I have been chasing a recent problem with printing large models. In particular a large flat 2 color print 200x200x10 mm. I have printed this model over 12 times in the past without a mechanical problem. Lately when the layer gets above 55% [>5 mm] what was a near perfect layer [a few strings] becomes a field of Pine Trees and Valleys. This is my 3rd attempt and the same result.
Please note the previous layer is normal. [the one just below the damaged areas.]
I have printed this model several times in both PLA and PETG. But for the last 3 weeks or so I have not been able to complete a print. It requires about 7 hours to print on the X1C in PETG. While watching the printing at the 55% level it seemed to go well. Then as a I turned and walked away I heard a load grinding noise and felt the table that the printer is on shake. Unsure of the cause I looked for an outside cause and then the grinding sound reoccured and the table shook significantly enough to shake an empty box off the table. When I looked inside the near perfect print appeared as shown above.
Before you all start with “Wet Filament”, “Clean Plate”, and Maintenance issues, let me point out the filaments were all recently re-dried for 24 hours prior to use, the plates washed with only one small successful printing of a model 100x100x5 mm high, and just completed cleaning and oiling [Screws,Rods, lidar lenses, etc.] and calibrating. I also cannot do a time laps because it is not allowed under the LAN mode.
The only time I’ve had problems with large pieces was caused by warping. Are you using glue or a PEI plate? You can also try using a higher bed temperature and keep it there (not just the first layer). Also, are you leveling the bed with each print?
What infill pattern are you using? I’ve read many times that grid (due to the overlapping filament passes) can be high enough to snag the nozzle end.
This occurs with any size print where the height is more than 10 mm high, just before the Top most layer which is ironed. and mostly in the middle to front side of the plate. The print is not warped and is PETG filament.
But it is a grid which is the default pattern to a 100% Sparse infill.
It is on a PEI [look at image 770]and the X1 levels before every print…
" I’ve read many times that grid (due to the overlapping filament passes) "
Yes, but this is the default pattern for 100% infill and the strikes only occur at the top most levels. [ironing] I have observed the lower layers to be put down perfectly without a strike.
I have recently seen this nozzle strike occur with support structures causing them to break at various heights. You can hear the strike from [open door] across the room [10-15 feet.]
I found an interesting a secondary problem that maybe a contributing cause in my case. The Silicon boot on the nozzle is torn. [maybe from the repeated strikes.] That has led to a build up of filament under the boot, [especially with multi color prints and a thousand nozzle wipes], that eventually extrudes out near the tear thus allowing a secondary surface to grab the fresh laid filament. Eventually this does grow into a ball that destroys the print and wipes off the entire top surface.
Found the source of the problem, and it is the build plate. As I mentioned before only the top most layers >7mm of a 200x200 mm flat build seems to be effected. It did not matter what filament or slowing and heating of the plate. I even switched to a brand new Engineering plate to see if there was something I was missing with the PEI textured plate that I had been using. Again in the final minutes of the 6 hour print I noticed a movement at the edge of the plate. It was lifting off of the heat plate causing the print head to crash into the build. Thinking my old eyes were failing me I grabbed my iPhone and saw this…
Which resulted in this…
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Thank you for coming back and posting what you found. That’s definitely a problem. I wonder if there’s a home remedy though. 
