Marco Bernardi
Mark_Navigator
Every process is multi-modal, based on the Total Variance Equation. Tool wear - the predominate variation in precision machining - is a continuous uniform distribution, but most other errors, such as sampling error, gage error, etc. are normal or otherwise tailed. Add them all up and you get a predominately uniform distribution with small tails contributed by the other factors in the equation.
So this issue should be the reason to stay on 75% spec. values? Then the combination of distributions, getting uniform behavior with tails on the extreme sides?