WO2020078902A1 - Procédé et système d'identification d'une pièce à usiner - Google Patents

Procédé et système d'identification d'une pièce à usiner Download PDF

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Publication number
WO2020078902A1
WO2020078902A1 PCT/EP2019/077777 EP2019077777W WO2020078902A1 WO 2020078902 A1 WO2020078902 A1 WO 2020078902A1 EP 2019077777 W EP2019077777 W EP 2019077777W WO 2020078902 A1 WO2020078902 A1 WO 2020078902A1
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WO
WIPO (PCT)
Prior art keywords
workpiece
image
area
identification area
reference area
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP2019/077777
Other languages
German (de)
English (en)
Inventor
Boris Regaard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Trumpf Werkzeugmaschinen SE and Co KG
Original Assignee
Trumpf Werkzeugmaschinen SE and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Trumpf Werkzeugmaschinen SE and Co KG filed Critical Trumpf Werkzeugmaschinen SE and Co KG
Publication of WO2020078902A1 publication Critical patent/WO2020078902A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/03—Observing, e.g. monitoring, the workpiece
    • B23K26/032—Observing, e.g. monitoring, the workpiece using optical means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/0869—Devices involving movement of the laser head in at least one axial direction
    • B23K26/0876—Devices involving movement of the laser head in at least one axial direction in at least two axial directions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/21—Bonding by welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/70—Auxiliary operations or equipment
    • B23K26/702—Auxiliary equipment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K37/00—Auxiliary devices or processes, not specially adapted for a procedure covered by only one of the other main groups of this subclass
    • B23K37/02—Carriages for supporting the welding or cutting element
    • B23K37/0211—Carriages for supporting the welding or cutting element travelling on a guide member, e.g. rail, track
    • B23K37/0235—Carriages for supporting the welding or cutting element travelling on a guide member, e.g. rail, track the guide member forming part of a portal
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00—Arrangements for image or video recognition or understanding
    • G06V10/10—Image acquisition
    • G06V10/12—Details of acquisition arrangements; Constructional details thereof
    • G06V10/14—Optical characteristics of the device performing the acquisition or on the illumination arrangements
    • G06V10/141—Control of illumination
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00—Arrangements for image or video recognition or understanding
    • G06V10/10—Image acquisition
    • G06V10/12—Details of acquisition arrangements; Constructional details thereof
    • G06V10/14—Optical characteristics of the device performing the acquisition or on the illumination arrangements
    • G06V10/145—Illumination specially adapted for pattern recognition, e.g. using gratings
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00—Arrangements for image or video recognition or understanding
    • G06V10/20—Image preprocessing
    • G06V10/24—Aligning, centring, orientation detection or correction of the image
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00—Arrangements for image or video recognition or understanding
    • G06V10/70—Arrangements for image or video recognition or understanding using pattern recognition or machine learning
    • G06V10/74—Image or video pattern matching; Proximity measures in feature spaces
    • G06V10/75—Organisation of the matching processes, e.g. simultaneous or sequential comparisons of image or video features; Coarse-fine approaches, e.g. multi-scale approaches; using context analysis; Selection of dictionaries
    • G06V10/751—Comparing pixel values or logical combinations thereof, or feature values having positional relevance, e.g. template matching
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00—Arrangements for image or video recognition or understanding
    • G06V10/70—Arrangements for image or video recognition or understanding using pattern recognition or machine learning
    • G06V10/74—Image or video pattern matching; Proximity measures in feature spaces
    • G06V10/75—Organisation of the matching processes, e.g. simultaneous or sequential comparisons of image or video features; Coarse-fine approaches, e.g. multi-scale approaches; using context analysis; Selection of dictionaries
    • G06V10/751—Comparing pixel values or logical combinations thereof, or feature values having positional relevance, e.g. template matching
    • G06V10/7515—Shifting the patterns to accommodate for positional errors
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V20/00—Scenes; Scene-specific elements
    • G06V20/80—Recognising image objects characterised by unique random patterns
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/18—Sheet panels
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V2201/00—Indexing scheme relating to image or video recognition or understanding
    • G06V2201/06—Recognition of objects for industrial automation

Definitions

  • the present invention relates to a method for identifying a preferably plate-shaped workpiece, in particular a sheet.
