SENSOR DEVICE FOR SCANNING LASER MACHINING OF A WORKPIECE USING A LASER BEAM DEFLECTED AROUND A PIVOT POINT

Description

[0001] The invention relates to a sensor device containing an array of sensors with which, during machining of a workpiece with a laser beam scanning over the workpiece, material is removed along a predetermined breaking line until the sensors detect a portion of the laser beam transmitted through the workpiece. A sensor device of this type is known from US Pat. No. 4,914,284 A.

[0002] The production of predetermined breaking lines in vehicle equipment elements, e.g. for airbag openings in the dashboard, in the door trim or in the steering wheel hub, or as breaking points on components that protrude into the passenger compartment, such as cup holders, using lasers has been known for a long time. Due to the high demands on their reliable breaking open when necessary and on the aesthetic appearance of the equipment parts, where vehicle occupants should not be able to see the predetermined breaking openings with the naked eye, the material removal along the predetermined breaking lines surrounding the predetermined breaking openings is sensor-controlled. In other applications too, e.g. in the packaging industry, it is known to incorporate predetermined breaking lines as cutting aids in containers and the like. To produce a predetermined breaking line by laser ablation, slits or holes that do not cut through completely are drilled into the workpiece in question.so-called micro-perforation holes, which only penetrate the workpiece with a very small hole, are introduced. Sensor monitoring can be used to produce either a reproducible remaining defined residual wall thickness or small holes with a reproducible diameter along the predetermined breaking line. When radiation energy is detected transmitting through the residual wall or the hole, the exceeding of a predetermined threshold value is used as a control variable. For this purpose, at least one sensor is arranged on a side of the workpiece opposite the laser (visible side). This sensor detects a transmitting portion of the processing laser radiation during processing when the workpiece only has a certain residual wall thickness or already has a micro-hole within the predetermined breaking line at the respective processing point.The relative movement required to create predetermined breaking lines using energy radiation can in principle be generated by the laser beam as a tool or by the workpiece, although the movement of the laser beam has proven to be easier to implement. Compared to robot-controlled guidance of a laser source above and along the predetermined breaking line, two- or three-dimensional scanning of a laser beam along the predetermined breaking line is technically simple to implement and also allows for significantly faster processing. However, the arrangement and, in particular, the alignment of the sensors is more difficult here. These sensors cannot be arranged in an array with the same alignment of their sensor axes if the laser beam is scanned by deflecting a mirror, since in this case the laser beam hits the workpiece at a different angle at each processing point along the predetermined breaking line.Assuming that the laser beam is focused on the back of the workpiece when guided along the predetermined breaking line or, in the case of workpieces with greater wall thickness, is possibly refocused to the current removal depth during removal, the sensors must be arranged at an equal distance from the visible side and each face in the direction of the scanning laser beam, i.e. the sensor axes, which are each orthogonal to a radiation-sensitive receiving surface of the sensors, are aligned in the direction of the laser beam that may directly impinge on it when it is scanned along the predetermined breaking line.Particularly for extended workpieces with predetermined breaking lines that define larger predetermined breaking openings, such as an airbag exit opening in a dashboard, the effort required to manufacture and assemble a suitable sensor device containing the sensors and a holding device in which the sensors are arranged and aligned relative to one another is complex. If a predetermined breaking line with a different line layout is to be produced on the same workpiece, a different holding device or at least a structural modification to the holding device is required.

[0003] US Pat. No. 4,914,284 A discloses an optical wide-angle sensor head comprising a mount in the form of a mounting plate in which the individual optics are arranged such that the directions of their optical axes have a common intersection point in front of the sensor head. The mounting device is thus individually designed for a predetermined arrangement of the individual optics.

[0004] It is the object of the invention to provide a sensor device for scanning laser processing of a workpiece with a holding device which allows a spatially flexible and changeable arrangement of the sensors and is easy to manufacture.

[0005] This object is achieved by a sensor device for scanning laser processing of a workpiece by means of a laser beam deflected about a pivot point, with a holding device and at least two sensors, wherein the holding device is formed from a matrix-shaped or honeycomb-shaped arrangement of sleeves firmly connected to one another, consisting of individual sleeves which are open at least on one side and each have a sleeve axis, wherein the sleeve axes intersect at an intersection point outside the holding device, and the at least two sensors, which each have a sensor axis, are each arranged in one of the sleeves in such a way that their sensor axis coincides with the sleeve axis.

[0006] Advantageous embodiments are specified in the subclaims.

