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Bed levelling - just z probe, or 2 indep. motors with G32?

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  • undefined
    Reefwarrior
    last edited by 21 Mar 2021, 19:50

    Hi,

    The above have reference. Will a normal mesh grid compensation be enough in order to circumvent possible bed unevenness; or is dual Z motors driven independently of each other the way to go? This setup is basically on an Ender3 with a DuetWifi. I just came across a posting now that said the G32 is basically 'decommissioned'.

    Sorry about the huge amounts of postings - trying to get a lot done as this project has been dragging on now for more than a year!

    Rgds
    Tinus

    undefined undefined 2 Replies Last reply 21 Mar 2021, 19:55 Reply Quote 0
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      DIY-O-Sphere @Reefwarrior
      last edited by 21 Mar 2021, 19:55

      This post is deleted!
      1 Reply Last reply Reply Quote 0
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        fcwilt
        last edited by fcwilt 21 Mar 2021, 20:06

        Hi,

        Bed Leveling (BL), be it automatic or manual, and Mesh Bed Compensation (MBC) are aimed at two different problems.

        While MBC can help cope with a bed in need of leveling it is not an ideal solution.

        MBC is best suited to coping with bed irregularities.

        If you wish BL to be Automatic you need at least 2 independent Z steppers but 3 are much better.

        You can get by with the Manual Bed Leveling Assistant (MBLA) which requires 3 or 4 bed leveling screws that you can turn by hand in response to the required adjustments reported by the MBLA.

        I have 1 printer equipped with 3 Z Steppers and 2 with bed leveling "thumb" screws.

        Being able to auto level the bed is a joy.

        Frederick

        undefined 1 Reply Last reply 21 Mar 2021, 20:10 Reply Quote 0
        • undefined
          Reefwarrior @fcwilt
          last edited by 21 Mar 2021, 20:10

          @fcwilt I think then it was the bed leveling that I actually need 🙂 Yes I have 2 indep. Z stepper motors - I am building a heavy modified Folgertech FT-5 and it will have 3 z steppers - so too my MGN BLV Cube that is still in pieces! 🙂

          undefined 1 Reply Last reply 21 Mar 2021, 20:14 Reply Quote 0
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            fcwilt @Reefwarrior
            last edited by 21 Mar 2021, 20:14

            @Reefwarrior said in Bed levelling - just z probe, or 2 indep. motors with G32?:

            @fcwilt I think then it was the bed leveling that I actually need 🙂 Yes I have 2 indep. Z stepper motors - I am building a heavy modified Folgertech FT-5 and it will have 3 z steppers - so too my MGN BLV Cube that is still in pieces! 🙂

            The FT5 would be a good candidate for converting to 3 Z steppers.

            I have one but it is still equipped with the 3 bed leveling "thumb" screw adjustements.

            The printer equipped with 3 Z steppers is one of my own design and I could not be happier with it.

            Frederick

            undefined 1 Reply Last reply 21 Mar 2021, 20:20 Reply Quote 0
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              Reefwarrior @fcwilt
              last edited by 21 Mar 2021, 20:20

              @fcwilt Ok, so I did a few changes in my configuration files:

              config.g

              M671 X:32.5:202.5 Y:32.5:202.5 P0.5

              bed.g
              G28
              M401
              G30 P0 X32.5 Y32.5 Z-99999
              G30 P1 X202.5 Y32.5 Z-99999
              G30 P2 X32.5 Y202.5 Z-99999
              G30 P3 X202.5 Y202.5 Z-99999 S3
              M402

              After running G32, I get:
              G32
              Error: Calibration failed, computed corrections: nan nan nan

              Board: Duet 2 WiFi (2WiFi)
              Firmware: RepRapFirmware for Duet 2 WiFi/Ethernet 3.2.2 (2021-02-11)
              Duet WiFi Server Version: 1.25

              Note: You can install updates on the System page.

              Tinus 🙂

              1 Reply Last reply Reply Quote 0
              • undefined
                Reefwarrior
                last edited by 21 Mar 2021, 20:22

                think I may have found the problem - the 'S' in the last G30 must be S4; as there are 4 screws, not 3....

                undefined 1 Reply Last reply 21 Mar 2021, 20:24 Reply Quote 0
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                  fcwilt @Reefwarrior
                  last edited by fcwilt 21 Mar 2021, 20:24

                  This post is deleted!
                  undefined 1 Reply Last reply 21 Mar 2021, 20:25 Reply Quote 0
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                    Reefwarrior @fcwilt
                    last edited by 21 Mar 2021, 20:25

                    @fcwilt The P is for the thread pitch ....

                    I got this: Error: Number of calibration factors (4) not equal to number of leadscrews (3)

                    undefined 1 Reply Last reply 21 Mar 2021, 20:27 Reply Quote 0
                    • undefined
                      fcwilt @Reefwarrior
                      last edited by fcwilt 21 Mar 2021, 20:27

                      @Reefwarrior said in Bed levelling - just z probe, or 2 indep. motors with G32?:

                      @fcwilt The P is for the thread pitch ....

