Simulation-aided computed tomography (CT) for dimensional measurements

Carrying out dimensional measurements by CT means assess ing coordinates in space. CT must therefore be treated as a coordinate measuring technique similar to optical or tactile Coordinate Measuring Machines (CMMs). The well-established standards and guidelin es for the acceptanceand verificationtesting of CMMs require the use of calibrated reference s tandards to achieve measurement machine characteristics. Hence, transferring these concepts from coordinate metr ology to CT, a dedicated CT-specific reference standard was designed, manufactured and calibrated using a tactile CMM. For comparison purposes, a CAD model was created by reverse engineering using the cal ibration data. The calibrated model was fed into a virtual CT and the measurement process was sim ulated. The reference standard was measured by micro-CT. By comparing the characteristics of the measurement output of CT and the output gained from simulation, the influences of measurement artefacts can be judged, for the fi st time, in analogy to existing guidelines of coordinate metrology.