Creating a digital twin in a processing centre

Abstract

The invention relates to a processing centre (1) or cutting materials, consisting of a cutting machine (2a) and an adjusting device (5), wherein the adjusting device (5) has a positioning device (8), an illumination device (9, 9a) and an image sensor (11), wherein the positioning device (8) holds a tool unit (10) to be illuminated by the illumination device (9, 9a) in front of the image sensor (11) in such a way that the image sensor (11) is partially shaded by the tool unit (10), wherein the image sensor (11) has a greater maximum extension in at least one spatial coordinates direction than the tool unit (10) in the same spatial coordinates direction, and wherein the outline contour of the tool unit (10) is determined using the value for the extension of the shaded region.

Claims

1. A machining center for cutting materials, consisting of a cutting machine and a setting device, wherein the setting device has a positioning apparatus, an illumination apparatus and an image sensor, wherein the positioning apparatus holds a tool unit to be illuminated by way of the illumination apparatus in front of the image sensor such that the image sensor is partially shaded by the tool unit, wherein the image sensor has a greater maximum extent in at least one spatial coordinate direction than the tool unit in the same spatial coordinate direction, and in that the enveloping contour of the tool unit is determined using the value for the extent of the shaded area and the cutting edge areas of the tool are disregarded to determine a collision-relevant envelope contour from the envelope contour.

2. The machining center as claimed in claim 1, wherein the image sensor has a greater maximum extent in two mutually perpendicular spatial coordinate directions than the tool unit in the same spatial coordinate directions.

3. The machining center as claimed in claim 1, wherein the image sensor is a line sensor that extends in a first spatial coordinate direction and progressively measures in several successive steps along a second spatial coordinate direction perpendicular thereto, wherein the extent of the line sensor in the direction along the first spatial coordinate direction is greater by at least a factor of 20 than along the second spatial coordinate direction.

4. The machining center as claimed in claim 1, wherein at least the line sensor and the light source move in the direction of the second spatial coordinate direction after each measurement.

5. The machining center as claimed in claim 1, wherein the workpiece moves in the direction of the second spatial coordinate direction after each measurement.

6. The machining center as claimed in claim 1, wherein the illumination apparatus emits parallel, better still polarized and preferably coherent light.

7. The machining center as claimed in claim 1, wherein the light beam(s) of the illumination apparatus are not focused on the tool unit.

8. The machining center as claimed in claim 1, wherein the signal strength that a single pixel delivers under the incidence of light is evaluated, and a pixel is deemed to be darkened if its signal strength exceeds a certain proportion of a pixel that is considered to be detected as 100% illuminated, preferably 75%.

9. The machining center as claimed in claim 1, wherein the positioning apparatus is designed such that the tool unit is able to be set in rotation during the measurement.

10. The machining center as claimed in claim 1, wherein the machining center has a measuring chamber that is able to be darkened substantially completely and that preferably has light-absorbing inner surfaces.

11. The machining center as claimed in claim 1, wherein the rotating tool unit is positioned in front of a measuring grid and in that a digital image of the measuring grid with the tool unit in front of it is recorded.

12. The machining center as claimed in claim 1, wherein the positioning apparatus is designed such that it holds a tool unit to be illuminated by way of the illumination apparatus in position in front of the image sensor such that the image sensor is partially shaded by the tool unit.

13. The machining center as claimed in claim 12, wherein extent or length of the shaded area is to be determined with an accuracy of at least 0.5 mm, in particular at least 0.25 mm, ideally of at least 0.1 mm.

14. A method for creating a digital twin of a tool unit consisting of a tool holder and a tool insert, wherein the tool unit is positioned in front of an image sensor that is divided into individual pixels for which it is output whether the pixel in question is illuminated or underilluminated, and in that the tool unit is illuminated with at least one beam consisting of directed light that is either reflected from the tool unit or impinges on the image sensor, and in that the enveloping contour of the tool unit is calculated from the pixels that are wholly or partly shaded by the tool unit and are therefore underilluminated and the envelope contour of the tool unit is used for making the digital twin or the digital image of the tool unit in order to simulate a machining process with the digital twin or the digital image, so that collision monitoring can be carried out, and the cutting edge areas of the tool are disregarded to determine a collision-relevant envelope contour from the envelope contour.

