Symmetrical multi-axis linear motor machine tool

• US 6,217,496 B1
• Filed: 08/12/1999
• Issued: 04/17/2001
• Est. Priority Date: 05/12/1995
• Status: Expired due to Term

• Current Assignee: Camozzi Pneumatics, Inc. (Camozzi Industries SpA), Ingersoll Machine Tools Incorporated (Camozzi Industries SpA), Fitch Even Tabin & Flannery LLP
• Original Assignee: Ingersoll Milling Machine Company
• Inventors: Lindem, Thomas Jules
• Primary Examiner(s): BRIGGS, WILLIAM R
• Application Number:
  US09/372,926
• Time in Patent Office: 614 Days
• Field of Search: 483/14, 483/15, 483/30, 483/36, 408/234, 409/202, 409/212, 409/191, 409/235, 451/11, 451/67, 451/162, 451/164, 451/340, 310/12, 310/13, 318/575, 318/687, 700/249
• US Class Current: 483/30
• CPC Class Codes: B23Q 1/017 Arrangements of ways
• CPC Class Codes: B23Q 1/626 followed perpendicularly by a single sliding pair
• CPC Class Codes: B23Q 11/005 by blowing
• CPC Class Codes: B23Q 11/0875 Wipers for clearing foreign matter from slideways or slidable coverings
• CPC Class Codes: B23Q 37/00 Metal-working machines, or constructional combinations thereof, built-up from units designed so that at least some of the units can form parts of different machines or combinations; Units therefor in so far as the feature of interchangeability is important features relating to particular metal-working operations, see the relevant subclass, e.g. B23P23/00
• CPC Class Codes: B23Q 5/28 Electric drives
• CPC Class Codes: B23Q 5/34 Feeding other members supporting tools or work, e.g. saddles, tool-slides, through mechanical transmission
• CPC Class Codes: Y10T 408/91 Machine frame
• CPC Class Codes: Y10T 409/307728 including gantry-type cutter-carrier
• CPC Class Codes: Y10T 409/308288 including gantry-type cutter-carrier
• CPC Class Codes: Y10T 409/309576 Machine frame
• CPC Class Codes: Y10T 483/1733 Rotary spindle machine tool [e.g., milling machine, boring, machine, grinding machine, etc.]

Abstract

A machine tool has a frame supporting a vertical gantry which is driven at the top and bottom sides of the gantry such that the opposed, normal magnetic forces between stator coils and magnets are substantially equal and are self-cancelling. This reduces normal magnetic forces that increase friction, and this prodes symmetry along an X-axis. A spindle-carrying saddle travels in a vertical slot in the center of the gantry with left and right linear motors mounted on opposite sides of the gantry. The linear motors are identical so that opposed right and left-hand, normal magnetic forces are self-cancelling. This provides symmetry along the vertical Y-axis. A spindle and ram are mounted on the saddle and are driven by at least one linear motor to travel along the Z-axis. The symmetry and cancelling of normal, magnetic attractive forces reduces the weight and the amount of forces needed to accelerate the gantry in the X-direction and the saddle in the Y-direction. The preferred frame is a stationary, box-type stue which encompasses the gantry and spindle, and the frame provides an enclosed space protecting the linear motors.

Claims

1. A machine tool for advancing a tool, such as a rotary cutting tool, along at least three mutually transverse axes for cutting of a workpiece, the machine tool comprising:

a spindle having a tool mounted thereon;

a frame to support the spindle and cutting tool while cutting and being advanced along the transverse axes;

a gantry mounted to the frame for slidable movement in a first axis relative to the frame;

a saddle mounted within the gantry and carried therewith and mounted for slidable movement along a second axis perpendicular to the first axis and along and within the vertical gantry;

a ram carried by the saddle for movement along a third axis perpendicular to the second axis and carrying the spindle and rotary cutting tool for movement along the third axis;

a first linear gantry drive having at least one linear motor having portions mounted on the gantry and mounted on the frame and extending in the direction of the first axis for moving the gantry relative to the frame along the first axis;

a second linear saddle drive having at least one linear motor for moving the saddle along and within the gantry and along the second axis;

a third linear ram drive having at least one linear motor mounted between the saddle portion and the ram and extending in the direction of the third axis for moving the ram and spindle along the third axis to move the tool toward the workpiece and away therefrom; and

the second linear drive includes a first linear motor within the gantry having portions mounted on a first side of the gantry and on a first side of the saddle and each extending in the direction of the second axis and a second linear motor within the gantry having portions mounted on a second side of the saddle and a second side of the gantry and each extending in the direction of the second axis so that the ram and the lower portion of the saddle carrying the ram are disposed between the first and second linear motors of the linear saddle drive.

