DE10339636B4 - Method and device for simultaneous laser welding - Google Patents

Abstract

Method for simultaneous laser welding of at least two workpieces along at least one common weld seam, wherein a first intensity distribution of laser light in a plane substantially perpendicular to the propagation direction of the laser light is generated by means of a laser device (1), the first intensity distribution being within an input aperture (23 ) beam shaping means (2) is converted into a second intensity distribution adapted to a contour of the weld, characterized in that the laser light is at least partially imaged in areas of the weld, of the entrance aperture (23) of the beam-forming means (2) in such a way are spaced, that a three-dimensional weld contour is generated.

Description

The present invention relates to a method for simultaneous laser welding according to the preamble of claim 1. Furthermore, the present invention relates to a device according to the preamble of claim 5.

The laser beam welding of workpieces is known from the prior art. It is increasingly replacing the traditional methods of joining workpieces such as gluing or screwing. Today, several methods are available to the user for material-fit joining of workpieces using laser beams.

In so-called contour welding, a laser beam is guided along a freely definable weld contour. Frequently fiber-coupled laser devices with round beam cross sections are used. Depending on the laser device used and the optics available, weld seam widths of a few tenths of a millimeter to several millimeters are achieved with the aid of this method.

In so-called quasi-simultaneous welding, a laser beam is guided at high speed along a weld contour using galvanometric mirrors (so-called scanner mirrors). Due to the high speed with which the laser beam is guided, the entire joining area is heated and plasticized very quickly (quasi-simultaneously). However, the welding of three-dimensional seam contours is relatively complicated and can only be implemented to a limited extent because of shading or unfavorable angles of incidence on curved surfaces. Furthermore, tensions or distortions often occur, which adversely affect the durability of the weld.

In so-called mask welding, an approximately line-shaped laser beam is moved across the workpieces to be welded. A mask selectively shadows the laser beam so that it only hits the joining surface at the points where welding is to take place. The field of application of the Meskenschweißens lies mainly in the field of sensors, chips and electronic components as well as microsystems technology. Fine structures in the mask allow a very high resolution, which allows welds of less than 100 microns width. In a single operation, straight and curved lines of different widths can be created and flat areas welded together.

In so-called simultaneous welding, individual, essentially line-emitting laser diodes or lasers or laser diodes with cylindrical lens optics are arranged to produce line-shaped laser beams along the seam contour to be welded. The melting and welding of the entire contour takes place simultaneously in this process (simultaneously). The number of laser diodes required for this depends on the circumference of the weld seam contour and the laser power required for welding. The method requires no relative movement between the component and the laser beam. The weld geometry can be chosen freely within a certain framework and has so far been limited to two-dimensional contours, which are constructed from individual straight lines.

A device and a method of the type mentioned are from the EP 0 282 593 A1 known. The device described therein comprises a laser light source and a beam shaping body having an entrance aperture and an exit aperture. Lens means can image the laser light generated by the laser light source onto the entrance aperture. The entrance aperture and the exit aperture have a different shape and are connected to one another via a beam guiding channel in the interior of the beam-forming body. The laser light emerging from the exit aperture can be imaged into a working plane in order to be used there, for example for welding.

Object of the present invention is to provide a method of the type mentioned above and a generic device available that allows simultaneous welding of a weld with any contour.

This object is first achieved by a method of the type mentioned above with the characterizing features of claim 1. According to the invention, it is proposed that the laser light is at least partially imaged into regions of the weld seam which are spaced from the entrance aperture of the beam-shaping means such that a three-dimensional weld seam contour is produced. Thus, not only two-dimensional but also three-dimensional weld seam contours can be produced with the aid of the method according to the invention.

With the aid of the beam-shaping means, it is possible to convert the first intensity distribution into a second intensity distribution, which is shaped so that it welds the at least two workpieces along the contour of the at least one common weld seam. As workpieces, for example, thermoplastics come into consideration. Alternatively, for example, thin sheets can be welded. The method according to the invention can be carried out as a transmitted light welding method or as a joint edge welding method. At the Transverse welding, a first transparent to laser light workpiece is welded to a second workpiece, which absorbs the laser light of the selected wavelength. The laser light passes through the transparent workpieces and is absorbed at the interface between this and the second workpiece. The heat generated during absorption leads to a local melting of the material. After cooling, a cohesive joining connection is created between the two workpieces.

In the case of abutting edge welding, on the other hand, two workpieces, of which at least one laser light absorbs, are compressed under the action of external forces and welded together along their common abutment edge.

