Print Shifted, what would cause that
I have a part I am trying to print using PETG and have something really strange going on. The X axis seems to be shifting on me (see pictures). I have tried the print twice and the shift is by different amounts and at different heights. Any idea on what in the world would cause this. It is like the machine is losing it's datum in the X axis. The part was still stuck to the plate so it wasn't the part shifting, it had to be the print head on the X axis. The belt is good and tight and I have tried to see if it is possible to have it skip a gear and there is no way it can do that.
Any ideas here?
RE: Print Shifted, what would cause that
The most common cause for layer shift is nozzle impact on the print while the nozzle is in motion or a belt motion problem.
PETG has a tendency to curl up on the edges of corners when insufficient cooling occurs. Your print has a large footprint and significant infill that could cause the extreme left and right edges to lift off the build due to contraction forces. In your first pic it looks like the left and right bottom edges may have lifted. If this is what happened the printer will continue to add filament as sliced resulting in over extrusion over those areas. Some of the over extruded filament will make the layer thicker than it should be and potentially interfere with the nozzle movement. There are indications of excessive extrusion bulges on the vertical walls over the left and right edges. In your first and second pics the shift occurred along the edt3es and bridging areas of holes which is consistent with the nozzle strike theory.
You could try adding brims, but due to the size of your print you may also have to reduce the infill % around the edges to limit the contraction forces as the bottom cools down. You could also increasing bed temperature or put a box over your printer to prevent air currents in your room from causing excessive cooling near the build plate.
RE: Print Shifted, what would cause that
What Lynn said, almost certainly warp enduced crashes resutling in x-belt shifting (do you print in normal mode with crash detection switched on?)
In addition to Lynn's advice: Clean the bed or use a different one if you have, everything to increase adhesion.
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RE:
Adhesion isn't the problem. Both attempts the part was firmly stuck to the bed all the way across. I am going to try it again by increasing the bed temperature. I have a enclosure over the printer already.
I have noticed that it does have build-up spots as it prints where the plastic is sometime "blobbing up" on the service. Any idea on what to do to prevent that from happening? That only seems to happen when I print PETG.
Also, I took the pictures after I had already removed the parts. Didn't think to take them when the part was still stuck to the bed. I'll do that this next time if it happens again.
RE: Print Shifted, what would cause that
Which firmware version did you use? It is well known that 3.13.2 shows layer separation. I found ( see my recent post) that 3.13.3 stil caused separation on my prints. Flashed 3.13.1 and it printed perfectly!