DE102010007717A1 - Connecting two workpieces using transmission welding, comprises contacting both workpieces over a contact area extending in x-y direction, where the contact area has a joining area, and directing a laser line to the joining area - Google Patents

Abstract

The method for connecting two workpieces (1, 2) using transmission welding, comprises contacting both workpieces over a contact area (10) extending in x-y direction, where the contact area has a joining area (3), and directing a laser line having certain width and extending in the x-y direction to the joining area, which is formed from line sections having equal lengths, where the lie sections and the joining area are completely illuminated by a laser beam bundle from a laser source, and moving the laser line relative to the joining area with a relative velocity in y-direction. The method for connecting two workpieces (1, 2) using transmission welding, comprises contacting both workpieces over a contact area (10) extending in x-y direction, where the contact area has a joining area (3), and directing a laser line having certain width and extending in the x-y direction to the joining area, which is formed from line sections having equal lengths, where the lie sections and the joining area are completely illuminated by a laser beam bundle from a laser source, moving the laser line relative to the joining area with a relative velocity in y-direction, and welding both workpieces with one another over the entire joining area. The contact area is defined as a strip matrix (31) extending in the x-y direction, where the strip matrix is formed from strips with a strip width in x-direction equal to the length of the line sections. The contact area is defined as an arrangement of strip elements (32) assigned to the strips, where the strip elements are detected and stored with respect to their positions and strip elongations in y-direction. The line sections are individually illuminated under the use of the stored data and the relative velocity to illuminate the strip elements of the strips with the laser beam bundle. The control of the laser beam bundle of the associated laser source takes place over a controller, so that the laser source is switched on when the line sections caused by it completely lie inside the strip elements in y-direction and remains switched-on so long as the line sections caused by it completely lie inside the strip elements in y-direction. The laser beam bundle of each laser source is formed, so that the distribution of the power of the laser beam bundle in each line sections corresponds to a top-hat distribution. The laser line is formed in a broken manner, where the disruptions are distributed over the length of the laser line in a regular or irregular manner and in same and different lengths. An independent claim is included for a device for connecting two workpieces using transmission welding.

Description

The invention relates to a method and apparatus for connecting materials by means of transmission welding, wherein structured joining areas can be connected to one another with a high spatial resolution, as generically described in US Pat EP 0 997 261 B9 is described.

In order to carry out the through-beam welding, two workpieces to be joined together are folded together so that they touch each other directly along a contact region. Within the contact area lies the joining area. A first workpiece is transmissive to laser beams and faces a laser source. The second workpiece is absorbing for the laser beams. The laser beams penetrate the first transmitting workpiece, hit the upper layers of the second workpiece, are absorbed there and converted into heat energy. The upper layers of the second workpiece melt, whereby by thermal conduction also to a melting of the adjacent layers of the first workpiece and a cohesive connection of both materials of the workpieces comes.

If both workpieces are to be connected to one another along a joining region, which has different dimensions over its extent, that is, the impact of the laser beams on the regions of the structured joining region must be limited in order to prevent welding of other regions within the contact region.

One possibility for this is the use of a point or line focused on the joining region of two workpieces laser beam, as in the EP 1 405 713 B1 is described. A laser lens focusing, designed as a roller or ball and placed on the surface of the transmitting workpiece optical lens is moved synchronously with the laser beam over the joint area. The workpieces to be welded are locally compressed by the lens. With the implementation of the disclosures of EP 1 405 713 B1, workpieces can be connected to one another precisely over structured joining areas, although the connection of larger areas is very time-consuming.

In the EP 997 261 B9 discloses a method in which two workpieces are connected by means of transmission welding together in a structured joining region.

In this case, the free surface of the transmitting workpiece is covered by a laserlichtundurchlässigen mask and the mask by laser beams (hereinafter laser beam called) applied in the form of a laser curtain, which is generated by collimation and focusing of laser beams of one or more laser sources. The mask is perforated corresponding to the structured joint area, so that those areas of the joint area are shaded, which should not be connected to each other. The shadowed by the mask laser beams are reflected.

