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.

The problem persists, when i print directly from SD

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
G92 E0.0

G1 Z3.950 F7800.000
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
G92 E0.0

G1 Z9.800 F7800.000
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?

  • 2
    $\begingroup$ 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 '20 at 17:57
  • $\begingroup$ Looks like the remnants of a deleted postprocessing that switched to relative mode to do something with extruder then back. $\endgroup$ – R.. GitHub STOP HELPING ICE May 21 '20 at 19:16

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.

  • $\begingroup$ 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 '20 at 7:08

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