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    Scara Problem

    Scheduled Pinned Locked Moved
    Firmware installation
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    • JoergS5undefined
      JoergS5 @Mauxx
      last edited by JoergS5

      @Mauxx Thanks for the code basis. The included ScaraKinematics seems to be the same like in the official code base, so this is propably not the problem.

      One possible reason ... (removed, this was not the reason...)

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      • Mauxxundefined
        Mauxx
        last edited by

        So with a Duet Board i will solve this problem? Great!!!☺
        Which board do you suggest?

        JoergS5undefined 1 Reply Last reply Reply Quote 0
        • JoergS5undefined
          JoergS5 @Mauxx
          last edited by

          @Mauxx I would choose Duet2 Wifi or Ethernet. The new Duet 3 is not needed for the application. The Maestro doesn't have FPU, and floating point algorithms are used in Scara. If you want to experiment a lot in the future, a Duet 3 is an option of course. It is a matter of budget also of course.
          I have personally a Duet 2 Wifi and Duet 3+Pi 4 and both are great.

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          • Mauxxundefined
            Mauxx
            last edited by

            nice!!!
            if you tell me that with duet there's no issues, i trust you

            JoergS5undefined 1 Reply Last reply Reply Quote 0
            • JoergS5undefined
              JoergS5 @Mauxx
              last edited by

              @Mauxx I have not tested the Scara, but I give you the following promise: if there is an error in the Scara code, I will help fixing it.

              I have created a parallel Scara printer:
              https://duet3d.dozuki.com/Guide/Five+Bar+Parallel+SCARA/24?lang=en
              and source in
              https://github.com/JoergS5/RepRapFirmware
              for RRF2, so I have expertise.
              Maybe you're interested in building a parallel scara in the future also?

              Mauxxundefined 1 Reply Last reply Reply Quote 0
              • Mauxxundefined
                Mauxx
                last edited by

                I still don't know if I'll build a parallel scara,
                howerver i see @dc42 Scara printer, maybe he can tell us if everything work good?

                JoergS5undefined 1 Reply Last reply Reply Quote 0
                • Mauxxundefined
                  Mauxx @JoergS5
                  last edited by

                  @JoergS5 Nice work!!!

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                  • JoergS5undefined
                    JoergS5 @Mauxx
                    last edited by

                    This post is deleted!
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                    • dc42undefined
                      dc42 administrators
                      last edited by dc42

                      The SCARA code includes a feature whereby if the start and end points of a non-extruding G1 move are reachable but the move can't be executed because it would pass too close to the proximal axis, the move is silently changed into a G0 move instead. I implemented this feature at the request of another SCARA user. From your video, my guess is that this code is being triggered incorrectly.

                      What I don't know is whether this problem occurs when running RRF on a Duet, or only in the LPC fork. I've never observed it on my SCARA printer, but I don't use it very much.

                      The code concerned is in two parts. The most important part is lines 291-304 of https://github.com/dc42/RepRapFirmware/blob/dev/src/Movement/Kinematics/ScaraKinematics.cpp. This determines whether a linear trajectory is possible, by determining whether the closest approach of the trajectory to the proximal axis lies between the start and end points, and if so what that distance is and whether it is smaller than the minimum radius. Perhaps there is an error in this code.

                      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

                      Danalundefined 1 Reply Last reply Reply Quote 0
                      • Mauxxundefined
                        Mauxx
                        last edited by

                        soon I will buy duet wifi or ethernet
                        thank you all for your support
                        I really hope you can fix this issue, because the firmware is really cool !!!

                        @dc42 if you can check it on your Scara, all you have to do is print 3 cubes, one of which must be on the central axis of the print bed

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                        • Danalundefined
                          Danal @dc42
                          last edited by

                          @dc42 said in Scara Problem:

                          The SCARA code includes a feature whereby if the start and end points of a non-extruding G1 move are reachable but the move can't be executed because it would pass too close to the proximal axis,

                          @dc42 Except it also does it when the move is nowhere near the proximal axis. About 3:10 in the video.

                          Of course, a severe enough error could still cause this behavior. It is interesting to note that all the places that do it (or that I see doing it) fit the "closest approach of the trajectory to the proximal axis lies between the start and end points" case. Hmmm...

                          @Mauxx I would also highly recommend a genuine Duet 2.

                          Delta / Kossel printer fanatic

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                          • dc42undefined
                            dc42 administrators
                            last edited by

                            I think I have found the problem. The calculation of the minimum achievable radius is incorrect. This doesn't show up on my SCARA printer because the distal angle range is B-27:157.5 which results in a calculated minimum radius of 75mm, only a little higher than the true value of 63mm. But you have a distal range that is symmetrical about zero, which results in the minimum radius being calculated as 387mm instead of 107mm. As a result, any line that passes within 387mm of the proximal axis at its closest point will get converted to a G0 movement, unless one of the end points of the line is exactly at the closest point.

                            I will fix this in the next release. Meanwhile, as a workaround I suggest you use B-149:31 in your M669 command, which will result in the correct minimum radius calculation.

                            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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                            • Mauxxundefined
                              Mauxx
                              last edited by Mauxx

                              @dc42 Thank you very much David @Danal and @JoergS5 , I followed your advice and set the angles of the Distal B-31: 149 arm (not B-149: 31 because I have Ymax Endstop) and now it works perfectly !!!

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                              • Mauxxundefined
                                Mauxx
                                last edited by

                                @dc42 I was wondering if when you fix the error in the next release, my scara will work like the helios, which manages to reverse the distal arm (like in this video at 0:51 https://www.youtube.com/watch?v=l_FVnIYND4Y ) it would be really cool!!!

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

                                  RepRapFirmware does in theory support switching arm modes already, but I can't test it on my SCARA machine because the distal joint doesn't have enough range.

                                  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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                                  • oliofundefined
                                    oliof
                                    last edited by

                                    I believe mine does. How would I test?

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

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

                                      @oliof said in Scara Problem:

                                      I believe mine does. How would I test?

                                      Use a G0 command to command movement to a point that is reachable in the other arm mode but not the current one.

                                      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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