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H1.SCRAP REDUCTION

H2.UNDERSTANDING CPK

As you can see in the graphs, Cpk varies depending on where the center of the distribution is with respect to the specification limits but also depending on the spread (standard deviation) of the distribution:

The closer to the center of the specification limits, the better the Cpk.
The less spread, the better your Cpk.

H3.WHAT CPK STANDS FOR

"Cp" stands for Critical Process Capability whilst the "k" comes from Japanese and means "Katayori" which is bias.

CPK, PROCESS YIELD, SCRAP RATES, PPM

If a process is normally distributed, Cpk and process yield are linked. The metrics process yield and scrap rate are also measures for process capability. You typically find them expressed in percent or ppm (parts per million).
For example, a Cpk of 1.33 means that less than 0.01% of the total production is scrap. See our table below.

ASSUMPTIONS OF THE CPK

Data is representative of the process
The process is stable (no special causes)
Data is normally distributed

HOW TO CALCULATE CPK

CPK vs PPK

Click here to learn more about the differences.

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