Optimising laser alignment


I’m using my laser to cut some names from 3mm MDF. If I run the laser for multiple passes, it cuts the outline of the name first, the finishes with the inner part (eg. the holes on the p and o).

I’m encountering a few issues:

  1. When making multiple consecutive passes, the accuracy of the cut seem fine. However, on the inner parts of the letters, there is about 1mm that doesn’t cut through. I believe this is where the laser begins it’s cut on this part. (Also worth noting, this is the same location as the second problem mentioned below)

  2. I’ve tried running single pass burns, one at a time. Based on the recommendation in this thread. (NB: I don’t know what sub layers are. Couldn’t find any setting for sub layers).
    However, when I do this, the laser completes the first pass and returns to origin. When I run subsequent passes, I get these lips (see highlighted parts). It appears that running one pass, and then a second, and on… the laser ever so slightly misaligns with the first pass.
    It’s important to note, this doesn’t occur when I run a job with multiple passes (see gold version below).

*Top version was cut back to front, whereas bottom was cut front to back. This is why there is more burn marks on the second version.


The problem is, if I’m making 3 passes, the inner parts (which are small) will make 3 pass in the same spot, one after the other. In some resulting in burn marks probably, because the material is under constant power.

I’ve tried making single passes one at a time. However, when I do this,

… not what is needed…


Neje 3 Max
G-Code controller
Latest version of Lightburn
Mac OS Monterey, Intel

Problem has been ongoing. I’ve been pulling apart, changing burn strategy, and on. Still not getting it quite right.

The images in this post were burned with the laser on the floor (not table).

I also did this test burn at 10% power to try to identify if the line is connecting at the end points.

You can see in the second image that the line stops less than a millimetre short. It doesn’t quite fully connect.

Bumping post. Any genuine responses welcomed.



What I see in the picture is the circle completes it’s rotation, but the end point is not aligned. That indicates some backlash in the mechanics of your laser. Possibly a slightly loose belt on the Y axis or a bearing not sitting just right or a loose grub screw.

Run this test at high speed and post a photo of the results.

Dot Test with Angle.lbrn (46.3 KB)

Here is another file that can help determine if there is backlash in your system.

BacklashTest.lbrn2 (199.0 KB)


Hi Tim,

Thanks for this. Here’s the result of the test.

Test #1. I don’t know what officially qualifies as high speed. I ran this at 4000/60, which is a lot faster than I run any other project. But I imagine it depends on the laser.

Test #2. This one I ran at 1200/50 which was the pre configured rate.

Looking at this second test I notice the line appears thicker on the x axis.


You definitely have mechanical issues. Juist a few things I see. In the first test the horizontal lines should be evenly spaced, they are not. The circles aren’t round and don’t meet at the ends. The letters are misshaped. In the second test the lines don’t meet the circle at all locations and the circle doesn’t meet at the ends.

@misken has an excellent guide for testing and adjusting your diode laser here Guide to mechanical adjustments and maintenance It is written for Sculpfun I believe, but most diodes are similar.