CA2176618A1

CA2176618A1 - Method and apparatus for joining workpieces together

Info

Publication number: CA2176618A1
Application number: CA 2176618
Authority: CA
Inventors: Hans Aebersold; Norbert Gross; Werner Urech
Original assignee: Elpatronic AG
Current assignee: Elpatronic AG
Priority date: 1995-05-15
Filing date: 1996-05-14
Publication date: 1996-11-16
Also published as: EP0743129A2; EP0743129A3; JPH08332583A

Abstract

In a method for joining workpieces together by welding by means of a welding energy source a plurality of workpieces are joined together in a plurality of welding stations, in succession, by a common welding energy source.

Description

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M~THOD ~D APPARATUS FOR JOINING WORKPIECES TO(~

The invention relates to a method for joining workpieces together by welding by means of a welding energy source in a welding station, and also to an apparatus for carrying out the method.
- Various welding processes are known for joining workpieces together, particularly for the fabrication of body components for motor vehicles. Especially worthy of note are mash roller seam welding, laser welding, etc.
For all welding processes, it is essential that the welding operation be conducted as economically as posRible. It is important to note that a specific time is required for the actual welding operation, since a specific rate of travel has to be maintained. In the present state of the art this lies somewhere below 15 m/min.
Furthermore, the workpieces which are to be joined together have to be positioned before welding can take place, and they have to be transported, loaded on carriers and unloaded from carriers, dressed, cooled, and subjected to quality inspection. These operations take up a considerable time, which is nonproductive time during which no welding can take place.
The object underlying the present invention is to develop a method and an apparatus of the abovementioned kind which allow two workpieces to be joined together in a more economical way and the productivity of the line to be increased through a reduction in nonproductive time.

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This object is achieved by using a common welding energy source to join together, in succession, a plurality of workpieces in a plurality of welding stations.
This means that several welding stations can be served by a single welding energy source, which is normally the most expensive part of the apparatus. This is known as duplex operation, in which those elements which are responsible for nonproductive time in single operation are multiplied. As a result costs can be reduced. It is also possible according to the invention, while a welding operation iæ taking place in one welding station, to remove workpieces which have already been joined together f~om another station in order to load that other station with new workpieces and to position those workpieces. All that then remains is to divert tne welding energy æou~ce to the newly supplied welding station in turn. As a result, very little time i9 lost.
In one way of carrying out the method according to the invention, the workpieces can be fixed and a welding beam, in particular a laser beam, traversed in relation to the workpieces to effect the welding. In the other way of carrying out the method, however, the welding energy source and the laser beam are fixed during welding and the workpieceæ are traversed with respect to the welding beam.
Obviously, the workpieces are secured during the welding operation, by means of suitable clamping tables, clamping elements or the like. Alternatively, roller conveyors with securing arrangements may be used.

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If a laser is used as the welding energy source, better possibilities may be obtained by the interposition of deflector devices into the laser beam. With the present state of laser technology, it can be arranged that the laser remains stationary, transmitting a beam always in one direction. Deflector devices can then be interposed into the path of the beam as required, to suit the positions of the welding stations, so as to deflect the beam to a focussing unit and to the welding station desired.
However, if the workpieces are to remain stationary during the welding operation, the possibility also exists of traversing the focussing units togeth~r with the deflector devices within the welding stations.
Possible deflector devices will normally be mirrors, but glass fibre cables can also be used.
There are also a large number of possible arrangements for the welding stations. They may be arranged in line or in parallel, or aligned in a sandwich arrangement. Moreover, the individual welding stations may be positioned at any desired angle in space with respect to each other.

The efficiency achievable by the present invention lies first of all in a duplication of the simpler components, minimising non-productive times for the costly welding energy source. The welding energy source can be permAne~tly utilized, which iB particularly important: at a given rate of travel (determined by the state of the art or other criteria), it is possible to achieve the maximum ~ 2176618 -production rate that can be attained by the use of a single welding energy source. It i9 also possible to cater for more than two welding stations with a single energy source.
Further advantages, features and particulars of the invention will become apparent from the following description of preferred embodiments given by way of example and with reference to the drawings, in which:
Fig. 1 is a diagrammatic side view of an apparatus according to the invention for joining two workpieces together;
Fig. 2 is a plan view of the apparatus according to Fig. 1;
Fig. 3 is a plan view of a further embodiment of an apparatus according to the invention;
Figs. 4 and 5 are diagrammatic views of further embodiments of an apparatus according to the invention;
Fig. 6 is a diagrammatic plan view of part of the apparatus shown in Fig. 2;
Fig. 7 is a cross-section through an apparatus according to the invention which uses a shuttle for welding several sheet-pairs;
Fig. 8 is a plan view of the apparatus shown in Fig. 8.
In an apparatus R according to the invention, two workpieces 1.1 and 1.2 (see Fig. 2) are to be joined together by laser welding. This apparatus R has feed units Fl and F2 on either side of a portal 2, and welding stations Sl and S2 inside the portal. The actual welding is 21 76~8 .

