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    Issues with pressure advance since RRF 3.4

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    • hestiahuangundefined
      hestiahuang
      last edited by

      https://forum.duet3d.com/topic/33803/unable-to-stop-severe-bulging-in-corners-with-new-print-head/29

      The same issue in above link too.

      hestiahuangundefined 1 Reply Last reply Reply Quote 0
      • hestiahuangundefined
        hestiahuang @hestiahuang
        last edited by

        @hestiahuang

        Most likely it is obvious on CoreXY machine. When there is a corner, and moving before arrived the end of corner, both A motor and B motor, need to slow down, severe bulging will come before arriving the corner. If it is the machine like UM, it will be only severe bulging after corner but never before corner, as there is only one aixs motor for each aixs. However this is the inherent feature for CoreXY, due to it needs both A motor an B motor keep moving.

        This is the first time I am using CoreXY machine, the E3D ToolChanger.

        No clue how to fix it...

        What I guess, PA can't fix this, as it is XY movement related, not extrusion related. However the Input shaping is the direction. RRF Input shaping is still the blackbox, a long way need to go.

        hestiahuangundefined 1 Reply Last reply Reply Quote 0
        • hestiahuangundefined
          hestiahuang @hestiahuang
          last edited by

          @hestiahuang

          Adjust the belt tension can not fix the problem.

          hestiahuangundefined 1 Reply Last reply Reply Quote 0
          • hestiahuangundefined
            hestiahuang @hestiahuang
            last edited by

            @hestiahuang

            Someone shared me that, he has the same issue on RRF, however It comes to be fixed after he using the Klipper. Really no idea what's the diff.

            Notepadundefined 1 Reply Last reply Reply Quote 0
            • Notepadundefined
              Notepad @hestiahuang
              last edited by

              @hestiahuang

              This problem can be replicated on Hbot and other similar Cartesian designs. Its only more obvious because CoreXY tends to have higher speeds thus requiring higher flow rates. Overall, its almost entirely a flow control issue instead of a kinematic issue.

              Klipper has a feature called smoothing time which works with their pressure advance - My current belief is that this smoothing time is the key to fixing this issue. I am currently building a test machine that will use klipper for an apples to apples comparison between RRF and Klippers implementation. But ill be having to do it after SMRRF as time constraints are tight right now.

              The real bamboo printer manufacturer

              PCRundefined 1 Reply Last reply Reply Quote 1
              • PCRundefined
                PCR @Notepad
                last edited by

                @Notepad @jay_s_uk has a machien where he can switch from klipper to RRF

                oliofundefined 1 Reply Last reply Reply Quote 1
                • oliofundefined
                  oliof @PCR
                  last edited by

                  @PCR so do I (actually capable of triple play -- Marlin, RRF, and Klipper). I can't say I have these issues with bulging corners but I run quite high extruder jerk and acceleration (https://forum.duet3d.com/topic/33964/e-acceleration-has-to-be-limited-to-to-e-jerk-pa?_=1700602309451). I wonder what e jerk and acceleration the people heavily affected run; if jerk and accel aren't high enough I can see that PA may kick in "late" and not have (any) effect, especially at higher speeds.

                  <>RatRig V-Minion Fly Super5Pro RRF<> V-Core 3.1 IDEX k*****r <> RatRig V-Minion SKR 2 Marlin<>

                  hestiahuangundefined Notepadundefined 2 Replies Last reply Reply Quote 1
                  • hestiahuangundefined
                    hestiahuang @oliof
                    last edited by

                    @oliof said in Issues with pressure advance since RRF 3.4:

                    @PCR so do I (actually capable of triple play -- Marlin, RRF, and Klipper). I can't say I have these issues with bulging corners but I run quite high extruder jerk and acceleration (https://forum.duet3d.com/topic/33964/e-acceleration-has-to-be-limited-to-to-e-jerk-pa?_=1700602309451). I wonder what e jerk and acceleration the people heavily affected run; if jerk and accel aren't high enough I can see that PA may kick in "late" and not have (any) effect, especially at higher speeds.