15. The method as claimed in claim 14, wherein the tool unit is set in rotation during the measurement.

16. The method as claimed in claim 15, wherein the rotational speed is high enough that a shadow is cast, which is able to be recognized as a shadow that is cast with stationary lines.

17. The method as claimed in claim 16, wherein, due to the rotation, all of the pixels that lie at least temporarily in the area of the shadow that is cast deliver only an average signal strength that is far enough from the signal strength of a 100%-illuminated pixel that the pixel in question is recognized as shaded, in particular when its average signal strength is at most 75% of a pixel.

18. A method for creating a digital twin of a tool unit consisting of a tool holder and a tool insert wherein the preferably rotating tool unit is positioned in front of a measuring grid and a digital image of the measuring grid with the tool unit in front of it is then recorded and the length of the measuring lines crossing in two spatial directions—which are preferably orthogonal—is then determined, wherein, for measuring lines whose length is shorter than that of an undisturbed continuous measuring line in the same direction, the position at which the measuring line ends is determined and the enveloping contour and thus the image of the tool unit is calculated from the end points thereby obtained—preferably by interpolation between immediately adjacent end points, and in that the envelope contour of the tool unit is used for making the digital twin or the digital image of the tool unit in order to simulate a machining process with the digital twin or the digital image, so that collision monitoring can be carried out, and the cutting edge areas of the tool are disregarded to determine a collision-relevant envelope contour from the envelope contour.

19. A device for performing a method as claimed in claim 14.

20. The use of the shadow that is cast by a rotating tool unit on an image sensor that delivers an electronic light/dark signal in order to determine the enveloping contour of the tool unit within the scope of a computational collision check along a predetermined machining path and through a workpiece to be cut, wherein the tool unit is a complete tool unit comprising a tool and a tool holder, and the cutting edge areas of the tool are disregarded to determine a collision-relevant envelope contour from the envelope contour.

Description

LIST OF FIGURES

(1) FIG. 1 shows a general overview of a machining system according to the invention.

(2) FIG. 2 shows a recording device according to the invention, which works with collimated light and a line sensor.

(3) FIG. 3 shows a side view of FIG. 2.

(4) FIG. 4 shows a variant of FIG. 2, in which however measurements are not performed step by step in the direction along the operating axis of rotation of the tool unit, but rather progressively step by step parallel to the operating axis of rotation of the tool unit.

(5) FIG. 5 shows a variant in which measurements are performed using a fanned-out light beam.

(6) FIG. 6 shows a variant in which measurements are performed using a single laser beam.

(7) FIG. 7 shows a completely alternative type of measurement using a conventional image sensor and a measuring grid.

EXEMPLARY EMBODIMENTS

(8) Principle of the Arrangement According to the Invention

(9) FIG. 1 shows a first exemplary embodiment of a machining center 1 according to the invention.

(10) The machining center 1 in this case consists of a cutting machine 2a with at least one work spindle 2, preferably in the form of a multi-axis milling machine. A cutting tool 4, preferably in the form of a milling cutter, is coupled to said work spindle 2.

(11) The cutting tool 4 is usually coupled with the interposition of a tool chuck 3. The tool chuck 3 holds the cutting tool fixedly in terms of torque, clamped in ready for work. Said tool chuck for its part is coupled fixedly in terms of torque to the work spindle of the machine tool and serves as a standardized interface between the cutting tool and the individual work spindle.

(12) A setting device 5 is linked to the cutting machine 2a and is preferably equipped with a darkened measuring chamber 7.

(13) A tool magazine M is often also likewise linked to the other system components. This is also shown in FIG. 1.

(14) The positioning apparatus 8 is located in the measuring chamber 7. In the simplest case, this is a setting-down plane, which in many cases will have a positively acting positioning aid. The latter is designed such that it ensures that the axis about which the tool unit to be measured in the cutting machine is to rotate always lies at the same location.

