dab55
May 8, 2022, 11:26pm
1
I have a project with a single cut layer derived from a SVG image. Before sending the job to the laser I group all ellements of the image.
The job completes however, the ellements of the image are not correctly positioned as you can see from the attached image.
If I rung the job using LaserGRBL and the same SVG file and settings It completes corretly, as shown inthe attached image.
This tells me that I do not have a mechanical issue with my Chinese laser engraver or the settings on the DLC V2.0 controll board.
What is the source of the SVG that you are importing into LightBurn?
Are you able to provide the following?
Screenshot of Preview in LightBurn with this design
Actual SVG file
Actual LightBurn .lbrn file with design ready-to-burn
dab55
May 9, 2022, 6:09am
3
please find attached files as requestedAirTag_Sleeve CORRECTED.lbrn2 (62.9 KB)
dab55
May 9, 2022, 6:32am
4
These are the gcode files sent to the controller from Lightburn and LaserGRBL. I will send lightburn file attached to this post and The LaserGRBL file attached to a seperate post.
Lightburn
; LightBurn 1.1.04
dab55
May 9, 2022, 6:34am
5
The LaserGRBL gcode file
;G90 (use absolute coordinates)
dab55
May 9, 2022, 8:51am
6
Sorry berainlb I missed the question in your response. The SVG file came from AirTag Mold | Template for lasercutting by grumpy_scrambler - Thingiverse
The .lbrn file you attached has 2 layers: one offset fill layer and one line layer that seems to match the photos and the g-code output. Can you confirm you’re only running the line layer for your tests?
The preview you attached is showing both so a little confused there.
Assuming that you’re only outputting the line layer I don’t see anything fundamentally wrong in the g-code or .lbrn file. LightBurn is commanding the laser to do the right thing. For some reason the laser is not complying.
I think what may be going on is that your machine is losing steps somewhere. Looks to me like a loose belt situation or possibly a situation where you’re driving the motors faster than they can go. First do a mechanical review of your system as it’s best to address any physical concerns before trying to address this with settings.
When you run this in LightBurn do you hear a buzzing or straining noise from the motors? If not, more likely an issue with belt tension or possibly belt alignment. Belts should be taught with no slack but not stretched.
I suspect the reason why this is happening in LightBurn and not LaserGRBL Is because LightBurn is using rapid moves between individual shapes. The individual shapes are being burned at your cut speeds but rapid moves will go at the max travel speed as configured in GRBL. That is set to 10,000 mm/min ($110, $111) for you currently on both axes. It’s possible that is fast enough to expose any mechanical issues on your system. LaserGRBL seems to be using G1 and cut speeds for all movements. Did the burn in LaserGRBL take longer than LightBurn?
dab55
May 10, 2022, 12:54am
8
I can confirm that I am only burning the line layer from the SVG as I removed the offset layer before sending the job to the laser.
I have already checked belt tension and there is no unusual sounds from the steppers while in operation.
I will try lowering the fast move speed.
The order of the burn is totally different i Lightburn to LaserGRBL .
This is not the only job that I experience this trouble with. Most multi layer jobs have a registration problem with Lightburn resulting in the different layers being offset.
LaserGRBL doesn’t give you many options to tweak laser path but LightBurn gives you a number of tools in the cut settings and optimization settings. However, it’s not so much the optimization that’s causing the problem in this case if my hypothesis holds up.
If you load the LightBurn gcode in LaserGRBL you can see that the planned shapes are as you would expect. In looking at the g-code you can see that LightBurn is using G0 rapid moves to go between shapes. An issue here would explain why the individual shapes of the LightBurn sample look okay while the spaces between shapes is skewed.
I’m not aware of your specific setup but 10,000 mm/min may very well be faster than your machine is capable of going so worth exploring.
That wouldn’t surprise me. Basically anything that uses rapid moves would be a problem. In fact, even the start point of jobs may not be accurate as the laser head moves to the starting position.
dab55
May 10, 2022, 3:04am
10
I have checked all belts and rollers, turned of “Fast White Space” and re run the job.
Results are still the same, it burns the outline of the front then the stitch holes and front window, finishing with the back of the item.
The front and back of the item are positioned accuratly however, the stitch holes and front window are not as the laser is not moving the correct Y position before burning each of these.
I have attached a link to a video of the burn.Burn Video https://drive.google.com/file/d/1zV6P77MEkdJ_4Z2ME1KKFjUtY3E5ggrl/view?usp=sharing
I responed on private message but let me repeat here so that others can benefit.
You cannot change rapid move speed with “fast white space”.
Based on the video I’m fairly certain your motors are skipping based on the sound. Not certain but they sound strained.
You need to change the settings for $110 and $111. Do this either in Machine Settings or in Console. For example, you wanted to try setting to 5000 mm/min:
$110=5000
$111=5000
I suggest you start out low and test. If it works, you can incrementally increase the value until you notice skipping and then dial it back.
dab55
May 10, 2022, 5:58am
12
Thank you berainlb, I lowered these settings to 2000 and the job completes correctly.
I have avoinded tweeking the setiings in the Output Settings section of Machine Settings as Lightburn issues a warning about changing these setting
I have attached an image showing the output settings I have. could you please any other recomended changes.
Once again thank you. I have a smile from ear to ear.
Great news. Glad that worked.
Was this the upper limit of speed before your steppers would skip? This is a pretty low value. If not, I’d encourage you to experiment to identify that upper limit so you can take full advantage of your hardware.
Could he do a test card that starts at a low speed and incrementally speeds up until things go screwy?
dab55
May 10, 2022, 12:14pm
15
I did some more testing and 3500 seems to be the limit. I have 17hs4023 steppers brand name Usongshine.
I have fought with this machine for over a year trying to get it setup to use Lightburn and now it is working perfectly.
Oh wow. That must be an immense sense of relief.
I think you were a bit lucky in this case that LaserGRBL had different results than LightBurn. It provides a relatively easy comparative reference.
Now you can just enjoy the process rather than fighting the machine.
Try this:
Then go into DEVICES → OPTIMIZATIONS and then pick REMOVE and then pick “ORDER BY GROUP”. Make sure your CUT layer is the last layer you use. Also pick “Cut Inner shapes first” and also “Reduce Travel Moves”
With a properly tuned machine, none of these settings should affect whether the output works or not, just the order in which things are done.
dab55
May 11, 2022, 2:21am
19
Thank you Keith for you advise, I am like a sponge sucking up all the knowledge I can find when it comes to laser engraving and cutting.
dab55
May 11, 2022, 10:13am
20
one last question if I may. Are the $110 and $111 settings limitted by the stepper motor or THE STEPPER motor driver ?
