Abstract: To solve the instantaneous geometric boundary parameters applied in hobbing force model， a method of simulation calculation of undeformed chip thickness based on the 3D solid modeling was presented. The undeformed chip， which is the intersection between swept volume of hob and workpiece， contains the information of geometric boundary parameters. Boolean operation is used to acquire the undeformed chip. By means of intersection operations on the rake plane of instantaneous hob teeth and the geometric entities of chip， CWE (cutter/workpiece engagement) that includes the information of cutting range constructed by the splines， was obtained. The undeformed chip thickness was extracted from CWE. This method lays a foundation for the precise prediction of dynamic hobbing force.

Key words: 3D solid modeling, hobbing force, undeformed chip, CWE(cutter/workpiece engagement), geometric boundary parameters, cutting thickness