Model based NC programming for end milling operations

This paper describes a cutting simulation system and its application to NC programming of pocket operations. The cutting simulator has a function of physical simulation as well as geometric simulation. In the geometric simulation, changes in the geometry of workpieces are evaluated by means of a solid modeling system. In the physical simulation, various cutting state parameters such as cutting force, machining error and chatter vibration are evaluated based on cutting process models in addition to the results of the geometric simulation. The contour parallel tool path for pocket machining is generated by means of a Voronoi diagram of the machining area. Cutting conditions are selected on the basis of constraints on multiple cutting state parameters, such as average cutting torque, maximum cutting torque acting on a flute, machining error and chatter vibration. Based on an analysis of the effects of changes in the cutting conditions on the cutting state parameters, strategies to avoid violating the constraints are discussed. An algorithm of providing additional tool path segments is proposed to solve the problem of abrupt increase in the engage angle at corners, and their generation is demonstrated with an illustrative example.