The motive behind the effort to make virtual prototyping more sophisticated is first of all cost reduction of manufacturing machine design, followed by reduction of lead time for development, prototyping and testing of the pre-manufacturing machine series. This article deals with the analysis of manufacturing precision of a 3-axial, numerically controlled milling machine. The methodology for precision analysis rests on a selected simplified numerical calculation model of a manufacturing machine on which virtual machining has been conducted. The mechanical inaccuracy itself is calculated by computer via the FEM analysis. The results are processed for visualization by the Excel software.