Hello, I recently started having issues with Lightburn when I wanted to change the Z height of my burn and needed to refocus the laser at the new height. When I went to use the “Fire” button for focusing, I noticed that it was burning into my workpiece (poplar at the time). I kept reducing the percentage next to the Fire button, all the way down to 0.25%, but it still burns into my workpiece.
I have the S-value max set to 1000 and all of the appropriate GRBL settings set each time I start the machine using a Macro, but it still is an issue.
I also tried to revert back to a last known working version of the software 0.9.24, but the issue persists.
I might try running a test on scrap of a few different types of cuts / fills at different speeds and powers to see if the laser is responding as expected.
I have done strip tests using different fills and the laser does respond to changes in percentage.
This only happens when using the “Fire” button and using the percentage next to that button.
Additionally, when I first started using the laser (about 6 weeks ago), I would have to set the percentage to 4% in order to get it to “fire” for a test.
Type $$ then hit ‘Return’ in the Console window. You will see a bunch of information spit back. Copy and paste the entire results (the console window will scroll) here for review.
If the control module fails, if can leave the “on/off” functionality intact but the power control broken (we see this on Ortur modules somewhat regularly). It’s possible this is happening here too.
Also check the $30 setting in the controller - XCarve controllers reset it automatically to 1, which causes all kinds of havoc with laser use. It should be 1000, to match the S-value max setting.
This is Shane with J Tech Photonics. I worked with Matt via a remote session on his computer. It’s worth mentioning that Matt is using LightBurn on a Mac. We checked his $30,$31, and $32 and they were set to the appropriate settings of 1000, 0, and 1 respectively.
We successfully fired his laser from the console using a M3 S10 command which resulted in the expected low power output. When the fire button on the move tab was pressed with a power setting of 0.25% the laser energized at what appeared to be 100% and started burning the scrap wood underneath it.
Matt stated to me that the fire button had worked in the past with the power set to 4%.
What is the ‘S-Value Max’ setting in Edit > Device Settings?
If you want to see what LightBurn is sending, you can enable the ‘Show All’ toggle in the Console window, and that will echo every command that LightBurn sends to the controller into the console window so you can see what it’s doing.
The ‘S-Value Max’ setting tells LightBurn what the $30 value is in your controller - if they don’t match, strange things can happen. If the value in LightBurn was set to 1000 and the $30 value in the controller was set to 250, for example, LightBurn would be sending commands with 4x the expected power level.
S-Value Max is set to 1000, and $30 is 1000 (set by a macro button when I initialize the machine). I can post a screen shot and $$ results if you would like to see those.
Try turning on the ‘Show all’ toggle in the console, then click the Fire button. Copy and paste the commands LightBurn is sending into a reply here so I can see them.
According to the GCode being sent, and your settings, that should be 0.25%. If it’s firing the laser at that power level, any of these could be it, or something else:
A bad laser module with a broken PWM circuit
A laser module that simply doesn’t support PWM
An incorrectly wired laser, where you’ve connected the TTL (on/off) line from the board to the PWM line of the laser
A broken controller whose PWM output pin is not working
