Apparatus for Joining, in Particular Laser Welding, two Components, and Operating Method for such a Joining Apparatus

Abstract

An apparatus for joining, in particular laser welding, two components, in particular plastics components, comprisestwo workpiece receptacles (1, 3) for respectively holding the two components (2, 4) to be connected, in each case one bearing element, preferably a bearing plate (7), for each of the workpiece receptacles (1, 3), a clamping drive (SA) for at least one bearing element for feeding and bracing of the two components (2, 4) held in the workpiece receptacles (1, 3) during the joining process, a controller (9) for the clamping drive (SA) and in particular a laser welding device (LS), anda mechanically loose coupling between the clamping drive (SA) and bearing element (7) such that the two workpiece receptacles (1, 3) are tiltable towards one another during feeding and bracing. Also disclosed is a method for operating such a joining apparatus during a joining process of two components (2, 4) held in the workpiece receptacles (1, 3), in particular during a laser welding process.

Claims

1-13. (canceled)

14. An apparatus for joining two components, in particular for laser welding two plastic components, comprising two workpiece holders for respectively holding the two components to be connected, respectively a bearing element, preferably a bearing plate, for each of the workpiece holders, a clamping drive for at least one bearing element for feeding and bracing the two components held in the workpiece holders during the joining process, and a controller for the clamping drive and a laser welding device, comprising a mechanically loose coupling between the clamping drive and the bearing element, such that the two workpiece holders can be tilted with respect to one another during the feeding and bracing.

15. The apparatus as claimed in claim 14, wherein the coupling between the clamping drive and the bearing element is a floating bearing.

16. The apparatus as claimed in claim 14, wherein the clamping drive comprises a plurality of linear drive elements arranged and acting parallel in the feed direction, on which the bearing element, configured as a bearing plate, of one workpiece holder is mounted in a floating fashion.

17. The apparatus as claimed in claim 16, wherein the linear drive elements are linear servo drives.

18. The apparatus as claimed in claim 16, wherein the linear drive elements comprise at least one of the group comprising position acquisition and drive force detection.

19. The apparatus as claimed in claim 18, wherein the linear drive elements can be driven individually by the controller according to the values recorded by at least one of the group comprising the position acquisition and the drive force detection.

20. A method for operating a joining apparatus in which the clamping drive comprises a plurality of linear drive elements arranged and acting parallel in the feed direction, on which the bearing element, configured as a bearing plate, of one workpiece holder is mounted in a floating fashion, during a process of joining two components held in the workpiece holders, in particular during a laser welding process, comprising the following method steps: feeding at least one of the bearing elements with the aid of the linear drive elements until contact of the two components to be joined, according to a predefined system setpoint value the workpiece holders being adjusted into a corresponding position with respect to one another, establishing the contact position as a reference position, during the joining process further driving of the linear drive elements starting from the reference position according to at least one predefined system parameter until reaching a target criterion for the system parameter, and ending the joining process after reaching the target criterion.

21. The method as claimed in claim 20, wherein the predefined system setpoint value is a clamping force setpoint value of at least one of the linear drive elements.

22. The method as claimed in claim 20, wherein the at least one predefined system parameter is at least one of the group comprising a predefined clamping force and a predefined joining displacement of the linear drive elements.

23. The method as claimed in claim 20, wherein for each linear drive element, the same or different predefined clamping force setpoint values are used as a system setpoint value for establishing the reference position.

24. The method as claimed in claim 20, wherein the linear drive elements are regulated individually by the controller to a predefined clamping force during the joining process.

25. The method as claimed in claim 24, wherein the predefined clamping force of the individual linear drive elements is adjusted in such a way that all linear drive elements simultaneously reach an individual switch-off criterion applying to them.

26. The method as claimed in claim 20, wherein during the joining process, the linear drive element applying the highest clamping force specifies, with a joining displacement, the joining displacement of the further linear drive elements one of the group comprising directly and by a setpoint variation as a command variable.

27. The method as claimed in claim 20, wherein during the joining process, the driving of the linear drive elements starting from the reference position is carried out according to the geometrical data, available in the controller, of the object to be produced from the components to be joined.

28. The method as claimed in claim 20, wherein the target criterion for ending the feeding of the components by the linear drive elements is the reaching of a predefined feed displacement.

