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What is a Measurement System Analysis / Gauge R&R Study?

Gauge R&R is the most common Measurement System Analysis (MSA) method used to practically determine the measurement uncertainty of equipment and inspection processes.

A Gauge Repeatability and Reproducibility Study, commonly known as Gage R&R or GR&R, is a Measurement System Analysis (MSA) tool used in metrology and the inspection industry to determine the equipment variance (repeatability) and process variance (reproducibility). This typically involves repeat measurement of multiple parts by multiple operators under controlled conditions using the inspection process to experimentally determine the system’s capabilities.

In the Aero Engine supply chain, the standard AS13003 defines the minimum requirements for an MSA, including the minimum requirements for a Gauge R&R. Additional requirements may be stipulated by OEMs such as Rolls Royce, GE or P&W. These requirements typically specify the actual required number of measurements and operators to be used.

Type 1 Gauge (repeatability) Study

A Type 1 gage study is normally used to determine the baseline repeatability of a measurement system. It involves repeated measurements of one part, on one instrument, by one operator to establish the baseline repeatability of the inspection process. In this type of study the part normally remains in situ while repeat measurements are made. For automated processes, such as CMM inspection, this may be as low as 3 or 5 runs due to the inherent repeatability of automated processes. For a manual inspection process the number of runs is normally significantly higher, and could be up to 50 runs.

Type 2 Gauge (reproducibility) Study

A Type 2 gage study is used to determine the reproducibility of a measurement system. This typically involves multiple operators inspecting multiple parts and then performing a statistical analysis on the results. In a good measurement system, there should be minimal variance between the operators running the process. The intention of a Type 2 study is to quantify the variance that could be expected in production as a result of variation in the inspection process and to highlight areas for improvement, such as fixturing, operator training, the inspection program, or even the hardware. We can help you design your Gauge R&R, carry out the study, and interpret results. We can even help you with root cause analysis if required.

The objective in the analysis of a Gauge R&R study is to split the variation into individual components: repeatability, reproducibility, parts, operators, etc., and then look for indications of any specific sources of variation.

AS13003 Section 8.2.4

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