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    Pressure Advance for direct drive

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    Tuning and tweaking
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    • pcsentinelundefined
      pcsentinel
      last edited by

      Is it worth using Pressure Advance on Direct Drive systems, I have an E3D Titan, if so what setting would be best?

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      • dc42undefined
        dc42 administrators
        last edited by

        Try it and see. I expect it will help, but you will need a low value of pressure advance, maybe in the range 0.02 to 0.05.

        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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        • hairy_kiwiundefined
          hairy_kiwi
          last edited by

          Running a wade-derivative direct drive + RRF1.18beta2 and printing at around 50mm/s, I saw a noticeable improvement last week with pressure advance values in the range dc42's suggesting.

          I'm currently running M572 D0 S0.025 in each gcode start-code block - i.e. not in RRF config.g. I read a good reason for it, but forget. Anyone care to remind?

          The nice thing about tweaking pressure advance is M572 can be issued while printing, making it super easy to experiment - thank you dc42 🙂
          I started with the rather extreme value of S5.0 just to check pressure advance was visibly functional. That resulted in a crude chamfer (approx 2mm) being applied to external square corners, S0.05 resulted in very slight but noticeable rounded corners and right now I'm happy with S0.025.

          IIRC S0.05 actually made for 'nicer' external perimeter corners than S0.025, but also resulted in gaps beginning to appear between infill and perimeters/outlines - perhaps more perimeter/outline overlap might solve this (currently its 15%).

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          • roboduetundefined
            roboduet
            last edited by

            @hairy_kiwi - do you have photos of printed parts with and without M572?

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            • Jackalundefined
              Jackal
              last edited by

              What kind of model is good for testing pressure advance?

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              • deckingmanundefined
                deckingman
                last edited by

                @Jackal:

                What kind of model is good for testing pressure advance?

                I'd guess the effect would be more noticable with longer print (extrusion) moves between changes of direction.

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

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                • hairy_kiwiundefined
                  hairy_kiwi
                  last edited by

                  @roboduet:

                  @hairy_kiwi - do you have photos of printed parts with and without M572?

                  No, sorry. I'll post some when I get a moment.

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                  • hairy_kiwiundefined
                    hairy_kiwi
                    last edited by

                    @Jackal:

                    What kind of model is good for testing pressure advance?

                    A solid infill 20 - 30 mm square x 3 mm height block ought to be of sufficient size to visually assess all the nuances of changing pressure advance. You may even need less z-height than 3mm to reach a conclusion. I would also suggest using the half-split-successive-guesstimate-technique* to derive your preferred value, rather than changing the value in small increments; you should find it much easier to see any changes that way. Until last week I was using a single 50 x 50 x 1.8 mm block with 0.3mm layer height and solid infill while setting up my machine. I found it a useful size block for checking bed flatness, E-steps/mm, jerk and acceleration and did also use it for setting pressure advance, but its size is probably overkill if you only want to set pressure advance.

                    *There's bound to be a bona fide mathematical process name for what I'm describing, but I can't find it so I've mashed one together: the half-split-technique (from electrical fault-finding) with successive-approximation (from mathematics, for finding roots of equations). 'Approximation' is further replaced by 'guesstimate', because at the end of the day it's all a somewhat subjective process.

                    Good luck! Have fun 😉

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                    • pcsentinelundefined
                      pcsentinel
                      last edited by

                      Thanks both, I'll start experimenting.

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                      • dc42undefined
                        dc42 administrators
                        last edited by

                        @hairy_kiwi:

                        *There's bound to be a bona fide mathematical process name for what I'm describing, but I can't find it so I've mashed one together: the half-split-technique (from electrical fault-finding) with successive-approximation (from mathematics, for finding roots of equations). 'Approximation' is further replaced by 'guesstimate', because at the end of the day it's all a somewhat subjective process.

                        I think you mean binary search. I remember using this technique when i was a student, to determine the appropriate amount of chilli to use when cooking chilli con carne. It only took me 3 meals to get it right.

                        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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                        • Alexander Mundyundefined
                          Alexander Mundy
                          last edited by

                          @hairy_kiwi:

                          @Jackal:

                          What kind of model is good for testing pressure advance?

                          *There's bound to be a bona fide mathematical process name for what I'm describing, but I can't find it so I've mashed one together: the half-split-technique (from electrical fault-finding) with successive-approximation (from mathematics, for finding roots of equations). 'Approximation' is further replaced by 'guesstimate', because at the end of the day it's all a somewhat subjective process.
                          Good luck! Have fun 😉

                          Back when I was a bench tech we called it "divide and conquer".

                          Good job with the naming convention!
                          I looked it up in a class training book from the '70's that I still have ( I'm not a pack rat 😉 ) and it was called the "half-split rule" there.

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                          • pcsentinelundefined
                            pcsentinel
                            last edited by

                            further Q on this, what E Jerk value would be a good starting point, its currently set to 20. I run a 0.9 deg stepper on the titan extruder

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                            • hairy_kiwiundefined
                              hairy_kiwi
                              last edited by

                              @dc42:

                              I think you mean binary search. I remember using this technique when i was a student, to determine the appropriate amount of chilli to use when cooking chilli con carne. It only took me 3 meals to get it right.

                              😄 That's it dc42! Many thanks for enlightening 🙂

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