An Innovative Concept for a Universal Drill Point Grinder Based on a Hexapod Mechanism

钻床约占全世界刀具总数的60%。钻探作业产生的芯片约占所有金属切割芯片的四分之三。波音737飞机的结构需要钻200多万个孔。一个典型的汽车发动机厂每天钻30万个孔。这些简单的事实表明，钻井作业在制造业中扮演着至关重要的角色。全球竞争增加了对美国制造业的需求，要求它们以更低的成本生产高质量的产品。因此，提高钻井效率和质量对美国制造商保持竞争力变得越来越重要。Robotronics，Inc.计划研究可行性，并建立一个基于六足机构的六自由度(DOF)万能钻尖磨床原型(也以其原始发明者的名字命名为Stewart平台)。钻尖的磨削或磨削需要一台灵巧、高精度、刚性大的机床。虽然磨削加工所需的工作包络相对较小，但万能钻尖磨床需要能够产生六个空间自由度的运动轨迹。Hexapod Drill Point Grinder(HDPG)有望实现磨削工具的跨越式发展，显著提高钻井作业的质量、效率和精度。高效的六足桁架式设计为给定质量提供了最坚固的机械系统。基于六足的机床基本上是六自由度的，因此它几乎可以加工任何曲面。与传统的串联结构相比，刚度增加了，因为载荷在所有的连杆之间分配，精度也提高了，因为腿长误差趋于平均，从而降低了最终误差。作为机械加工载荷的结果施加到执行器上的力都是轴向力(拉力和压力)，没有任何弯矩。六足机器人在机械上比同等能力的串联连杆机构更简单。由于机械简单，基于六足动物的机床应该比相同能力的传统机床成本更低。

Drilling machines represent about 60% of the total number of cutting tools throughout the world. The drilling operation generates about three quarters of all chips made in metal cutting. More than two million holes need to be drilled in a Boeing 737 aircraft structure. A typical automotive engine plant drills 300,000 holes daily. These simple facts indicate the crucial role that drilling operation plays in manufacturing. Global competition has increased demands on U.S. manufacturing sectors to produce high quality products at lower costs. Therefore, enhancement of drilling efficiency and quality is becoming increasingly important for U.S. manufacturers to remain competitive. Robotronics, Inc., proposes to study the feasibility and build a prototype of a six degree-of-freedom (DOF) universal drill point grinding machine based on the Hexapod mechanism (also called a Stewart Platform after its original inventor). The grinding or sharpening of drill points requires a dexterous and high precision machine tool with great stiffness. While the work envelope required by the grinding operation is relatively small, a universal drill point grinder needs to be able to generate motion trajectory with six spatial DOF. The Hexapod Drill Point Grinder (HDPG) promises a leapfrog advancement in grinding tools which can significantly improve the quality, efficiency, and precision of drilling operations. The efficient truss type design of the Hexapod provides the stiffest mechanical system for a given mass. The hexapod-based machine tool is fundamentally six DOF, hence it can machine virtually any surface. Stiffness is increased over its conventional serial counterparts because the loads are divided among all of the links, and accuracy is increased because leg length errors tend to average and therefore decrease the final error. The forces applied to actuators as the result of machining loads are all axial forces (tension and compression) without any bending moments. A hexapod is mechanically simpler than an equally capable serial link mechanism. Because of their mechanical simplicity, Hexapod-based machine tools should be less costly than conventional machines of the same capability.