planning for 16 stepper motors..



  • Hello, We are building a large cartesian 3d printer and are hoping to drive 16 stepper motors.

    2 for the X axis, 4 for the Y axis, 4 for the Z axis
    and 6 for extruders

    We plan on using 12 nema-17 stepper motors for the X and Y axes as well as the extruders and 4 nema-23 stepper motors for the Z axis

    Upon studying the forum and the documentation, we are planning to use the duet2 wifi, the duex5 and the 2 additional motor signals sets on the CONN_LCD.. however this only nets us 12 independent channels of control.

    on the Duet2:
    We're planning to run the 2 X axis motors off the 2 Z headers on the Deut2.
    We also plan to run the 4 Y axis motors on the remaining 4 motor headers on the Duet2

    on the Deux5:
    We're planning on running 5 of the extruder stepper motors on the Duex5

    on the CONN_LCD:
    We plan to run the 6th extruder off of the signals for E10 on the CONN_LCD (Stp10, Dir10, En10, and Stop10)

    Is there a way of driving multiple motor controllers with one set of control signals so they run in parallel?

    For example could we run our 4 nema-23s on the Z axis via 4 separate motor controllers working off the same signals from E11 on the CONN_LCD (Stp11, Dir11, En11, and Stop11) ? If we can are there drawbacks to running them off of the same signals?

    We were curious if anyone has tried to use a second Deux5 custom wired to the CONN_LCD connector to get 5 more controllers?

    Finally, we saw talk in the forums about a new version in the works that supported additional motors.. Is there a timeline for this new version yet? Are there opportunities to beta test it before its released?

    Thanks for any help!

    Michael 23


  • administrators

    There are a few possibilities;

    1. Depending on what speed and torque you need, you may be able to connect two stepper motors in series (which is how the two Z motor connectors are wired) or in parallel, if you don't need to control them independently. Using 24V power instead of 12V helps. Use the motor calculator at reprapfirmware.org to see if this will work well with your chosen motors.

    2. If you are using any external stepper drivers, you can connect motors in parallel to the external driver outputs if they have high enough output current capacity.

    3. Also if you are using external stepper drivers, you can connect stepper driver inputs in parallel.

    4. The above methods don't allow independent control of the motors that are driven from a single driver channel. To get independent control of more than 4 motors, you could modify the firmware to reallocate some of the pins on the expansion bus to drive additional stepper drivers. Somebody already did this to drive 14 motors independently.

    The advantage of allowing independent control of each Z motor is that you can use them to to bed levelling. See https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors.

    For the future, the Duet 3 as currently prototyped provides 6 stepper drivers on the main board, then you can daisy chain expansion boards that carry 3 drivers each. So the main board plus 4 expansion boards would provide 18 stepper drivers. Or the main board plus 3 expansion boards would provide 15, and you could use the dual outputs on the main board to connect the extra motor.


 

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