Development of a 3D Vibration Assisted Machining System

在加工过程中，工件与刀具之间的振动会影响加工精度和表面质量。然而，控制小振幅（几微米）高频率（几十千赫）的振动可以促进加工过程。这被称为振动辅助加工（VAM）。VAM将精密加工与刀具与工件之间的小振幅振动相结合，通过设置适当的加工参数和振动参数，使刀具周期性地与切屑失去接触，从而改变切削运动学和力学特性，提高加工性能。报告的好处包括：减少加工力；提高表面光洁度和成型精度；抑制毛刺的形成；减少刀具磨损，延长刀具寿命；等。在车削过程中，由于刀具是静止的，所以辅助振动比较容易实现。一维振动辅助系统，即切削方向上的直线振动辅助，以及二维振动辅助系统，即切削方向和切削方向深度平面上的椭圆振动运动，都已成功应用于车削加工中。由于铣削过程的运动学和动力学的复杂性，振动辅助在铣削中的应用很少受到重视。目前在振动辅助铣削方面的努力纯粹是经验的，缺乏精确的运动学和动力学模型来设计最优的VAM系统，而且所有的二维振动辅助铣削研究都局限于低频，不适用于微铣削作业。此外，为了获得复杂的几何形状，铣削过程需要在空间上任意方向的进给矢量，即三维端铣削需要进给矢量的垂直和水平分量。然而，目前还没有3D VAM系统的报道。为了克服这些限制，利用振动辅助的优势，本项目将开发一种新型紧凑的三维振动辅助加工系统，用于难加工材料的自由曲面的微铣削，并通过加工实验评估其性能。从半导体材料、压电材料、玻璃等难以加工的材料制造精密微产品，在生物工程、MEMS、光学等各种应用领域的需求日益增长。该项目的成功将为以更具成本效益的方式加工这类材料开辟新的工业途径。然而，为了在实践中实现这一目标，迫切需要开发三维振动辅助加工系统及其相关的设计和建模方法。

Vibrations between the workpiece and the cutting tools in machining processes can deteriorate machining accuracy and surface quality. However controlled small amplitude (several microns) high frequency (tens of kHz) vibrations can facilitate machining processes. This is called vibration assisted machining (VAM). VAM combines precision machining with small amplitude vibration between tool and workpiece, and for appropriate machining and vibration parameter sets, the tool can periodically loses contact with the chip, which changes the cutting kinematics and mechanics, and can improve machining performance. Reported benefits include: reductions in machining forces; improved surface finish and form accuracy; suppression of burr formation; reduction of tool wear and extension of tool life; etc. In turning process, the vibration assistance is relatively easy to implement as the tool is stationary. Both 1D vibration assisted system, i.e. linear vibration assistance in the cutting direction, and 2D vibration assisted system, i.e. elliptical vibration motion in the plane of cutting direction and depth of cut direction have been applied in turning processes with success. Due to the complexity of kinematics and dynamics of the milling process, application of vibration assistance to milling has received little attention. Currently efforts on vibration assisted milling are purely empirical and lack accurate kinematic and dynamic models to design an optimal VAM system, and all 2D vibration assisted milling studies have been limited to low frequencies which are not applicable to micro milling operations. In addition, to obtain complex shape geometry, the milling process requires a feed vector in arbitrary direction in space, i.e. both a vertical and horizontal components of feed vector are necessary for 3D end milling. However, currently no 3D VAM systems have been reported. To overcome these limitations on the state-of-the-art and make use of the advantages of vibration assistance, this project will develop a novel compact 3D vibration assisted machining system for micro milling of free-form surfaces on hard-to-machine materials, and evaluate its performance through machining experiments. Fabrication of precision micro products from hard-to-machine materials, such as semiconductor materials, piezoelectric materials, glasses, is increasingly in demand in various applications such as bio-engineering, MEMS, optics, etc. Success of the project would open new industrial avenues for processing such materials at a more cost-effective manner. However, to achieve this in practice, development of a 3D vibration assisted machining system and its associated design and modelling methodology are urgently needed.