3D measuring probes can be used to quickly check the kinematic accuracy of a five axis milling machine. The principle is based on probing an accurate sphere with predefined and standard measuring cycles. The results are presented graphically and allow you to do a trend analysis of the machine’s accuracy within a defined time frame.
The basic components of this direct measuring principle include an integrated 3D measuring probe (not of a specific brand) and an accurate measuring sphere with known diameter mounted on a (standard) beam. The beam and sphere are mounted on a production machine table. Depending on the size of the milling machine, different sized beams can be used.
The full measuring procedure is based on +/- 7 predefined and standard measuring cycles. Before executing the cycles, the position of the measuring sphere’s midpoint (X, Y, Z) has to be defined as accurate as possible, and stored in the machine control. As the 3D measuring probe is responsible for the quality of the measurements, you should ideally ensure the eccentricity of the stylus is low. However, if your machine supports spindle orientation it will automatically be compensated for during the standard calibration cycle. Providing your probe performance test passes, the calibration remains valid for up to six months. In the next step we need to check probe performance: measuring accuracy, probe repeatability and probe load/unload. If there is not any important deviations, the procedure can be finalized with NC-Checker, checking the kinematic accuracy of your machine tool’s rotation axes. The measuring sphere will be probed at different angles of the rotation axes (eg each 15 or 45 degrees).
After completion of all measurements the results are presented visually, and the accuracy of the machine and probe performance is shown . This gives a strong indication if further actions are necessary. The closer the results to the nominal circle, the more accurate the results. By clicking on a specific measurement, the underlying details of that specific measurement are shown.
With regards to the precision manufacturing research project, Sirris can distribute both hardware and software until the end of October 2015. Companies who are interested can contact us for further information or a live demo on the 5-axis precision milling machine Fehlmann Picomax P825 Versa.
– Krist Mielnik, Sirris
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