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    Parallel Scara, Five Bar Scara

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    • JoergS5
      JoergS5 last edited by JoergS5

      This is a follow up of https://forum.duet3d.com/topic/5651/parallel-scara

      If you are interested in parallel Scara, please check whether my documentation in https://duet3d.dozuki.com/Guide/Five+Bar+Parallel+SCARA/24?lang=en seems to be valid:

      • is the description and images ok?

      • are the parameters of M669 understandable and the parameters ok? @dc42 is defining the parameters with this letters ok?

      • do you miss an important construction option which I should add?

      Next step for me is to implement the Kinematics file, I have finished the algorithms. The necessary other source changes of Step 6 cannot checked in by me, because then I cannot make a push request.

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      • Falkia
        Falkia last edited by

        @JoergS5 any pros/cons about using proximalDistance=0 (like the Morgan type)?
        The kinematics must be easier that way.

        Printer: "Deltacus" Delta with 510mm bed diameter and 925mm build height. Powered by Duet 2 WiFi. Duet Smart Effector with E3D Volcano.

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

          @falkia You're absolutely right, it is much easier to calculate. It is included in the configuration by setting proximalDistance to 0. But it may be easier to construct a Scara with distance > 0, because you can place the steppers side by side. So I wanted to give all options for the user.

          With proximalDistance=0 and the arm lengths all the same, calculation would be very easy: only one middle angle and the radius. I documented the details in the wiki.

          One aspect where I don't have an answer yet is which solution is best. Some proximalDistance may be advantageous for the print area, speed, stability or precision. I will test it.

          One could change proximalDistance to influence print area and precision also with an additional actuator.

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          • dc42
            dc42 administrators last edited by

            I've had a quick look at it. It appears OK to me except that I suggest you make some changes to the M669 parameters:

            • K is reserved for kinematics type, so you need to use a different letter for the working mode.
            • I suggest you use X and Y for the origin offset, just as serial SCARA does. So choose a different letter for the proximal distance.
            • In your description of the A parameter, you have specified two different defaults.

            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

            JoergS5 1 Reply Last reply Reply Quote 0
            • JoergS5
              JoergS5 @dc42 last edited by

              @dc42 Thank you for review, I will make the changes. The defaults for A mean the first is for nnn:mmm, the second for ppp:qqq. I will make that clearer.

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              • JoergS5
                JoergS5 @JoergS5 last edited by

                Just a status update:

                I've added code to https://github.com/JoergS5/RepRapFirmware/tree/v2-dev now, implementing FiveBarScaraKinematics.cpp and .h. The checked-in version is buildable. The necessary changes in the checked out files are described in step 7 of the documentation (I cannot check it in because of later github push reason).

                I've changed some details in the documentation also. Next I will finish the prototype build and test the code. One thing I am not sure it is working is the homing procedure.

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