US 4,761,876 A · High speed precision drilling system

Abstract

A high speed drilling system is disclosed for high speed drilling of very small holes in workpieces such as printed circuit boards. The X-Y positioning system includes air bearings to provide lift between the stationary guide beams, the crossbeam and the top table, and further includes a vacuum preloading apparatus for providing a preloading force between the table and the guide beam. The preload force dampens Z axis oscillations which can result in drill bit breakage. The top table is a lightweight honeycomb structure, whose effective rigidity is virtually that of the guide beam due to the vacuum preloading. The system includes pairs of spindles, one a conventional spindle for drilling holes larger than about 0.125 inches, and the other a high speed spindle for drilling holes in the range of about 0.003 to 0.125 inches. The high speed spindle includes a stationary spindle body carrying the stator of the rotary drive motor. Only the spindle rotor is translated along the Z axis to perform the drilling movements. The rotor is supported within the spindle body by rotary and linear air bearings, and is axially driven by a linear motor. A toolchanger loaded by clips carrying the drilling bits is mounted on the top work table, and minimizes the time required to change drilling tools. The clips minimize the manual handling of the fragile drill bits. A vacuum hold-down apparatus is employed to secure the workpieces to a drilling station.

Claims58

Dependent claims

A high-speed precision drilling system for positioning a workpiece along at least one axis in relation to a drilling spindle, comprising:

a first beam member having a planar first surface region;
a work table having a planar second surface region juxtaposed with said first beam member such that said surface regions are adjacent one another, said table arranged to carry said workpiece for operations thereon by the drilling spindle;
means for providing a distributed air bearing between said planar surface regions providing distributed separation forces to separate said surface regions and to support the work table over a substantial portion of the area carrying the workpiece;
at least one drilling spindle supported on a support structure separated from said work table for carrying a drilling tool, said drilling spindle comprising means for feeding said drilling tool into and out of a workpiece secured to said table while the drilling tool is rotated at high speed;
translating means for translating said table along a first axis in relation to said guide beam;
and
preloading means for exerting preloading forces distributed between said planar surface regions and opposing the separating forces provided by said air bearing means, tending to draw said surface regions of said table and beam members together without overcoming the separation forces applied by the air bearing, thereby damping vibrations in the work table caused by said translation or operation of said drilling machine.

4 more elements

A planar positioning system for positioning a workpiece on a plane in relation to a machine tool, comprising:

a stationary guide beam having a planar upper surface region;
a crossbeam having planar upper and lower surfaces and arranged over said guide beam;
first means for providing a distributed air bearing between said planar upper surface region of said guide beam and said lower planar surface region of said crossbeam;
first translating means for translating said crossbeam along a first axis in relation to said guide beam;
an upper work table disposed over said crossbeam and said guide beam and having a lower planar surface region, said work table arranged to carry said workpiece;
second means for providing a distributed air bearing between the opposing areas of said upper surface region of said crossbeam and said planar lower surface region of said table;
second translating means for translating said work table in relation to said crossbeam along a second axis;
and
vacuum preloading means for exerting preloading forces tending to draw said work table and said guide beams together in opposition to the lift provided by said respective first and second air bearing means, thereby damping vibrations in the work table caused by operation of said machine tool.

6 more elements

A high leverage centrifugal chuck assembly for gripping a drill tool in a high speed drilling spindle, comprising:

a chuck structure having an interior opening formed therein to accept the shank of a drill tool and comprising gripping means for firmly gripping said shank only during dynamic, high speed rotation of said chuck structure, said gripping means for applying sufficient gripping forces as a result of centrifugal forces to firmly grip said shank during dynamic operation, while applying little or no gripping pressure during static conditions, said means comprising:
(i) at least one pair of opposed jaw members each comprising a jaw surface partially defining a circumferential region of said opening for contacting said shank;
(ii) at least one pair of opposed lever arm members corresponding to said jaw members and extending along and adjacent to said opening;
and
(iii) a fulcrum region encircling said opening between said jaw members and said lever arm members, said fulcrum region between each of said corresponding jaw members and said lever arms such that as said respective lever arm members are urged outwardly from said opening, reactive forces are transmitted through said fulcrum region tending to urge said jaw members inwardly to grip said drill tool shank;
and
(iv) means for positioning the chuck in concentricity with a spindle drilling axis and for aligning the tool shank with said drilling axis;
whereby as said chuck is rotated at high speeds with a drill bit shank inserted in the chuck assembly, centrifugal forces urge said chuck lever arms outwardly, causing the jaws to grip the shank securely and concentrically with the drilling axis.

