Dual Z screw not working right with DueX5 end stop



  • I have my idex configured to use all axis through A for main axes motion and I was using Z and B configured on external drivers 10 and 11. The problem 11 - > B is not always homing right sometimes it homes correctly and hits the limit switch on that side, sometimes it keeps moving through the end stop.

    Just to troubleshoot and ruleout wiring issues etc, I switched my 2nd Y axis – which was mapped to U with B and moved the end switches accordingly, and now Z is still 10 and 11, but for homing I configure 10 to Z and 11 to U now, and homing works. Homing for my 2nd Y axis works with B as well, but that means I can't hide the extra axis with P parameter. It seems there is a bug with dual lead screw homing combining end switch on the main board and the Duex5.
    David, you fixed the homing on the Duex5 for other axis, but it seems not to work right with dual lead screw config


  • administrators

    As I understand it, the endstop input that is unreliable is endstop 11 on the CONN_LCD connector. At present you will need to add an external pullup resistor between this endstop input and +3.3V for it to work reliably, or use a 3-wire endstop switch. Same to endstop 10. In firmware 1.20 (first beta due out today or tomorrow) I'll enable the internal pullup resistors on those inputs.

    Have you considered using a single Z endstop switch and leveling the two motors using the Z probe?



  • @dc42:

    As I understand it, the endstop input that is unreliable is endstop 11 on the CONN_LCD connector. At present you will need to add an external pullup resistor between this endstop input and +3.3V for it to work reliably, or use a 3-wire endstop switch. Same to endstop 10. In firmware 1.20 (first beta due out today or tomorrow) I'll enable the internal pullup resistors on those inputs.

    Have you considered using a single Z endstop switch and leveling the two motors using the Z probe?

    I'm using axis B which maps to the 7th end stop on the DueEx5, that's the one that is not working when used mapped to drive 11. I only need 7 end stops. It works fine when mapped to an independent axis – that is 2nd Y axis. Basically flip-flopping endstop 4 and 7 solved my mechanical issue -- only difference is endstop 4 is on the main board, and 7 is on Duex5

    I'm presently still building, and I will switch to z-probe, but I need to build that into the machine -- I have the piezo board, and I'm working on designs to incorporate piezos, but for now I am able to fully level the bed manually, so it's not a priority.
    Also the bed is heavy, very heavy -- the point for 2 lead screws is to support the weight of the bed, when power is removed, it drops down, not evenly, so using a single z end stop is not practical since the starting point is not known, at least with 2 -- I can get the 2 lead screws sync'ed up when homing.



  • David, what I'm seeing is that limit switch 7 can't be combined with limit switch 2 – essentially the stepper assigned to axis B keeps moving through the switch. This doesn't always happen, sometimes it works correctly. I would like axis B to used as the 2nd Z axis since it's the last axis and I can use P7 parameter and hide it from the UI, but this means I can't. By simply moving the 2nd Z axis limit switch to the 4th one on the main board, and using the 7th end switch for homing my 2nd Y axis, everything works fine, but now U axis is the 2nd Z axis, and B is now used for the 2nd Y axis, so I can't hide U, it is present in the UI. Basically it seems that limit switches on the Duex5 can't be used together with those on the Duet for Dual Z lead screws.


  • administrators

    Try using a lower Z homing speed, or lower Z microstepping if you are using greater than x16.



  • I'm using external Z drivers at 16 microstepping. Homing slowly doesn't help. I just switched to using limit switches on the Duet for Z, my other axis home fine using limit switches on the Duex5. It still seems that the Duex5 limit switches are not as fully featured. Ideally would it be possible to assign a limit switch to a letter – basically 0->X, 1->Y, 2->Z, 3->B, 4->U etc, then the letter wouldn't matter as much and the location of the limit switch would also be secondary, because I have no way of saying B axis should use a different limit switch except #7 on the Duex5


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