Skewed cutting but engraving is fine

We have 3 laser machine Derek laser using Ruida controllers. We have been having issues with cutting, the cuts are skewed. Maybe anyone has had the same issue. It is the same with all of our machines. The skew is like .5mm as you can see on the photo.

Is this reflected in the opposite direction on the other side of the cut shape?

Co2s have a “drag” factor on their cut

(Image is from fiber lasers cutting metal but serve the purpuse)

Uncertain if this is what you are referring to
But if it is, the only way to remove it is slowing down, which… might not be very efficient.

If however you mean the cut is skewed Always even against the direction of the cut, this means your head mirror might be focusing not at the center of the nozzle but offset.

Its the second one that you described, cut is always skewed, it skewed by .5mm to the right on the underside. The alignment seems to be dead center on the nozzle. All 3 lasers are like these.

Any chance you could show us your setup

As in , set the material on the bed, show us your focal head and the direction of the skew, so we can have a visuel cue on your machine

it has to be mirror alignment (or bed level for that matter) if is consistent

I will take photos of my setup later. For the meantime uploading photo for reference. I have checked alignment of mirror and they are aligned. The deck I am not so sure yet, we have suspected that it could be the deck but we are not so sure how to properly align them.

That’s pretty severe. Is the angle the same relative to the machine regardless of cut direction (indicating mechanical problem) or is the angle always the same relative to the cut direction (indicating beam drag).

We cut tons of steel at work and deal with drag always. I know what that looks like, but I’m not sure what it looks like on wood. If drag, you may need to slow more for direction changes, but my money is on a mechanical problem. Ie, M3 holder/tube/nozzle out of perp/plumb with bed.

Its not the drag that the problem. I believe the angled cut problem only happens when its cutting on the y-axis the cut on the x-axis is pretty straight. The photo you have shows the sides are cut straight, ours cuts angled on one side, the y-axis.

Yes, drag is always parallel to the cut direction, so only corners or fast arcs are problem. Easily corrected with speed adjustment.

Sounds like your heads need some adjustments. I don’t have a CO2, so not sure exactly how to go about doing that.

Measure the laser head against the platform:

Despite the obvious misalignment, the beam came out perfectly perpendicular to the platform: Mirror 3 can send the beam at an angle within the tube.

To check the beam alignment:

  • Manually burn a spot in something cheap at the normal focal point
  • Lower the platform 10 mm
  • Burn another spot, raising power as needed
  • Iterate until you run out of platform motion

If all the spots are concentric, then the beam is perpendicular.

If they walk off to one side, then that angle need correcting.


Exactly what i was thinking but was not able to… put it well in words
I would assume depending on the focal lenght this issue can become more or less obvious to fix
Longer focal lense and tube - like in picture - would possible start making the beam touch the sides of the nozzle?

Seems reasonable: the longer the path inside the lens tube, the farther the beam will be from the axis at the nozzle aperture. However, if the (focused) beam passes through the middle of the aperture and beam is perpendicular to the platform, then there’s not much to complain about. :grin:

If it’s not right, I’d start by aligning the laser head perpendicular to the platform in both axes.

Then verify the beam still hits Mirror 3 in its center, which may not be the center of the laser head’s aperture. Replace the mirror with a paper target to see where the beam hits; it should produce a single spot at both ends of the X axis travel.

Reinstall the mirror, replace the focus lens with a paper target, and adjust Mirror 3 so the beam hits the center of the lens aperture.

Reinstall the lens (convex side up!) and the beam should now emerge from the center of the nozzle, which you can check with some tape stuck on the nozzle.

Verify the beam is perpendicular to the platform over the entire range of its motion.

With a bit of luck, that will change the results, but you never can tell without measurements! :chart_with_upwards_trend:

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