Metal working – Plural diverse manufacturing apparatus including means for... – With means to feed work intermittently from one tool station...
Patent
1991-05-22
1993-05-25
Briggs, William
Metal working
Plural diverse manufacturing apparatus including means for...
With means to feed work intermittently from one tool station...
409221, B23Q 702
Patent
active
052128571
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to fixturing systems for machine tools.
It is known in fully automated machine tools to have pallets which carry fixtures on which are mounted several workpieces at a time. The pallets are usually relatively large and flat and are mounted on a pallet changing device which can automatically replace a pallet on the machine after the machining operations are completed with a new pallet carrying more fixtures and another batch of workpieces.
The fixtures are mounted on the flat top surface of the pallet by means of a curvic coupling, or other arrangement, and rigidly clamped. The workpieces are mounted on the fixtures by further clamping devices.
An example of such a pallet system is used on machine tools manufactured and sold by Bridgeport Machines Limited in England.
Such systems are expensive both in terms of capital expenditure and in storage space. The fixtures are usually machined components which include means for holding the workpieces and are usually dedicated to one type of workpiece. Thus for machining different workpieces in batch production several costly fixtures are required.
Also for a 24 hour unmanned production operation, many pallets, each loaded with fixtures have to be stored in a large pallet handling system for automatic loading and unloading onto a machine.
The object of the present invention is to provide a fixturing system which avoids the need for expensive dedicated fixtures for holding workpieces, and which avoids the needs for storage and retrieval of the present large pallets.
In accordance with the present invention in its broadest aspect, there is provided a fixturing system for a machine tool which comprises an elongate core for attachment to a rotary axis of a machine tool with its longitudinal axis substantially parallel to said rotary axis, and at least one workpiece-providing cassette which is detachably secured to the core in such a manner that it projects from the periphery thereof.
By this means the core can remain permanently attached to the machine and only the cassettes need to be stored. Thus the invention avoids the use of conventional pallets and enables the traditional expensive fixture to be replaced by a relatively inexpensive cassette. Also, by having the cassettes mounted on the periphery of the core, and thus offset from the rotary axis, loading and unloading of the cassettes onto the core is facilitated.
The invention is capable of implementation in two alternative embodiments. In one embodiment the cassettes provide the workpieces by having one or more workpiece-locating recesses therein, which may be loaded with workpieces. The cassettes in this embodiment are mounted on the fixture core and removed after the machining operations have taken place to be re-loaded and re-used.
Alternatively the cassettes provide the workpieces by acting as blanks themselves on which one or more components are machined directly. In this embodiment therefore the cassettes are sacrificial or disposable.
Preferably the core has one or more highly accurate cassette-locating features on its periphery and each cassette has complementary locating features thereon whereby the cassettes may be accurately located on the core and may be removed from and replaced on the core by the same or another cassette in the same position. Where the cassettes act as workpiece holders each will further include workpiece-locating features thereon whereby one or more workpieces may be accurately located on each cassette.
However, the methods by which the cassettes are secured to the core, or by which the workpieces may be held on, or in the cassettes, may be many and varied. All kinds of clamping devices and bolting devices are traditionally used for holding fixtures on pallets or for holding workpieces on fixtures, and many would be capable of being used in the present system. The devices may be actuated by hydraulic, pneumatic, magneticm mechanical or other means generally known to those skilled in the art.
The preferred method chosen in the specific embodiments describ
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Briggs William
Renishaw plc
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