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Stepper calculations and motor max speed

Discussion in 'General Talk' started by HPB, Jun 6, 2018.

  1. HPB

    HPB Well-Known
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    Hello, I wanted to make some calculations on the max speeds a motor can achieve and this is what I came up with. Can anyone verify if this is correct? For belt driven systems the machine speeds seems too high (bottom left of the image). Also how would I calculate the motor speed with the federate as a variable?

    [​IMG]
     
  2. DAVID C MCHENRY

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    Thanks for your calculations here.

    The lead screws have 4 starts but still the pitch is 8mm. That means 8mm of travel per revolution I think. Four starts but still 8mm per rev.

    In parts sales now Spec for the listed linear actuators with 8mm pitch screw drive says 5000mm/min.
    This is 83mm per second.
    But the screw would have to turn 10.37 rev per second (622 RPM) to do that.
    You calculate it at 8.93 REV / SEC
    I have not had much luck spinning stepper motors at those speeds without big torque loss.
    Anyway thanks for these calculations.
     
    Peter Van Der Walt likes this.
  3. Peter Van Der Walt

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

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    I'd say there are too many variables (friction, acceleration, static loads, dynamic loads) not taken into account just yet

    Experience based numbers puts our Leadscrew driven actuators around 5000-6000mm/min peak, for a CNC (gantry, router, etc loaded up) more reliably around 3000-4000mm/min
    Belt driven - 10,000 mm/min is a good sane "maximum" on the longer actuators - on the short ones (acceleration curve tuning/load dependant) you might not have enough space to run up to that
    (Running our standard Electronics packages on our standard machines and actuators)

    That's kind of our "safe" values, we do encourage customers to play with acceleration and max feed values to optimize their own Grbl parameters - but the base numbers are solid as a starting point

    See OpenBuilds-CONTROL/grbl-defaults.js at master · OpenBuilds/OpenBuilds-CONTROL for our standard machine profiles though - all conservative, but a good baseline
     
  4. DAVID C MCHENRY

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    Thanks for that.
     

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