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    CoreXY - speed constrained?

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    • pro3dundefined
      pro3d
      last edited by

      I did set firmware to 300 max speed

      In this video I ask for 300mms just to check the mechanics. Somehow it says 212/214 on some movements

      What can be the reason?

      Go to 2 minutes in the video
      https://youtu.be/hVf9eABEwaI

      Valkyrie DIY High Temp 3D Printer

      R&D - Engineering Designer - Viking 3D Printers
      https://vkingprinter.com/

      JoergS5undefined deckingmanundefined 2 Replies Last reply Reply Quote 0
      • JoergS5undefined
        JoergS5 @pro3d
        last edited by JoergS5

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

          Movement on a diagonal is done by just one motor working twice as hard, so the firmware limits the speed and acceleration to half the values for pure X or Y movement that you configure in the M203 and M201 commands in config.g.

          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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          • deckingmanundefined
            deckingman @pro3d
            last edited by

            @pro3d Can you post your config.g and also a sample of the gcode file you were trying to print.

            BTW, having looked at your video and heard your comments, it is possible to print at 300 mm/sec ☺

            https://somei3deas.wordpress.com/2018/10/14/real-3d-printing-at-high-speeds-and-even-higher-melt-rates-with-a-large-nozzle/

            Here is what it looks like (300mm/sec is from about 10 mins 20 secs) https://www.youtube.com/watch?v=rUV5IZxfAxU&t=697s

            Ian
            https://somei3deas.wordpress.com/
            https://www.youtube.com/@deckingman

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            • thweundefined
              thwe
              last edited by

              recently I had also checked my mechanics - see the video:

              https://youtu.be/Vj9jpNAjHS4

              movements in the straight were also fully extended, the oblique movements and the circle are at max. 330 - 360 mm/s

              (I think that's more than enough 🙂 )

              Thomas

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              • pro3dundefined
                pro3d @dc42
                last edited by pro3d

                @dc42 said in CoreXY - speed constrained?:

                Movement on a diagonal is done by just one motor working twice as hard, so the firmware limits the speed and acceleration to half the values for pure X or Y movement that you configure in the M203 and M201 commands in config.g.

                Thanks for the response. I did not understand what you mean. Pure perpendicular movement when both motors are working has half the acceleration? So when 1500 in accel it does 750? Or the other way around?

                Edit
                I confused myself. Did you mean xy movement has acceleration reduced? Diagonally moved? One motor

                Valkyrie DIY High Temp 3D Printer

                R&D - Engineering Designer - Viking 3D Printers
                https://vkingprinter.com/

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                • dc42undefined
                  dc42 administrators
                  last edited by

                  The firmware has to treat accelerations and speeds on CoreXY machines differently from Cartesian.

                  On a Cartesian printer, the X and Y motions are independent, so X and Y speed limits and accelerations are applied independently. This means that the speed and acceleration that the firmware will allow for a diagonal move is sqrt(2) times the speed for a pure X or Y move (if the X and Y speed limits ar3e the same, and similarly for the accelerations).

                  On a CoreXY printer, pure X and Y moves are done by both motors contributing equally. But pure diagonal moves are done by just one motor. So whereas on a Cartesian printer, you can execute diagonal moves with greater acceleration and speed than X or Y moves, on a CoreXY the reverse is true.

                  You could argue that for a pure diagonal move, the speed and acceleration limits should be one quarter of the limits for pure X and Y moves: one half because one motor is doing all the work, and another half because that motor is moving both the X carriage and the Y gantry. But the current firmware doesn't go that far, it only takes account of how much of the total work each motor is doing.

                  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

                  pro3dundefined Phaedruxundefined 2 Replies Last reply Reply Quote 1
                  • pro3dundefined
                    pro3d @dc42
                    last edited by

                    @dc42 so what do I have to do to get same performance for diagonal movement as perpendicular? Or is this not possible

                    Valkyrie DIY High Temp 3D Printer

                    R&D - Engineering Designer - Viking 3D Printers
                    https://vkingprinter.com/

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                    • Phaedruxundefined
                      Phaedrux Moderator @dc42
                      last edited by

                      @dc42 I've sometimes wondered if it would make sense to rotate the solid infill direction in the slicer 45 degrees to take advantage of using both motors at the same time.

                      Z-Bot CoreXY Build | Thingiverse Profile

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                      • dc42undefined
                        dc42 administrators @pro3d
                        last edited by

                        @pro3d said in CoreXY - speed constrained?:

                        @dc42 so what do I have to do to get same performance for diagonal movement as perpendicular? Or is this not possible

                        It's not possible for a CoreXY printer to have the same peak performance for diagonal moves as for X or Y moves, that's in the nature of the mechanics. It would be possible to change the firmware to restrict the pure X and Y acceleration and speed so that it doesn't exceed what can be managed for diagonal moves; but would that really be useful?

                        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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                        • deckingmanundefined
                          deckingman
                          last edited by

                          @pro3d On the basis that two motors will always have more torque than one, then no - it isn't possible to get the same theoretical performance in both diagonal as perpendicular. Having said that, your ultimate print speed is constrained not by how fast you can move the axes, but by how fast you can melt and extrude filament. The simple thing to do is to spec the motors so that one motor is capable of accelerating the entire mass at the desired rate.
                          @Phaedrux On a coreXY yes, you could set infill to 90 degrees (or 0 degrees) but are you likely to be able to make use of that extra torque? Is you print speed currently constrained by the available motor torque? Or to put it another way, do you have to print 45 degree infill at lower speed because motor torque is the limiting factor?

