They’re finally trying to do inline on Luban. Which you’re now experiencing the exact bug I pointed out way back in 1.14 that I described in an old post below. (and is why I had made custom firmware)
They’re no longer using M3/M5 to turn the laser on and off, instead turning it on with M3 or M4 and then inline power changes to control the laser. However, when the laser should be “Off” it calls for S0 which, in theory, should turn the laser off by setting the power to 0. However, a very old commit instead makes S0 turn the laser on at either full power or the last power it was before, instead of off. This is very dangerous.
This is now the default output from Luban, I suggest downgrading until this is fixed in the firmware.
As far as the “constant power” option goes, it simply swaps M4 for M3, which is a GRBL thing and does nothing in a Marlin based system for laser. (in CNC mode, M3 is clockwise, M4 is counter-clockwise) On a GRBL system (XTool, 3018, Ray, etc) M4 would allow the controller to adjust the laser power down and up to compensate for deceleration and acceleration of the toolhead to prevent burns in corners/small details where the laser can’t reach full speed. M3 is “constant power” mode, wherein it remains at your set power, no matter how fast/slow the toolhead is going, and can cause burns in small details and corners.
TL;DR Old dangerous bug still there, Luban now does “inline” by default, the constant power toggle is useless. Downgrade Luban to 4.8.0 or lower if you’re on stock firmware until it’s fixed, or if you’re on my old firmware, test out the new inline feature in Luban 4.9.0!
EDIT: As an interim solution, export the gcode to file > open in a text editor such as Notepad++ > Ctrl-H to bring up the “replace” dialog box > Replace ALL S0 with S1 > Save and load into workspace and run, or load onto machine. This sets the power level of the laser to 1% so it won’t be powerful enough to burn and give you the effect of it being off. This is what I did in the images while testing in the above forum post.
EDIT2: Oh boy! They didn’t do inline for dot-filled engraving. So this is going to be the exact same, stuttery, stop/go image engraving as before. However they’re doing inline in “Line-filled” engraving, which if it worked, would be exponentially faster. (Luban’s own ETA for a test image was 7 hours in dot, and 39 minutes in line). Sadly? With the bug stated above, all you’d get would be a solid block of black, as S0 would keep the laser on. @VaporPhoxxe Try a line filled engraving of a grayscale image, replacing S0 with S1 please? 