Use a Cpk study on your screen printer. Deviation from print to print.
Most reutable surface mount machine companies will supply you with their Cpp study they performed on your machine before they shipped it.
On ovens use your profiler. You can determine Cpk on peak temps, or times above liquidous - what ever.
You'll find that this kind of paper work is only good for auditors or pencil pushers that have no clue how solder works yet are in charge to make such calls.
Never use a Cpk study to determine your machines capabilities - as Cpk only determines repaetability. If you have new equipment perform your Cpk and then jump in and see how far you stretch your process windows. This information is far more valuable than any Cpk study. I always see a Cpk study as driving a car in a perfect world. I push the pedal all the way down and it goes 55 MPH - I push the break and it stops exactly in 120 feet of distance. In the real world I can't always drive a constant 55MPH and sometime I have to stop under a distance of 120 feet. It's good to know it will always do 55 MPH and stop at 120 feet, but in the real world you will never use it. (Oops, I just fell off my soap box - or was I pushed off?)
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