A magnetically levitated high-speed spindle assembly (20) is provided for
forming non-circular holes (22) in workpieces (24) or non-circular
surfaces on pins. The non-circular holes (22) can be formed with
dimensionally varying axial trajectories at high speeds and with great
accuracy. This is accomplished by supporting a rotating spindle (26)
between first (58) and second (60) magnetic bearing clusters and
independently controlling these bearing clusters (58, 60) to move a
shaping tool (32) at the end of the spindle (26) in a predetermined
orbital path (B). A multiple input-multiple output control strategy is
used to control spindle (26) movements in the X and Y axes. The tilt
angle between the cutting edge (34) of the shaping tool (32) and the
orbital path (B) is maintained perpendicular under this multiple
input-multiple output control of the magnetic bearing clusters (58, 60)
to further improve shaping precision and spindle (26) stability during
high-speed operations.