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Z axis issue: wrong movement (layers)

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  • undefined
    zecchi @Phaedrux
    last edited by 30 Dec 2019, 08:17

    @Phaedrux said in Z axis issue: wrong movement (layers):

    Can you test the repeatability of your Z axis? Set to a known position marker and then move the z axis up and down many times and see if it returns to the same starting position.

    Thanks for your replay.
    I'll try later.

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    • undefined
      zecchi @Phaedrux
      last edited by 30 Dec 2019, 08:21

      @Phaedrux said in Z axis issue: wrong movement (layers):

      Is there a gear reduction involved?

      There is a 1 to 1 ratio

      1 Reply Last reply Reply Quote 0
      • undefined
        zecchi @Phaedrux
        last edited by 30 Dec 2019, 08:24

        @Phaedrux said in Z axis issue: wrong movement (layers):

        Is the belt slipping the teeth?

        Belts are quite tight, I don't think they can slip (I hope… no noises , nothing that make me to think they are slipping )

        1 Reply Last reply Reply Quote 0
        • undefined
          zecchi @Phaedrux
          last edited by 30 Dec 2019, 08:27

          @Phaedrux said in Z axis issue: wrong movement (layers):

          Ideally you should set the current to be 70-85% of the rated max current of the motor.

          Ok, it was too low. I set 1200 mA (80% of 1.5A). Unfortunately the error doesn't disappear.

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          • undefined
            zecchi @Phaedrux
            last edited by 30 Dec 2019, 08:32

            @Phaedrux said in Z axis issue: wrong movement (layers):

            You're using anti-backlash nuts. They typically are not necessary on the Z axis since there is constant downward force on the bed from gravity and the bed is always dropping away from the nozzle during a print. They can increase friction however to the point they cause binding.
            Have you lubricated the lead screws?

            I'll try to remove nuts and use normal ones. Also I'll try to clean and re-lubricate the lead screws

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            • undefined
              zecchi
              last edited by 1 Jan 2020, 09:19

              News:
              -Repetitivety Is ok, tested with a dial indicator
              -I've change the nut. Some improvements but the error doesn't disappear.

              Other advices?

              undefined 1 Reply Last reply 1 Jan 2020, 16:56 Reply Quote 1
              • undefined
                SIam
                last edited by 1 Jan 2020, 13:06

                it looks like a z-wobble dubble (tripple) check the Z-Axis motion this must be stable and run smooth (it can be a nightmare to find the right position)

                Hypercube-Evolution-Hybrid, Piezo Orion, Orbiter
                Duet WiFi 1.02 or later + DueX5
                RepRapFirmware for Duet 2 WiFi/Ethernet 3.4.0beta4 (2021-09-27 11:30:36)
                Duet WiFi Server: 1.26
                Duet Web Control 3.4.0beta4 (2021-09-27)

                undefined 1 Reply Last reply 1 Jan 2020, 16:54 Reply Quote 0
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                  zecchi @SIam
                  last edited by 1 Jan 2020, 16:54

                  @SIam
                  I've printed a piece in order to fix the lead screws at the exactly center of the two rods, quite good but I didn't solve the problem.

                  Any suggestions?

                  1 Reply Last reply Reply Quote 0
                  • undefined
                    Phaedrux Moderator @zecchi
                    last edited by 1 Jan 2020, 16:56

                    @zecchi said in Z axis issue: wrong movement (layers):

                    -I've change the nut. Some improvements but the error doesn't disappear.

                    Look for more sources of binding. The smooth rods and bearings would be my next target.

                    Z-Bot CoreXY Build | Thingiverse Profile

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                    • undefined
                      zecchi
                      last edited by 3 Jan 2020, 21:44

                      Also rods are checked. Z axes is absolutely perfect, tested with a dial indicator (only 0.01mm of error in 300mm ). I've also printed a jig in order to have the rods at the same distance.
                      But , layer are, still, inconstant (0.24, 0.18, 0.22 ecc...) And this cause the blob (I'm pretty sure about that ).

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                      • undefined
                        Phaedrux Moderator @Phaedrux
                        last edited by 3 Jan 2020, 21:48

                        @Phaedrux said in Z axis issue: wrong movement (layers):

                        What is the full step resolution of your z axis?

