Some concepts about DIN 5480 spline dimension Part 3

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In this tutorial, I will explain the concept of addendum correction (modification) and how is applied to DIN 5480 splines

  1. Step 1: Principle of corrections (modifications)

    Approaching and withdrawal of the production tool from the gear center changes the shapes and therefore also properties of the involute toothing. This creates corrected toothing.

    The values of modification are based on the use of a hob or rack-type cutter and as a result, are more than adequate for gears cut with circular, shaper-type cutters. See the figure below .

    A: Production tool

    B: Produced gear




     

  2. Step 2: Why correct the addendum?

    The values of addendum modification enable:

    • Increase loading capacity of the gearing 
    • Achieve the exact axis distance.
    • Improve the contact ratio (achieve a contact ratio >1)
    • Eliminate sharpness of teeth

    Additionally if gear moves

    • Prevent undercutting of teeth (roots of a small number of teeth might be undercut; this decreases the coefficient of duration of the meshing and reduces the loading capacity of the teeth)
    • Prevent the creation of production and operational interference of teeth
    • Reduce noise and vibrations of the gearing
    • Improve efficiency

    In DIN 5480, this correction is prescribed, as an example for a shaft W52x2x24x8h, addendum modification can be seen in the table below.



  3. Step 3: What changes with gear modification?

     The correction of the addendum modifies the shape and strength as can be seen in the picture below.



  4. Step 4: Values of correction

    x1xm is the distance from the Standard pitch circle of the gear to the Standard pitch line of the cutter. (Figure b) If the correction is equal to zero, the Standard pitch line of cutter and Standard pitch circle of the gear are tangent. (Figure a)



     

  5. Step 5: Indication of modification in DIN 5480



     

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