Knowledge-based Optimisation of the Tactile Scanning Process on Cmm

− Today the scanning-technology on coordinate measuring machines (CMMs) is used for tactile detection of form deviations. Many companies apply CMMs instead of form measuring devices because of their high flexibility and the possibility of fast workpiece inspection. However, the kinematic of CMMs is more complex than the one of specialized form measurement devices. Dynamic effects, like centrifugal force of roundness measuring, result in a rising measurement uncertainty. The right setup of scanning parameters, like point density and scanning speed, is a challenging task. It is up to the machine operator because guidelines for the setup of optimal parameters do not exist. The dynamic characteristics of the used CMMs are not sufficiently identified and the detection of the measuring task dependent uncertainty is very complex. At the chair for Production Metrology and Quality Management of RWTH Aachen University the characteristic behaviour of tactile scanning CMMs are analysed. These studies built the basis for the practical and object oriented optimisation of the measurement strategy. An actual research project deals with the development of optimisation strategies by considering the maximum allowed measurement uncertainty. A knowledge-database was defined containing basic information about the used CMM, ranges for parameters and the main dynamic characteristics based on experiments.