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Pressure Advance: Discussion for Future Development

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  • undefined
    Slzer @RyanP
    last edited by 2 Aug 2020, 17:05

    @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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      Exerqtor
      last edited by 4 Aug 2020, 00:45

      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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        CCS86
        last edited by 30 Aug 2020, 02:59

        @dc42, any thoughts on this?

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          CCS86
          last edited by 28 Dec 2020, 15:34

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

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            CCS86
            last edited by 14 Feb 2021, 20:22

            @dc42

            😟

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              dc42 administrators
              last edited by 15 Feb 2021, 08:25

              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

              undefined 1 Reply Last reply 17 Feb 2021, 18:08 Reply Quote 4
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                Hergonoway
                last edited by Hergonoway 15 Feb 2021, 11:24

                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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                  dc42 administrators
                  last edited by 15 Feb 2021, 11:27

                  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
                  • undefined
                    pkos
                    last edited by 15 Feb 2021, 11:34

                    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

                    undefined 1 Reply Last reply 15 Feb 2021, 11:56 Reply Quote 0
                    • undefined
                      dc42 administrators @pkos
                      last edited by 15 Feb 2021, 11:56

                      @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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                      • undefined
                        pkos
                        last edited by 15 Feb 2021, 11:57

                        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

                        undefined 1 Reply Last reply 16 Feb 2021, 04:44 Reply Quote 0
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                          zapta @pkos
                          last edited by 16 Feb 2021, 04:44

                          I run a small experiment, printing calicat at 50mm/s with different PA values while watching the retraction graph on the stepper analyzer.

                          (my printer uses esteps=830 with 1/16 microsteps, such that 10 full steps on the vertical axis represent (10 * 16) / 830 = 0.193mm).

                          With PA = 0 it looks very very clean with normal 0.2mm retractions as set in my slicer (using BMG direct):

                          20210215-202653.png

                          Increasing the PA to 0.08 (my normal, BMG, direct) introduced small intermediate retractions, I presume because of the PA:
                          20210215-201346.png

                          Increasing to PA=0.2 made it really loud and wilde:
                          20210215-201318.png

                          With very rapid shot direction changes such as these ones:
                          20210215-201242.png

                          undefined undefined 2 Replies Last reply 16 Feb 2021, 09:10 Reply Quote 1
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                            DanS79
                            last edited by 16 Feb 2021, 07:37

                            I generally make parts where the seam ends up on a radiused corner. And something i've noticed is that the seam will look really good for one sized radius and bad for another of a substantially larger or smaller radius.

                            I assume this is because the PA value was tuned for angular acceleration similar to that encountered while traversing the corner radius.

                            Can anything be done to take X & Y acceleration and jerk into account?

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                              Martin1454 @zapta
                              last edited by 16 Feb 2021, 09:10

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

                              20210215-201242.png

                              NANANANA BATMAN!

                              1 Reply Last reply Reply Quote 2
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                                CCS86 @dc42
                                last edited by 17 Feb 2021, 18:08

                                @dc42 said in Pressure Advance: Discussion for Future Development:

                                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.

                                Thanks for the reply. It's good to know that it is on the radar.

                                I'm wondering if one of my suggestions: not allowing PA to change the print head acceleration, might be developmentally cheap enough to try in a beta release?

                                I still believe that when PA reduces print head acceleration, it could be adding to the issue of mismatched extrusion rate.

                                1 Reply Last reply Reply Quote 1
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                                  CCS86 @zapta
                                  last edited by 17 Feb 2021, 19:13

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

                                  I run a small experiment, printing calicat at 50mm/s with different PA values while watching the retraction graph on the stepper analyzer.

                                  Is this the stepper analyzer you are using? https://forum.duet3d.com/topic/21312/low-cost-public-domain-stepper-analyzer-season-2

                                  I'm curious if I could at least get a detailed step output from the Duet Maestro to track the extruder dur PA moves.

                                  undefined 1 Reply Last reply 19 Feb 2021, 05:46 Reply Quote 0
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                                    CCS86
                                    last edited by 18 Feb 2021, 23:57

                                    I did a test cube, running PA only on perimeters, to see if in the simplest case I could improve sharp corner geometry and/or the seam.

