生产过程控制教材(英文版)(ppt 55页)

生产过程控制教材目录：
1、Variation, Tolerances and Dimensional Control4
2、Population, Sample and Normal Distribution15
3、Cp and Cpk Concept28
4、Use of the NMP Data Collection Spreadsheet44
5、Confidence of Cpk

生产过程控制全球教材内容提要：
Common Causes:
      Causes that are implemented in the process due to the design of the process, and affect all outcomes of the process
Identifying these types of causes requires methods such as Design of Experiment (DOE), etc.
Special Causes:
      Causes that are not present in the process all the time and do not affect all outcomes, but arise because of specific circumstances
Special causes can be identified using Statistical Process Control (SPC)
      For some critical dimensions we need to measure more than 1 part，For capability data we usually measure 5 pcs 2 times/hour=100 pcs (but sampling plan needs to be made on the basis of production quantity, run duration and cycle time)
     The difference between sLT and sST is only in the way that the standard deviation is calculated

sLT is always the same or larger than sST

If sLT equals sST, then the process control over the longer- term is the same as the short-term, and the process would not benefit from SPC

If sLT is larger than sST, then the process has lost control over the longer- term, and the process would benefit from SPC

The reliability of sLT is improved if the data is taken over a longer period of time.  Alternatively sLT can be calculated on several occasions separated by time and the results compared to see whether sLT is stable

 

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