Prusa upgraded to duet, weird extrusion

  • Greetings again!

    I have set up my Prusa MK2.5S/Bear Extruder/Full Bear/Duet 2 WiFi upgrade combo and so far it seems to print at least. 🙂

    I am facing weird looking extrusion artifacts I have never seen before though..

    On one axis, I am getting intense vibrations, like, I can feel them with my nail:

    2019-12-09 20.05.15.jpg

    The other axis side gets moire effect I have seen on Prusa github issues with MK3 owners..

    2019-12-09 20.05.06.jpg

    My config is as follows:

    ; Configuration file for Duet WiFi (firmware version 2.03)
    ; executed by the firmware on start-up
    ; generated by RepRapFirmware Configuration Tool v2.1.3 on Sat Nov 30 2019 21:16:45 GMT+0200 (Eastern European Standard Time)
    ; General preferences
    G90                                       ; send absolute coordinates...
    M83                                       ; ...but relative extruder moves
    M550 P"Prusa Bear MK2.5"                              ; set printer name
    ; Network
    M552 S1                                   ; enable network
    M586 P0 S1                                ; enable HTTP
    M586 P1 S0                                ; disable FTP
    M586 P2 S0                                ; disable Telnet
    ; Drives
    M569 P0 S1                                ; physical drive 0 goes forwards
    M569 P1 S1                                ; physical drive 1 goes forwards
    M569 P2 S1                                ; physical drive 2 goes forwards
    M569 P3 S0                                ; physical drive 3 goes backwards
    M584 X0 Y1 Z2:4 E3                        ; set drive mapping
    M671 X-36.0:290.0 Y110:110 S1             ; Set the Z motor relative locations correction 1mm
    M350 X16 Y16 Z16 E16 I1                   ; configure microstepping with interpolation
    M92 X100.00 Y100.00 Z400.00 E138          ; set steps per mm
    M566 X600.00 Y600.00 Z12.00 E150.00       ; set maximum instantaneous speed changes (mm/min)
    M203 X9000.00 Y9000.00 Z360.00 E7200.00   ; set maximum speeds (mm/min)
    M201 X1000.00 Y1000.00 Z200.00 E10000.00  ; set accelerations (mm/s^2)
    M906 X600 Y600 Z600 E800 I30              ; set motor currents (mA) and motor idle factor in per cent
    M84 S30                                   ; Set idle timeout
    ; Axis Limits
    M208 X0 Y-4 Z0 S1                         ; set axis minima
    M208 X250 Y210 Z210 S0                    ; set axis maxima
    ; Endstops
    M574 X1 Y1 S1                             ; set active high endstops
    M574 Z1 S2                                ; set endstops controlled by probe
    ; Z-Probe
    M558 P1 H0.85 F600 T12000 ;A3 S-0.03      ; set Z probe type to switch and the dive height + speeds
    G31 P500 X23 Y5 Z0.625                    ; set Z probe trigger value, offset(original 0.875) and trigger height
    M557 X24:228 Y6:210 S50                   ; define mesh grid
    ; Filament Sensor
    M591 D0 P2 C3 S1
    ; Heaters
    M307 H0 B0 S1.00                          ; disable bang-bang mode for the bed heater and set PWM limit
    M305 P0 T100000 B4725 C7.060000e-8 R4700  ; set thermistor + ADC parameters for heater 0
    M143 H0 S120                              ; set temperature limit for heater 0 to 120C
    M305 P1 T100000 B4725 C7.060000e-8 R4700  ; set thermistor + ADC parameters for heater 1
    M143 H1 S280                              ; set temperature limit for heater 1 to 280C
    ; Fans
    M106 P0 S0 I0 F500 H-1                    ; set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M106 P1 S1 I0 F500 H1 T45                 ; set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
    ; Tools
    M563 P0 D0 H1 F0                          ; define tool 0
    G10 P0 X0 Y0 Z0                           ; set tool 0 axis offsets
    G10 P0 R0 S0                              ; set initial tool 0 active and standby temperatures to 0C
    ; Custom settings are not defined
    ; Miscellaneous
    T0                                        ; select first tool
    ;M572 D0 S0.104                           ; pressure advance test

    If anybody could see if anything is really wrong with my config, I would really appreciate this. 🙂

    Right now the cube I have is perfectly 20x20x20mm and 0.45mm walled. So I would just love to get rid of these artifacts..

  • @Veti

    So basically my frame is so good(at least stiff) that the stepper drivers being "cheap" is showing now? Now that's a paddlin'. 😐

  • yes. i had the same problem. i kept improving my printer until i arrived at those artefacts as well.
    took my a while to figure that one out. replaced a lot of other parts before swapping to 0.9 stepper drivers.

  • @Veti

    Did you swap just X and Y steppers or all of them?