[0007] It is particularly advantageous to manufacture the holding device as a monolithic component using a generative process, also known as 3D printing. In addition to speeding up the entire manufacturing process while using minimal material, this process offers the advantage that a component can also be manufactured with undercuts, which are difficult to avoid when designing the interior of the sleeve as a plug-in connection for a sensor. Particularly when a large number of sensors with high local resolution are to be arranged optionally in the holding device, a design of the holding device formed by a matrix- or honeycomb-structured arrangement of sleeves that can be reduced to the size of the sensors as far as possible and are connected to one another monolithically or by a material bond, is very advantageous.Such an arrangement of firmly connected sleeves leads to a high level of internal stability in the component, even when the sleeve walls are thin. The outer cross-section and the inner cross-section of the sleeves can have different shapes, and the sleeve walls can merge into one another. In the broadest sense, the arrangement of the sleeves can also be formed by through-holes or blind holes in a plate. The inner contour of the sleeves is advantageously designed in such a way that the sensors are held centered in the sleeve via a plug-in connection, so that the sensor axes of the inserted sensors and the sleeve axes coincide and intersect at an intersection point around which the processing laser beam can be deflected during the processing of a workpiece.Due to the low radiation power transmitted through the workpiece during machining, the holding device can be made of plastic, making it ideal for injection-molded parts or, in particular, for 3D printing. The sensors can be relocated to a different sleeve if necessary, e.g., if the cutting line guide changes.

[0008] The invention will be explained in more detail below using exemplary embodiments and drawings. These show: Fig. 1 shows a workpiece to be machined and a sensor device arranged therefor, Fig. 2a shows a sectional view through a sensor device lying on the workpiece via a mating surface, Fig. 2b shows a sectional view through a sensor device lying on the workpiece via spacers, Fig. 3a shows a first embodiment of a sleeve for receiving a sensor and Fig. 3b shows a second embodiment of a sleeve for receiving a sensor.

[0009] In Fig.1 is a sensor device according to the invention for processing a workpiece 0 by means of a scanning laser beam, which is deflected around a pivot point, arranged as intended on a rear side of the workpiece 0. The laser beam, which can be deflected around a pivot point, is directed onto a front side of the workpiece 0 and, depending on the degree of deflection, strikes the workpiece 0 at a different angle. In order for a portion of the laser beam transmitted through the workpiece 0 to be optimally detected by a sensor 2 arranged downstream of the workpiece 0, the sensor axis 2.0 (in Fig. 1 not shown) of the sensor 2, which is orthogonal to the radiation-sensitive receiving surface of the sensor 2, must be directed in the direction of the incident laser beam, i.e. the sensor axes 2.0 must intersect at the pivot point.

[0010] A sensor device according to the invention basically contains a holding device 1 and at least two sensors 2. The holding device 1 has a matrix or, as in Fig. 1 shown, a honeycomb-structured arrangement of sleeves, consisting of individual sleeves 3. The sleeves 3 have, as in the Fig. 2a und 2b shown, each has a sleeve axis 3.0 and a sleeve wall 3.5, which are defined by a first end face 3.1 and a second end face 3.2 (see Fig. 3b ) or a floor area 3.3 (see Fig. 3a ) is limited,

[0011] In order for the sensors 2 inserted into the sleeves 3 to be aligned in the direction of an incident laser beam, the sleeves 3 are arranged relative to one another such that the sleeve axes 3.0 intersect at an intersection point P on the side of the first end faces 3.1 outside the holding device 1. The laser beam is deflected around this intersection point P during processing, i.e. the sensor device is arranged as a device scanning the laser beam such that the intersection point P coincides with the pivot point around which the laser beam is deflected. The inner contour of the sleeves 3 is designed such that the sensors 2 are held centered within the sleeve 3 upon insertion into the sleeve 3, so that their sensor axis 2.0 coincides with the sleeve axis 3.0.

[0012] Advantageously, the first end faces 3.1 together form a coherent mating surface which is adapted to the surface contour of the workpiece 0 in a processing area. Adapted here means that the mating surface has the same surface contour as the workpiece 0 in the processing area, or has an approximately identical surface structure, wherein the centers of the first end faces 3.1 each lie on an imaginary surface with the same contour as the workpiece 0. The sensor device can thus, as in Fig. 2a shown, are placed with their mating surface directly on the surface of the workpiece 0. The sensors 2 arranged in a sleeve 3 in the sensor device then each have an equal vertical distance to the workpiece 0. In the Fig. 2a und 2b In the sleeves 3 shown, instead of a second collar 3.4.2, three spring elements 3.4.3 are formed on the sleeve wall 3.5, for example. In principle, any internal design and any internal contour of the sleeve 3, e.g., polygonal or round, is possible, as long as it is suitable for accommodating the sensor 2 in such a way that its sensor axis 2.0 coincides with the sleeve axis 3.0. Advantageous, in particular for production using a 3D printing process, is a sleeve shape in which an outer circumferential line of the cross section of the sleeve 3 has a hexagonal shape and an inner circumferential line of the cross section of the sleeve 3 has a circular shape.

[0013] As an alternative to a formed mating surface, spacers 5 are formed on some of the first end faces 3.1, to which the workpiece 0 can be placed, as in Fig. 2b shown.