                        @zecchi What is the pitch/lead of your lead screws?

                        The problem really seems to be similar to trying to print at a layer height that isn't a multiple of the full step resolution of the Z axis.

                        https://blog.prusaprinters.org/calculator/#optimallayer

                        Z-Bot CoreXY Build | Thingiverse Profile

                        undefined 2 Replies Last reply 3 Jan 2020, 21:50 Reply Quote 0
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                          zecchi @Phaedrux
                          last edited by 3 Jan 2020, 21:50

                          @Phaedrux
                          2mm pitch. (I ordered the 8mm pitch but it arrived wrong).

                          undefined 1 Reply Last reply 3 Jan 2020, 21:58 Reply Quote 0
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                            zecchi @Phaedrux
                            last edited by 3 Jan 2020, 21:53

                            @Phaedrux
                            I've shorter 8mm pitch lead screws. I'll try with them.

                            1 Reply Last reply Reply Quote 0
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                              Phaedrux Moderator @zecchi
                              last edited by 3 Jan 2020, 21:58

                              @zecchi said in Z axis issue: wrong movement (layers):

                              2mm pitch.

                              Well there goes that theory.

                              With a 2mm lead, and 1.8 degree motors (deduced from your 1600 steps per mm on Z) your full step resolution is 0.01mm. So you have no limits there.

                              What are the motor specs?

                              Z-Bot CoreXY Build | Thingiverse Profile

                              undefined 1 Reply Last reply 3 Jan 2020, 22:11 Reply Quote 0
                              • undefined
                                zecchi @Phaedrux
                                last edited by 3 Jan 2020, 22:11

                                @Phaedrux
                                So, if my layer height is 0.2mm isn't a problem, correct?

                                Motor: 1.5A , 1.8°. Classic 17HS4401 stepper motor.

                                undefined 2 Replies Last reply 3 Jan 2020, 22:17 Reply Quote 0
                                • undefined
                                  Phaedrux Moderator @zecchi
                                  last edited by 3 Jan 2020, 22:17

                                  @zecchi said in Z axis issue: wrong movement (layers):

                                  @Phaedrux
                                  So, if my layer height is 0.2mm isn't a problem, correct?

                                  Correct

                                  Z-Bot CoreXY Build | Thingiverse Profile

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                                  • undefined
                                    Phaedrux Moderator @zecchi
                                    last edited by 3 Jan 2020, 22:19

                                    @zecchi said in Z axis issue: wrong movement (layers):

                                    Motor: 1.5A , 1.8°. Classic 17HS4401 stepper motor.

                                    I'm unable to find a data sheet that seems close. There are many sub-models of 17H4401 between many manufacturers. I didn't even see any that were 1.5a.

                                    Can you find a data sheet that seems to match your motor based on what you know about it?

                                    Z-Bot CoreXY Build | Thingiverse Profile

                                    undefined 1 Reply Last reply 3 Jan 2020, 23:41 Reply Quote 0
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                                      zecchi @Phaedrux
                                      last edited by 3 Jan 2020, 23:41

                                      @Phaedrux
                                      Second line of this datasheet:
                                      17HS2408-MotionKing.pdf

                                      Now I realize that the seller made fun of me selling this motor as 1.5A instead 1.3A (I re-cecked and in the description is written 1.5A😠 ).

                                      undefined 1 Reply Last reply 3 Jan 2020, 23:43 Reply Quote 0
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                                        zecchi @zecchi
                                        last edited by zecchi 1 Mar 2020, 23:46 3 Jan 2020, 23:43

                                        @zecchi
                                        My fault , the line is actually the number eight. So the current is 1.7A. awesome.

                                        This is the link :
                                        € 21,62 20%OFF | Nema17 Stepper Motor 42 motor Nema 17 motor 42BYGH 1.5A 38mm 17HS4401 motor 4-lead for 3D printer CNC
                                        https://a.aliexpress.com/BBHPrX2gL

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                                        • undefined
                                          zecchi
                                          last edited by 4 Jan 2020, 23:46

                                          This is the response to M122 command:

                                          Screenshot_20200104-212211.jpg

                                          Screenshot_20200104-212217.jpg

                                          Screenshot_20200104-212224.jpg

                                          If you see something strange ,please let me know.

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