INSTALLATION AND METHOD FOR NON-DESTRUCTIVE INSPECTION OF WELD POINTS

Abstract

Installation and method for the non-destructive inspection of welding points comprising a robot arm carrying in its hand an inspection head (9), provided with a surface analysis device (15), an ultrasonic probe (17) and a dispensing device (19) of a coupling substance. Figure to be published with the abstract: Figure 2

Description

Title of the invention: INSTALLATION AND METHOD FOR THE NON-DESTRUCTIVE INSPECTION OF WELDING POINTS

[0001] The invention lies in the field of non-destructive testing techniques for the inspection and quality control of welding points used for the assembly of automobile bodies.

[0002] It is known to construct structures such as vehicle bodies by assembling different metal parts, such as steel sheets, using electric resistance welding spots. Motor vehicle bodies are thus assembled more than 80% by welded spots. To do this, at least two metal parts are held together by means of a clamp providing point pressure, and heated by passing an electric current until the material melts at the contact zone. This technique is therefore dependent on the resistivity of the materials, the thickness of the assembly and the diameter of the electrodes forming the clamp. This method, which is very reliable, lends itself to partial or total automation.

[0003] However, it has been found that due to the automation of welding, some welding points may not comply with the required quality standards. Among the defects listed, we note the absence of a welding point or the absence of welding as such (the metal parts are glued together but not welded). When a welding point is present, it may be undersized, intersecting, poorly positioned, burned, or deformed. It is also possible for a welding point to show a burr or an excessive imprint. All these defects are obviously detrimental to the quality of the vehicle produced, in particular because they can affect its proper functioning or its robustness, and therefore impact the safety of the passengers transported. It is therefore important, during the production of a vehicle, to be able to detect these defects and remedy them.

[0004] A first known way to check the conformity of the welding points with respect to the required requirements is a visual inspection by experienced operators. However, this solution is insufficient, costly in time and labor. There is therefore a need to automate the quality control process.

[0005] Various automated technologies for non-destructive testing of resistance welding points have been described.

[0006] Thus, document KR20070044647A describes a system for non-destructive analysis of resistance welding points comprising a sensor coupled to an analyzer allowing automated interpretation of results. In the technology used, the sensor uses an electrical resistance measurement at the welding points.

[0007] Document US2021379689A1 describes a resistance welding device coupled to a control device. The control device comprises an imaging system coupled to an ultrasonic detector and to a coupling gel deposition apparatus allowing good transmission of ultrasound in the analyzed area. The coupling of the two devices, welding and control, allows the adjustment of the welding parameters on the basis of the results obtained during the inspection of the previous welding points in a fully automated manner. Although very interesting, this solution is nevertheless incomplete because the ultrasonic detector only allows a partial vision of the area of interest to be obtained.

[0008] Document EP3492214A1 refers to an automated inspection system for weld points, comprising a robot, a controller, a camera and an eddy current probe. This solution is also interesting but also has the disadvantage of only allowing a partial view of the area of interest to be obtained.

[0009] Document WO2016172078A1 describes a portable inspection system for weld points, which can be mounted on a robot and uses a multi-element ultrasonic detector, the latter using a fluid applicator on the surface of the object to be inspected to improve detection; an associated controller makes it possible to validate or invalidate the weld points in an automated manner following acceptability instructions. The points to be inspected are predetermined prior to the examination.

[0010] Document JP2006104672 presents an automated inspection system based on an industrial robot. A machine vision system is used to identify the precise location of the weld point. The robot then places the probe in the center of the weld and optimizes the orientation to obtain the best signal, which is recorded and analyzed. The device uses a conventional ultrasonic inspection system, without gel application.

[0011] The invention aims to overcome at least one of the defects and drawbacks encountered in the prior art. The invention aims to provide an installation and a method for the non-destructive inspection of welding points allowing a complete and reliable control of said welding points in an automated manner. In particular, the invention aims to provide an installation and a method for the non-destructive inspection of welding points allowing an automated inspection of said welding points both on criteria of appearance and quality of the fixing obtained by welding, said inspection showing increased reliability and precision.

[0012] To this end and according to a first aspect, the invention relates to an installation for non-destructive inspection of weld points, the installation comprising a robot arm carrying in its hand an inspection head, the installation being remarkable in that the inspection head comprises a surface analysis device, an ultrasonic probe and a device for dispensing a coupling substance.

[0013] As will be understood from reading the definition which has just been given, the invention consists of coupling on the same inspection head, two welding point inspection devices, not only complementary in their functions and in the information collected but which cooperate to allow complete automation of the inspection process.

