What is the Process Capability Index?

Cpk is a process capability index that determines how much a process can produce. Cpk, unlike Cp, does not assume the process mean is centered between the specified boundaries. Many people use Process Capability as a computation tool to estimate the output of a product they are manufacturing. It helps the manufacturers estimate the potential production and manage the resources to get the best results. The typical statistical analysis and distribution of data gathered are frequently used as inputs for the process capability index. It’s analogous to the mathematics terms mean and average value as well as standard deviation. However, it varies in that it employs a control chart analysis to assess the statistical control of the system.

The assumption that the measurements are regularly distributed is required by Cpk. 

Process Capability Index Formula

[Tex]Cpk=min \left (\frac{USL-mean}{3\sigma},\frac{mean-LSL}{3\sigma} \right) [/Tex]

where,

• σ is the standard deviation.
• upper specification limit = USL
• lower specification limit = LSL

Interpreting CpK Values

• If the Cp value is equal to the Cpk value, the process is functioning on the edge. The production capability is adequate and meets the design parameters for Six Sigma standards.
• The process means has violated one of the specification boundaries if Cpk is less than zero.
• When Cpk is larger than zero but less than one, the process mean is within specification limitations, but a portion of the manufacturing output has exceeded them.
• The process means is properly centered and within the specification limits if Cpk is bigger than one.

Process Capability Index (Cpk) Formula: Process Capability (Cp) is an approach for determining the quantifiable attribute of a process in relation to a specification. Process Capability Index is abbreviated as Cpk (Cpk). It assesses a manufacturer’s capacity to create a product within the tolerance range of a client. Cpk is used to determine how near you are to achieving a goal and how consistent your performance is compared to your average. Cpk calculates the best-case scenario for your current procedure.