Approaches to the Calibration of Freeform Artefacts on Coordinate Measuring Machines

The paper compares two different experimental methods to establish the traceability of freeform measurements on coordinate measuring machines: i) uncertainty assessment using Modular Freeform Gauges, and ii) uncertainty assessment using Uncalibrated Objects. The first approach is an application to freeform geometries of the method described in ISO TS 15530-3 based on comparisons. The second approach is inspired by the procedure currently being developed within ISO TC213, involving repeated measurements of a given object in different orientations with variation of measuring parameters etc. The feasibility of the two approaches for freeform geometries is demonstrated through the calibration of a turbine blade.