METHOD FOR MANUFACTURING AND TESTING A FINISHED BREAK LINE IN A VEHICLE INTERIOR TRIM PART

Description

[0001] The invention relates to a method for producing a predetermined breaking line in a vehicle interior trim part and for checking its contour and position.

[0002] The process is carried out with a device that includes a sensor matrix and a laser scanning device, with which, during the production of the predetermined breaking line, a laser beam scanning across the vehicle interior trim part along the predetermined breaking line removes material until individual sensors of the sensor matrix detect a portion of the laser beam transmitting through the vehicle interior trim part.

[0003] It should be noted that, for the purposes of this description, a predetermined breaking line is defined as a line along which the predetermined breaking line is created, regardless of the processing state.

[0004] The creation of predetermined breaking lines using lasers in vehicle interior trim parts, e.g., for airbag openings in the dashboard, door panels, or steering wheel hub, or as break points on components protruding into the passenger compartment, such as cup holders, has been known for a long time. Due to the high demands on both the reliable breaking of these lines when needed and the aesthetic appearance of the trim parts, where a vehicle occupant should not perceive the predetermined breaking points with the naked eye, material removal along a predetermined breaking line that defines the breaking point is sensor-monitored or sensor-controlled.

[0005] It is also known in other applications, e.g. in the packaging industry, to introduce predetermined breaking lines using lasers as a separating aid in containers etc.

[0006] To create a predetermined breaking point by laser material removal, slits or holes, or so-called microperforations, which only penetrate the vehicle's interior trim panel with a very small opening, are made along a predefined line in the relevant vehicle interior trim panel. Sensor monitoring and control allow for the creation of either a reproducible remaining wall thickness or small holes with a reproducible diameter along the line forming the predetermined breaking point. This is achieved by using the detection of radiation energy transmitted through the remaining wall or the hole as a control parameter, specifically when a predefined threshold is exceeded.For this purpose, at least one sensor is arranged on the side of the vehicle interior trim panel opposite the laser (visible side). During processing, this sensor detects a transmitting portion of the processing laser radiation when the vehicle interior trim panel within the predetermined breaking line at the respective processing point has only a certain residual wall thickness or already a micro-hole. The necessary relative movement for generating predetermined breaking lines can, in principle, be generated by the laser beam as a tool or by the vehicle interior trim panel itself, with the tool stationary. A method involving movement of the laser beam has proven to be simpler to implement. In comparison to robot-controlled guidance of a laser source above and along the predetermined breaking line, a two- or...Three-dimensional scanning of a laser beam along the predetermined breaking line is technically easy to implement and also allows for significantly faster processing.

[0007] DE 10 2005 026 906 A1 discloses an interior trim part for vehicles and a method for manufacturing such an interior trim part. A device for carrying out the method comprises a laser with focusing optics and a scanner mirror system. A focus of a laser beam generated by the laser lies at a depth within the interior trim part, and material is removed at this focus.

[0008] From DE 10 2005 054 607 A1 a method for determining a residual layer thickness during the formation of blind holes or cut edges in components is known, in which blind holes or cut edges are formed by means of laser radiation starting from one side of a component and the temperature on the opposite surface of the component is determined without contact by means of electromagnetic radiation emitted from this surface and thus the residual layer thickness in the respective processing area of ​​the laser radiation is determined.

[0009] A method disclosed in patent EP 1 118 421 B1 describes the production of a predetermined breaking line consisting of perforations using pulsed or continuous laser radiation. The laser beam is directed onto the back of a vehicle interior trim panel by means of a processing optic. Opposite, on the front of the vehicle interior trim panel, a sensor is located in the laser's beam path, i.e., on the optical axis of the processing optic. During a relative movement between the vehicle interior trim panel and the processing optic along the predetermined breaking line to be produced, the laser emits a limited sequence of individual pulses, which partially overlap on the vehicle interior trim panel, or a continuous laser beam of limited duration. This creates a slot in the vehicle interior trim panel with a continuously decreasing residual wall thickness.The laser radiation is interrupted as soon as the sensor on the front detects a breakthrough of the laser beam. If the required relative movement is to be performed by the laser, highly precise tracking of the sensor must be achieved so that the sensor axis and the optical axis of the processing optics always coincide.

