The presented results are part of more extensive experiments, which aim to verify the reliability of the results provided by CAM systems in the production of parts with shaped surfaces. The article deals with the comparison of production times obtained from programming and simulation systems with real production times. For production planning and organization processes, information on estimated production time is an important input. A free-form sample was designed for the experiment. Finishing of the sample surfaces was accomplished by 3-axis and 5-axis milling using three different strategies. The machining times obtained by the simulation in the CAM system, the times from the simulation mode of the machine control system and the real machining times were evaluated. Data discrepancies were shown, with in almost all cases the real machining times being longer than the times given by the simulations. The results were supplemented by outputs from software that optimizes the feed during milling thus reducing the production time. The tests proved the validity of its use.