[0014] The use of a coupling substance makes it possible to improve the reliability and precision of an ultrasonic analysis. Indeed, when an ultrasonic analysis is carried out without the application of a coupling substance, only a partial view of the weld point analyzed is obtained, and moreover the absence of a coupling substance results in a significant attenuation of the signal between the emission and reception of the ultrasound by the probe.

[0015] According to preferred embodiments, the surface analysis device comprises a camera and / or a laser profilometer device; preferably, the camera is a stereoscopic camera allowing the restitution of a relief image.

[0016] According to preferred embodiments, the ultrasound probe is a multi-element ultrasound probe; preferably, the multi-element ultrasound probe is a linear or matrix array probe.

[0017] Advantageously, the surface analysis device is arranged to be interposed between the ultrasound probe and the device for dispensing a coupling substance; and / or the ultrasound probe is arranged to be oriented at an angle of between 10 and 80° relative to the orientation of the surface analysis device.

[0018] Ideally, the installation further comprises a reservoir configured to supply the dispensing device with coupling substance; preferably, the reservoir is carried by the inspection head.

[0019] Preferably, the robot has a poly-articulated arm with 5, 6 or 7 axes; and / or the installation further comprises a unit for processing the data obtained by the inspection head during an inspection cycle.

[0020] According to a second aspect, the invention relates to an inspection method for the non-destructive inspection of welding points implementing an installation according to the first aspect, the method carrying out an inspection cycle per welding point and is remarkable in that at least one inspection cycle or each inspection cycle comprises the following steps:

[0021] c) acquisition of at least one image and / or profile data of the welding point by means of a surface analysis device and analysis of the conformity of said point welding according to a first series of parameters;

[0022] d) applying a coupling substance to the welding point by the dispensing device

[0023] e) acquisition of sound information from an ultrasonic probe and analysis of the conformity of said welding point according to a second series of parameters.

[0024] It will be understood that the inspection of said welding points by the surface analysis device is carried out on appearance criteria (shape, relief, etc.) while the ultrasonic analysis offers an inspection more focused on the quality of the fixing obtained between the elements welded together.

[0025] According to preferred implementations, step c) is carried out so as to enable the creation of a three-dimensional profile of said welding point, and comprises the acquisition of a pair of stereoscopic images and / or the acquisition of profile data.

[0026] According to preferred implementations, step e) comprises rotating the inspection head to align the ultrasonic probe with the weld point to be inspected.

[0027] Advantageously, prior to the implementation of an inspection cycle, a test is carried out to determine whether the dispensing device and its reservoir contain a predetermined volume of coupling substance to be deposited, the inspection cycle being initiated when the result of the test is positive.

[0028] Preferably, prior to step c) at least one inspection cycle or each inspection cycle comprises the following steps:

[0029] a) Positioning the inspection head at the theoretical position of a weld point to be inspected; and

[0030] b) Activation of the surface analysis device and possible correction of the position of the inspection head relative to said welding point.

[0031] The use of a surface analysis device makes it possible, in addition to an inspection based on visual and / or relief criteria, to determine the exact location of the welding point and therefore to precisely apply a coupling substance for ultrasonic analysis. The volume of coupling substance deposited is therefore optimized.

[0032] According to one implementation, the first series of parameters comprises the measurement or determination of one or more parameters chosen from the shape of the welding point, its diameter and / or its depth; and in that the method comprises the comparison of the observed shape with a predetermined shape and / or the measured values with predetermined reference value ranges; the welding point being declared non-compliant when at least one of the measurements is outside said reference ranges.

[0033] According to one implementation, the second series of parameters comprises one or more parameters chosen from the junction depth between the sheets, the surface of junction at a given depth, and the size of a defect if a defect is present; and in that the method comprises comparing the measured values to predetermined reference value ranges; the weld point being declared non-compliant when at least one of the measurements is outside said reference ranges.

[0034] The invention will be well understood and other aspects and advantages will appear clearly on reading the following description, given by way of example with reference to the attached drawings in which:

[0035] [Fig.l] represents an installation according to the invention.

[0036] [Fig.2] represents an inspection head according to the invention.

[0037] In the following description, the term "comprise" is synonymous with "include" and is not limiting in that it allows the presence of other elements in the installation or process to which it relates. It is understood that the term "comprise" includes the terms "consist of". In the different figures, the same references designate identical or similar elements.