[0010] According to EP 0 827 802 B1, a defined material removal down to a remaining residual wall thickness (material thickness) is ensured by detecting the transmitted radiation at the processing point from the outside using a sensor. For this purpose, the sensor must be positioned on the optical axis of the laser beam directed at the vehicle interior trim panel. No details are provided here regarding how the relative movement between the laser beam and the vehicle interior trim panel necessary to generate the predetermined breaking line is achieved.

[0011] EP 3 321 024 A1 discloses a method and a device for producing a weakening line in a planar workpiece along a predetermined contour by material removal using a laser. In this method, a workpiece is positioned in a working area between an array of sensors and a laser scanner. The laser scanner scans a pulsed laser beam across the back side of the planar workpiece along a weakening line, removing material in the form of holes down to a predetermined residual wall thickness at a multitude of ablation points along the weakening line. During material removal, individual sensors detect measurement signals generated by the laser beam's transmission at the ablation points. Subsequently, a comparison signal is generated and compared with a reference signal to which the predetermined residual wall thickness is assigned.The laser generator that produces the laser pulses is controlled so that laser pulses only strike the ablation sites until the predetermined residual wall thickness is reached. The transmitted laser radiation power of a laser pulse is then detected when it exceeds a lower limit of the sensor's sensitivity range, and the attenuation line can be positioned arbitrarily within the sensor array's field of view.

[0012] German patent application DE 10 2007 024 510 B3 discloses a device with a sensor arranged on the outside of the vehicle interior trim panel to be processed, the sensor's measuring range encompassing the entire predetermined breaking line. The sensor is a matrix camera whose pixels can be read individually. An associated control and processing unit is connected to the sensor and a laser generator, which generates the processing laser radiation. The control and processing unit is designed to store the positional data of the matrix camera's pixels, assigned to the individual processing locations, so that during processing only the pixels assigned to the relevant processing location are read out.

[0013] Accordingly, the vehicle interior trim part must be positioned with precise alignment to the sensor so that the individual processing locations along the predetermined breaking line assume a predetermined relative position to the respective assigned pixels.

[0014] According to the method described in the aforementioned DE 10 2007 024 510 B3, a predetermined breaking line is produced in a vehicle interior trim panel by directing a laser beam onto the inner surface of a vehicle interior trim panel held stationary in a holding device, guiding it along a predetermined breaking line, and causing material removal in the form of holes with a remaining wall thickness at a multitude of processing points along the predetermined breaking line. Predetermined pixels of a stationary sensor, which detects the complete course of the predetermined breaking line on the outer surface of the vehicle interior trim panel, acquire measurement values ​​that are equivalent to the remaining wall thickness. Depending on these measurement values, a laser generator emitting the laser beam is controlled by comparison with at least one reference measurement value.Essential to the method disclosed in the aforementioned DE 10 2007 024 510 B3 is that only predetermined pixels of a matrix camera are read out to determine the measured values. These predetermined pixels are the pixels that are stored as receiving pixels assigned to the individual processing locations.

[0015] In contrast to the methods described above, a method according to EP 10 2021 115 496 does not require the vehicle interior trim part to be precisely positioned opposite a sensor array. Here, the vehicle interior trim part is positioned in a working plane between a sensor matrix and a laser scanning device, and a laser beam is scanned along the predetermined breaking line. This process removes material in the form of holes down to a predetermined remaining wall thickness at each processing location along the breaking line. A transmitting portion of the laser beam sequentially generates individual measurements for individual sensors of the sensor matrix at each of the processing locations. A total measurement is calculated from the simultaneously acquired individual measurements and compared to a total reference value, to which the predetermined remaining wall thickness is assigned.When the total measured value reaches the total reference value, the laser beam is switched off. A special feature of the method disclosed here is that, at the beginning of the method, the actual position of the vehicle interior trim part in a coordinate system relative to the laser scanner is determined using a camera whose relative position in the coordinate system is known, in order to adjust the stored coordinates for the predetermined breaking line to the actual position of the vehicle interior trim part. The remaining wall thickness along the predetermined breaking line can only be inferred from the measured values ​​of the sensor matrix.

[0016] The object of the invention is to find a method in which the remaining wall thickness in a predetermined breaking line is monitored by means of a sensor matrix and the contour and position of the predetermined breaking line on the vehicle interior trim part can be checked without additional detection means.