                      I got this: Error: Number of calibration factors (4) not equal to number of leadscrews (3)

                      Arggggg.....

                      My bad - I confused the S and P parameters.

                      When am I going to learn to not trust to memory....

                      Frederick

                      undefined 1 Reply Last reply 21 Mar 2021, 20:31 Reply Quote 0
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                        Reefwarrior @fcwilt
                        last edited by 21 Mar 2021, 20:31

                        @fcwilt hahahaha no stress 🙂

                        1 Reply Last reply Reply Quote 1
                        • undefined
                          Reefwarrior
                          last edited by 21 Mar 2021, 20:35

                          Can't seem to sort out the 'Number of calibration factors....' error.....

                          1 Reply Last reply Reply Quote 0
                          • undefined
                            Reefwarrior
                            last edited by 21 Mar 2021, 20:47

                            Eureka!

                            G32
                            Manual corrections required: 0.00 turn up (0.00mm) 0.00 turn down (0.00mm) 0.76 turn up (-0.38mm) 0.81 turn up (-0.41mm)

                            The M671 I used to define the springs positions was not correct.

                            undefined 1 Reply Last reply 21 Mar 2021, 21:27 Reply Quote 1
                            • undefined
                              fcwilt @Reefwarrior
                              last edited by 21 Mar 2021, 21:27

                              @Reefwarrior said in Bed levelling - just z probe, or 2 indep. motors with G32?:

                              Eureka!

                              G32
                              Manual corrections required: 0.00 turn up (0.00mm) 0.00 turn down (0.00mm) 0.76 turn up (-0.38mm) 0.81 turn up (-0.41mm)

                              The M671 I used to define the springs positions was not correct.

                              The : character after the X and Y?

                              Frederick

                              1 Reply Last reply Reply Quote 0
                              • undefined
                                Phaedrux Moderator @Reefwarrior
                                last edited by 22 Mar 2021, 03:55

                                @Reefwarrior said in Bed levelling - just z probe, or 2 indep. motors with G32?:

                                This setup is basically on an Ender3 with a DuetWifi.

                                I wouldn't bother changing the Ender3 to a dual Z axis setup. It's not necessary. When assembled properly the design is adequate for keeping the X gantry level. The bed can be manually leveled pretty easily, and mesh compensation can take care of the rest.

                                There's something to be said for simplicity. Once you add a second Z axis motor you have to calibrate it because it won't stay in sync over time.

                                Also, 2 Z motors will only give you tilt correction along a single axis. You need 3 motors to do a 3 point plane. So you'd still be using mesh compensation and manual leveling anyway.

                                So I say avoid a second z axis motor if the printer design allows for it.

                                Z-Bot CoreXY Build | Thingiverse Profile

                                undefined 2 Replies Last reply 22 Mar 2021, 05:45 Reply Quote 0
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                                  Reefwarrior @Phaedrux
                                  last edited by 22 Mar 2021, 05:45

                                  @Phaedrux Hi, thank you for the reply. I have extended my Z and my X axis and noticed drooping on the one side if the Z raises... hence the reason now for the second motor 🙂

                                  1 Reply Last reply Reply Quote 0
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                                    Reefwarrior @Phaedrux
                                    last edited by 22 Mar 2021, 06:02

                                    @Phaedrux I'm probably going too complicated now, but won't it help to have 2 indep. motors, have it correct tilt and then bed level assistant for the rest? If I read it correctly, I can not have both 2 indep and MBLA at the same time, or have I misunderstood something? 🙂

                                    undefined 1 Reply Last reply 22 Mar 2021, 18:46 Reply Quote 0
                                    • undefined
                                      Phaedrux Moderator @Reefwarrior
                                      last edited by 22 Mar 2021, 18:46

                                      @Reefwarrior said in Bed levelling - just z probe, or 2 indep. motors with G32?:

                                      If I read it correctly, I can not have both 2 indep and MBLA at the same time, or have I misunderstood something?

                                      Yes you can use both, but there needs to be a reference somewhere. If you do the tilt correction based on the bed surface, but then change the bed surface itself with MBLA your tilt correction is now changed as well.

                                      Maybe a better solution would be to correct for gantry tilt with 2 endstops at the top of the frame so that you're leveled to the frame as a reference. Then you can adjust the plane of the bed to match the frame.

                                      Z-Bot CoreXY Build | Thingiverse Profile

                                      undefined 1 Reply Last reply 23 Mar 2021, 03:37 Reply Quote 0
                                      • undefined
                                        Reefwarrior @Phaedrux
                                        last edited by 23 Mar 2021, 03:37

                                        @Phaedrux Awesome, thanx! 🙂

                                        1 Reply Last reply Reply Quote 0
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