General Competition (December 1992)

Octahedral Hexapod Machine Development Program

Sponsor: Ingersoll Milling Machine Company

• Project Performance Period: 3/1/1993 - 2/28/1996
• Total project (est.): $3,509,693.00
• Requested ATP funds: $1,874,237.00

Machine tools, especially precision machine tools, are at the base of any country's manufacturing strength. Virtually every consumer product depends upon machine tools. At present, the United States imports many of its machine tools -- $1.6 billion worth in 1991 alone. Ingersoll proposes to combat this trend toward imported machine tools by developing the technology for a new class of high-precision machine tools based on a combination of two well-known mechanical principles: the "Stewart platform" and the octahedron frame. The Stewart platform, a floating base supported or suspended by six actuators, is familiar to several generations of pilots -- it was the basis for the design of the Link flight simulator. Independent control of the six actuators allows the Stewart platform to be positioned rigidly in virtually any orientation within its work volume. The octahedron, a regular geometric shape built from eight equilateral triangles, has the useful property that it provides the maximum possible stiffness for any given mass of material: forces applied at the vertices are distributed down the struts with no bending. In principle, a machine tool built with the drive spindle mounted on a Stewart platform suspended from the vertices of an octahedron might achieve far better performances than more conventional designs: 20 times the maximum acceleration rate, 6 times the machine stiffness, 10 times higher resonant frequencies, 5 times better positioning accuracy. Under the ATP award, Ingersoll will use a laboratory prototype Octahedral Hexapod Machine (which they are constructing with their own funding) to develop detailed baseline data on the performance of the design, and then try various enhancements for improving and measuring machine precision. The results could be used to design a future class of commercial machines based on the octahedral hexapod concept.

For project information:

Mary Lewis, (815) 987-6274

ATP Project Manager

Jack Boudreaux, (301) 975-3560
jack.boudreaux@nist.gov