The use of parallel mechanism micro-CMM in micrometrology

Over the past two decades there has been a surge in demand for accurate and precise 3D metrology machines to provide measurements in micron scale. This demand is encouraged by the need for quality and process control for the promised technological development of micro electromechanical systems (MEMS). Parallel mechanisms have been the subject of study as positioning machines. Parallel manipulators used as small scale coordinate measuring machine, micro-CMMs, to provide measurements with submicron accuracy for MEMS products with ever decreasing dimensions. This paper highlights some research activities in micro-CMMs. Initially, the advantages of the parallel mechanisms over their serial counterpart CMMs (such as high stiffness, high accuracy, and low inertia), as well as the disadvantages (such as complex forward kinematics, small workspace, complicated structures, and a high cost) are introduced. Then an identification of the major error sources in these structures is presented. Later, the kinematics and the concept of calibration is introduced. Additionally, the main characteristics of the existing methods of calibration and error compensation are discussed. Finally, concluding remarks concerning micro measurements using microCMMs are given. Keywordsmicro-CMM; parallel manipulator; micromeasurement.