[0038] The invention relates to an installation for the non-destructive inspection of welding points and the method used to carry out said inspection. The installation and the method will be described jointly. The invention is particularly suitable for the inspection of welding points present on the body or on a body subassembly of a motor vehicle but will be easily applied to the inspection of welding on other assemblies of parts welded together. Similarly, the invention will be described in application with electric welding points but can be used for the inspection of the quality of laser welding points and / or welding beads.

[0039] Reference will first be made to [Fig. 1] illustrating an exemplary embodiment of an installation 1 according to the invention. The installation 1 comprises a positioning table 3 intended to receive a body 5 or a vehicle body subassembly for the purpose of its inspection. A body subassembly may be a platform, body sides, a front or rear assembly, etc. The different subassemblies are then assembled to form the body of a vehicle.

[0040] The installation 1 also comprises a robot 7 having a poly-articulated arm holding an inspection head 9 in its hand. The poly-articulated arm is of the 5, 6 or 7 axis type so as to show sufficient flexibility to be able to align the inspection head 9 with all the welding points to be inspected on the body 5 or a sub-assembly of the body of the vehicle. Preferably, the robot 7 has a 6-axis poly-articulated arm. The invention further comprises a unit 11 for processing the data obtained by the inspection head 9 during an inspection cycle. The unit 11 comprises one or more computers equipped with software for analyzing the images obtained by the surface analysis device 15 and the sound information obtained by the ultrasound probe 17.

[0041] An exemplary embodiment of an inspection head 9 is illustrated in [Fig. 2]. The inspection head 9 comprises a plate 13 for its attachment to the robot arm (not visible in [Fig. 2]). It comprises a surface analysis device 15, an ultrasonic probe 17 and a device 19 for dispensing a coupling substance. According to a preferred embodiment, the surface analysis device 15 is arranged to be interposed between the ultrasonic probe 17 and the device 19 for dispensing a coupling substance. The arrangement can be in the vertical direction as illustrated in [Fig. 2] or in the horizontal direction. When it is in the vertical direction, the person skilled in the art will benefit from the nozzle of the device 19 for dispensing the coupling substance being arranged lower than the surface analysis device 15.

[0042] Advantageously, the surface analysis device 15 and the ultrasonic probe 17 are oriented at different angles so that they can be used alternately after rotation of the inspection head 9. Advantageously, the ultrasonic probe 17 is oriented at an angle less than or equal to 90° relative to the orientation of the surface analysis device 15; for example an angle between 10 and 90°; or an angle between 20 and 80°; or an angle between 25 and 70°; or between 30 and 60°.

[0043] The surface analysis device 15 has a dual function. Firstly, after positioning the inspection head 9 at the theoretical position of a weld point to be inspected, the surface analysis device 15 will make it possible to confirm said theoretical coordinates of the weld point to be inspected by comparing them with the actual coordinates. When the actual coordinates differ from the theoretical coordinates, the method comprises a step of correcting the position of the inspection head 9 relative to the weld point to be inspected.

[0044] Once the surface analysis device 15 is aligned with the weld point, an acquisition of one or more images of the weld point and / or profile data is carried out.

[0045] In an exemplary embodiment, the surface analysis device 15 is, or comprises, a camera; preferably a stereoscopic camera allowing the restitution of a relief image (i.e. a three-dimensional profile). In the latter case, the method comprises the acquisition of at least two images from different angles so as to be able to obtain a relief image of said welding point. The images can be acquired successively with a modification of the angle and / or the positioning of the camera between two acquisitions. According to a preferred embodiment, the camera is a stereoscopic camera (or “3D camera” or even “3-dimensional camera”) which allows a double image acquisition to be carried out simultaneously according to two different angles or positions. Such cameras are known and com generally take two lenses, placed side by side in a single housing. The camera will simultaneously acquire a pair of stereoscopic images, i.e. two twin (but not similar) images for the purpose of restoring the relief (i.e. for a three-dimensional inspection).

[0046] In one exemplary embodiment, the surface analysis device 15 is, or comprises, a laser profilometer device. Laser profilometer devices are known to those skilled in the art, and use a laser beam to scan the surface of an object. By measuring the time it takes for the laser to return after hitting the surface, the device can calculate the distance and create a three-dimensional profile of the object.

[0047] The surface inspection carried out (on visual and / or profilometric criteria) thus makes it possible to carry out an inspection of the conformity of the welding point by measuring one or more parameters of a first series and comparing the measured values with predetermined reference value ranges. The welding point is declared non-compliant when at least one of the measurements is outside said reference ranges.

