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

钻床约占全世界切削工具总数的60%。在金属切削加工中，大约四分之三的切屑是由钻孔加工产生的。一架波音737飞机的结构需要钻200多万个孔。一个典型的汽车发动机工厂每天要钻30万个孔。这些简单的事实表明，钻井作业在制造业中起着至关重要的作用。全球竞争增加了对美国制造业以更低成本生产高质量产品的要求。因此，提高钻井效率和质量对于美国制造商保持竞争力变得越来越重要。Robotronics, Inc.提议研究基于六足机构（也称为Stewart平台）的六自由度万能钻点磨床的可行性并构建原型机。钻尖的磨削或锐化需要一个灵巧、高精度、刚度大的机床。虽然磨削作业所需的工作范围相对较小，但通用钻点磨床需要能够产生具有六个空间自由度的运动轨迹。六足钻点磨床（HDPG）有望实现磨削工具的跨越式发展，可以显著提高钻井作业的质量、效率和精度。六足机构的高效桁架式设计提供了给定质量下最刚性的机械系统。基于六足的机床基本上是六个自由度，因此它可以加工几乎任何表面。由于载荷在所有连杆之间分配，因此刚度比传统的串行对偶件增加，并且由于腿长误差趋于平均，因此精度增加，从而减少了最终误差。作为加工载荷的结果，施加在执行器上的力都是轴向力（拉力和压缩力），没有任何弯矩。六足机构在机械上比同等功能的串行连杆机构简单。由于其机械简单，基于六足的机床应该比同等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.