University's accurate CMM facility available for sub-contract measurement

The Wolfson School's Dr Jon Petzing, senior lecturer in metrology, makes the claim. All the laboratory's equipment, including articulated-arm measuring machines, non-contact CMMs and a range of surface texture measurement instruments, are available to manufacturing and industrial companies looking to sub-contract their inspection. Recent Government funding of £160,000 was given to the Wolfson School to upgrade the UKAS-standard dimensional metrology laboratory. Two thirds of that went to buy a Metris LK Ultra co-ordinate measuring machine (CMM) from Metris UK. The British-built CMM has a 0.7 micron accuracy statement, although Dr Petzing indicated that 0.5 micron can be achieved in reality. Competitive German and Japanese machines costing 50 to over 100 per cent more offered similar accuracy. In addition, the Metris CMM had the smallest footprint, and while space is currently not at a premium in the laboratory, economising on floor area will mean that there will be room to install more equipment. One application in which the Ultra’s precision is proving useful is in the manufacture of tungsten carbide pistons used in collaboration with the National Physical Laboratory’s primary pressure standard. The Wolfson School is the only academic centre investigating manufacturing, surface characteristics and performance issues of such devices. Cylindricity, circularity and straightness have to be within one micron, which the previous best in-house CMM was unable to inspect as it was capable of only 3 micron accuracy. In practice, therefore, matched pistons and cylinders were paired by trial and error. Now, full 3D geometrical analysis on the Ultra enables a batch of 10 pistons to be machined and inspected so that they are fully interchangeable with three cylinders to a repeatable clearance of less than one micron, an achievement that has not previously been demonstrated.