A large reference artefact for CMM verification

This report describes the design, construction and calibration of a large reference artefact suitable for use as a length artefact in the verification of co-ordinate measuring machines (CMMs). The artefact is of modular design, constructed in 1 m and 0.5 m tubular sections made from carbon-composite materials. Each section can carry a range of reference surfaces including reference spheres (tooling balls). The artefact has been calibrated by three metrology laboratories using a repositioning methodology. Equipment for supporting the artefact during the verification of a CMM has also been designed and constructed. The artefact and positioning equipment have been successfully tested in the verification of two large CMMs according to the principles of ISO 10360-2. The design philosophy and calibration methodology are flexible and can be easily adapted, providing a practical approach to large CMM verification.