(15) The measurement according to the invention is performed on the setting device 5 or in its measuring chamber 7. This measurement delivers the geometric data of an enveloping body that completely accommodates the rotating tool unit 10, that is to say represents what is called an image of the rotating tool unit, which is also called a digital twin. The image of the rotating tool unit corresponds substantially, or with a tolerance of 0.5 mm, preferably 0.25 mm, particularly preferably 0.1 mm, to the actual shape, that is to say what is called the real image, of the rotating tool unit.

(16) The setting device 5 preferably transmits the data obtained in this way to the controller 6 of the cutting machine.

(17) This uses the data delivered by the setting device 5 in order to perform a computer simulation with the aim of verifying that the tool unit, on its programmed path that it is to take on the cutting machine, does not strike anywhere unplanned and is thereby damaged or causes damage itself.

(18) First Variant of the Actual Measuring Arrangement

(19) FIG. 2 shows a basic first variant of the measuring arrangement used for the measurement according to the invention.

(20) A light source 9 that usually generates parallel-oriented light beams is used.

(21) For this purpose, a pinhole aperture 9a arranged behind the actual lamp in the beam direction is preferably used. This serves as a point light source.

(22) The light rays Li emitted thereby are dispersed by a scattering lens 12 in such a way that they run substantially parallel, that is to say their focal point is at infinity or substantially at infinity.

(23) According to the invention, what is known as a collimator is used.

(24) In order to keep the “twilight area” that forms the light/dark boundary on the image sensor as small as possible, it may be a sensible option to additionally use a polarization filter, which is not shown here in the figure.

(25) A slotted aperture, likewise not shown here, may optionally be provided, this ensuring that only a light curtain is output overall, the extent of said light curtain being such that its cross-sectional surface area corresponds (completely or at least substantially) to the surface area of the image sensor.

(26) An image sensor 11, which is designed here as a line sensor in the sense defined at the outset, is arranged on the other side of the tool unit 10 to be measured and that is preferably set in rotation during the measurement. It should be noted that, in the present example, this line sensor has a greater maximum extent on both sides in a spatial coordinate direction (here specifically that of the X spatial coordinate direction) than the tool unit 10 in the same spatial coordinate direction.

(27) It is likewise able to be seen clearly that the tool unit 10 to be measured casts a shadow in the parallel beam path that is preferably used, which shadow is an image of the rotating tool unit 10.

(28) FIG. 3 shows the arrangement according to FIG. 2 in a side view. In this exemplary embodiment, the measurement is performed step by step in the direction of the subsequent operating axis of rotation L of the tool unit 10. For this purpose, the light source 9, the scattering lens 12 and the image sensor 11 are moved parallel to the operating axis of rotation. For example, the shadow that is cast is then determined every 0.1 mm. For this purpose, travel may be stopped briefly parallel to the operating longitudinal axis, but a snapshot may also be taken “while moving”. This procedure is repeated again and again until a complete image of the rotating tool unit has been created.

(29) Ideally, the light source 9, the scattering lens 12 and the image sensor 11 are arranged on a jointly movable carriage or frame.

(30) As an alternative, the device according to the invention may also be designed such that instead of the light source 9, the scattering lens 12 and the image sensor 11, only the tool unit 10 to be measured is moved in the direction of its operating axis of rotation. For this purpose, the positioning apparatus 8 may be designed as a motor-operated lifting table.

(31) It is noteworthy that the line sensor may alternatively have a greater maximum extent only on one side in a spatial coordinate direction (here specifically that of the X spatial coordinate direction) than the tool unit 10 in the same spatial coordinate direction—which is not illustrated here in the figure. The tool unit to be measured is then only measured in half, from its outer edge to its operating axis of rotation. This not only allows an image sensor with a smaller surface area, but also reduces the amount of data processing, thus speeding up the work process.