[0017] This problem is solved by a method having the features of claim 1.

[0018] Advantageously, the stored individual measurements are not only compared with the individual reference values, but also with individual comparison values ​​that are stored and assigned to the respective individual sensor and processing location, each of which represents a positional deviation from the target position. Through interpolation, the actual position can thus be deduced from the individual measurements.

[0019] In order to determine the contour and position of the predetermined breaking line with minimal computational effort, it is advantageous to store and compare the individual measurement value for each processing location only for those individual sensors that have a center distance to the target position of the processing location that is smaller than the maximum extent of an individual sensor.

[0020] Alternatively, advantageously, the individual measurement value is stored and compared for each processing location for exactly the two individual sensors for which the highest individual reference value is recorded, in comparison to the other individual reference values ​​assigned to the processing location.

[0021] It is advantageous that a defective individual sensor can be identified if at least one of the read-out individual sensors does not provide an individual measurement value or provides an individual measurement value that deviates by more than 50% from the associated individual reference value.

[0022] Advantageously, a negative deviation of an individual measurement value from the assigned individual reference value can indicate a positional deviation of the actual position of the machining location from its target position away from the center of the relevant individual sensor, and a positive deviation of an individual measurement value from the assigned individual reference value can indicate a positional deviation of the actual position of the machining location from its target position towards the center of the relevant individual sensor.

[0023] It is not necessary to determine the actual position for each processing location using the inventive process steps; instead, the actual position of individual processing locations can be determined from the determined actual positions of neighboring processing locations.

[0024] More accurate results are achieved when simultaneously recorded individual measurements are weighted differently in the overall measurement value, depending on the different sensitivities and / or response times of the individual sensors.

[0025] To determine whether a vehicle interior trim part is a good part, it is advantageous to define an upper limit for the number of positional deviations outside a tolerance range and to confirm the vehicle interior trim part as a good part if the upper limit is not exceeded.

[0026] For later verification purposes, it is advantageous to document the actual positions of the processing locations and assign them to the target positions. Such documentation can also take the form of a two-dimensional map on which the processing locations are locally entered and where, for example, individual reference values ​​and individual measurements are marked, or where the magnitude of the individual measurements is locally reflected by corresponding color intensity.

[0027] The invention is explained in more detail below using exemplary embodiments and the accompanying drawings. These drawings show:

[0028] In Fig. 1 Figure 1 is a schematic representation of a device known from the prior art and suitable for carrying out the method for producing a predetermined breaking line 2 in a vehicle interior trim panel 1. It comprises a sensor matrix 3, a processing head arranged for this purpose with a laser generator and a laser scanning device 4, and an intermediate working plane A in which the vehicle interior trim panel 1 to be processed is arranged in a defined position relative to the sensor matrix 3 and the laser scanning device 4. The device also includes a control and processing unit that is connected to the sensor matrix 3 and the laser scanning device via a signal connection. The working plane A is adapted to the surface contour of the vehicle interior trim panel 1 and need not be a geometric plane.The defined arrangement of the sensor matrix makes it known which individual sensors detect transmitting laser radiation during the production of each hole in the predetermined breaking line, provided the breaking line is produced with a predetermined contour in a predetermined position. Individual reference values ​​are stored for each of the respective sensors, corresponding to the predetermined position of the individual holes.

[0029] The process begins with the vehicle interior trim part 1 to be processed being positioned in the working plane A between the sensor matrix 3 and the laser scanning device 4 in a predetermined relative position to the sensor matrix 3. Consequently, a predetermined breaking line 2 to be generated and the holes forming it also assume a predetermined relative position to the laser scanning device 4 and to the sensor matrix 3, and thus to the individual sensors of the sensor matrix 3.

[0030] The laser scanning device 4 scans a laser beam S on an inside surface of the vehicle interior trim part 1, along the predetermined breaking line 2, whereby material removal in the form of holes is effected up to a predetermined residual wall thickness at each processing location P along the predetermined breaking line 2.

[0031] A portion of the laser beam S, transmitted sequentially to the processing locations P, causes individual measurements at individual sensors of the sensor matrix, at least some of which are recorded. Typically, only those individual measurements above a threshold are recorded. Alternatively, individual measurements from selected sensors at and around the respective processing location P can be recorded. The more individual measurements are included in the overall measurement, the more independent the overall measurement becomes from the point of impact of the laser beam (processing location).

