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.