[0048] When the surface analysis device 15 is, or comprises, a simple camera, it allows an inspection on visual criteria in two dimensions, the first series of parameters comprises at least the shape of the welding point and / or its diameter.

[0049] When the surface analysis device 15 is, or comprises, a laser profilometer device, it allows an inspection of the three-dimensional profile of the welding point, the first series of parameters consists of, or comprises, one or more parameters chosen from the shape of the welding point, its diameter and / or its depth.

[0050] The invention is remarkable in that the inspection of the welding points is carried out according to at least two different analysis methods. Thus, once the surface inspection has been carried out (on visual and / or profilometric criteria), the method and the installation 1 will allow a second inspection of the welding point by ultrasonic technology.

[0051] Thus, as seen above, the inspection head 9 is also provided with an ultrasonic probe 17 and a device 19 for dispensing a coupling substance.

[0052] Thus, the method according to the invention comprises placing a predetermined volume of a coupling substance on the welding point for the purpose of non-destructive inspection of said point by ultrasound.

[0053] The fully automated application of the coupling substance is made possible by determining the actual coordinates of the welding point during the previous steps. Advantageously, the applied coupling substance is water-soluble and / or anti-corrosive. Its viscosity is sufficient to prevent it from flowing after application.

[0054] The coupling substance is supplied to the dispensing device 19 from a reservoir 21. Preferably, said reservoir 21 is fixed to the inspection head 9. Advantageously, before any start of an inspection cycle, the method comprises a test aimed at determining whether the dispensing device 19 and its reservoir 21 contain said predetermined volume of coupling substance to be deposited. If the result of the test is positive, the inspection cycle is started. Otherwise, an alert is sent to signal to an operator that the reservoir 21 must be filled in order to be able to carry out an inspection cycle. The reservoir 21 can be detachable from the inspection head 9 for filling or can be filled in situ.

[0055] The coupling substance deposited is preferably a coupling gel. The use of the ultrasound coupling gel guarantees high precision and good reproducibility in defect detection measurements. Coupling gels are commercially available, for example, from PCE Instruments France or Olympus.

[0056] The inspection head 9 then rotates in order to align an ultrasonic probe 17 with the weld point to be inspected.

[0057] Ultrasonic spot welding inspection techniques are well known to those skilled in the art. The technique used in the context of the invention uses a monolithic ultrasonic probe or a phased array ultrasonic probe, preferably a multi-element ultrasonic probe. Phased array ultrasonic probes (PA for "Phase Array") allow the implementation of advanced ultrasonic testing methods in the context of industrial non-destructive testing. Thus, the invention will preferentially use ultrasonic technology of the PAUT type (for "Phase Array Ultrasonic Technology"). This technology is well known and for example described in document WO2016172078A1.

[0058] Single-element (non-phased array) probes, technically known as monolithic probes, emit a beam in a fixed direction. When such a probe is used, it is physically scanned (moved or rotated) to sweep the beam across the area of interest.

[0059] Preferably, a person skilled in the art will use a phased array ultrasound probe whose beam can be focused and scanned electronically without moving the probe. The beam is controllable because a phased array ultrasound probe is composed of several small elements, each of which can be pulsed individually at a computer-calculated time. Phased array ultrasound probes are known and commercially available, for example, from Olympus.

[0060] The multi-element ultrasonic probe may be selected from ring array probes, circular array probes, convex array probes, concave array probes, linear array probes, matrix array probes, sector array probes, and sparse array probes. According to a preferred implementation of the invention, the multi-element ultrasonic probe 17 is a linear or matrix array probe; more preferably a matrix array probe.

[0061] The method thus comprises the acquisition of sound information from an ultrasonic probe 17; preferably, from a multi-element ultrasonic probe; and analysis of the conformity of said welding point according to a second series of parameters and comparison of the measured values with predetermined reference value ranges. The welding point being declared non-compliant when at least one of the measurements is outside said reference ranges.

[0062] According to the invention, the second series of parameters comprises one or more parameters chosen from the junction depth between the sheets, the junction surface at a given depth, and the size of a defect if a defect is present.

[0063] The results of the visual and ultrasonic determination inspection tests are recorded for transmission to an operator or to an automated or semi-automated weld defect correction system.

[0064] Thus, the invention also relates to an inspection method for the non-destructive inspection of weld points using an installation 1 as described above; the method carrying out one inspection cycle per weld point and is remarkable in that at least one inspection cycle or each inspection cycle comprises the following steps:

[0065] c) acquisition of at least one image and / or profile data of the welding point by means of a surface analysis device 15 and analysis of the conformity of said welding point according to a first series of parameters;

[0066] d) application of a coupling substance to the welding point by the dispensing device 19;

[0067] e) acquisition of sound information from an ultrasonic probe 17 and analysis of the conformity of said welding point according to a second series of parameters.

