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    Speed affects extrusion rate with pellet extruder

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    • jay_s_ukundefined
      jay_s_uk @p8blr
      last edited by

      @p8blr you probably want to look at non linear extrusion and calibrate that

      Owns various duet boards and is the main wiki maintainer for the Teamgloomy LPC/STM32 port of RRF. Assume I'm running whatever the latest beta/stable build is

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      • droftartsundefined
        droftarts administrators @p8blr
        last edited by

        @p8blr See https://docs.duet3d.com/User_manual/Reference/Gcodes#m592-configure-nonlinear-extrusion

        Ian

        Bed-slinger - Mini5+ WiFi/1LC | RRP Fisher v1 - D2 WiFi | Polargraph - D2 WiFi | TronXY X5S - 6HC/Roto | CNC router - 6HC | Tractus3D T1250 - D2 Eth

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        • p8blrundefined
          p8blr @droftarts
          last edited by

          @droftarts Can you explain or link me to an explanation of this equation: (1 + min(L, Av + Bv^2)) ?

          I read through the forum posts linked in the M592 description but I still don't understand the theory behind that equation, let alone how to determine the A and B coefficents.

          Thanks.

          dc42undefined 1 Reply Last reply Reply Quote 0
          • dc42undefined
            dc42 administrators @p8blr
            last edited by dc42

            @p8blr the A and B coefficients are those of a parabola that best fits the extrusion multiplier vs. speed curve. I suggest you establish the required extrusion multiplier at lower speeds so that you can determine a base extrusion multiplier at low speeds.

            Alternatively you could command the extruder to extrude a fixed amount of plastic at various speeds, then weigh the amount extruded at each speed to determine how the amount of extrusion decreases with speed and hence what multiplier is needed.

            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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            • p8blrundefined
              p8blr @dc42
              last edited by p8blr

              @dc42 I collected some data, but I'm not sure how to make an equation that fits the format. I can't set an intercept of 1. Was my mistake that I calibrated at my maximum speed?

              2024-12-10 10_19_32-Cerberus Settings Calculator.xlsx - Excel.png

              I'm racking my brain trying to figure out how to make an equation that doesn't have a constant and I can't figure it out.

              Marlin supports a constant:
              155856e3-1e84-4fba-81c7-6cb914fdb887-image.png

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              • dc42undefined
                dc42 administrators @p8blr
                last edited by

                @p8blr if you think you need a constant then your extruder steps/mm is set incorrectly. It should be set so that you need an extrusion factor of 1 at low speeds.

                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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                • p8blrundefined
                  p8blr @dc42
                  last edited by p8blr

                  @dc42 the steps/mm are correct. I have them set to the values specified by the extruder manufacturer.

                  Does this make more sense?

                  936adc27-404a-4ae7-9dac-35375626de53-image.png
                  Book1.xlsx

                  • Print same part multiple times, only varying the print speed. (Two perimeter thick print, no infill)
                  • Measured the wall thickness several times, average them.
                  • Omit the 500mm/min speed because it is an outlier (may be a limitation of the pellet extruder)
                  • Theoretical bead width is 3.6mm, I take the nominal value (2*3.6mm) and divide it by the actual widths. This gives me an extrusion multiplier - I refer to it as the "corrective multiplier".
                  • Because I'm not using filament, my slicer has an arbitrary "filament diameter", I use the extrusion multiplier to recalculate a new filament diameter (Surface area * coefficient = surface area, solve for Diameter)
                  • I now create a new extrusion multiplier, based on the new extrusion multiplier at 1000mm/min being 1. This is calculated by taking the new nominal width, divided by the actual widths.
                  • I plot the extrusion multiplier vs the extrusion speed in mm/s (as specified in the M592 documentation) and apply a 2nd order polynomial trendline.

                  I end up with these coefficients:
                  M592 D2 A0.0047 B-0.00001 L1.29478

                  What is strange is that when I apply these, sometimes my extruder doesn't extrude at all.

                  Please let me know what you think. Thank you.

                  oliofundefined dc42undefined 2 Replies Last reply Reply Quote 0
                  • oliofundefined
                    oliof @p8blr
                    last edited by

                    @p8blr just a note that for whatever reason the Marlin implementation opted to swap the A and B parameter meaning. Maybe looking at Marlin docs caused a mix up?

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

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                    • dc42undefined
                      dc42 administrators @p8blr
                      last edited by

                      @p8blr looks like your factor vs speed plot is linear, so you can omit the B parameter entirely. Change the extruder steps/mm so that plot crosses extrusion factor 1 at speed 0.

                      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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                      • p8blrundefined
                        p8blr @dc42
                        last edited by

                        This post is deleted!
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                        • p8blrundefined
                          p8blr @dc42
                          last edited by

                          @dc42 How exactly do I modify the esteps/mm so that the plot crosses extrusion factor 1 at speed 0? I'm getting better results using a linear trendline, however, the issue I keep running into is this:

                          If I calibrate my esteps/mm at the slowest speed I use (1000mm/min for instance), then print some test prints at faster speeds, measure the widths, plot the results, my extrusion multiplier will always be off on the speed I calibrated at, i.e. if A = 0.0036, and I calibrated my multiplier to be 1 at 1000mm/min then my multiplier is now 1.0036 now at 1000mm/min.

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                          • dc42undefined
                            dc42 administrators @p8blr
                            last edited by dc42

                            @p8blr in that example you would divide your E steps/mm by 1.0036.

                            The best fit line in the graph in your earlier post showed an intercept of 0.9194 so if using that to provide the parameters you would multiply the steps/mm by 0.9194.

                            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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