DE102007053993A1 - Method and device for tool measurement - Google Patents

Abstract

For measuring tools (2), in particular their cutting edges (3, 4, 5), the vehicle is taken with a camera having a focal plane (14) and shallow depth of field. As the tool is rotated, images are taken to extract the data from the cutting edge.

Description

The The invention relates to a method and a device for fast and precise measurement of cutting edges of tools such as drills, step drills, milling cutters, hobs, Taps or similar.

It is often necessary to measure tools for cutting workpiece machining with regard to selected parameters. For example, it may be desired to determine the effective diameter generated by a tool. This suggests the DE 199 27 496 A1 a measuring device, in which the tool is brought into the beam path between a lighting device and an image pickup device. The shadow cast of the tool is picked up by the image capture device. The image pickup device has a depth of field range ≥ 10 mm. When the tool rotates, a sequence of still images is recorded. The contour maxima are then determined in the image sequence so that finally an envelope is determined which maps the respective diameters at different axial positions of the tool.

Though This method can be used to define the contour of a tool find out, however, can be determined on the basis of this data certain Do not perform machining on the tool. Especially This method does not provide information about the exact Cutting edge course but only over the radius the cutting edge. Information about the respective angle a cutting point with respect to the tool axis hen hen lost.

Next z. B. from the U.S. Patent 5,151,609 as well as from the DE 10 2004 047 928 A1 Measuring method known that record a three-dimensional height profile of spatially trained workpieces using a camera having a sharply defined focal plane. By adjusting the distance between the camera and the three-dimensional measurement object, for example by moving the camera or the measurement object, images are obtained which in each case focus only on the part of the measurement object lying in the focal plane. The XYZ positions of the individual, sharply imaged parts of the measurement object can then be determined from the images successively obtained by adjusting the distance between the camera and the measurement object.

Such Methods are suitable for recording the height profile of three-dimensional non-intersecting objects, but not directly for surveying of milling cutters, drills or the like.

From that Based on the object of the invention, a method as well as a To create a device that makes cutting tools simple, precise and let it measure quickly.

This object is achieved by the method according to claim 1 as well as with the device according to claim 11:
According to the invention, a rotary positioning device is used to measure the tool, with which the tool can be controlled to rotate about its axis of rotation, wherein the individual angular positions are detected by a corresponding Winkelaufnehmer and optionally available as measured values. For measuring further serves an image pickup device, for example in the form of a camera whose optics defines a focal plane, only lying within the focal plane object parts are sharp and all other object parts are blurred and mapped only in their projection in the focal plane. Strictly speaking, the focus plane is surrounded by a plane space area, which is extremely short and thus almost planar in the direction of the optical axis of the camera, within which a sharp image is obtained. The depth of field in the direction of the optical axis, ie in the Z direction, is preferably less than 1 mm, preferably a few 100 μm.

to Measurement will be the tool and the image capture device so in Reference to each other set that the axis of rotation of the tool lies in the focal plane. For very small tools whose diameter is less than the object field of the image pickup device, can the rotation axis the optical axis of the image recording device (Z-axis) to cut. The image pickup device thus takes two each other 180 ° opposite peripheral portions of the Tool at the same time. In this case, the tool must be for Measurement can be rotated by only 180 °. Otherwise will be the axis of rotation of the tool and the optical axis against each other offset the edge of the tool appearing in the picture approximately in the middle or, if appropriate, elsewhere in the picture. In this case, the tool becomes the measurement rotated by (preferably exactly) 360 °.

