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PicoScale High Speed Measurements

Today’s quality control standards stipulate an ever increasing precision of milled or otherwise produced parts. To achieve this precision, the errors and deviations of the production tools have to be measured with extremely high accuracy. Furthermore, the measurements have to be carried out with high bandwidths in order to discern aberrations at high frequencies. The PicoScale interferometer is ideally suited for this task.

Setup

On the right hand side, the setup of an interferometer head and object mirror designed to measure the velocity of a milling tool and at the same time oscillations that occur in the setup is shown. The object mirror was mounted below the spindle of the milling tool. The whole tool was moved by 225 mm with the maximum speed specified by the manufacturer of 1 m/s. The velocities were calculated by the PicoScale interferometer in real time, and streamed alongside the position data. In this case, the streaming frequency was set to 9770 Hz, corresponding to one datapoint each 100 µs.

Results

The results of the measurement are shown on the right hand side. The velocity changes between 1 m/s and -1 m/s as the tool moves back and forth. The smaller graph in the inset shows that not only macroscopic translations can be measured, but at the same time microscopic oscillations are visible, which are induced in the mirror mount by the acceleration and deceleration of the tool. The standard graphical user interface PicoScale Control is also capable of calculating the FFT of the position data. Thereby, vibration amplitudes and frequencies can be immediately seen in real time during the measurement.

Summary

It has been shown that the PicoScale interferometer can accurately measure velocities of 1 m/s over a working range spanning 225 mm. The measurement could thus successfully verify the speed specification of the milling tool machine. Vibrations in the µm range were measured at the same time. The bandwidth of the measurement was in the range of 10 kHz, but could also be increased to the MHz range in order to reveal even higher vibration frequencies.