A standardized numerical measurement collected over time to evaluate process performance, quality, or reliability. Good metrics are objective, repeatable, and directly tied to process capability or customer requirements. They form the raw data plotted on control charts and used to calculate capability indices.
The primary metric for that milling station is surface roughness, so make sure the gauge is calibrated before you start pulling samples.
Related terms
Cpk
Process capability index that accounts for centering: distance from the mean to the nearest spec limit in units of 3 sigma.
Control chart
Time-ordered plot of a process statistic with a centerline and limits that flag when the process has changed.
Process capability
How well a stable process's natural spread fits inside the specification limits, usually expressed as an index.
DPMO
Defects per million opportunities: defect count scaled by the number of chances for a defect in each unit.