Hybrid orbiting spindle for shaping non-circular holes
View Patent ↗A machine tool assembly includes a high speed rotating spindle for forming extremely precise surface contours on a work piece. The spindle is supported on a spherical air bearing about its center of gravity. The spindle can be rotated through an air turbine drive system incorporated into the spherical air bearing to eliminate any undesirable moments about an axis perpendicular to the long spindle axis. The spindle is adjustable in pitch and yaw directions through the influence of X-Y actuators. The X-Y actuation system is preferably electromagnetic and provides a non-contact method of displacing the spindle shaft in a controlled manner at any speed.
1. A machine tool assembly of the type having a pitch-and-yaw adjusting spindle for forming high-precision surface contours on a work piece, said assembly comprising:
a spindle defining a long axis and having a shaping tool extending from one end thereof, said spindle including a bearing journal;
a journal box at least partially enveloping said bearing journal for rotatably supporting said spindle;
a drive motor operatively interacting with said spindle for forcibly rotating said spindle about said long axis;
at least one X-Y actuator for controlling pitch and yaw of said spindle to move said shaping tool in a non-circular orbital path; and
said bearing journal and said journal box having concentric, generally spherical opposing surfaces centered about a center point intersecting said long axis of said spindle.
2. The assembly of claim 1 , wherein said X-Y actuator comprises a magnetic bearing cluster including at least three magnet stators spaced about said long axis.
3. The assembly of claim 2 , further including at least one position sensor for indicating the pitch and yaw of said spindle.
4. The assembly of claim 2 , wherein said magnetic bearing cluster includes a pair of opposing X-coordinate magnet stators and a pair of opposing Y-coordinate magnet stators, said X-coordinate magnet stators spaced between and generally co-planar with said Y-coordinate magnet stators.
5. The assembly of claim 4 , wherein said pair of opposing X-coordinate magnet stators and said pair of opposing Y-coordinate magnet stators disposed on respective opposite sides of said center point.
6. The assembly of claim 1 , wherein said journal box comprises an air bearing for producing a pressurized cushion of air against said bearing journal.
7. The assembly of claim 6 , wherein said journal box is porous.
8. The assembly of claim 1 , wherein said drive motor comprises an air turbine.
9. The assembly of claim 8 , wherein said air turbine includes an impeller disposed on said spindle and spaced from said bearing journal.
10. The assembly of claim 8 , wherein said air turbine includes an impeller disposed on said bearing journal.
11. The assembly of claim 10 , wherein said impeller is fabricated from a magnetically reactive material, said X-Y actuator comprising a magnetic bearing cluster including at least three magnet stators spaced proximate said impeller.
12. The assembly of claim 1 , wherein said drive motor is contained within said journal box.
13. The assembly of claim 1 , wherein said drive motor is disposed outside said journal box.
14. The assembly of claim 1 , further including a rotary position sensor for determining the angular position of said shaping tool about said long axis.
15. The assembly of claim 1 , wherein said shaping tool terminates in a plurality of point-like cutting edges disposed in generally equal accurate increments about said long axis.
16. The assembly of claim 1 , wherein said bearing journal is centered upon the center of gravity of said spindle.
17. A method for rotating a high-speed spindle assembly to form an irregular hole with a dimensionally varying axial trajectory in a work piece, said method comprising the steps of:
affixing a radially extending shaping tool to one end of a spindle having a long axis;
supporting the spindle for rotation about the long axis;
rotating the spindle about the long axis;
creating a magnetic field influencing at least part of the rotating spindle;
adjusting the yaw and pitch angulations of the long axis during rotation of the spindle by manipulating the magnetic field to thereby move the shaping tool in a predetermined non-circular orbital path;
and said step of supporting the spindle for rotation about the long axis further including confining the spindle in a spherical bearing centered about a center point intersecting the long axis of the spindle.
18. The method of claim 17 , wherein said step of supporting the spindle for rotation about the long axis further includes creating a cushion of air.
19. The method of claim 18 , wherein said step of creating a cushion of air includes pumping air through a porous journal box.
20. The method of claim 17 , wherein said step of rotating the spindle about the long axis includes turning an air turbine.
21. The method of claim 17 , wherein said step of confining the spindle in a spherical bearing includes centering the spherical bearing upon the center of gravity of the spindle.