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    Pressure Advance Calibration

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    Tuning and tweaking
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    • OBELIKSundefined
      OBELIKS
      last edited by

      These are all long printing moves, as the models usually have small ones.
      You can always check in gcode.ws

      P3Steel Toolson mk2 - Duet 2 WiFi --> RatRig V-Core with Duet WiFi 1.03
      Original Prusa i3 MK3S

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      • jens55undefined
        jens55
        last edited by

        Is pressure advance supposed to change with different extrusion thickness ? I was always under the impression it was relatively constant at least with the same filament.
        I had run calibration for PLA 0.8 mm nozzle and 0.2 mm layer thickness and got a number of 0.45.
        I subsequently printed out a model at 0.4 mm layer thickness and ran into some odd issues that looked a lot like pressure advance issues but dismissed that because I had just calibrated that.
        I ran another pressure advance calibration but this time with 0.4 mm layer thickness and got a figure closer to 0.2 for pressure advance.
        Does this mean that in order to run a long bowden tube (where pressure advance is most critical) I have to calibrate every combination of filament, nozzle size, layer thickness and possibly nozzle temperature ?
        If so then the case for a direct extruder setup got a lot stronger ....

        deckingmanundefined 1 Reply Last reply Reply Quote 0
        • deckingmanundefined
          deckingman @jens55
          last edited by

          @jens55 I must confess that although I've played around with various parameters in relation to pressure advance, layer height vs nozzle diameter isn't one of them. I'd say that it's eminently possible that using a layer height of 20% of the nozzle diameter could offer a restriction to the filament flow as it exits the nozzle (because the nozzle tip is closer to the part being printed). Which would of course affect the pressure in the hot end, making it higher than if the layer height was greater.

          That being the case, then I'd expect the same problem to manifest itself, regardless of whether the extruder is direct drive or Bowden (because the cause of the pressure increase is downstream of the extruder).

          Ian
          https://somei3deas.wordpress.com/
          https://www.youtube.com/@deckingman

          jens55undefined 1 Reply Last reply Reply Quote 0
          • jens55undefined
            jens55 @deckingman
            last edited by

            @deckingman said in Pressure Advance Calibration:

            That being the case, then I'd expect the same problem to manifest itself, regardless of whether the extruder is direct drive or Bowden (because the cause of the pressure increase is downstream of the extruder).

            All I have ever read about pressure advance seems to indicate that a direct extruder only uses minimum amounts ... or put into other words, just a smidgen to optimize things.
            Going from 0.45 to 0.2 in a bowden setup becomes the difference between a good print and a failed print. The print I have been dealing with recently ended up with holes in the outer wall layer (still testing this finding) at the point where a layer started.
            I would very much like to have confirmation if my understanding of this is correct before I contemplate a major printer configuration change !

            deckingmanundefined 1 Reply Last reply Reply Quote 0
            • deckingmanundefined
              deckingman @jens55
              last edited by

              @jens55 Common perception is that pressure build up happens mostly in the Bowden tube, due to the filament buckling and twisting, which is why direct extruders are less prone to it's effects. Nobody really knows for sure but it seems a reasonable hypothesis. I was just surmising that if you are seeing a big difference between layers heights, then it might be because the filament flow as it exits the nozzle is being restricted with small layer heights. In which case, the cause of the pressure might be something other than the filament buckling and twisting. So if that is the case, then a direct extruder may exhibit the same behaviour. It's just conjecture on my part.........

              Ian
              https://somei3deas.wordpress.com/
              https://www.youtube.com/@deckingman

              jens55undefined 1 Reply Last reply Reply Quote 0
              • jens55undefined
                jens55 @deckingman
                last edited by

                @deckingman , thanks for your input. I agree with your thinking.
                I am hoping that somebody with first hand experience might chime in as we are both guessing.

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                • Munce31undefined
                  Munce31
                  last edited by

                  Hi All

                  I've been using this python script to fine tune my pressure advance on my zesty nimble extruder. It has been a massive help in this process.

