Tolerancing will not necessarily determine if a good part or a bad part will be produced, but it can help determine if the final assembly is going to be in tolerance as opposed to the individual parts themselves. It is possible to produce parts that conform to individual tolerances, but when put together the parts don't work because the overall effect on assembly has not been analyzed.
"A good tolerancing scheme is needed all the way through to final assembly," said Steve Scigliano, business unit manager of quality at the San Jose, CA-facility of Tecnomatix Technologies (Herzeliya, Israel). "Companies should manage tolerances not only in the design phase, but also in the manufacturing phase.