Accessibility analysis for planning of dimensional inspection with coordinate measuring machines

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 me asuring machines (CMM's), 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 p robes to use, how to orient the probes, and so on, This paper introduces th e notions of accessibility and approachability, which are important for ins pection planning, and describes two sets of implemented algorithms for comp uting accessibility information, One of these sets of algorithms performs e xact computations on polyhedral objects and is relatively slow, whereas the other uses discrete approximations and achieves high speed by exploiting s tandard computer graphics hardware, The discretized algorithm has been test ed on real-world parts, and is sufficiently fast for industrial application s.