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Project Lead/Ballscrew Max Speed Calculations 2016-10-16

figure out how fast you can spin it before you risk whip

  1. Julius

    Julius Veteran Builder

  2. MaryD

    MaryD OpenBuilds Team Staff Member Moderator Builder

    Thanks for posting this!
  3. evilc66

    evilc66 Master Builder

    If I have this straight, the safe RPM's for the different stock lengths of the C-Beam would be as follows:

    250mm - 426 rpm
    500mm - 106 rpm
    1000mm - 26 rpm

    (80% of critical speed)

    This is assuming the root diameter of the lead screw is 6mm, and the supported length of the screw is the same length as the extrusion. From what I found, root diameter is the overall diameter minus the pitch

    According to this calculator, the OB steppers max out at the following:

    Nema 17:
    12v @ 1.68A - 382 rpm (3056mm/m, 120.3ipm)
    24v @ 1.68A - 768 rpm (6144mm/m, 241.9ipm)

    Nema 23:
    12v @ 2A - 300 rpm (2400mm/m, 94.5ipm)
    24v @ 2A - 600 rpm (4800mm/m, 189ipm)

    12v @ 2.8A - 214.2 rpm (1713.6mm/m, 67.5ipm)
    24v @ 2.8A - 428.4 rpm (3427.2mm/m, 134.9ipm)

    Nema 23 High Torque:
    12v @ 2A - 225 rpm (1800mm/m, 70.9ipm)
    24v @ 2A - 450rpm (3600mm/m, 141.7ipm)

    12v @ 3A - 150 rpm (1200mm/m, 47.2ipm)
    24v @ 3A - 300 rpm (2400mm/m, 94.5ipm)

    EDIT: Added mm/m and ipm travel speeds, assuming OB TR8*8-2 lead screw.
    Last edited: Oct 19, 2016
  4. Julius

    Julius Veteran Builder

    Yes. That's why i don't like the idea of 5mm acme for over 250. I can bend it with my finger in the Z axis...

    I have 16mm ballscrews. With 48V they become the limit, at 300ipm. I'm ok with that! Currently at a max of 170 before the motors lose their torque.

    For my 1500mm machine next year i will have to use 2010 screws
  5. evilc66

    evilc66 Master Builder

    Added mm/m and ipm travel speeds to my post.

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