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Duet Maestro Struggling to Produce Smooth Curves

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  • undefined
    dc42 administrators @CCS86
    last edited by 2 Mar 2021, 13:41

    @CCS86 said in Duet Maestro Struggling to Produce Smooth Curves:

    If you read further down, you will see that I used arc welder to process the cylinder gcode, and still see the faceting. Any ideas on that?

    What perimeter printing speed did you use, and what is the diameter of the part? Knowing those, I can work out what segment size RRF will use for the G2/G3 moves.

    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

    undefined 1 Reply Last reply 2 Mar 2021, 14:21 Reply Quote 0
    • undefined
      CCS86 @dc42
      last edited by 2 Mar 2021, 14:21

      @dc42

      I posted a code snippet of a single wall:

      G0 F7650 X66.46 Y133.941
      ;TYPE:WALL-OUTER
      G3 X59.665 Y131.199 I-0.004 J-9.780 E18.81959 F2700
      G3 X56.678 Y124.500 I6.796 J-7.046 E18.89384
      G3 X59.175 Y117.612 I9.776 J-0.353 E18.96800
      G3 X65.774 Y114.385 I7.287 J6.541 E19.04236
      G3 X72.742 Y116.642 I0.691 J9.751 E19.11650
      G3 X76.195 Y123.114 I-6.281 J7.508 E19.19075
      G3 X74.174 Y130.180 I-9.725 J1.040 E19.26515
      G3 X67.884 Y133.837 I-7.718 J-6.036 E19.33876
      G0 F2430 X67.829 Y133.845
      

      I ran at 45mm/s and 60mm/s.

      1 Reply Last reply Reply Quote 0
      • undefined
        dc42 administrators
        last edited by 2 Mar 2021, 14:29

        Look like about 10mm radius then. The segment length used by RRF 3.2 is:

        length = min(sqrt(8 * radius * 0.02), speed/50)

        subject to a minimum of 0.1mm and a maximum of 2.0mm. Putting your figures in, at 60mm/sec we get:

        length = min(sqrt(1.6), 1.2)

        so the minimum segment length will be 1.2mm. Does this fit with what you observed?

        The Maestro has no hardware floating point unit, so there is limited scope to use smaller segments. However, the arc generation algorithm has been speeded up somewhat in the 3.3beta source code, so there may now be some scope.

        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

        undefined 1 Reply Last reply 2 Mar 2021, 14:39 Reply Quote 0
        • undefined
          CCS86 @dc42
          last edited by 2 Mar 2021, 14:39

          @dc42

          1mm does match up to the faceting I am seeing there.

          So RRF is taking the arc and decomposing them back into line segments to drive motion? Somewhat counter productive, if I can already output sub 1mm segments from the slicer. I was hoping that the arcs could help to avoid the segment junction issue, by making them tangent, but it appears to by making them worse in this case.

          ? 1 Reply Last reply 2 Mar 2021, 15:13 Reply Quote 0
          • ?
            A Former User @CCS86
            last edited by 2 Mar 2021, 15:13

            @CCS86

            As far as I recall as processors/boards get faster, in the future, the integrated line-segmentation will overtake one day by beeing faster and finer by dirctly controlling the motor (in the long run...)... If you ask me if the duet-community does not want the hardware to be considerably more expensive (I don´t want that) we have to wait until our price-segment cpu etc. get´s faster...

            I stay with pre-segmentation in the post-processor til that day 🙂 because a hot plastic-stripe is anyhow far from being perfect 😉

            Hope that is of any help 🙂 & great post - because thanks to you dc42 posted the formula 😉

            undefined 1 Reply Last reply 2 Mar 2021, 17:41 Reply Quote 0
            • undefined
              CCS86 @A Former User
              last edited by 2 Mar 2021, 17:41

              @LB said in Duet Maestro Struggling to Produce Smooth Curves:

              @CCS86

              As far as I recall as processors/boards get faster, in the future, the integrated line-segmentation will overtake one day by beeing faster and finer by dirctly controlling the motor (in the long run...)... If you ask me if the duet-community does not want the hardware to be considerably more expensive (I don´t want that) we have to wait until our price-segment cpu etc. get´s faster...

              I stay with pre-segmentation in the post-processor til that day 🙂 because a hot plastic-stripe is anyhow far from being perfect 😉

              Hope that is of any help 🙂 & great post - because thanks to you dc42 posted the formula 😉

              I don't think this is a hardware limitation. The Maestro can already chug through super dense code to approximate curves with smooth motion. It would be far less taxing on the hardware to use motion planning that allowed path deviations to virtually erase these segment vertices, and not rely on jerk (not a trivial coding task though).

              Is anything like that planned @dc42?

              undefined 1 Reply Last reply 2 Mar 2021, 18:12 Reply Quote 0
              • undefined
                dc42 administrators @CCS86
                last edited by 2 Mar 2021, 18:12

                @CCS86 said in Duet Maestro Struggling to Produce Smooth Curves:

                It would be far less taxing on the hardware to use motion planning that allowed path deviations to virtually erase these segment vertices, and not rely on jerk (not a trivial coding task though).

                Essentially you are askling RRF to second guess that the user wanted a curve, not facets. IMO that's the wrong approach. Jerk does not produce facets, it merely allow them to be printed without slowing down at each junction.