[0032] From simultaneously acquired individual measurements, an overall measurement value is calculated for each processing location P and compared with a stored overall reference value, to which the specified remaining wall thickness is assigned. The laser beam S is switched off when the overall measurement value reaches the overall reference value.

[0033] It is essential to the invention that at least some of the individual measured values ​​of a respective total measured value, upon reaching the total reference value, are stored and assigned to the relevant individual sensor and the relevant processing location, and are each compared with a stored individual reference value assigned to the relevant individual sensor and the relevant processing location, and that the resulting deviations are used to evaluate the contour and the position of the predetermined breaking line 2.

[0034] In Fig. 2 A schematic representation of a sensor matrix and individual measured values ​​assigned to a processing location P is shown. The target position of processing location P is, by way of example, located exactly at the intersection of four adjacent individual sensors. In principle, all individual measured values ​​acquired for calculating the overall measured value can be stored and considered. However, preferably only those individual measured values ​​are stored and considered for comparison with individual reference values. These individual values ​​must originate from sensors whose center-to-center distance to the target position of the processing location does not exceed a predefined distance and is advantageously smaller than the maximum dimensions of an individual sensor. Therefore, in this example, the individual measured values ​​of sensors 14, 15, 22, and 23 are considered, and thus only the individual measured values ​​of the four sensors located directly at processing location P are stored.If the machining location P is located relative to these individual sensors 14, 15, 22, and 23 exactly where its target position is, then the individual measured values ​​each correspond to the associated individual reference values. Deviations indicate a positional deviation of the actual position from the target position. If the actual position is shifted, for example, diagonally across individual sensor 22, the magnitude of the individual measured value from individual sensor 22 increases, while the magnitude of the three individual measured values ​​from individual sensors 14, 15, and 23 decreases. In the example shown here, the total measured value is also calculated from only these four individual measured values. In principle, the individual measured values ​​from two individual sensors are sufficient to conclude, in comparison with the respective individual reference values, that the machining location is not in its target position.By specifying that only the individual measurements from sensors whose center distance to the target position of the machining point is less than the maximum dimensions of a single sensor are used, the individual measurements of a maximum of six sensors are considered. Only in the special case where the machining point coincides exactly with the center point of a single sensor is only one measurement considered under this specification. In this case, the actual position of this machining point can be determined by interpolation from the actual positions of the neighboring machining points.

[0035] If the remaining wall thickness is to be constant along the entire predetermined breaking line, the same overall reference value is stored for all processing locations P. However, this value varies locally due to a different number and different individual reference values. These different individual reference values ​​enable position determination.

[0036] Depending on the requirements for quality assessment, limit values ​​for the permissible deviations of the individual measured values ​​can be stored, if these are exceeded, the hole created at the respective processing location P is assessed as being out of tolerance with its actual position.

[0037] Alternatively, in addition to the stored individual reference values ​​assigned to the target position of the respective processing location P, individual comparison values ​​can be stored for each processing location P. These comparison values ​​are assigned to a specific deviation of the processing location P from the target position. From the individual measured values ​​obtained and stored at a processing location P, the actual position of the processing location P can thus be determined by interpolation using the individual comparison values.

[0038] Individual measured values, and corresponding individual reference values ​​and individual comparison values, are values ​​derived from the electrical signals generated by the individual sensors. These can be, for example, the signal amplitudes or the integral under the signal. The overall measured value is calculated from the individual measured values ​​by summation or other known processing rules. The individual measured values ​​can be weighted differently. In the case of the Fig. 2 In the example shown, the signal amplitudes are weighted equally in the overall measurement, regardless of any parameter tolerances of the individual sensors. In more practical terms, the individual sensors are weighted differently. This weighting results from the characteristics of the individual sensors, such as their response time and sensitivity range, which are subject to fluctuations. The weighting is applied to minimize these fluctuations in sensor parameters.

[0039] In a special case, the target position of the machining point P is located horizontally and vertically exactly midway between the individual sensors 14 and 15. The center-to-center distance of the adjacent individual sensors is greater than the maximum dimension of any single sensor, meaning that only the individual measurements of sensors 14 and 15 are recorded and compared with individual reference values. This illustrates that the individual measurements of adjacent sensors must also be considered to calculate the overall measurement value, since if the machining point deviates significantly from the target position, the desired remaining wall thickness will be reached much sooner than the overall measurement value will reach the overall reference value.

