Technology and use of coordinate measuring machines

In the field of macro-geometric dimensional control, coordinate-based coordinate measuring machines (CMMs) came into their own in the 1970s. Classically, they are essentially composed of a mechanical structure guiding a mechanical probe which, on contact with a surface, electronically triggers the measurement of its position in a Cartesian coordinate system. CMMs can thus provide a "digital image" of a physical object's surfaces, based on a set of point clouds. Software processing of the information acquired in this way enables the measurement of dimensional and three-dimensional geometrical characteristics, which can comply with various ISO-GPS (Geometrical Product Specification) standards.

Over the last ten years or so, CMMs have undergone a new technological evolution, linked to the use of increasingly high-performance non-contact optical measurement sensors. It is now more appropriate to speak of "3D measurement systems", in which coordinate CMMs make their contribution to a highly diversified technological offering in which the CMM itself can be replaced by an optical measurement system (optical CMM).

After outlining the main criteria for choosing a 3D measurement system, we'll focus more specifically on the technologies associated with coordinate CMMs, providing the metrological foundations common to the various systems.