                    So first of all we need to stop tuninig anything but testing the capability of the E motor.
                    Btw, any steps or details shown how to find out the value?

                    oliofundefined 1 Reply Last reply Reply Quote 0
                    • oliofundefined
                      oliof @hestiahuang
                      last edited by

                      @hestiahuang I simply increased extrusion speed into thin air until the extruder skipped, then backed off of that 20%, after that did firmware retrac/unretract with increased acceleration until the extruder screamed, and then backed that off 20%

                      There is a case to be made that you may need to redo this for PETG due to its difference in backpressure behavior, but I never bothered and it seems to work well enough.

                      In direct drive, my PA value is 0.02 to 0.03 and that seems to be good enough.

                      <>RatRig V-Minion Fly Super5Pro RRF<> V-Core 3.1 IDEX k*****r <> RatRig V-Minion SKR 2 Marlin<>

                      gloomyandyundefined 1 Reply Last reply Reply Quote 0
                      • gloomyandyundefined
                        gloomyandy @oliof
                        last edited by

                        @oliof What extruder jerk are you currently running? After reading your other thread I tried increasing mine to the 3000 range (previously it was 300), but with that setting I started getting various odd noises at sharp corners and seemed to be losing extrusion.

                        oliofundefined 1 Reply Last reply Reply Quote 0
                        • oliofundefined
                          oliof @gloomyandy
                          last edited by

                          @gloomyandy jerk in the 300 to 600 range, acceleration in the 3600 to 6000 range

                          <>RatRig V-Minion Fly Super5Pro RRF<> V-Core 3.1 IDEX k*****r <> RatRig V-Minion SKR 2 Marlin<>

                          gloomyandyundefined 1 Reply Last reply Reply Quote 1
                          • gloomyandyundefined
                            gloomyandy @oliof
                            last edited by

                            @oliof Thanks, what sort of jerk and acceleration are you running on X, Y, Z? I must say I do find the entire jerk/acceleration thing very confusing having spent some time yesterday searching the forums it seems that values anywhere from high jerk/lowish acceleration to low jerk/high acceleration seem to be in use! There also seems to be some (unresolved) confusion as to when jerk is actually applied with some comments indicating it is only used between moves while others say it is applied (in mode 1) as an initial speed for moves that start at zero.

                            oliofundefined 1 Reply Last reply Reply Quote 0
                            • oliofundefined
                              oliof @gloomyandy
                              last edited by oliof

                              @gloomyandy jerk is a bit of black magic, I spent a weekend with a friend trying to read and understand how its applied in RRF, but I forgot all about it since then.

                              my jerk/accel on the IDEX are

                              M566 X360.00 Y210.00 Z18 E300.00 P1                  ; Set maximum instantaneous speed changes (mm/min)
                              M201 X7500.00 Y4000.00 U7500.00 Z100.00 E6000.00     ; Set accelerations (mm/s^2)
                              

                              (this is an i3 style portal printer with a prusa bear like frame with a 220^3 print volume)

                              On the V-Minion my values are

                              M566 X900.00 Y900.00 Z60.00 E300.00                    ; set maximum instantaneous speed changes (mm/min)
                              M201 X3000.00 Y3000.00 Z200.00 E6000.00                ; set accelerations (mm/s^2)
                              

                              (this is an Ormerod style cartesian cantilever printer with a 180^3 print volume)

                              Just a note that the accelerations on the V-Minion are quite low compared to the klipper config for it, it is on record with 6 minute speed benchies, but I haven't pushed that far yet.

