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    Duet 2: using Z brake

    Duet Hardware and wiring
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    • TheGov
      TheGov last edited by Phaedrux

      Hi,

      I have been trying to find a brake principe for my belt driven Z axis for a while now.
      On the reprapforums someone adviced using a relay to short the 2 phases of a Nema stepper motor. I am just wondering how i should connect this to my Duet2 wifi board (i am aware this will void warranty). I was also informed the braking might not last long on a long and heavy Z axis (45 cm and +-5kg)

      Can anyone advice me how to connect this for a duet2 instead of a MKS board?

      Thanks in advance. For all interested, the info is on a russian link, just translate the page.
      https://3dtoday.ru/blogs/3dmaniack/sistema-tormozheniya-shd-posle-ego-otklyucheniya-v-2

      2ed7ad12-7c23-468f-89ae-59d34b6d74a6-image.png

      d2ebc40b-da5a-4463-a341-574859676c46-image.png

      dc42 DigiD 2 Replies Last reply Reply Quote 0
      • Phaedrux
        Phaedrux Moderator last edited by

        I think @oozeBot may have implemented something like this z brake.

        Z-Bot CoreXY Build | Thingiverse Profile

        1 Reply Last reply Reply Quote 1
        • oozeBot
          oozeBot last edited by

          Yes I did do this in an early prototype but we've now removed it as we found a way to better counter balance the gantry where it is no longer needed..

          Here is the only photo I have of it currently. It takes two relays per stepper.

          stepper brake.jpg

          1 Reply Last reply Reply Quote 1
          • fcwilt
            fcwilt last edited by

            Hi,

            I "solved" that problem, on my printer, by using 2mm pitch lead screws.

            Movement at the same speed as an 8 pitch lead screws requires faster stepper speed (4x) and it is rather noisy.

            But for normal Z speeds it's just fine.

            Frederick

            Printers: A FT-5 with the 713 upgrade bits. A custom MarkForged style. A small Utilmaker style and a CoreXY from kits. Various hotends. Using Duets (2 and 3) running 3.4.1

            1 Reply Last reply Reply Quote 1
            • dc42
              dc42 administrators @TheGov last edited by dc42

              @TheGov said in Duet 2: using:

              On the reprapforums someone adviced using a relay to short the 2 phases of a Nema stepper motor. I am just wondering how i should connect this to my Duet2 wifi board (i am aware this will void warranty). I was also informed the braking might not last long on a long and heavy Z axis (45 cm and +-5kg)
              Can anyone advice me how to connect this for a duet2 instead of a MKS board?

              You can do it in the same way for a Duet. You don't need the 4.7 ohm resistors, you can use the relays to short the windings.

              You can simplify the circuit by switching only one wire from each stepper motor phase, so you only need two SPDT relays (or one DPDT relay) per motor.

              To reduce the risk of damage to the drivers on the Duet, use the M918 M911 command to execute M18 when a power loss is detected, to turn the motors off. With luck the motor currents will have dropped to near zero by the time the relay changes over.

              Note, shorting the motors is unlikely to stop them turning, but it will slow them down.

              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

              oozeBot 1 Reply Last reply Reply Quote 1
              • TheGov
                TheGov last edited by TheGov

                Thank you everyone for the responses!

                @dc42 , Great forum and suppport you have going on here.

                I have the same relay as mentioned in the plan it's this one.
                https://www.aliexpress.com/item/32760607353.html?spm=a2g0s.9042311.0.0.27424c4dJsEquu

                I made a plan, could you be so kind to make some simple changes to the plan? i used MS paint.
                That would be very kind! I can see how to connect the motor part, i won't use any resistors like you mentioned but i am not sure how to connect the other side of the relay though

                Thanks in advance

                48bb6412-c971-4e2d-b7e7-b2f1cb580120-image.png

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

                  @dc42 said in Duet 2: using:

                  To reduce the risk of damage to the drivers on the Duet, use the M918 command to execute M18 when a power loss is detected, to turn the motors off.

                  David, can you elaborate on this? I've reviewed the M918 command and can't decipher how that can be used in connection with the M18?

