Determination of cutting conditions for the stable milling of flexible parts by means of a three-dimensional dynamic model

In this paper, a three-dimensional dynamic model for the prediction of the stability lobes of high speed milling is presented considering the combined flexibility of both tool and workpiece. The aim is to avoid chatter vibrations in the finish milling of aeronautical parts that include thin walls and thin floors, taking into account the variation of the dynamic properties of the workpiece during machining. Hence, the accurate selection of both axial depth of cut and spindle speed can be accomplished. The model has been validated by means of a test device that simulates the behaviour of a thin floor. The following methodology is applied: first, a modal analysis of the test device is performed, second, stability lobes are calculated, and finally, a milling test validate the approach. Vibration signals from machining have been analysed to detect the chatter vibrations. The lobes diagrams obtained considering only the machine or only the tool are not in touch with reality; only through consideration of the relative frequency response function, the real borderline of stability can be obtained.