Cp&Cpk

Cp or Cpk stands for process capability index.

it means in a specific period, what's the capability of the process to produce products at a stable ,controable level.

operator ,machinery , materials,envrionment and technology this five main factors effect the process consistently, and the final production is effected by this five major factors.

during the production process, variation always exists. Cp compares the process spread to the width of the tolerances, tolertances should be at least as wide as the process is or more wider.

but Cp is not enough, may the tolerance of two process is same but one of them not lacated into the limits, Cpk is needed.

it measures the likehood of producing non-conforming product of the process. Cp compares the distance from the process centre to either tolerance, Cpk measurs the distance from top/bottom to the centre.

the process best situation is that Cp equals to Cpk. Cpk will never exceed Cp.Cpk can be negative if centre is outside of the control limits.

: 30 Nov 2010 21:25 |  Tags: Piuss |  Comments (0) |  Report a problem