In the sweep, images are continuously taken during the rotation of the tool, resulting in a first group of images. These are recorded, for example, at angular intervals of one degree. Thus, the image pickup device has generated and stores a first group of images from a first peripheral portion. The measuring run is continued by adjusting the tool and the image recording device in the direction of the rotation axis of the tool, optionally taking into consideration a wobble pre-correction, in relation to one another the image pickup direction sees the next subsequent peripheral portion of the tool. Again, as the tool rotates, it captures a group of images, now the second group. This process continues until pictures are taken of the entire tool. At the same time or after that, data processing takes place. In this, the imaged cutting edges are determined in the images of each group. Only the sharp part of the cutting edge is assigned the current rotation angle. In addition, by image processing routines, such as edge finder routines, the X and Y values of the cutting edge to be measured in the image plane can be determined and assigned to this rotation angle. The obtained value triplet (X, Y and Z) is stored. The adjoining value triples each form a data set that defines a cutting edge.

On In this way, all cutting edges of the tool are found and measure. Per cutting edge, a record can be generated, the as a basis for further processing of the tool, For example, a grinding process or the like can serve.

The explained method can with refinements and modifications be executed. For example, the tool at the measurement run continuously or in steps rotated become. Furthermore, although it is not mandatory but advantageous, if the pictures of the peripheral sections overlap connect to each other. Thus, data redundancies are avoided.

Further it may be advantageous in the resulting data quantity to be meticulous Make filterings. For example, it may be possible in individual cases that cutting edges are not based solely on the criterion "sharpness" can be seen. Also other parts of a tool, for example cylindrical or partially cylindrical sections, one can cause sharp picture. Here are two criteria be applied to distinguish such portions of cutting edges.

One The first criterion is that cutting edges, at least so far they have a helical shape, d. H. Have slope, only in one Part are shown sharp, piercing the focal plane. neighboring Areas are out of focus. The data filter must be longer in this case discard contiguous sharply displayed image parts. It will then only such sharply imaged image parts the record assigned to the cutting edge, in the current image, only one represent short edge section. It can be an upper limit fixed for the length of the sharp image area become. In addition, the criterion can be provided that the sharp imaged short edge portion in the previous image or successor image of the recorded image sequence to the sharp Section of the current image (gapless) connects. In other words, the filter maps the cutting edge data set only those sharp parts of the picture, which become with rotation of the tool move through the picture.

at Tools whose cutting edges run axially fails this criterion but. Here, however, as in the aforementioned case also, in addition or even a second stronger criterion applied become. This criterion or filter rejects all parts of the picture that are over a rotation angle range can be shown sharply, the one Exceeds limit. This limit can be, for example Fractions of a degree or several degrees.

Further Details of the invention will become apparent from the description. These is limited to essential aspects of the invention and other conditions. The drawing discloses further details and is to be used additionally.

It demonstrate:

1 a measuring device for carrying out the measuring method according to the invention in a schematic side view,

2 geometric relationships in the implementation of the measurement on the tool in a schematic representation,

3 and 4 Pictures taken by the image recording device in exaggerated schematic representation,

5 a block diagram illustrating the data processing operation associated with the measurement and

6 taken pictures with focus window to illustrate the measurement method.

In 1 is a measuring device 1 illustrated for optical measurement of a tool 2 serves. The tool 2 can be a drill, cutter or similar tool. It has one or preferably a plurality of peripheral cutting edges 3 . 4 . 5 on. These can be parallel to one of the tool 2 fixed axis of rotation 6 arranged or, as shown, be at a pitch angle, so that they have, for example, helical shape. The tool 2 may be a milling tool, a drill, a step drill or other, arranged for cutting workpiece machining cutting edges having tool.

To the measuring device 1 heard a recording 7 . 8th for the tool 2 , where the recording 7 . 8th is set up to use the tool 2 pick up and position precisely. In particular, the recording can be the tool 2 in defined rotational positions about its axis of rotation 6 move and hold there. In addition, the recording 7 connected to a drive device and provided an angle encoder to the tool 2 On the one hand defined to rotate and on the other hand to implement the rotational positions in measured values.

