How do you calculate CP?

To calculate Cp, subtract the lower specification limit from the upper specification limit, then divide by six standard deviations.

What is a good CP value?

In general, the higher the Cpk, the better. A Cpk value less than 1.0 is considered poor and the process is not capable. A value between 1.0 and 1.33 is considered barely capable, and a value greater than 1.33 is considered capable. But, you should aim for a Cpk value of 2.00 or higher where possible.

What does a Cp of 1.33 mean?

Cpk = or >1.33 indicates that the process is capable and meets specification limits. Any value less than this may mean variation is too wide compared to the specification or the process average is away from the target.

What is Cp and Cpk definition?

Cp and Cpk, commonly referred to as process capability indices, are used to define the ability of a process to produce a product that meets requirements. In other words, they define what is expected from an item for it to be usable.

What is the formula for the C P index?

C p is governed by following formula: U S L = Upper Specification Limit. L S L = Lower Specification Limit. μ = estimated mean of the process. σ = estimated variability of the process, standard deviation. Higher the value of process capability index C p, better is the process.

What is the meaning of the CPK index?

Process Capability Index (Cpk) Definition: Process capability index (cpk) is the measure of process capability. It shows how closely a process is able to produce the output to its overall specifications.

What is the ratio of NT to CPK?

Traditionally, NT is 6 times the standard deviation. We often describe Cp as the capability the process could achieve if the process was perfectly centered between the specification limits. The equation for Cpk is more complicated: [minimum (mean – LSL, USL – mean)] / (0.5*NT).

Which is better process capability index C P or σ?

σ = estimated variability of the process, standard deviation. Higher the value of process capability index C p, better is the process. Consider the case of a car and its parking garage. garage size states the specification limits and car defines the process output.