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    RRF 2.03 pressure advance causes 20% overextrusion

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    • dc42undefined
      dc42 administrators @jschall
      last edited by dc42

      @jschall said in RRF 2.03 pressure advance causes 20% overextrusion:

      Just a thought, for a next generation path following algorithm, what I would do is:

      1. Segment the toolpath into linestrings in which the angles between the lines are less than some threshold (such as 30 degrees)
      2. Smooth those segments, using maybe a series of cubic splines (long lines may need to be split up into shorter lines first).
      3. Compute the speed curve along the segment such that tangential and radial acceleration is limited and such that the extruder can keep up with pressure advance. Each segment starts at zero speed and pressure and ends at zero speed and pressure.

      "Jerk" (bad choice of term) becomes unnecessary. Corners below the angle threshold are rounded smoothly, without ringing or asymmetry. The printer will come to a brief stop at sharp corners above the angle threshold, thus making them as sharp as possible.

      That's similar to what I have planned. A disadvantage is that the existing effect whereby the perimeters of holes are always under-sized would be made a little worse.

      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

      jschallundefined 1 Reply Last reply Reply Quote 0
      • T3P3Tonyundefined
        T3P3Tony administrators @jschall
        last edited by

        @jschall said in RRF 2.03 pressure advance causes 20% overextrusion:

        The printer will come to a brief stop at sharp corners above the angle threshold, thus making them as sharp as possible

        it will be interesting to see if PA can compensate for the large blob seen when stopping briefly at corners. Currently sharp corners are slightly rounded because the printer does not come to a complete stop - but they are smooth, where as when the print hed has to be raised (e.g. to the next z level, there is a visible Z "seam".

        Maybe this is better off combined with jerk for angles > than the smoothing process works on.

        www.duet3d.com

        jschallundefined 1 Reply Last reply Reply Quote 0
        • jschallundefined
          jschall @dc42
          last edited by

          @dc42 said in RRF 2.03 pressure advance causes 20% overextrusion:

          That's similar to what I have planned. A disadvantage is that the existing effect whereby the perimeters of holes are always under-sized would be made a little worse.

          Holes are undersized because of the low resolution meshes. I generally export my STLs with higher resolution.

          I did this real quick, based on wikipedia's python example of catmull-rom splines. The yellow line is the spline drawn through only the provided points, and the blue line is the spline when additional control points are added to limit the length of curved sections. It shouldn't cause holes to undersize - if anything it will make them better.

          Figure_1-1.png

          1 Reply Last reply Reply Quote 1
          • jschallundefined
            jschall @T3P3Tony
            last edited by

            @T3P3Tony said in RRF 2.03 pressure advance causes 20% overextrusion:

            Maybe this is better off combined with jerk for angles > than the smoothing process works on.

            Here's the thing though - just increase acceleration. That's effectively what jerk is doing anyway.

            mendenmhundefined 1 Reply Last reply Reply Quote 0
            • jschallundefined
              jschall
              last edited by

              Hard enough to get PrusaSlicer to generate gcode without 20% more extrusion than the volume of the STL in the first place 😄

              botundefined 1 Reply Last reply Reply Quote 0
              • mendenmhundefined
                mendenmh @jschall
                last edited by

                @jschall You have to be careful with just increasing the acceleration. Because of decreasing torque with increasing speed, high acceleration combined with high speed can cause lost steps. You can tolerate much more acceleration at low speed (where jerk comes into play) than at high speed.

                I have a low-accel setting for my printer (1200 mm/s^2) that allows travel up to 150 mm/s. I had to make my high-accel (1800 mm/s^2) macro drop the travel speed to 120 mm/s to not lose steps.

                I actually would like, someday, in RRF a variable-acceleration mode which drops the acceleration as the speed approaches a specified target, to keep the system inside the torque-speed envelope. It isn't a difficult calculation, and might allow somewhat faster overall printing.

                jschallundefined 1 Reply Last reply Reply Quote 0
                • jschallundefined
                  jschall @mendenmh
                  last edited by

                  @mendenmh yes, could just model that and limit acceleration to stay within torque limits.

                  1 Reply Last reply Reply Quote 0
                  • jschallundefined
                    jschall
                    last edited by

                    Getting endless "connection reset by peer" upload failures when trying to upload gcode to RRF 3.1.1. Not sure if the issue is with my network or RRF 3.1.1.

                    1 Reply Last reply Reply Quote 0
                    • Phaedruxundefined
                      Phaedrux Moderator
                      last edited by

                      Is your DWC version also at 3.1.1?

                      Post the result of M122?

