Webinar On "Measurement Systems Analysis"

Calibration of gages and instruments is a familiar activity whose purpose is to determine whether the gages in question return, on average, the same dimensions as the standards against which they are calibrated. This is required by ISO 9001. Calibration does not, however, ensure or even measure precision; the consistency with which the gages return the dimension in question. This is the purpose of measurement systems analysis (MSA), or gage reproducibility and repeatability (R&R).

1. Calibration (comparison of the gage's average measurement of a standard's dimension against the standard's actual dimension) and precision (the gage's ability to return the same measurement consistently) are two separate but important aspects of measurement system performance.
2. Gage R&R refers to repeatability (variation inherent to the gage, similar to common cause variation) and reproducibility (variation due to differences between inspectors).
3. Gage variation affects not only outgoing quality but also the power of SPC charts to detect process shifts. It does not however increase the false alarm risk for SPC charts.
4. The standard procedure for MSA includes minimum requirements for parts, inspectors, and replicated measurements. Readily available software such as Minitab and StatGraphics can then identify the variance components (repeatability and reproducibility) and overall gage variation, and also perform tests for the adequacy of the study.

A table of the d*2 factors (necessary for performance of the calculations in Excel) will be provided.

• Manufacturing  engineers
• Quality engineers
• Technicians
• Inspectors with responsibility for inspections that involve quantitative measurements of parts.

William A. Levinson, P.E., FASQ, CFPIM, is the owner of Levinson Productivity Systems PC. He holds professional certifications from the American Society for Quality, APICS, and Society of Manufacturing Engineers.