Metrics to monitor process improvement

[carvind]

Can someone provide a reference where there is a detailed discussion (with examples) on creating metrics to assess how much a process needs improvement. Any help would be greatly appreciated. Thanks in advance.

 

[Darius]

"how much a process needs improvement ?", the answer is you have to continue to improve the process while is economically possible.

If the changes cost more than what you are going to obtain from the improvement, it's time to stop or look for other alternatives.

Look for Taguchi's Loss function, It may help you

http://www.mv.com/ipusers/rm/loss.htm
http://class.et.byu.edu/mfg340/lessons/lossfunction/

 

[Sam]

Darius, Those are two very informative sites for the expalnation of the loss function.
Having read them one of the statements seems to jump out;

"For example: A medical company produces a part that has a hole measuring 0.5" + 0.050". The tooling used to make the hole is worn and needs replacing, but management doesn't feel it necessary since it still makes "good parts". All parts pass QC, but several parts have been rejected by assembly. Failure costs per part is $0.45. Using the loss function, explain why it may be to the benefit of the company and customer to replace or sharpen the tool more frequently."

It appears to me that if the parts pass inspection but still will not assemble, it would be a another problem rather then a worn tool.
I don't know, maybe I'm not reading the example correctly.

 

[Darius]

Sam

The example said that the parts pass inspection but were reyected not that they did not assemble, of course it may be that they didn't, but also that in the assembly line the operator didn't like the way it fit (too much loose), but it's still a good example of Taguchi's loss function (most of the text just tell the teory, but not how to apply).