Development of a 3D Vibration Assisted Machining System

在加工过程中，工件和刀具之间的振动会降低加工精度和表面质量。然而，受控的小振幅（几微米）高频（几十kHz）振动可以促进加工过程。这被称为振动辅助加工（VAM）。VAM将精密加工与刀具和工件之间的小幅振动结合起来，通过适当的加工和振动参数设置，刀具可以周期性地与切屑脱离接触，从而改变切削运动学和力学，提高加工性能。报告的效益包括：减少加工力;提高表面光洁度和形状精度;抑制毛刺的形成;减少刀具磨损和延长刀具寿命;等等。在车削过程中，由于刀具是静止的，所以振动辅助相对容易实施。一维振动辅助系统（即沿切削方向的线性振动辅助）和二维振动辅助系统（即沿切削方向和切削深度方向的平面内的椭圆振动运动）都已成功地应用于车削工艺中。由于铣削过程运动学和动力学的复杂性，振动辅助铣削的应用很少受到关注。目前，振动辅助铣削的努力是纯粹的经验和缺乏准确的运动学和动力学模型来设计一个最佳的VAM系统，和所有的二维振动辅助铣削研究已被限制在低频率，这是不适用于微铣削操作。此外，为了获得复杂的形状几何形状，铣削过程需要在空间中的任意方向上的进给矢量，即，进给矢量的垂直分量和水平分量对于3D端铣都是必要的。然而，目前还没有3D VAM系统的报道。为了克服现有技术的这些局限性，并利用振动辅助的优点，本项目将开发一种新型的紧凑型三维振动辅助加工系统，用于难加工材料上的自由曲面的微铣削，并通过加工实验评估其性能。从难以加工的材料，如半导体材料，压电材料，玻璃，精密微型产品的制造越来越多地在各种应用中的需求，如生物工程，MEMS，光学等，该项目的成功将开辟新的工业途径，以更符合成本效益的方式处理这些材料。然而，为了实现这一点，在实践中，三维振动辅助加工系统及其相关的设计和建模方法的发展是迫切需要的。

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.