Soori, M., Arezoo, B. and Habibi, M., 2013. Dimensional and geometrical errors of three-axis CNC milling machines in a virtual machining system. Computer-Aided Design, 45(11), pp.1306-1313.Virtual machining systems are applying computers and different type of software in manufacturing and production in order to simulate and model errors of real environment in virtual reality system. Many errors of CNC machine tools have an effect on the accuracy and repeatability of part manufacturing. Some of these error can be reduced by controlling the machining process and environments parameters. However geometric errors which have a big portion of total error need more attention. In this paper virtual machining system which simulates the dimensional and geometrical errors of real three-axis milling machining operations is described. The system can read the machining codes of parts and enforce 21 errors associated with linear and rotational motion axes in order to generate new codes to represent actual machining operations. In order to validate the system free form profiles and surfaces of virtual and real machined parts are compared in order to present the reliability and accuracy of the software.