![]() The familiar method is called “average and range,” or “long AIAG.” This method is intended for spreadsheets or pocket calculators, but it is not recommended for professional software. The most familiar method is not the best. There are three ways to calculate Gage R&R results. In Figure 1, data for a typical Gage R&R study has been entered into GAGEtrak software. The person collecting the data should present the parts in random order but record the measurements according to the temporary part number. For example, you have only 8 parts and 2 operators or the trials are very expensive. Smaller sample sizes can be used if there is a reason. Normal sample sizes are 10 parts, 3 operators and 3 trials for a total of 90 measurements. This can happen even if an operator is consciously trying not to do so. Just knowing what to expect will tend to reduce the variation. Operators can often influence a gage to a considerable extent. The parts have to be temporarily numbered in a way in which they can avoid knowing which number is being measured. They also need to take precautions to make sure they never know which part they are measuring. The people who do the measurement have to know how to measure, of course. He or she would serve as a resource to answer questions and would have access to Gage R&R Software. A calibration technician would often be a good choice. (During the try-out phase of a new part, you may have to use substitutes for the people who will actually do the measurements in the future.) These might be production people, quality inspectors or lab technicians, depending on the situation. ![]() This is required for each production measuring process, but not for each gage – you might have 3,000 gages and only 200 production measuring processes.Ĭhoose three people who do the measurements in production. The purpose is to confirm that variation is not excessive or to take action if the variation is found to be excessive. The primary variables are repeatability and reproducibility (R&R). The method is to measure variables of production measuring processes. Today’s software makes Gage R&R data entry and calculation easy, but learning to effectively interpret the results is imperative. More importantly, however, this single study may be the only chance to find measurement quality problems. Nearly every manufacturing company is required to conduct these studies, the many benefits gleaned from which range from product acceptance measurements and reliable control charts to objective equipment selection criteria and identifying the need for operator training. ![]() Calibration alone won’t produce quality measurements even when perfectly accurate, a gage can be unacceptable for measuring a product or process. ![]()
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