Pressure advance issues



  • Printer is a cross between dc42 "Big Delta" design and T3P3 XL Delta. Duet Wifi.
    24V 0.9 deg stepper motors; all metal construction.
    Bowden tube is 53cm ; Extruder motor is 1.8 deg from my old Ormerod 2.



  • @Merlin:

    Printer is a cross between dc42 "Big Delta" design and T3P3 XL Delta. Duet Wifi.
    24V 0.9 deg stepper motors; all metal construction.
    Bowden tube is 53cm ; Extruder motor is 1.8 deg from my old Ormerod 2.

    I have a similar machine. How much pressure advance and retraction are you using? Thanks!



  • M572 D0 S0.1
    5mm retraction defined in MatterHacker, not using firmware retraction as MH slicing software does not support it.

    [Worth looking at latest version of Matter Hacker - its an interface and a slicer, with great 3D graphics a bit like Simplify3D; it's a free download and has a neat recovery feature, except this feature only works when driving printer from MH via usb]



  • Further to my earlier posts on this subject:
    I see that Matter Hackers slicer does support firmware retraction but cannot hack complex multi colour slicing - very slow, plus limit of 300,000 polygons!
    So I have now gone back to S3D - the latest version makes mincemeat of multi colour slicing and is extremely fast.
    Well worth the money as far as I am concerned (but not telling 'her indoors').



  • I tried 0.1 and 0.15 pressure advance on my delta (600+ mm bowden tube), but I can't see any difference in print quality compared to before. The only difference I notice is that my extruder makes odd sounds while printing the skirt.



  • Does Pressure Advance slow down your printspeed considerably? It's the only variable I've changed, and I seem to have lost the ability to actually control the speed…a 20min test cube turns into a 1.5hr test cube, and adjsuting the speed factor seems to do nothing..

    Thoughts?



  • SCRATCH THAT, I was implementing it in the config.g, works in the starting gcode just fine 😄



  • I found that I needed to increase the acceleration and jerk values when I started to use pressure advance, otherwise the printing speed was reduced.


  • administrators

    @StephenRC:

    I found that I needed to increase the acceleration and jerk values when I started to use pressure advance, otherwise the printing speed was reduced.

    The extruder jerk value is the critical one. The extruder acceleration during printing moves is limited to the lower of the value you specified in M201, and the jerk converted to mm/sec and divided by the amount of pressure advance.



  • @dc42:

    @StephenRC:

    I found that I needed to increase the acceleration and jerk values when I started to use pressure advance, otherwise the printing speed was reduced.

    The extruder jerk value is the critical one. The extruder acceleration during printing moves is limited to the lower of the value you specified in M201, and the jerk converted to mm/sec and divided by the amount of pressure advance.

    M201 X1000 Y1000 Z15 E1000 ; Accelerations (mm/s^2)
    M203 X15000 Y15000 Z300 E3600 ; Maximum speeds (mm/min)
    M566 X600 Y600 Z30 E200 ; Maximum jerk speeds mm/minute

    Okay, so… If M201 is E1000 and M566 is E200 (mm/m) I'd be limited at the 1000mm/s on acceleration?

    If i take 200 / 60 and divide that by .1(pressure advance) I get 33.3mm/s

    Am i doing that right? Should I adjust any of that? o.O;


  • administrators

    That's all correct. You don't need very high extruder acceleration for printing moves (and pressure advance doesn't affect the acceleration for retract and un-retract moves); however 200mm/min extruder jerk is unusually low, so the associated acceleration limit for printing moves that it causes might have an effect.



  • @dc42:

    That's all correct. You don't need very high extruder acceleration for printing moves (and pressure advance doesn't affect the acceleration for retract and un-retract moves); however 200mm/min extruder jerk is unusually low, so the associated acceleration limit for printing moves that it causes might have an effect.

    Okay! Glad to hear! I believe I even upped that from where it was before… wondering if this might be the cause of my issues haha

    What E-Jerk settings would you recommend? Using a e3d Titan with pancake stepper..

    Thanks,
    -Casey



  • I'm experimenting with some pressure issues here too. Stumbled on this thread, with adding M572 D0 S0.2 (I have an unusually long bowden tube) things seem much better- still tinkering. What are we actually changing with pressure advance?


  • administrators



  • Thanks DC42. Perfect explanation.



  • @dc42:

    That's all correct. You don't need very high extruder acceleration for printing moves (and pressure advance doesn't affect the acceleration for retract and un-retract moves); however 200mm/min extruder jerk is unusually low, so the associated acceleration limit for printing moves that it causes might have an effect.

    Sorry to dig up an old thread but I am just now configuring my own pressure advance. What would you recommend for extruder jerk with a 3:1 gear bowden extruder and a ~60cm long bowden tube?



  • I am also tuning the Pressure Advance. I have found a a K-factor calibration guide for Marlin at http://marlinfw.org/docs/features/lin_advance.html and a G-Code pattern generator in http://marlinfw.org/tools/lin_advance/k-factor.html.

    Will this approach work for Duet?.



  • Well replacing the instructuon fir Marlin

    [[language]]
    M900 K0.x ; set K-factor
    
    ```by
    

    [[language]]
    M572 D0 S0.x


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