Optics: measuring and testing – Shape or surface configuration
Reexamination Certificate
2001-01-04
2003-06-24
Mathews, Alan A. (Department: 2877)
Optics: measuring and testing
Shape or surface configuration
C356S394000, C382S152000
Reexamination Certificate
active
06583883
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for measuring a rotary tool, rotatable about a rotation axis and mounted in a tool mounting having a tool contour determining the working dimensions of the rotary tool using a measuring device, which has an optical image acquisition device with an optics orientable onto the rotary tool for acquiring images of said rotary tool and an image processing device connected to the image acquisition device for the computer-aided evaluation of the acquired images, as well as a measuring device suitable for performing the method.
2. Description of the Prior Art
Rotary tools are e.g. used in working machines for the material-removing and in particular cutting working of workpieces. For example for the manufacture of precise holes or bores use is made of cutting devices in which the working or active dimensions of the tool are determined by a replaceable and adjustable tool cutting edge. In order to be able to respect the presently required, very close manufacturing tolerances and demands concerning the surface quality, bore shape, etc., such rotary tools must be measured in micrometer-precise manner and optionally precisely set for the particular application. Apart from the requirement of high precision measurement, with respect to optimized production sequences there is also a need for high speed of the tool measurement and setting.
In order in the case of manual tool setting to be able to fulfill the contradictory requirements of speed and precision, nowadays in place of the previously conventional tool measuring and setting devices with projectors, increasing use is being made of measuring devices, which comprise an optoelectronic image acquisition device and an image processing device connected thereto for computer-aided evaluation of acquired images. The image acquisition device normally has a CCD video camera, whose optics are aligned with the tool to be measured or on the area of the tool contour to be measured. The arrangement between the optics and the tool is to be so set during measurement that the rotation axis of the rotary tool is oriented perpendicular to the optical axis of the optics and passes through the area of the sharpness or definition zone of the optics. The camera is normally placed on a slide or carriage, which is movable in two directions perpendicular to the optical axis. Conventionally a direction running parallel to the tool mounting axis is called the Z-direction and a radial direction perpendicular thereto the X-direction. In the case of rotary tools, whose rotation axis in the case of a correct setting coincides with the tool mounting rotation axis, the Z-direction corresponds to the tool longitudinal direction, so that a Z-value corresponds to a tool length and a X-value to a tool radius.
A conventional, image processing-aided measuring sequence commences with an operator moving the tool contour to be measured (tool cutting edge) roughly into the image field of the optics with the aid of the X-Z-slide. The tool cutting edge then becomes visible in a monitor connected to the image acquisition device. In the following step the tool cutting edge to be measured is focussed in that the operator rotates the rotary tool about its rotation axis until the tool contour to be measured is located in the sharpness zone of the optics and is consequently focussed. The focussing step critical for the precision of the measurement is facilitated in certain known devices with image processing by a focussing display visible on the monitor. The focussing display is e.g. in the form of an analog bar display with colour change between red (still unsharp) and green (sharpness position) and guides the operator during focussing. Within the computer the deflection of the cutting edge contour in the radial direction (X-direction) is detected and evaluated for the focussing display. This is generally at a maximum when the tool cutting edge is in the sharpness zone. In practice the operator initially rotates the tool beyond the sharpness position and then slowly back for the actual measurement into the position of maximum sharpness corresponding to the maximum deflection in the X-direction. This focussing process is facilitated by the focussing display, which guides the operator during the focussing of the cutting edge and ensures an operator-independent focussing.
SUMMARY OF THE INVENTION
The object of the invention is to make available a tool measurement and setting aided by image processing and which permits a precise and at the same time very rapid tool measurement.
For solving this problem the invention proposes a method for measuring a rotary tool using a measuring device, the rotary tool being rotatable about a rotation axis and being mounted in a tool mounting with, the rotary tool comprising a tool contour determining the working dimensions of the rotary tool;
the measuring device comprising an optoelectronic image acquisition device including optics alignable with the rotary tool for acquiring images of the rotary tool, further comprising an image processing device connected to the image acquisition device for the computer-aided evaluation of acquired images, the method involving the following steps:
placing the area of the tool contour to be measured in an image area of the optics of the optoelectronics image acquisition device;
rotating the rotary tool about the rotation axis;
acquiring a sequence of frames of the rotating rotary tool;
computer-aided evaluation of the frames with respect to at least one image parameter, the image parameter representing a measure for the positioning of the tool contour with respect to a sharpness zone of the optics;
determining a selection frame by computer-aided selection of a frame from the sequence of frames, in which frame the image parameter corresponds to a positioning of the tool contour in the sharpness zone of the optics;
evaluation of the selection frame for determining at least one tool parameter characterizing the tool contour.
The object is also achieved by a measuring device for measuring a rotary tool, the rotary tool being rotatable about a rotation axis and being mounted in a tool mounting, the rotary tool comprising a tool contour determining the working dimensions of the rotary tool; the measuring device comprising:
an optoelectronic image acquisition device with optics alignable with the rotary tool for acquiring images of the rotary tool and;
an image processing device connected to the image acquisition device for the computer-aided evaluation of images acquired by the image acquistion device;
the image processing device comprising a frame grabber for acquiring a sequence of frames of the rotary tool and a computing unit with a working program for computeraided evaluation of the frames, wherein the working program comprises the following steps:
evaluation of the frames with respect to at least one image parameter, the image parameter representing a measure for the positioning of the tool contour with respect to the sharpness zone of the optics;
determination a selection frame by selecting a frame from the sequence of frames, in which frame the image parameter corresponds to a positioning of the tool contour in the sharpness zone of the optics;
evaluation the selection frame for determining at least one tool parameter characterizing the tool contour.
Preferred further developments are given in the dependent claims. The wording of all the claims is hereby made by reference into part of the description.
In the method according to the invention firstly a section of the rotary tool containing the tool contour to be measured is placed in the image field of the optics, which can be brought about by a suitable relative movement between optics and rotary tool. The rotary tool is rotated about its rotation axis and rotation normally only begins when the section to be measured is in the image field of the optics, but optionally also beforehand. During rotation there is an acquisition of a sequence of frames of the rotating rotary tool. These f
Kelch GmbH + Co. Werkzeugmaschinenfabrik
Mathews Alan A.
Nath Gary M.
Nath & Associates PLLC
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