Pendulum grinding machine

A high efficiency method for grinding an elongated workpiece having a first workpiece surface which moves in a non-circular path as the workpiece is rotated about its elongated axis, the method comprising:

• providing a frame that supports one or more grinding wheel carriages;
• forming a machining space below the frame;
• mounting at least one grinding wheel carriage on the frame;
• mounting at least one pivot drive on the grinding wheel carriage, the at least one pivot drive having a pivot axis;
• depending at least one arm having an upper pivot end and a lower end from the pivot drive;
• coupling the upper pivot end of the at least one arm to the pivot drive;
• mounting a grinding wheel on the lower end of the at least one arm and positioning the grinding wheel in the machining space, the grinding wheel and the at least one arm having a center of mass that is spaced from the pivot axis, the grinding wheel having an axis of rotation that is parallel to the pivot axis, wherein the at least one arm and the grinding wheel comprises a pendulum assembly having a natural oscillation frequency about an equilibrium position determined by a length of the at least one arm measured from the pivot axis to the center of mass of the pendulum assembly;
• using the pivot drive to rock the at least one arm and the grinding wheel back and forth in a controlled manner about the pivot axis, whereby the at least one arm and the grinding wheel has a pendulum motion at said natural oscillation frequency as the pendulum assembly is displaced from its equilibrium position;
• supporting a headstock from the frame in the machining space, whereby the workpiece may be mounted in the headstock having an axis of rotation that is parallel to the pivot axis, rocking the grinding wheel back and forth equal angular distances about the equilibrium position in the machining space at the natural oscillation frequency to follow the non-circular path of the first workpiece surface while rotating the workpiece about its elongated axis, wherein the pendulum motion of the pendulum assembly at the natural oscillation frequency creates a pendulum gain.

A high efficiency grinding machine for grinding an elongated workpiece having a first workpiece surface which moves in a non-circular path as the workpiece is rotated about its elongated axis, the grinding machine comprising:

• a rectangular frame comprising first and second vertical supports which extend upward from a base and a horizontal beam having a length that joins an upper end of the first vertical support to an upper end of the second vertical support;
• a machining space formed below the horizontal beam and between the first and second vertical supports;
• at least one grinding wheel carriage mounted on the horizontal beam;
• at least one pivot drive mounted on the grinding wheel carriage, the at least one pivot drive includes a coaxial torque motor;
• at least one arm depending from the pivot drive, the at least one arm having an upper pivot end and a lower end, wherein the coaxial torque motor has a rotational output that is coaxial with a pivot axis and the upper pivot end rotates about the pivot axis;
• a grinding wheel mounted on the lower end of the at least one arm and positioned in the machining space, the grinding wheel and the at least one arm having a center of mass that is spaced from the pivot axis, the grinding wheel having an axis of rotation that is parallel to the horizontal beam;
• and
• a headstock supported by the horizontal beam in the machining space, whereby the workpiece may be mounted in the headstock having an axis of rotation that is parallel to the horizontal beam, wherein the at least one arm and the grinding wheel comprises a pendulum assembly having a natural oscillation frequency about an equilibrium position determined by the length of the at least one arm measured from the pivot axis to the center of mass of the pendulum assembly;
• wherein the pivot drive rocks the at least one arm and the grinding wheel back and forth in a controlled manner about the pivot axis, whereby the at least one arm and the grinding wheel has a pendulum motion at the natural oscillation frequency as the pendulum assembly is displaced from its equilibrium position;
• wherein the pivot drive rocks the grinding wheel back and forth equal angular distances about the equilibrium position in the machining space at the natural oscillation frequency of the pendulum assembly to follow the non-circular path of the first workpiece surface as the workpiece is rotated about its elongated axis.