Abrasive tool making process – material – or composition – With carbohydrate or reaction product thereof
Patent
1982-05-10
1985-05-07
Whitehead, Harold D.
Abrasive tool making process, material, or composition
With carbohydrate or reaction product thereof
5116573, 51267, 51322, 51289R, 324238, B24B 4914
Patent
active
045149348
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates generally to a method and apparatus for abrasively machining a workpiece and more particularly to a method and apparatus for controllably grinding ferrous metal workpieces.
2. Background Art
A number of attempts have been made to control abrasive machining operations to prevent overheating the workpiece. In particular, several attempts have been made to control the amount of heat input to a metal workpiece during grinding operations, by limiting contact pressure between the grinding tool and the workpiece, or by controlling feed rate, wheel speed, coolant flow, or dressing speed and feed. In general, grinding processes are controlled by establishing a predetermined value for one or more of the above operating parameters and then limiting the grinding machine operation to less than the predetermined values. An example of such a control method is disclosed in U.S. Pat. No. 4,118,900, issued Oct. 10, 1978 to Sodao Moritomo et al.
However, it has been found that even by limiting grinding machine operation to predetermined --and presumably safe--values, it is not always possible to produce defect-free articles. For example, it has been found that different grinding wheels manufactured by the same manufacturer vary in quality and have different grinding characteristics. It has also been found that in a single grinding wheel, grinding characteristics may vary as the wheel wears. Often the change in grinding characteristics, during operation, are such that the predetermined operating parameters are not adequate to safeguard the workpiece from damage and as a result of production of excess heat, the workpieces are damaged.
The present invention is directed to overcoming one or more of the problems as set forth above by sensing changes in the workpiece resulting from the abrasive machining operation as the changes occur during the operation.
DISCLOSURE OF THE INVENTION
In accordance with one aspect of the present invention, a method for abrasively machining a workpiece by contacting the workpiece with an abrasive tool includes establishing an eddy-current in the workpiece at an area where the tool contacts the workpiece, sensing any change in the eddy-current in response to change in the microstructure of the workpiece, and controlling the abrasive machining operation in response to the sensed change in microstructure.
In another aspect of the present invention, an apparatus for abrasively machining a workpiece by contacting the workpiece with an abrasive tool and moving the workpiece or the tool relative to one another includes a means for establishing an eddy-current in the workpiece and sensing any change in the eddy-current in response to change in the microstructure of the workpiece resulting from the abrasive machining operation and generating an output signal responsive to the sensed change in microstructure.
Heretofore, it has not been possible to detect small changes in the microstructure of a workpiece during a grinding operation. Detection of grinder burn on the surface of a workpiece has been a particularly vexatious problem. Grinding burn is generally characterized as small undesirable changes in the surface morphology or microstructure of metallic workpieces resulting from the grinding operation. Each grinding parameter such as dressing, feed rate, coolant, or wheel composition and quality, can cause grinder burn. The detection of grinder burn has previously been possible only by destructive test techniques such as etching, polishing, or indentation hardness measurements.
The present invention not only provides a method of non-destructively detecting grinder burn, but also permits the detection of grinder burn at its very incipiency and provides a method of controlling the abrasive machining process to prevent the burn from progressing beyond predetermined allowable limits. Further, the present invention provides a method and apparatus that is particularly useful in controllably grinding hardened ferrous metal workpieces and consistently produci
REFERENCES:
patent: 2427064 (1947-09-01), Moul
patent: 3341983 (1967-09-01), Baldenhofer
patent: 3646839 (1972-03-01), Shillam
patent: 3653855 (1972-04-01), Smith
patent: 3810002 (1974-05-01), Sata
patent: 3939404 (1976-02-01), Tait
patent: 3992826 (1976-11-01), Nakaoka
patent: 4095469 (1978-06-01), Yamada
patent: 4118900 (1978-10-01), Moritomo et al.
patent: 4258319 (1981-03-01), Shimada
"Eddy-Current Testing", Tool and Manufacturing Engineers Handbook, 3rd Edition, pp. 33-21 thru 33-23, 1976, McGraw-Hill, New York.
Pierce Rex G.
Ray Robert W.
Caterpillar Tractor Co.
McFall Robert A.
Whitehead Harold D.
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