Sporadic layer shifting

[pottedplant73]

That raised band isn’t supposed to be there. I printed 3 of these in a different color Bambu PETG and had no issues, but then this ridge appeared when I switched to orange Bambu PETG. Layer shifts seem to happen sporadically, from model to model, with no apparent rhyme or reason.

Print settings:

Filament: Bambu PETG Basic
Nozzle: 255C
Bed: 70C
Flow ratio: 0.95
Volumetric speed: 13mm/s^3
Filament start gcode:
; filament start gcode
{if (bed_temperature[current_extruder] >80)||(bed_temperature_initial_layer[current_extruder] >80)}M106 P3 S255
{elsif (bed_temperature[current_extruder] >60)||(bed_temperature_initial_layer[current_extruder] >60)}M106 P3 S180
{endif}

{if activate_air_filtration[current_extruder] && support_air_filtration}
M106 P3 S{during_print_exhaust_fan_speed_num[current_extruder]}
{endif}

Filament end gcode:
; filament end gcode
M106 P3 S0

Things I’ve tried to get rid of the shift:

Belt tensioning

Cleaning the carbon rods and cleaning/lubricating the stainless steel rods

Running printer self-calibration routine

Things I haven’t checked/tried yet:

Checking stepper motors for overheating

Enabling 'automatic recovery from step-loss' option in Bambu Studio

Maybe there’s something obvious here I’m missing. Maybe this isn’t even a layer shift, technically? Not sure.

[JonRaymond]

Just a heads up that this isn’t a layer shift. A layer shift moves the entire model away from its origin because of a step loss. There are also other reasons. A layer shift doesn’t return to its original position several layers up. It stays shifted. It also isn’t only on one face. CoreXY machines shift different than Cartesian machines. Generally cartesian machines shift in X or Y while CoreXY shifts in a combination of X and Y.

I would investigate the gcode preview. 8 wall loops is a lot and the slicer might doing something weird.

[pottedplant73]

Thanks for the clarification–I don’t know why I thought that was a layer shift, looking at other obvious examples of layer shifts. And yeah, 8 perimeters now seems pointless in terms of offering more rigidity. I’ve printed a new one with 4 perimeters and kept infill at 20%, and superficially the two seem just as strong.