Coordinate measuring machines with rotary axes

All of the machine designs described so far allow the integration of rotary axes or rotary/tilt axes. This makes several views of the workpieces accessible to the sensors and the measuring objects can be measured all round in one clamping (Fig. 44). The position and movement of these axes and the workpieces are fully taken into account during measurement. It is therefore possible to measure features from different rotating and swivelling positions and to link the results in three dimensions.

The rotary axis can be integrated in both horizontal and vertical orientation. Machines with a horizontal rotary axis allow crane loading of large and heavy workpieces as well as easy handling of small rotationally symmetrical workpieces. For measuring long cylindrical workpieces, special coordinate measuring machines with an integrated vertical rotary axis and horizontally moving ram have proven their worth. This design allows the workpieces to be clamped vertically. The benefits are the avoidance of deflection of the measuring object, good accessibility, only an axial load when clamping between centres and the small space requirement for long parts.

The rotary table is positioned vertically together with the workpiece (x-direction). One or two rams are mounted together on a guide table (y-direction) and are moved with the sensors in the orientation of the horizontal axes (z-direction) (see Fig. 38f).

Machines with a horizontal ram can be designed with mechanical bearings for workshop measurement tasks (Fig. 45) or - e.g. for the measurement of precision tools - with air bearings (Fig. 46). This also applies to the rotary axes. With an air bearing, radial run-out errors of less than 0.1 µm can be achieved. For precise pitch measurements, such as on hobs, the rotary axis can be equipped with particularly accurate angle measuring systems. The machines are also available with two rams for multi-sensor applications.

This special machine design is used for the measurement of gears, shafts and cutting tools. The spectrum of shaft measurement ranges from motor and gear shafts to shafts for luxury watches. The measurements of all diameters, undercuts, flutes and running tolerances can be carried out without contact using the image processing sensor. Axial run-out measurements and measurements on bores and gears require tactile sensors. Fast complete measurement in one set-up is therefore only possible with multisensor coordinate measuring machines. When measuring tools, the focus is often on very precise measurement of the cutting edges or scanning the effective contour (seeMeasuring during movement, p. 95 f.) in relation to the tool shank with a vision sensor