  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.
