Question: What Should PPK Be?

What is a good PPK number?

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 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.

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)

How PPK is 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 CPK and PPK calculation?

If we look at the formulas for Cpk and Ppk for normal (distribution) process capability, we can see they are nearly identical: The only difference lies in the denominator for the Upper and Lower statistics: Cpk is calculated using the WITHIN standard deviation, while Ppk uses the OVERALL standard deviation.

What is PP PPK CP CPK?

Pp is what Ppk would have been if the process were centered. Cpk is what the Ppk will be if the process is stable (no change between subgroups mean). Cp is what Ppk will be if the process is stable AND centered.

What is PPK in statistics?

Ppk is an index of process performance which tells how well a system is meeting specifications . This index also takes into account how well the process is centered within the specification limits. … If Ppk is 1.0, the system is producing 99.73% of its output within specifications.

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…

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. In other words, they define what is expected from an item for it to be usable. …

How do you know if a process is capable?

All the data points fall well within the specification limits with a normal distribution. A process where almost all the measurements fall inside the specification limits is deemed a capable process.

What percentage is 4 sigma?

4 Sigma: 6.2K errors per million (99.4% accuracy).

What does a PPK of 1.33 mean?

meeting customer requirementsPpk < 1.33. The process is substandard for meeting customer. requirements. Process improvements must be given high.

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.

What does PPK stand for?

PPKAcronymDefinitionPPKPolizei Pistole Kriminal (German pistol)PPKPersonal Preference Kit (NASA)PPKParts Per Kilo (thousand)PPKPer Packet Keying16 more rows

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.

Is CPK always higher than PPK?

In short, Yes, Ppk can be larger than Cpk. … Cpk is an index that is designed to communicate the state of quality of what you are measuring. Cpk uses three pieces of information to calculate the index: The mean or average of the data that was collected.

What is Cp and Cpk formula?

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). and since the maximum value for k is 1.0, then the value for Cpk is always equal to or less than Cp.