  • the invention also relates to an associated system for identifying a workpiece.
  • a respective workpiece or sheet with a coding for easier tracking.
  • the coding can be applied, for example, in the form of a linear bar code or a 2D code by laser marking to the surface of the workpiece.
  • the coding can also be applied to the workpiece in other ways.
  • DE102017202628A1 describes a method for coding and a method for identifying a plate-like workpiece, the method for coding comprising: defining a coding area, applying one
  • Magnetic layer on the surface of the workpiece and fusing parts of the magnetic layer with the surface of the workpiece by exposing the workpiece to radiation within the coding area.
  • Identifying the workpiece comprises the steps of the method for coding and additionally: storing the coding in a memory device, reading the coding by measuring the local distribution of the magnetization in a reading area, and comparing the stored coding and the read coding.
  • DE102017202629A1 also describes a method for coding, in which a chemical reaction of a base material of the workpiece is caused by irradiation of the workpiece in a coding area and a reaction material is formed within the coding area which has a magnetic remanence that differs from the base material.
  • DE102017202630A1 describes a processing machine for shaping
  • EP2875932A1 describes a method and a device for producing a three-dimensional workpiece which has an information code pattern.
  • the information code pattern is characterized by the microstructure of the
  • the information code pattern can, for example, form a linear bar code or a two-dimensional matrix code, for example a QR code.
  • DE102005022095A1 describes a method and a device for determining a lateral relative movement between a machining head and a workpiece during machining of the workpiece.
  • the surface of the workpiece in the region of the machining head is illuminated with optical radiation, and optical radiation reflected from the surface of the workpiece is repeatedly detected with an optical detector in order to obtain optical reflection patterns of the surface of the workpiece at different times.
  • the lateral relative movement is determined by comparing the successive reflection patterns.
  • the invention has for its object a method and a system
  • Illumination radiation recording an image of the identification area which contains a workpiece-specific reflection pattern of illumination radiation reflected on the identification area, and identifying the workpiece by comparing the recorded image of the identification area with at least one of a plurality of in a storage device stored images of at least partially overlapping with the identification area reference areas, the images each one
  • the method according to the invention does not require a coding to be applied to the surface of the workpiece, rather the surface of the workpiece itself serves as coding for uniquely identifying a specific workpiece.
  • the fact described in DE102005022095A1 cited at the beginning is used that workpieces typically have a surface structure or
  • the workpiece roughness required for this purpose is automatically given in most metal workpieces in particular.
  • the reference area is shown enlarged.
  • the magnification can be selected such that a length of approximately 10 pm on the surface of the workpiece corresponds to a pixel on the detector surface, for example a high-resolution camera.
  • the surface structure and thus also the reflection patterns generated during the illumination are workpiece-specific, i.e. that these make it possible, in the manner of a fingerprint, to uniquely identify the workpiece as a rule or to uniquely assign the workpiece to one of the plurality of workpieces for the images of a respective one
  • Reference area were stored in the storage device.
  • the majority of workpieces, of which images of the reference area are stored in the storage device, are typically workpieces that are to be processed on several processing machines or processing stations of a group, between which the workpieces are transported and possibly
  • the method comprises: illuminating the reference area on the Surface of the or one of the plurality of workpieces with
  • Illumination radiation recording the image of the reference area, which contains the workpiece-specific reflection pattern of illumination radiation reflected on the surface of the workpiece, and storing the image of the
  • Reference area in the storage device To take the picture, the surface of the workpiece is illuminated at least at the reference area. The position of the reference area on the surface of the workpiece is usually fixed.
  • An image (“template”) is recorded from the reference area, which has a predefined size, e.g. 256 x 256 pixels or 32 x 32 pixels on a spatially resolving detector, for example in the form of a camera.
  • the picture can be a grayscale picture, but it is also possible to take a colored picture. Interference radiation can be eliminated by suitable bandpass filters, which are arranged between the spatially resolving detector and the reference area.
  • a lighting power of the illuminating radiation is set or regulated.