The measuring device 1 also has an image pickup device 9 , for example in the form of a camera 10 with a lens 11 on, its optical axis 12 is vertically oriented in the present case and coincides with the Z-axis. However, the optical axis does not necessarily have to be perpendicular to the xy plane. It is z. B. inclined in hobs, taps and the like against the z-direction. The objective 11 is the tool 2 facing and preferably looks at the chip surface. On the other side of the tool 2 is a lighting device 13 , This is preferably completely in the field of view of the camera 10 that partly from the examinee and tool 2 is blocked.

The lighting device 13 is together with the image capture device 9 movable in the X direction parallel to the axis of rotation 6 and preferably set horizontally. In addition, the image pickup device is 9 z. B. in the Z direction perpendicular to the X-axis vertically adjustable. If desired, it may also be adjustable in the Y direction, the Y direction being a horizontal direction oriented at right angles to the Z axis and the axis of rotation. It is understood that the axes can be spatially differently aligned with the same relative orientation; z. For example, the x-axis may be oriented vertically.

The objective 11 the image pickup device 9 is such that it is a focal plane 14 sets. All within the focal plane 14 lying structures are shown sharply. All outside the focal plane 14 lying structures are not sharp and only shown as a projection. The blur preferably takes only a few 100 microns from the focal plane 14 removed in such a way that the relevant image parts are clearly qualified as blurred by automatic contrast measurement. The depth of field may be limited to a few 10 μm.

To the image recording device 9 An image processing device, which is connected to the image recording device, is connected 9 analyzed images and from these the cutting edges 3 . 4 . 5 extracted and missing pointwise. This works as follows:
It will open 2 directed. The tool shown there 2 has several, z. B. two cutting edges 3 . 4 on, which directly adjoin chip spaces 15 . 16 connect. For measurement, the focal plane is first 14 the image pickup device 9 precisely on the axis of rotation 6 set so that the rotation axis 6 in the focal plane 14 runs. For this example, a corresponding doctrine is used by the recordings 7 . 8th is picked up and the one sharp edge on the axis of rotation 6 or parallel to this. Is the device 1 adjusted to that extent, becomes the tool 2 from the recordings 7 . 8th added. The image capture device 9 For example, it is now positioned to have a first peripheral portion 17 ( 1 ).

The geometric relationships are in 2 illustrated. The tool 2 is now starting from an initial rotational position with a speed limited by the frame rate of the camera and the angular resolution by 360 ° about the axis of rotation 6 turned. This z. B. first, the cutting edge 3 and then the cutting edge 4 the focal plane 14 , While the tool 2 turns, picks up the image capture device 9 constantly taking pictures. Each image becomes the current rotational position of the tool 2 assigned. For example, for each degree or at a finer desired angular resolution, an image is also taken for each tenth of a degree. This results for the peripheral portion 17 a first group 19 of pictures, as in 5 is symbolically illustrated. The pictures of the group 19 are each silhouettes of the tool 2 , The tool 2 covers part of the between the illumination device 13 and the lens 11 given beam path according to 2 ,

In each captured image, a more or less sharp cut-off line is seen by the tool 2 is caused. This cut-off may be from the cutting edge 4 or from other parts of the tool 2 originate. 3 illustrates such an image of the image stack 19 , The cutting edge 4 marked there the light-dark border, where in 3 the hatched area represents the dark picture area in which the tool 2 the lighting device 3 shades.

The cutting edge 4 is due to their pitch angle obliquely to the focal plane 14 and pierces them in one point 20 , There and in the immediate vicinity is the cutting edge 4 sharply depicted. In the neighboring areas 21 . 22 it is out of focus and projected into the xy plane. The image of the tool 2 according to 3 at the rotation angle ø1 its contrast maximum 20 at the point X1, Y1. Will the tool 2 rotated further, the contrast maximum moves 20 , like it 4 shows. At the angle of rotation øk it has the position Xk, Yk.

The same applies to another group of pictures 23 , which in a subsequent measuring operation on the peripheral portion 18 has been recorded.

