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    Mismatching stepper pulley and idler?

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    • Wyvern
      Wyvern last edited by Wyvern

      Surprisingly finding such a simple thing is a PITA online.

      I have had 16T pulleys to put in my X/Y axes, but I have 20T idlers, could the angle of which the belt travel have any issues when using them on a Z axis bed Cartesian give me any issues? I'm thinking there is a possibility that the belt will push or pull against the axis.

      Thanks.

      Stephen6309 1 Reply Last reply Reply Quote 0
      • Stephen6309
        Stephen6309 @Wyvern last edited by

        @wyvern Make sure the side of the idler and pulleys has a straight path on the side the belt connects to the z bed.

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        • Wyvern
          Wyvern last edited by

          My belt driven bed is fine where it is, I will not be changing that axis.

          I'm not sure I understand the answer.

          Stephen6309 1 Reply Last reply Reply Quote 0
          • Stephen6309
            Stephen6309 @Wyvern last edited by Stephen6309

            @wyvern Have the belt running in a straight line on the side it drives the axis.

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            • Wyvern
              Wyvern last edited by Wyvern

              Well, I'm unable to move the idler or steppers without some modification. Right now it would form a V.

              In short it sounds like I will be needing to go .9 in order to increase resolution.

              Stephen6309 1 Reply Last reply Reply Quote 0
              • Stephen6309
                Stephen6309 @Wyvern last edited by

                @wyvern When it is V shaped, there is a small amount of change in the distance the axis moves between the center and at the end of the axis. You may not see the change in an actual print.

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                • Phaedrux
                  Phaedrux Moderator last edited by

                  This may help: https://forum.duet3d.com/topic/8460/must-pulley-and-idler-sizes-match

                  Z-Bot CoreXY Build | Thingiverse Profile

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                  • Wyvern
                    Wyvern last edited by

                    Yeah, so that's a no-go as I expected.

                    Looks like I need to save up another $75 for steppers. Trying to get this thing as accurate as possible.

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                    • bot
                      bot last edited by

                      Buying different steppers will have no effect in correcting this problem. You have to either accept the small error caused by non-parallel belt path, or make it parallel to the axis.

                      *not actually a robot

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                      • SupraGuy
                        SupraGuy last edited by

                        0_1549482357842_UnevenPulley.png
                        If your axis is aligned like this, it will be okay. With this alignment, the clamp for the X or Y axis will move parallel to the direction of the axis, and even if the other side of the belt does not, it will be okay, so long as that part of the belt does not interfere with anything else.

                        It is probably easiest to get this kind of alignment using the same size pulleys for both, since the centers then are parallel to the axis direction as well, but this kind of alignment is still possible.

                        If you put the centers of uneven clamps like this, you get funny motion, since the overall length of the belt has to change.

                        Lead screw driven printer, powered by Duet 2 Wifi
                        MPCNC powered by Duet 2 Wifi
                        CoreXY printer driven by Duet 3 6HC
                        LowRider CNC powered by Duet 2 Wifi

                        Wyvern 1 Reply Last reply Reply Quote 1
                        • Wyvern
                          Wyvern @SupraGuy last edited by

                          @supraguy My setup is good now, 20t/20t.

                          I asked because I want to bump up resolution and had 16t pulleys.

                          So without fixing what isn't broken, I will just get .9 steppers.

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                          • SupraGuy
                            SupraGuy last edited by SupraGuy

                            I hope that the belt is straight between the idler and the motor pulley where it's clamped. The rest of the belt path doesn't matter, but if the belt has to deflect to go to the part where it clamps to the moving part, then you will have inaccuracies due to parallax that get worse the closer to the motor end that you get.

                            EDIT: If the 20T pulleys is how it came initially, then that's probably perfect.

                            Lead screw driven printer, powered by Duet 2 Wifi
                            MPCNC powered by Duet 2 Wifi
                            CoreXY printer driven by Duet 3 6HC
                            LowRider CNC powered by Duet 2 Wifi

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