5 more elements

A high speed drilling spindle, comprising:

a spindle shaft having a shaft axis;
means for driving said shaft at high rotational speeds;
and
a centrifugal chuck assembly for securing a drilling tool to said shaft in alignment with the spindle axis during spindle rotation, comprising:
(i) a tool alignment bushing comprising a bore for receiving the inserted end of a drilling tool shank, the bushing mounted in said spindle such that said bore is aligned with said shaft axis;
(ii) a unitary chuck structure mounted adjacent the tool end of the spindle shaft and having an interior opening formed therethrough to accept said shank, said chuck structure for developing the gripping forces securing the shank by centrifugal forces and for substantially releasing said gripping forces when the spindle is not rotating, the chuck structure comprising at least one pair of diametrically opposed jaw members disposed about peripheral regions of the opening for contacting said shank, at least one pair of lever arm members corresponding to said respective jaw members, and a fulcrum region encircling said opening between and coupling said respective jaw members and said lever arm members such that as said respective lever arms are urged outwardly from said opening by centrifugal forces, reactive forces are transmitted through said fulcrum regions tending to urge said jaw members inwardly toward said axis to grip said shank;
and
(iii) a chuck alignment bushing mounted adjacent said tool end and having an opening formed therein for receiving the tool shank and an alignment surface for contacting said chuck and maintaining the chuck structure in concentricity with said shaft axis.

5 more elements

A tool changer for a machine tool system employing at least one tool head for mounting a tool along a predetermined axis and a work table which is selectively positionable with respect to the tool head for carrying a workpiece, comprising:

magazine means for accepting a removable tool clip carrying a plurality of tools inserted in aligned clip apertures, and for securing said inserted clip with said tools oriented along tool axes which are substantially parallel to said tool head axis;
means for locking or unlocking each tool in the inserted clip such that in the locked condition, the tools may not be removed from the tool changer, and in the unlocked condition, the tools may be removed from the tool changer;
means for translating the tool changer along an axis which is parallel to said tool head axis to transfer tools between said tool head and said tool changer;
and
means for mounting the tool changer to said work table.

2 more elements

A high speed precision drilling system adapted for drilling holes in workpieces such as printed circuit board, comprising:

a stationary base table;
a work table supported above said base table for translation along at least one axis and having a first surface for carrying a workpiece on a working area of said surface and a lower planar surface;
means for separating the work table and the base table on air bearings distributed over substantial areas of the second surface of the work table and providing distributed separating forces to separate the work table and the base table;
preloading means for applying distributed preload forces opposing the air bearing separating forces for damping oscillations of the table in directions normal to said table upper surface thereby minimizing table vibration;
at least one drilling spindle supported on a support structure separated from said work table, said spindle comprising a spindle body, a shaft supported within said body on rotary and linear air bearings to allow rotation of the shaft and axial translation of the shaft along a predetermined range of movement in relation to the spindle body, a chuck assembly mounted at a tool end of the shaft for securing a drilling tool therein in concentric alignment with the shaft axis, a rotary drive motor for imparting rotational drive forces on the shaft, and a linear drive means coupled to the shaft to impart axial drive forces to the shaft to feed the drilling tool into and out of a workpiece secured to the work table while the shaft is simultaneously rotated at high speed;
and
positioning means for translating said work table through a range of movement along at least one axis to position a workpiece carried thereon at a predetermined position relative to said spindle shaft;
whereby said spindle body remains stationary while the tool is fed into and out of the workpiece thereby further minimizing vibration of the system.

5 more elements

A high speed drilling spindle, comprising:

a spindle shaft having a shaft axis;
means for driving said shaft at high rotational speeds;
and
a centrifugal chuck assembly for securing a drilling tool to said shaft in alignment with the spindle axis during spindle rotation, comprising:
(i) a tool alignment bushing comprising a bore for receiving the inserted end of a drilling tool shank, the bushing mounted in said spindle such that said bore is aligned with said shaft axis;
(ii) a chuck structure mounted adjacent the tool end of the spindle shaft and having an interior opening formed therethrough to accept said shank, the chuck structure further comprising at least one pair of diametrically opposed jaw members disposed about peripheral regions of the opening for contacting said shank, at least one pair of lever arm members corresponding to said respective jaw members, and a fulcrum region encircling said opening between coupling said respective jaw members and said lever arm members such that as said respective lever arms are urged outwardly away from said opening, reactive forces are transmitted through said fulcrum region tending to urge said jaw members inwardly toward said axis to grip said shank;
(iii) a chuck alignment bushing mounted adjacent said tool end and having an opening formed therein for receiving the tool shank and an alignment surface for contacting said chuck and maintaining the chuck structure in concentricity with said shaft axis, and
(iv) means for applying a static gripping force on said tool shank when the spindle shaft is stationary, thereby retaining the tool in the inserted position within the chuck assembly, said means comprising a resilient O-ring member disposed between the outer periphery of said tools alignment bushing and the lever arm members of said chuck so as to urge the lever arms outwardly, causing the jaw members to grip the tool shank.

5 more elements

Dependencies are inferred from the claim text.

High speed precision drilling system

Life of this patent

High speed precision drilling system

Life of this patent

Abstract

Claims58