In a particularly preferred embodiment it is provided that the laser light is imaged on the entrance aperture on a first end face of the beam-shaping means. In this way, the laser light enters the beam-shaping means in a well-defined form, in which the first intensity distribution is converted into the second intensity distribution.

Preferably, the laser light exits the beam-shaping means through an exit aperture on a second end face of the beam-forming body, wherein the shape of the exit aperture deviates from the shape of the entry aperture. The shape of the exit aperture is in principle freely selectable and can thus be adapted to the contour of the weld

Furthermore, the laser light can be imaged with the aid of at least one second lens means on the weld seam of the at least two workpieces in order to obtain a sufficiently high energy density on the regions of the workpieces to be welded.

The object underlying the present invention is further achieved by a device of the type mentioned above with the characterizing features of claim 5.

According to the invention, the second end face of the beam-shaping means has a contouring with elevations and depressions arranged offset to one another in the propagation direction of the laser light and adapted to the contour of the weld seam. As a result, three-dimensional contours can also be welded by means of the device according to the invention.

In a particularly advantageous embodiment, the beam shaping means has an entry aperture, wherein the shape of the exit aperture is different from the shape of the entry aperture. In this way, the first intensity distribution of the laser light can be adapted to the contour of the weld.

The beam-shaping means may comprise at least one beam guiding channel for guiding the laser light within the beam-shaping means.

Preferably, the beam-guiding channel has at least one reflection coating for the at least partial reflection of the laser light within the beam-guiding means. At the reflection coating, the laser light is repeatedly at least partially reflected and guided to the exit aperture, where it leaves the beam-forming agent.

In a particularly advantageous embodiment, it is provided that the reflection coating is formed as a gold coating. This gold coating is characterized by a high reflectivity. Of course, it is also possible to use other reflective materials.

The beam guiding channel may be hollow, for example.

Furthermore, the beam guiding channel can be roughened for homogenizing the laser light.

To generate the laser light, the laser device may preferably have at least one laser diode bar.

Furthermore, the device may comprise first lens means for imaging the laser light onto the entrance aperture.

In a preferred embodiment, it is proposed that the device has second lens means in order to image the laser light emerging at the exit aperture onto the weld seam of the workpieces. In this way, a sufficiently high energy density is generated in the region of the seam to be welded, which is sufficient to weld the workpieces together.

Further features and advantages of the present invention will become apparent from the following description of a preferred embodiment with reference to the accompanying drawings. Show in it

1 a perspective view of a beam-forming body of a device according to the invention;

1a a detail according to 1a in 1 ;

1b a section of the beam-shaping body according to 1 cut in the longitudinal direction;

2 schematically the beam path through a device according to the invention;

3 a plan view of a laser weld produced by a method according to the invention.

First, it will open 1 Referenced. Therein is a beam forming body 2 shown in perspective, which can be used in a method according to the invention for simultaneous laser welding of at least two workpieces. The beam forming body 2 can be made using a conventional 3D CNC machining process from a, in this embodiment, substantially cuboid block of material (for example, a metal block). This will be a beam shaping body 2 get that inside part 24 and outer part 25 having.

One recognizes from the representation in 1 in that the beam-shaping body 2 on a first front side 20 a substantially square entrance aperture 22 for laser beam 10 . 11 , in the 2 are shown. It should be noted at this point, however, that the entrance aperture 22 on the first front side 20 can be arbitrarily, in particular triangular, rectangular or polygonal shaped.

On a second front side 21 that the first front page 20 is substantially opposite, the beam-shaping body 2 an exit aperture 23 on, which in principle arbitrary, formed in this embodiment of a plurality of straight and a plurality of curved sections shape of that of the entrance aperture 22 differs. Between the entrance aperture 22 and the exit aperture becomes a beam guide channel 26 formed, as in 1b shown from an outer surface 240 of the inner part 24 and an inner surface 250 of the outer part 25 is limited laterally.

As later referring to 2 will become clear, the through the entrance aperture 22 of the beamforming body 2 entering laser beam 10 . 11 several times within the beam guiding channel 26 of the beamforming body 2 before passing it through the exit aperture 23 leave again. The shape of the entrance aperture 22 deviates from the shape of the exit aperture 23 in order in this way a first intensity distribution through the entrance aperture 22 in the beam forming body 2 entering laser beam 10 . 11 during the passage of the beam guiding channel 26 to convert to a second, different from the first intensity distribution intensity distribution.

