Improving Measurements


Coleman, David E.; Stein, Philip G.   (1990, ASQC)   Alcoa Laboratories, Alcoa Center, PA

Quality Progress    Vol. 23    No. 11
QICID: 12343    November 1990    pp. 35-39
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Article Abstract

Statistical process and measurement control (SPMC) analyzes and controls measurement systems. SPMC uses the measurement capability study (MCS) and measurement process control (MPC). An MCS analysis is analogous to a process capability study. MCS involves the identification and quantification of measurement variability. This is followed by suggestions for redesign of the measurement process and monitoring of the improvements. A case study demonstrates an MCS of a repeatability problem in a dimension-measuring machine. MPC is analogous to SPC (statistical process control). Whereas SPC analyzes a product, MPC examines measurement. Plots of MPC show the status of groups of measurements, while control charts indicate when the measurement process is out of control. A case study describes how computerized automatic test equipment in a television chassis factory is calibrated and prevented from drifting out of control. Because every measurement is susceptible to error and because only some errors are crucial, SPMC is a key to improving measuring equipment and their measurements.


Case study,Capability study,Manufacturing,Measurement and control,Process control,Variation,Statistical process control (SPC)

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