performed by means of a laser beam 3 produced by a laser 4.
In order that the laser beam 3 can be directed either to the welding station S1 or to the welding station S2, deflector devices 15.1 and 15.2 are provided in the laser beam 3, each able to deflect the la9er beam 3 from a horizontal direction to a vertical direction.
In this case the laser 4 i9 fixed and is located for example in the corner region of the portal 2. The laser 4 transmits a single laser beam towards the deflector devices 15.1 and 15.2. Focussing units 16.1 and 16.2 are associated with the deflector devices 15.1 and 15.2. When the deflector device 15.2 is interposed in the path ~f the laser beam 3, the focussing unit 16.2 is utilized. When the deflector device 15.2 is swung clear, the laser beam 3 is able to pass to the deflector device 15.1 whe~e it is deflected into the focussing unit 16.1. Both deflector devices 15.1 and 15.2 move together with their respective focussing units 16.1 and 16.2.
A discharge unit 5 is provided between the two welding stations S1 and S2 for transporting the workpieces 1.1 and 1.2 away, in the direction y, after they have been welded together to form a compound panel. The discharge unit 5 may for example have a corresponding roller conveyor 6 as indicated in Fig. 1.
Since the construction of the feed units F1 and F2 and the welding stations S1 and S2 is identical, only one example will now be described.
The feed unit F has a gripping manipulator 7 .

which is capable of traversing in the direction xl. The manipulator 7 has a horizontal slit 8 which is adjoined on both sides by receiving rollers 9. The workpieces 1.1 and 1.2 are laid on these receiving rollers 9 and are propelled towards one another and into the horizontal slit 8 by any desired mechanical handling means. They are then clamped in the horizontal slit 8 by means of any desired clamping elements.
The manipulator 7 is then traversed into the welding station S between two clamping tables 10.
Meanwhile the receiving rollers 9 remain in their position outside the portal 2.
The manipulator 7 then lays the workpieces 1.1 and 1.2 on the clamping tables 10 so that the workpieces 1.1 and 1.2 are each held between a clamping tab~e 10 and a pressure plate 11.1 and 11.2 respectively. These pressure plates 11 are subjected to pressure, which may be hydraulic, pneumatic or mechanical as desired, so that the workpieces 1.1 and 1.2 are fixed as securely as possible.
The clamping pressure acting on the workpieces 1.1 and 1.2 in the horizontal slit 8 is then released! and the manipulator 7 is traversed out of the welding station S
in the opposite direction to the direction x1. This exposes a butt joint (not shown) between the two workpieces 1.1 and 1.2, and the laser beam 3 is now guided along it, producing a welded seam and thus joining the two workpieces together.
The feed unit F is reloaded with workpieces while . 2176~18 .