                The correct approach is for the input GCode to have either facets too fine to see, or not gacets at all and G2/G3 curves instead. The focus of RRF should be to be able to print those curves without visible facets. As it happens, I already did some work in RRF 3.3 to make the computations more efficient, which will allow finer segmentation of curves. If you wish, you can try out a 3.3 internal build and we can work together to establish how fine we can make the segments.

                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

                undefined 1 Reply Last reply 2 Mar 2021, 19:58 Reply Quote 1
                • undefined
                  CCS86 @dc42
                  last edited by 2 Mar 2021, 19:58

                  @dc42

                  That's a fair point for sure. Inferring the user intention is very difficult.

                  One approach could be to only allow this "path smoothing" on segments below a certain length threshold and below a certain angular separation; both user defined, along with the max deviation. It seems like this would put the user firmly in control.

                  I'm happy to do some testing on 3.2 vs 3.3. I actually haven't managed to choke 3.2 yet, so that would be the first order of business!

                  1 Reply Last reply Reply Quote 0
                  • undefined
                    MJLew
                    last edited by 2 Mar 2021, 20:49

                    @dc42 Does the firmware use a finer G2/G3 arc segment for Duet boards with better calculation capacity?

                    I'm working with G2/G3 segments on my Duet 2 Wifi and I can occasionally see fine facets in cylinders (occasionally as in when everything else worked well!).

                    undefined 1 Reply Last reply 2 Mar 2021, 22:49 Reply Quote 0
                    • undefined
                      dc42 administrators @MJLew
                      last edited by 2 Mar 2021, 22:49

                      @MJLew said in Duet Maestro Struggling to Produce Smooth Curves:

                      @dc42 Does the firmware use a finer G2/G3 arc segment for Duet boards with better calculation capacity?

                      I'm working with G2/G3 segments on my Duet 2 Wifi and I can occasionally see fine facets in cylinders (occasionally as in when everything else worked well!).

                      Currently, all boards use the same segment length. It would probably make sense to use finer segments on boards with floating point hardware.

                      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

                      1 Reply Last reply Reply Quote 0
                      • undefined
                        CCS86
                        last edited by CCS86 3 Mar 2021, 14:24 3 Mar 2021, 14:19

                        Okay, it looks like I was able to choke the Duet Maestro with RRF3.2 at 95mm/s printing 0.17mm segments.

                        So, just about 560 segments per second.

                        Scheduled moves 97706, completed moves 97706, hiccups 0, stepErrors 0, LaErrors 0, Underruns [26740, 0, 19], CDDA state -1
                        

                        Added cylinder in Superslicer (20x20x20).
                        2 walls.
                        Speed varied every 2mm from 60mm/s - 112mm/s.
                        XY accel = 3000 mm/s/s.
                        XY jerk = 10 mm/s

                        48833d9d-8965-486d-a6fa-50f528498d8e-image.png

                        choke.gcode

                        undefined 1 Reply Last reply 18 Apr 2021, 11:45 Reply Quote 0
                        • undefined
                          dc42 administrators
                          last edited by 3 Mar 2021, 14:43

                          Thanks, it looks like there is scope to increase the maximum segments/sec for G2/G3 moves then.

                          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

                          undefined 1 Reply Last reply 3 Mar 2021, 20:45 Reply Quote 1
                          • undefined
                            CCS86 @dc42
                            last edited by CCS86 3 Mar 2021, 20:45 3 Mar 2021, 20:45

                            @dc42 said in Duet Maestro Struggling to Produce Smooth Curves:

                            Thanks, it looks like there is scope to increase the maximum segments/sec for G2/G3 moves then.

                            I'm guessing that on your end steps/sec might be more important, these are 0.9* steppers with the following configuration:

                            M92 X159.93 Y159.75                       ; set steps per mm
                            M350 X16 Y16 I1                           ; configure microstepping with interpolation
                            
                            1 Reply Last reply Reply Quote 0
                            • undefined
                              dc42 administrators
                              last edited by 4 Mar 2021, 11:41

                              @CCS86 I have put new 3.3beta firmware builds with finer G2/G3 segmentation at https://www.dropbox.com/sh/ian1cpllo0oexzy/AACLMSPaWhTXSrGcMieHT2uoa?dl=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

                              1 Reply Last reply Reply Quote 1
                              • undefined
                                _Domaa @CCS86
                                last edited by 18 Apr 2021, 11:45

                                @ccs86 Hello, i think i have a similar problem with printing smooth curves. Have you solved this problem, and if so, how? Thanks

                                undefined 1 Reply Last reply 21 Apr 2021, 12:19 Reply Quote 0
                                • undefined
                                  CCS86 @_Domaa
                                  last edited by 21 Apr 2021, 12:19

                                  @_domaa said in Duet Maestro Struggling to Produce Smooth Curves:

                                  @ccs86 Hello, i think i have a similar problem with printing smooth curves. Have you solved this problem, and if so, how? Thanks

                                  I would suggest reading this whole thread. There is a lot of good info, not just one answer.

                                  1 Reply Last reply Reply Quote 1
                                  • undefined CCS86 referenced this topic 29 Nov 2023, 15:25
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