Dimensional variability of production iron castings

The dimensional variability of casting features from production gray and ductile iron castings has been characterized. Dimensional data from castings and patterns has been collected front castings produced at seven jobbing foundries. The variability of over 300 casting features from castings produced in green sand molds using jolt squeeze, high-pressure horizontal parting line and vertical parting line molding processes have been evaluated. A comprehensive database of casting, pattern and feature variables have been developed so that the influence of these variables on dimensional variability can be determined. Measurement system analysis techniques were used to ensure that large measurement errors were not reported as dimensional variability. Results indicate that the dimensional variability of production casting features is less than is indicated by current International Standards Organization (ISO) standards. The type of molding process strongly influences dimensional variability-high-pressure molding results in reduced casting dimensional variability. Other geometric considerations, such as feature size, casting weight and parting line, also influence variability. Corresponding pattern measurements indicate that the actual pattern allowances for casting features vary considerably. This variation in pattern allowances strongly influences the ability of the foundry to satisfy customer dimensional requirements.