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amilapsn

  • one year ago

A punching machine has to carry out piercing operations at the rate of 12 holes per minute. The amount of work to be done in cutting 30mm diameter holes in 15mm thick plate is 8J/mm2 of the sheared area. The actual piercing operation takes 2s. The total frictional losses over a cycle are equivalent to one sixth of the work done during a single piercing operation. The machine shaft is driven by a constant power electric motor. The maximum fluctuation of the speed of the machine shaft is between 190 rev/min and 210 rev/min. (a) Find the minimum required motor power to drive the piercing machine

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  1. amilapsn
    • one year ago
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    (b) Determine the required sum of the mass moments of inertia of all revolving parts on the machine shaft in order to keep the speed fluctuation within the given limits. State any assumption made.

  2. amilapsn
    • one year ago
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    @ganeshie8

  3. amilapsn
    • one year ago
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    @dan815

  4. dan815
    • one year ago
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    :)

  5. amilapsn
    • one year ago
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    I've got some problems to sort out regarding this problem @dan815

  6. dan815
    • one year ago
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    okay what seems to be the problem

  7. amilapsn
    • one year ago
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    During a piercing operation the shear area would be \(\pi r^2\) or \(s2\pi r h\) where r is the diameter of the hole while h is the depth...

  8. amilapsn
    • one year ago
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    *\(2\pi rh\)

  9. dan815
    • one year ago
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    why 2*pirh

  10. amilapsn
    • one year ago
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    Then why the depth is given?

  11. dan815
    • one year ago
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    not sure why, i dont think we need it

  12. dan815
    • one year ago
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    it gives work per surface area though in mm^2 so

  13. amilapsn
    • one year ago
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    Work done per hole = 8 x pi x r^2?

  14. amilapsn
    • one year ago
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    Then another q:

  15. dan815
    • one year ago
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    yep

  16. amilapsn
    • one year ago
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    Am I right: minimum power to drive the piercing machine=maximum power in a cycle

  17. amilapsn
    • one year ago
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    |dw:1433649727575:dw|

  18. dan815
    • one year ago
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    yeah

  19. amilapsn
    • one year ago
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    But in a text book they've taken the average as the minimum required power...

  20. IrishBoy123
    • one year ago
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    you need the thickness in shear area Ex 5 on page 10: http://www.freestudy.co.uk/mech%20prin%20h2/stress.pdf

  21. amilapsn
    • one year ago
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    Thank you so much! @IrishBoy123

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