                              <>RatRig V-Minion Fly Super5Pro RRF<> V-Core 3.1 IDEX k*****r <> RatRig V-Minion SKR 2 Marlin<>

                              gloomyandyundefined 1 Reply Last reply Reply Quote 1
                              • gloomyandyundefined
                                gloomyandy @oliof
                                last edited by

                                @oliof Thanks! It's interesting that your two printers have such a big difference between them! I'm currently using something similar to your first example on my toolchanger with a jerk of 300 and acceleration of 15000, I do get a lot of ringing though so I'll probably be reducing the acceleration somewhat.

                                Don't want to disrupt this thread, but I wish there was a good way to determine good values for jerk and acceleration with RRF.

                                oliofundefined 2 Replies Last reply Reply Quote 1
                                • oliofundefined
                                  oliof @gloomyandy
                                  last edited by

                                  @gloomyandy the first printer isna glorified ender3 with a terrible y motion system that's dragging it down (also 6mm belts). The second is a very compact machine with 9mm belts designed for rigidity and speed.

                                  To be fair, I haven't even started really tuning the V Minion for fast printing simply for lack of time, or the differences would be even more striking.

                                  <>RatRig V-Minion Fly Super5Pro RRF<> V-Core 3.1 IDEX k*****r <> RatRig V-Minion SKR 2 Marlin<>

                                  gloomyandyundefined 1 Reply Last reply Reply Quote 1
                                  • gloomyandyundefined
                                    gloomyandy @oliof
                                    last edited by

                                    @oliof Can't resist taking this thread slightly more off topic! How did you select the Jerk speed for the V-Minion? Did you use any test prints to help? I seem to remember it has a big impact on how curves get printed...

                                    1 Reply Last reply Reply Quote 0
                                    • Notepadundefined
                                      Notepad @oliof
                                      last edited by Notepad

                                      @oliof
                                      I currently am running a jerk of 1000mm/min with accelerations of 4000 mm/s/s Using a Hemera XS with a volcano style hotend.

                                      I used to run by the theory of low jerk high acceleration (J of 500mm/min and 7000mm/s/s) but im now just trying everything in order to isolate the issue

                                      Edit: I should say I am only experiencing this issue on larger nozzles. On a 0.4mm nozzle the issue is imperceptible enough to not be an issue, but on a 0.6mm nozzle the issue is exceptionally bad.

                                      The real bamboo printer manufacturer

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

                                        I think everyone should learn to use one of these sealant gun.jpg

                                        You apply pressure at one end which forces a viscous fluid out of a restricted orifice. Just like a 3D printer extruder. You'll learn a lot about how the flow of a viscous fluid out of a small orifice reacts (or rather hardly reacts) to changes in pressure on the input and how difficult it is to get that flow rate to match the rate to change of movement of the nozzle through space.

                                        Personally, I get best results by keeping the filament flow rate as near constant as possible which essentially means low(ish) acceleration and high(ish) jerk and using pretty much the same speed for all move types.

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

                                        1 Reply Last reply Reply Quote 1
                                        • oliofundefined
                                          oliof @gloomyandy
                                          last edited by

                                          @gloomyandy re:jerk -- I increased it until I got skipping on the motion system, then backed off by 20%. It seems to be a good approach that gets me into a "usable, not too low" range.

                                          @deckingman I had issues with too low acceleration causing print head inertia to be a factor on corner performance. So I tend to aim for low-ish jerk and higher acceleration.

                                          <>RatRig V-Minion Fly Super5Pro RRF<> V-Core 3.1 IDEX k*****r <> RatRig V-Minion SKR 2 Marlin<>

                                          1 Reply Last reply Reply Quote 0
                                          • gloomyandyundefined
                                            gloomyandy
                                            last edited by

                                            @Notepad Are the jerk and acceleration figures you are quoting for the extruder, the movement axis or both?

                                            @deckingman A similar question really what are the actual jerk/acceleration figures you have settled on both for the various axis and the extruder?

                                            deckingmanundefined Notepadundefined 3 Replies Last reply Reply Quote 0
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