  • @Murloc992 said in Prusa upgraded to duet, weird extrusion:

    Did you swap just X and Y steppers or all of them?

    i only swapped x and y
    (be aware i only found out they have no cut shaft, but they work nonetheless.)

  • @Veti said in Prusa upgraded to duet, weird extrusion:

    (be aware i only found out they have no cut shaft, but they work nonetheless.)

    You mean no flat spot?

  • yes. i mainly got them because those were the only ones with swappable cable.

    a good alternative are the steppers suggested here

  • @Veti

    Maybe you have pics of print results with E3D motors? I have some motors with same specs to buy locally, but E3D are.. cheaper?

  • @Veti

    Thank you. Now I just need to wait till my steppers arrive and update this post. 🙂 Going to change X/Y and E.

  • So I've upgraded my motors to E3D ones:


    Now I have a WEIRD pattern that comes from the extruder motor:
    2019-12-18 00.51.44.jpg
    2019-12-18 00.51.46.jpg
    (I know, my first layer is too high, I just wanted to test ASAP)

    I can hear the extruder motor making such "patterned noise"..

    I have started at 1000mA current(both driver and motor cool), then tried to make it 1400mA(driver a bit hotter than lukewarm, motor cool/warm) with no change in behavior. What is this artifact?

  • @Murloc992 said in Prusa upgraded to duet, weird extrusion:

    Now I have a WEIRD pattern that comes from the extruder motor:

    are you sure its from the extruder? how does it look if you switch back to the old motor on the extruder?

  • @Veti

    I am sure, it's making pulsing noise even when spinning alone, without any plastic or idler engaged.. The old one doesn't pulse.. I have tried increasing microsctepping and disabling interpolation (nothing), reducing current(nothing), increasing current to maximum(heat increased only)..

    This is the best I got:
    2019-12-18 09.24.51.jpg
    2019-12-18 09.24.58.jpg

    The pattern is uniform on all sides.

    Last time I had it was when I had too thin wires for my motor on an old printer and wires were heating up. But these are E3D cables, I haven't even changed the pins, tried different cables too and they are not heating up at all even at maximum current..

    The one I had on my old printer was extreme.. and fixed after changing the extruder cabling.
    2019-02-26 22.15.54.jpg

  • Maybe this could be related to low voltage? I use 12V. Also I got an advice to attempt to reduce microstepping of the extruder motor to 8 microsteps. I will lose the interpolation though.. Will this matter?

    Need an expert here. 🙂

  • Moderator

    I'd say that somewhere in your extruder drive, a gear is running eccentrically, or there's some other mechanical factor that's causing the the filament to speed up and slow down as it passes through the extruder. Is the stepper motor geared to the hobbed drive, or directly connected? I'd look if the gear on the motor shaft is running eccentrically, due to the hole being off centre, particularly if it's a geared extruder drive, as this would give the short frequency of over/under extrusion you're seeing. If you're using Chinese cloned gears (I think the Bear uses Bondtech BMG parts), this is quite likely!

    Edit: Could also be caused by using very coarse hobbed drive.


  • @droftarts

    This might be a possibility. I use a genuine Prusa MK2.5S that was torn apart and resurrected into a Full Bear + Bear Extruder + Duet + New motors(now).

    The gears are genuine Bondtech, extruder is as direct as it gets (Bear Extruder), but I wonder how can it be eccentric.. With old motor I didn't have this.. Maybe a difference in flatspots? Or could it have happened if I tightened onto the flatspot a bit angled? Maybe a bent motor shaft (I hope not..)?

  • Moderator

    @Murloc992 Quite possibly one of those! As it's so consistent, I'd think it has to be mechanical. If you can't spot anything obvious, maybe refit the old motor and revert extruder settings in config.g?


  • @droftarts

    Every time I have to take the extruder of a prusa apart(including the wiring loom) I die a little inside, but I guess I will have to if I can't center the main gear.. 😞

    Will need to upgrade the extruder wiring loom someday to use a PCB at the back, so the wiring loom will be independent..

  • Moderator

    The fact that you can hear it pulsing makes me think it's the motor itself. Does it still sound like that if you run it free of any connection to the extruder gearing?

  • The motor shaft is straight, the gear is straight. Motor switch didn't help. All of them pulse. I will try reducing my microsteps to 8.. Maybe somebody knows about a TMC parameter called "Velocity"? I remember there's some register adjustments but I can't find it at the moment..

  • @Phaedrux It does, in fact, all the 0.9 degree motors I bought sound like that. Even without load.. I suspect that I need to adjust something in the drivers themselves. I used 1.8 degree steppers, now I got 0.9 degree ones.

  • Moderator

    What is the power supply?

  • @Phaedrux Whatever came with Prusa MK2S originally.. 12V and I guess 20A? Maybe 15A, not sure.

  • Moderator

    Can you post the results of an M122 command after doing a print?

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