What is Cpk and 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 a PPK of 1.67 mean?
Interpretation. Pp and Ppk > 1.67 The process probably meets customer requirements. After approval, begin production and follow the Approved Control plan. 1.33 ≤ Ppk ≤ 1.67 The process may not meet customer requirements.
What does a Cpk of 1.67 mean?
Excellent, Capable
CPK >1.67 (Excellent, Capable)
What does a Cpk of 1.33 mean?
In general, the higher the Cpk, the better. A Cpk value less than 1.0 is considered poor and the process is not capable. A value between 1.0 and 1.33 is considered barely capable, and a value greater than 1.33 is considered capable.
What is Cpk used for?
Cpk is used to estimate how close you are to a given target and how consistent you are to around your average performance. Cpk gives you the best-case scenario for the existing process. It can also estimate future process performance, assuming performance is consistent over time.
What does a PPK of 1.0 mean?
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. If Ppk is between 0 and 1.0, not all process output meets specifications.
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 does a PPK of 0.5 mean?
Interpreting P
For instance, Machine A has Ppk of 1.0 and Machine B has Ppk of 0.5. From Ppk value, one can drive that Machine A is producing 99.73% of its output within specifications.
What are acceptable Cpk and PPK values?
What sigma is 1.33 Cpk?
4.0
Sigma level table
| Two sided table | ||
|---|---|---|
| Cpk Ppk | Sigma level | % out of tolerance |
| 1.00 | 3.0 | 0.27 |
| 1.17 | 3.5 | 0.05 |
| 1.33 | 4.0 | 0.01 |
What does Cpk 1.66 mean?
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 PPK means?
Ppk stands for Process Performance Index and is used for long-term variability.
What is the highest Cpk value?
The minimum value of “k” is 0 and the maximum is 1.0. A perfectly centered process will have Cp = Cpk.
…
Cpk will never exceed the Cp
- Cp is a measure of variation only.
- Cpk is a measure of location and variation.
- Cp will never be a negative number.
- Cpk can be a negative number.
What if PPK is less than 1?
What does a high PPK mean?
a more capable process
Generally, higher Ppk values indicate a more capable process. Lower Ppk values indicate that your process may need improvement.
What does a low PPK mean?
Generally, higher Ppk values indicate a more capable process. Lower Ppk values indicate that your process may need improvement.
What is a good PPK value?
What Cpk is 3 sigma?
1.00
Relationship to measures of process fallout
| Cp | Sigma level (σ) | Process yield |
|---|---|---|
| 1.00 | 3 | 99.73% |
| 1.33 | 4 | 99.99% |
| 1.67 | 5 | 99.9999% |
| 2.00 | 6 | 99.9999998% |
What is Cpk normal range?
Normal Results
Total CPK normal values: 10 to 120 micrograms per liter (mcg/L)
How do you read PPK values?
Generally, higher Ppk values indicate a more capable process. Lower Ppk values indicate that your process may need improvement. Compare Ppk to a benchmark value that represents the minimum value that is acceptable for your process. Many industries use a benchmark value of 1.33.
What is a good Cpk value?
What if Cpk is less than 1?
Why is it called 6-sigma?
It’s called Six Sigma because the term sigma refers to one standard deviation in a data set. The idea is that six such deviations should occur before the process results in a defect. When a process achieves Six Sigma, it reaches a point where only 3.4 errors per one million process events result in a defect.
Why Six Sigma means 3.4 defects?
Because it is almost impossible to achieve zero defects — a concept known as infinity sigma — six sigma allows for 3.4 defects per million opportunities for a defect to occur. In contrast, three sigma allows for 66,807 defects per million opportunities.
What is a good CPK?