Accessibility Analysis for Planning of Dimensional Inspection with Coordinate Measuring Machines

Steven N. Spitz, Antonia J. Spyridi, Aristides A. G. Requicha

Quality and process control activities in a mechanical product's life cycle require that components be measured, or dimensionally inspected. Computer-controlled dimensional inspection is typically performed with Coordinate Measuring Machines (CMMs), which are very precise Cartesian robots that use touch probes to measure the coordinates of points on a workpiece's surfaces. Automatic planning and programming of inspection tasks with a CMM involve spatial reasoning, to determine how to orient the part on the CMM, which probes to use, how to orient the probes, an so on. This paper introduces the notions of accessibility and approachability, which are important for inspection planning, and describes two sets of implemented algorithms for computing accessibility information. One of these sets of algorithms performs exact computations on polyhedral objects and is relatively slow, whereas the other uses discrete approximations and achieves high speed by exploiting standard computer graphics hardware. The discretized algorithm has been tested on real-world parts, and is sufficiently fast for industrial applications.