After a crash, MK3S thinks X axis is further right than it should, even after full "Wizard" recalibration
After a good few days making spare parts for my new MK3S, the printer crashes while making the PSU-replacing brace for the lack enclosure out of PETG. I try to start all over again the next day, but when it goes to home, it grinds against the right extreme of the X axis and decides the best thing to do is check the Z axis. After trying several options in the menu that I think might fix this but to no avail, I decide to give up and just do a full recalibration using the wizard.
The wizard warns me that it will wipe all settings and start all over again. I accept, and let it do its thing. It passes all checks and with paper in place, it does the bed level thing and successfully finds all calibration points. Then it guides me through the PETG-to-PLA swap and goes to do the final Z-level adjust.
Except that it then homes to the old position and crashes on the right extreme again. Anyone know why it's retaining this memory of its false post-crash X-axis home position, and more importantly, how to fix it?
RE: After a crash, MK3S thinks X axis is further right than it should, even after full "Wizard" recalibration
Look at the crash counter in the LCD status menus. >0 means you have something dragging or bearings with too much friction.
Also - anything that prevents the extruder from bumping solid against the left Z-bracket is a show stopper.
Oh - and a loose drive gear or belt can cause this, too.
RE: After a crash, MK3S thinks X axis is further right than it should, even after full "Wizard" recalibration
Crash Counter: Total X=8, last print = 0. (Crash Y is zero). I can't tell what's due to the failed print and what's due to other factors, and I can't see a way to reset it to test that.
I can push the X carriage along when powered off and it gives resistance but no more than it did when it was functioning perfectly (I printed literally every single black part from the black/orange MK3S kit without a single error). It is free to move to the furthest extents in either direction.
The belt is tight and the drive gear is solid enough that holding the spindle in place prevents the X carriage from being able to move by any visible amount.
The misalignment on the X axis is such that even though it tested the X axis during calibration, smoothly moved from left to right without any problems then gave it the OK, and did the 4-point bed calibration perfectly, when it went to print it thought the home position (usually extreme left) was actually about 3cm from the right bumper. I'm not sure how it can slip that much between the start of calibration and the first test print for Z axis adjustment.
I have since tried again with calibration with some degree of success. In order I have done:
- Power off, push Y platter to far rear, X carriage to far left.
- Auto Home.
- Self Test. Result - X, Y, Z, Bed, Hotend: All OK. X axis reports it is now at position +12.0.
- XYZ Calibration: Finds all 4 calibration points, measures reference values at all 9 bed level points (all in the right place), reports calibration successful and X/Y axes are perpendicular. The calibration procedure stops with the nozzle a little bit up, right and backwards in reference to the plate as the usual home position. The X axis detected as +46.5.
- Auto home again. The Z axis moves down to the plate, the plate moves back to the start Y position, the X axis does nothing. Not even a squeak from the motor. However, it is now reporting X axis position as +12.0 again. This can't be right.
- This is obviously going to fail again as it's over 3cm away from where it thinks it is. So... Power off, push X/Y axes back to the home position, power on, Auto Home. Position is now +12.0 and looks like it's in the right place.
- First layer calibration:
- Point 1 calibration: Spot on (front left).
- Point 2 calibration: Spot on (front centre).
- Point 3 calibration: Spot on (front right).
- Point 4 calibration: Spot on (centre right).
- Point 5 calibration: Spot on (true centre).
- Point 6 calibration: WAY OFF (1cm to left of true centre).
- Point 7 calibration: Spot on (rear left).
- Point 8 calibration: Spot on (rear centre).
- Point 9 calibration: Spot on (rear right).
- Crash detected! (Crash X total now 9, Y still 0). It can't be an X axis move problem to my mind, because if it was, it would have failed to move to point 6 when it lost steps, and those steps would have stayed lost. It would have been stuck at that offset for points 7-9. It wasn't. It moved diagonally to point 7 and found it fine.
- Continues printing anyway. For no good reason I can think of, the pressure balancing initial stripe is 11cm too far along the Y axis but in the correct place for the X axis.
I've powered it off, and taken a look at the entire X axis. The motor pulley seemed to have shifted position slightly with the belt riding against the edge all the time, so I adjusted it. Now when I move the X carriage forwards and backwards it does drift a bit to the left and right, but doesn't touch the edges.
I've since done 3 first layer calibrations (It's difficult to get it in just the right place in just one pass) and it moved to all 9 points correctly. I'm now religiously auto-homing before each print, and I've left it printing a small part (I'm not letting it tackle the brace until it's proved itself) - so far it's about 4 layers in without any errors. Hopefully this will fix it, but I'm still confused about how the 9-point calibration failed point 7 but passed the rest. What would make it do that? If there is still a problem, then can it be explained by further X axis setup problems? Would I be looking at belt retensioning and/or bearing replacement/lubrication? I've set it up as best I can interpret the instructions. Currently the belt is as tight as it will go, and if I make it any looser then the X carriage can be moved by hand slightly when holding the spindle static with pliers. I've bought a spare set of bearings (from E3D) and a tube of lithium grease (From Amazon, MG Chemicals Lithium Grease, 85 ml Tube, White), and I've read the guide showing how to de-lubricate then re-lubricate them but I've got no good way of getting it neatly into the bearings as yet. I know there's an object for doing that with Loctite Super Lube - maybe this has the same thread dimensions but I've not printed one yet.
RE: After a crash, MK3S thinks X axis is further right than it should, even after full "Wizard" recalibration
try a factory reset with data clear and maybe upgrade to the new 2.8.0 firmware
RE: After a crash, MK3S thinks X axis is further right than it should, even after full "Wizard" recalibration
It finished the smaller print, and then the larger bracket without any problem. Then I found out that the bracket in the Lack enclosure that Prusa have in their blog only fits the silver PSU because of the different position of the Y frame bolts... And there is a new Lack enclosure v2 with the right shape frame for the black PSU that I have... So it's going in the bin and I'm starting again. I've done the firmware upgrade and tried the new print. Except this time it wouldn't seek to the mesh bed levelling positions correctly at all. First it failed at 6 and did 7, 8, 9 fine, then it failed at 6 and lost steps altogether for the remainder. I tried loosening the X belt, in case it was too tense, and it still failed. Then I noticed that the carriage was significantly more difficult to move than this morning, even with the looser belt. I gave the two rods an application of 3-in-1 oil the full length from both ends twice so the bearings would get as much of it as possible, and the cloth I used to apply it was jet black afterwards from the deposit it removed while doing it. Now it's seeming to do the seek correctly - I can only conclude at this early point that it is the bearings at fault, but the total print time on board is only 25 hours or so. I was very careful to install the bearings smoothly - Is it normal for bearings to start seizing up within that short an operational life?
RE: After a crash, MK3S thinks X axis is further right than it should, even after full "Wizard" recalibration
could be just the shaft seals on the bearings wearing in and dry bearings. also the dust level in your workspace may have an effect. I would plan on wiping the rods ( only the rods, never the Z leadscrews) with oil regularly