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    Pressure Advance: Discussion for Future Development

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    • CCS86undefined
      CCS86
      last edited by

      I can't remember with confidence which files I tried and failed to get a good result. The next time I have that issue, I will set the code aside.

      I decided to try to make a test print that I hoped would replicate my PA issues for demonstration. Just a short, narrow print, which necks down from an 8mm width, to 2mm width. This object is copied 4 times, printed one at a time, with M572 D0 S0, S0.5, S1.0, S1.5.

      I photographed the results with my macro lens, but it's really hard to make judgement from the photos. In hand, they all look similar. If anything the S0 print looks best. With PA enabled, you certainly lose a bunch of time.

      1327abdc-2297-402d-8a9b-5ca161255c0c-image.png

      cf9aaa5e-9bc5-4543-b943-6ef1d3ebd746-image.png

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      • QuintBrandundefined
        QuintBrand
        last edited by QuintBrand

        I relate to your ideas and findings. I have a nimble though, so bit different situation. A nimble has trouble to keep up wit PA due to its high gear ratio (as noted on duet website). So although direct drive it has some "bowden like" behavior in PA. My findings:

        • using Marlin routine I need S0.54
        • using the Python script approach I need S0.6
        • in real printing I find better results with S0.4

        So lower than in the tests with I think relate to your observation on for the under extrusion on very short lines.

        I have no need anymore for coasting in cura, and overall I have better quality. I hope and think you do too right? It's about improving it even more.

        So I think your idea on the minimum amount of time could work well. I'm wondering if it should be time or travel length though? That would take out the need to tune each time when you print with different speeds for different prints, or even when using different speeds while printing different features.

        I think having both options would be best to tinker with.

        Also I would think it would be even nicer if one can give two parameters:

        • length/time No PA
        • length/time Full PA.

        And an interpolation in between to give a sliding PA value?

        No idea how hard to implement, but I bet it would be a selling point when this works well (I'd be happy to test 🙂 when indeed working well.

        While think about it: anybody know how to modify a gcode file to search for short line length and putting an M572 in front (and after) to change the settings with some existing scripts or something to prototype test?

        Cheers Q

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        • QuintBrandundefined
          QuintBrand
          last edited by

          Seems little interest CCS... 🤔

          CCS86undefined 1 Reply Last reply Reply Quote 0
          • Slzerundefined
            Slzer
            last edited by

            I ended up just using 0.5 for my PA on my long bowden setup despite all tests indicating more or less no change until 1.5-2 range.

            I'm actually getting quite nice results but I was simply limited by what didn't cause the extruder to sound like a machine gun

            Exerqtorundefined 1 Reply Last reply Reply Quote 0
            • Exerqtorundefined
              Exerqtor @Slzer
              last edited by

              @Slzer

              That's exactly what i ended up doing to (well i setteled on 0.4), even though i would get the most consistent pressure somewhere close to 2, but it sounded like my BMG was one nudge away from exploding at that point 😂

              Designed new extruder mounts so i could move the extruders over the build area (corexy machine) and shorten the bowdens down to 300mm ish, so 0.4 isn't that much off.

              RyanPundefined 1 Reply Last reply Reply Quote 0
              • CCS86undefined
                CCS86 @QuintBrand
                last edited by

                @QuintBrand said in Pressure Advance: Discussion for Improvement in Bowden Printers:

                Seems little interest CCS... 🤔

                Were you waiting on my feedback? It sounded like you were generally agreeing with me and not asking questions.

                I don't think "length" is a better parameter to use for filtering over "time". We are dealing with time based phenomenon, ie lag between extruder drive motion > nozzle pressure > nozzle flow rate. How fast the print head is traveling doesn't impact these things.

                QuintBrandundefined 1 Reply Last reply Reply Quote 0
                • Edgars Batnaundefined
                  Edgars Batna
                  last edited by Edgars Batna

                  I have resorted to printing without PA now. In my case I observed that the extruder reverse motion gets skipped on consecutive small segments, thus all my over-extrusion issues ensued.

                  I also dug in the Firmware and at some point it just stopped being fun as there are multiple approximations related to step generation which smell bad. Having no handy HW simulation tools it just took too long to debug with all the variables.

                  I saw Klipper implements "smoothing" for PA, so I started moving to it to test it out. While there are pros and cons between Duet and Klipper (I still like the Duet), but at least in Klipper the CPU basically only runs the step pulses, so no need to deal with interrupts being late or whatnot.

                  Not finished yet, tho.

                  1 Reply Last reply Reply Quote 1
                  • QuintBrandundefined
                    QuintBrand @CCS86
                    last edited by

                    @CCS86

                    Hey, no I was not trying to push you in any way, but actually trying to support this tread from sliding away as I think it is an excellent idea to get the "gun" effect out of the printing with PA 👍.

                    I think bit time and length would be nice. I agree that if we'd "need to choose" time is probably better, but when printing at (quite) different speeds for infill, walls etc I think length is also nice.

                    I also went from 0.4-0.5 found from testing to 0.2 to ease the printing somewhat and get good results anyways too.

