Fine-textured parts are measured using stylus with very small diameter of its tip commensurable with the radius of parts mating.
Such parts are inspected at Lapic LLC using pointer stylus (with the stylus tip radius of 0.02 mm). It is impossible to reach perfect sphericity with such small parameters.
In this case, the measurement accuracy is reached as follows. As a result of the pointer stylus calibration, certain zones are determined which meet the precision sphericity requirements. Determination of stylus tip parameters allows us to measure parts with high accuracy (up to 1 microns) using the given program. During measurement the necessary condition is to contact the surface with the calibrated zones of the stylus tip (shown in red in the figure).
Since the calibrated zones can be arbitrarily located on the surface of the stylus tip, the inclination angle of the stylus during the contact with a part will be arbitrary as well. This is achieved owing to continuous control of carriage inclination of the six-axis CMM. When measuring during the contact the machine determines coordinates of the stylus tip center in space and circumscribes equidistant curve. Resulting line of the surface is defined by correcting this value by the radius value.