What Is A Good CPK And PPK?

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..

Should I use CPK or PPK?

Another way to look at the difference is that Cpk is used for a subgroup of data, while Ppk is used for the whole process. Cpk is typically used while processing in the ideal conditions to identify if the process is capable of meeting the specifications.

How is PPK calculated?

Process Mean close to USL If your Process Mean (central tendency) is closer to the USL, use: Ppk = [ USL – x(bar) ] / 3 s, where x(bar) is the Process Mean.

What is minimum Cpk value?

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. An estimate for Cpk = Cp(1-k).

What is a good CPK and PPK value?

According to Six Sigma philosophy, Cp or Pp and Cpk or Ppk should be greater than 1.50. From a technical standpoint, Six Sigma deems a process being acceptable only after achieving a maximum defect rate of 3.4 parts per million opportunities.

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)

What does a PPK of 1.0 mean?

Capability indicesPpk is an index of process performance which tells how well a system is meeting specifications . If Ppk is 1.0, the system is producing 99.73% of its output within specifications. … The larger the Ppk, the less the variation between process output and specifications.

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.

What if CPK is less than 1?

By convention, when the Cpk is less than one, the process is referred to as incapable. When the Cpk is greater than or equal to one, the process is considered capable of producing a product within specification limits. In a Six Sigma process, the Cpk equals 2.0.

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 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 PPK value?

For stable processes and normally distributed data, a Cpk value ≥ 1.33 should be achieved. For chronically unstable processes with output meeting specification and a predictable pattern, a Ppk value ≥ 1.67 should be achieved.”

What does CPK and PPK stand for?

Sorry to tell, but definition of Cpk and Ppk is wrong, it´s just the other way round: Ppk is a short term analysis (mostly done with 50 or 100 samples measured) Ppk is Process Potential Capability. Cpk is long term analysis and is Continous Process capability.

How many Sigma is 1.67 Cpk?

Sigma level tableTwo sided tableCpk PpkSigma levelPPM out of tolerance1.334.063.3421.504.56.7951.675.00.5738 more rows

Why is PPK higher than CPK?

theoretically Ppk can’t be greater than Cpk. However, it is possible to get Ppk larger than Cpk due to measurement problems (poor resolution or chunky data particularly if you use the Range to estimate the standard deviations) and if you have almost no between subgroup variation…