  • the illuminating radiation is generated by an illuminating source whose output can be adjusted.
  • the illumination or the illumination power can be adapted to the reflection behavior of the respective workpiece, for example with the aid of a regulation of the illumination, in order to generate an illumination intensity that is optimal for the spatially resolving detector.
  • the brightness of the image can be determined on the spatially resolving detector, for example in the form of an average of the brightness or the intensity of all pixels of the recorded image.
  • the lighting power is adjusted or regulated in such a way that the brightness of the respectively recorded image is always of the same size or lies within a predetermined brightness interval. Comparing images that have a similar brightness is particularly beneficial if one
  • Pattern recognition algorithm or a correlation algorithm is used that does not take into account different levels of brightness, as is the case, for example, with the SAD (“sum of absolute differences”) algorithm.
  • Illuminating taking the image of the reference area and the The image is saved for a plurality of workpieces which are to be distinguished from one another using the method.
  • the illumination and the recording of the image of the reference area and the illumination and the recording of the image of the
  • the two sensor devices can, for example, on different processing machines of a network of
  • Processing machines can be formed, or on two different
  • Signaling connection which can be formed, for example, on a central computer or in the cloud and in which the images of the reference areas of the workpieces to be processed are stored.
  • the image of the identification area can also be recorded with one and the same sensor device.
  • Reference area and / or the identification area through processing optics, in particular through focusing optics, of a processing head for processing the workpiece by means of a processing beam.
  • the reference area or the identification area is usually illuminated coaxially or only slightly inclined to a machining beam which is aligned with the workpiece.
  • Such illumination has proven to be advantageous, since with this type of illumination, illumination radiation reflected from a respective surface area generates very irregular, workpiece-specific reflection patterns in the image on a spatially resolving detector, which facilitate the comparison between the reflection patterns. Also a coaxial observation of the
  • the detector which can be a high-resolution camera, for example, is typically also arranged coaxially with the processing beam or with an extension of the beam axis of the processing beam.
  • the imaging optics are designed such that they are telecentric, at least on the object side. This can be achieved, for example, by arranging an aperture diaphragm in the image-side focal plane of a converging lens of the imaging optics.
  • a similarity measure between the image of the identification area and the image of the reference area is preferably determined by a pattern recognition algorithm.
  • the image of the or a respective reference area and the image of the identification area are correlated in order to determine a similarity measure.
  • Known image processing methods are used for this purpose: For example, difference-based similarity functions (Sum of Absolute Differences - SAD, median absolute deviation - MAD, Mean-squared-Difference - MSD), cross correlation, correlation coefficient or phase correlation can be used.
  • difference-based similarity functions Sud of Absolute Differences - SAD, median absolute deviation - MAD, Mean-squared-Difference - MSD
  • cross correlation correlation coefficient or phase correlation
  • the workpiece to be identified is assigned to the workpiece whose stored image has the greatest similarity to the recorded image, that is to say the image in which the degree of similarity is at a maximum.
  • the degree of similarity can also be determined at the sub-pixel level, as described in DE102005022095A1. In the case of further training, the workpiece is only identified if that
  • Similarity measure between the image of the identification area and the image of at least one reference area exceeds a minimum value. In the event that the similarity measure does not exceed the minimum value for any of the stored images, this indicates that the workpiece to be identified does not match one of the plurality of workpieces for the images of the
  • the identification area is chosen to be larger than that
  • the identification area is larger than the reference area, in particular the identification area and the reference area can have an identical size.
  • the positions of the identification area and the reference area on the surface of the workpiece are typically selected such that the reference area lies within the identification area, i.e. that the (larger) identification area includes the respective reference area.
  • Displacement of the reference area relative to the identification area and / or a different magnification of the image of the reference area and the image of the identification area is taken into account.
  • a lateral offset between the image of the reference area and the image of the identification area can be taken into account, for example, with the aid of a cross correlation, as is described in DE102005022095A1 cited at the outset, since this is one against the other a lateral shift tolerant pattern recognition algorithm.
  • a (slight) lateral offset can be taken into account by displacing the image of the reference area laterally for comparison with the identification area and determining a similarity measure for different values of the amount of the lateral offset.