The laser beams impinge in a laser line on the surface of the absorbing workpiece, the laser line being subdivided into line segments by the design of the mask. If the mask has been perforated corresponding to a line segment, the line segment is illuminated with the full power of the laser beams; if the mask is not broken, the respective line segment remains unlit. Workpieces and laser line are moved relative to each other, whereby the laser line is guided over the joint area. The laser line is constantly adapted to the extent of the swept over at a time joining area. The extension of the laser curtain, and thus the maximum extension of the laser line, can be adjusted by changing the working distance of the laser source and the mask. In addition, the energy density of the laser line can be adjusted by changing the power of the laser beam.

A disadvantage of such a solution is the need for the cost-intensive production of workpiece-specific masks. An immediate correction or readjustment in an ongoing manufacturing process is therefore not possible.

A change in the structuring of the joining area requires the preparation and use of a new mask. This usually has to be re-applied and positioned at every workpiece pair to be connected.

It is also energetically unfavorable that a portion of the emitted laser beam is not used and also more or less diffusely reflected, which means an increased material load on the device and additional occupational safety measures required.

Furthermore, no solution is known by means of which the distribution of the power density along a laser line can be controlled, except that sections of the laser line are illuminated in the sense of a binary control, either not or at full power. A change in the power parameters of the laser beam always has the same effect on several or all Line segments of the laser line off. A section-wise adjustment of the service is not known.

The invention has for its object to provide a way to connect workpieces by Durchstrahlschweißens along freely selectable structured joining areas without the use of a mask. It is also an object of the invention to show a possibility of how the incident on a line section of a laser line power of the laser beam can be adjusted in sections.

In the following, laser sources are understood as meaning all technical devices emitting a laser beam, independently of whether the laser beam is generated and emitted directly in these devices or the laser beam is conducted away from an emitter and indirectly emitted by these devices. Indirect emitters may be, for example, arrangements of optical waveguides.

The object is achieved by means of a method for joining two workpieces by means of transmission welding, wherein the two workpieces touch each other over a contact area extended in the xy direction, which comprises at least one joining area in which a laser line of a certain width extended in the x direction points towards the joining area is formed of a plurality of line sections of equal length, each by a laser beam, each coming from a laser source, illuminated, the laser line is moved relative to the joining region at a relative speed in the y-direction, whereby the joining region through the laser beam completely is illuminated and the two workpieces are welded together over the entire joining area, achieved by the contact area is defined as a striped strip matrix in the xy direction, formed from strips with a strip width in the x direction equal to the Length of the line sections that the joining area is defined as an array of strip elements associated with a strip, which are detected and stored with respect to their position and stripe extent in the y direction and the line sections are individually illuminated using the stored data and the known relative speed to illuminate each of the strip elements of a strip with a laser beam.

The core of the method according to the invention is formed by virtue of the virtual division of the contact region into a strip matrix with strip elements corresponding to a joining region and by generating a laser line which is composed in sections of line sections and which can be actively adjusted in sections as regards the power of the laser beam illuminating a strip element.

An active setting is understood to be control-technical measures that can be carried out in a targeted manner by means of corresponding control commands. Passive settings, on the other hand, are those that can not be achieved by control measures. By passive measures in this sense is meant the mere use of shading means, such as the masks mentioned above.

The position of each virtual strip element in a strip and its extension in the direction of the strip (stripe extent) can be chosen freely.

The division of the contact area is carried out according to a rule, which is provided for example as a program.

Those virtual strip elements over which a connection is to be made are each assigned a value that identifies them as belonging to the joining area.

The data on the position and extent of contact area and joining area are repeatedly retrievable and stored in a form suitable for analysis.

The laser line has a length in the x direction and a width in the y direction. The length of the laser line is preferably not less than the extension of the joining region in the x direction.

The position and length of the laser line as well as the position and extent of the joining area swept by the laser line at this time are known at all times. This information is compared with each other and form the basis of the control of the laser sources, the means for generating the relative movement and any other means necessary for carrying out the method according to the invention.

