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Identifying tolerances for capability analysis

Discussion in 'Capability - Process, Machine, Gage …' started by venkat, Jul 13, 2017.

  1. venkat

    venkat New Member

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    Hi,

    How do to select USL and LSL limits?

    For example,

    I have observation results of 30 Re is 3.43, 3.27 ,3.19, 3.17,3.17, 3.19, 3.19, 3.24, 3.1, 3.12 ,3.25, 3.2, 3.35, 3.2, 3.2, 3.22, 3.23, 3.18, 3.19, 3.31, 3.18, 3.08, 3.18, 3.17, 3.23, 3.19, 3.25, 3.26, 3.23, 3.18

    mean = 3.2117, STD = 0.07

    Company datasheet provided for Re is 3.08 and production tolerances +/- is 7.50%

    ——–

    to find Cpk how do I calculate USL and LSL values?
     
  2. Miner

    Miner Moderator Staff Member

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    USL = 3.08 + 0.075 * 3.08 = 3.31
    LSL = 3.08 - 0.075 * 3.08 = 2.85

    Point of caution regarding your data. If it is in time sequence, the first data point is out of control. If not in time sequence, the first data point is an outlier. Either way, you should investigate the cause before proceeding further.
     
    Last edited: Jul 13, 2017

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