EP2393626A1

EP2393626A1 - Apparatus having scanner lens for material processing by way of laser

Info

Publication number: EP2393626A1
Application number: EP10715656A
Authority: EP
Inventors: Pravin Sievi
Original assignee: Scansonic MI GmbH
Current assignee: Scansonic MI GmbH
Priority date: 2009-02-09
Filing date: 2010-01-21
Publication date: 2011-12-14
Also published as: CN102307698B; DE102009057209B4; US20110290780A1; CN102307698A; WO2010088873A4; WO2010088873A1; DE102009057209A1

Abstract

The invention relates to an apparatus equipped with a scanner lens (pre- or post-objective scanning) for material processing by way of laser (1), in particular for laser welding. The apparatus comprises an image sensor (18), which can be moved along with the scanner lens (2a, 2b) and which is optically integrated into a partial region of the beam path of the scanner lens (2a, 2b), the partial region beginning with the processing position (16) on the workpiece (7), and at least one projector (10), which can be moved along with the scanner lens (2a, 2b) and is used to project measurement light (11) in the form of measurement structures onto the workpiece (7) to be processed. The image sensor (18) is sensitive in the wavelength range of the measurement light (11) emitted by the projector (10) and arranged on the side of a deflection unit (4a, 4b) facing away from the beam path, the unit allowing light in the wavelength range emitted by the projector (10) to be transmitted and reflecting light in the wavelength range emitted by the processing laser (1). The apparatus can be used to weld geometric patterns having high resolution, such as fine hollow and crimp seams, without difficulty in mass production.

Description

Device with scanner optics for material processing by laser

The invention relates to a device with a scanner optics (pre- or post-objective scanning) equipped for material processing by laser, in particular for laser welding, which recognizes the processing positions on the workpieces to be machined independently and with little error by means of a sensor. This makes it possible to compensate for machine- and workpiece-related positioning errors using the scanner optics. With the device mass production uncomplicated geometry pattern with high resolution, such as. B. fine KeN and flanged seams, are manufactured, which previously required a very large effort.

From the state of the art, scanner optics with deflection units for lasers are known, which enable positioning of the laser processing beam by adjusting the deflection units. As deflection units usually mirrors are used. Significantly higher speed and acceleration characteristics can be achieved with scanner optics than with guide machines; on the other hand, they make it possible to write seams and contours on the workpieces to be machined during the movement of the guide machine, independently of this. As a result, the production times can be lowered sustainably.

Scanner optics work either on the principle of pre-objective scanning or post-objective scanning.

In scanner optics, which operate on the principle of pre-objective scanning, the divergent laser beam first passes through a collimation unit, is then deflected via one or more active (adjustable) deflection units and finally imaged via a focusing on the workpiece to be machined. The focusing unit is equipped with an optical lens or a plan-field lens.

Scanner optics according to the principle of post-objective scanniηg also have a collimation unit, but the focusing unit is at least before a deflection unit, ie by the deflection unit, the already focused laser beam is positioned on the workpiece.

In addition to the active deflection units, passive (fixed) deflection units which serve to guide the beam are often used in the scanner optics.

With the conventional scanner optics, however, only comparatively low positioning accuracies of the laser spot can be achieved when machining workpieces. The reason for this is the accumulated errors of the tolerance chain of the overall system consisting of guide machine, scanner optics and workpiece.

The scanner optics are usually used relative to the moving workpieces. Either the scanner optics is stationary and the workpiece moves relative to this or the scanner optics is moved by means of a guide machine and das.Werkstück is fixed in place. The actual vector of the relative velocity and the actual Cartesian position between the workpiece processing point and the scanner optics must therefore be known to the scanner optics in order to first determine the starting point for the laser spot and then track it according to the geometry programming. While the vector of the relative velocity can still be determined comparatively accurately, the position of the scanner optics relative to the workpiece is severely flawed due to elastic deformations of the arrangement, the limited resolution of the displacement sensors of the guide machine, manufacturing tolerances of the workpieces and positional deviations of the workpiece caused by the tensioning device ,

There are also errors in the scanner optics, which are mainly caused by the limited dynamics of the drives and the limited resolution of the displacement sensors. Due to the unfavorable optical imaging ratios and large working distances (small changes in the deflection mirrors cause large changes in the position of the laser spot), these errors have a particularly strong effect on the positioning accuracy. Finally, when assessing the error, it must also be considered that the diameter of the laser spots is typically only 0.3 mm 0.6 mm.