Alignment of the laser beams is accomplished using known beamforming optical means. When laser sources are used whose laser beams are emitted along the different dimensions of the aperture of the laser sources on different axes and with different divergence angles, it is a preferred embodiment when the laser beams of all axes are brought together and collimated.

Advantageously, by a collimated, so parallel aligned, beam guidance is achieved that those regions of the joining region, which are in other embodiments of the invention, although perpendicular to the propagation direction of the laser beam, but along the z-axis in different xy planes, with the same energy are applied.

A parallel beam guidance therefore makes it possible to dispense with focusing the laser beam for generating the laser line. In further embodiments of the invention, however, a focus may be provided and appropriate technical means may be present.

In each line segment of the laser line, the distribution of the power of the laser beam follows a normal distribution, which however can be modified by the properties of the optical means used. In particular, it is advantageous if the distribution of the power approaches both the length and the width of a line segment of a top hat distribution (rectangular distribution), which has steep rises and a plateau-shaped course of the amplitude. Such a distribution of the power within the sections of the laser line ensures a sharp-cut mutual delimitation of the line sections and their uniform illumination.

According to the invention, it is possible to set the power of the emitted laser beams of each individual laser source individually via a drive. The power of the laser beams is controlled by adjusting the electrical power consumption of the individual laser sources. The range in which the power of the laser beam can be adjusted is determined by the technical characteristics of the respective laser source and ranges from zero power to the maximum possible power of the laser source in question.

In particular, when using laser diodes as laser sources, it is advantageous if the laser beam propagating along the so-called "fast axis" are collimated by suitable optical means. Preferably, the laser beams are each arranged so that the collimated laser beams of the fast axis determine the width of the laser line.

The laser line can be formed interrupted, the interruptions can be the same or different lengths and regularly or irregularly distributed over the length of the laser line.

An individual adjustment of the power of the laser beam is always active. It is useful, for example, if the permeability of the transmitting workpiece varies due to its surface design or manufacturing reasons.

The achievable spatial resolution of the welded joint to be created along the joint area mainly depends on the dimensions of the line segments of the laser line. If laser sources are used with small dimensions, z. As optical fibers, the line sections of the laser line can be kept small and thereby high resolution can be achieved. In addition, the resolution can be increased if a plurality of laser lines are arranged and their line segments overlap in the x-axis direction by a certain amount. The amount of overlap can be adjustable in further embodiments.

An adjustment of the power of the laser beams per line section can be achieved in two advantageous ways. On the one hand, the power of each laser source can be adjusted individually by means of a suitable control from a value equal to zero to the maximum power of the laser source.

In a further advantageous embodiment, the laser sources remain in the on state. It is advantageous if the laser sources can also be individually controlled with respect to their emitted power. In order to illuminate portions of the laser line with a power of zero, the respective laser beams are prevented by engaging in the beam path of the laser beam means to illumination of their associated strip. The advantage of this design lies in the reduction of unfavorable control effects, as they can occur by a rapid and repeated change in the power consumption of electrical components.

If a relative movement takes place between the joining region on the one hand and the laser line on the other hand, the information about the relative position of the joining region and laser line, the relative velocity and the expansion of the joining region are compared continuously or at time intervals and / or after a certain amount of relative movement has been covered. The relative position can also be detected and controlled by means of the detection of the position of existing at least one workpiece marks and / or significant changes in property of the workpieces by means of known optical and / or tactile methods.

The object is further achieved by a first device for connecting two workpieces by means of transmission welding, wherein the two workpieces on one, in the xy direction contact extended contact area, which comprises at least one joining region, wherein a plurality of laser beams each emitting a laser beam and optical means are present, which collimate the laser beams in the y-direction and arranged to each other so that they line sections of equal length along an x-direction expands Laser line can illuminate on the contact area, further comprising a support for receiving the workpieces and a drive for generating a relative movement between the carrier and laser sources are achieved in that a drive is present, which is connected to each laser source and the laser sources by means of the control are individually controllable, that a memory is present, which is connected to the drive and which is adapted to a joining area within the contact area as an array of strip elements, each of a strip with a stripe width in x-Richtun g are equal to the length of the line sections associated with a strip matrix, with their position and extent in the y direction, store and that the drive is designed so that they the laser sources, each associated with a strip, using the stored data and the known relative speed so controls that each of the strip elements of a strip are acted upon by a laser beam of a laser source.

