A new range of UKAS-certified length and form artefacts, complete with holding fixture, has been introduced by Derby-based coordinate measuring machine (CMM) manufacturer LK Metrology Ltd, allowing the inspection accuracy of any 3-D measuring platform to be verified, and thereby giving a user greater confidence in the results of an inspection — whether for metrology or reverse engineering — long after the typical annual calibration of the measuring machine has been carried out.

Each CMM Checking Gauge (CCG) enables independent monitoring and verification of accuracy through regular intermediate checks on a CMM or portable measuring arm, giving an OEM certainty that prototypes and production parts are within tolerance, while sub-contractors can assure their customers that machining and inspection carried out on their behalf are accurate. Artefact measurement uncertainty is down to ±0.01μm.

CCG provides an efficient go/no-go check with measurement results for ongoing CMM monitoring. Three combinations of length bars, ring gauge, test sphere and fixture of different sizes are available to suit various measuring machine models. Regular use provides an early warning of changes in the inspection system and an opportunity to take pre-emptive action.

Once identified, accuracy issues — due perhaps to environmental changes or an unnoticed probe crash — can be addressed by scheduling an interim machine service or calibration before downstream manufacturing processes are impacted.

The gauge is supplied in a carrying case with a program on a USB drive that runs in LK’s Camio measuring and reporting software. The program comprises DMIS measurement and alignment routines for bridge and horizontal arm CMMs, allowing the CCG cycle to run seamlessly on LK machines. However, it is easy for operators of other 3-D measuring platforms using different software to program a probing cycle around the artefacts to check for machine accuracy.