Machining center

Details Machining center Machining center

2002-11-04

2004-03-30

Cadugan, Erica (Department: 3722)

Metal working

Plural diverse manufacturing apparatus including means for...

With means to feed work intermittently from one tool station...

C029S02700R, C029S564000, C029S03800E, C082S129000, C082S122000, C082S138000, C408S037000, C408S043000, C409S192000, C409S203000, C409S158000, C409S159000, C409S161000, C409S165000

Reexamination Certificate

active

06711804

ABSTRACT:

FIELD OF THE INVENTION
My present invention relates to a machine tool and, more particularly, to a machining center having a multiplicity of stations at which machining operations can be carried out. Also the invention relates to a machining center of the type in which the multiplicity of machining stations are arrayed about a central axis.
BACKGROUND OF THE INVENTION
A machining center having a central axis and a multiplicity of positions or stations at which machining can occur arrayed around the axis is known. The machining center can be used primarily for the machining of metal workpieces by turning, milling, drilling or the like machining operations. They enable, for example, one workpiece to be machined at a first station while other workpieces are machined at other stations and each workpiece to be transferred from a first to a second station and so on until the machining operations are completed. The machining center permits not only a succession of different machining operations to be carried out upon a given workpiece but also a number of workpieces to be operated upon simultaneously to thereby increase productivity, reduce machining time and minimize the machining cost. When, in addition, the workpiece transfer between stations or positioning of the workpiece at the respective station is effected automatically, manual intervention is reduced to a minimum, and cost is similarly reduced.
In German patent document DE 195 04 369 Al, a multispindle machine tool is described which has a multiplicity of spindles in a frame rotatable about an axis, the spindle each engaging a workpiece and being rotatable. The arrangement of the spindles in this system is, however, fixed relative to the frame and the entire frame can be set into rotation in increments of, for example 45° about the central axis so that the workpiece on each spindle is presented to a new working station or sector at which it can be engaged by a tool.
The tools in each sector can then be moved towards the workpiece to allow machining of the latter when it is set into rotation through the respective spindle or even while it is at standstill.
The fixed arrangement of the individual spindle with respect to the axis, even with the freedom of rotation of the spindles between stations, has the disadvantage that the tool in each working sector or machining station must be movable toward and away from or relative to the workpiece. In point of fact the tools are mounted to enable radial movement of the tools relative to the spindles. The positioning of the workpieces on the spindles at the work stations is then exclusively by the rotation of the entire spindle assembly and each spindle may be vertically displaceable to vary the vertical position of the workpiece holder at each station.
The horizontal position of each workpiece in the particular machining sector or station is fixed and usually located along a center line through the particular sector or station. In German patent document DE 199 16 212 Al, the spindles within a sector or station can be movable along a predominantly circular path. This allows a spindle unit to cooperate within each machining sector or station with, for example, two different tools while in at least one other station the spindle is not moved. This permits various machining processes, some of which can be more time extensive than others, to be optimally combined with each other. It also enables a more flexible arrangement or use of the tools in the individual machining stations or sectors.
Nevertheless this machine has the disadvantage that within each sector only a limited number of tools can be arranged. Additionally for the system of DE 199 16 212 as well as that of DE 195 04 369, after a complete machining cycle, the array of spindles is periodically rotated back through about 360
to return the individual spindles to their starting positions when extensive slide contacts and distributors are to be avoided for the electrical and fluid lines. A further drawback is that in each machining sector the tool must be mounted for radial shiftability when a relative radial movement of the workpiece and tools is required for the machining purpose. For each tool, therefore, there must be a corresponding feed and guide arrangement which has its own drive and that can be costly, especially when a large number of tools is provided.
OBJECTS OF THE INVENTION
It is, therefore, the principal object of the present invention to provide a machine tool and especially a machining center whereby the aforementioned drawbacks are avoided.
Another object of the invention is to provide, in a machine tool of the aforedescribed type, an arrangement which reduces the cost for multi-axis machines, limits the size of the machining stations which are required for that purpose and ensures reduction in time for multi-step machining operations.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter are attained, in accordance with the invention in a machine tool and especially a machining center having a spindle unit, also referred to as a work spindle unit which is mounted to orbit a central axis and, of course, can be rotatable about its own axis. At least one such spindle unit is provided so that it can be positioned in at least one but preferably a plurality of positions spaced around the central axis and so that at least some of the stations can be provided with tool units. The at least one work spindle unit, in addition, is movable in the radial direction relative to the central axis and, in an embodiment of the invention, across or through this axis to a position or station at the opposite sides of the orbit.
The movement of the at least one work spindle unit in the radial direction may be independent of any positioning movement thereof of the workpiece relative to the work spindle unit and independent of any positioning movement of the tool or tools at the particular station.
The system of the invention, therefore, provides that the workpiece, which can be mounted on the work spindle unit, can be shiftable in the radial direction within a machining sector or station independently of any positioning movement required for the machining practice at that station itself. The work spindle unit, by being orbital about the central axis can position the workpiece at any of the machining sectors or stations thereby contributing additional degrees of freedom of movement and especially the freedom of movement of the radial direction, or movement of the workpiece so as to place the workpiece in a position where it can be attacked by a tool at that station, i.e. for positioning the workpiece and/or for the machining itself or to allow selection of the tool which is to engage the workpiece.
Through this additional radial mobility of the work spindle unit it is possible to dispose tools along various partial circular paths or circular path segments in any of the machining sectors or stations for contact with the workpiece so that a feed device can be eliminated for all or for some of the tools at the particular sector or station or such that none of the tools or not all of the tools need be provided with respective feed units.
In combination with the vertical mobility of the workpiece, each can be provided by the working spindle unit, each machining sector or station can have a multiplicity of tools at different spacings from the central axis and at different vertical positions or heights for respective contact with the workpiece.
The radial movement of the work spindle unit can be decoupled advantageously from the positioning movement of the spindle unit. The term “positioning movement” when referring to the spindle movement will be understood to be that movement of the workpiece which causes machining when the workpiece engages a tool. That will be understood to be distinct from the radial movement of the workpiece holder, namely, the work spindle unit which has been referred to before and may be provided in addition to the positioning movement and may, for example, enable the workpiece to be dis

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