[0068] According to a preferred implementation, at least one inspection cycle or each inspection cycle comprises the following steps:

[0069] a) positioning of the inspection head 9 at the theoretical position of a welding point to be inspected;

[0070] b) activation of the surface analysis device 15 and possible correction of the position of the inspection head 9 relative to said welding point;

[0071] c) acquisition of at least one image and / or profile data of the welding point by means of a surface analysis device 15 and analysis of the conformity of said welding point according to a first series of parameters;

[0072] d) applying a coupling substance to the welding point by the dispensing device 19;

[0073] e) acquisition of sound information from an ultrasonic probe 17 and analysis of the conformity of said welding point according to a second series of parameters.

Claims

Claims

1. Installation (1) for the non-destructive inspection of weld points, the installation (1) comprising a robot arm carrying in its hand an inspection head (9), the installation (1) being characterized in that the inspection head (9) comprises a surface analysis device (15), an ultrasonic probe (17) and a dispensing device (19) for a coupling substance.

2. Installation (1) according to claim 1, characterized in that the surface analysis device (15) comprises a camera and / or a laser profilometer device; and / or in that the ultrasonic probe (17) is a multi-element ultrasonic probe; preferably, the multi-element ultrasonic probe is a linear or matrix array probe.

3. Installation (1) according to one of claims 1 or 2, characterized in that the surface analysis device (15) is arranged to be interposed between the ultrasonic probe (17) and the device (19) for dispensing a coupling substance; and / or in that the ultrasonic probe (17) is arranged to be oriented at an angle of between 10 and 90° relative to the orientation of the surface analysis device (15).

4. Installation (1) according to claim 1 to 3, characterized in that it further comprises a reservoir (21) configured to supply the distribution device (19) with coupling substance; preferably, the reservoir (21) is carried by the inspection head (9).

5. Installation according to one of claims 1 to 4, characterized in that the robot (7) has a poly-articulated arm with 5, 6 or 7 axes; and / or in that it further comprises a unit (11) for processing the data obtained by the inspection head (9) during an inspection cycle.

6. Inspection method for the non-destructive inspection of welding points using an installation (1) according to one of claims 1 to 5; the method performing one inspection cycle per welding point and is characterized in that at least one inspection cycle or each inspection cycle comprises the following steps: • c) acquisition of at least one image and / or profile data of the welding point by means of a surface analysis device (15) and analysis of the conformity of said welding point according to a first series of parameters; • d) application of a coupling substance to the welding point by the dispensing device (19); • e) acquisition of sound information from an ultrasonic probe (17) and analysis of the conformity of said welding point according to a second series of parameters.

7. Method according to claim 6 characterized in that step c) is carried out so as to allow the creation of a three-dimensional profile of said welding point and comprises the acquisition of a pair of stereoscopic images and / or the acquisition of profile data; and / or in that step e) comprises the rotation of the inspection head (9) to align the ultrasonic probe (17) with the welding point to be inspected.

8. Method according to one of claims 6 or 7, characterized in that prior to the implementation of an inspection cycle, a test is carried out to determine whether the dispensing device (19) and its reservoir (21) contain a predetermined volume of coupling substance to be deposited, the inspection cycle being initiated when the result of the test is positive; and / or in that prior to step c) at least one inspection cycle or each inspection cycle comprises the following steps: • a) positioning of the inspection head (9) at the theoretical position of a welding point to be inspected; and • b) activation of the surface analysis device (15) and possible correction of the position of the inspection head (9) relative to said welding point.

9. Method according to one of claims 6 to 8, characterized in that the first series of parameters comprises the measurement or determination of one or more parameters chosen from the shape of the welding point, its diameter and / or its depth; and in that the method comprises the comparison of the observed shape with a predetermined shape and / or the measured values with predetermined reference value ranges; the welding point being declared non-compliant when at least one of the measurements is outside said reference ranges.

10. Method according to one of claims 6 to 9, characterized in that the second series of parameters comprises one or more parameters chosen from the junction depth between the sheets, the surface of junction at a given depth, and the size of a defect if a defect is present; and in that the method comprises comparing the measured values to predetermined reference value ranges; the weld point being declared non-compliant when at least one of the measurements is outside said reference ranges.

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