Cutting Misaligned

Hi All,

We are experiencing a couple of issues with our machine & are out of ideas where to look.

The machine is a 130W 1000mm x 800mm with a Ruida controller and is less than a year old. We work mostly with 3mm acrylic.

I have attached some pictures of the issues we are experiencing:

  • Shapes not cutting in the correct place. (Picture of white letters where you can see the inner shapes are not cut where they should be. The font for the O & E has bumpy looking lines by design, this isn’t a laser issue!). This shows correctly in preview on Lightburn & on the controller once completed. We cut a lot of lettering and find it happens to all different sizes and font types etc.

  • Shapes not joining (2 pictures of kiss-cuts where letters aren’t beginning and ending in the same place. Picture of a circle cut out of ply which this has also happened on).

I’ve read a few similar threads & have tried to look at a number of factors but nothing has fixed this so far:

  • Mirror alignment is fine
  • Belts are fine, can’t find any loose screws
  • Calibration was slightly off which has since been adjusted but hasn’t fixed the issues
  • Turning on the ‘Hide Backlash’ option does help with the shapes joining, but still experiencing cutting in incorrect place

Does anyone have any ideas on where else to look?

This issue has popped up in the last month and no settings were changed around the time this started happening etc. We are assuming it’s a hardware issue.

This has all the earmarks of something lose. Since it’s been working there is no reason to suspect anything except wear or lose.

Sounds like you’ve checked all the grub screws…

I’d spend a bit more time with the mechanical… it’s one of the hardest things to find.

Although rare this can happen with lose head components, such as lens tubes and the lens itself.

Good luck


In the past, I have disabled stepper idling to help diagnose drivetrain slop. I would lock the motors and then carefully try to move the tool head back and forth in all directions, by hand, while looking closely for movement at all drivetrain components. A move at the head should also move every single connected part all the way to the motor.

Of course, there is risk here. You’re working inside a powered-up machine, so being knowledgeable about typical machine service safety procedures is mandatory. Attempt at your own risk. :wink:

As @cggorman suggests but it may be very difficult to find something with a very minor bit of slack… it’s worth a try… the only other option is to make an adjustment and test it… kind of a long and tedious task…

If you can disable the lps (Laser power supply or lps) from the mains, it would be a good idea.

On my China Blue, you can turn the 24V supply on, motors and controller work, and leave the lps off. That way it cannot fire…

If you can’t do this from your switch panel, all of the mains go into one connector and you can just pull it out … of course any change power it off :crazy_face:

Good luck


Unfortunately, that means you haven’t found the one screw causing the problem.

Because the backlash seem to appears along the Y axis (vertically in your letters), it’s most likely one of the setscrews connecting the Y axis motor to the jackshaft across the back of the machine.

The pix in this post show some possibilities:

Toothed belt pulleys may have a setscrew buried under the belt between their teeth, so (with the power off!) rotate the shaft by hand so you can inspect the entire perimeter of the pulley.

Get out the hex wrench set, start at the motor pulley, and try to loosen each setscrew as you work your way to the laser head. The ones not giving you trouble will be nice and tight, the one letting the shaft move will be easily loosened.

If it’s on a shaft or coupler, rotate the shaft back and forth as you tighten the screw, so the screw ends up at the middle of the flat in the shaft when it’s firmly tightened.

As you’ve discovered, Hide Backlash doesn’t solve the problem. It just pushes the backlash somewhere else, where you may not notice it on this pattern. Unfortunately, the next pattern will reveal it in full glory, so the only way to eliminate it is to find that elusive setscrew.

Thank you all for taking the time to comment, I really appreciate your help. We will begin the wider search for the loose screw!!

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