Metal working – Plural diverse manufacturing apparatus including means for... – Binding or covering and cutting
Reexamination Certificate
2002-02-06
2004-09-07
Wellington, A. L. (Department: 3722)
Metal working
Plural diverse manufacturing apparatus including means for...
Binding or covering and cutting
C029S563000, C029S564000, C409S201000
Reexamination Certificate
active
06785942
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a machine tool system for machining a large-sized workpiece such as an aircraft part mounted on a workpiece mounting table, by moving a spindle having a tool mounted thereon in the directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece and, more specifically, to a novel machine tool system such as a machining center, which includes a spindle support structure having a spindle arranged to be movable in the directions along the X-axis, the Y-axis and the Z-axis, and a workpiece mounting table opposed to the spindle support structure, the workpiece mounting table having two pallet mounting surfaces and supporting the pallet mounting surfaces to allow them to be rotationally indexed in a desired position, and which can provide a highly efficient, high-speed and highly precise maching even for a large-sized workpiece and requires only a compact area for installation. The present invention also relates to a method for exchanging pallets in the machine tool system.
BACKGROUND ART
In the prior art, a method has been employed in which an airframe of an aircraft is constructed by dividing it into small components to be machined and by joining the components with bolts or rivets. In recent years, however, the trend is toward integrating those parts as far as possible and thereby reducing the number of joins. As a result, the parts to be machined have increased in size and have become complicated in shape, thereby giving rise to the demand for a novel machine tool for machining such parts.
The unique performance requirements for such a machine tool include the provision of a table on which a large-sized workpiece to be machined can be mounted, the provision of a sufficient stroke in feed axes to machine the large workpiece and the possibility of machining a large-sized part having a complicated shape at any portion, and in any kind of shape, by a single setup. Further, such a part must be machined efficiently, at a high speed and with high precision. Also, in view of fact that a desired size of a workpiece to be machined will vary from one machine tool user to another, the machine tool having a size required by each user can be manufactured timely and promptly and installed in the factory.
For purpose of fixedly mounting a large workpiece, the table of the machine tool has to be large, and it is necessary to take into consideration that the movability of the large table in the directions along three orthogonal feed axes, i.e., the X- Y- and Z-axes or in the directions along three rotational feed axes, i.e., the A- B- and C-axes is disadvantageous from the viewpoint of high-speed and highly precise machining. More specifically, unlike normal machine tools, a machine tool for machining a large workpiece requires that the spindle rotating with the tool held thereon is provided with orthogonal feed means and rotational feed means and is thereby movable in the directions along orthogonal feed axes and in the directions along rotational feed axes, in order to allow the workpiece to be machined with the table being fixed (in a stationary state) during the machining.
It is noted that the X-axis and the Y-axis are orthogonal to each other in a vertical plane, and extend horizontally and vertically, respectively, while the Z-axis extends in a horizontal direction perpendicular to the X-axis and the Y-axis. It is also noted that the directions along the A- B- and C-axis are defined as the directions of rotation about the X- Y- and Z-axes, respectively.
In addition, as a large workpiece is liable to deteriorate the efficiency of a workpiece setup process, it is required to provide means for automatically changing the workpiece thereby to improve the efficiency of the setup process and an operating rate of the machine tool.
Generally, in case that the workpiece is machined to a desired shape by a machine tool such as a machining center, the desired machining of the workpiece is efficiently performed by mounting the workpiece on a pallet and by exchanging the pallets between the pallet stocker and the workpiece mounting table of the machine tool including the table.
For such an efficient pallet exchange, components such as a pallet stocker acting as a setup station for performing the setup process therein, pallet changing means for replacing one pallet having a workpiece mounted thereon with another by transferring and carrying them, a pallet magazine for storing a plurality of pallets having a workpiece mounted thereon and pallet transferring means for transferring the pallets between the pallet magazine and the pallet stocker are required. Therefore, the large-sized machine tool for handling the pallets having relatively large workpiece mounted thereon is uselessly enlarged in its entire installation area unless these components are provided.
Further, such large workpieces are often mounted on the pallets by a vacuum method and may fall off the pallets, if the pallets are transported in a vertical state, to harm the workers in the worst case. In addition, the pallets in the vertical state are poorly balanced during the transportation, and some the workpieces mounted on the pallets may decline the pallets thereby to make it seriously difficult to mount the pallets on the workpiece mounting table of the machine tool. It is, therefore, desirable that the pallets having the large workpiece mounted thereon are handled in the horizontal state.
Further, in case that the large workpiece is machined, the time required for a setup process of mounting a workpiece on a pallet and for an exchange process of pallets is often substantially equal to that required for activating the machine tool to actually machine the workpiece. Therefore, since the setup time and the pallet exchanging time occupy a considerable ratio to that required for machining one workpiece, the shortening of the setup time and the pallet changing time may directly achieve high-speed machining and an improved machine operating rate.
A first prior art available for realizing the aforementioned requirements is a symmetric multiaxial linear motor machine tool, as disclosed in Unexamined Japanese Patent Publication (Kokai) No. 8-318445. The machine tool includes a vertical gantry movable in a direction along the X-axis on vertically opposed frames, a saddle movable in a direction along the Y-axis on the vertical gantry, a ram adapted to be movable in a direction along the Z-axis on the saddle, a spindle head disposed at the front end portion of the ram for rotatably supporting a spindle having a tool mounted thereon, and a table fixed on the front portion of the frame for mounting a workpiece thereon. The machine tool is driven to move in the individual feed directions along the X- Y- and Z-axes by linear motors. Moreover, the vertical gantry is guided on two sides, upper and lower sides, with respect to the frame and is driven by the linear motors. A stator (static element) and a mover (moving element) of the linear motor are arranged on the frame in vertically symmetric manner so that the attraction force of the stator acting on the mover both in the upper and lower linear motors may be vertically offset from each other.
A second prior art available for realizing the aforementioned requirements is a machine tool as disclosed in Unexamined Japanese Patent Publication (Kokai) No. 9-262727. The machine tool includes a vertical bed in the shape of a rectangular frame having a through opening at its center, as viewed in front view, an X-slide in the shape of a rectangular frame shape made movable on the front side of the vertical bed in a direction along the X-axis and having a through opening at its center, as viewed in front view, a Y-slide adapted to be movable in a direction along the Y-axis while being supported and guided in the through opening of the X-axis slide, a Z-axis slide adapted to be movable in a direction along the Z-axis while being supported and guided by the Y-axis slide, a spindle head disposed at the front end portion of the Z-axis slide for rotatably
Makino Milling Machine Co., Ltd.
Paul & Paul
Ross Dana
Wellington A. L.
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