the welding operation i8 being performed. When the feed unit F is then traversed into the welding station S, these further workpieces can expel the welded workpiece out of the welding station S and onto the discharge unit 5.
In a further embodiment of the invention shown in Fig. 3, clamping tables 10.1,10.2 and 10.3,10.4 are arranged to run parall`el with and alongside one another on corresponding rails 17.1 to 17.4. In this embodiment, the clamping tables 10.1 to 10.4 are traversable, while the laser 4 is stationary. The laser could also be made pivotable about an axis of rotation through a predetermined angle, in the preferred embodiment through an angle af 180, so that it can reach both the clamping tables 10.1,10.2 and the clamping tables 10.3,10.4, although with preRent-day industrial-type l~sers this i8 not r~alistic owing to their size and weight. In principle, it would also be possible to make the laser rotatable so that it could activate separate deflector devices provided on the left and on the right over the clamping tables 10.1,10.2 and 10.3,10.4, respectively. This embodiment should also be deemed to be included within the present invention, even though it cannot be realised with present-day lasers.
Fig. 3 shows instead how the laser beam 3 can be directed by a deflector device 15.3 ta prismatic mirror) to the left or to the right as desired, towards the focussing units 16.1 or 16.2. The focussing units 16.1 and 16.2 direct the beam 3 on to a butt joint 21 between the workpieces 1.1 and 1.2, which are welded together by the laser beam 3. The clamping tables 10.1 and 10.2 are traversed in the direction Y1 until the two workpieces 1.1 and 1.2 are joined together. The clamping tables are now close to an ejector unit 19.1, which is in the form of an industrial robot for example. As indicated in broken lines at top right, this bears against the rear edge of the welded workpieces and pushes them onto the discharge unit 5. The clamping tables 10.1 and 10.2, which are coupled together to be driven jointly, then travel back to a position as 5hown for the clamping tables 10.3 and 10.4.
Fig. 3 shows the clamping tables 10.3 and 10.4 in a loading position, in which workpieces 1.3 and 1.4 are pushed laterally on to the clamping tables so that they lie under the pressure plates 11.3 and 11.4. At the same time, it is possible to position the two workpiece~ 1.3 and 1.4, and in particular to apply edgewise pressure to close the butt joint between them.
While loading of the clamping tables 10.3 and 10.4 has been taking place, the laser beam 3 has joined the workpieces 1.1 and 1.2 together, in the position shown. On completion of this welding operation, the laser beam 3 is turned round, preferably through 180, into the position shown in broken lines, by which time the clamping tables 10.3 and 10.4 have traversed forwards ln the direction Y
so that the laser beam 3 can continue welding in this position. The workpieces 1.3 and 1.4 are then welded together, while the clamping tables 10.1 and 10.2 can be unloaded and reloaded. When the welding operation on the (-;

gworkpieces 1.3 and 1.4 is complete, the clamping tables 10.1 and 10.2 are once again in the position shown in Fig.
3 with newly loaded workpieces, 80 that the laser beam 3 i9 able, after having been turned round again through 180, to continue welding on the clamping tables 10.1 and 10.2.
The schematic illustration of an apparatus according to the invention in Fig. 4 iæ mainly intended to show that the siting of the laser 4 is completely independent of the location and arrangement of the welding 0 station, or of the workpieces. In this case an additional deflector device 15.1 is interposed in the laser beam path to one of the welding stations. Obviously, the workpieces are fixed on corresponding clamping tables.
The apparatus R4 shown in Fig. 5 differs from the forms cf apparatus shown in Figs. 1 to 4 in that a sandwich type arrangement has been set up. Here, the laser 4 is positioned between clamping tables 10.1 and 10.2 which are traversed horizontally. To weld the workpieces on the clamping tables 10.1 or 10.2 as the case may be, the laser beam 3 is deflected accordingly.
With the embodiments shown in Figs. 3 and 5, it is possible either to traverse the clamping tables in relation to the focussing units or to traverse the focussing units together with their deflector devices in relation to the clamping tables.
In Fig. 6 the two workpieces 1.1 and 1.2 are shown on corresponding clamping tables which together form a shuttle 22 on which a plurality of workpiece-pairs are 21 7~1 8 ;

transported through a welding station S, for example from a loading station to an unloading station. During transport, the workpieces are secured to the clamping tables 10.1 and 10.2 by the pressure plates 11.1 and 11.2.
In the welding station S, the workpieces 1.1 and 1.2 are first of all dressed in the region of the butt joint, as described in EP-A 0565846. A dressing unit to carry out this operation is indicated at 23.
The dressing unit 23 is followed by a gap monitor 24 whose main function is to check the line of the gap to be tracked by the laser beam 3.
After welding, it has proved advisable for the welded seam to be treated in a brushing unit 25. This is preferably followed by oiling, which also has the effect of cooling the weld seam. This treatment takes place in a cooling unit 26. This is followed by a quality inspection 27 and, if necessary, further-dressing in a post-dressing unit 28.
This set-up suggeQted schematically in Fig. 6 is illustrated more graphically in Figs. 7 and 8:
Fig. 7 shows a cross-section through a machine with the functions illustrated in Fig. 6.
A plan view of the machine illustrated in Fig. 7 is shown in Fig. 8.
Fig. 7 shows a cross-section through an apparatus for carrying out the invention. The drawing shows a machine frame 16.1,30, with limbs of the part 16.1 of the frame specifically designated 10.1 and 10.2. A clamping 2 1 ~

