Development of a Super-Stiff, Vibration-Free Machine Tool
Develop a super-stiff, vibration-free milling machine to cut high-temperature alloys such as titanium and advanced technical ceramics such as aluminum oxide.
Sponsor: Rockford Engineering Associates LLC605 Fulton Avenue
Rockford, IL 61103
Today's manufacturers have to machine advanced materials that strain or exceed the capabilities of modern machine tools or use alternative processes, such as grinding, that are costly and time-consuming. These materials include high-temperature alloys such as the titanium alloys used in a variety of commercial products from aircraft parts to medical implants. Other difficult-to-cut materials are advanced technical ceramics, used in products such as lasers, semiconductors, bearings, and turbine blades. Conventional machining processes are constrained by the thermal limits of the cutting tool edge and the dynamic stability of the milling cutters and machine structure. As a result, material removal rates are low and tool consumption is high. Rockford Engineering Associates has proposed developing a three-axis, super-stiff, vibration-free (SSVF) milling machine to cut superhard and high-temperature alloys, which are the most difficult to machine using existing systems. The underlying innovation will be a unique, dynamically controlled hydrostatic bearing system that theoretically offers virtually infinite stiffness. Challenges in this design include control of fluid flow, shear, compressibility, mass, and temperature. The prototype milling machine will use dual-membrane-restrictor hydrostatic bearings for the linear axes and for the high-torque, low-speed spindle. The combination of the highest possible dynamic stiffness and damping ratio will allow the application of a new generation of hard and brittle cutting-tool materials that are expected to significantly increase machining efficiency. Metal removal rates should be improved by 50 to 100 percent, and the new technology is anticipated to be a major breakthrough in machining today's most difficult-to-cut materials. Initial applications of the technology could reduce the high cost of titanium components for commercial and military aircraft.