Integrated modeling and analysis of ball screw feed system and milling process with consideration of multi-excitation effect

- An integrated modeling method of ball screw feed system and milling process is proposed.
- The forming mechanism of a new kind of quality defect shown as contour low frequency oscillation is explained.
- An analytical model of motor torque with multi-frequency harmonics is presented.
- The characteristics of contour oscillation under different milling condition are discussed.
- An efficient experiment modal method considering rotational-DOF of ball screw feed system is given.

The present researches about feed drive system and milling process are almost independent with each other, and ignore the interaction between the two parts, especially the influence of nonideal motion of feed drive system on milling process. An integrated modeling method of ball screw feed system and milling process with multi-excitation effect is proposed in this paper. In the integrated model, firstly an analytical model of motor harmonic torque with consideration of asymmetrical drive circuit and asymmetrical permanent magnet is given. Then, the numerical simulation procedure of cutter/workpiece engagement during milling process with displacement fluctuation induced by harmonic torque is put forward, which is followed by the solving flow for the proposed integrated model. Based on the integrated model, a new kind of quality defect shown as contour low frequency oscillation on machined surface is studied by experiments and simulations. The results demonstrate that the forming mechanism of the contour oscillation can be ascribed to the multi-excitation effect with motor harmonic torque and milling force. Moreover, the influence of different milling conditions on the contour oscillation characteristics, particularly on surface roughness, are further discussed. The results indicate that it is necessary to explain the cause of the new kind of quality defect with a view of system integration.