I start the test. X and Y go through the motions but Z doesn’t move at all; it stays at Z397.37. Then when the test is done Z moves in the Z- direction faster than it should be able to; it goes faster than the limit in my firmware (and faster than the Z speed I have set under ‘move’) and causes some of the motors to skip steps…tilting the bed. So the only time Z moves is at the end…and then it moves wrong.
Machine is a CO2 laser running Marlin 2.1.1 on an Octopus.
Is Z- up or down? Also, how do you know it’s moving faster than firmware limits? I’m wondering how that would even be possible other than a firmware bug or similar.
Do Z movement controls in Move window work correctly? How many steppers do you have for Z-axis?
So the Z- speed is confusing; the fact that it moves faster than the speed in the firmware is probably a marlin bug…but it shouldn’t be moving at all at that point, and I’d think the speed should be able to be limited by software somehow? Z- is moving the bed up…towards the laser nozzle. Can’t move Z+ because it’s already at home.
Normal Z movements work perfect. Z homes, z moves up and down in the ‘move’ pane. If I tell it to move to Z50 it moves to Z50. I have 4 motors for my z axis.
I believe by default LightBurn will attempt to return Z back to starting position at the end.
I assume this is managed in firmware? I’m curious if this would be enforced based on the speed issue.
I can’t recall if LightBurn uses the speed setting in Move window also for Z operations but you could potentially try reducing the speed there to see if it makes a differnece.
One thing I’m seeing is that you have relative Z moves on in Device Settings. My understanding of relative Z moves only is that LightBurn wouldn’t attempt to account for absolute positioning of Z, but only relative moves from current position. In that case, I’m wondering if your Start Z value may be causing an issue. Perhaps try setting height manually, then setting Start Z to 0.
Alternatively, try disabling “Relative Z Moves” only.
If none of those things work, can you save the Gcode for the focus test and post here?
That partially fixed it (turning off relative z). It now at least attempts to move the bed up when it starts. Still moves it too fast so it tilts. The Z speed in move is set to 10mm/s. The firmware is also set to 10mm/s. I’ve tested and I start to have problems when moving faster than 18mm/s so I should have a lot of headroom.
Looking at the G code I can already see some issues. It seems to like using G0 for some reason, which I think Marlin dislikes because Marlin doesn’t even have a place to specify G0 speeds as far as I am aware. I also see it ends by trying to move to a position my laser cannot move to…although it fails long before it tries that.
Turning off relative Z fixed it. I also had to lower the default acceleration in the firmware (because I guess I’m using G0 now). Now if I can just get it to not try to crash the machine when it’s done, that would be great.
I didn’t think LightBurn would attempt to send the head to anywhere it hasn’t already been but that could be wrong, especially with relative moves disabled. LightBurn is not going to know that values below 45 are off limits but I would expect the firmware to account for that.
You should consider trying relative moves with the manual start as that would likely prevent crash scenarios.
It is actually limited by the firmware; when it tries to move to Z0 it only goes to Z45. Problem is that I have a piece of wood on the bed so Z45 is a crash. I’m going to change my min Z to Z80 to work around the problem but Light Burn is still trying to crash my machine…firmware just won’t let it.
Also any idea how to turn off the G0 moves? In marlin all G0 moves are the same speed…so x and y moves are insanely slow to match the speed of z moves.
There’s no way to disable G0 moves in LightBurn as far as I know. LaserGRBL has a feature to avoid G0 moves but not sure what type of Z controls are available.