A
Aashish
Please guide me on starting the process capabilities studies in Pig Iron Industry having 2 small blast furnaces.
I'm scratching my head. I have always viewed process capability as 'this is what we get'. The simplest example would be goods out the door. You measure a number of parts over a period of time, then calculate Cp, Cpk.
If you have gage or measurement error, that is not process error. It masks process error, and it makes your data invalid. So, that is not process error, and is not the point. It must be made statistically insignificant before any understanding of the variation is understood. If you have process variation (tool wear, for example), and add batch variation, multiple machines, etc., then it is mutltimodal, non-normal and Cpk and Ppk will be of no value. It would still be recommended to minimize the variation of those additional variances to be statistically insignificant, if it is economically feasible, to increase the process output stability across the streams..Yes, this does include all of the process variation such as batches, machines, gauges, men (or indeed women, or any sentient carbon based life form!). But isn't this the point? .
If your product is not good enough, then you improve the process by finding out what is causing the variation (by developing the total variance equation in fact!) then using all of the usual SPC techniques to fix the problems.
I suspect that I am misunderstanding you, but you seem to be implying in your response that you should fix the process before deciding if it is capable, which is begging the question .
If you have gage or measurement error, that is not process error.