                          Ian
                          https://somei3deas.wordpress.com/
                          https://www.youtube.com/@deckingman

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                          • pro3dundefined
                            pro3d @deckingman
                            last edited by

                            @deckingman I don't really print much faster than 60mms so my questions is due to my curious nature.

                            It was also new to me so I wonder how I can obtain the smoothest movement if jerk and acceleration is half on the diagonals. Then if I want minimum accel at 1500 I must set 3000 as accel if I understand. Then it will accelerate 3000 on perpendicular moves. Jerk will be the same and with 30 in jerk I think I will push the limits so I need to figure out what would be the solution with the best and smoothest performance in my case

                            Speed is not the issue here but acceleration and jerk

                            Valkyrie DIY High Temp 3D Printer

                            R&D - Engineering Designer - Viking 3D Printers
                            https://vkingprinter.com/

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                            • 691175002undefined
                              691175002
                              last edited by 691175002

                              I'm not sure if I'm misunderstanding something here, but I was under the impression that G1 coordinated moves will always respect the configured acceleration and velocity limits regardless of their orientation.

                              Physical kinematic limits should only affect motion when the commanded movement is not physically possible, which should never occur outside of deliberate testing.

                              As mentioned, Cartesian and CoreXY printers can produce faster movement when multiple motors are driven at the same time, but this should be completely irrelevant when slicing or printing models.

                              (The sole exception would be a G0 uncoordinated move, but I'm not sure if any 3d printer firmwares actually perform uncoordinated movement.)

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                              • DocTruckerundefined
                                DocTrucker
                                last edited by DocTrucker

                                There is a g code command to limit the print and travel accelerations.

                                I'd prefer to set the config file values to the maximum physical capability of the machine and then limit the actual accelerations on a per geometry type as Slic3r allows.

                                Running up to the physical limits like discussed here would result in different conditions for the deposition of the polymer depending on the deposition direction and that would potentially cause more orientation related artefacts.

                                Edit: That said Slic3r was implementing that badly last time I checked.

                                Running 3 P3Steel with Duet 2. Duet 3 on the shelf looking for a suitable machine. One first generation Duet in a Logo/Turtle style robot!

                                Phaedruxundefined 1 Reply Last reply Reply Quote 0
                                • pro3dundefined
                                  pro3d @691175002
                                  last edited by

                                  @691175002 I am mostly interessted in jerk primarily and then acceleration. Speed is always obtained but if jerk and accel are 50% on diagonals then I need to consider this when setting this in the firmware

                                  Valkyrie DIY High Temp 3D Printer

                                  R&D - Engineering Designer - Viking 3D Printers
                                  https://vkingprinter.com/

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                                  • Phaedruxundefined
                                    Phaedrux Moderator @pro3d
                                    last edited by

                                    @pro3d said in CoreXY - speed constrained?:

                                    Speed is always obtained but if jerk and accel are 50% on diagonals

                                    I didn't get the impression that this is the case from @dc42 s comments.

                                    Z-Bot CoreXY Build | Thingiverse Profile

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                                    • deckingmanundefined
                                      deckingman @pro3d
                                      last edited by

                                      @pro3d The worse case is moving the entire mass of both carriages with single motor. Unless you've got extremely heavy carriages and extremely small motors, the accelerations you use for printing will be far less than this worse case.

                                      But I think you are being unduly concerned. Do the maths. If you had acceleration set to 1500mm/sec^2, the to reach 60mm/sec would take 0.04 seconds and the print head would move 1.2mm during that acceleration phase. If you then double the acceleration to 3,000 mm/sec^2 then to reach 60mm/sec takes 0.02 seconds and the print head would move 0.6mm.

                                      That's assuming a start and end speed of zero. In reality, you would have jerk configured so the start and end speeds would be non zero.

                                      Ian
                                      https://somei3deas.wordpress.com/
                                      https://www.youtube.com/@deckingman

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                                      • Phaedruxundefined
                                        Phaedrux Moderator @DocTrucker
                                        last edited by

                                        @doctrucker said in CoreXY - speed constrained?:

                                        That said Slic3r was implementing that badly last time I checked.

                                        I just checked and from what I can tell Slic3r is using M204 S rather than P and T for acceleration adjustment when using RepRap flavor. Still seems to work though. At least they aren't using M201.

                                        Z-Bot CoreXY Build | Thingiverse Profile

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                                        • DocTruckerundefined
                                          DocTrucker
                                          last edited by

                                          Are you running dev version of Slic3r or stable 1.3.0?

                                          Running 3 P3Steel with Duet 2. Duet 3 on the shelf looking for a suitable machine. One first generation Duet in a Logo/Turtle style robot!

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                                          • Phaedruxundefined
                                            Phaedrux Moderator @DocTrucker
                                            last edited by

                                            @doctrucker slic3r PE 1.41.2

                                            Z-Bot CoreXY Build | Thingiverse Profile

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