Why is the filament being retracted?

General Discussion
1

Basic Information:

Printer Model: FLSUN QQ
MCU / Printerboard: MKS
Host / SBC: Pi 3B
klippy.log.zip (22.0 KB)

Describe your issue:

Have a look at VID_20240604_c.zip (359.7 KB). It shows the filament going back and forth while my printer is printing the bottom of a cube, this part:

image

The corresponding part of the GCode looks like this:

G0 F12000 X6.853 Y-8.419
G1 F3600 X8.419 Y-6.853 E38.88573
G0 F12000 X8.419 Y-6.288
G1 F3600 X6.288 Y-8.419 E38.98596
G0 F12000 X5.722 Y-8.419
G1 F3600 X8.419 Y-5.722 E39.11282
G0 F12000 X8.419 Y-5.156
G1 F3600 X5.156 Y-8.419 E39.2663

For what it’s worth I do have firmware_retraction enabled:

[firmware_retraction]
retract_length: 2.6
retract_speed: 60
unretract_extra_length: 0
unretract_speed: 60

My question is, why is the filament going backwards during this part of the print? There are no G10/G11 commands and the E value is steadily increasing. What’s going on here?

The GCode viewer in fluidd also shows retractions, but strangely only on the first layer:

image

Here’s the gcode file: tb_test.gcode.zip (56.4 KB)

2

Most likely you are seeing the effect of Pressure Advance.
Your setting of 1.04 is extremely high and could be indicative to various issue:

  • Long bowden
  • Low quality bowden
  • Bad bowden couplings
  • Unlocked bowden couplings
  • Generally low extruder quality or worn out extruder

Respectively, one or any combination of the above.

3

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