Quick Answer: What Is PPK And CPK?

Is CPK always higher than PPK?

The automotive confusion aside, Ppk will always be greater than Cpk since Ppk is long term capabliity and Cpk is short term capability.

The only way that Cpk will be greater than Ppk (other than a misuse of the terms and formulas) is under the conditions stated in a previous post..

Should I use CPK or PPK?

So the key takeaway is that Cpk is the potential of a process to meet a specification (short term) while Ppk is how the process actually did (long term). … If the Cpk and Ppk calculations are very close or equal, then there is an even better indication that the process is statically in control.

Can CPK be lower than PPK?

In short, Yes, Ppk can be larger than Cpk. … Cpk uses three pieces of information to calculate the index: The mean or average of the data that was collected. The upper and/or lower specification.

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.

Are CPK and PPK the same?

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 does CPK 1.33 mean?

Process capability indexProcess capability index (Cpk) is a statistical tool, to measure the ability of a process to produce output within customer’s specification limits. … Cpk = or >1.33 indicates that the process is capable and meets specification limits.

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.

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.

Can CPK be greater than CPK?

At the same time, the potential to create product outside the specification limits increases. Cpk can only have positive values. It will equal zero when the actual process average matches or falls outside one of the specification limits. The Cpk index can never be greater than the Cp, only equal to it.

What is CP and 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.

What is CPK and how is it calculated?

Cpk is a process capability index used to measure what a process is capable of producing. … The formula for the calculation of Cpk is Cpk = min(USL – μ, μ – LSL) / (3σ) where USL and LSL are the upper and lower specification limits, respectively.

What is PPK?

Ppk is an index of process performance which tells how well a system is meeting specifications . Ppk calculations use actual sigma (sigma of the individuals ), and shows how the system is actually running when compared to the specifications. … If the system is centered on its target value, Ppk and Pp will be equal.

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 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 difference between CPK PPK and CMK?

Machine capability index can be used to measure the effectiveness of process improvement efforts. … But, for Cpk standard deviation is measured from the control chart, as this is a measure of process performance. Cmk is measured using continuous samples keeping all influences other than the machine parameters constant.