制程能力分析中Cpk或Ppk中的k是哪个单词的缩写？或代表什么意思？查过很多资料，百思不得其解，希望有高人给出答案，将不胜感激。

本帖最后由 flying008 于 2011-9-21 16:31 编辑

今天无意中在灌水的时候突然想起曹兄弟这个贴子, 下面是我paste过来的国外原文, 希望可以一程度上回答你的疑问, 哈哈……
Cp = Process Capability. A simple and straightforward indicator of process capability. Cpk = Process Capability Index. Adjustment of Cp for the effect of non-centered distribution. Pp = Process Performance. A simple and straightforward indicator of process performance. Ppk = Process Performance Index. Adjustment of Pp for the effect of non-centered distribution.

The "k" stands for "katayori" which means deviation, inclination or offset in Japanese. The origins of k actually go back to the 1970s in Japan. The Japanese are credited with developing the the Cp, Cpl, Cpu, Cpk, and k indexes of process capability.

So what is k? It is an index of process centering, defined as follows, where M is the middle of the tolerance, mu is the process average, USL is the upper spec limit, and LSL is the lower spec limit:

k = |M - mu| /

k is then used as follows to compute Cpk.

Cpk = Cp (1 - k)

When the process average is centered at the middle of the tolerance, M = mu, and therefore, M - mu = 0. With k = 0, Cpk will equal Cp.

Cpk = Cp (1 - 0) = Cp

If the process average is centered anywhere else, then the absolute value of the quantity M - mu is greater than zero, making k also greater than 0. Suppose k is 0.30 for a process. Then the Cpk index for this process is only 70% of the Cp index.

Cpk =Cp (1 - 0.30) = 0.70Cp

So in one way, k measures how much potential capability is lost due to poor centering. In the above example, Cpk could be increased by 30% if we could center mu at M.

==>其实英文缩写或语句里有日文译字也很正常, 我随手拿来一份英文表格, 上面标题是"Deviations identified at GENBA", 你要真在英文单词辞海里找这个翻译, 那就要纠结好长时间哟……:P