FuelInjectorNozzles-EN.pdf - Assessing Measurement System...

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Assessing Measurement System Variation Example 1: Fuel Injector Nozzle Diameters Problem A manufacturer of fuel injector nozzles installs a new digital measuring system. Investigators want to determine how well the new system measures the nozzles. Data set Nozzle.MPJ Description Variable Fuel injector nozzle measured Nozzle Data collection Technicians randomly sample, across all major sources of process variation (machine, time, shift, job change), 9 nozzles that represent those that are typically produced. They code Operator who measured Operator Original run order of the experiment Run Order Measured diameter of nozzle (microns) Diam the nozzles to identify the measurements taken on each nozzle. The first operator measures the 9 nozzles in random order. Then, the second operator measures the 9 nozzles in a different random order. Each operator repeats the process twice, for a total of 36 measurements. Note For valid measurement system analyses, you must randomly sample and measure parts. The specification for the nozzle diameters is 9012 ± 4 microns. The tolerance is 8 microns. Tools Gage R&R Study (Crossed) Gage Studies for Continuous Data 3 Assessing Measurement System Variation
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Measurement systems analysis What is measurement systems analysis Measurement systems analysis assesses the adequacy of a measurement system for a given application. When measuring the output from a process, consider two sources of variation: Why use measurement systems analysis Measurement systems analysis answers questions such as: Can the measurement system adequately discriminate between different parts? Part-to-part variation Is the measurement system stable over time? Measurement system variation Is the measurement system accurate throughout the range of parts? If measurement system variation is large compared to part-to-part variation, the measurements may not provide useful information. For example: Can a viscometer adequately discriminate between the viscosity of several paint samples? When to use measurement systems analysis Before you collect data from your process (for example, to analyze process control or capability), use measurement system analysis to confirm that the measurement system Does a scale need to be periodically recalibrated to accurately measure the fill weight of bags of potato chips? measures consistently and accurately, and adequately discriminates between parts. Does a thermometer accurately measure the temperature for all heat settings that are used in the process? Gage Studies for Continuous Data 4 Assessing Measurement System Variation
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Gage R&R study (crossed) What is a gage R&R study (crossed) A crossed gage R&R study estimates how much total process variation is caused by the measurement system. Total process variation consists of part-to-part variation plus measurement system variation. Measurement system variation consists of: Why use a gage R&R study (crossed) This study compares measurement system variation to total process variation or tolerance. If the measurement system variation is large
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