                                    Print parameters:

                                    • 0.4mm nozzle
                                    • 0.15mm layers
                                    • 50mm/s perimeters
                                    • PA varied by layer from 0.0 to 1.5
                                    • Max Accel (mm/sec^2): X: 4000.0, Y: 4000.0, Z: 400.0, E: 10000.0
                                    • Max jerk (mm/sec): X: 16.0, Y: 16.0, Z: 4.0, E: 5.0
                                    • Print accel (perimeters): 1200 mm/s^2

                                    In these photos, hopefully you can see what I can in person. Everything looks best with PA nearest zero. There is a corner bulge, but it is crisp and only affects the area very near the corner. Once PA values rise, the geometry deviation grows away from the corner (especially in the decel region), without actually reducing the corner bulge. The 22mm cube measures 22.10mm near the bottom (low PA), and measures 22.26mm at higher PA values.

                                    IMG_8885.jpg

                                    IMG_8883.jpg

                                    IMG_8882.jpg

                                    I'm a little baffled at how PA seems to provide no benefit in this test. But, IMO, the corner deviation growing away from the corner has to do with the print head accel being reduced at higher PA values, and lends some credibility to my suggestion of allowing an option to run the print head "untethered" by PA.

                                    Thoughts?

                                    undefined 1 Reply Last reply 19 Feb 2021, 02:43 Reply Quote 0
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                                      DanS79 @CCS86
                                      last edited by DanS79 19 Feb 2021, 02:43

                                      @CCS86 said in Pressure Advance: Discussion for Future Development:

                                      I'm a little baffled at how PA seems to provide no benefit in this test. But, IMO, the corner deviation growing away from the corner has to do with the print head accel being reduced at higher PA values, and lends some credibility to my suggestion of allowing an option to run the print head "untethered" by PA.

                                      Thoughts?

                                      Generally you want to do pa tests with only 1 or 2 perimeters and no infill. Also you want the seem in the middle of a side if your slicer will allow that. If you slicer won't allow for it, print a cylinder of a large enough diameter that the print head hits the requested print speed.

                                      Imo, based on the last picture you have some serious ringing you need to address before you worry about PA.

                                      for reference this is what i have on my railcore running a direct drive E3d V6.

                                      M201 X4500 Y4500 Z250 E1500       ; Accelerations (mm/s^2)
                                      M203 X24000 Y24000 Z1500 E3600    ; Maximum speeds (mm/min)
                                      M566 X1500 Y1500 Z120 E1500       ; Maximum jerk speeds mm/minute
                                      

                                      Important settings from my various ideamaker pla profiles. 0.4mm nozzle, 0.4mm extrusion width, 0.2mm layer height

                                      Vel	Accel	Jerk	PA	flowrate Temperature
                                      50	600	1500	0.11	86.2	 200
                                      50	480	1200	0.125	86.2	 200
                                      50	360	900	0.14	86.2	 200
                                      50	240	600	0.155	86.2	 200
                                      50	120	300	0.17	86.2	 200
                                      					
                                      100	3600	1500	0.08	85.8	 205
                                      100	2880	1200	0.08	85.8	 205
                                      100	2160	900	0.08	85.8	 205
                                      100	1440	600	0.08	85.8	 205
                                      100	720	300	0.08	85.8	 205
                                      					
                                      150	4500	1500	0.08	86.0	 220
                                      150	3600	1200	0.08	86.0	 220
                                      150	2700	900	0.08	86.0	 220
                                      150	1800	600	0.08	86.0	 220
                                      150	900	300	0.08	86.0	 220
                                      
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                                      • undefined
                                        CCS86
                                        last edited by CCS86 19 Feb 2021, 03:14

                                        The ringing is a separate thing altogether. I had bumped my XY jerk up a good bit for this PA test to mitigate some of the need for PA. The photos exaggerate the ringing a bit too.

                                        How are your flow rates the same for velocities ranging from 50 - 150 mm/s, with fixed layer height and extrusion width?

                                        undefined 1 Reply Last reply 19 Feb 2021, 03:18 Reply Quote 0
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                                          DanS79 @CCS86
                                          last edited by 19 Feb 2021, 03:18

                                          @CCS86 said in Pressure Advance: Discussion for Future Development:

                                          How are your flow rates the same for velocities ranging from 50 - 150 mm/s, with fixed layer height and extrusion width?

                                          See the temperature column.

                                          undefined 1 Reply Last reply 19 Feb 2021, 03:50 Reply Quote 0
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