Banding on tall parts



  • Ok, so I have tried printing my first really tall print (200mm out of the max 230mm) and I noticed about 6cm up banding started and go progressively worse. Here is a picture of what I am seeing. This is on a delta printer with the smart effector.

    Not sure where to even start. This is new to the DuetWifi and smart effector and the subsequent hardware as the original electronics and such didn't have this.



  • It looks like backlash to me. Do you have springs on your arms to limit backlash? Also, what print speed?


  • administrators

    What is the pitch of the vertical banding?

    From the photo, there is one point on the perimeter of the cylinder where there is no banding, all the way up. Which tower does that position align with?



  • Its not a perfect circle but an interesting pattern that is repeated. I will try to take a close up but its too small for my camera. The pitch is a perfect 5.5mm which is suspect.

    The almost "no banding" is actually close to the bed. I am printing the parts again and will take a picture prior to removing them. It is hard to tell what it aligns with. Again new to Delta's. Forgive me if this is standard but the towers are set with one on each side (front) and one in the middle (back). It seems to be perfect aligned from left to right so I am not sure which tower that aligns with. Its perfectly horizontal with the back tower (z?). Also, while it shows no banding at the bottom, I restarted the print and I can see some minor banding probably because I am paying attention.. Below is the config file for reference.

    [[language]]
    ; Configuration file for Duet WiFi (firmware version 1.20 or newer)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool on Fri Mar 16 2018 21:17:52 GMT-0400 (Eastern Daylight Time)
    
    ; General preferences
    G90                                      ; Send absolute coordinates...
    M83                                      ; ...but relative extruder moves
    
    ;*** The homed height is deliberately set too high in the following - you will adjust it during calibration.
    M665 R115 L288.18 B115 H220.9                 ; Set delta radius, diagonal rod length, printable radius and homed height
    M666 X0 Y0 Z0                            ; Put your endstop adjustments here, or let auto calibration find them
    
    ; Network
    M550 PDelta                              ; Set machine name
    M552 S1                                  ; Enable network
    ;*** Access point is configured manually via M587
    M586 P0 S1                               ; Enable HTTP
    M586 P1 S0                               ; Disable FTP
    M586 P2 S0                               ; Disable Telnet
    
    ; 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
    M350 X64 Y64 Z64 E32 I0                  ; Configure microstepping without interpolation
    M92 X320 Y320 Z320 E815.14                  ; Set steps per mm
    M566 X1200 Y1200 Z1200 E1200             ; Set maximum instantaneous speed changes (mm/min)
    M203 X18000 Y18000 Z18000 E3600          ; Set maximum speeds (mm/min)
    M201 X1000 Y1000 Z1000 E1000             ; Set accelerations (mm/s^2)
    M906 X800 Y800 Z800 E800 I60             ; Set motor currents (mA) and motor idle factor in per cent
    M84 S30                                  ; Set idle timeout
    
    ; Axis Limits
    M208 Z0 S1                            ; Set minimum Z
    
    ; Endstops
    M574 X2 Y2 Z2 S1                         ; Set active high endstops
    
    ; Z-Probe
    M558 P5 R0.4 H10 F1000 T2400              ; Set Z probe type to effector and the dive height + speeds
    G31 P100 X0 Y0 Z-0.2                         ; Set Z probe trigger value, offset and trigger height
    M557 R115 S10                            ; Define mesh grid
    
    ; Heaters
    M305 P0 T100000 B3950 C0 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 S300                             ; 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
    M106 P2 S1 I0 F500 H-1                   ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned off
    
    ; Tools
    M563 P0 D0 H1                            ; 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
    
    ; Automatic saving after power loss is not enabled
    
    ; Custom settings are not configured
    
    ; Miscellaneous
    T0                                       ; Select first tool
    M501
    
    


  • Are you using wheels or rail? Maybe one of your wheels has a flat spot.



  • I am using linear rails. I checked them and they seem fine. If it helps it’s based on the anycubic linear plus.



  • Also in response to a question earlier I don’t have springs on the arms but I wouldn’t expect backlash to be so large. Speed is 2000mm/min. Typically backlash shows as an echo on turns not later over later variantions. This seems more like calibration is causing an issue or some other random issue that I don’t have enough experience with. Deltas are cool but man they are tough to debug. Part of the charm I guess.



  • I don't think it is calibration, calibration shows up at the start of the print most times. It seems mechanical to me.



  • Below are pictures while it is printing. It definitely bands left to Right perfectly. The very front and back points seem perfectly smooth all the way up with the sides showing the banding. Let me know if there are any files or other pictures you would like for me to take. Thanks in advance for everyone's help.




