Präzisionsprüfgerät für Nanomesstaster
Precision Test Equipment for Nano Gauging Probes Abstract Due to the increasing demands on the processing tolerance in manufacturing technology and on the miniaturization of industrial components, nanometrology is increasingly more important in manufacturing processes. Therefore, precise measuring instruments and sensors play a decisive role for the accurate characterization and inspection of products. For linear length inspection, highly accurate gauging probes, i.e. nano gauging probes, are of great importance. They possess a resolution within the nanometer range and have an accuracy of less than 100 nm. This group of precision gauging probes includes probes based on electronic as well as optical principles, e.g. inductive, incremental-optical or interference optical. To guarantee the accuracy and the traceability to the definition of the meter, calibration and test of nano gauging probes are necessary. Existing test methods and machines suffer from various disadvantages. Some permit only manual test procedures which are time-consuming, e.g. with high accurate gauge blocks as material measures. Other tests exhibit higher accuracy but are capable of measuring only in the micrometer range or result in uncertainties of more than 100 nm in the large measuring ranges. In order to make the test possible with a high resolution as well as a large measuring range, a precision test equipment for nano gauging probes was constructed, that with a resolution of 1.24 nm, a measuring range up to 20 mm (60 mm) and a measuring uncertainty of approx. ±10 nm can fulfill the requirements of high resolution within the nanometer range while simultaneously covering a large measuring range in the order of millimeters. This work is based on a calibration equipment for length sensors developed at the Institute of Process Measurement and Sensor Technology at the Ilmenau Technical University. The precision test equipment is equipped with a plane mirror interferometer. As a new approach for the avoidance of the Abbe error, a continuous angular control of the measuring body is realized with the help of piezo translators. Thus, during the test procedure, the measuring body reaches a tilt of less than 0.2" is reached and the Abbe error is minimized. A drive system consisting of ball guides, a fine thread spindle and a DC motor positions the measuring body. For the automation of the test procedure a measuring program adhering to the measurement principle outlined in VDI/VDE 2617 guideline was designed. With this program a gauging probe can be tested in less than thirty minutes with eleven measuring points and five repetitions. Theoretical and experimental investigations show that the precision test equipment has a test uncertainty of approx. ±10 nm at the measuring range of 18 mm, that corresponds to a relative uncertainty of approx. ±5·10-7. With small uncertainty, the minimization of the Abbe error and short test times this device can be regarded as an universal and efficient precision test equipment, which is available for the accurate test of arbitrary precision gauging probes and other linear length sensors.