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                    • RyanPundefined
                      RyanP @Exerqtor
                      last edited by

                      @Exerqtor said in Pressure Advance: Discussion for Improvement in Bowden Printers:

                      @Slzer

                      That's exactly what i ended up doing to (well i setteled on 0.4), even though i would get the most consistent pressure somewhere close to 2, but it sounded like my BMG was one nudge away from exploding at that point 😂

                      Designed new extruder mounts so i could move the extruders over the build area (corexy machine) and shorten the bowdens down to 300mm ish, so 0.4 isn't that much off.

                      Answers like this make me not feel alone in the world.

                      CR10S, August 2018
                      Anycubic Photon S December 2019
                      Ender 5 Feb 2020
                      Ender 5 Plus May 2020
                      Anycubic Photon Mono X Nov 2020
                      ~
                      https://3dimensiongames.com/

                      Slzerundefined 1 Reply Last reply Reply Quote 0
                      • Slzerundefined
                        Slzer @RyanP
                        last edited by

                        @RyanP said in Pressure Advance: Discussion for Improvement in Bowden Printers:

                        @Exerqtor said in Pressure Advance: Discussion for Improvement in Bowden Printers:

                        @Slzer

                        That's exactly what i ended up doing to (well i setteled on 0.4), even though i would get the most consistent pressure somewhere close to 2, but it sounded like my BMG was one nudge away from exploding at that point 😂

                        Designed new extruder mounts so i could move the extruders over the build area (corexy machine) and shorten the bowdens down to 300mm ish, so 0.4 isn't that much off.

                        Answers like this make me not feel alone in the world.

                        Aye me too... Most calibration things I can see the difference and select a good balance (although often having to run multiple parameter ranges to get a matrix of options - stringing control being a good example here, move speed, retraction length, retraction rate wipe etc.) but this one feels like black magic hah

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                        • Exerqtorundefined
                          Exerqtor
                          last edited by

                          Just saw this tutorial pop up, note that it is for klipper-fw, but it should be translateable for RRF to i think. Gonna try it tomorrow and see what numbee i end up with this time 😅

                          https://www.lpomykal.cz/anycubic-kossel-klipper-pressure-advance/

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                          • CCS86undefined
                            CCS86
                            last edited by

                            @dc42, any thoughts on this?

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                            • CCS86undefined
                              CCS86
                              last edited by

                              @dc42 I was really hoping you would weigh in here!

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                              • CCS86undefined
                                CCS86
                                last edited by

                                @dc42

                                😟

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                                • dc42undefined
                                  dc42 administrators
                                  last edited by

                                  I'm sorry, I don't have time to look at improving PA until I've implemented input shaping. But I've bookmarked this thread so that I can return to it. Pressure advance smoothing is something I was already thinking about.

                                  Duet WiFi hardware designer and firmware engineer
                                  Please do not ask me for Duet support via PM or email, use the forum
                                  http://www.escher3d.com, https://miscsolutions.wordpress.com

                                  CCS86undefined 1 Reply Last reply Reply Quote 4
                                  • Hergonowayundefined
                                    Hergonoway
                                    last edited by Hergonoway

                                    while we're at it, is there any impact using DAA (Dynamic Acceleration Adjustment: M593 with F != 0) during PA calibration process? DAA is related to acceleration where PA is jerk related, technically one shouldn't alter the other result but... heavy doubt 👀

                                    or is it better to turnOFF DAA, calibrate PA, then calibrate/turnON DAA ?

                                    Delta goes BrrrRRRRrrrrrRRRRrrr

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                                    • dc42undefined
                                      dc42 administrators
                                      last edited by

                                      DAA might reduce acceleration, so it may affect PA - but only because in reality, PA should not be applied linearly. I think I would be inclined to calibrate DAA first followed by PA, however I haven't tested doing it both ways so I may be wrong.

                                      Duet WiFi hardware designer and firmware engineer
                                      Please do not ask me for Duet support via PM or email, use the forum
                                      http://www.escher3d.com, https://miscsolutions.wordpress.com

                                      1 Reply Last reply Reply Quote 1
                                      • pkosundefined
                                        pkos
                                        last edited by

                                        Forgive the reference, but that's the way Klipper does it. First you do input shaping and only then PA.

                                        Speaking of input shaping - since you are looking at it - are you also considering the option of using an accelerometer (like adxl345) to get the measurements? 🙂

                                        Voron 2.4 (Duet 3 6HC + 3HC standalone), Voron SW (Duet 3 mini 5+ standalone), Voron Trident (Duet 3 mini 5+ standalone), Voron 0.1

                                        dc42undefined 1 Reply Last reply Reply Quote 0
                                        • dc42undefined
                                          dc42 administrators @pkos
                                          last edited by

                                          @pkos said in Pressure Advance: Discussion for Future Development:

                                          Speaking of input shaping - since you are looking at it - are you also considering the option of using an accelerometer (like adxl345) to get the measurements?

                                          Yes.

                                          Duet WiFi hardware designer and firmware engineer
                                          Please do not ask me for Duet support via PM or email, use the forum
                                          http://www.escher3d.com, https://miscsolutions.wordpress.com

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                                          • pkosundefined
                                            pkos
                                            last edited by

                                            Awesome!

                                            Voron 2.4 (Duet 3 6HC + 3HC standalone), Voron SW (Duet 3 mini 5+ standalone), Voron Trident (Duet 3 mini 5+ standalone), Voron 0.1

                                            zaptaundefined 1 Reply Last reply Reply Quote 0
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