Question: What Is A Good CP CPK Value?

What is CP CPK?

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.

Specifications are normally defined in terms of nominal (+/-) tolerances or ranges (low to high..

What is a good CP value?

By convention, when a process has a Cp value less than 1.0, it is considered potentially incapable of meeting specification requirements. Conversely, when a process Cp is greater than or equal to 1.0, the process has the potential of being capable. Ideally, the Cp should be as high as possible.

What does a Cpk of 1.67 mean?

The Capability Index, Cpk. The outcome of a Process Capability study is a single metric, which provides an indication of the ability of a process to consistently provide output which is within required specifications. CPK <1.00 (Poor, incapable) 1.00< CPK <1.67 (Fair) CPK >1.67 (Excellent, Capable)

How many ppm is 1.33 Cpk?

Sigma level tableTwo sided tableCpk PpkSigma levelPPM out of tolerance1.173.5465.2581.334.063.3421.504.56.7958 more rows

What does CPK stand for?

Creatine phosphokinaseCreatine phosphokinase (CPK) is an enzyme in the body. It is found mainly in the heart, brain, and skeletal muscle.

Can CPK be negative?

Yes, it is possible for Cpk and Ppk to be negative. … It is impossible to have a standard deviation be negative so that would mean that x(bar) was larger that the Specification Limit. In other words, the process average is out of specification.

What does a Cpk 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 does a Cp of 1.5 mean?

A Cp of less than one indicates that the process spread is greater than the specification. This means that some of the data lies outside the specification. … So a Cp of 1.5 means the process can fit inside the specification 1.5 times. A Cp greater than one is obviously desirable.

What does a Cpk of 2 mean?

When Cpk is negative it means that a process will produce output that is outside the customer specification limits. … Cpk can have an upper and lower value reported. If the upper value is 2 and the lower is 1, we say it has been shifted to the left.

What does a Cpk of 0 mean?

Cpk of 0 would only be possible if the process was run exactly on either the upper or lower spec. limit. This would assume there was no variation in the process what so ever.

What is the value of CP and CPK in SPC?

The mean (38.667) is closer to one of them than to the other, leading to a Cpk factor (0.17) that is lower than the Cp value (0.22). This implies that the LSL is more difficult to achieve than the USL. Non-conformities exist at both ends of the histogram.

What is the CPK for 3 sigma?

Relationship to measures of process falloutCpAdjusted Sigma level (σ)Process yield1.00393.32%1.33499.38%1.67599.9767%2.00699.99966%2 more rows

How many Sigma is 1.67 Cpk?

6 sigmaCp = Cpk = 1.67. The sigma level is now 5 – the specifications are five standard deviations away from the average. The out of specification has decreased to 0.57 ppm. The fourth curve represents that magical 6 sigma level.

What is a good CPK?

The higher the Cpk, the better is the capability of the process to meet its requirements. In the industry, a Cpk of less than 1.66 needs a closer look. A Cpk that’s less than 1.33 needs some action to make it higher, and a Cpk of less than 1.0 means that the process is not capable of meeting its requirements.

What is the minimum acceptable value for CP?

A value of less than 1 is unacceptable, with values greater than 1.33 (1.25 for one-sided specification limits) widely accepted as the minimum acceptable value, and values greater than 1.50 (1.45 for one-sided specification limits) for critical parameters (Montgomery, 2012) .

What is the maximum value of CP and CPK?

The minimum value of “k” is 0 and the maximum is 1.0. A perfectly centered process will have Cp = Cpk. Both Cpk and Ppk relate the standard deviation and centering of the process about the midpoint to the allowable tolerance specifications.