  • Reference area relative to the image of the identification area can be determined by a rotation-tolerant pattern recognition algorithm, e.g. Optical flow.
  • the recording of the respective image can optionally take place with a different imaging scale.
  • Sensor device more precisely via the imaging scale with which the respective image is recorded, can also be stored in the memory device.
  • the different magnification of the pictures can be
  • Another aspect of the invention relates to a system for identifying a
  • Workpiece comprising: at least one sensor device with: one
  • Illumination source for illuminating an identification area on the surface of the workpiece with illuminating radiation
  • a spatially resolving detector for recording an image of the identification area
  • a workpiece-specific reflection pattern of illuminating radiation reflected on the surface of the workpiece a storage device in which a plurality of images of at least partially overlapping, preferably smaller, reference areas of surfaces of an identification area A plurality of workpieces is stored, the workpiece-specific
  • Contain reflection patterns Contain reflection patterns
  • an evaluation device which is designed or programmed to identify the workpiece by comparing the reflection pattern of the recorded image of the identification area with at least one of the plurality of images of the reference areas.
  • the evaluation device is arranged or can be arranged in the vicinity of the workpiece
  • the evaluation device and in particular also the storage device can be arranged at a basically arbitrary location.
  • the system has more than one sensor device in order to record images of workpieces, it is necessary that the recorded images are stored in a common storage device, to which a respective evaluation device or possibly all of them
  • Sensor devices can access common evaluation device.
  • the workpiece can alternatively be identified in a local evaluation device in or in the vicinity of a respective sensor device which is based on the
  • Storage device can access.
  • the system can form a closed network of processing machines which are arranged at one location, but it is also possible for the processing machines or
  • Processing stations of the network are distributed over several locations and have to be loaded for transport.
  • the system can have two or more sensor devices and that
  • Illumination and recording of the image of the identification area can take place on two different sensor devices. This is particularly favorable or necessary if the workpieces to be identified are transported to different locations in order to enable clear assignment in this case too.
  • the or a further sensor device can serve or be designed to illuminate the reference area on the surface of the workpiece with illuminating radiation, to take an image of the reference area, which the
  • workpiece-specific reflection patterns from on the surface of the workpiece contains reflected illumination radiation, and to transmit the image of the reference area to the storage device in order to store it there.
  • Sensor device can, for example, be permanently connected to a processing head of a processing machine, which can be moved relative to a respective workpiece, so that the identification area or the reference area can be reached in a particularly simple manner by means of the sensor device.
  • the sensor device is designed to illuminate the identification area on the surface of the workpiece and record the image of the identification area through processing optics, in particular through focusing optics, of a processing head for processing the workpiece using a processing beam.
  • the sensor device can be a sensor device that is already available for monitoring a machining process, for example a laser welding or laser cutting process, and can also be used to identify workpieces. It is not absolutely necessary for the sensor device to illuminate the identification area on the surface of the workpiece and to record the image of the
  • Identification area is formed by a processing optics essentially coaxial to the processing beam. Rather, both the illumination source and the spatially resolving detector on the processing head can also be arranged outside the processing optics or outside the housing of the processing head.
  • the evaluation device is designed or programmed to compare the image of the reference area and the image of the identification area, a measure of similarity between the image of the
  • Identification area and the image of a respective reference area preferably to be determined by a pattern recognition algorithm.
  • the workpiece has been described in connection with the method, in that it is assigned to the image of the reference area which has the maximum similarity to the image of the identification area. As described above, it is beneficial if the workpiece is only identified if the similarity measure exceeds a minimum value.
  • the system in particular a respective sensor device, can be designed to select the identification area larger than the reference area.
  • the image of the identification area can cover, for example, the entire detector area of the spatially resolving detector, while the image of the reference area covers only a partial area of the detector area.
  • the evaluation device can also be designed to take into account a rotation and / or a lateral displacement of the reference area relative to the identification area when comparing the image of the reference area with the image of the identification area.