(32) It is likewise noteworthy that, instead of the conventional light source, a bar with a plurality of laser beams arranged next to one another and emerging parallel to one another is preferably used. Laser beams provide coherent light. This has the enormous advantage that practically no “twilight area” occurs between the light/dark boundary. Measurements are therefore able to be performed very precisely using simple means.

(33) In this case, the bar may be supplied by a number of laser diodes lying next to one another on said bar, for example in accordance with the template in patent EP 0 486 175.

(34) However, it is preferably supplied by a single, mostly central laser source. Its light beam is split several times by a beam splitter. It is then guided via optical conductors, usually in the form of glass fibers, to the individual outlet openings in said beam.

(35) In this laser embodiment, the number and the distance of the individual laser sources or laser outlet openings and the number and the distance of the individual pixels or pixel clusters responsible for a laser beam are matched to one another. They then usually correspond to one another.

(36) Second Variant of the Actual Measuring Arrangement

(37) The function and structure of this second variant, shown in FIG. 4, correspond to that of the first variant—with the exception of the differences or options described explicitly below.

(38) What has been described for the first variant, including all conceivable modifications, thus also applies here.

(39) The difference is that, in this case, measurements are not performed step by step in the direction along the operating axis of rotation L of the tool unit 10 to be measured, but rather perpendicular thereto, that is to say the greatest length of the line sensor is aligned parallel to the operating axis of rotation L.

(40) This makes it very easy to measure only half of the tool unit to be measured, from its outer edge to its operating axis of rotation, and thus to realize the advantages specified above.

(41) A further option, which may also be used in the first variant, is illustrated in FIG. 4: Instead of a conventional lamp with a downstream collimator, a diode or laser bar is used to form a crowd of light beams arranged in a line, these being formed in the manner of a flat light curtain.

(42) Third Variant of the Actual Measuring Arrangement

(43) FIG. 5 shows a further variant of the measuring arrangement according to the invention.

(44) Instead of a light curtain consisting of collimated light, a fanned-out light beam is preferably used here.

(45) If speed is important, such an inherently optically fanned-out light beam is recommended. The light beam may be optically fanned out in such a way as to give for example a triangular, increasingly widening light beam, as shown in FIG. 5.

(46) An image sensor, for example a line sensor as described above, is again mounted behind the tool unit to be measured.

(47) It is able to be seen clearly that the fanned-out light beam preferably exposes the entire linear image sensor at once. The fanning out of the light beam however results in a kind of parallax, which is also able to be seen clearly in FIG. 5—the shadow that is cast appears to be wider than justified by the size of the tool unit to be measured. However, the parallax error is easily able to be calculated mathematically and thereby corrected.

(48) In this embodiment, it is particularly expedient if a laser whose light beam is subsequently fanned out, extensively or into individual sub-beams, serves as light source. This is because, despite the fanning out, the light naturally remains coherent (when fanning out into individual sub-beams) or at least its very precise fan is present (with extensive, as it were “blurred” fanning out), resulting in a good detectable light/dark boundary.

(49) The light fan may be aligned horizontally and be able to be moved vertically or vice versa.

(50) If a line sensor of the type described above is used, it is moved linearly in synchronism with the light fan, as likewise already described above.

(51) Fourth Variant of the Actual Measuring Arrangement

(52) As an alternative, instead of the fanning out, a single at least substantially straight light or laser beam may also be used, this being deflected for example step by step via a pivoting mechanism or via optics such as a discrete mirror or an electrically controllable micromirror matrix, in the manner shown in FIG. 6.

(53) The deflection in each case takes place in such a way that it impinges or would have to impinge on the image sensor if the tool unit to be measured were not in the way.

(54) In this case too, the silhouette of the tool unit to be measured may easily be determined with mathematical correction.

(55) Fifth Variant of the Actual Measuring Arrangement

(56) FIG. 7 shows a further, conceptually fundamentally different variant of the measuring arrangement according to the invention.

(57) This is a measuring arrangement that uses a special method for creating a digital twin of a tool unit 10 consisting of a tool holder or chuck 3 and a tool 4, as described at the outset.

(58) The measuring grid 14, which consists of orthogonally crossing lines, and the tool unit arranged in front of it are able to be seen clearly.