Conventional scanner optics are therefore used only in areas where the positioning accuracy requirements of the laser spot are comparatively low. So z. B. welded in vehicle only overlap seams, the width of the overlap is chosen so that even with unfavorable summation alier tolerances the seams on the workpiece in the allowable tolerance range. As a result, the flange widths are unnecessarily large, which is counterproductive, since in vehicle always lighter, material-reduced bodies are sought. The welding of fillet welds on the lap joint or seams is not possible. By welding fillet welds, however, the flange widths could be significantly reduced and, in addition, the welding speeds could be increased while the laser power remained constant.

The object of the invention is to find a device equipped with a scanner optics for material processing by means of laser, which detects processing positions on the workpieces to be machined independently and poor in error. By increasing the positioning accuracy of the laser spot uncomplicated geometry pattern with high resolution, such. B. fine throat or flanged seams, be manufacturable.

This object is achieved by the characterizing features of claim 1. Further advantageous embodiments will become apparent from the claims 2 to 10.

The starting point is a device for material processing by means of a laser, in particular for laser welding, with a scanner optic movable relative to the workpiece to be machined by a guide machine. The scanner optics is either stationary and the workpiece is moved relative to this or the workpiece is stationary and the scanner optics is moved by means of a guide machine. The scanner optics, whose beam path is defined by one or more active and / or passive deflection units, operates either on the principle of pre-objective scanning or post-objective scanning. - A -

According to the invention, the device comprises a projector which serves to project measurement light in the form of measurement structures onto the workpiece to be processed, and an image sensor which is sensitive in the wavelength range of the measurement light emitted by the projector. The projector and the image sensor are connected to the scanner optics and thus are moved during operation of the device with the scanner optics. The image sensor is integrated with the part of the beam path of the scanner optics, which starts at the impact position on the workpiece. For optical decoupling from the beam path, the image sensor is arranged on the side of a deflection unit (hereinafter: behind) which is transparent to the wavelength range of the light emitted by the projector and reflects the light out of the wavelength range of the processing laser.

It is intended to arrange the image sensor behind a passive deflection and use as a light source for the projector, a laser emitting light of a different wavelength than the processing laser, as well as to perform the passive deflection as partially transmissive mirror, which is provided with interference layers, these being the light reflect the laser and let through the light of the projector laser.

Hereinafter, in the description, the optical path is from the point of view of the processing location, i. in the direction starting at the machining location on the workpiece and ending at the laser, defined.

Particularly suitable for decoupling the sensor signal is that passive deflection unit which is arranged in the beam path behind the last active deflection unit of the scanner optics or the passive deflection unit which follows directly in the beam path to the focusing.

Due to this construction, the measuring field of the sensor is moved synchronously in all available degrees of freedom with the laser processing beam. Since the laser processing beam in the scanner optics runs coaxially or approximately coaxially to the axis of incidence of the sensor in at least one area of the optics, position and geometry errors from the overall optical or mechanical structure can not affect the measurement result. Since, in the simple embodiment, the projector is stationary, but the area monitored by the sensor on the workpiece can be positioned over the deflection units in the entire field of operation of the scanner optics. it is only possible to detect the measuring light projected onto the workpiece by the sensor when the deflection units are aligned such that the measuring light impinges on the measuring field of the sensor. To overcome this limitation across the seam longitudinal direction, a projector is used which projects onto the workpiece lines transverse to the longitudinal direction of the seam to be formed on the workpiece, the lines extending over the entire working field of the scanner optics.

The measuring light contains one or more projection lines, the number of lines depending on the required correction dimensions. When using a measuring line, the height difference, the offset transverse to the seam longitudinal direction and the rotation about the seam longitudinal direction can be determined, while with three measuring lines all spatial dimensions can be determined.

In order that the environmental influences caused by the laser process, such as temperature gradients, the resulting plasma torch, welding fumes and spatters, do not significantly falsify the measuring signal, the lines of the measuring light must always maintain a distance to the position of incidence of the laser beam. In particular, they must not cross the laser beam. This requirement is achieved in that a distance in the longitudinal direction of the seam can be specified by the projector. In terms of process technology, it is favorable if the projection line always has a flow with respect to the processing point.

The device is equipped with a control unit which calculates the machining positions on the workpiece by means of triangulation and / or light-slit method from the sensor data and controls the active deflection units of the scanner optics by means of this position data. With the known methods of triangulation (one-dimensional) or the light-section method (multidimensional), the position in the room can be deduced from the position of the receiving beam in the measuring field of the sensor due to the known angular relationship between the projector and the sensor. In the multidimensional area is no longer just a Measuring point, but a profile captured by the sensor, which contains geometric characteristics by which the machining position can be determined. This makes it possible to control the deflection units of the scanner optics so that the laser beam is always projected comparatively accurately to the desired machining position.