  • Fig. 1 is a schematic representation of an embodiment of a
  • Laser processing machine for cutting processing a workpiece with an identification area and a reference area
  • 3a, b show an image of the identification area
  • 4a, b a representation of the image of the identification area and an image of a reference area of a second workpiece
  • 5a, b show the image of the identification area and a rotated and laterally offset image of the reference area of the second workpiece.
  • FIG. 1 shows a laser processing machine 1 with a laser source 2, a
  • Laser processing head 4 and a workpiece support 5 A laser beam 6 generated by the laser source 2 is guided by means of a beam guide 3 with the aid of deflecting mirrors (not shown) to the laser processing head 4 and is focused therein as well as with the aid of mirrors (also not shown) perpendicular to the surface 8a of a Workpiece 8 aligned, ie the beam axis (optical axis) of the laser beam 6 runs perpendicular to the workpiece 8.
  • the laser source 2 is a C02 laser source.
  • the laser beam 6 can be generated, for example, by a solid-state laser.
  • the laser beam 6 is first used to pierce, i.e. the workpiece 8 is melted or oxidized at a puncture position and the resulting melt becomes
  • the laser beam 6 is then moved over the workpiece 8, so that a continuous cutting contour 9 is formed, on which the workpiece 8 is cut along the laser beam 6.
  • Both grooving and laser cutting can be supported by adding a gas.
  • Oxygen, nitrogen, compressed air and / or application-specific gases can be used as cutting gases 10.
  • Particles and gases that arise can be extracted from a suction device 11
  • Suction chamber 12 are suctioned off.
  • the laser processing machine 1 also comprises a movement device 13 for moving the laser processing head 4 and the workpiece 8 relative to one another.
  • the workpiece 8 rests on the during machining Workpiece support 5 and the laser processing head 4 are moved during processing along two axes X, Y of an XYZ coordinate system.
  • the movement device 13 has one with the help of one
  • Double arrow indicated drive 14 in the X-direction movable portal The laser machining head 4 can be displaced in the X direction with the aid of a further drive of the movement device 13, indicated by a double arrow, in order to move to any machining head positions P in the X direction and in the Y direction in one by the displaceability of the laser machining head 4 or the workpiece 8 predetermined work area to be moved.
  • the laser beam 6 has an (instantaneous) feed speed V.
  • the laser beam 6 is focused on the workpiece 8 by means of a focusing device in the form of a focusing lens 15 in order to carry out a cutting machining on the workpiece 8.
  • the focusing lens 15 is a lens made of zinc selenide, which focuses the laser beam 6 onto the workpiece 8 through a laser processing nozzle 16, more precisely through its nozzle opening 16a, specifically in the example shown onto a focus position F on the upper side 8a of the workpiece 8.
  • the laser beam 6 there forms an interaction region 17 with the workpiece 8, behind which against the machining direction V or against the cutting direction of the
  • Laser cutting process the cutting contour 9 shown in FIG. 1 is generated.
  • a focusing lens made of quartz glass, for example can be used.
  • FIG. 2a also shows a partially transparent deflection mirror 18 of a sensor device 20, which reflects the incident laser beam 6 (for example with a wavelength of approx. 10.6 pm) and, for process monitoring, also makes another partially transparent observation radiation
  • Deflecting mirror 19 transmitted, which also forms part of the sensor device 20.
  • the deflecting mirror 18 is partially transparent for observation radiation in the form of thermal radiation at wavelengths l of approximately 700 nm to 2000 nm.
  • An illumination source 21 of the sensor device 20 serves for the coaxial illumination of the workpiece 8 with illumination radiation 22.
  • the illuminating radiation 22 is transmitted by the further partially transmissive deflecting mirror 19 and by the deflecting mirror 18 and is directed onto the workpiece 8 through the nozzle opening 16a of the laser processing nozzle 16.
  • Illumination source 21 is adjustable.
  • Reflect edge area are used to supply the illumination radiation 22 to the workpiece 8. At least one mirror introduced laterally into the beam path of the laser beam 6 can also be used to enable the observation.
  • Diode lasers or LEDs or flash lamps can be provided as the illumination source 21, which, as shown in FIG. 2a, coaxially, but also off-axis
  • Laser beam axis 24 can be arranged.
