Laser auto focus w/ 9.02

I was running LightBurn v 9.0 and updated to 9.02 today. Something changed with the way the auto focus is handled and it’s not working any longer with my normal settings. Is there an easy way to downgrade back to v 9.0 or earlier so I can get this job finished and figure out the issue later? Thanks

I switched back to 9.0 but the issue still persists. It’s adding 20mm to the height setting for some reason… Any ideas?

You should go back to 9.02 - it fixes some communications issues that exist in 9.00 and 9.01.

You probably have a setting such as material thickness that is causing this to happen, not a change in the software.

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Okay. I was thinking it was the upgrade because everything’s been working fine for the last couple months and I haven’t made any changes besides updating.

I double checked the material thickness, focus and offsets. All are set correctly and they should be as nothing has been modified lately. When I press start, the Z table moves down 14.64mm past the focus point for some unknown reason and starts engraving.

Try rebooting the computer and machine. All power off, verify controller is off, and let it sit for a bit.

So I figured out LightBurn is adding the material thickness each time I send the file. If I set the material thickness to 0.200" it will drop the table 0.200" before engraving. If I change nothing with the file, but send it to the laser to overwrite the current file it will drop the table another 0.200" before engraving. Whatever I change the material thickness to, that’s what it will drop the table by before engraving any new file regardless of the current height.

Rebooted everything and still doing it.

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In my tests to figure out the material height was the issue, the table height got down to 54.8mm So I re-focused the table to zero (7.36mm offset from my auto focus probe). Then I edit the material thickness to 0 thinking it will be a work around and send the new file. Press start and the table drops back down the 54.8mm

What’s going on here??

In the device settings, do you have “Relative Z Moves only” enabled? If not, enable that and try again. That setting tells LightBurn to read the Z height from the controller when you hit Start / Send, and uses that as the baseline height for everything, instead of zero. This way, you can leave the material setting blank, and all moves just happen relative to whatever your current Z height is. The Ruida is a bit of a pain in that it has no facility for sending relative Z moves as part of a cut job.

I didn’t have Relative Z Moves enabled so I tried that and it didn’t help. I’ve tried everything I can think of and I can not figure it out. Auto height control no longer works with version 9. I down graded Lightburn to 8.07 and auto focus is working again. Something changed w/ the update but unfortunately I can’t figure out what.

Did you have Z enabled before? When you say “auto focus is not working”, LightBurn has never done anything with auto-focus aside from having a button you could push to run the focus probe cycle, so I’m wondering if you just enabled Z and didn’t have that on before.

So here’s how I handle height control in v8:

After I touch the auto focus sensor on my laser to the surface of my material, the table automatically drops 0.290" which sets the focus point on the surface of my material for a 2" lens. All my material thickness’ are set to 0.290" (my laser focus point). I then offset my material depending on thickness; zero if I’m engraving, 0.625 inward if cutting 0.125" material, etc.

This was my workaround for v8 but no longer works in v9. Does this make sense?

Not really, no. It sounds a bit like you were using the “offset” property in each material instead of setting the material thickness, to get around the problem of it not handling your focus distance. If you set all material thicknesses and offsets to zero, you should be able to use “Relative Z Moves Only” from there.

Yes, I was using the Offset property in each material.

So if I set the material thickness and offsets to zero, how does it know what height to cut or engrave?

I think you’re saying to just use the Z Offset in the Cut Settings? It seems like that may work…

If you use auto-focus to the top of your material, you’ve already set the height, so there’s no need to move at all, is there? And no, I’m not saying to use the Z-Offset, I’m just trying to figure out how it should work. :slight_smile:

The auto-focus sets the focus point to the top of the material. If I’m cutting, the focus point should be to the center of the material. So for example, 0.250" thick material should move the focus point IN 0.125" to the center of the material. If I was engraving, no, I usually wouldn’t change the focus from the top of the material.

Ahh, ok. Yes, for that you would set the material thickness to zero, and just use the offset to push in by the correct amount, you’re right.

The material thickness value is primarily for systems like diode lasers that have a movable head, but no touch probe or manual focus method. Using manual or auto focus it’s much simpler to just use relative moves from the top of the material.

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So I can update my Library correctly, when I Edit Desc, is checking “No Thickness” the same as setting the thickness to 0mm?

Not quite - “No thickness” means it won’t alter the existing material height. Zero will set it to zero if you use a material set that way.