise I took.

So one shot shows the other side of the cutout/hole and it is fine. The other is the wonky bit.


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Maybe a slightly loose grub screw in one of your belt pulleys which jumped back in position after change of direction

I have noticed the same issue on my LR2. Often just the first pass. But it has been a while since I noticed it happen.

Looking forward to hearing the cause of this!

Is the shift parallel to your belts? If so your wheels got nudged on the table. Before you start a job run the machine the full length of the belts a couple of times to make sure they are tracking correctly.

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Well, the shift is on the X axis.

So today did another run and it went funny again. I also was trying a 32mm 3.18mm bit that I bought and I was not happy with that but I don’t think that was the problem. It did not cut good circles.
It dragged itself across the table by about 3mm. Nearly failed the job at the end but I was watching and stopped it all.

So pulled the old girl apart.

Couple of observations.

  1. grub screw on X axis seemed tight. But took it apart, cleaned it all with thinners and put it back together with locktite.
  2. noticed that the teeth of the cog wheel thing look like they have been deformed a little bit. See photo. But I don’t think it is the problem. (sawdust?)
    3.slid the carriage back and forward with out the belt off and it runs really freely across the X axis, not binding.
  3. considered my patent brush dust shoe could be catching and dragging the setup to one side but I doubt that. So have removed and am printing the one with the shower curtain as a barrier. Should be done in 10 hours.
  4. noticed on reassembly that the X axis Stepper seems sort of loose in it’s frame on the plate. See video…
    Does this look right or should I take it off and disassemble it too and retighten everything…? Or does this settle when the belt is on…?

What do you experts reckon?


The pulley looks fine. It doesn’t have to have a perfect finish to be accurate. Most of the surface is good. The motor being loose looks like maybe the screws going into the motor are loose?

Are you sure your wheels aren’t just skipping sideways?

When a motor skips, it sounds a little like gears crunching. That is going to happen if things go wrong. Nothing mechanical is grinding though, it is just the motor jumping from one phase to another really fast.

I don’t think there is enough ‘slack’ in the gantry to allow it to move across the table but I have not checked that.

Will reassemble and look for that effect. Guess the idea is to go then put some L bracket on the sides of the table to hold the wheels? I remember seeing photos of something along those lines on the forum.


Yeah. I put some 3/4" x 3/4" plywood strips on mine.

I owe you once again Jeff. You are the man.

I have found a couple of things but your last comment is the one about the thing drifting +/- on X axis. ie wheels move left and right

  1. redid grubscrews.
  2. that wobble in the stepper was due to a bolt missing??? Fallen out or failed to put in.
  3. went into town and bought more.
  4. refitted
  5. got a bit of aluminium L bracket and there is a 5mm drift across the x axis for the whole gantry. ie I can push/pull it 5mm either way.
    6.did a test pattern in Fusion and it cut fine but you could see it pulling the wheels one way then the next.

So… going forward.

  1. do I tighten up the gantry across the x axis to take that 5mm out and create friction in the setup
  2. do I go and buy 2 lengths of L bracket and screw it to the table to stop the wheels drifting left and right?


I don’t think it will add significant drag to put those l brackets on. But you are the one there, so do what you think makes sense.

Hi, New to the forum. There is a thingiverse part that uses rollerbearing wheels on the side of the table which are perpendicular to the Y axis wheels. This seems to help keep the X axis from drifting. Have only used a couple of times though

Just been looking for the link on Thingiverse Edward but can’t seem to find it. You have a link bookmarked?


Having been a user of the roller bearing side of table thingy for a while now, I suggest you use the plywood strips or aluminum angle.

The table MUST be square for the roller bearing thing to work. Here is a link for reference.

I don’t know of one on TV but I did one for my rolling-gantry FoamRipper… which runs on a hollow-core door. There’s one on each end of the gantry and opposes whichever way your gantry wants to drift. It’s obviously unique to my machine but its the same concept and could easily be adapted for another machine…

– David

Thanks mate. I started to design on in Fusion over a coffee but will stop now and print this out and see how it goes.

Like this one.
Will try and sketch one like it.
Thanks a lot mate.


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I think it works for me because I have unistrut rails which they ride along nicely.

Depending on the table I suspect you could shim the unistrut to suit.

I spent the better part of a week dialing in my table by sheering off tiny bits of the sides until the table was trued up. The effort was worth it in the end I suppose, however I could have saved substantial time by just using the conventional/tested solution.