[0040] The inventive method monitors the remaining wall thickness at each machining location and controls the machining of the holes at these locations by locally terminating the machining process when a total reference value is reached. Simultaneously, a deviation of the actual position of the machining location from a target position is inferred from at least some of the individual measurements that constitute the total measurement. This allows not only the determination of a positional deviation, but also whether it lies within a predetermined tolerance and where the actual position is located as a result of the deviation. From this information about the individual machining locations, the contour and position of the predetermined breaking line on the vehicle interior trim panel can be determined. Reference symbol list

[0041] 1 Vehicle interior trim panel 2 Break line 3 Sensor matrix PProcessing location AWorking plane SLaser beam

Claims

1. A method for producing a break line (2) in a vehicle interior trim part (1), wherein the vehicle interior trim part (1) is arranged in a working plane (A) between a sensor matrix (3) and a laser scanning device (4), the laser scanning device (4) scans a laser beam (S) on an inner side of the vehicle interior trim part (1), along the break line (2), wherein material removal in the form of holes is successively effected in each case down to a predetermined residual wall thickness at respective machining locations (P) along the break line (2), a portion of the laser beam (S) transmitted successively at the machining locations (P) causes individual measured values for individual sensors of the sensor matrix (3), at least some of which are recorded, and a respective total measured value is formed for each respective machining location (P) from individual measured values recorded simultaneously and is compared in each case with a respective stored total reference value to which the predetermined residual wall thickness is assigned, and when the total measured value has reached the total reference value, the laser beam (S) is switched off, characterized in that the vehicle interior trim part (1) is arranged in the working plane (A) in a known relative position to the sensor matrix (3) and to the laser scanning device (4), and at least some of the recorded individual measured values of a respective total measured value, when the latter reaches the total reference value, are stored in a manner assigned to the respective individual sensor and the respective machining location (P) and are each compared with a stored individual reference value assigned to the respective individual sensor and the respective machining location (P), which stored individual reference value is assigned to a target position of the machining location (P), and any resulting deviations are used to evaluate the contour and position of the break line (2).

2. The method according to claim 1, characterized in that an actual position of the respective processing location (P) is derived from the simultaneously recorded, stored individual measured values of a total measured value that has reached the total reference value in each case, said actual position is compared with a target position stored for the respective machining location (P) and the quality evaluation is carried out by inspecting the position and course of the produced break line (2).

3. The method according to claim 2, characterized in that the individual measured value is stored and compared for each machining location (P) only for the individual sensors that have a center distance to the target position of the machining location (P) that is smaller than a maximum extension of any individual sensor.

4. The method according to claim 2, characterized in that the individual measured value is stored and compared for each processing location (P) precisely for the two individual sensors for which the highest individual reference value, in comparison to the other individual reference values assigned to the machining location (P), is recorded.

5. The method according to any one of the preceding claims, characterized in that an individual sensor is concluded to be defective if at least one of the individual sensors read out provides no individual measured value or an individual measured value that deviates by more than 50% from the assigned individual reference value.

6. The method according to any one of the preceding claims, characterized in that a deviation of an individual measured value from the assigned individual reference value indicates a position deviation of the actual position of the machining location (P) from its target position, wherein a position deviation away from the center point of the relevant individual sensor is inferred if the individual measured value of the relevant sensor is smaller than the assigned individual reference value, and wherein a position deviation toward the center of the individual sensor concerned is inferred if the individual measured value is greater than the assigned individual reference value.

7. The method according to claim 1, characterized in that, at individual machining locations (P), their respective actual position is determined by interpolation from the determined actual positions of adjacent machining locations (P).

8. The method according to any one of the preceding claims, characterized in that the simultaneously recorded individual measured values are included in the total measured value with a different weighting depending on a different sensitivity and / or different response times of the individual sensors.

9. The method according to any one of the preceding claims, characterized in that an upper limit for a number of position deviations outside a tolerance range is defined and the vehicle interior trim part (1) is confirmed as a usable part if the upper limit is not exceeded.

10. The method according to any one of the preceding claims, characterized in that the actual positions of the machining locations (P) are documented in relation to the target positions.