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Modern coordinate measurement machines (CMM) are universal tools to measure geometric features of complex three-dimensional workpieces. To use them as reliable means of quality control, the suitability of the device for the specific measurement task has to be proven. Therefore, the ISO 14253 standard requires, knowledge of the measurement uncertainty and, that it is in reasonable relation with the specified tolerances. Hence, the determination of the measurement uncertainty, which is a complex and also costly task, is of utmost importance.The measurement uncertainty is usually influenced by several contributions of various sources. Among those of the machine itself, e.g., guideway errors and the influence of the probe and styli play an important role. Furthermore, several properties of the workpiece, such as its form deviations and surface roughness, have to be considered. Also the environmental conditions, i.e., temperature and its gradients, pressure, relative humidity and others contribute to the overall measurement uncertainty.Currently, there are different approaches to determine task-specific measurement uncertainties. This work reports on recent advancements extending the well-established method of PTB's Virtual Coordinate Measuring Machine (VCMM) to suit present-day needs in industrial applications. The VCMM utilizes numerical simulations to determine the task-specific measurement uncertainty incorporating broad knowledge about the contributions of, e.g., the used CMM, the environment and the workpiece.

A new procedure and reference standards for specifying the structural resolution in coordinate metrology traceable to the SI unit the metre are proposed. With the definition of the structural resolution, a significant gap will be closed to complete ‘acceptance and verification tests’ of the coordinate measuring systems (CMSs) which are specified in the ISO 10360 series dealing with tactile sensors, optical sensors, and x-ray computed tomography measurement systems (CTs). The proposed new procedure uses reference standards with circular rounded edges. The idea is to measure the radius of curvature on a calibrated round edge structure. From the deviation between the measured and the calibrated radius, an analogue Gaussian broadening of the measurement system is determined. This value is a well-defined and easy-to-apply measure to define the structural resolution for dimensional measurements. It is applicable to CMSs which are based on different sensing principles, e.g. tactile, optical and CT systems. On the other hand, it has a physical meaning similar to the classical optical point-spread function. It makes it possible to predict which smallest details the CMS is capable of measuring reliably for an arbitrary object shape. The theoretical background of the new procedure is given, an appropriate reference standard is described and comparative, quantitative measurement data of CMSs featuring different sensors are shown.

The German national metrology institute, the Physikalisch-Technische Bundesanstalt (PTB), has developed a novel calibration method for gear artefacts. This reduces the current calibration uncertainty of gear standards, which is an essential step towards meeting the rising quality demands of the gear manufacturing industry. The measurement setup is based on a coordinate measuring machine (CMM) equipped with a high-precision rotary table. The key element of the novel gear measuring device is a tracking interferometer (TI) for reading the distance information. This information is combined with the reading of the coordinate measuring machine line scales in order to reduce the overall measurement uncertainty. If an optimized measurement strategy is applied, the measurement results are almost achieved with laser interferometer accuracy. First simulations and measurement results for an involute profile artefact are presented and discussed.