Usually, the scanner optics is mounted on the guide machine and is moved by this relative to the workpiece. Without further measures, the process speed thus necessarily coincides with the speed (guide speed) determined by the guiding machine. In order nevertheless to be able to work with different speeds, in one embodiment of the device according to the invention, the active deflection units of the scanner optics are synchronized with the guide machine with the aid of the control unit in such a way that, in addition to the seam guide, the process speed is reduced or increased compared to the guide speed with the scanner optics can be moved by the laser beam with the scanner optics in or against the predetermined direction of the guide machine movement.

For this purpose, before starting the seam guide, the active deflection units of the scanner optics are pivoted so far in the feed direction that the measuring light line / measuring light lines is / are positioned at the lower end of the sensor measuring field. After positioning the laser spot on the joining edge, the seam guide is started at this end and the required process speed is synchronized with the actual movement of the guide machine by means of a compensation movement in the feed direction, realized by the scanner optics. In order to achieve higher cycle times, the guide speed is usually higher than the process speed. During processing of the workpiece, therefore, the projection line travels from the lower end of the sensor measuring field to the upper end. With sufficiently linear workpiece contours, the compensation movement can also be extrapolated beyond the field of view of the sensor / camera image.

Due to the line projection onto the workpiece, with a stationary projector, a seam tracking transversely to the seam longitudinal direction is not possible in principle. If a continuous seam tracking at small workpiece radii or workpiece edges, the be at a steep angle to each other, to be realized, the leading machine must reorient the scanner optics within a small time-Λ / Vegabschnitts what technically can be realized only with great effort. In order to avoid this limitation in advance, in one embodiment of the device either several projectors are used, or a projector is mounted such that it can be pivoted about an additional degree of freedom around the processing point around. For all degrees of freedom, the current position must be recorded by the measuring beam of the projector and calculated out of the sensor data. Panning of the projector can be done electro-mechanically, optically or electro-pneumatically.

Furthermore, during the measuring operation, the projector can also be actively positioned in the seam longitudinal direction via one or more separate projector degrees of freedom. This makes it possible on the one hand, to keep the flow between the measuring light lines from the projector and the laser spot and thus the sensor measuring field variable, on the other hand, by exploiting the entire scanner field by means of a synchronized movement between the projector and deflection units of the scanner optics a larger Seam guiding area in the seam longitudinal direction obtained or can a greater difference between the leadership and process speeds can be achieved.

In order to keep process environmental influences such as the thermal plasma torch, the welding smoke and the splash, which inevitably arise during the laser process and can lead to a disturbance of the image sensor signal from the projector / projectors, the device may be equipped with at least one Prozessjet. The process jet uses compressed gas (compressed air) to create a flow of air that moves the process environmental effects out of the surrounding area of the projector. The process jet, like the projector, is connected to the scanner optics and is therefore moved together with the projector.

Depending on whether a single and stationary mounted projector, multiple projectors or a tiltable projector is used, to ensure that the process environmental influences are always safely blown away from the projector, a stationary mounted process jet, multiple process jets, or a process jet that is pivotally mounted like the projector used.

The invention will be explained in more detail with reference to an embodiment; For this purpose, the figures show in schematic representation in each case a device for material processing with a scanning optics operating on the principle of the pre-objective scanning:

Fig. 1: lateral view;

Fig. 2: top view;

Fig. 3: view from the front.

In the apparatus illustrated in FIGS. 1 to 3, the light emitted by the processing laser 1 enters the scanner optical system 2b operating according to the construction principle of the post-objective scanning, is collimated with the collimation unit 3 and coupled to the passive deflection unit 4a (FIG. executed as a partially transparent mirror) directed to the focusing unit 5. There, the laser processing beam 6 is focused and, in the further course of the beam path, strikes the active deflection unit 4b (embodied as a mirror), which directs the beam 6 onto the workpiece 7 to be machined. By adjusting the active deflection unit 4b, the impact position 8 of the beam 6 on the workpiece 7 can be changed; the maximum range to which the impact position 8 can be steered by means of the deflection unit 4b defines the working field 9 of the scanner optics 2b.

The projector 10, which is mechanically connected to the scanner optics, irradiates measuring light 11 generated by a laser in the form of projection lines 12 which extend transversely to the longitudinal direction 13 of the seam onto the workpiece 7. The projector 10 has degrees of freedom 14 in the longitudinal direction 13 and also degrees of freedom 15 which allow pivoting about the target machining position 16, thereby enabling continuous seam tracking even at small radii or at edges.

Light reflected by the workpiece 7 reaches the active deflection unit 4b and is directed by the latter onto the passive deflection unit 4a. Since the passive deflection unit 4a is permeable to the lens 10 of the projector 10, it passes through it and passes through the designed as a lens sensor focusing unit 17 on the sensor measuring field 20 of the optical image sensor 18. When passing through the sensor focusing unit 17, the light is focused. The course of the received laser light defines the receiving beam 19 of the sensor 18.

