What Is An Acceptable PPK Value?

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 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 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 is a good PPK?

The larger the Ppk, the less the variation between process output and specifications. If Ppk is between 0 and 1.0, not all process output meets specifications. If the system is centered on its target value, Ppk should be used in conjunction with the Pp index.

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.

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…

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.

How is PPK value 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 does a Cpk of 1.0 mean?

Process Capability IndexDefinition: Cpk = Cpk = Process Capability Index. … 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 does PPK stand for?

PPKAcronymDefinitionPPKPunt, Pass, and Kick (NFL youth program)PPKProfessional Protection KitPPKPalm Portable KeyboardPPKPublic Private Key16 more rows

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

What is PP and PPK value?

Pp and Ppk It measures how well the data might fit between the spec limits (USL, LSL). It doesn’t care if the process is centered within the limits only if it would fit if it was centered. Ppk is the performance centering index. It measures how well the data is centered between the spec limits.

Is PPK short term capability?

Cpk is sometimes referred to as the short-term capability. With Ppk, the calculated standard deviation is used. This includes all the data at one time in the calculation. Ppk is sometimes called the long-term capability.

What does CPK 1.67 mean?

Excellent, CapableThe 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)