X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode  

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

That's a lot of detail 😉  Not necessary.

Here is what likely happened - one or more of your parts warped off of the plate, the head hit the edge after mooshing into the plastic for a bit of time, and then finally smashed into the part - causing the position sense to be knocked off by what you see.

Add brim.

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

Dan, That's a logical suggestion. I should have looked for warping before removing the parts. If I add a full height brim and the printer is running in normal mode will the printer stop if a part warps off the plate?

So far in all my prints (most variants of the short models you see in the picture)I haven't seen any evidence of parts warping off the plate. Am using "Strong PLA" which is made with the NatureWorks Ingeo 3D870 resin. It seems to be quite stable.

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

Do check your X belt tension as well - if it jumped a couple of teeth in an acceleration move, this same problem could happen.  There is a nice little PETG Gcode for belt tension meter that does a better job than the sensor based belt tension #'s.

Brim's aren't a full height thing - that's skirt, and usually not needed (skirt height) for PLA.  Brim is a flat extra wide bottom layer that the slicer can add in - try two MM and that will certainly tame any warping. 

Three things can make position jump like that.  Head hits print.   Something interferes with head (not sliding smoothly on rods).  Belt slips or pulley slips.

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

Also check the tightness of the grub screw on the X axis stepper.  The belt tension could be correct but if the grub screw comes a bit loose it could slip on the axle and also cause this.

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

Dan gave you a list of possible culprits, all plausible. Given the size and pattern of the shift I suspect the nozzle hit something. But checking belts should be on your todo list too. 

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

Thanks everybody for all the suggestions. Have another two hours on a current print and will investigate belt tension and check tightness on grub screws and more more when it's done.

Since getting the printer running about three weeks ago I have had to tighten the Y-axis belt.

Recently I've noticed a relatively high-pitched rattle like noise in certain movements that I didn't hear before. It reminds me a bit of something not being tight enough, that might be another clue.

I'll report back.

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

Posted by: @stephen-bannasch

[...] I bought the printer kit last August but just got it going about 3 weeks ago. I think it's an MK3+ but after assembling I can't find my sticker with serial number!

This is definitely a bit of a long shot, but if your printer is running firmware v3.8.1 and you're using OctoPrint, there was a nasty bug that would cause results that looked like layer shifts that popped up only on longer prints.

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

Posted by: @bobstro

Posted by: @stephen-bannasch

[...] I bought the printer kit last August but just got it going about 3 weeks ago. I think it's an MK3+ but after assembling I can't find my sticker with serial number!

This is definitely a bit of a long shot, but if your printer is running firmware v3.8.1 and you're using OctoPrint, there was a nasty bug that would cause results that looked like layer shifts that popped up only on longer prints.

Running firmware 3.9.3-3556 and still using the 16GB card and sneakernet to get the gcode from the computer to the printer.

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

I recently had a similar thing happen and saw there was a crash detected.  Belts seemed OK so I cleaned the rods and greased the bearings as described in the maintenance procedures and all has been well since.

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

I had lots of small tests to print before I could dig into the belt tension tonight. None of the small prints showed any problem. Just by feel the X axis belt felt a bit loose. I tightened it just a bit by loosening the top X axis motor mount screws and tightening an screw that pushed against the outer motor mount screw. Is that what folks here call the 'grub' screw? I'll need to take the back off the extruder and tighten the belt one or two few cogs soon. I'm at the limit of adjustment now.

I then ran the  belt calibration and the X-Axis reading changed from 249 to 257. Not the direction I expected with a small amount of tightening.

The belt calibration reported the Y axis was too loose to operate properly and when I turned theprointer on it's side the Y-axis belt felt loose to me too.

I took apart one end of the Y-axis belt clamping and adjustment system under the plate and shifted the belt tighter two cogs tighter and re-assembled. The belt tension feel right to me and here are the numbers the belt calibration reports (presumably these are before and after):

Checking X axis
X:258 -> 270
Checking Y-axis
Y:281 -> 279

Am starting a four-hour print now of the same parts. I was able to shrink the parts a a bit so in a future print when I print 12 it should  only be about 8 hours. 

I've left the mode set at Normal instead of Stealth so if there is a problem the printer is likely to stop and at least record a crash event.

RE: X axis offset 11 mm 60% of the way through 11 hour print overnight in stealth mode

Good luck finding and solving your problem.  "Grub screw" is a term used to refer to the small set screws that hold the pulleys to the motor shafts on the x and y axes.  Many times people who experience much smaller layer shifts than you will find that the pulley is loose on the shaft and rocks back and forth with direction changes.  This is commonly caused by not following the proper sequence for tightening these two screws on each pulley.  First tighten the screw that contacts the flat on the motor shaft and then tighten the second screw.  Properly tightened these screws rarely work loose.  Improperly tightened they will always loosen.

Regards,

Steve