NIST Work Enhances Shop Floor Productivity

(National Institute of Standards and Technology: Washington, D.C.) -- National Institute of Standards and Technology engineers, together with colleagues from industry and other standards organizations have completed a five-part series of standards designed to evaluate the accuracy—and thus usability—of manufacturing measurements. The standards, the last of which was published last month by the American Society of Mechanical Engineers, describe ways measurement personnel can communicate, evaluate and respond to uncertainties in manufactured part measurements. Adopting these standards on the shop floor should enhance manufacturing productivity at the same time that it minimizes scrapping of acceptable parts, unnecessary rework, and even litigation.

In a previous era, shop engineers could relax if component parts varied slightly from specification. Parts just had to “fit together.” However the complexity of many of today’s products, ranging from airplane turbines to nanotechnology microscopes, requires ever more advanced measurement capabilities at the shop floor. The ASME standards were needed because measurements often vary each time they are made (even the temperature of the part can change the measurement result by a significant amount).

The series of standards also explains dimensional measurement traceability. Traceable measurements demonstrate the connection between the standard international (SI) unit of length (the meter) and the task-specific measurement under consideration; this also requires an uncertainty statement describing the accuracy of the measurement result.

The ASME B89.7 standards series addresses, with clear descriptions, the role of measurement uncertainty when accepting or rejecting products based on a measurement result and a product specification; economically efficient methods to overcome differences between two parties in the evaluation of measurement uncertainty; how to determine the economically appropriate decision to accept or to reject a product due to measurement uncertainty; and ways to demonstrate dimensional measurement traceability to the SI unit so that all parties can be sure of the reliability of their measurements. The latest addition to the series, B89.7.3.2, offers simplified guidelines for understanding and evaluating the major sources of measurement uncertainty.

NIST researchers chaired the ASME B 89.7 working groups and contributed to other related development work during the five-years it took to develop the five standards.

For more information, visit www.nist.gov/public_affairs/techbeat/tb2007_0412.htm#shop.

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