The process jet 21 uses compressed gas 22 to blow away as much as possible from the projector 10 as much as possible due to the laser welding process environmental influences 23.

List of reference numbers used

I processing laser

2a Scanner-optics according to the construction principle pre-objective-scanning

2b scanner optics according to the construction principle post-objective-scanning

3 collimation unit

4a active deflection unit

4b passive deflection unit

5 focusing unit

6 laser processing beam

7 workpiece

8 impact position

9 working field

10 projector

I 1 measuring light

12 projection line

13 seam longitudinal direction

14 projector degrees of freedom in the seam longitudinal direction

15 projector degrees of freedom around the machining position

16 target machining position

17 Sensor focusing unit

18 sensor

19 Reception beam of the sensor

20 sensor measuring field

21 process jet

22 compressed gas

23 process environmental influences

Claims

claims

1. Device for material processing by means of laser (1) with a by a guide machine relative to the workpiece to be machined (7) movable scanner optics (2a, 2b), according to the principle of pre-objective scanning or post-objective scanning operates and whose beam path is guided by means of one or more active (4b) and / or passive (4a) deflection units, characterized in that they with the scanner optics (2a, 2b) mitbeweglichen image sensor (18), the optically in the the processing position (16) on the workpiece (7) beginning portion of the beam path of the scanner optics (2a, 2b) is included, and at least one with the scanner optics (2a, 2b) mitbeweglichen projector (10) includes, which serves Project measuring light (11) in the form of measuring structures onto the workpiece (7) to be machined, the image sensor (18) being sensitive in the wavelength range of the measuring light (11) emitted by the projector (10), and the image sensor (18) being at the o Optical extraction from the beam path of the scanner optics (2a, 2b) on the side facing away from the beam path of a for the wavelength range of the projector (10) emitted light and reflecting for the wavelength range of the processing laser (1) light reflected deflection unit (4a, 4b) is arranged.

2. Apparatus according to claim 1, characterized in that the image sensor (18) on the side facing away from the beam path of a passive deflection unit (4a) arranged as a light source of the projector (10) a laser, the light with a different wavelength than the processing laser ( 1), inserted and the passive deflection unit (4a) is designed as a partially transparent, provided with interference layers mirror.

3. Apparatus according to claim 1 and 2, characterized in that the image sensor (18) on the side facing away from the beam path of the passive deflection unit (4a), the beam path from the perspective of the processing position (16) following, to the last active Ablenkungseinheit (4b) connects, is arranged.

4. Apparatus according to claim 1 and 2, characterized in that the image sensor (18) on the side facing away from the beam path of the passive deflection unit (4a) is arranged, following the beam path from the perspective of the processing position (16), behind the focusing (5) of the scanner optics (2b) is arranged.

5. Apparatus according to claim 1 to 4, characterized in that a projector (10) is used, which projects onto the workpiece (7) lines (12) transversely to the longitudinal direction (13) of a seam to be produced on the workpiece (7), wherein the lines extend over the entire working area (9) of the scanner optics (2a, 2b), observe a distance to the impact position (8) of the laser beam (6) which can be predetermined by displacements in the seam longitudinal direction (13) and the laser beam (6) is not cross.

6. Apparatus according to claim 1 to 5, characterized in that it is equipped with a control unit, which by means of triangulation and / or light-cut method from the data of the image sensor (18) calculates the machining positions (16) on the workpiece (7) and by means of the position data which drives at least one active deflection unit (4b) of the scanner optics (2a, 2b).

7. Apparatus according to claim 1 to 6, characterized in that the active deflection units (4b) of the scanner optics (2a, 2b) are synchronized by means of the control unit in such a way with the guiding machine that by means of the scanner optics (2a, 2b) In addition to the seam guide, the process speed can be reduced or increased relative to the speed specified by the guide machine by moving the laser beam (6) in or against the direction of movement predetermined by the guide machine by means of the scanner optics.

8. Apparatus according to claim 1 to 7, characterized in that for multi-axis seam guide either multiple projectors (10) are used or at least one projector (10) is pivotally mounted about the beam path.

9. Apparatus according to claim 1 to 8, characterized in that it comprises at least one with the scanner optics (2a, 2b) mitbeweglichen Prozessjet (21) for generating an air flow by means of compressed gas (22), the removal of laser welding resulting vapors and the reduction of other laser-welding process environmental influences (23) that interfere with the signal of the image sensor (18), serves from the surrounding area of the projector (10) has.

10. The device according to claim 9 and 10, characterized in that to ensure the protective effect of the at least one process jet (11) either, when a plurality of projectors (10) are used, a plurality of process jets (21) are used, or if a swivelable projector (10) is used, either a plurality of process jets (21) or a process jet (21), which is also pivotally mounted, is used.