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  • Lifting mechanism and effect of gearbox on stepper motor accuracy

    Discussion in 'The main mechanical design forum' started by akshay23, Jun 4, 2013.

    1. akshay23

      akshay23 New Member

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      i am working on project in which i need to place hydrophones in a 2mX2mX1m water tank at exact x,y, z coordinates

      for the x and y movements i have a traverse guiding rail (for y movement) which sits on a sort of vehicles on wheels (for x movement). these are driven by stepper motors.

      i now need a lifting mechanism to be put on the vehicle for lifting a load of around 3 kgs vertically

      1. Can a rack and pinion mechanism be used for vertical lifting? (the pinion will be fixed above water and rack will move vertically carrying with it the hydrophones).

      2. Also if a mount my (0.9 Nm holding torque) stepper motor on to a 3:1 gearbox will i still be able to accurately control the position of the vertical dimension? (precision in order of mm required)

      3. And what other lifting mechanisms can be used in which the motor stays out of water?
      (keeping in mind that noise should be minimum)
       
      Last edited: Jun 4, 2013
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    3. Mark Stapleton

      Mark Stapleton Active Member

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      Have you considered a trapezoidal thread (as in "Acme") screw jack or a rolling ring gearbox for your Z motion? See Duff Norton or Helix/Nook if not.
       
    4. Dana

      Dana Well-Known Member

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      Your achievable accuracy will be the sum of the stepper motor error plus the error and backlash of any gearing. Depending on the arrangement, backlash may not be an issue in the vertical axis as the weight is always pulling in the same direction.

      For any linear motion, a rack and pinion is one choice; a lead screw is another. Depending on the pitch of the lead screw, it may or may not be self locking. You can get stainless lead screws with plastic nuts for underwater use in a wide range of diameters and pitches. Another option is a timing belt with the load clamped to the belt at one point for linear motion.
       

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