Meaning
Statistical evaluation of a measurement system determines the amount of variation introduced by the measurement device and the operators performing the test. Through gauge r&r, molders evaluate whether a chosen inspection process is capable of reliably distinguishing between acceptable and defective polymer parts. This study isolates the repeatability of the equipment from the reproducibility of the human inspectors to secure reliable quality data.
Molding Application
Soft plastic parts are highly susceptible to operator-induced measurement variation due to differences in manual hand-gauge pressure. Conducting a gauge r&r study reveals if different quality technicians are compressing the elastomer differently during caliper or micrometer checks. This analysis is essential for qualifying inspection processes before starting a high-volume run of flexible or thin-walled components.
Process Qualification
Mold validation protocols like production part approval processes demand a measurement system variation of less than ten percent of the total tolerance band. If a gauge r&r study reveals a variation above thirty percent, the measurement system is considered unacceptable, prompting a redesign of the fixtures or the selection of non-contact optical methods. Minimizing this measurement uncertainty is the only way to ensure that borderline parts are correctly classified.
This systematic reduction in variation reduces the likelihood of false failures.
Data Collection
Testing requires multiple operators to measure several parts across multiple trials to generate a statistical dataset. In gauge r&r, the selected parts must span the entire expected range of process variation to yield a realistic assessment.