2. A box assembly for driving a tool along a plurality of mutually transverse axes for cutting a workpiece, the box assembly comprising:

a spindle capable of receiving a tool;

a box frame having a first set of top and bottom frame members and having a second set of side members connected to the top and bottom frame members and defining an internal space and having a forwardly facing opening;

a vertical gantry extending between the top and the bottom frame members in the frame internal space mounted for slidable movement relative to the frame along a horizontal X-axis extending relative to the side frame members adjacent to the opening, the gantry having a top member adjacent to and below the frame top member and a bottom member adjacent to and above the frame bottom member and two spaced side members with a front face therebetween forming an elongate central vertical slot adjacent the frame opening;

carriage means for mounting the spindle for sliding movement in two directions perpendicular to the X-axis, one direction being along a vertical Y-axis coincident with the vertical slot with the carriage means further defining the other direction along a horizontal direction of movement extending through the slot, a saddle portion of the carriage means for sliding along the vertical Y-axis and disposed between the gantry side frame members and behind the front face of the gantry, both the gantry and the saddle portion being within the box frame which surrounds and supports the moving gantry and saddle portion without a cantilever supporting thereof on the box frame; and

linear motor drive means associated with the vertical gantry and carriage means capable of causing a tool to be advanced at a speed of at least 1,500 inches/minute and at an acceleration or deceleration of at least 1 G along the X, Y and Z-axes with the frame, gantry and saddle portion being formed from a material having a high level of material stiffness.

3. The box assembly of claim 2 wherein the frame, vertical gantry and carriage means are formed from steel and have a predetermined natural structural frequency and the linear drive means includes a motor drive circuit having a preselected operating frequency range with the operating frequency range being preselected such that the predetermined natural structural frequency is greater than the preselected operating frequency range of the motor drive circuit.

4. The box assembly of claim 2 wherein a plurality of resilient vibration absorbing pads are attached to the box frame to mount the frame to a support surface and isolate the box assembly and support surface from each other.

5. The box assembly of claim 4 wherein three vibration pads are attached to the frame bottom member for three-point mounting of the box frame to a support surface.

6. A machine tool for advancing a tool, such as a rotary cutting tool, along at least three mutually transverse axes for cutting of a workpiece, the machine tool comprising:

a spindle having a tool mounted thereon;

a frame to support the spindle and cutting tool while cutting and being advanced along the transverse axes;

a gantry mounted to the frame for slidable movement in a first axis relative to the frame, the gantry defining an opening;

a saddle mounted within the gantry and carried therewith and mounted for slidable movement along a second axis perpendicular to the first axis and along and within the vertical gantry;

a ram carried by the saddle for movement along a third axis perpendicular to the second axis extending through the gantry opening and carrying the spindle and rotary cutting tool for movement along the third axis;

a first linear gantry drive having at least one linear motor having portions mounted on the gantry and mounted on the frame and extending in the direction of the first axis for moving the gantry relative to the frame along the first axis;

a second linear saddle drive having at least one linear motor for moving the saddle along and within the gantry and along the second axis; and

a third linear ram drive having at least one linear motor mounted between the saddle portion and the ram and extending in the direction of the third axis for moving the ram along the third axis and through the gantry opening which faces forwardly toward the workpiece to move the spindle and tool toward the workpiece and away therefrom.

7. The machine tool of claim 6 wherein the saddle includes a lower portion to provide the ram with support from underneath thereof, and the second linear drive includes a first linear motor within the gantry having portions mounted on a first side of the gantry and on a first side of the saddle and each extending in the direction of the second axis and a second linear motor within the gantry having portions mounted on a second side of the saddle and a second side of the gantry and each extending in the direction of the second axis so that the ram and the lower portion of the saddle carrying the ram are disposed between the first and second linear motors of the linear saddle driver.

8. The machine tool of claim 6 including a table for supporting the workpiece thereon with the table being fixed against movement along the first, second and third axes so that as different workpieces having different sizes and weights are mounted on the fixed table for machining, speeds and accelerations that can be achieved by the respective linear motors for the gantry, saddle and ram remain the same regardless of the workpiece size and weight.

