3D Shaping with Tertiary Tool Motion

本研究项目的两个目标是：(1)构思一种同时控制三维自由曲面表面形貌的超精密微/细观加工方法；(2)为加工运动学和切割力学建立分析基础。在该方法中，刀具的一次和二次运动由三次运动分量补充，该三次运动分量由超声频率下受控的小幅度闭合轨迹运动组成。对于第三次动议的产生，将探索两种替代方案。第一种是基于压电驱动的二维弯曲设计，而第二种是基于可调谐的超声椭圆振荡器。辅助理论工作将重点放在机器命令序列的分析公式上，以便在表面上生成所需的拓扑特征。最初，这将通过几何和运动学考虑来实现，后来扩展到包括与切割力学相关的影响，如弹性和塑性变形、最小切屑厚度影响和其他影响。样机将在不同的切割方案下进行设计、制造和测试，这些方案在常规切割和延性切割条件下实施。如果成功，新构思的微切削工艺将提供目前竞争对手无法实现的能力。它的优点是：(1)非常高的切割速度，(2)能够通过对运动部件进行调制和相位来传递复杂的表面图案，以及(3)创建具有可控地形的雕塑曲面。该方法还提供了一种替代微端铣削的方法，并消除了对超高速低跳动主轴的需求。从科学的角度来看，理论、计算和实验方法的结合将提供对开发的机器的能力和它执行的新过程的基本理解。由于微制造是一个相当新的研究领域，通过本研究创建的知识库和机器原型将为继续探索微/中尺度切割过程提供必要的教育和物理基础设施。

The two objectives of this research project are: (1) to conceive an ultra-precision micro/meso-scale machining method for a subclass of three-dimensional free-form surfaces with the concurrent control of their surface topography, and (2) to establish the analytical basis for the process kinematics and cutting mechanics. In the proposed method, primary and secondary motions of a cutting tool are supplemented by a tertiary motion component consisting of controlled small-amplitude closed trajectory motions at ultrasonic frequencies. For the generation of the tertiary motion two alternatives will be explored. The first is based on a piezo-driven two-dimensional flexure design, while the second on a tunable ultrasonic elliptical oscillator. Supporting theoretical work will focus on the analytical formulation of the machine's command sequences for the generation of desired topological features on the surface. Initially, this will be accomplished through geometric and kinematic considerations and later extended to include cutting mechanics related effects such as elastic and plastic deformation, minimum chip thickness influences and others. A prototype machine will be designed, manufactured and tested under different cutting scenarios implemented in conventional and ductile cutting regimes. If successful, the newly conceived micro-cutting process will offer capabilities that cannot be achieved by current competing operations. Its advantages are: (1) very high cutting velocities, (2) ability to impart intricate surface patterns by modulating and phasing the motion components, and (3) creation of sculptured surfaces with controlled topography. The method also offers an alternative to micro-endmilling and eliminates the need for ultra-high-speed low runout spindles. From the scientific standpoint, the combination of theoretical, computational, and experimental methodologies will provide the fundamental understanding of the developed machine's capabilities and of the new processes it executes. Since micro-manufacturing is a fairly new research area, the knowledge base and machine prototype created through this research will provide the necessary educational and physical infrastructure for continued exploration of micro/meso-scale cutting processes.