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    More strange pressure advance behaviour

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    • dc42undefined
      dc42 administrators
      last edited by

      When you say it's with a single extruder, do you really mean that, or do you have the other extruders set to a very low percentage in the mix? I think it may make a big difference.

      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

      deckingmanundefined 1 Reply Last reply Reply Quote 0
      • deckingmanundefined
        deckingman @dc42
        last edited by

        @dc42 said in More strange pressure advance behaviour:

        When you say it's with a single extruder, do you really mean that, or do you have the other extruders set to a very low percentage in the mix? I think it may make a big difference.

        Dam. My bad. I thought I had mixing ratios set to unity but I've just checked and somewhere along the line I'd uploaded a config with mixing ratios of 0.96:0.02:0.02. That's what I was using. When I get time, I'll test again with unity mixing ratio. Sorry....

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

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        • deckingmanundefined
          deckingman
          last edited by

          OK. Tested with mixing ratio of 1.00:0.00:0.00 and the result was the same as with a mixing ratio of 0.96:0.02:0.02. That is to say very jerky head movement and by observing the extruder, the appearance that pressure advance is being applied multiple times around the circle. It is observable (if you watch the extruder gear) at lower pressure advance values like 0.1 but much less severe that at higher values. That's with 16x extruder microstepping. I can toggle the fault on and off by changing the extruder micro-stepping "on the fly" from the gcode console. So entering this M350 E16:16:16:16:16 will cause the fault to happen, and entering this M350 E256:256:256:256:256 will cure the fault.

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

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          • deckingmanundefined
            deckingman
            last edited by

            Trying to understand why this problem isn't being more widely reported. It's probably a unique combination of various factors but in an attempt to eliminate one of them, I defined Tool 0 simple as M563 P0 D0 H1 and commented out all the lines to do with mixing etc. Printing the tapered cylinder with 16x micro-stepping for the extruder and 0.5 pressure advance exhibits the same bad behaviour as having the tool defined to use multiple extruders but with the mixing ratio set to 1.00:0.00:0.00, so it isn't that. Oh well.....

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

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

              @deckingman I guess that a value of 0.5 for pressure advance is even high for a long bowden setup as far as I can tell. So maybe that's the reason why it is rarely ever reported.

              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

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              • deckingmanundefined
                deckingman @wilriker
                last edited by

                @wilriker said in More strange pressure advance behaviour:

                @deckingman I guess that a value of 0.5 for pressure advance is even high for a long bowden setup as far as I can tell. So maybe that's the reason why it is rarely ever reported.

                The thing is, I can see the same behaviour with lower values although at 0.1 or less, most people probably wouldn't notice unless they looked really closely. 0.3 or more is quite alarming though so I'm sure there must be some other reason why I see this behaviour. There are a lot of other things that are a bit unique to my printer. Two A and two B motors, 5 colour Diamond hot end, 0.5mm nozzle, big build volume, the use of Slic3R which generates strange looking segments sizes for arcs, - the list goes on. It's strange why upping the extruder steps per mm to 256x from 16x cures the problem though.

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

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                • deckingmanundefined
                  deckingman
                  last edited by

                  Following on from this thread https://forum.duet3d.com/topic/6090/problem-printing-circles/26 I tried re-slicing the object with "detect thin walls" disabled and "resolution" set to 0.1. The problem persists with extruder micro-stepping set to 16x, so no change. The gcode file still shows large variations in segment size which may be acting as trigger for whatever is causing the issue?

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

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                  • OBELIKSundefined
                    OBELIKS
                    last edited by OBELIKS

                    Check this one also, at the end: https://forum.duet3d.com/topic/6078/core-xy-movement-issues/57
                    He swapped M92 and M350 in config.g

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

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                    • deckingmanundefined
                      deckingman @OBELIKS
                      last edited by deckingman

                      @obeliks said in More strange pressure advance behaviour:

                      Check this one also, at the end: https://forum.duet3d.com/topic/6078/core-xy-movement-issues/57
                      He swapped M92 and M350 in config.g

                      Thanks for trying but yes I've been trying to help that OP also so I'm well aware.

                      Edit. But just for the hell of it, I made those same changes (even thought it's not correct) and it didn't help my issue.

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

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                      • dc42undefined
                        dc42 administrators
                        last edited by dc42

                        Hi Ian, I tried printing your tapered cylinder on my delta last week and again today with various pressure and advance extruder microstepping values. Even at pressure advance set to 0.4 and extruder microstepping set to 1 the XY movement is still smooth, although I can feel and hear the extruder vibrating.

                        [EDIT: I only tried the spiral vase version.]
                        [EDIT 2: I also tried with a mixing extruder configured, mix ratio 1:0.02:0.02, microstepping as low as 1:1:16. XY movement still smooth.]

                        So the next step is for me to replicate your configuration on my bench setup and see if I can see any jerkiness in the movement of the XY motors. But I have a feeling that you are not running very recent firmware. So please can you upgrade to firmware 2.01beta2 if you are running an older version, and verify that the problem is still there and it goes away at higher microstepping. Stay with DWC 1.20 (the latest DWC beta doesn't work properly with CoreXY) and add M564 H0 to config.g if you don't have it in there already.

                        PS - did the jerkiness happen at all heights of the tapered cylinder, or only in certain regions?

                        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

                        deckingmanundefined 1 Reply Last reply Reply Quote 0
                        • deckingmanundefined
                          deckingman @dc42
                          last edited by

                          @dc42

                          Hi David. As per post dated 14th July, I am indeed still on 1.20.1RC2 so I'll update and report back.

                          I can't say if the jerkiness happens at all heights. It does for the skirt and the first few layers, after which I've always aborted the print (didn't seem any point in continuing).

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

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                          • deckingmanundefined
                            deckingman
                            last edited by

                            Well now, it seems to be fixed 🎉 🎊 📣 🔔 🎷 🎂

                            So I updated the firmware to 2.01beta2 and put extruder micro-stepping down to 16x and I cannot provoke the problem. Tried single tool, mixing tool, ratios from 0.96:0.020.02 to 0.34:0.33:0.33. Tried the tapered vases - both vase mode and 3 perimeter model. Tried the original test cylinders. These were sliced at mostly 90mm /sec and I changed the speed from 30% (30mm/sec) all the way up to 300% (theoretically 270 mm/sec but in reality limited by acceleration to somewhat less). Tried pressure advance from 0.1 to 0.5. Tried all combinations of those sometimes crazy settings and behaviour is fine and normal.

                            That is to say, no matter what I do, pressure advance gets applied once only at the end of each circle, instead of multiple times during the circle and there are no pauses or jerky behaviour of the head movement.

                            So something that changed in firmware between 1.20.1RC2 and 2.01beta has fixed it although I haven't seen anything in the release notes that would explain it. Maybe it was the change to RTOS??? Who knows? Who cares? I'm just happy it's fixed.

                            PS, the top layer surface finish on those test cylinders at some speed way in excess of 90mm/sec with highish pressure advance was as good as 30mm/sec - almost flawless.

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

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                            • dc42undefined
                              dc42 administrators
                              last edited by

                              Great! I'll cross that one off my list. I made some changes to the pressure advance calculations in release 1.21, so those may have fixed it.

                              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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