                  Phaedrux 1 Reply Last reply Reply Quote 0
                  • Phaedrux
                    Phaedrux Moderator @oozeBot last edited by

                    @oozeBot I think he meant M911 for configuring what happens during power loss.

                    https://duet3d.dozuki.com/Wiki/Gcode#Section_M911_Configure_auto_save_on_loss_of_power That's where the M18 would go.

                    Z-Bot CoreXY Build | Thingiverse Profile

                    1 Reply Last reply Reply Quote 1
                    • TheGov
                      TheGov last edited by

                      Is there anyone who can help me with my previous post?
                      Help is very much appreciated, it is basically my last step before i can start testing my printer which has been in development for the last 3 years.

                      TheGov 1 Reply Last reply Reply Quote 0
                      • TheGov
                        TheGov @TheGov last edited by TheGov

                        I updated the drawing

                        Can someone confirm this is the way to go?
                        Thanks

                        duet2Relay.png

                        oozeBot 1 Reply Last reply Reply Quote 0
                        • oozeBot
                          oozeBot @TheGov last edited by oozeBot

                          @TheGov I’m not sure if anyone wants to take the liability of telling you, for sure, that’s correct.. However, I did find another photo you could use to compare it to..

                          Note- I only used two relays per stepper where you are using four..

                          BDB73459-6EFE-482F-A20F-4DDC864ABAF9.jpeg

                          1 Reply Last reply Reply Quote 0
                          • oozeBot
                            oozeBot last edited by

                            One more:

                            B8E5409B-D5FD-446F-B139-E70EF7041BAA.jpeg

                            TheGov 1 Reply Last reply Reply Quote 0
                            • TheGov
                              TheGov @oozeBot last edited by

                              @oozeBot

                              Thanks for the pictures.
                              Not really relevant for me i am afraid.

                              Today i connected the relay like seen below, Z motor not working.
                              Relay also does not seem to be turned on, no short on coils when power is turned off either.

                              duet2Relay.png

                              1 Reply Last reply Reply Quote 0
                              • DigiD
                                DigiD @TheGov last edited by

                                @TheGov

                                Have you considered using a simple mechanical brake ?

                                Below is what is essentially used on a large industrial cutting machine that has knives loaded on the z Axis . (its a cutter I have worked on)

                                During initialization of the cutting heads the cams turn counter clockwise releasing pressure on the solenoid that is powered by the DC power supply and it pulls out of the way . Z can now work in both directions . On any loss of power the solenoid drops out and catches the pawl in an 1/8th of a turn preventing the knives dropping into the table. Its a simple reliable system . Occasionally the solenoids fail , in 10 years over a 100 machines maybe 4 have been replaced. 3 burned out and 1 had some dirt /debris stopping it from engaging the pawl

                                701c3393-ac65-49db-a416-96bad0a51a14-image.png

                                TheGov 1 Reply Last reply Reply Quote 0
                                • TheGov
                                  TheGov @DigiD last edited by TheGov

                                  @DigiD

                                  Thx for the input, i actually have been think about this.
                                  I bought a small solenoid for this purpose but was not able to get it working, possibly i was/am not thinking of a good implementation.

                                  Solenoid.jpg

                                  This is how my Z axis is driven, my solenoid design was not able to hold the axis, which made sense as soon as i tried it. Maybe you have a different idea how to implement the solenoid?

                                  nema23.jpg

                                  TheGov DigiD 2 Replies Last reply Reply Quote 0
                                  • TheGov
                                    TheGov @TheGov last edited by TheGov

                                    I also want to state that i have spare duet (partly faulty) to do the testing on..
                                    Just would like to know what i'm doing wrong.

                                    1 Reply Last reply Reply Quote 0
                                    • DigiD
                                      DigiD @TheGov last edited by

                                      @TheGov

                                      If I had to design a brake for that Z axis I would mount the solenoid on that rail the motor is attached to and then have the Pawl on the left shaft . Design and print a Pawl cam and mate it to a GT2 20 or 30 tooth sprocket that has grub screws to fix it to the shaft and design and print an interference tooth for the end of the solenoid . Since its all plastic I would use surface areas as wide as possible . Its just a rough idea but I would attempt something like this

                                      46116c52-0113-4910-b33a-d41e0f45e34e-image.png

                                      those flanges for the GT pulley apparently are not that hard to take off and put back on again once that printed piece is fitted on

                                      1 Reply Last reply Reply Quote 0
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