Optics: measuring and testing – Dimension – Width or diameter
Reexamination Certificate
2002-04-17
2003-07-22
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Dimension
Width or diameter
C356S613000
Reexamination Certificate
active
06597464
ABSTRACT:
The invention relates to a method for testing a cutting-edge geometry of a rotatably drivable tool and a device for performing the method according to the invention. In particular, the invention relates to the testing of a cutting-edge geometry of a tool for the purpose of breakage and wear monitoring by means of a measuring beam.
The use of measuring systems to test rotatably drivable tools using a measuring beam, in particular an optical measuring beam is known. Thus, DE 42 38 504 describes a method that measures the length and the diameter of a tool and also concentricity errors using a thin laser beam. In this way, not only can the setting of the tool be checked, but also wear or a break in the tool can be detected. In this procedure, the tool is presented to an optical measuring plane perpendicular to the measuring plane. The measuring system outputs a signal that indicates whether the tool has entered the measuring plane. When the tool enters, its relative position is determined with respect to the measuring plane in order to calculate the dimensions of the tool using reference points. In order, in addition, to determine the concentricity and the diameter of the tool, the rotating tool is also fed parallel to the measuring plane.
In order to avoid impairments of the measuring operation as a result of contaminants in the air in a measuring region of an optical measuring system, in accordance with DE 42 44 869, a signal that indicates the entry of a tool into the measuring plane is generated only if a drastic signal decrease is detected in a laser beam used as measuring beam. In addition, comparison values are recorded by the measuring system that serve as reference values for individual measuring operations and are intended to reduce interference effects that impair the measuring operation.
Furthermore, DE 32 18 754 discloses a method for measuring the length of a rotatably drivable tool. In this method, the tool passes an optical measuring device, the position of the tool being determined when the tool tip passes through a measuring plane of the optical measuring device. The length of the tool can be calculated by comparing the measured position with a standard position of the tool. In this way, it is also possible to determine whether the tool is broken.
During the industrial application of these described methods, it has emerged that faulty or unsatisfactory measurements occur as a result of contaminants, e.g. due to coolants or metal chips, in the measuring regions of the optical measuring systems used. Furthermore, the optical measuring systems used have to be re-adjusted as a function of the tools used and also their rotational speed has to be re-adjusted for the particular application case. In addition, none of these known methods makes possible a check of the individual cutting edges of a tool or also a complete check of the geometry of a tool.
DE 39 05 949 A1 discloses a measuring system for testing a cutting-edge geometry in which occlusions of a measuring beam due to obstacles in its propagation path are detected and evaluated. No provision is made therein to take account of standard time instants and detection time instants.
In accordance with DE 692 23 544 T2, interferences in the optical measurement of the profile of an object are eliminated in that the optical scanning of the object by means of a laser beam is restricted to predetermined time intervals. For this purpose, the laser beam is allowed to emit light in an illumination time interval, whereas the laser beam is switched off in a switched-off time interval. For this purpose, a read-out device for receiving the laser beam is operated synchronously in order to repeat alternately a synchronous read-out scanning operation of light-receiving elements.
DD 245 481 A1 discloses a method and an arrangement for determining photoelectrically the position of edges on rotating specimens with respect to their axis of rotation. In this method, during a first revolution, that rotation position of the specimen relative to the photoreceiver in which a specified edge of the specimen is detected by a photoreceiver is determined by means of an optical measuring method. During further revolutions of the specimen, only those photoreceiver signals that are detected in the previously determined rotation position of the specimen are evaluated by means of a high-resolution, slow method.
From U.S. Pat. No. 3,900,738, U.S. Pat. No. 3,817,647, JP(A) 0 221 20 45 and U.S. Pat. No. 4,667,113, it is known, for the purpose of testing a cutting-edge geometry of a rotatably drivable tool, to move a region to be tested of a tool that is being rotated at a specified rotational speed into a measuring range defined by a measuring beam and to detect signals that indicate when and if the measuring beam is instant on the region to be tested or is interrupted by it.
In accordance with DE 197 20 176 C1, to eliminate interfering signals in the case of a light barrier, light pulses incident on a receiver of the light barrier are evaluated only during specified time intervals whose time period is matched to the length of the time intervals within which light pulse sequences are emitted by a transmitter of the light barrier.
It is therefore the object of the invention to eliminate interference effects in a measuring plane of a measuring system during the testing of a rotatably drivable tool.
In order to make possible a desired machining quality with a rotatably drivable tool, it is necessary to ensure that the tools used have certain properties. Said properties include, inter alia, the positioning of a tool in a suitable holding device of the tool machine and also the geometry of the tool itself. With the aid of the method according to the invention, it becomes possible to check a rotatably drivable tool in regard to its actual shape. For this purpose, a region to be tested is defined on the tool, for example the region of the cutting edge of the tool. The tool is rotated at a desired rotational speed and is introduced into a measuring range that is defined by a measuring beam. As a result of the rotation of the tool, the measuring beam is able to strike that region of the tool to be tested, but it is also possible that the measuring beam does not strike the region to be tested. Beside this interaction with the region to be tested, interactions between the measuring beam and other media or substances situated in the measuring range may also occur, for example with drops of coolant or metal chips. In order to test the tool, the interactions of the measuring beam with the region to be tested are detected. In this connection, it is necessary to avoid interactions between the measuring beam and the other substances or media that result in spurious measurements.
According to the invention this is avoided in that the detection takes place only during time intervals that comprise time instants at which it is to be expected that the region to be tested enters the measuring beam during the rotation. Such time instants are determined using a specified pitch, denoted below as standard pitch, of a reference tool corresponding to the tool to be tested. These time instants determined are denoted below as standard time instants. The detection is then performed during chosen detection intervals that each contain a standard time instant in order to check, on the basis of optical interactions that occur or do not occur, whether the tool has the standard pitch or is damaged.
In this connection, provision is made that the detection time intervals are chosen in such a way that they do not overlap in time. Furthermore, the detection time intervals can be chosen in such a way that they comprise the corresponding standard time instant symmetrically.
Tools that are used as reference tools for the tools to be tested comprise real tools whose dimensions comply with the desired dimensions for the tool to be tested, for example undamaged or new tools, but also so-called “virtual tools”. Here “virtual tools” are not to be understood as the tools in the actual sense, but the for
Bucher Heribert
Riedter Bruno
Blum-Novotest GmbH
Browning Clifford W.
Rosenberger Richard A.
Woodard Emhardt Moriarty McNett & Henry LLP
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