Under extrusion after retracts and dimensional errors on Delta



  • Hello people!

    I have now finally gotten to make a few small prints on my DYI delta printer https://www.duet3d.com/forum/thread.php?id=4000
    At the moment my setup is:
    Bondtech QR extruder
    40 cm Capricorn PTFE tubing
    E3D Chimerra - 0.4 mm nozzle (So far only using one of the nozzles)

    I have calibrated my extruder steps to be spot on.

    This are the relevant pieces of my config.g (not complete)

    [[language]]
    ; Drives
    M350 X16 Y16 Z16 E16 I1                                               ; Configure microstepping with interpolation
    M92 X200 Y200 Z200 E475                                             ; Set steps per mm (477 from bondtech manual)
    M566 X1200 Y1200 Z1200 E900                                      ; Set maximum instantaneous speed changes (mm/min)
    M203 X40000 Y40000 Z40000 E4000                                    ; Set maximum speeds (mm/min)
    M201 X3000 Y3000 Z3000 E3000                                       ; Set accelerations (mm/s^2)
    M906 X1100 Y1100 Z1100 E880 I30                                      ; Set motor currents (mA) and motor idle factor in per cent
    M84 S15                                                                  ; Set idle timeout
    
    ; Tools
    M563 P0 D0 H1  F1:2                                                          ; Define tool 0
    G10 P0 X9 Y0 Z0                                                          ; Set tool 0 axis offsets
    G10 P0 R0 S0                                                              ; Set initial tool 0 active and standby temperatures to 0C
    M572 D0 S0.05                                                          ; Setup pressure advance
    
    

    I must say, that i am generally very happy with the looks of my prints and i believe this printer can become very good! Here my third print:

    However a few things is still to be addressed.

    1. A 20 x 20 x 20 cube measures 19.8 x 19.9 x 20 (x,y,z). I have done 6-factor auto calibrations and are down to 0.016 deviations when i run a G32. Can this dimensional error be related to a delta arm value that is to low? If i think of it, i would rather think that to low a value would create a print that was to large and not to small. Am i wrong?

    2. My other issue is something that have been haunting me for all my 3D printing adventures, both with my trusty old Hephestos Prusa with a cheap E3D clone j-jhead to a expensive Core XY with E3D V6 and dyzend.
    I always get under extrusion after retracts.. (Pressure advance mittigates this effect a little but it is there with and without) Here is an example of my issue:
    This part looks absolutely amazing.. until the thin section where retractions start to really happen. It is easy to see that when retractions happens for the first time, i get under extrusion.



    This example print was printed at:
    40 mm/s
    200 degree nozzle
    55 degree bed
    ColorFabb black PLA
    1.8 mm of retraction at 30 mm/s
    0.2 mm layer height

    Does anyone know what may be causing my problems? (I know there is a peremiter gap, but that is due to mismatch of extrusion width and model thickness)



  • Sorry for the image quality..


  • administrators

    1. It's better to use a larger test cube to check dimensional accuracy, to reduce the effect of any under or over extrusion. If after that you still find the dimensions a little under, then print a grid pattern over the whole bed to check linearity. If the grid lines are parallel and evenly spaced, don't adjust the configured arm lengths, instead use M579 to adjust the scaling.

    2. How much pressure advance are you using?

    If you are getting consistent under-extrusion after retraction, then the "extra length on restart" parameter in the slicer may help you, although I've never needed it.



  • 1. Okei i will try that whenever i have time!

    2. I think this is the pressure advance:
    M572 D0 S0.05
    So not a lot i think.

    It is not always when i retract it seems to be a little random. And adding the extra restart length gave issues on my other printers. Haven't tried it on this one. I thin k i might have missed some fundamental knowledge about 3D printing because i always had this issue to some extend.
    On the Core XY i mentioned it looked like random under extrusions and then sometimes over extrusions. This is a picture from testing back then. I do not remember much of the settings though. But it was also short retractions around 2 mm.

    Back then i thought i retracted to much so sometimes it would slightly jam and then suddenly over extrude as the jam cleared. Buuut i am not so sure anymore. I was using the minimal amount of retraction to avoid stringing.



  • Okay, I am sloly going crazy..

    How can these two prints both be printed at the same settings!!!!?



    When printing the cube everything looks absolutely normal.


    When printing the bottom of the pyramid everything looks normal.
    As soon as the small sections start all shit breaks loose.. I can see that it underextrudes when it begins on a tower, then suddenly the next tower overflows extremely and so on. I sometimes hear the extruder grinding (i have a very low tension on the QR arm of the bondtech - tightening the screw removes grinding but changes nothing on the print)

    They where printed at 40 mm/s
    200 degrees
    0.2 mm layer height
    No retraction
    No pressure advance
    100% colling fans (temeperature is staple +- 1 degree at max.)

    S3D is set to relative extrusions, so is the config.g
    Temperature seems to be correct-ish. 180 gives grinding when just extruding into the air. 190 -220 works. 230-240 works but clearly to liquid 250 starts to smell burned.

    I have absolutely no idea where to look..