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table or shuttle 20 runs on the frame 16.1,30, and is supported thereon by C-shaped elements 20.1,20.2,29.1,29.2.
Magnets 23 form the supporting surface for the sheets 1.1 and 1.2. Press shoes 25, preferably of ferromagnetic material, are pressed against the sheets 1.1,1.2 by pressure elements 27. The pressure due to the pressure elements 27 combines with that of the magnets 23 with more than proportionate effect, with the result that the arrangement is able to sustain more than proportionately greater lateral forces. Dissipation of heat due to the welding in the joint 3 is assisted by the cooling ducts 24.1 and 24.2.
From Fig. 8 it can be seen that the shuttle, of which only the two yokes 29.1 and 29.2 are visible, runs the whole length of the apparatus. At present it is in a loading station F, from which it passes to a welding station S, and thence to an unloading station E from which the welded workpieces are removed.
In the welding station, the butt joint is preferably dressed by a dressing unit 31 as described in EP-A 565846. The dressing unit 31 is preferably followed by a gap monitor 32 allowing a laser beam 2 located next along the machine to track the line of the gap.
After the butt joint has been welded by the laser 33, the weld seam is preferably treated in a brushing unit 34 and oiled in a cooling station 35. These treatments are followed by a quality inspection 36 and, if necessary, further dressing 37.

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The workpieces 1.1 and 1.2 pass through all these treatments while clamped to the shuttle.

Claims

1. Method for joining workpieces (1) together by welding by means of a welding energy source (4) in a welding station (S), characterised in that a plurality of workpieces (1.1-1.4) are joined together in a plurality of welding stations (S1,S2), in succession, by a common welding energy source (4).

2. Method according to claim 1, characterised in that a welding operation is performed in the welding station operatively linked with the welding energy source and, at the same time, one or more of the joining operations which precede or follow the welding operation is performed in at least one other welding station, such as:
loading said other welding station with workpieces, fixing said workpieces in readiness for the welding operation, edge preparation by plastic deformation, brushing and oiling, or discharge of the welded workpieces from the welding station.

3. Method according to claim 1, characterised in that a laser (4) transmitting a laser beam (3) is used as the welding unit.

4. Method according to claim 3, characterised in that the laser beam (3) is deflected to the individual welding stations (S1,S2) by deflector devices (15), and is converged in focussing units (16).

5. Method according to claim 4, characterised in that the deflector devices (15.1,15.2) are displaced into the path of the laser beam (3) while the laser (4) remains stationary.

6. Method according to claim 4 or 5, characterised in that the focussing units (16) are moved together with the deflector devices (15.1,15.2) in the welding stations (S1, S2), while the workpieces (1.1-1.4) remain fixed.

7. Method according to claim 4 or 5, characterised in that the workpieces (1.1-1.4) are traversed in relation to stationary focussing units (16).

8. Apparatus for welding metal sheets into compound panels including the steps of:
- using at least one welding energy source with a plurality of welding stations operatively linkable with the welding energy source, the number of welding stations being greater than the number of welding energy sources, and - joining the metal sheets together.

9. Apparatus according to claim 8, characterised in that a laser unit and deflector devices for its laser beam are provided as the welding energy source, in such a way that the laser beam can be selectively directed to a laser welding lens system of an individual welding station to perform a welding operation there.

10. Apparatus according to claim 8 or 9, characterised in that each welding station has elements for fixing the sheets to be welded and elements for relative motion between the sheets to be welded and the laser welding lens system and also preferably elements for edge preparation of the sheets by plastic deformation.

11. Apparatus according to claim 10, characterised in that the element for relative motion is in the form of a shuttle which carries the fixing elements and which can be traversed forwards and backwards between a loading area and an unloading area of the welding station, the laser welding lens system being stationary between the loading and unloading areas.

12. Apparatus according to claim 10, characterised in that the element for relative motion is in the form of a traversable laser welding lens system which is operatively traversable forwards and backwards over the fixing element which is in the form of a clamping table.

13. Apparatus according to claim 10, characterised in that the element for fixing the sheets to be welded has securing elements for a plurality of sheet-pairs, these securing elements preferably comprising pressure elements and magnets cooperating therewith.