Turning – Miscellaneous
Patent
1990-07-31
1993-01-05
Schwartz, Larry I.
Turning
Miscellaneous
407120, 73104, 374141, 82900, B23B 2506
Patent
active
051760533
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a cutting tool equipped with a tool state indicator, and more specifically to a state indicator for measuring tool temperature and tool wear.
BACKGROUND OF THE INVENTION
The cost of a machining operation which requires the use of cutting tools is highly dependent on the wear rate of the tool. Consequently, attempts have been made in the past to measure tool wear directly, and to assess the useful length of life of a tool on the basis of tool wear, primarily on the basis of chamfer wear on the relief or clearance side of the tool. An experienced machine operator will be able to judge roughly with the naked eye whether or not the tool needs to be changed.
In present times automatization has progressed to such lengths that there is often no operator available, and consequently attempts have been made, for instance, to work with automated wear measuring methods with the use of image processing systems, which is an expensive and slow solution to the problem. It is necessary with such machines to halt machining work while the measurements are being taken. Attempts have also been made to measure tool wear indirectly, by measuring prevailing cutting forces, the changes in which forces are contingent on wear on the tool. The relationships, however, are not always specific and consequently the method is not reliable.
A third method involves measuring cutting temperatures, e.g. with the aid of a thermoelement inserted into a bore drilled in the tool. This results in mechanical weakening of the tool, however, and it is very difficult to drill holes in the extremely hard material from which such tools are made and to position the holes with precision. Tool temperatures are measured in on attempt to calculate the temperature of the cutting tool in the critical zone around the cutting edge--the contact surfaces between tool and chip or swarf and tools and workpiece respectively.
For mechanical strength reasons, it is necessary to place the thermoelement at a relatively long distance from the actual cutting edge and the temperatures measured will differ radically from the temperature which actually prevails at the contact surface and which determines the wear rate of the tool.
CROSS REFERENCE TO RELATED APPLICATION
It is disclosed in Swedish Patent Specification 8403609-4 dated Apr. 7, 1988 and from Swedish Patent Application 8403609-4 filed Jul. 6, 1984 and published on Jan. 7, 1986 under Publication No. 452,911, that a thermoelement and/or thermistor can be configured, for instance, with the aid of thin film techniques so as to measure the temperature of a spot or punctiform location on a tool or some other mechanical component.
Applicants' U.S. Pat. No. 4,945,770 dated Aug. 7, 1990 corresponds in its disclosure with Swedish Patent No. 8403609-4. The U.S. application Ser. No. 344,453 was filed 99,318, dated Aug. 11, 1987 (abandoned), and has a priority filing date of Jan. 2, 1986 based on PCT application PCT/SE86/00001 (Published as WO87/04236 on Jul. 16, 1987).
The aforesaid Swedish Patent Specification (U.S. Pat. No. 4,945,770) also discloses that tool wear can be measured successively with the aid of a plurality of conductors connected to the cutting edge, since the resistances in the conductors will change gradually and abruptly, depending on the extent to which the conductors are worn away.
SUMMARY OF THE INVENTION
It is highly desirable to be able to control a cutting process in a manner which will enable the process to be effected under optimum conditions with respect to cutting speed, feed and tool wear. However, the cutting properties of the machined material will vary from workpiece to workpiece, and even within one and the same workpiece. Consequently, when employing known techniques it is necessary to choose relevant cutting data conservatively, so that the tools are able to withstand the most difficult loading situations, which means that it is often necessary to work at excessively low cutting speeds or feeds.
It is also desired to avoid the occurrence of tool cata
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patent: 3079821 (1963-03-01), Von Zelewski et al.
patent: 4744241 (1988-05-01), Mayer
patent: 4885530 (1989-12-01), Mayer et al.
patent: 4927300 (1990-05-01), Ramalingam et al.
patent: 4945770 (1990-08-01), Alvelid et al.
patent: 5000036 (1991-03-01), Yellowley et al.
Alvelid Birger
Crafoord Ralph
Carroll Kevin J.
Schwartz Larry I.
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