  • the illumination source 21 can, for example, also be arranged outside (in particular next to) the laser processing head 4 and directed towards the workpiece 8; alternatively, the
  • Illumination source 21 arranged within the laser processing head 4, but not aligned coaxially to the laser beam 6 on the workpiece 8.
  • the laser processing head 4 can also be used without one
  • Illumination source 21 are operated.
  • the camera 25 can be a
  • Act high-speed camera which is arranged coaxially to the laser beam axis 24 or to extend the laser beam axis 24 and thus independent of direction.
  • images are recorded by the camera 25 in the incident light method in the NIR / IR wavelength range, around that
  • a filter can be arranged in front of the camera 25 if additional radiation or wavelength components are included in the detection the camera 25 are to be excluded.
  • the filter can, for example, be designed as a narrow-band bandpass filter with a half-value width of, for example, approximately 15 nm, which transmits wavelengths l in the range around approximately 800 nm.
  • the laser processing head 4 has an imaging optics 27 for recording an image B1 of a circular identification region 26 shown in FIG. 1 on the surface 8a of the workpiece 8 on a detector surface 25a of the camera 25.
  • the imaging optics 27 have a diaphragm 28 which is rotatably mounted about a central axis of rotation D, so that the position of an eccentrically arranged diaphragm opening 28a moves on a circular arc around the axis of rotation D during the rotation (cf. .
  • observation beam path 23 which passes through an edge region of the focusing lens 15 and is aligned in the convergent beam path after the focusing lens 15 at an angle ⁇ to the beam axis 24 of the laser beam 6, through the aperture 28a arranged eccentrically to the extension of the beam axis 24 of the laser beam 6 and forms an observation beam 23a, which is imaged on the detector surface 25a.
  • an observation direction R1 of the observation beam 23a runs parallel to the direction of the projection in the XY plane or in the workpiece plane
  • Machining vector V along which the laser beam 6 and the workpiece 8 are moved relative to one another in the XY plane to form the desired cutting contour, i.e. there is a sharp observation.
  • the angle ⁇ at which the observation direction R1 is aligned with the beam axis 24 of the laser beam 6 is in the example shown between approximately 1 ° and approximately 5 °, for example approximately 4 °.
  • the diaphragm 28 can in particular be arranged in the focal plane of the lens 29 or the imaging optics 27 on the image side in order to produce a telecentric image.
  • an electrically adjustable diaphragm for example in the form of an LCD array, can be used, in which individual pixels or groups of pixels are electronically switched on or off to create the aperture effect.
  • the mechanical diaphragm 28 can also be moved or shifted transversely to the observation beam path 23, for example in the YZ plane, in a manner different from that shown in FIGS. 2a, b
  • the panel 28 can also be realized in the form of one or more mechanical elements that can be opened and closed. Unlike that shown in Fig. 2a, b, the aperture 28 can also be completely dispensed with, i.e. the observation beam path 23 as a whole is imaged on the detector surface 25a.
  • the machining head 4 In order to identify the workpiece 8 shown in FIG. 1 before machining, the machining head 4 and thus also the one permanently connected to it
  • Control tasks of the laser cutting machine 1 take over and, among other things, also control the motor drives of the movement device 13, positioned above the circular identification area 26 in the example shown.
  • Identification area 26 relative to the workpiece support 5 and thus also relative to the workpiece 8 positioned stationary on the workpiece support 5 is fixed.
  • the image B1 of the illuminated identification area 26 shown in FIG. 3a is generated on the detector surface 25a.
  • the machining head position PI is in the center of the nozzle opening 16a, which is the center of the circular
  • An evaluation device 31 shown in FIG. 2a which has a signal connection with the detector 25, is used to compare the recorded image B1 of the identification area 26 with a plurality of images BRi, BR2,..
  • Surface 8a of a plurality of workpieces 8 have been recorded and are stored in a storage device 33 shown in FIG. 1.
  • the storage device 33 can be formed, for example, in a central computer or in the cloud, which is connected to the evaluation device 31 in terms of signal technology. Other than this in Fig. 1 is shown, the storage device 33 can also in the
  • Evaluation device 31 can be integrated.
