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  1. #31
    Ran some more math on my triple beam "L" gantry. With a little less simplification. Generally don't see any major problem. I think it is time to add the final details to the design and then start building the thing.

    Using Fusion 360 now and its static FEA solver. Not sure I will stick with this although the integration with industrial design capabilities looks pretty cool.


    Click image for larger version. 

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    John C

  2. #32
    Fwiw..

    My large cnc mill bed is 240 kg in mass, for the bed alone, and up to 100 kg of vice and workpiece, easily.
    So 340 kg++ of mass.

    Worked fine with one small nema 23 stepper of 3Nm.
    48V, 2M542 drive.
    1:3 HTD belt drives.

    Heavy is better, not worse.

    For non-commercial use the speed was never a concern.
    I never needed higher speeds.
    Always wanted more mass, more rigidity, more resolution ...
    leading to better accuracy.

  3. #33
    hanermo2, I have some 2.8 Nm NEMA 23 low inductance steppers and some 60 volt PS and drivers so I will try that with this rig. Will mount the steppers off belts rather than the direct drive I previously planned. Sigh, back to the CAD.

    John C

  4. #34
    Quote Originally Posted by jcarpenter View Post
    hanermo2, I have some 2.8 Nm NEMA 23 low inductance steppers and some 60 volt PS and drivers so I will try that with this rig. Will mount the steppers off belts rather than the direct drive I previously planned. Sigh, back to the CAD.

    John C
    My previous machine ran off something similar to that spec with 5mm screws (you mentioned these in an earlier post) and it was direct drive. All worked fine.
    But if you want better speeds for wood then belt drive allows 1:2, also reduces resonance effects in the stepper and most important of all(!) allows the motor to be tucked away.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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