                      Z-Bot CoreXY Build | Thingiverse Profile

                      jschallundefined 1 Reply Last reply Reply Quote 0
                      • botundefined
                        bot @jschall
                        last edited by bot

                        @jschall said in RRF 2.03 pressure advance causes 20% overextrusion:

                        Hard enough to get PrusaSlicer to generate gcode without 20% more extrusion than the volume of the STL in the first place 😄

                        Ahem: https://github.com/n8bot/PrusaSlicer/tree/n8_precision_minus_infill_support

                        This fork of PS 2.3.0-alpha alleviates inconsistent extrusion rate, among a few other things. I think you'll like it. Build that n8_precision_minus_infill_support branch.

                        *not actually a robot

                        jschallundefined 2 Replies Last reply Reply Quote 0
                        • jschallundefined
                          jschall @Phaedrux
                          last edited by

                          @Phaedrux said in RRF 2.03 pressure advance causes 20% overextrusion:

                          Is your DWC version also at 3.1.1?

                          Post the result of M122?

                          https://gist.github.com/jschall/49fc6d654a912f81ac897d64064325a4

                          1 Reply Last reply Reply Quote 0
                          • Phaedruxundefined
                            Phaedrux Moderator
                            last edited by

                            Check the General > Settings tab in DWC to see what version it's at.

                            M122 looks ok.

                            Z-Bot CoreXY Build | Thingiverse Profile

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                            • jschallundefined
                              jschall
                              last edited by

                              @Phaedrux said in RRF 2.03 pressure advance causes 20% overextrusion:

                              Check the General > Settings tab in DWC to see what version it's at.

                              Duet Web Control 3.1.1

                              1 Reply Last reply Reply Quote 0
                              • jschallundefined
                                jschall @bot
                                last edited by

                                @bot I tried to build PrusaSlicer before and gave up because of ridiculously huge numbers of dependencies on cutting edge versions of everything.

                                Edgars Batnaundefined 1 Reply Last reply Reply Quote 0
                                • jschallundefined
                                  jschall @bot
                                  last edited by

                                  @bot do you think you could build the linux .appimage for that and send it to me?

                                  botundefined 1 Reply Last reply Reply Quote 0
                                  • botundefined
                                    bot @jschall
                                    last edited by bot

                                    @jschall I do not have access to a linux machine, and have never built an app image... I've only built this on windows.

                                    However, I found the SuperSlicer (fork of PS) build instructions fantastic.

                                    https://github.com/supermerill/SuperSlicer/blob/master/doc/How to build - Linux et al.md

                                    Give that a shot.

                                    *not actually a robot

                                    jschallundefined 1 Reply Last reply Reply Quote 0
                                    • jschallundefined
                                      jschall @bot
                                      last edited by

                                      @bot said in RRF 2.03 pressure advance causes 20% overextrusion:

                                      However, I found the SuperSlicer (fork of PS) build instructions fantastic.

                                      That's just identical to the PrusaSlicer build instructions.

                                      Hmm, even a windows build would be fine. Can run it under a VM.

                                      botundefined 1 Reply Last reply Reply Quote 0
                                      • botundefined
                                        bot @jschall
                                        last edited by

                                        @jschall here's the windows build I run day-to-day:

                                        https://github.com/n8bot/PrusaSlicer/releases/tag/v2.3.0-alpha0-n8pmis

                                        It's almost the latest PS master branch, but the latest changes they made to the master branch aren't useful so those aren't included yet. (waiting for the seam painter to actually work, not just paint meaninglessly)

                                        *not actually a robot

                                        jschallundefined 1 Reply Last reply Reply Quote 0
                                        • jschallundefined
                                          jschall @bot
                                          last edited by

                                          @bot What's the difference between that and the n8_precision_minus_infill_support branch?

                                          botundefined 1 Reply Last reply Reply Quote 0
                                          • botundefined
                                            bot @jschall
                                            last edited by bot

                                            That release is the n8_precision_minus_infill_support branch.

                                            I copied and pasted the description from a previous release hastily, so it might have said the wrong thing.

                                            The previous releases work fine, too, but this one enables better support placement (PS ignores some "thin" support regions which prevents some support from appearing) and also prevents the solid infill from "auto-adjusting" the width by ~1 micron, which was annoying in some cases but not important to "fix."

                                            There are other releases there, too.

                                            The two main things I think you'll like are the resolution change, and the decimal precision changes. Fixes extrusion rate problems.

                                            Edit: Also, you might need some .DLLs from MS Visual Studio redistributable. Let me know if/which ones you need I can send them too.

                                            *not actually a robot

                                            jschallundefined 1 Reply Last reply Reply Quote 0
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