9. The machine tool of claim 6 wherein the frame includes an internal space with the gantry and saddle mounted in the internal space, and

means for substantially sealing the internal space to allow the ram and spindle to extend beyond the internal space while limiting workpiece chips generated and coolant used at the tool and workpiece interface from entering the internal space during a machining operation.

10. The machine tool of claim 9 including means for pressurizing the internal space to provide a positive pressure therein for keeping the space free of chips and coolant.

11. The machine tool of claim 6 wherein the linear motors each have a row of permanent magnets cooperating with a coil section and the first linear drive comprises a first pair of symmetric linear motors having magnetic force attractions in opposite directions to offset their respective forces.

12. The machine tool of claim 6 wherein the gantry and saddle each include respective pairs of side walls, and the saddle portion includes a bottom wall extending between the saddle side walls to form a cradle for supporting the ram from underneath thereof as it is driven for movement along the third axis by the third linear drive, and

the linear saddle drive has first and second linear motors each being positioned between the gantry side walls and corresponding saddle side walls, respectively, and having magnetic force attractions in opposing directions to offset one against the other.

13. The machine tool of claim 12 wherein the ram includes a bottom support plate with the third linear drive comprising a linear motor positioned between the ram bottom plate and saddle bottom wall for sliding movement of the ram in the third axis.

14. The machine tool of claim 6 wherein the ram includes a box-shaped body defining a spindle receiving bore and having slide rails mounted thereon, and means to limit the travel of workpiece chips generated and coolant used at the tool and workpiece interface during a machining operation from entering into the machine tool.

15. The machine tool of claim 6 wherein the gantry has a depth extending along the third axis several times shorter than the ram.

16. The machine tool of claim 6 wherein the gantry opening is a through opening so that the ram extends forwardly and rearwardly beyond the gantry.

17. A machine tool for advancing a tool along a plurality of mutually transverse axes for cutting a workpiece disposed in a work zone, the machine tool comprising:

a rotary spindle having a cutting tool mounted thereon;

a frame to support the spindle and cutting tool while cutting and being advanced along the transverse axes;

a vertical gantry mounted for slidable movement in a first axis relative to the frame;

a saddle mounted within the gantry and carried therewith and mounted for slidable movement along a second axis perpendicular to the first axis and along and within the gantry;

a ram carried by the saddle and mounted for slidable movement along a third axis perpendicular to the second axis and carrying the spindle and rotary cutting tool for movement along the third axis toward and away from the work zone;

a first linear drive having first and second linear motors mounted proximate opposite ends of the gantry and extending in the direction of the first axis for moving the gantry relative to the frame along the first axis;

a second linear drive having first and second linear motors mounted on opposite sides within the gantry each extending in the direction of the second axis for moving the saddle along and within the gantry and along the second axis with magnetic force attractions being in opposite directions to provide symmetry;

each of the first and second motors of the respective first and second linear drives generally lying in a single plane defined by the first and second axes; and

a third linear drive having one or more linear motors mounted between the saddle and ram and extending in the direction of the third axis for moving the ram and spindle along the third axis.

18. The machine tool of claim 17 wherein bearings are provided for gantry travel along the first axis and saddle travel along the second axis with the gantry and saddle bearings being aligned and generally lying in a plane forwardly of the plane in which the motors of the first and second linear drives lie to minimize the distance along the third axis between the co-planar bearings and the work zone and the overhang of the spindle from the bearings.

19. The machine tool of claim 17 wherein the gantry has side walls with an internal space therebetween and the saddle has side walls in the gantry internal space, and the first and second linear motors are disposed between the corresponding gantry side walls and saddle side walls for driving the saddle along the second axis entirely within the gantry internal space with there being no cantilevered portions of the saddle relative to the gantry.

20. The machine tool of claim 19 wherein the frame has a box-shape defining an internal space and including top and bottom frame members and side frame members connected to the top and bottom frame members, and the gantry has a top frame member adjacent to and below the frame top member and a bottom member adjacent to and above the frame bottom member so that both the gantry and saddle are entirely within the box frame to minimize cantilevers therefrom.

21. The machine tool of claim 17 wherein the linear motors are capable of moving the gantry, saddle and ram to cause a tool to be advanced at a speed of at least 1,500 inches/minute and at an acceleration or deceleration of up to at least 1 G with the frame, gantry and saddle being formed from steel to provide them with a high level of material stiffness.

22. The machine tool of claim 17 wherein the third linear drive comprises a pair of linear motors mounted on opposite sides of the ram for moving the ram and spindle with, magnetic force attractions being in opposite directions to provide symmetry.