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Does a Belt drive actuator isolate motor vibration?

  1. Oct 4, 2016 #1
    Trying to build a case for a belt driven ball screw axis versus a Planetary gear box, with the fact that the motor vibration would carry down the gearbox to the axis, but the timing belt drive would isolate the motor vibration. How would I model this? and ideally a way to get a factor of difference of performance.

    if the belt does act like a spring, how would I figure out its stiffness?

    Any help appreciated.

    Thank you.
     
  2. jcsd
  3. Oct 4, 2016 #2
    First of all. Why is motor vibration a problem? What is the nature of the vibration?

    By what mechanism do you think the belt provides isolation?
     
  4. Oct 4, 2016 #3
    Well from what i've read is that sometimes motor rotors can be out of balance, which at higher RPMs would cause the motor housing to shake and consequently the bracket holding the motor. Now usually this is negligible, however for some precision applications, this has a potential to affect the tool accuracy. And in terms of the belt isolating the vibration, I assume that the timing belt has some stretch to it, and also some elasticity, I was hoping this would act as a damper & spring, therefore reducing the vibration that would transfer to the ball screw, that might otherwise be transferred over through a rigid coupling.
     
  5. Oct 4, 2016 #4
    It probably would provide better isolation, and avoid the tooth-meshing vibration and noise of a gear box. However a timing belt (Gilmer belt, or toothed belt) adds its own vibration, shown up as a speed variation, as the belt teeth interact with the pulley teeth. If you are using it for adjusting a static position, depending on the particular application, that probably won't matter. (Ahh, just re-read the question and noted the 'ball screw axis'. Sounds like this applies, and belts are cheaper than gear trains.)

    On the other hand, if you are trying to move a credit card thru a card reader, then you better use a flat belt.

    If you don't need continuous rotation, a cable drive works well.
     
  6. Oct 5, 2016 #5
    Isolation of a mass spring systems only occur when the secondary mass is operating at frequencies above the mode (and therefore out of phase). Ie it's operating some region above the modal frequency. If the machine is OOB, and precision is needed, the answer would be to balance it. Always try to eliminate NVH issues at source.

    https://goo.gl/images/DzdyK7

    Belts can actually be rather stiff in tension, if they were overly stretchy they wouldn't transmit power. As you are adding a stiff spring, you are adding a mode to the system. If you are particularly unlucky that critical speed will cause amplification right where you don't want it to.

    IT's difficult to comment as everything like this is so application specific.
     
  7. Oct 5, 2016 #6
    That's an excellent point, that if the belt is rigid enough, it could act as a source of vibration. I never considered that.
     
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