MSA Chicken and Egg - Process Capability and Measurement System Capability

[M Greenaway]

Can someone explain the following concept to me that is outlined in the QS9000 MSA Manual.

In broad terms it states that overall process capability is the sum of the manufacturing process capability and the measurement system capability.

Fine, but in determining the manufacturing process capability dont we have to use a measurement system ?

How do we isolate a measurement of process capability ?

 

[JRKH]

Very good question.

MSA needs to be conducted before Process Capability is measured. If possible the measurement error needs to be reduced to an insignificant level based on the accuracy required by the process.

The "Manufacturing Process Capability" speaks to the ability of your equipment. This type of capability study should use the most accurate measurment available, possibly even in a controlled envoronment to virtually eliminate measurement error as a factor.

"Process Capability Studies" then utilize these knowns to evaluate the overall capability of a process.

I trust I have helped clarify the mud, or mudify the clare, or whatever.

At least this is how I read it.

James