INTEGRATED PRECISION INSPECTION SYSTEM FOR MANUFACTURING OF MOLDS HAVING CAD DEFINED FEATURES

An integrated precision inspection system has been developed for manuf acturing moulds having CAD defined features. The techniques of precisi on measurement are implemented for CAD/CAI integration for moulds havi ng sculptured surfaces with some basic features, such as, holes, slots and bosses. Features to be inspected are chosen in the CAD environmen t, and inspection planning is performed for each feature. The sampling -point strategies are: uniform distribution, curvature dependent distr ibution, or hybrid distribution of the two depending on the complexity of the sculptured surface. Line and plane features are divided into s ubintervals, and the measurement points are distributed at random posi tions in the subinterval. Prime number subintervals are considered for a circle feature, in order to avoid possible periodic distortion of t he measurement features. The measurement path planning is performed co nsidering collision avoidance and coordinate matching between the coor dinates. The output of the planning ir the machine code for a specific CMM having CNC capability. The machine code is downloaded to a specif ic CMM, and the measurement results are fed back to the computer. A ne w algorithm, called MINIMAXSURF, is developed to evaluate the form err or precisely for sculptured surfaces. The algorithm considers the radi us of the touch probe and evaluates the profile tolerance successfully by removing the unavoidable setup errors. The developed measurement s ystem has been applied to real moulds, demonstrating high performance and accuracy.