All systems which can be used to store the contact area and the joining area virtually in terms of their position and extent in strip elements of a strip matrix can be used as memory, and this information can be repeatedly retrievably stored and analyzed.

Laser sources may be, for example, laser diodes, Nd: YAG lasers or any other suitable laser.

It is also possible to provide laser sources by so-called coupled modules, that is to say by optical waveguides, such as optical fibers or fiber bundles, which are connected to at least one emitter.

Each individual laser source is connected to a central control and can be individually controlled by it with regard to the power of the laser beam emitted by them. This is done by means of a suitable electrical and / or electronic circuit.

In further embodiments, additional optical means may be present, by means of which the laser beams can be arranged relative to each other and focused on the laser line.

The laser sources are preferably arranged linearly (line array) in the direction of the x-axis, wherein a plurality of line arrays may be present, which may be arranged offset in relation to one another in the direction of the x and y axes by an amount. The dimensions and / or performance characteristics of the individual laser sources of the line arrays can be different within and between them.

The laser sources may also be in other arrangements with each other, as long as it is ensured that their laser beams are arranged so that they illuminate the line sections of the laser line.

The object is further achieved by a second device in which, in addition to the features mentioned for the first device each laser source is associated with a deflection by which the laser beam of a laser source can be prevented from illuminating the associated line section and a control is present, the is connected to each deflection and the deflection is controlled individually by means of the control.

Deflection devices in the above-mentioned sense can be, for example, reflective, beam-guiding and / or absorbing means. If reflective means are used, it is extremely advantageous if the reflected laser beams are directed so that they pose no danger.

The workpieces are held during the welding process in a clamping device which has a drive for movement in the x-y plane. The drive is connected to the drive in a signal-conducting manner.

In addition to fixing the position of the workpieces, it is the task of the clamping devices to press the workpieces together, at least in the area of the welding process, in order to ensure a good connection of the melted areas of both workpieces.

The invention will be explained in more detail with reference to embodiments and drawings. The drawings show:

1 a schematic representation of workpieces with structured joining area and laser sources,

2 a perspective view of a device according to the invention, according to a first embodiment,

3 a partial perspective view of an embodiment of the invention, according to a second embodiment.

In the illustration according to 1 are as essential elements for laser radiation transmitting first workpiece 1 and a laser beam absorbing second workpiece 2 , a line array 8th with laser sources 8a to 8h as well as an activation 14 and a memory 15 available.

The two workpieces 1 and 2 touch each other in a contact area 10 , the virtual in a strip matrix 31 with parallel in the y-direction and equally spaced strips 31a to 31h is divided. The contact area 10 includes a joining area 3 (hatched), to its location and stripe extent in each stripe 31a to 31h corresponding strip elements 32 available. Each of the laser sources 8a to 8h of the line array 8th is with the control 14 and this in turn is with the memory 15 connected. Through the store 15 All information required for carrying out the method is repeatedly retrievably stored and the control 14 made available. The joining area 3 is from a joint-free area 4 crossed over the extent of which no illumination takes place.

In the store 15 are also information about the virtual division of the contact area 10 in the form of a strip matrix 31 and the strip elements contained therein 32 and information about the stripe extent of the joint area 3 stored. Furthermore, there are control 14 and a, a relative movement between the first and second workpiece 1 and 2 on the one hand and the laser line 11 on the other hand, effecting drive 13 with each other in such a connection that information about the relative position of the first and second workpieces 1 and 2 and the laser line 11 exchanged, with the corresponding to a respective relative position expansion of the joining region 3 can be compared and, if appropriate, the relative movement can be influenced.

