mixing extruder feedrate

I just trying to setup a mixing extruder, 1 nozzle with 2 extruders, firmware is work92 (latest update), Arduino-Due and Ramps-FD, Delta machine. 
I found that after I enabled the mix extruder setting,  the extruder stepper motor speed can not been controlled by feedrate value, either G1 E10 F400 or G1 E10 F1200, running in the same speed! Is it normal ? Or anything I missed ?


  • I would expect the same as you - faster extrusion. Only thing is extruders can often not extrude that fast (F400 = 6.6mm) so the motors might be loosing steps at both speeds. Except if run without filament and given that max. extruder feedrate is higher (to allow fast retraction) they then should turn faster.
  • Actually I really trying to run it without filament because I just want to test the extruders.
    If I set the MIXING_EXTRUDER to 0, the EXT0 can run as my expected speed, very fast extrusion/retraction. 
    But if I set the  MIXING_EXTRUDER to 1, it always run in the same slow speed 
  • I just found that the problem not caused by the mixing_extruder enabled. It happened when I set the NUM_EXTRUDER to 2. 
  • You just lost me. NUM_EXTRUDER 2 seems a logical choice for a mixing extruder.

    So you mean mixing extruder with 1 extruder is ok, with 2 extruders it is slow? Depending on mixing ratio they are slower, ok, but I guess you considered that already.
  • In my previous test, I set the mixing_extruder to 0 and num_extruder to 1 at the same time, then the problem gone. So, I guess the problem caused by mixing extruder settings, but I was wrong. 
    In my last test, I set the mixing_extruder to 0 in configure.h to disable mixing and then keep NUM_EXTRUDER to 2 such that it just same as a normal 2 extruders 2 nozzles config. Then the problem happened.
    I can sure the configuration no problem because I using it in my printer for a long time. For single extruder, it's working fine. But when I set the NUM_EXTRUDER to 2, no matter the MIXING_EXTRUDER is 0 or 1, Both extruder motor will run slowly and same slow speed for any F value

    Any suggestion I can try ?

  • I don't see an error here. My guess is that in eeprom some values differ and cause the problem.

    I also assume that with NUM_EXTRUDER 2 extruder 1 stills behaves normally?
  • "I also assume that with NUM_EXTRUDER 2 extruder 1 stills behaves normally?" -> NO...
    once set NUM_EXTRUDER 2, both extruders including  extruder 1 have the same problem...really strange...

  • Especially having 2 extruders work on so many printers. And also 2 extruder config should have no influence on first extruder. That is something I can also not understand.

    What you can do is compile with
    #define DEBUG_QUEUE_MOVE

    enable echo and do a few pure e moves. In the log you will see some computations especially here how many steps for how 
    many mm are planned and timings. Maybe they give some hints what gets computed wrong.
  • Just fixed the problem by refresh the eeprom... maybe some corrupted data inside the eeprom caused the abnormal behaviour.

    Thanks Repetier
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