As 5 illustrates, provides the image processing device 1 thus initially a dataset 24 for each peripheral section 17 . 18 (and possibly further peripheral sections) groups 19 . 23 (optionally further) of images. In these pictures are largely blurred illustrations of the tool 2 Each image has one or more contrast maxima.

In the following post-processing, the amount of data becomes 24 with a filter 25 processed. This extracts from each image of the groups 19 . 23 only the sharply imaged, ie high contrast image parts around the point 20 around. The procedure is off 6 seen. Contrast maxima are found by moving a focus window in a search direction through the image associated with angle ø1. The focus window preferably has a width that corresponds to the depth of field. This avoids, on the one hand, that blurred edge areas are included in the measurement, which would lead to measurement uncertainties. On the other hand, the measurement process is fast because the focus window captures all sharp parts of the image. The measurement of the cutting edge, ie the determination of X1 and Y1 and thus the determination of the data triplet {X1, Y1, ø1}, takes place (only) in the focus window, which is thus at the same time the measurement window.

From the data obtained in the measurement windows of all groups 19 Images are combined for each measured cutting edge one record at a time. The cutting edge is composed of cutting edge sections. The cutting edge shape can optionally be smoothed by calculation. In addition, the angular resolution can be increased by interpolation. Polynomials, preferably of the 4th degree, and preferably over a plurality of successive images of a group, are suitable for the interpolation.

Optionally, a cutting edge extrapolation can be made from the data obtained from a stack. This allows or facilitates tracking of cutting edges as they move from one group to the next subsequent group. This can be done from the records that come from the respective groups 19 . 20 have been obtained, those data sets are combined that belong to a cutting edge. This results in records describing cutting edges extending over several groups of images.

Should a cutting edge at a certain point between the axial Ends of the measuring range ends (or starts), changes the number of cutting edges detected at one revolution on one specific location of the focus window in a stack of images. A complete cutting edge search can detect such. Preferably, the complete cutting edge search in a focus window preferably at an end (or beginning) of a picture carried out.

The Filtering the data (detection cutting edge / non-cutting edge) can be like described on the basis of the geometry of the cutting edge or on the basis of quality indicators be performed. The quality indicators are z. B. a sharpening criterion that within each picture on the focus window is tracked. It can alternatively also always the same focus window through multiple or all images of a stack be followed. The maximum (or minimum) of the quality score identifies the valid measured values of the cutting edge. This one These measures can be combined become.

additional or alternatively, it may be checked at compilation of the record be that or at least the value Xk of the data triplet {Xk, Yk, øk} of an image of the value Xk of the adjacent one Distinguishes data triplets. If this is not the case, the data triplet is located {Xk, Yk, øk} probably on a circle outline and heard thus not directly to a cutting edge. Such data triples can be discarded by the filter d. H. from the record be removed.

Every record 27 to 29 Contains the complete spatial definition of each cutting edge 3 . 4 . 5 , can optionally undergo arithmetic processing steps, for example, a wobble correction, and is available as a measurement result for further processing of the tool.

The filter 25 Optionally, it can also monitor the change in the sharpness of the individual parts of the image, which depends on the time or on the angle of rotation øk (k = 1 ... n; for n images). From this, it can sort out and discard those parts of the image whose sharpness is high, but does not change over a larger range of the rotation angle ø. As the upper range limit, a rotation angle value ømax can be defined. The remaining sharply-imaged parts of the images can be accessed through a spatial edge finder routine in a module 26 to chains are composed, consisting of the data triplets {Xk, Yk, øk} and each depict a cutting edge. These belonging to a cutting edge records are z. B. as records 27 . 28 . 29 output.

For measuring tools 2 , especially in particular their cutting edges 3 . 4 . 5 , the tool is taken with a camera that has a focal plane 14 and shallow depth of field. As the tool is rotated, images are taken to extract the data from the cutting edge.

