One is in QS9000. Ppk in QS9000 means Preliminary Process Capability Index. It should be calculated before Mass Production and based on limited product quantity. Normally, it should be more than 1.67 because it's a short term process capability which doesn't consider the long term variation. But, in QS9000 3rd edition, there's no Compulsory Requirement that the Ppk must be more than 1.67. In QS9000 3rd edition, it states like Ppk/Cpk >=1.33.
Another one is in 6-Sigma. Ppk in 6-Sigma means Process Performance Index. It's a long term process capability covered the long term process variation and based on more product quantity. Gernally, in 6-Sigma, the Ppk value is less than Cpk value.
xbjia (2004-2-13 08:22:23)
QUOTE:
Originally posted by stone at 2003-1-14 07:58 PM:
嗨！大家好!小女子有一个问题想要请教大家。什么是PPK？PPK与CPK有什么不同？他们的使用场合有什么不同？他们的计算公式又有什么不同的？谢谢！
Ppk
Overall performance capability of a process, see Cpk. 过程的整体表现能力。
Cp
A widely used capability index for process capability studies. It may range in value from zero to infinity with a larger value indicating a more capable process. Six Sigma represents Cp of 2.0. 在流程能力分析方面被广泛应用的能力指数，在数值方面它可能是从零到显示更强有力流程的无穷大之间的某个点。六个西格玛代表的是Cp=2.0。
Cpk
A process capability index combining Cp and k (difference between the process mean and the specification mean) to determine whether the process will produce units within tolerance. Cpk is always less than or equal to Cp.一个将Cp和k（表示流程平均值与上下限区间平均值之间的差异）结合起来的流程能力指数，它用来确定流程是否将在容忍度范围内生产产品，Cpk通常要么比Cp值小，要么与Cp值相同。
最新回复
willianli (2003-11-24 15:35:31)
pippo (2003-11-28 21:09:53)
PPK的值应该比CPK要高些！
wanghaiyan715 (2003-11-30 00:04:32)
stdev (2003-11-30 20:27:27)
CPK : Capability Indies of Process
PPK : Performance indies of Process
cjj (2003-12-01 09:06:43)
luckyw (2003-12-01 16:58:31)
elicoer (2003-12-02 12:24:53)
而CPK，是进入大批量生产后，为保证批量生产下的产品的品质状况不至于下降，且为保证与小批生产具有同样的控制能力，所进行的生产能力的评价，一般要求≥1.33
一般来说，CPK需要借助PPK的控制界限来作控制。
PPAP，即生产性零组件核准程序，它是你向你的顾客提供你所承制产品的品质保证，它包括了从设计开发、过程控制、各种测量及试验的过程控制，以及必须的生产/标准样件。它利用APQP的思路，结合了FMEA、CP、MSA、SPC的QS-9000工具，是一种对品质的全面自发性的保证。
原则上来讲，你向你的顾客提供了PPAP的保证，你的顾客可以免除对你产品的验证而直接使用。
jiangyic (2004-2-12 13:25:52)
vividquality (2004-2-12 18:09:42)
One is in QS9000. Ppk in QS9000 means Preliminary Process Capability Index. It should be calculated before Mass Production and based on limited product quantity. Normally, it should be more than 1.67 because it's a short term process capability which doesn't consider the long term variation. But, in QS9000 3rd edition, there's no Compulsory Requirement that the Ppk must be more than 1.67. In QS9000 3rd edition, it states like Ppk/Cpk >=1.33.
Another one is in 6-Sigma. Ppk in 6-Sigma means Process Performance Index. It's a long term process capability covered the long term process variation and based on more product quantity. Gernally, in 6-Sigma, the Ppk value is less than Cpk value.
xbjia (2004-2-13 08:22:23)
QUOTE:
http://www3.6sq.net/cdb/viewthread.php?tid=16281huzi (2004-2-13 16:28:39)
Overall performance capability of a process, see Cpk. 过程的整体表现能力。
Cp
A widely used capability index for process capability studies. It may range in value from zero to infinity with a larger value indicating a more capable process. Six Sigma represents Cp of 2.0. 在流程能力分析方面被广泛应用的能力指数，在数值方面它可能是从零到显示更强有力流程的无穷大之间的某个点。六个西格玛代表的是Cp=2.0。
Cpk
A process capability index combining Cp and k (difference between the process mean and the specification mean) to determine whether the process will produce units within tolerance. Cpk is always less than or equal to Cp.一个将Cp和k（表示流程平均值与上下限区间平均值之间的差异）结合起来的流程能力指数，它用来确定流程是否将在容忍度范围内生产产品，Cpk通常要么比Cp值小，要么与Cp值相同。
flyingpard (2004-2-14 08:42:48)
jiangyic (2004-2-14 19:39:35)
spbgxb (2004-2-15 11:04:53)
凌晨三点半 (2004-2-15 13:34:13)
QUOTE:
很全面，能够认识到这一层很不错spbgxb (2004-2-15 13:57:28)
2003-11-24 03:35 PM
请问，sigma的计算公式如何不一样了？
spbgxb (2004-2-15 13:59:18)
QUOTE:
如何不一样呀？高人快指点！！！！Cissy (2004-2-15 14:14:15)
Cp= ─
6σ
T
Cpk=(1-K)Cp=(1-K)─
6σ
T
Pp= ─
6σ
Ppk=(1-K)Pp
C系列过程能力指数与P系列过程能力的指数的公式类似，二者的主要区别在于：前者的公式中的σ的估计值且必须在稳态下计算，而后者公式中的σ是实际值，是在实际不一定稳定下计算。
[ Last edited by Cissy on 2004-2-15 at 14:15 ]