After completing the 3D CNC machining, the inner part becomes 24 for further processing from the outer part 25 of the beamforming body 2 removed. To the reflectivity of the outer surface 240 of the inner part 24 or the inner surface 250 of the outer part 25 to improve and thus reduce the reflection losses, both surfaces 240 . 250 each with at least one reflective coating 27 provided (see 1b ). The reflection coating 27 For example, it may be a gold coating or another highly reflective coating.

After application of the reflective coating 27 becomes the inner part 24 again in the outer part 25 plugged to thereby the beam forming body 2 to build.

To prevent the inner part 24 from the outer part 25 Unintentionally, the inner part becomes 24 by securing means on the outer part 25 held. The securing means, for example, a retaining pin 9 which is exemplified in 1a is shown. As a rule, several such retaining pins 9 inserted between the inner part 24 and the outer part 25 be clamped, thereby preventing the inner part 24 unintentionally from the outer part 25 of the beamforming body 2 can be solved. The retaining pins 9 are preferably only in the region of the entrance aperture 22 between the inner part 24 and the outer part 25 brought to ensure that the exit aperture 23 is illuminated substantially homogeneously and not by the retaining pins 9 is covered. Optionally, the reflective coating 27 for the homogenization of the laser beam 10 . 11 roughened specifically.

In 2 the beam path of a device according to the invention for simultaneous laser welding is shown. To simplify the further embodiments, a Cartesian coordinate system is also shown. An essential component of the device according to the invention is that already described with reference to FIG 1 beam shaping body described 2 , Furthermore, the apparatus for carrying out the simultaneous laser welding process comprises a laser device 1 for generating laser light. Exemplary here are only two laser beam 10 . 11 shown to explain the operation of the device in more detail. The laser device 1 For example, it may comprise at least one laser diode bar or other known lasers or laser diodes.

The device also has a first lens means 3 , in the propagation direction of the laser beam 10 . 11 (x-direction) viewed in front of the beam-shaping body 2 is arranged to the laser beam 10 . 11 on the entrance aperture 22 of the beamforming body 2 map. In the propagation direction are considered behind the beam-shaping body 2 second lens means with lenses 4 . 5 arranged to the laser beam 10 . 11 after passing through the beam-forming body 2 from the exit aperture 23 on a weld of the workpieces to be welded together 6 map.

It can be seen that the laser beam 10 . 11 that from the laser device 1 are emitted, first the first lens agent 3 go through and on the entrance aperture 22 of the beamforming body 2 (compare also 1 ), which in this embodiment is substantially square. In this way, a first intensity distribution of the laser beam 10 . 11 generated in a first, oriented substantially perpendicular to the propagation direction plane (yz plane).

Within the beamforming body 2 become the laser beam 10 . 11 several times at the reflection layers 27 the inner or outer surfaces 240 . 250 of the beam guiding channel 26 reflected and finally arrive at the exit aperture 23 of the beamforming body 2 that, as already in 1 shown one of the geometry of the entrance aperture 22 has different, multi-curved shape. In this way, in the area of the exit aperture 23 a second intensity distribution of the laser light beams 10 . 11 generated, which deviates from the first intensity distribution.

This makes it clear that the weld 7 , in the 3 is shown in a plan view, has a two-dimensional contemplated, which is the shape of the exit aperture 23 of the beamforming body 2 equivalent.

One recognizes from the representation in 2 that the second end face 21 of the beamforming body 2 furthermore has a contouring. That means the second end face 21 of the beamforming body 2 elevated areas 210 and recessed areas 211 includes. The second front side 21 is contoured in this embodiment, so that not only two-dimensional but also three-dimensional weld seam contours can be generated by means of the device according to the invention.

Together with the arbitrary shape of the exit aperture 23 performs this contouring of the second end face 21 So that the laser beam 10 . 11 the workpieces 6 can weld together simultaneously along a three-dimensional weld contour. This happens because the pixels of the laser beam 10 . 11 after passing through the second lens means in the x-direction at different distances from the exit aperture 23 are removed and thereby in addition to a shaping of the weld 7 in the yz plane also a deep contouring of the weld 7 allowed in the x direction, leaving the weld 7 becomes three-dimensional overall.

Each individual contoured, so with increases 210 and depressions 211 provided subsection of the exit aperture 23 of the beamforming body 1 then acts almost like a single laser light source, the two-dimensional outline of the weld 7 who in 3 is shown, the shape of the exit aperture 23 in the second end face 23 corresponds and the depth contouring by the contouring of the second end face 21 of the beamforming body 2 comes about. Only in the area of their pixels does the energy density of the laser beam reach 10 . 11 to locally heat the workpiece (or the workpieces) so much that the material can locally melt there.