    Here is my full config.g

    [[language]]
    M111 S0                                                                 ; Debugging off
    G21                                                                     ; Work in millimetres
    G90                                                                     ; Send absolute coordinates...
    M83                                                                     ; ...but relative extruder moves
    M555 P1                                                                 ; Set firmware compatibility to look like RepRapFirmare
    M665 R147.796 L335 B130 H223.915 X-0.202 Y-0.102 Z0.000                 ; Set delta radius, diagonal rod length, printable radius and homed height
    M666 X0.28 Y-0.09 Z-0.20                                                ; Put your endstop adjustments here, or let auto calibration find them
    M208 Z0 S1                                                              ; Set minimum Z
    
    ; Endstops
    M574 X2 Y2 Z2 S1                                                       	; Set active high endstops
    
    ; BlTouch
    M307 H3 A-1 C-1 D-1 ;							;?
    M558 P5 X0 Y0 Z1 H2 F100 T10000						; Set Z probe trigger value, offset and trigger height
    G31 X0 Y-19 Z2.4 P25 							; Set Z probe offsets, trigger height, and trigger value
    M557 R110 S20                                                           ; Define mesh grid
    
    ; Drives
    M569 P0 S1                                                             	; Drive 0 goes forwards
    M569 P1 S1                                                              ; Drive 1 goes forwards
    M569 P2 S1                                                              ; Drive 2 goes forwards
    M569 P3 S1                                                              ; Drive 3 goes forwards
    M569 P4 S1                                                              ; Drive 4 goes forwards
    M350 X16 Y16 Z16 E16 I1                                               	; Configure 16th microstepping with interpolation for all drives
    M92 X200 Y200 Z200 E470                                             	; Set steps per mm (466 from cal 477 from bondtech)
    M566 X1200 Y1200 Z1200 E900                                      	; Set maximum instantaneous speed changes (mm/min)
    M203 X40000 Y40000 Z40000 E2700                                    	; Set maximum speeds (mm/min)
    M201 X3000 Y3000 Z3000 E10000                                       	; Set accelerations (mm/s^2)
    M906 X1100 Y1100 Z1100 E900 I30                                      	; Set motor currents (mA) and motor idle factor in per cent
    M84 S15                                                                 ; Set idle timeout
    
    ; Heaters
    M307 H0 S0.50 A90 C700 D10 B0                                		; Use PID on bed heater 
    M305 P0 T100000 B4725 C0 R4700                                          ; Set thermistor + ADC parameters for heater 0 - bed
    M143 H0 S120    							; Set max bed temerature
    M307 H1 A288.7 C130.7 D3.4 B0                                           ; Use PID on heater 1
    M305 P1 T100000 B4725 C0 R4700                                          ; Set thermistor + ADC parameters for heater 1
    M143 H1 S280  								; Set max temerature for heater 1
    M307 H2 A288.7 C130.7 D3.4 B0                                           ; Use PID on bed heater 2
    M305 P2 T100000 B4725 C0 R4700                                          ; Set thermistor + ADC parameters for heater 2
    M143 H2 S280                                                            ; Set max temerature for heater 2
    
    ; Tools
    M563 P0 D0 H1 F1:2                                                      ; Define tool 0
    G10 P0 X9 Y0 Z0                                                         ; Set tool 0 axis offsets
    G10 P0 R0 S0                                                            ; Set initial tool 0 active and standby temperatures to 0C
    M563 P1 D1 H2 F1:2                                                      ; Define tool 1
    G10 P1 X-9 Y0 Z0                                                        ; Set tool 1 axis offsets
    G10 P1 R0 S0                                                            ; Set initial tool 1 active and standby temperatures to 0C
    
    ; Fans
    M106 P0 S0.9 I0 F100 H1:2 T50                                            ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned on
    M106 P1 S0 I0 F100 H-1                                                   ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M106 P2 S0 I0 F100 H-1                                                   ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned off
    
    ; Custom settings are not configured
    
    

    Does anyone know where i can start?



  • How about a screen shot of your Extruder tab in S3D?



  • Of course!

    As the error could potentially be anywhere here are all the relevant tabs from S3D







  • Okei, not much time for testing, but managed to do one small test today. I wouldn't say i got any wiser on the issue but i have hope that it has nothing to do with my printer (hardware or firmware).

    The black one you know (disregard that it has a misshapen bottom - i got impatient and ripped it off the hot bed..)
    The white one is the one i printed today (remember, no retractions whatsoever):

    The only thing i did was: Turn on printer. Heat the nozzle to 200 degrees. Remove the black ColorFabb filament(not even a "Atomic pull"). Install a 5 year old white makerbot leftover. Then just re-print the g-code file already uploaded to the printer.

    … Now this strongly suggests that the issue lies with the filament. However, i did not considder ColorFabb to be a bad brand at all! Also it does not explain why the black cube printed fine.. It seems like the black filament prints fine as long as the print has a more or less constant filament flow. As soon as the filament flow pauses i get issues..

    My next test will be to try again with the black filament on a cold machine like today. This way i can eleminate heatcreep in my hotend as the issue. I do not belive that is the issue however as i use a 40 mm powerfull fan instead of the stock 35 mm E3D fan. Additionally the cube was printed right AFTER the pyramid without the printer cooling down in between.

    I am happy if it is just a filament issue, but i just cant belive it. Either way, I still have absolutely no theory of why the black cube and pyramid are so different (same filament after all)


  • administrators

    It looks to me that the black one was printed at much too high an extrusion temperature. Different brands of filament need different temperatures.



  • Then how does that explain that the small cube i showed above is printed fine?
    It is printed at exactly the same settings and with the same filament as the pyramid.

    When it prints the pyramid it looks like there is a short delay from print move starts til plastic is extruded, then suddenly a big pile of filament is extruded. Can this be caused due to too high temeprature? Also, extruding into free air at the given temperature seems to work fine..


  • administrators

    With large parts you can get away with excessively high temperatures or insufficient cooling because when it prints perimeters, by the time it finishes the first one and starts the second, the first perimeter has cooled sufficiently to become solid. That's why the base of the pyramid is ok. What's happening at the sides is that when the second perimeter is printed, the first one is still molten, so it is being pushed out of place by the second one.

    Solutions:

    1. If using slic3r, set a low speed for "small perimeters". Slic3r has had this setting for at least 4 years, but sadly the other slicers still don't provide it.

    2. Reduce extrusion temperature.

    3. Increase print cooling.

    4. Reduce print speed.


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