Filament Overrides - Retraction Length acting strange  

Filament Overrides - Retraction Length acting strange

Hi everyone,

There is a strange issue I have been recently facing when using the Filament Settings / Filament Overrides / Retraction / Length setting. I will detail what has been happening:

I have been using PrusaSlicer 2.2.0 for a few months now, and despite some early hurdles (caused by my lack of knowledge), it has been my go-to slicer for the vast majority of my prints.
Yesterday I switched filament on my printer from Spectrum PLA Pro Rust Copper to Sakata3D Green PLA. I had been using both brands before with good results, but as always when I insert a new filament I start with the same test prints for material fine tuning. After tuning maximum flow rate I found out that I needed to bump from the usual 200 degrees Celsius to 210 (could be my recently installed steel nozzle), but while using this temperature the filament was a tad bit runnier, so I decided to use the filament-based retraction override (which I had used before).

I have a modified Creality CR 10 MAX printer with direct drive (Bondtech clone) and Volcano hotend, hardened steel nozzle, so my usual retraction distance is 1mm. With this filament I have changed it to 1.5mm from the Filament Settings / Filament Overrides / Retraction / Length setting. That's the only entry I have activated in the above-mentioned menu, everything else was disabled. I then started printing a test model, namely the Autodesk x Kickstarter FDM 3D Printer Assessment (which I had used before). Issues started with first layer directly, after a string of several quick-succession retractions, the extruder started skipping, and didn't recover until I canceled the print. This usually tells me there might be a clog or the nozzle could be too close to bed.
For clog checking, I raise the nozzle, keep hotend hot and manually extrude material in mid-air using G90; G1 E50 F100 commands. That worked fine, no skipping.
The nozzle was not too close to bed because I am using ABL with mesh checking which is being performed before every print, and the extruder skipping issue always started at the same exact point during the first layer, every time, like clockwork.

After several reslicing and retries, pulling my hair why is this happening, I have noticed something while monitoring the direct drive. The extruder system gear ratio is 3:1, an I have been looking at the white visible plastic wheel turning, and while I can't accurately measure its rotation, it seemed to travel more then expected during retractions. I had a hunch, so I went to Filament Settings / Filament Overrides / Retraction / Length setting and disabled it completely, leaving just the default setting from Printer Settings / Extruder 1 / Retraction / Length.

Sliced again, started printing... no more extruder skipping.
Changed that setting from 1mm to 1.5mm, sliced again, started printing... no more extruder skipping.

I am puzzled because I had been using this override before, with good results. However, it now looks like the override, for some reason, adds the override amount to the default retraction length setting, at least based on my empiric observation of the behavior. I also looked at the GCode but couldn't find anything wrong with it.

Below is an excerpt of retraction flurries which always cause this using the override:

G1 X227.567 Y204.192 F9000.000 ; move to first infill point
G1 F1800.000
G1 X227.501 Y204.098 E1.56565 ; infill
G1 X227.419 Y204.226 E1.56648 ; infill
G1 E0.06648 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X227.570 Y199.800 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.50000 F2400.00000 ; unretract
G1 F1800.000
G1 X227.501 Y199.902 E1.50068 ; infill
G1 X227.427 Y199.788 E1.50143 ; infill
G1 E0.00143 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X217.578 Y199.783 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.50000 F2400.00000 ; unretract
G1 F1800.000
G1 X217.501 Y199.902 E1.50082 ; infill
G1 X217.434 Y199.805 E1.50150 ; infill
G1 E0.00150 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X217.437 Y204.189 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.50000 F2400.00000 ; unretract
G1 F1800.000
G1 X217.501 Y204.095 E1.50064 ; infill
G1 X217.572 Y204.205 E1.50138 ; infill
G1 E0.00138 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X207.571 Y199.799 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.50000 F2400.00000 ; unretract
G1 F1800.000
G1 X207.501 Y199.904 E1.50070 ; infill
G1 X207.434 Y199.805 E1.50137 ; infill
G1 E0.00137 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X207.437 Y204.189 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.50000 F2400.00000 ; unretract
G1 F1800.000
G1 X207.501 Y204.094 E1.50062 ; infill
G1 X207.564 Y204.188 E1.50124 ; infill
G1 E0.00124 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X199.246 Y207.276 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.50000 F2400.00000 ; unretract
G1 F1800.000

And below is the same code, with 1mm retraction instead of 1.5mm:

G1 F1800.000
G1 X227.500 Y204.094 E1.06584 ; infill
G1 X227.423 Y204.212 E1.06662 ; infill
G1 E0.06662 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X227.432 Y199.804 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.00000 F2400.00000 ; unretract
G1 F1800.000
G1 X227.500 Y199.905 E1.00068 ; infill
G1 X227.570 Y199.800 E1.00138 ; infill
G1 E0.00138 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X217.570 Y199.799 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.00000 F2400.00000 ; unretract
G1 F1800.000
G1 X217.500 Y199.905 E1.00071 ; infill
G1 X217.432 Y199.804 E1.00138 ; infill
G1 E0.00138 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X217.569 Y204.196 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.00000 F2400.00000 ; unretract
G1 F1800.000
G1 X217.500 Y204.094 E1.00068 ; infill
G1 X217.423 Y204.212 E1.00146 ; infill
G1 E0.00146 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X207.570 Y199.799 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.00000 F2400.00000 ; unretract
G1 F1800.000
G1 X207.500 Y199.905 E1.00071 ; infill
G1 X207.432 Y199.804 E1.00138 ; infill
G1 E0.00138 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X207.569 Y204.196 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.00000 F2400.00000 ; unretract
G1 F1800.000
G1 X207.500 Y204.094 E1.00068 ; infill
G1 X207.423 Y204.212 E1.00146 ; infill
G1 E0.00146 F2400.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.600 F9000.000 ; lift Z
G1 X199.247 Y207.277 ; move to first infill point
G1 Z0.200 ; restore layer Z
G1 E1.00000 F2400.00000 ; unretract
G1 F1800.000

I see no problem with them. Code looks good, which keeps me scratching my head.
Anyone else having encountered this same issue? Could it be hardware-related? Could it be filament-related? Again, it's a setting I had used before with no issues.

Thank you for going through this rather long read, and apologies if I omitted some detail, in which case please let me know and I'll answer.