The simultaneous laser welding method according to the invention and the device according to the invention can be used for so-called transmission welding or for abutting edge welding. In transmission welding, a first workpiece transparent to laser light is welded to a second workpiece which absorbs the laser light of the selected wavelength. The laser light passes through the transparent workpieces and is absorbed at the interface between this and the second workpiece. The heat generated during absorption leads to a local melting of the material. After cooling, a cohesive joining connection is created between the two workpieces.

In the case of abutting edge welding, on the other hand, two workpieces, of which at least one laser light absorbs, are compressed under the action of external forces and welded together along their common abutment edge.

If, by means of the device for welding plastic parts, a different three-dimensional contour than indicated here is to be welded, only the beam-shaping element has to be welded 2 be replaced by another beam forming body having the desired contouring. There is also the possibility that the exit aperture 23 has no contouring in the x direction, so that a two-dimensional weld contour is generated.

In this way, the device is very flexible and can be adapted quickly to changed two- or three-dimensional weld seam contours. In principle, any desired weld seams can be laser-welded simultaneously in the contour of the device shown here.

Claims (14)

Method for the simultaneous laser welding of at least two workpieces along at least one common weld, wherein by means of a laser device ( 1 a first intensity distribution of laser light is generated in a plane substantially perpendicular to the direction of propagation of the laser light, wherein the first intensity distribution is within one with an entrance aperture (FIG. 23 ) beam forming agent ( 2 ) is converted into a second intensity distribution, which is adapted to a contour of the weld, characterized in that the laser light is at least partially imaged in areas of the weld, which from the entrance aperture ( 23 ) of the beam shaping agent ( 2 ) are spaced such that a three-dimensional weld contour is generated. A method according to claim 1, characterized in that the laser light on the entrance aperture ( 22 ) on a first end face ( 20 ) of the beam shaping agent ( 2 ) by means of first lens means ( 3 ) is displayed. A method according to claim 2, characterized in that the laser light, the beam shaping means ( 2 ) through an exit aperture ( 23 ) on a second end face ( 21 ) of the beam-shaping body ( 2 ) leaving the shape of the exit aperture ( 23 ) of the shape of the entrance aperture ( 22 ) deviates. Method according to one of claims 1 to 3, characterized in that the laser light is imaged by means of at least one second lens means on the weld of the at least two workpieces. Device for the simultaneous laser welding of at least two workpieces, comprising at least one laser light source ( 1 ) for generating a first intensity distribution of laser light in a plane substantially perpendicular to the propagation direction of the laser light, the device comprising at least one beam shaping means ( 2 ) for converting the first intensity distribution into a second intensity distribution, wherein the beam shaping means ( 2 ) an entrance aperture ( 22 ) and a first, the entrance aperture ( 22 ) associated end face ( 20 ) as well as an exit aperture ( 23 ) and a second, the exit aperture ( 24 ) associated end face ( 21 ), characterized in that the second end face ( 21 ) of the beam shaping agent ( 2 ) a contouring offset in the propagation direction of the laser light to each other increases ( 210 ) and depressions ( 211 ), which are adapted to the contour of the weld. Device according to claim 5, characterized in that the shape of the exit aperture ( 23 ) of the shape of the entrance aperture ( 22 ) is different. Device according to claim 5 or 6, characterized in that the beam-shaping means ( 2 ) at least one beam guiding channel ( 26 ) for guiding the laser light within the beam-shaping means ( 2 ) having. Apparatus according to claim 7, characterized in that the beam guiding channel ( 26 ) at least one reflective coating ( 27 ) for the at least partial reflection of the laser light within the beam guiding means ( 2 ) having. Apparatus according to claim 8, characterized in that the reflection coating ( 27 ) is designed as a gold coating. Device according to one of claims 7 to 9, characterized in that the beam guiding channel ( 26 ) is hollow. Device according to one of claims 7 to 10, characterized in that the beam guiding channel is roughened for homogenizing the laser light. Device according to one of claims 5 to 11, characterized in that the laser device ( 1 ) has at least one laser diode bar. Device according to one of claims 6 to 12, characterized in that the device comprises first lens means ( 3 ) for imaging the laser light on the entrance aperture ( 22 ) having. Device according to one of claims 6 to 13, characterized in that the device comprises second lens means to the at the exit aperture ( 24 ) emit laser light onto the weld seam of the workpieces.

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