The article deals with the problem of improving the stability of quality parameters in the milling of molds, which provides for minimizing deviations from the set values that meet the requirements of the product drawing. For this purpose, a block diagram of the milling operation was developed and decomposition was carried out, which allowed to identify such subsystems, “workpiece”, “machine — tool”, “tool”, “contact zone”. The factors that lead to a decrease in the parameters of the quality of the surfaces of the workpiece are determined. The developed block diagram allowed to establish the relationship between the main components of the technological system and the characteristics of the machining process.