Selective measuring of freeform surfaces for quality control and selective maintenance of bending tools

Bending tools are frequently used to manufacture freeform surfaces. In such cases, the geometry of the workpiece is determined wholly or in part by that of the tool (e.g. die forming). The quality of the finished product depends largely, therefore, on the geometry of the tools. Tool geometry is changed in the course of the manufacturing process by wear and optimisation. When the time comes for repairs or the manufacture of new tools, there is no record of the geometrical modifications which have been carried out. A model in the form of a quality control loop to feed back geometrical modifications to CAD and CAM systems is presented in this contribution. A means of creating the individual components in the quality control loop is described. Particular care has been taken to ensure that both the measurement and the feedback are limited to selected areas in order to minimise the cost and time involved.