Inconsistant layer height changes and lowering Z to cause nozzle to drive into model with Cura 4.8 slicing for a CR-6 SE

[jfulton-ak 0]

I am using Cura 4.8 with a Creality CR-6 SE and CR-6 Max.

 

When I sliced the Maker's Muse Printmas Christmas Tree Lattice, I blew it up to 400mm height, the max of the CR-6 Max. About 100 layers in, Z shifted back to 0, broke one of the limbs of the tree and drove the head into the base of the print, and the next layer went back up to the next height. At first I thought it was a corrupted SD card until I fed the GCODE file via Octoprint and I caught it doing the same thing again. Like a fool, I deleted the gcode file and resliced it and it printed fine this time.

 

Roll ahead 3 weeks now and I sliced BabyGroot.stl by Medelis and I experienced another odd inconsistent layer issue. I still have attached the gcode. Around layer 680 it switches from my selection of .12mm layer height to .16, then to .2, .2, and back to .12. This happens again at layer 689 going to .16, .2 for 4 layers, .16 for 3 layers and then back to .12.

 

At layer 804, it switches to .16, then layer 805, it does NOT change the Z height. It does this again on layer 809.

 

I did not find it yet in there, but somewhere it must have dropped the Z height downward because I came back into the room to the model popped off of the buildplate with an impression of the nozzle in the top of the model's head and it was printing spaghetti.

 

I used the default settings for the CR-6 SE with a .4mm nozzle, .12 super quality adjusting the print speed to 75, temp to 210, build plate to 65, and seam to sharpest corner with no support, 3 skirts at 5mm away.

BabyGroot-SE.zip

[GregValiant 904]

There are no Z moves in that file larger than your Z-hop height of .2mm.  Whenever it goes up .2mm for a Z-hop, it comes back down .2mm to the working height.

According to the settings listed at the end of the gcode file, Adaptive Layers is turned on.

 

[metadata]
position=0
type=quality_changes
quality_type=adaptive
setting_version=16

 

Varying the layer heights to the model geometry is what Adaptive Layers is supposed to do.

[jfulton-ak 0]

Thank you GregValiant. I do not know how I enabled that as I am looking now in Cura and it is unchecked. I normally select New Project as I flip back and forth between my CR-6 SE and CR-6 Max and like to have the settings wiped clean each time.

And after staring at the G-code for long enough, I see on those few layers where I didn't see an initial Z height change, that it was there a few lines above.

I do need to find why it is driving the head down into the model though. I haven't found where in the file that happens or if my printer is having a brain fart at that point. Although with this print file, it reproduced it twice. May try again and watch it when it does it since I know the approx point it happens, maybe I can watch the layer count.

[GregValiant 904]

I read  the Gcode file using a macro in MSExcel.  It found 59,878 Z moves and none went down by more than .2mm.  That isn't enough to crash the head.

Since you sent the file via Octoprint as well as by SD, that eliminates the possibility of a bad SD card.  I'm not sure what to look at next.  Sometimes a piece of infill or the edge of an overhang will stick up.  When the print head comes by again later it catches the part sticking up and pushes the model over.  I suppose it could get cocked and catch on the nozzle to leave a mark.  I increased my Z-hop height to .5 because of things like that (but it never got caught on the nozzle).