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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 Well-Known
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    #1 Julius, Oct 16, 2016
  2. MaryD

    MaryD OpenBuilds Team

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    Thanks for posting this!
     
    #2 MaryD, Oct 17, 2016
  3. evilc66

    evilc66 Journeyman
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    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.
     
    #3 evilc66, Oct 19, 2016
    Last edited: Oct 19, 2016
  4. Julius

    Julius Well-Known
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    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
     
    #4 Julius, Oct 19, 2016
  5. evilc66

    evilc66 Journeyman
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    Added mm/m and ipm travel speeds to my post.
     
    #5 evilc66, Oct 19, 2016
  6. Rafael Romero

    Rafael Romero New
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    I know this is an old thread but I found it important.

    So, the RPM calculated by evilc66 are at 80% safety factor using Rigid/Free combination with 8mm lead screws.

    In my case, I ordered the Workbee 1010. It looks like it is Simple/Simple configuration

    At approx 20% from critical i should be safe from whip at about 300 rpm ... is this correct? I have not yet received it so Im not 100% sure of what support arrangements the unit has.

    Kind regards,

    Rafael
     
    #6 Rafael Romero, Jun 11, 2019
  7. kambo

    kambo New
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    #7 kambo, Jul 20, 2020
  8. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

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    #8 Peter Van Der Walt, Jul 20, 2020
  9. kambo

    kambo New
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    Thank you so much Peter, i always forget this wayback machine :)
     
    #9 kambo, Jul 20, 2020

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