  • administrators

    Does the direction (clockwise/anticlockwise) of printing the perimeters change in sync with the banding?

    If you reduce the print speed (you can do this on-the-fly), does the banding reduce?



  • I will try printing again and slow the speed down as it is printing. It doesn't seem to be related to the direction of the printing as the printer is set to print in the same direction the entire time.


  • administrators

    @BPisLife:

    I will try printing again and slow the speed down as it is printing. It doesn't seem to be related to the direction of the printing as the printer is set to print in the same direction the entire time.

    The slicer may be reversing the print direction now and then. I suggest you watch which way it prints next time.



  • Ok, I just re-ran the print at a slower speed….hence why the results took so long.

    First I can absolutely confirm that the printer does not change directions. What I can say however is that reducing the speed 50% reduces the frequency of the banding by 50%. It appears to be a time based wobble which leads me to two possibilities. 1) Normal power supply fan turn on/turn off. I need to measuring that,

    or

    1. most likely the bed heating up and and cooling down is warping the bed/glass slightly and angling the print, which is why it is more apparent at top versus the bottom. It would make sense since slowing the print down 50% means that the bed warping would change reduce the z-height of the banding since it takes more time to increase the print height.

    Is there a way to change the hysteresis for turning on and off the heated build plate?

    My bed currently is a heater connected to the aluminum heat plate which is then adhesively attached to a borosilic glass plate (anycubic ultrabase attached to anycubics standard aluminum heater plate). Is there a better setup you would recommend for this?


  • administrators

    have a look here:

    https://duet3d.dozuki.com/Wiki/Gcode#Section_M307_Set_or_report_heating_process_parameters

    you can change your bed heating cooling PID etc to it holds a steady temperature. If its slow enough of a cycle to see the banding over multiple layers then you should see that in the bed temperature graph as well unless your bed thermistor is poorly thermally coupled to the bed?



  • Not sure yet, but it seems odd that changing the printing speed would directly change the frequency of the banding. I changed the speed to 150% and the banding changed accordingly. What gave me the idea is that in a few other forums people have complained about banding it it seemed correlated to their bed.

    The bed is standard from anycubic and has a PCB heater connected to a 3mm thick piece of aluminum and their ultrabase is another 3.5mm piece of glass with a special coating. The thermistor is on the opposite side of the pcb heater from the aluminum and is held against it by a piece of insulator. The temp. graph looks stable but I can't figure out how to adjust the scale or dump the temp data to graph it and see. Would be interesting to see the duration the heat is on versus off and see if it matches with the banding.

    I changed the bed to PID from bang-bang and I will see if that makes a difference at all.


  • administrators

    I assumed you were already using PID to control the bed, because if you ran heater tuning on it then PID would become the default. Using bang-bang to control the bed often causes Z banding. In your case I suspect that bed tilts a little with heat due to uneven heating or uneven support.



  • OK, it appears that the bed sits on plastic supports on the 2020 extrusions. I still get the banding with PID. I need to print some other stuff out and will get back to debugging this issue soon. The banding doesn't start for about 3-4" or at least isn't noticeable. One thing I read on some forums is the power supply fan can cause issues, but at this point I am done guessing. I will try printing without the heater on at all, and another with the temp increased 20 degrees to see if there is a difference.



  • So I figured I would continue to update this thread in case someone else runs into this sort of thing in the future. I started digging into this again and still not finding any solutions I changed the test print to be a simple 20mm cylinder that was 180mm tall. What I noticed is the the start/stop point which is supposed to be at the same point everytime (and same direction) is shifted each layer. As I begun searching for the layer shifting issue in a delta I found an older post in which someone references a better belt tension. In any event I have new carriages (and new linear rails...just to rule them out) in which the carriage is made out of metal (instead of the current plastic) and have a screw based belt tensioner, versus just a spring. I will see if that helps.

    [http://forums.reprap.org/read.php?178,763936](link url)


  • administrators

    Maybe try a different slicer that you can set the layer start point to be the same point on the cylinder and see if that has an effect on how the banding looks.



  • @t3p3tony sorry if I wasn't clear. I meant that it is set in Simplify3D to the same point and I can see it shifting in and out along with the banding. The bottom picture shows this if you look careful in the middle. Now based on the link I tried tightening the belt as best as I could based on the current carriage. The picture on the left is part of the cylinder prior to doing this and the right is after I tightened them. Definitely look better but still very apparent.

    Note the left one is cut in half so I could see if the infill had the same pattern and it does. It is definitely a layer shifting issue.

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