What do CP and CPK mean in quality management?

CP is an index used to measure the potential capacity of a machine or process. CP is more suitable to represent the processing capacity of a process (regardless of specifications), and CPK is an index used to measure the ability of a machine or process to produce products within specifications. CPK is more suitable for expressing the defective rate of products produced in the process.

The difference between CP and CPK:

1, CP=CPK (K=0 at this time) only when the measured value is a bilateral tolerance and the distribution center coincides with the standard center.

2. When the distribution center of mass characteristics is just at the upper or lower limit of the standard, then K= 1.

3. When the distribution center of quality characteristics is outside the standard limit, then k >；; 1。 The smaller the k value, the better.

Because the quality distribution center and the standard center often do not overlap in production practice, the actual and effective standard range can not be fully utilized. After the offset occurs, the added capacity distributed on the left side of the center cannot compensate the lost capacity of the process on the right side. The process capability index can only be calculated by the smaller value of the two. This process capability index can also be called modified process capability index, which is recorded as CPK. The modified process capability index is a general process capability index.