                  Just one suggestion - I don't know if it is possible - however, I would like to see what pressure advance setting it is currently at during the print. Preferably to be displayed like a pop, similar to how the Report PA macro works in https://forum.duet3d.com/topic/6181/tuning-macros-menus-accel-jerk-retraction-pressure-advance. Is it possible to add something to this python script to report current pressure advance? It would make fine tuning the pressure advance just a little easier by taking a chunk of the guess work out of it.

                  Thanks,
                  Vince

                  wilrikerundefined 1 Reply Last reply Reply Quote 0
                  • wilrikerundefined
                    wilriker @Munce31
                    last edited by wilriker

                    @Munce31 You could manually add M117 <current PA value> into the GCode file after every change of PA.

                    Manuel
                    Duet 3 6HC (v0.6) with RPi 4B on a custom Cartesian
                    with probably always latest firmware/DWC (incl. betas or self-compiled)
                    My Tool Collection

                    Munce31undefined 1 Reply Last reply Reply Quote 0
                    • Munce31undefined
                      Munce31 @wilriker
                      last edited by

                      @wilriker said in Pressure Advance Calibration:

                      @Munce31 You could manually add M117 <current PA value> into the GCode file after every change of PA.

                      Yeah I figured I could do that as well, but that potentially could be quite laborious. I was thinking more along the lines of something like M117 <current PA value> being added directly into the python script so that it can be automated.

                      OBELIKSundefined 1 Reply Last reply Reply Quote 0
                      • Phaedruxundefined
                        Phaedrux Moderator
                        last edited by

                        The Report PA Value macro just sends the command for pressure advance without any parameters so that the current value gets echoed back. Doing a find and replace in the gcode file shouldn't be too hard to add it.

                        Z-Bot CoreXY Build | Thingiverse Profile

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                        • OBELIKSundefined
                          OBELIKS @Munce31
                          last edited by

                          @Munce31 If you are using the script @jens55 posted, you can add

                          print("M117 %.3f" % pressure_advance)
                          

                          after

                          print("M572 D0 S%.3f" % pressure_advance)
                          

                          P3Steel Toolson mk2 - Duet 2 WiFi --> RatRig V-Core with Duet WiFi 1.03
                          Original Prusa i3 MK3S

                          Munce31undefined 1 Reply Last reply Reply Quote 1
                          • Munce31undefined
                            Munce31 @OBELIKS
                            last edited by

                            @OBELIKS said in Pressure Advance Calibration:

                            @Munce31 If you are using the script @jens55 posted, you can add

                            print("M117 %.3f" % pressure_advance)
                            

                            after

                            print("M572 D0 S%.3f" % pressure_advance)
                            

                            Hi @OBELIKS thanks for providing that. It'll make it easier to watch the test print and see what pressure advance it current is running at.

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                            • zzingundefined
                              zzing
                              last edited by

                              I was reading though some of this to take a look at my own values.

                              What is quite odd is that the point at which the fast areas and slow areas are equal in width is at 1.75 - which seems crazy high according to the documentation. I am using a bowden tube of capricorn of length ~600mm. It has a bondtech extruder and a smart effector/v6 combo on the output.

                              I was using the original script from the start.

                              The other relevant settings from config:

                              M92 X80.00 Y80.00 Z80.00 E830.00                  ; Set steps per mm
                              M566 X1200.00 Y1200.00 Z1200.00 E40.00             ; Set maximum instantaneous speed changes (mm/min)
                              M203 X18000.00 Y18000.00 Z18000.00 E5000.00        ; Set maximum speeds (mm/min)
                              M201 X3000.00 Y3000.00 Z3000.00 E120.00            ; Set accelerations (mm/s^2)
                              M906 X1000.00 Y1000.00 Z1000.00 E500.00 I30        ; Set motor currents (mA) and motor idle factor in per cent
                              

                              I also just figured out this:

                              M92 E820
                              M592 D0 A0.001246 B0.000406 T230
                              

                              Do these seem reasonable? The max instanteous speed sounds low compared to one post above.

                              This is an upgraded mini kossel.

