工序能力分析(电子企业).ppt

过程能力分析CpkZ 那么 . . . 什么是 “好” 和 “不怎么好”? 红 (坏的) 黄 (还行) 绿 (好的) 为什么这么做? 为了回答 . . . 总体上讲, 过程 表现如何? 练习: 缺陷计算 The purpose of this slide is to emphasize the differences between an “entitlement” study and a “performance” study. Emphasize that the entitlement study should be taken over a short enough period of time to only involve 1 “set-up”, 1 lot of material, 1 set of people, basically minimal sources of variability with no time for a shift in the mean to occur whereas performance needs to have multiple set-ups and all sources of variability acting onthe process. Participant Notes: Remember, Six Sigma is a short term goal. GE will report short term sigma scores and long term DPMO. Look up 3.4 DPMO or 3.4E-06 on the normal table and you will see it has a Z value of 4.5 NOT 6.0. When we have long term data we calculate DPMO and convert it to the Z value. Then we add 1.5 to that number to get a short term Z value. Hence, GE talks about 6? (short term Z score) being equivalent to 3.4 DPMO in the long term. Be consistent...If you have short term datayou cannot add 1.5 to the Z score! Short term data does not capture total range of variation of a design or process. A reasonable estimate of the long term standard deviation can be obtained by multiplying the short term standard deviation by 1.3. This is the method applied to continuous data. The key to all of this is : 1. Consistency in applying the 1.5 shift -If you gather short term data (Capability or Entitlement Study), DO NOT apply a 1.5 ? shift -If you gather long term data (Performance Study or Historical data), add the shift 2. Report short term ? values and long term DPM 3. Minitab or the normal table is useful for both Variables and Attribute type of data Read through this slide. It leads to the next slide - How do I determine if it’s the centering or the spread ? Explain how defects are created from not having the average of the data centered on the target or center of spec. Draw an u