| Nowadays, the requirements of miniature and micro parts have an increasing growth in the academic and industrial fields. The micro-manufacturing is the enabling technology for the fabrication of miniature and micro parts. The conventional micro manufacturing technology, Micro-Electro-Mechanical System (MEMS), has limitations in the manufacturing of workpieces with various materials and complex shapes. However, the micro-cutting technology can fabricate micro components with 3D free form surfaces and various engineering materials, and fill the gap between micro/nano and macro domain. In addition, vibration-assisted machining (VAM) has been widely applied in the fabrication of micro parts as its perfect cutting performance. As a result, VAM is applied in micro milling forming two-dimensional vibration-assisted micro milling (2D VAMM) in order to improve the machining quality, extend tool life and meet the fabrication demands of micro parts with different materials. In the paper, the cutting mechanisms and key technologies on 2D VAMM, such as kinematics, cutting force, machined surface quality, burr formation and tool life, have been investigated.The tool tip trajectory relative to the workpiece becomes very complex due to the two-dimensional vibrations of the workpiece, which causes the chip thickness formation to be distinct from that in conventional micro milling. In this paper, the tool tip cutting path and the chip thickness computation model are established, with which the characteristics of the cutting path and the chip thickness are studied. It's found that the cutting path varies greatly with different machining and vibration parameters, and the chip thickness in 2D VAMM is influenced not only by one precious cutting, but also by several previous cuttings. Furthermore, 2D VAMM is an interrupted cutting process since the tool could not remove materials in the cutting area. Therefore, two evaluating indicators, free time ratio (FTR) and amplitude ratio (AR), are defined to analyze the effects of cutting parameters on the chip thickness.The cutting force is critical to understand the cutting mechanisms, optimize appropriate cutting conditions and monitor the cutting process. A 3D mechanical cutting force model is proposed based on the shear and slip-line field method, in which the tool edge radius and elastic restitution in the ploughing field are taken into consideration. The cutting force model utilizes the proposed instantaneous undeformed chip thickness model to represent the real trajectory of the tool tip in 2D VAMM, and is integrated with the cutting process dynamic response model. The simulated cutting force has good agreement with the experimental data. And the influence of cutting conditions on the cutting force is analyzed using the simulations. The machined surface roughness is a significant parameter for the evaluation of the surface quality. Based on the truth that machined surface is generated by duplicating the tool profile on the workpiece surface, the surface topography integrated simulation model is established considering tool tip cutting path interference and the cutting process dynamic response. The experiments are carried out to verify the simulation model. And the roughness prediction mathematic expression is obtained using Response Surface Method (RSM) based on the experimental data, with which the effects of cutting conditions on the surface roughness are investigated. It's found that feed per tooth, amplitude, frequency and spindle speed have significant effects on the surface roughness, and 2D VAMM can decrease the surface roughness so as to improve the machined surface quality.Burr affects the machining quality significantly in micro milling process. In the paper, 2D VAMM is used to machine micro slot, the top burr on the side of micro slot is observed and measured with microscope, and the effects of cutting conditions on the top burr are studied. Finally, the influence of size effect on top burr formation is used to interpret the top burr formation in 2D VAMM. It's concluded that 2D VAMM can weaken the size effect and decrease the compression and friction between the workpiece and tool so as to control the burr formation and reduce the top burr size.The investigation on micro-tool's wear mechanisms is helpful to understand micro-tool's wear reasons, improve its machinability, and prolong the tool life. 2D VAMM is applied to machine aluminum alloy and two different hardness tool steel (HRC55 and HRC58), and the tool flank wear is observed and measured. And the effects of cutting parameters on tool flank wear are studied through the tool wear experiment. It's found that 2D VAMM can reduce tool flank wear, and the smaller amplitude and lower frequency are helpful to reduce tool wear.
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