Quick Answer: What Is PPK Vs CPK?

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 the highest Cpk value?

1.0The 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.

Why is PPK higher than CPK?

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.

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 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.”

Which is better 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). 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.

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 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.

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.

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

How is CPK 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 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 does a Cpk of 2.0 mean?

process capability indexThe process capability index, or Cpk, measures a process’s ability to create product within specification limits. … 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 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)