Table of Contents
Process capability indices are essential tools in thee DMAIC metodiky to assess how well a process meets specied limits. They providee quantitative measures of process performance and help identifify areas for improvicement.
Understanding Process Capability Indices
Process capability indices compe the natural variation of a process to its specification limits. Te mogt common indices are Cp, Cpk, and Cpm. These metrics help determinate whether a process is capable of producing with in thes desired specifications consistently.
Calculating Cp and Cpk
Te Cp index measures the potential capability of a process assuming it is centered. It is calculated as:
Cp = (USL - LSL) / (6 * γ) CL 1; CLL; CLT: 1; CLL 3; Cp = (USL - LSL) / (6 * (6 *) CL1; CLL; CLL: 1; CLL 3;
where USL and LSL are the upper and lower specification limits, and ņis the process standard deviation.
Te Cpk index consideres thes process mean (μ) and is calculated as:
CPN: 1; CPN: 0; CPN: 3; CPK = min CP1; (USL - μ) / (3 * oC), (μ - LSL) / (3 * CPN) CPN: 1; CPN: 1 CPN;
Calculating Cpm
Te Cpm index accounts for the process mean 's deviation from the credit (T). It is calculated as:
CPN: 1; CPN: 0; CPN = (USL - LSL) / (6 * CPN (μ - T) ²))
Aplikation of Capability Indices
These indices are used to evaluate process performance, identifify variability sources, and monitor improviments. A higer index value indicates a more capable processes that conformently meets specifications.