[0014] Advantageously, the sensor device has more sleeves 3 than sensors 2, whereby the sensors 2 are arranged relative to one another to form a selectable pattern. The pattern is determined by the linear path of a predetermined breaking line, which is to be introduced into the workpiece 0 and along which the laser beam is scanned over the workpiece 0.

[0015] The inner contour of the sleeves 3 is designed to provide a plug-in connection for the sensors 2. Thus, a first collar 3.4.1 is advantageously formed in each of the sleeves 3, within or on which one of the sensors 2 is held.

[0016] Advantageously, the first and optionally a second collar 3.4.1, 3.4.2 each have a circular inner contour and the sensors 2 have a cylindrical outer contour.

[0017] According to a first embodiment of the sleeve 3, shown in Fig. 3a ,The first collars 3.4.1 each have an end face concentrically enclosing the sleeve axis 3.0, in which an annular groove is formed, in which a sealing ring 4 is arranged, which encloses the sensor 2 in a force-fitting manner. In this exemplary embodiment, the sleeve wall 3.5 is delimited on one side by a bottom surface 3.3 and is thus closed on one side except for an opening for a media cable 7 connected to the sensor 2. A raised portion 6 is shown in the center of the bottom surface 3.3, against which the sensor 2 is placed during installation in the sleeve 3 and is then held centered by the raised portion 6 and the sealing ring 4.

[0018] According to a second embodiment of a sleeve 3, shown in Fig. 3b , the first collars 3.4.1 each have a conical inner surface facing the second collar 3.4.2, to which the sensor 2 is applied in a force-fitting, centered manner.

[0019] Advantageously, the holding device 1 is a monolithic component manufactured using a generative manufacturing process. Additional small parts for securing the sensors 2 in the sleeves 3, such as a rubber seal or spring elements 3.4.3, can be inserted into grooves provided for this purpose in the sleeve walls 3.5. List of reference symbols

[0020] 0Workpiece 1Holding device 2Sensor 2.0Sensor axis 3Sleeve 3.0Sleeve axis 3.1First end face (of sleeve 3) 3.2Second end face (of sleeve 3) 3.3Bottom surface (of sleeve 3) 3.4.1First collar (on sleeve 3) 3.4.2Second collar (on sleeve 3) 3.4.3Spring element (on sleeve 3) 3.5Sleeve wall 4Sealing ring 5Spacer 6Protrusion 7Media cable PIntersection point (of the sleeve axes 3.0)

Claims

1. A sensor device for scanning laser machining of a workpiece (0) by means of a laser beam rotating around a point, comprising a holding device (1) and at least two sensors (2), characterized in that the holding device (1) is formed by a matrix- or honeycomb-shaped arrangement of firmly interconnected sleeves, consisting of individual sleeves (3) open on at least one side, each having a sleeve axis (3.0), the sleeve axes (3.0) intersecting at a point of intersection (P) outside the holding device (1), and the at least two sensors (2), each having a sensor axis (2.0), each being arranged in one of the sleeves (3) such that their sensor axis (2.0) coincides with the sleeve axis (3.0).

2. The sensor device according to claim 1, characterized in that the sleeves (3) each have a sleeve wall (3.5) which is bounded by a first end face (3.1) and a second end face (3.2) or a bottom face (3.3), and the point of intersection (P) is located on the side of the first end faces (3.1).

3. The sensor device according to claim 2, characterized in that the first end faces (3.1) together form a contiguous mating surface which is adapted to the surface contour of the workpiece (0) in a machining area.

4. The sensor device according to claim 2 or 3, characterized in that some of the first end faces (3.1) are provided with spacers (5) facing away from the holding device (1), against which spacers (5) the workpiece (0) can be applied.

5. The sensor device according to claim 1, characterized in that sensor device has more sleeves (3) than sensors (2), which means that the at least two sensors (2) are mutually arranged with respect to one another to form a selectable pattern.

6. The sensor device according to claim 1, characterized in that in each of the sleeves (3) first and second collars (3.4.1, 3.4.2) are formed, within which one of the sensors (2) is held.

7. The sensor device according to claim 6, characterized in that the first and second collars (3.4.1, 3.4.2) each have a circular inner contour and the sensors (2) have a cylindrical outer contour.

8. The sensor device according to claim 6, characterized in that the first collars (3.4.1) each have an end face concentrically enclosing the sleeve axis (3.0), in which end face an annular groove is formed, in which a sealing ring (4) is arranged which encloses one of the sensors (2) in a force-fitting manner.

9. The sensor device according to claim 6, characterized in that the first collars (3.4.1) each have a conical inner surface on which one of the sensors (2) is centered in a force-fitting manner.

10. The sensor device according to any one of the preceding claims, characterized in that the holding device (1) is a monolithic component.

11. The sensor device according to claim 10, characterized in that an outer circumferential line of the cross-section of a sleeve (3) has a hexagonal shape and an inner circumferential line of the cross-section of the sleeve (3) has a circular shape.