The design of a six-axis articulate machine for three-dimension coordinate measuring is studied in this research. The study includes mechanism design, kinematics design, and calibration technique. The coordinate measuring machine is developed for the reverse engineering application. The target accuracy is approximately better than 100 micrometers for 500x500x300 cubic-millimeter workspace. The very high resolution optical rotary encoder installed at each arm joint is used for measuring the joint angles. By knowing the joint angles, probe length, and the structure of the homogeneous transformation, the unknown parameters of the arm configuration can be solved numerically by using nonlinear regression. The unknown parameters are for obtaining the homogeneous transformation of the arm using in the measurement. The measured coordinate data can be interfaced with commercial CAD packages (such as CATIA) by using a neutral file format, CGO_ASCII format. The accuracy of the machine is tested by measuring the distance of the two calibrating sphere locations, using the center point of the sphere as the reference point. The 300 points are used in the calibration procedure, and the other 50 points for evaluating the accuracy. The result shown that accuracy of 100 micrometer is promising.