The of the laser sources 8a to 8h of the line array 8th in the direction of the joining area 3 transmitted laser beam 12 cause a laser line there 11 , which in the direction of the x-axis of equal-sized line segments 11a to 11h is composed. Every laser source 8a to 8h causes exactly one line section 11a to 11h , The length of each line segment 11a to 11h is equal to the width of the stripes 31a to 31h and the location of the line sections 11a to 11h corresponds to the location of the stripes 31a to 31h so every strip 31a to 31h exactly one line section 11a to 11h is assigned, each by an associated laser source 8a to 8h is effected.

In further embodiments, further line arrays may be present, which may also contain other numbers of laser sources (not shown) and which may be displaceable parallel to the xy plane. For each additional line array, another strip matrix is defined according to the conditions described above. Each further line array is controlled by the driver 14 controlled according to the respective further strip matrix. The laser sources can also be arranged in a planar array, whereby the formation of a laser line is adjusted by means of correspondingly controlled laser sources of the array.

The laser sources 8a to 8h of the line array 8th and / or other line arrays can be described further in terms of their dimensions and performance both between and within individual line arrays 8th differ. Furthermore, the line arrays can be adjusted to a working direction at freely selectable angles 7 stand or be stopped.

The fixed in their position to each other workpieces 1 and 2 become with a relative movement, having a known relative speed to the line array 8th in the working direction 7 , guided. The laser sources sweep over 8a to 8h and with them the laser line 11 , the respective strips 31a to 31h and are doing so by the control 14 controlled that a line section 11a to 11h is illuminated exactly when this with its entire surface a strip element 32 covered. Shown is the lighting of the strip elements 32 the stripe 31a . 31b . 31g and 31h by laser beam 12 the laser source 8a . 8b . 8g and 8h in the line sections 11a . 11b . 11g and 11h , All other line sections 11c to 11f are unlit at the time shown.

When passing over a number of contiguous strip elements 32 or of strip elements 32 whose strip extension in y-direction is greater than the width of the laser line 11 is, every laser source becomes 8a to 8h through the control 14 then turned on when the line section caused by it 11a to 11h completely within a strip element 32 to lie in the y-direction. It stays on as long as the line section it causes 11a to 11h completely within a strip element 32 to lie in the y-direction. The relevant strip element 32 is at the relative speed continuously through its associated line section 11a to 11h the laser line 11 painted over. In the y-direction, therefore, the spatial distribution of the on the strip element 32 incident power as a top hat distribution: when the laser source is turned on, the line segment becomes one 11a to 11h covered area of the strip element 32 with a Power distributed according to the top hat distribution in the y direction. With progressive relative movement and continuous exposure to the laser beam 12 becomes the top hat distributed power of the respective line segment 11a to 11h along the strip element 32 associated strip 31a to 31h shifted and it comes to a resulting power entry, which at any time and for each point of the strip element 32 can be described by the successive overlays of the shifted top hat distributed power. Determining factors are the concrete mathematical function of the top-hat distribution, the amount of relative velocity and the width of the laser line 11 ,

The line array 8th can be formed in particular as a laser diode bar or laser diode array and by arrangements of optical waveguides. Fiber optic cables are used, several of them by only one emission source with laser beams 12 are supplied, so optical, electrical, electronic, mechanical measures or combinations thereof are provided, the controlled emission of laser beams 12 through the individual laser sources 8a to 8h enable.

In a first embodiment according to 2 is the line array 8th present, for the sake of clarity, only the laser sources 8a to 8d are shown in the form of four laser diodes of the same size and with the same performance parameters. In front of the laser sources 8a to 8d is a cylindrical lens 9 arranged, through which the emitted laser beam 12 collimated and on the joint area 3 be directed. The workpieces 1 and 2 be on a carrier 5 held, which is designed so that on it the two workpieces 1 and 2 are positioned parallel to an xy plane. A tensioning device 6 is arranged such that first and second workpiece 1 and 2 be pressed through each other. The carrier 5 is with a drive 13 connected and by this in the working direction 7 movable.

In a further embodiment, the carrier 5 also be designed to be movable in the direction of the x-axis and / or the z-axis.

The contact area 10 is traversed in the y direction by a depression in the form of an angled channel, the areas of the strips 31b and 31c pervades. The Stripes 31a and 31d and the areas of the strips not crossed by the depression 31b and 31c form the joining area 3 , The areas of the depression provide the joint-free area 4 represents.

