Still massive stringing problems with my A20m

[DzzD]

Old topic but here are some very interresting informations.

Retraction on mixing extruder just do not work as expected, and this is the key of stringing problems.

Basically when one side/filament is retracted, it suck from the other side/filament rather than from the nozzle , that's why the retraction just does not have any effect...

Here are some more informations

https://github.com/MarlinFirmware/Marlin/pull/11941

I found a solution that mitigate the problem when printing with one PLA filament I just use a higher temperature filament in the second extruder (ABS for example)

Here is Marlin 2 Configuration_adv.h settings you have to change to enable extruders synchronized retraction and completely remove stringing problems

Code: Select all

#define FWRETRACT
#if ENABLED(FWRETRACT)
  #define FWRETRACT_AUTORETRACT           // Override slicer retractions
  #if ENABLED(FWRETRACT_AUTORETRACT)
    #define MIN_AUTORETRACT 0.1           // (mm) Don't convert E moves under this length
    #define MAX_AUTORETRACT 15.0          // (mm) Don't convert E moves over this length
  #endif
  #define RETRACT_LENGTH 5                // (mm) Default retract length (positive value)
  #define RETRACT_LENGTH_SWAP 13          // (mm) Default swap retract length (positive value)
  #define RETRACT_FEEDRATE 45             // (mm/s) Default feedrate for retracting
  #define RETRACT_ZRAISE 0                // (mm) Default retract Z-raise
  #define RETRACT_RECOVER_LENGTH 0        // (mm) Default additional recover length (added to retract length on recover)
  #define RETRACT_RECOVER_LENGTH_SWAP 0   // (mm) Default additional swap recover length (added to retract length on recover from toolchange)
  #define RETRACT_RECOVER_FEEDRATE 8      // (mm/s) Default feedrate for recovering from retraction
  #define RETRACT_RECOVER_FEEDRATE_SWAP 8 // (mm/s) Default feedrate for recovering from swap retraction
  #if ENABLED(MIXING_EXTRUDER)
    #define RETRACT_SYNC_MIXING         // Retract and restore all mixing steppers simultaneously
  #endif
#endif

Important : after flashing your firmware, you must send gcode M209 S1 to enable FWRETRACT_AUTORETRACT(this will enable conversion of your G1 E to firmware retract/unretract gcode while printing)

Hope it helps !!!

@admin : maybe this post should be stick as I have not seen around a lot of right answers (exept commons : lower your temp, increase your retract etc...) for stringing problems on mix extruder printer

[Jdbye]

Old topic but here are some very interresting informations.

Retraction on mixing extruder just do not work as expected, and this is the key of stringing problems.

Basically when one side/filament is retracted, it suck from the other side/filament rather than from the nozzle , that's why the retraction just does not have any effect...

Here are some more informations

https://github.com/MarlinFirmware/Marlin/pull/11941

I found a solution that mitigate the problem when printing with one PLA filament I just use a higher temperature filament in the second extruder (ABS for example)

Here is Marlin 2 Configuration_adv.h settings you have to change to enable extruders synchronized retraction and completely remove stringing problems

Code: Select all

#define FWRETRACT
#if ENABLED(FWRETRACT)
  #define FWRETRACT_AUTORETRACT           // Override slicer retractions
  #if ENABLED(FWRETRACT_AUTORETRACT)
    #define MIN_AUTORETRACT 0.1           // (mm) Don't convert E moves under this length
    #define MAX_AUTORETRACT 15.0          // (mm) Don't convert E moves over this length
  #endif
  #define RETRACT_LENGTH 5                // (mm) Default retract length (positive value)
  #define RETRACT_LENGTH_SWAP 13          // (mm) Default swap retract length (positive value)
  #define RETRACT_FEEDRATE 45             // (mm/s) Default feedrate for retracting
  #define RETRACT_ZRAISE 0                // (mm) Default retract Z-raise
  #define RETRACT_RECOVER_LENGTH 0        // (mm) Default additional recover length (added to retract length on recover)
  #define RETRACT_RECOVER_LENGTH_SWAP 0   // (mm) Default additional swap recover length (added to retract length on recover from toolchange)
  #define RETRACT_RECOVER_FEEDRATE 8      // (mm/s) Default feedrate for recovering from retraction
  #define RETRACT_RECOVER_FEEDRATE_SWAP 8 // (mm/s) Default feedrate for recovering from swap retraction
  #if ENABLED(MIXING_EXTRUDER)
    #define RETRACT_SYNC_MIXING         // Retract and restore all mixing steppers simultaneously
  #endif
#endif

Important : after flashing your firmware, you must send gcode M209 S1 to enable FWRETRACT_AUTORETRACT(this will enable conversion of your G1 E to firmware retract/unretract gcode while printing)

Hope it helps !!!

@admin : maybe this post should be stick as I have not seen around a lot of right answers (exept commons : lower your temp, increase your retract etc...) for stringing problems on mix extruder printer

That's very useful information. I have been struggling with stringing issues, but I chalked it up to my cheap filament (HobbyKing PLA) since it doesn't seem to happen to everyone. Increasing retraction to 4mm/50mm helped a bit, but the issue still persists, although I have lived with it since it just takes some postprocessing and the prints look good. The issue is multiplied whenever I try to make multi color prints though and the result is really bad.
I hope your suggestion will help me as well.
But where did you find Marlin 2.0 for the Geeetech A20M?

Edit: Thank you! I expected to see the extruders moving in tandem, but weirdly the secondary one did not seem to move much (it didn't move for the 15 seconds I was looking closely), maybe it doesn't work the way I think it does. However, the stringing is almost completely gone now, even on the super problematic retraction test. That's awesome.
I found Marlin 2.0.1 for the A20M on Thingiverse, it's working well.

Edit: Before and after. The difference is impressive.

[Spideryon]

Hi, i have also this problema with my a20t, Will this work for 3 extruders??

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