Im building a large format printer and have been tuning the firmware recently. It uses a btt octopus and has 4 independent z steppers leveling out a 1/4 inch aluminum plate, one in each corner, with an ir probe to measure the height. It worked great for a while and could level out to within half a millimeter across 800 mm in 3 rounds of z tilt, but yesterday it stopped working.
I cant for the life of me figure out what changed, but now two opposing corners wont adjust to the same value as the other two. The print area is 800mm by 300mm and the measured points at 0, 0 and 800, 300 get down to about 1.3mm and the points at 0, 300 and 800, 0 go to about 0.6mm. The tolerance is set to 0.5mm and the retries are set to 5 so it either runs out of retries, or occasionally fails because the distance is increasing.
I’ve tried everything I could think of, I’ve changed the order of the points and which driver the motors are plugged into and its consistently the same motors regardless of the driver. Otherwise the motors work great. Ive checked for any mechanical issues and cant find any anything. Ive remeasured the tilt positions and slightly changed the coordinates that it measures. Because the issue is on opposite corners I don’t think theres an issue with the sensor being wonky on the gantry. It just seems like the z tilt calculation isn’t telling the motors to move as much as they need to.
Im attaching a klippy log from when it started and one from when it worked. Nothing changed in the config and nothing changed physically on the machine, I just left it for a couple days and came back to busted z tilt. Any ideas?
klippy_issue.log (279.4 KB)
klippy_no_issue.log (391.3 KB)
have you solved the issue, I have a similar problem
I got it to complete by moving the probed points in 50mm from the corners, but the issue was still there just small enough to work. I think it’s because correcting one corner changes the other 3, but I really have no clue. Z tilt might work best with 3 points instead of 4.
Hey so I spoke too soon. I found this and figured id give quad gantry leveling a try despite the warning about moving beds and it works perfectly. The math for Z tilt assumes the bed is flat and rigid so it cant actually account for the warping thats showing up. Quad gantry level, despite being for leveling a gantry does the math necessary to correct that warping.