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Help Capstan driven z axis

  1. Aug 29, 2014 #1
    Hello guys I am working on a z axis lift driven by stepper to lift and lower the platform precisely . It will be driven by a capstan drum fixed to stepper shaft and cable routing around pulleys . I have a stepper nema23 with 1n-m holding torque . As per my calculation toque required By motor to lift the stage would be FXR since I am looking to design the stage for max payload of 10 kg I assume the motor torque is sufficient but as we know the efficiency of motor is actually less assuming 80% available torque would that be enough since I am running cables through capstan drum with 2-4 wraps and around pulleys will I be having some mechanical advantage so that my motor is capable with available torque? If yes will that be sufficient enough to hold the stage if there is a power failure without slipping I am routing cables similar to this diagram http://www.google.com/patents/US5273352 I also thought of increasing torque with torque amplifier design http://en.m.wikipedia.org/wiki/Torque_amplifier is this feasible enough . Waiting for valuable suggestions
  2. jcsd
  3. Aug 30, 2014 #2
  4. Aug 30, 2014 #3


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    Science Advisor

    Welcome to PF.

    How fast will it be required to travel?
    How often will it change direction?

    If slow then counterbalance with mass.
    If fast then counterbalance with a spring.
  5. Aug 31, 2014 #4
    Hi the height is 2feet it's a bed for a combo mill and 3d printer it will be slow a slow speed since it will driven by stepper to lower precisely I thought of counterbalancing the stage but I have a space constraints that's why I thought of going with a torque amplifier route will this work ?
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