                              wilrikerundefined 1 Reply Last reply Reply Quote 0
                              • wilrikerundefined
                                wilriker @zzing
                                last edited by

                                @zzing said in Pressure Advance Calibration:

                                M566 X1200.00 Y1200.00 Z1200.00 E40.00             ; Set maximum instantaneous speed changes (mm/min)
                                

                                Do these seem reasonable? The max instanteous speed sounds low compared to one post above.

                                These values really are rather odd. How did you find such a low max inst. speed value for E? I have mine at 1800 and think I am still rather on the low end. Also this 40 of yours will probably lower total print speed.

                                Manuel
                                Duet 3 6HC (v0.6) with RPi 4B on a custom Cartesian
                                with probably always latest firmware/DWC (incl. betas or self-compiled)
                                My Tool Collection

                                botundefined 1 Reply Last reply Reply Quote 1
                                • zzingundefined
                                  zzing
                                  last edited by

                                  I am not sure if I set that or it was configured from the tool to build a config. With all those other values I could probably use realistic values for a delta machine.

                                  I can retest then.

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                                  • botundefined
                                    bot @wilriker
                                    last edited by

                                    If a user has a very geared down extruder, low E jerk is required (if using pressure advance). IIRC, extruder jerk is only used when pressure advance is in effect. Otherwise, it has no effect on print time. E Accel has an effect on print time when set too low, with or without pressure advance.

                                    My extruder can't use correct amounts of pressure advance without a low E jerk value of ~90.

                                    *not actually a robot

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                                    • SnakeSPundefined
                                      SnakeSP
                                      last edited by

                                      I have very strange results when trying to calibrate PA.
                                      Here are the speed, acceleration and jerk settings:
                                      M203 X15000.00 Y15000.00 Z15000.00 E6000.00
                                      M201 X2000.00 Y2000.00 Z2000.00 E2000.00
                                      M566 X1200.00 Y1200.00 Z1200.00 E1200.00
                                      I'm using BMG cloned extruder (if matters) with bowden of 550 mm and ID 2 mm.
                                      Used python script to print patterns with the following settings:
                                      extrusion_width = 0.5 (nozzle is 0.4 actually, 0.5 is used in slicer as an extrusion width)
                                      layer_height = 0.2
                                      filament_diameter = 1.72 (measured with calipers)

                                      travel_speed = 150
                                      first_layer_speed = 15
                                      slow_speed = 5
                                      fast_speed = 70

                                      I tried PA settings from 0.1 to 1.0 at first and there were no signs of PA working. Further experiments showed that noticable result is there only in range 1.5 to 1.9. But this looks insane... Or this is normal?
                                      Also i noticed that the speed is limited to 63-65 mm/s (due to too low extruder settings possibly?).

                                      Phaedruxundefined 1 Reply Last reply Reply Quote 0
                                      • Phaedruxundefined
                                        Phaedrux Moderator @SnakeSP
                                        last edited by

                                        @SnakeSP Perhaps try this method of tuning pressure advance.

                                        https://duet3d.dozuki.com/Wiki/Pressure_advance#Section_Methods_of_finding_the_right_amount_of_pressure_advance

                                        Z-Bot CoreXY Build | Thingiverse Profile

                                        SnakeSPundefined 1 Reply Last reply Reply Quote 0
                                        • SnakeSPundefined
                                          SnakeSP @Phaedrux
                                          last edited by

                                          @Phaedrux
                                          I tried the first one, with the python script.
                                          Will try the second one, with the cube, but need to understand how to make Simplify3d to align seam at the center of the side, for now i can only align it to one of the corners.

                                          One more thing still bothers me: i have not yet found the proper settings for BMG extruder (speed, acceleration, jerk) there are very different number said to be best in every topic i've read and there is nothing about it on Bondtech site. Can you point me where can i find such info please?

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                                          • SnakeSPundefined
                                            SnakeSP
                                            last edited by

                                            No matter what i try to set with "Choose start point..." the beginning of the line is always in the corner. Same for Cura. Does anyone know how to align Z seam to the center of the cube's side?

                                            Phaedruxundefined 1 Reply Last reply Reply Quote 0
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