Measurement systems analysis (MSA), or gage reproducibility and repeatability (R&R), quantifies measurement variation from inspectors (reproducibility) and the gage itself (repeatability). This returns a measurement of the gage's precision, or ability to get the same result consistently from the same part. Precision is the counterpart to accuracy, or the gage's ability to get, on average, the correct measurement from a part. Gages must be precise as well as accurate to perform their jobs. While ISO 9001:2008 required only accuracy (as ensured by calibration), the automotive ISO/TS 16949 standard requires MSA as well.
MSA is a major and vital component of the control plan for a manufacturing process, which means that everybody involved in process planning (e.g. advanced quality planning) and process management needs to understand what it does and how it works. This includes understanding of the risks from poor gage capability (regardless of the gage's calibration status) and potential actions to address situations of this nature.
A control plan is a mandatory part of advanced quality planning (AQP), and it defines the required measurements for critical to quality (CTQ) part characteristics along with the required gages and instruments. This in turn defines the calibration and measurement systems analysis (MSA) requirements. Calibration and MSA ensure (respectively) that gages are accurate and that they are sufficiently precise for their roles in the control plan.
Quality managers, engineers, and inspectors with responsibility for process measurements and also advanced quality planning (AQP), R&D engineers, Six Sigma professionals, Auditors, Regulatory affairs, noting that MSA supports the control plan.
William A. Levinson, P.E., is the principal of Levinson Productivity Systems, P.C. He is an ASQ Fellow, Certified Quality Engineer, Quality Auditor, Quality Manager, Reliability Engineer, and Six Sigma Black Belt. He is also the author of several books on quality, productivity, and management, of which the most recent is The Expanded and Annotated My Life and Work: Henry Ford’s Universal Code for World-Class Success.