  • FIG. 3b two images BRi, BR2 of a respective reference area 32 are shown in FIG. 3b and in FIG. 4b, which were recorded on a first and second workpiece 8. Taking pictures BR1, BR2 of a respective one
  • Reference area 32 of a workpiece 8 can be created using the one shown in FIG.
  • a further sensor device 20 serves to record the image (s) BR1, BR2,... Of the respective reference area 32.
  • the further sensor device 20 can be provided on another processing machine on which a respective workpiece 8 is processed for the first time and an image BR1, BR2, ... of the respective reference area 32 is recorded to identify the workpiece 8.
  • An image BR1, BR2,... Of the respective reference area 32 can also be recorded on a sensor device 20 provided specifically for this purpose, on which none
  • Workpieces 8 are machined. Together with the laser cutting machine 1 shown in FIG. 1, the further sensor device 20 forms the
  • Evaluation device 31 and the storage device 33 a system 34 for
  • the images BR1, BR2 of the reference area 32 shown in FIG. 3b and in FIG. 4b were previously recorded on the surfaces 8a of a plurality of workpieces 8 at the same processing head position PI at which the image B1 of the identification area 26 was also recorded.
  • a respective reference area 32 is smaller than the identification area 26 and, due to the matching machining head position PI, the reference area 32 is arranged on the workpiece 8 concentrically with the identification area 26.
  • Identification area 26 is a reflection pattern RI specific to the workpiece 8 resting on the workpiece support 5, which is indicated symbolically in FIG. 3a by a plurality of lines and a dot.
  • the reflection pattern RI or the captured image B1 with the plurality of captured images BR1, BR2,... Of a respective one Reference region 32 compared, which were previously recorded on several workpieces 8, including on the workpiece 8 to be identified, which lies on the workpiece support 5.
  • a similarity measure A between the image B1 of the identification area 26 and the image BRi becomes one
  • Reference area 32 of a first workpiece 8 is determined.
  • the image BRi of the reference area 32 of the first workpiece 8 contains a workpiece-specific reflection pattern Ri, for which a measure of similarity A to the reflection pattern RI of the image B1 of the identification area 26 is determined.
  • the similarity measure A is determined by a pattern recognition algorithm, which compares the two images B1, BRi and thus the workpiece-specific reflection pattern RI of the identification area 26 with the workpiece-specific reflection pattern Ri of the reference area 32 of the first of the plurality of workpieces 8.
  • the similarity measure A can be, for example, a difference-based similarity function (Sum of Absolute Differences - SAD, median absolute deviation - MAD, Mean-squared-Difference - MSD), a cross-correlation
  • the reflection pattern Ri of the first workpiece 8 shown in FIG. 3b differs significantly from the reflection pattern RI of the workpiece 8 to be identified shown in FIG. 3a.
  • a value Ai of the similarity measure A is therefore determined which is very low.
  • the reflection pattern R2 of the image BR2 shown in FIG. 4b of the reference area 32 of the second of the plurality of images BRi, BR2,... Stored in the storage device 33 has one very high agreement with the reflection pattern RI of the identification area B1.
  • the value A2 of the similarity measure A is therefore larger than in the first image BRi shown in Fig. 3b, i.e. A2> Ai applies.
  • the identification of the workpiece 8 can possibly be completed, i.e. the workpiece 8 to be identified is the second stored image BR2 of the
  • Reference range 32 continued, which were recorded on a third, fourth, ... workpiece 8 and here a respective value A3, A4, ... for the
  • the workpiece 8 is assigned to that of the stored images BR1, BR2, ... of the reference area 32, in which the
  • Similarity measure A has a maximum value.
  • the value A2 of the similarity measure A is maximum in the second image BR2 shown in FIG. 4b, i.e. that on the workpiece support 5
  • Workpiece 8 lying on it is identified as the workpiece 8 on which the second image BR2 of the reference area 32 was recorded beforehand and in which
  • the images BR1 stored in the storage device 33 can , BR2, ... of the reference area 32 are deleted again.
