Important tooling and casting production decisions are based on dimensional data generated by foundry measurement systems. These measurements systems should be able to generate inspection information that is reliable enough to allow foundry personnel to make dimensional decisions with confidence. However, measurement errors caused by inadequate measurement equipment or inadequate use of the equipment can compromise dimensional decisions. Gage Repeatability and Reproducibily (R&R) evaluation is a key way of quantifying a measurement system's performance and acceptability.

The performance of commonly used inspection equipment and systems, used for casting dimensional inspection, has been studied. Factors that affect measurement errors have been identified. These results have been evaluated to determine the appropriate use and selection of dimensional measurement equipment for casting dimensional inspection. The type of measuring instrument, casting surface finish, and the size of the feature being measured all affect R&R. R&R also dictates the established casting dimensional tolerance ranges that can be measured with confidence.

All these factors will be discussed for making the choice of a measurement system for a particular measurement application. It has been found that the coordinate measuring machine (CMM) has the best repeatability and reproducibility of the measurement instruments. The micrometer, layout machines and calipers must be used for casting dimensional inspection with great care. Recommendations for the selection and use of appropriate foundry dimensional inspection equipment are presented.