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Sometimes my Extruder will start spinning pointlessly fast and long.

Youtube Video showing the problem

This Issue only happens:

  • When printer has finished a Layer and moved up to the next (right after the Z axis has moved)
  • Not on all, but only on some layers of a print.
    Typically it will be more towards the middle of a print, and it will happen on several (maybe 10, 20, or a lot more) consecutive layers

My regular Setup/Stack:

  • PrusaSlicer-2.0.0+win64-201905201652
  • Octoprint (Version 1.4.0)
  • Tevo Tornado (with Mamorubot print-platform)

I have tried to test whether the source of the problem could be Octoprint or the slicer/gcode.

Octoprint:
The problem persists, when i print directly from SD

slicer/gcode:
Here is some gcode, one of a layer change where the problem did occur and one where it was fine: Problem occured here:

G1 X167.854 Y170.305 E209.95401
G1 X167.851 Y132.289 E210.24063
;BEFORE_LAYER_CHANGE
G92 E0.0
;3.95

G1 Z3.950 F7800.000
;AFTER_LAYER_CHANGE
;3.95
G1 X168.141 Y131.859
G1 F3600
G1 X129.532 Y131.858 E211.24663
G1 X128.945 Y131.592 E211.26340
G1 X128.419 Y131.004 E211.28396

No Problem occured here:

G1 X168.288 Y170.558 E474.06508
G1 X168.224 Y170.259 E474.06950
G1 X168.213 Y131.857 E474.62495
;BEFORE_LAYER_CHANGE
G92 E0.0
;9.8

G1 Z9.800 F7800.000
;AFTER_LAYER_CHANGE
;9.8
G1 X168.559 Y131.441
G1 F3600
G1 X129.622 Y131.440 E475.63947
G1 X129.198 Y131.248 E475.65161
G1 X128.776 Y130.777 E475.66807

I cannot see any problem with the gcode.

Now I am at my wits' end - what could be the source of the problem, and how to I proceed to debug it?

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    $\begingroup$ Where is the G92 E0.0 on layer change coming from? Because it looks like you're setting E to 0, but then after moving in the X/Y, your first move has to spin it all the way to 470-something. Are you sure you're not seeing this on every layer change? $\endgroup$
    – Davo
    May 21, 2020 at 17:57
  • $\begingroup$ Looks like the remnants of a deleted postprocessing that switched to relative mode to do something with extruder then back. $\endgroup$ May 21, 2020 at 19:16

1 Answer 1

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Doing some googling, it looks like the BEFORE_LAYER_CHANGE comment in the G-code and stuff that follow come from the before_layer_gcode setting in your PrusaSlicer profile. Somehow, G92 E0.0 got in there. Remove it and the problem should go away.

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  • $\begingroup$ The code G92 E0.0 was in the 'before layer change' settings in prusaslicer, I don't know how or why. After removing this, it seems to work wonderfully. I was just really confused, because that problem occured so irregularely, and after the z-axis had spinned, while this code was in there before the z-axis commands. $\endgroup$
    – IARI
    May 22, 2020 at 7:08

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