  • the deletion can take place, for example, if the storage period of a respective reference image BR1, BR2, ... in the storage device 33 exceeds a predetermined period of time, if a respective associated workpiece 8 has left the system 34 and / or if a quality control on the respective workpiece 8 was carried out.
  • the example described here additionally checks whether the maximum value A2 of the similarity measure A determined in the comparison with all workpieces 8 is above a minimum or threshold value As.
  • the workpiece 8 is only identified if this is the case. If the threshold value As is undershot, this is an indication that the workpiece 8 does not match any of the plurality of workpieces 8 for the images BR1, BR2,... Of the reference area 32 in FIG.
  • Storage device 33 are stored.
  • the workpiece 8 can be misplaced due to In the event that the reflection pattern R2 'in the image BR2 of the reference area 32 is slightly rotated relative to the reflection pattern RI in the image B1 of the identification area 26, as can be seen from a comparison of FIG. 5a with FIG. 5b: Although the reflection pattern R2 of the image BR2 of the
  • Reference area 32 of FIG. 5b is practically identical to the reflection pattern RI of the identification area 26 of FIG. 5a, in the event that the rotation is not taken into account, no high value A2 is determined for the similarity measure A, so that it may become one
  • the workpiece 8 is incorrectly assigned or not identified because the threshold value A s is not exceeded.
  • Pattern recognition algorithm can be used, e.g. Optical flow.
  • Identification area 26 and reference area 32 which means that both areas 26, 32 are not arranged concentrically, can be compared when comparing the respective images B1, BR2 by means of a suitable pattern recognition algorithm which is tolerant of a relative shift, for example by means of a cross-correlation algorithm , are taken into account.
  • the fact that the reference area 32 is smaller than the identification area 26 and is completely surrounded by it has a favorable effect here. In the lateral displacement shown in FIG. 5 a, the reference area 32 is still completely within the identification area 26, so that the entire reference area 32 for the
  • Angular positions can, if necessary, be a value for the for a plurality of values of the lateral offset between the reference area 32 and the identification area 26 Similarity measure A is determined and a maximum value for similarity measure A is determined with different lateral misalignments.
  • Sensor devices 20 are included, these can optionally be included
  • the different magnifications of the images BR1, BR2 or B1 can be taken into account during the comparison by scaling them appropriately for the comparison, so that the difference in the imaging scales is compensated for.
  • the images BR1, BR2,... Of the respective reference area 32 and the image B1 of the identification area 26 should, if possible, be compared with something comparable
  • the illuminating power PB of the illuminating source 21 can be suitably set, for example taking into account the reflectivity of a respective material type of the workpiece 8.
  • the method or system 34 for identifying workpieces 8 has been described in connection with a laser cutting machine 1, this method can also be used in other machining processes, for example in the welding machining of a workpiece 8 with the aid of a machine tool 1 designed for this purpose, e.g. in the form of a laser welding machine, a processing machine for the forming processing of the workpiece 8 etc.

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Abstract

La présente invention concerne un procédé pour identifier une pièce à usiner (8) de préférence sous forme d'une plaque, en particulier une tôle. Le procédé comprend : l'exposition d'une zone d'identification (26) sur une surface (8a) de la pièce à usiner (8) avec un rayonnement d'exposition, la photographie d'une image de la zone d'identification (26) qui contient un modèle de réflexion, spécifique à la pièce à usiner, du rayonnement d'exposition réfléchi au niveau de la zone d'identification (26), ainsi que l'identification de la pièce à usiner (8) par une comparaison de l'image photographiée de la zone d'identification (26) avec au moins une image d'une pluralité d'images, stockées dans un dispositif de stockage (33), d'une zone de référence (32) recouvrant au moins en partie la zone d'identification (26), qui contiennent chacune un modèle de réflexion, spécifique à la pièce à usiner, et qui ont été photographiées à la surface (8a) d'une pluralité de pièces à usiner (8). La présente invention concerne en outre un système (34) d'identification d'une pièce à usiner (8).
PCT/EP2019/077777 2018-10-15 2019-10-14 Procédé et système d'identification d'une pièce à usiner Ceased WO2020078902A1 (fr)

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