1

measuring device

2

Tool

3, 4, 5

cutting edges

6

axis of rotation

7, 8th

admission

9

Image recording device

10

camera

11

lens

12

optical axis

13

lighting device

14

focal plane

15 16

gullets

17 18

peripheral portion

19

group

20

Point

21 22

areas

23

group

24

amount of data

25

filter

26

module

27 28, 29

record

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 19927496 A1 [0002]
• US 5151609 [0004]
• DE 102004047928 A1 [0004]

Claims (11)

Method for measuring tool cutting edges ( 3 . 4 . 5 ), in which in a measuring run: a) a tool ( 2 ), the at least one peripheral cutting edge ( 3 ), in a rotary positioning device ( 7 . 8th ) is arranged so that its axis of rotation ( 6 ) in the focal plane ( 14 ) an image recording device ( 9 b) the image recording device ( 9 ) at a first peripheral portion ( 17 ) of the tool ( 2 ) is arranged so that the tool ( 2 ) only a part of the image field of the image recording device ( 9 ), c) the tool ( 2 ) while maintaining the distance between the image recording device ( 9 ) and the axis of rotation ( 6 ) of the tool ( 2 ) by a fixed angle of at least 180 ° about its axis of rotation ( 6 ) is rotated to all in the peripheral portion ( 17 ) existing cutting edges ( 3 ) at least once through the focal plane ( 14 ) d) during the rotation of the tool ( 2 ) a group ( 19 ) of images and to which the respective value of the rotation angle (ø) is assigned, which the tool ( 2 ) when taking the respective image, e) after the rotation, the image recording device ( 9 ) and the tool ( 2 ) with respect to each other in the direction of the axis of rotation ( 6 ) are adjusted to one another such that the image recording device ( 9 ) to another peripheral section ( 18 f) steps c) and d) are repeated until, for all circumferential sections of interest ( 17 . 18 ) one group each ( 19 . 23 ) of images and in a data processing operation: g) in the images of each group ( 19 . 23 ) illustrated cutting edges ( 3 . 4 . 5 ) and in the focal plane ( 14 ) and thus sharply imaged part ( 20 ) of the cutting edge ( 3 . 4 . 5 ) associated with the image value of the angle of rotation (ø) and assigned and for this part ( 20 ) of the cutting edge ( 3 . 4 . 5 ) determined by image processing, in the focal plane ( 14 ) lying values (x, y) are assigned. Method according to claim 1, characterized in that that the value of the total to be traversed angle of rotation for all peripheral sections is set to 360 °. Method according to claim 1, characterized in that the tool ( 2 ) is rotated in the measuring run in a single predetermined direction of rotation. Method according to claim 1, characterized in that the tool ( 2 ) is continuously rotated during image acquisition. A method according to claim 1, characterized in that the adjustment of the image recording device ( 9 ) and the tool ( 2 ) from a peripheral portion ( 17 ) to the next peripheral section ( 18 ) is dimensioned such that the images of the one peripheral section ( 18 ) without overlapping to the images of the other peripheral portion ( 17 ) connect. Method according to claim 1, characterized in that that the data processing process as post-processing after completion the measuring run is performed. Method according to claim 1, characterized in that from the pictures of all groups ( 19 . 23 ) only the data of the at least one cutting edge ( 3 . 4 . 5 ) and all other data is discarded. A method according to claim 1, characterized in that in the images to cutting edges ( 3 . 4 . 5 ) associated image parts based on their sharpness progression from not to cutting edges ( 3 . 4 . 5 ) belonging image parts are distinguished. Method according to claim 1, characterized in that image parts whose sharpness remain sharp over a rotation angle range are not used as cutting edges ( 3 . 4 . 5 ) and discarded. A method according to claim 1, characterized in that for the evaluation of the images of each stack ( 19 . 20 ) is used in each case a focus window whose width of the depth of field of the lens ( 11 ) corresponds to the length of the sharp-edged cutting edge to be measured in the x-direction. Apparatus for carrying out the method according to Claim 1.