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  1. #11
    How big a packet of Hob Nobs?

    The Proxxon is limited to about 160mm by 40mm movement in X and Y. As the 1Nm steppers are only driven by 13.5V it could probably be sped up a bit, but a typical job might be a 25mm dia brass gear, or maybe a 80mm by 30mm PCB.

  2. #12
    Quote Originally Posted by leadinglights View Post
    2000mm/min sounds like the speed of sound to me
    That would be over 6rps on my lead screw handles

    I can ramp it up to incredibe speeds but start to get uneasy at around 3rps.

    Guess I'm not very brave :whistling:

  3. #13
    I have just been playing with the numbers on toothed belt drives and stepper motors but I don't know if the answer I have come up with are right.
    Using the formulae given in the Transdev datasheet for Syncroflex toothed belt drives, I get a figure for tooth shear strength when using a 10mm wide belt and pulleys of 16T and 40T, 6 teeth engaged, of just a tad under 200 Newtons at the stepper motor. The Tension Member is not much better at about 300 Newtons.
    Although I haven't settled on a stepper motor yet, the most likely candidate, the so-called 3Nm NEMA 23s that are available at the moment, put out about 2Nm at stall - about 160 newtons at the periphery of a 16 tooth pulley.
    Is toothed belt really that wimpy, or have I lost a decimal place somewhere?

    Hmm, a quick edit here. Looking at the datasheet for Zapps SY60STH88-3008BF, the maximum radial load is given as 75 Newtons. I assume that if you are applying a torque of 2Nm at a 12.5mm radius then you will get something like 160 Newtons of radial force reacting to it. I may have to think a bit more about the motors as well.
    Last edited by leadinglights; 05-05-2010 at 08:39 PM.

  4. #14

    2Nm torque, 5:2 reduction, 5mm pitch screw gives a driving force of 0.63 tons.

    Probably best if the belt fails before something else does :naughty:


    How to calculate it...
    ! rev = 5/2.5 = 2mm
    2mm/(2*pi)= 0.3183mm = 0.0003183m torque radius
    2Nm/0.0003183m = 6283N = 0.63 tons

  5. #15
    Hmm, I had better apply myself to Irving's tudorial and motor calcs program. I had avoided that until I get some idea of the masses that I will be throwing around.
    (Also, avoid getting finger trapped between table and frame at 0.63 tons)

  6. #16

    So 6283 Newtons would accelerate a mass of 18.5kg to Mach 1 in approx 1 second.

    Robin :heehee:

  7. #17
    But I will be using Mach3, does that take 3 seconds?

  8. 1.85638543287408 Hob Nobs [approx]

    John S -

  9. #19
    Quote Originally Posted by leadinglights View Post
    But I will be using Mach3, does that take 3 seconds?

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