(59) The work here is usually performed using a conventional image sensor, as is used for digital cameras. The image sensor is arranged on the diametrically opposite side of the tool unit to be measured in relation to the plane containing the measuring grid.

(60) The image sensor, which cannot be seen in FIG. 7, is designed such that it records a digital image by way of which the length of the individual measuring lines is able to be determined in the horizontal and vertical direction. Completely vertical or horizontal continuous measuring lines are ignored. The measuring lines that are not completely continuous, because they are partially covered by the tool unit to be measured, are determined.

(61) The distance from the edge of the measuring grid at which the respective measuring line ends is then for example determined. The respective end point corresponds to a point on the enveloping contour of the tool unit that preferably rotates during the measurement. If a linear or higher-order interpolation is then for example performed between the respectively adjacent end points, then the image that essentially corresponds to the enveloping contour of the tool unit is thereby obtained.

(62) Options for all Variants

(63) In general, it should be noted that the usable cutting edge areas of the tool must be disregarded for any collision analysis. This is because the cutting edge areas of the tool are allowed to dip into the workpiece without a collision taking place.

(64) In order to exclude the usable cutting edge areas, the option exists to adopt the information about the position of the usable cutting edge areas from the tool preset and the measurement carried out in the process, and then to accordingly computationally trim the image generated according to the invention.

(65) As an alternative, it is possible to color-code the cutting edge areas on the real tool and then to automatically recognize the colored areas. Such color-coding may be carried out for example using a spray made from UV luminescent paint, which only exhibits a recognizable light reflection under UV light, but otherwise behaves transparently.

(66) A correspondingly emitting light source and a further sensor positioned on the side of the light source are then used, which sensor is able to recognize the surface area indicated by the UV luminescent paint such that said surface area is able to be taken into consideration.

(67) As an alternative, manual marking may be performed on the digital image, or, which is often simpler, an aperture may be set before the recording according to the invention is performed. This aperture shades the entire usable cutting edge area and leaves a noticeable shadow pattern on the image sensor. This may easily be recognized as an area that is not to be taken into consideration for determining the collision-relevant enveloping contour.

(68) Further Functions

(69) If the tool units, tools or tool holders that are to be measured are appropriately marked, then they are able to be recognized automatically. What is known as a data matrix code, a bar code, other machine-readable tags and electromagnetic data carriers such as for example RFID chips are conceivable here. An EEPROM or flash memory or the like is advantageously used on the RFID chip. Additional reading units, such as for example read/write heads for RFID chips or scanners for bar codes, may under some circumstances be necessary for this purpose.

(70) The newly created digital twins of a tool, of a tool holder or of a tool unit may be compared with existing datasets and thereby identified.

(71) If the individual components of a tool unit are identified, a parts list for the entire tool unit may be created from the data, possibly with the addition of assembly instructions. Geometric data may also be stored together with the parts list, for example the total length of the tool or of the tool unit.

(72) On the basis of the digital twins of the tool units or of the individual tools or tool holders, alternative or similar tools that are already used for other machining cases may be determined. It is thus easily possible to determine and suggest an alternative tool unit to be used if a potential collision or, in any case, an excessively small clearance is established.

(73) It is thereby also possible to minimize the tool inventory if necessary, since several similar tools may then be replaced by a common design.

(74) The method according to the invention digitizes the existing physical tool units or tools and tool holders quickly and easily.

(75) It is therefore easy to generate an electronic database including individual components.

LIST OF REFERENCE SIGNS

(76) 1 machining center 2 work spindle 2a cutting machine 3 chuck or tool holder 4 cutting tool 5 setting device 6 controller of the cutting machine 7 darkened measuring chamber 8 positioning apparatus 9 light source 9a pinhole or slotted aperture (lamp side) 10 tool unit to be measured 11 image sensor 11a aperture or slotted aperture (image sensor side) 12 scattering lens 13 not used 14 measuring grid M magazine of the tool changer or tool magazine Li light beam or light beam path L operating axis of rotation of the tool unit