It is also possible that the joint-free area 4 also one in the first workpiece 1 in-reaching survey of the second workpiece 2 , an area lying in the xy plane or a combination of these possibilities.

The time shown by the laser sources 8a . 8b and 8d at a divergence angle of 40 ° along the fast axis emitted laser beam 12 be through the cylinder lens 9 collimated and on by stripe elements 32 in stripes 31a to 31d Virtually illustrated joint area 3 directed. The line section remains 11c unlit. To the by the adjustments of the achievements of the laser sources 8a to 8d The change in electrical parameters such as voltage drops compensated in such a way that the welding process remains unaffected is indicated by the control 14 an integrated bypass circuit (not shown).

Further embodiments of the method according to the invention can be used for other technical possibilities to compensate for voltage and current fluctuations and to compensate for other adverse effects.

In a further embodiment of the invention, those of the as a laser source 8a to 8d used laser diode bundles laser beam 12 the slow axis not collimated and rather used to possible differences in the power densities of the individual line sections 11a to 11h a laser line 11 to decrease in the direction of the x-axis. Spreads a laser beam 12 unchecked, ie not collimated, along the slow axis, is determined by each laser source 8a to 8d a line section 11a to 11d imaged, which is sharply defined in the direction of the fast axis, but longitudinally oval and larger than the exit opening of the laser source in the direction of the slow axis 8a to 8d is. The power density of the laser beam 12 is approximately normally distributed at least in the direction of the x-axis. Along the laser line 11 For example, the increases in the power density distribution in the x-axis direction will be at least partially due to rising regions of an adjacent line segment 11a to 11d superimposed and summarily increased. Therefore, it lies above the entire laser line 11 a more homogeneous distribution of power density than that obtained by considering the non-superposed distribution in each individual line segment 11a to 11d would result.

The disadvantage here is that portions of the laser beam 12 on joint-free areas 4 can hit. However, this disadvantage can be achieved by adjusting the emitted power of individual laser sources 8a to 8d be reduced.

In the embodiment shown above according to 2 In addition, an arrangement of deflection devices 16 (only two deflectors 16 represented in the form of micromirrors), as they are in 3 is shown. These are arranged so that through them in the beam path of the laser beam 12 can be intervened. They are powered by a mirror drive 17 operated, which with the control 14 connected is. One of the diverters 16 exemplifies the beam path of the laser source 8c and directs the laser beam over the length of their engagement 12 as a reflected laser beam 18 in a laser trap 19 , The line section 11c the laser line 11 is therefore not illuminated.

In further embodiments, the deflection can 16 any optical, electro-optic or opto-mechanical components of appropriate dimensions, controllability and optical properties. As a deflection 16 For example, (micro) lenses or reflective, beam-shaping and / or absorbing components can be used.

The inventive method allows the precise connection of individual workpieces 1 and 2 , but also of endless materials with at the same time free and at any time possible adjustment of the laser line 11 to the extent of a joining area 3 , This can also workpieces 1 and 2 with arbitrarily structured joining area 3 be connected with high precision of the achieved welding. At the same time, the possibility is created of being able to intervene in current production processes without having to interrupt the process. The invention can be used in all areas in which the transmission welding is used. In particular, it can be used for the production of components in microfluidics.

LIST OF REFERENCE NUMBERS

1

first workpiece

2

second workpiece

3

joining area

31

striped array

31a to 31h

strip

32

strip element

4

joint-free area

5

carrier

6

jig

7

working direction

8th

line array

8a to 8h

laser sources

9

cylindrical lens

10

contact area

11

laser line

11a to 11h

line segments

12

laser beam

13

drive

14

control

15

Storage

16

deflecting

17

mirror drive

18

reflected laser beam

19

laser trap

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0997261 B9 [0001]
• EP 1405713 B1 [0004]
• EP 997261 B9 [0005]

Claims (9)

