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IndustryArena Forum > Mechanical Engineering > Mechanical Calculations/Engineering Design > Calculation Of Force In Order To Select Correct Spring
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  1. #1
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    Jan 2007
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    35

    Question Calculation Of Force In Order To Select Correct Spring

    I need to decide on which compression spring to use in one of the assemblies I am working on. In order to do so, however, I need to calculate the force which will be applied to the springs in Newtons.

    The assembly consists of two shafts each driven by a siemens stepper motor. The shafts are offset and in turn drive two plates in a linear direction towards each other, resulting in a clamping force being applied between the two plates.

    I need to calculate the resultant clamping force between these two plates.

    Any guidelines would be appreciated.
    Thanks

  2. #2
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    Dec 2005
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    3319
    Not enough information provided to calculate the answer.

    However, it would seem that you're trying to essentially make a screw type "vise" via stepper motor operation of the screw handle.

    If that is the case, get hold of a machine design book and look into bolt clamping discussions. Essentially, the clamping of a bolt is the same sort of load application that you're trying to affect.

    A helpful formula involves;

    deflection = (P*L)/(A*E)

    Where:

    Deflection = the length change of a stretched bolt
    P = tensile force in the bolt
    L = Length of bolt in tension
    A = cross sectional area of the bolt
    E = material modulus.

    How does a bolt torque figure in? Simple. once you know the thread pitch, once the clearance is taken up, any more turns of the nut stretches the bolt.

    Once you know/establish 4 of the variables, you then calculate the 5th. If there are any "I don't knows" in there, problem is unsolveable via calculative means and they you SWAG.

    Now that you have figured out the force scientifically, you then use Hooke's law (and some coil or leaf spring forulae) to calculate a spring's geometry that will provide an equivalent force within the available space.

    This is the "how to" part of the process - the rest of the effort is a pure and simple machine design problem solving episode.

  3. #3
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    Aug 2011
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    Hi there, im one of a Jig and Fixture Designer. Can anyone please help how to calculate a force for a Clamping Jig? If we wanted to clamp a stock in a jig, how do we calculate the force? Looking forward for ya' all reply. Good day....

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