PTB News 2/2003 (380 kB) PTB News 2/2003, English edition, Issue August 2003The “virtual coordinate measuring machine”, developed by PTB, is ready for practical use. A whole network of calibration laboratories will employ the new procedure and make it available to industry. With this procedure, realistic measurement uncertainties for coordinate measurements can now be determined automatically.
Coordinate measuring machines (CMM) as universal measuring facilities are widely used for quality assurance in industry where they serve to measure motor units and many other workpieces. To determine the suitability of a CMM for a measurement task and to define reasonable product tolerances – a significant requirement from an economic point of view in particular –, it is important to know the measurement uncertainty for the features of a workpiece.
These measurement uncertainties can be determined by the virtual CMM. The procedure is based on measurements simulating the metrological behaviour of the CMM. The software module needed for this purpose can now be obtained from two German CMM manufacturers. It is directly integrated into the CMM software and together with the measurement report it automatically furnishes the measurement uncertainty assigned to the measurement result.
In a joint project with partners from industry and universities, the procedure has been confirmed on the basis of more than 13 000 comparison measurements so that the “Deutscher Kalibrierdienst” (DKD, German Calibration Services) could accredit several laboratories for the use of this procedure. Thus a network of calibration laboratories is available capable to calibrate any prismatic workpieces as reference standards. These calibrated standards can be supplied to industry enabling it to ensure the traceability of its measuring facilities.