After drawing diagonal and circular lines, they come out curved.
Hi @Jacz
Could you post a photo of the result, along with a screenshot of the same design in LightBurn?
Hi Jose,
This appears to be what we call a lost-motion issue. Generally, this is caused by slack/slop in the motion system of your laser. Could you please give your laser diode/gantry a wiggle and see if you can feel any looseness in the system? Your belts should be taught and lightly twang when plucked.
Hi, I checked the belts and they are tight; before it started malfunctioning, I simply cleaned the lens with isopropyl alcohol.
What puzzles me the most is that the misalignment also appears in the LightBurn designs.
Can you upload the .lbrn2 file? I do not see this in your images above.
@Jacz, if you removed and cleaned the lens just before checking, then your lens is properly seated, not cracked or broken, and the housing is not loose or cross-threaded, etc.
It doesn’t look like the lens is damaged; I performed the cleaning simply by removing the air pump nozzle.
I don’t think it’s the laser, as I ran a test with an infrared laser and got the same result—the lines come out distorted.
Checking the belts is not enough. They are just a small part of the mechanics. You need to do a full check. Go through the guide mentioned on the setup-page: Sculpfun iCube Ultra - Diode Laser Wiki
and this guide:
Guide to mechanical adjustments and maintenance
Was the IR on a different frame, or did you replace the diode module with an IR module?
Trying again. We need to see if what you describe is in the program you are using to get your images from. We also need to know if that is your design or was it imported. If imported, what was the file type it had?
Yes, the machine can switch between diode laser and IR.
I’m sharing the LightBurn file, the preview, and the final result, which shows that the lines came out wrong.
Muestra.lbrn2 (51,5 KB)
I don’t see any issue here, but still, just go through the mechanics guides, this will fix your issue with 98% probability 
I will go with 99.8% because I saw nothing in the Lightburn file matching the output.
Your vertical moves (Yaxis) are decently straight but the horizontal moves (Xaxis) have the wiggles. This suggests the Xaxis is remaining still as it travels along the Yaxis. Conversely, traveling across horizintally shows movement in the Yaxis direction.
I have an iCube machine, so I am guessing the most likely fault is in the rails (wheels), not in the belts. But @misken is correct suggesting you give it a complete mechanical checkout.
The link below takes you straight to adjusting the wheels, but the entire web page is relevant.
The evidence does not confirm this option.
That’s what I have to repeat a lot: the belts are usually NOT the issue. The belts are just a very minor part of the mechanical system. Check the pulleys, grub screws, lubrication of the rails etc. With the iCube, you should also run the system with the top cover opened to check if the cables get in the way. Additionally, you need a firmware update to avoid the cables moving the laser head once powered off. It’s explained in my articles above.
I know the belts aren’t everything; I checked the other parts of the machine and they all seem tight—nothing looks loose. I also updated the laser machine using an update shared by Sculpfun, and now I’ve noticed that when moving the head toward the back—almost reaching the end—it makes a slight sound, as if the belt teeth were rubbing against the ring holding them.
I’m not saying they are not adjusted, but if you’re around here very long this doesn’t mean too much. How long have you had the machine and how many times have you done a successful adjustment?
How did you set it?
This is clearly mechanical. You can swear up and down it isn’t but it clearly is mechanical. The one on the left, from Lightburn preview isn’t even close.
When it’s going somewhere it changes the axes it messes up. This appears to be where the Y axes should be pretty much steady but isn’t. It could be lots of things, not nessarily a belt.
This works better with a square or rectangle box and I’d give that a shot to see if the fault really stick out
How could you do this in software, unknowingly?
We’re here to help, not drag you over the coals, so don’t take it as unkindly. 
Good luck.
Hi, I don’t take it the wrong way; on the contrary, I appreciate the support and your comments. I’ve had the machine for about three months now, and today I’ve confirmed—just as you suggested—that the issue lies with the machine itself, since I ran a test in LaserGRBL and got the same error. I’ve checked the guides you pointed out and believe I’ve adjusted everything correctly, so I’ll keep trying until it’s fixed.
Believe it or not, we will do the same for you until it is fixed or you quit talking to us.
By the numbers…
- If you tilt the machine with the power off, is it hard to move at all, or drop like a rock?
- With the top off, can you twist the laser module and feel any kind of movement?
- If you grab the bottom of the laser module, can you twist it sideways or front to back?
- If you move the laser module around by hand, are there any places it gets tight, loose, or seem to slip suddenly?
- Can you move the laser module straight up and down vertically at all?
You should not feel any play or looseness in any step after #1.
When you have answered all these, then we will go to the next step, the couplings.