Method for joining two workpieces ( 1 . 2 ) by means of transmission welding, wherein the two workpieces ( 1 . 2 ) over a contact area extended in the xy direction ( 10 ) touching at least one joining area ( 3 ), in which an x-directionally extended laser line ( 11 ) of certain width on the joint area ( 3 ), which consists of a plurality of line sections ( 11a to 11h ) of equal length formed, each by a laser beam ( 12 ), each from a laser source ( 8a to 8h ), be lit, the laser line ( 11 ) with a relative velocity in the y-direction relative to the joining region ( 3 ), whereby the joining area ( 3 ) through the laser beams ( 12 ) is completely illuminated and the two workpieces ( 1 . 2 ) over the entire joining area ( 3 ) are welded together, characterized in that - the contact area ( 10 ) as a stripe matrix extended in the xy direction ( 31 ) defined by strips ( 31a to 31h ) with a strip width in the x-direction equal to the length of the line segments ( 11a to 11h ), - the joining area ( 3 ) as an arrangement of one strip each ( 31a to 31h ) associated strip elements ( 32 ), which are recorded and stored with regard to their position and their strip extent in the y-direction, and - the line segments ( 11a to 11h ) are individually illuminated using the stored data and the known relative speed to respectively scan the stripe elements ( 32 ) of a strip ( 31a to 31h ) with a laser beam ( 12 ) to illuminate. Method according to Claim 1, characterized in that the control of the laser beam ( 12 ) of the respectively associated laser source ( 8a to 8h ) via a control ( 14 ) is carried out so that then a laser source ( 8a to 8h ) is turned on when the line segment ( 11a to 11h ) completely within a strip element ( 32 ) in the y-direction and remains switched on as long as the line section ( 11a to 11h ) completely within a strip element ( 32 ) comes to lie in the y-direction. Method according to claim 1, characterized in that the laser beam ( 12 ) of each laser source ( 8a to 8h ) is shaped so that the distribution of the power of the laser beam ( 12 ) in each line segment ( 11a to 11h ) corresponds to a top hat distribution. Method according to one of the preceding claims, characterized in that the laser line ( 11 ) is interrupted, wherein the interruptions equal or different lengths and regular or irregular over the length of the laser line ( 11 ) can be distributed. Device for connecting two workpieces ( 1 . 2 ) by means of transmission welding, wherein the two workpieces ( 1 . 2 ) over a contact area extended in the xy direction ( 10 ) touching at least one joining area ( 3 ), wherein several each one laser beam ( 12 ) emitting laser sources ( 8a to 8h ) and optical means are present, which the laser beam ( 12 ) in the y-direction and arrange them in such a way that they form line sections ( 11a to 11h ) of equal length along an x-directional laser line ( 11 ) on the contact area ( 10 ), and a support ( 5 ) for receiving the workpieces ( 1 . 2 ) and a drive ( 13 ) for generating a relative movement between carriers ( 5 ) and laser sources ( 8a to 8h ) are present, characterized in that - a control ( 14 ) is present with each laser source ( 8a to 8h ) and the laser sources ( 8a to 8h ) by means of the control ( 14 ) are individually controllable, - a memory ( 15 ) is present, with the control ( 14 ) and which is adapted to a joint area ( 3 ) within the contact area ( 10 ) as an array of strip elements ( 32 ), each one strip ( 31a to 31h ) with a strip width in the x-direction equal to the length of the line segments ( 11a to 11h ) a strip matrix ( 31 ), with their location and extent in the y-direction, store and - the control ( 14 ) is designed so that it the laser sources ( 8a to 8h ), one strip each ( 31a to 31h ), using the stored data and the known relative speed so that each of the strip elements ( 32 ) of a strip ( 31a to 31h ) by a laser beam ( 12 ) a laser source ( 8a to 8h ). Apparatus according to claim 4 or 5, characterized in that the laser sources ( 8a to 8h ) in a line array ( 8th ) are arranged. Apparatus according to claim 4 or 5, characterized in that a plurality of line arrays are present. Apparatus according to claim 6 or 7, characterized in that at least one line array ( 8th ) is displaceable parallel to the xy-plane. Device according to one of claims 5 to 8, characterized in that the control ( 14 ) includes a bypass circuit.

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