Bed levelling using multiple independent Z motors



  • Hi. I want to use the capabilities of my Duet 2-Bad levelling using multiple independent Z motors. My z axis has 6 guide rails. The bed size is large (800*400mm). The instructions say: You should not use 4 leadscrews with a bad that is rigid enough to resist twisting strongly (https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors#main) I have 4 nezavisymykh motor are used for axis Z. As me do fastening, kotore not will too rigid and not will break under twisting bed?



  • In the three dimensional universe in which we find ourselves living, 3 points define a plane. Therefore, 3 motors on Z will work best of any possible setup.

    To answer the question "Will 4 motors break this bed or connection or whatever", we have to know a lot. The bed size, thickness and material. The way it is attached. The motors and the belts, pulleys, leadscrews, whatever. How far off level will it ever get. And many, many, more things.

    My advice:

    1. Use three. Then all questions go away.

    2. If you must use four, then ensure that the connections to the bed can pivot, and that they can separate (like a ball in a cup with a magnet or spring) and self-re-connect.



  • the reason for 3 point vs 4 points is described here
    https://drmrehorst.blogspot.com/2017/07/3-point-print-bed-leveling-vs-4-point.html

    if the bed is very rigid with 4 lead screws you have the potential to bend the bed.
    What you have to make sure is that the maximum adjustment (S parameter in M671) will not cause damage to your bed when its moving in the wrong direction.



  • 6 guide rails is asking for trouble. I can't imagine how you could possibly get and keep 6 rails parallel to each other. In theory, only two should be enough to prevent lateral motion. You might add another depending on how solidly the machine is built.


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