Turning – Radially moving rotating tool inside bore – Tool simultaneously moving axially
Reexamination Certificate
1999-11-18
2002-04-09
Tsai, Henry (Department: 3722)
Turning
Radially moving rotating tool inside bore
Tool simultaneously moving axially
C082S118000, C082S133000, C082S147000
Reexamination Certificate
active
06367359
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the provision and use of a programmable boring and contouring apparatus or “head assembly” for performing three-dimensional machining operations such as boring, contouring, threading, turning, facing and the like, using a head assembly that is rotated about a primary rotation axis (PRA) of a machining center, wherein the head assembly has a radially movable tool holder for supporting a cutting tool at a radial offset distance (ROD) from the PRA which is controlled, at least in part, through the use of a micro-controller and a servo motor that are components of the head assembly itself. More particularly, the present invention relates to a boring and contouring apparatus or “head assembly” having on-board logic 1) for being mounted on the rotatable spindle of a machining center such as a boring machine, 2) for being rotated about a primary axis of rotation (PRA) of the spindle, and 3) for supporting a cutting tool such as a boring bar at a controllable radial offset distance (ROD) from the PRA, wherein the ROD is adjusted by the head assembly as the head assembly is advanced along the PRA by the machining center, so that a bore or other desired type of workpiece formation is formed having one or more turned surfaces that differ in diameter as a function of their location along the PRA or vice versa. Features of the invention reside not only in the apparatus and but also in methods by which turned surfaces of varying diameter are formed, and in safety features that obtain through providing the apparatus with an electronically readable identification code that can be checked by control logic external to the head assembly to ensure that a correctly programmed head assembly carrying a correct cutting tool is being installed on a machining center to perform desired functions.
2. Prior Art
So-called “standard machining centers” are known that each utilize a spindle which is rotatable (relative to a workpiece on which cutting operations are to be performed) about a spindle rotation axis (referred to herein by the term “primary rotation axis” or by the abbreviation “PRA”), wherein the spindle is used to support a tool head or “head assembly” that rotates (together with the spindle on which it is mounted) about the PRA to bring a cutting tool that is carried by the head assembly into engagement with the workpiece to perform boring or other turning type cutting operations that center about the PRA.
Head assemblies utilized for such purposes typically are provided with tool holders that are manually adjusted to radially position (at a selected radial offset distance from the PRA, referred to herein by the abbreviation “ROD”) such cutting tools as are mounted on their tool holders. Head assemblies having manually adjustable tool holders (i.e., the ROD of the tool holder is manually adjustable) often are used to bore holes of selected diameters in workpieces or to form turned surfaces with features having diameters that vary as functions of the position of these features along the associated PRA, or vice versa. Usually these manually adjustable head assemblies require that relative rotation of the head assembly and the workpiece be stopped when adjustments (i.e., ROD adjustments) are to be made as by manually repositioning the tool holders on the head assemblies.
Head assemblies also are known that incorporate an ability to effect ROD adjustments of their tool holders without stopping relative rotation of the tool holders and the workpieces. However, many of these so-called “easier to adjust” head assemblies have one or more associated drawbacks that have left a long-standing need for an improved boring and contouring apparatus that offers a radially adjustable tool holder that has the ability to coordinate the radial and axial positioning of cutting tools in a simple and effective manner to provide smoothly contoured workpiece surfaces of desired configuration.
One common drawback of present-day head assemblies that have tool holders with ROD adjustments that can be made during tool rotation is that they are not well suited for use with standard machining centers unless modifications are made to provide some means for transmitting control signals to the rotating head assembly to cause the cutting tool it carries to be properly ROD positioned. One approach that has been taken is to replace the normally solid spindles of standard machining centers with hollow spindles, through which mechanical movements (i.e., “mechanical control signals”) can be provided to rotating head assemblies to cause their tool holders to effect proper ROD adjustments of cutting tools as cutting operations proceed. Another approach that has been taken is to provide standard machining centers with mechanical apparatus located to one side of their rotating head assemblies for transmitting control motions (i.e., “mechanical control signals”) to the rotating head assemblies to carry out needed ROD adjustments mechanically. Still other approaches have called for the use of electrical contacts to transmit electrical control signals, or the use of transmitters and receivers of such non-mechanical, non-electrical control signals such as infrared light, to the rotating head assemblies so the head assemblies will coordinate the ROD positioning of cutting tools (that are being rotated by the head assemblies as the head assemblies are rotated by the machining centers) with the axial positions of these tools along the PRA—so that desired contours and profiles can be generated as cutting operations proceed.
If a standard machining center that has a capability to control the rotation and axial positioning along the PRA of a head assembly is to be provided with the added capability to control the ROD positioning of a cutting tool that is carried by the head assembly, this necessitates that some means be provided to coordinate ROD movements of a tool holder of the head assembly with the movements of other components of the machining center. Stated in another way, the addition of a radial tool positioning capacity to a machining center that does not have such a capacity has typically required that the machining center's numerical control system be modified or replaced, otherwise the required coordination of movements cannot be achieved. Making such modifications and replacements requires considerable technical skill and a good working knowledge of numerical controls, is expensive, and risks the introduction of inaccuracies and errors inasmuch as numeric control system components and their specifications must be matched to the particular servo motors and gear sizes and other features of the components that are used. In many instances, it may not be possible to retrofit a machining center with a new numerical control system that will provide radial cutting tool positioning control (i.e., that will control the ROD of a cutting tool which calls for the machining center to provide tool positioning control along what amounts to an “added axis”) that is properly coordinated with other cutting tool movements (such as rotation about and axial movement along the PRA of the spindle).
Many of these proposed modifications and/or additions result in the provision of non-standard apparatus that is not interchangeable from one work station to another, and that is not well suited for use with automatic tool changing equipment that may be required in order to enable a machining center to perform sequential operations with efficiency. Some of the proposed additions and/or modifications provide non-standard structure that is so bulky, heavy and/or dynamically out of balance as to be unusable with smaller machining centers. In many instances, the additions and modifications that are required are found to compromise machining accuracy.
A deficiency of most previously proposed head assemblies has been their inability to automatically advance the radial position (i.e., the ROD) of a cutting tool during tool rotation, or to take other needed steps to accommodate or re
Burge David A.
Tsai Henry
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