In this paper, an enhanced CAD/CAM system for simulating 3-axis milling of complex parts is proposed. The system consists of the conventional CAD/CAM system enhanced with a milling process simulator. The latter includes a geometric module and a physical module. The geometric simulator integrates solid, surface and curve modelling to accurately represent the geometric entities involved in the milling simulation and extract the geometric information required for predicting different process parameters. The physical simulator is composed of force models for flat and ball end mills which compute instantaneous cutting forces. The applicability of the approach is demonstrated for the case of 3-axis milling using a ball end tool. The validity is shown by predicting cutting forces and comparing them with experimental measurements. This system can be used to verify and optimize NC codes, thus contributing to improving the reliability, accuracy, and productivity of NC machining.