I hope someone will be able to help me solve the problem that I have been dealing with for about a month now. The issue started suddenly, after finishing a project using a GRBL laser. About 5 minutes after the job was done, I restarted the machine, but noticed that the circles were not cut evenly – the start and end of the circle didn’t align, causing a “tooth” to form instead of a smooth circle. After placing the piece back into the hole and rotating it 180 degrees, it no longer fit. Now, the “tooth” seems a little smaller, but the circle is still not a perfect circle. On one axis, it is distorted by about 1 mm.
I then switched to LightBurn (trial version) to check if the issue persists there as well. Unfortunately, after looking through many threads and similar topics, I found that the problem still occurs.
I’ve already taken several steps to try and fix the issue, including:
Disassembling and reassembling the machine several times.
Replacing the lens.
Changing the gears from MXL to GT2, as NEJE’s support team acknowledged that the gears were defective.
Replacing the belts with new ones.
Tensioning the belts.
Performing X and Y axis calibration, since I noticed deviations when cutting a 10x10 cm square.
I also tried the “Hide Backlash” option, but the problem persists.
Despite these efforts, the issue remains unresolved. Has anyone encountered a similar situation or have any suggestions on how to solve this problem?
Thank you in advance for any help or advice.
the first 2 photos are from the beginning of the month, the next 2 are after subtracting the steps I mentioned in the subsections
Hello, I think it’s a bit of hardware wear in the Y axis. The +Y and -Y motion have a shift value. I didn’t find on Lightburn a way to compensate for this offset. Check the gears (teeth) and their axes that can create this offset. The belt can also cause this effect but it has been replaced. The frame of the machine must be perfectly tight without play. The stepper motor axis may also be the source of the problem but this is also the most rewarding element.
I replaced the gears with new ones to fit the GT2 belt, they are properly tightened – I checked this several times, nothing is loose. The frame is also well tightened (I even tried attaching it to the table because I initially thought the frame might be moving on the table due to the motion). Additionally, I tried swapping the right stepper motor to the left side and the left one to the right, thinking one of them might be defective, but unfortunately, this didn’t help.
This is almost certainly going to be a mechanical issue, or at least something on the hardware side. As your tests have demonstrated this is not an issue with software, as-in the instructions to the controller are likely correct.
To me this looks like a backlash issue on the Y-axis. It also looks like the amount of backlash is variable so may be impacted by acceleration. Review all couplings on the machine with particular focus on the Y-axis. Check that the pinion gears are properly secured to the stepper shafts. If you have a coupling on the Y-axis shaft make sure it’s properly secured and not able to slip.
It’s possible this could also be due to the machine being under too much tension. With the machine off, are you able to freely and effortlessly move the laser head around the entire area of the bed? If there is resistance that could be to over tensioning of belts or alignment wheels. Identify the source and relieve it.
Est-ce que les cercles sont générés (vectorisés) par le logiciel lightburn?
Il est possible de vérifier si la fin de code est correct en céant un cercle avec Lightburn et enregistrant l’image du cercle au format GCODE puis de le lire avec BLOC-NOTE.
Le point initial G0 doit correspondre au point final sans décalage.
exemple.
