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What should be considered to adjust/not adjust the SPC Control Limit?

Discussion in 'SPC - Statistical Process Control' started by Pongsakorn, Nov 27, 2019.

  1. Pongsakorn

    Pongsakorn Member

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    If we have to periodically re-calculate and review the Control Limit, what should be the criteria to consider to adjust/not adjust control limit.
    e.g.
    - If the new control limit is wider, the control limit should be adjusted or not?
    - If the new control limit is narrower but the new CL shift to be far from nominal spec more than the old CL, the control limit need to be adjusted or not?

    Anyone has an idea on this, please help to share or comment.
     
  2. Bev D

    Bev D Moderator Staff Member

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    Never adjust the limits to accommodate a degradation in variation.
    Only adjust the limits to a new level (average) or tighter limits when you took deliberate action to improve the process.
     
    G650ER likes this.

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