A Constructive Solid Geometry (CSG) based process simulation system is developed for 2 1/2 axis milling. Along each path, the cutter is intersected with the individual geometric primitives describing the part. The cutter-part intersection data are then merged using the CSG part description tree, and retained to be accessed during the milling process simulation. Using the stored intersection data and an analytic reformulated mechanistic milling process model, the cutting forces and dimensional accuracy of the parts are simulated before the machining actually takes place. By using an inverse solution for the milling expressions, the feed rate is automatically scheduled to satisfy force, torque, and part dimensional error constraints. The accuracy and efficiency of the milling process simulation model are demonstrated experimentally.