Traceable Measurements on Machine Tools - Thermal Influences on Machine Tool Structure and Measurement Uncertainty

Flexible manufacturing processes for high quality products at low costs are one of the main research objectives in the field of production technology. The quality inspection of large or complex workpieces manufactured on machine tools often takes place beside the production line. To assure the traceability of the quality inspection the features are measured on a CMM. The manufacturing process is interrupted and transportation, handling and the loss of the original manufacturing setup influence the workpiece quality. The high invest and the mentioned aspects show the need for an machine integrated traceable measuring process.Integrated touch probes can be found in many new machine tools and shall provide the possibility of testing product characteristics right after the manufacturing process in the original setup on the machine tool. Due to disturbances like machine defects or temperature fluctuations of the surrounding, the measurement process is not traceable and the data cannot be used for a process improvement or process control.New Approaches at WZL are aiming to assure the traceability of the inspection processes on machine tools. The fusion of appropriate methods for the traceability of CMM's and innovative calibration methods for machine tools allow the determination of a measurement uncertainty for the measurement system “touch probe and machine tool”. Different methods known from CMMs have been examined and validated for machine tools. As the main influence for deviations of the workpiece quality seems to be the temperature, the impacts of the surrounding temperature on the machine tool structure and the achievable measurement uncertainty was examined in a temperature controlled surrounding. The thermal effects on the tool structure shown by repetitive calibrations can now be directly linked to the measurement uncertainty.The objectives of the research activities are part of the Cluster of Excellence ‘Integrative Production Technology for high Wage Countries’ at the RWTH Aachen.