29. The method as claimed in claim 20, wherein the target criterion for ending the feeding of the components by the linear drive elements is the reaching of a defined limiting force, which is higher than the clamping force during the feed process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 shows a schematic perspective representation of a laser welding system,

[0038] FIG. 2 shows a very highly schematic partial sectional representation of the laser welding system,

[0039] FIG. 3 shows a flowchart for a welding process carried out on this laser welding system,

[0040] FIG. 4 shows a chart of the clamping forces of the individual linear drive elements of the laser welding system,

[0041] FIG. 5 shows a time/feed displacement diagram of these linear drive elements,

[0042] FIGS. 6 and 7 show representations similar to FIGS. 4 and 5 with clamping forces of the linear drive elements differing from one another, and

[0043] FIGS. 8 and 9 show time/feed displacement diagrams of further alternative drivings of the linear drive elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0044] As may be seen from FIGS. 1 and 2, an exemplary joining apparatus is configured as a laser welding system in which a lower workpiece holder 1 receives a first component 2, for example a lamp housing of a motor vehicle tail lamp, and an upper workpiece holder 3 receives a second component 4, for example the lens of the tail lamp, which covers the lamp housing, for the welding process. The upper workpiece holder 3 is positioned in a fixed location by means of a base 5 on a stationary bridge 6, the second component 4 being, for example, fixed in the workshop holder 3 by applying a vacuum.

[0045] The lower workpiece holder 1 is arranged on a bearing element in the form of a substantially horizontally arranged bearing plate 7 which is movably driven by a clamping drive, denoted as a whole by SA, in the vertical feed direction Z in order to carry out feeding of the second component 4 to the first component 2 and bracing of these two components 2, 4. The clamping drive SA consists of eight vertically directed linear drive elements in the form of linear servo drives 8.1 to 8.8, which are positioned in two groups of four arranged in a rectangle in a bottom plate 18.

[0046] As revealed by FIG. 2, the laser welding system comprises a central controller 9 which, besides the clamping drive SA, also controls a schematically indicated laser welding device LS having a laser source 10, imaging optics 11 and a light guide 17 between them for the laser beam 12 carrying out the welding of the two components 2, 4.

[0047] The linear servo drives 8.1 to 8.8of which only the one linear servo drive 8.4 is shown in FIG. 2are respectively connected by their spindle motors 13 to the controller 9. The linear servo drives furthermore respectively comprise a detector 14 for recording the forward movement position and a detector 15 for recording the clamping force of the respective linear servo drive 8.1 to 8.8. These detectors 14, 15 deliver their recorded values to the controller 9.

[0048] As is furthermore schematically indicated in FIG. 2, the bearing plate 7 rests loosely on the round heads of the linear servo drives 8.1 to 8.8 by means of a spherical cap-shaped indentation 16, so that a floating bearing of the bearing plate 7 on the linear servo drives 8.1 to 8.8 is obtained overall, which allows tilting of the bearing plate 7 and therefore of the workpiece holders 1, 3 relative to one another as indicated by the arrow V.

[0049] The basic method sequence of the clamping and welding process should now be explained with the aid of FIG. 3. It is not represented in the drawings that the clamping drive SA is initially moved downward. The system is therefore opened and the components 2, 4 are placed in the lower workpiece holder 1step A.

[0050] The controller 9 then activates the clamping drive SA and moves the linear servo drives 8.1 to 8.8 uniformly upward. The components 2, 4 are thereby brought into the working positionstep B.

[0051] At the end of this step B, the determination of a reference position is carried outstep Cby feeding the lower workpiece holder 1 with the two components 2, 4 into contact against the upper workpiece holder 3. The clamping force applied in this case is recorded for each clamping drive by the respective clamping force detector 15 and compared by the controller 9 with a predefined system setpoint value, for example 2 kN. As soon as this value is reached, the position of the corresponding linear servo drive 8.1 to 8.8 is zeroed and this contact position is established as a reference position for measuring the further setting displacement between the two workpiece holders 1, 3 and the corresponding two components 2, during the laser welding.

[0052] The welding process is then carried outstep D, during which the two components 2, 4 are welded together in the conventional way in the region of their welding flange 19, 20 together by applying the laser beam 12 to them. As will be explained in more detail below with the aid of FIGS. 4 to 9, operation may in this case be carried out with various regulating strategies, until a corresponding target criterion is reached and the welding process is therefore ended by switching off the laser beam 12step E.

[0053] The workpiece joined from the two components 2, 4 is subsequently still kept under pressure in a defined way until the plastic cools, particularly in the region of the melted weld seam, and a permanent connection is produced between the two components 2, 4step F.

[0054] In order to remove the workpiece, the bearing plate 7 with the workpiece holder 1 and the complete workpiece is moved downward into the bottom position with the aid of the clamping drive SAstep Gand the workpiece can be removedstep H.

[0055] The aforementioned regulating strategies will now be discussed in more detail below. Thus, FIG. 4 shows the adjustment of the clamping force setpoint values FSETPOINT of the eight linear servo drives 8.1 to 8.8 to a common equal value of 2 kN. Each linear servo drive is in this case thus driven in steps B and C until the reaching of this setpoint value is recorded by means of its clamping force detector 15. In practice, this means that in the event of tolerances, for example in the region of the interfaces between the two components 2, 4, the linear servo drives 8.1 to 8.8 find their zero point individually and are correspondingly moved into slightly different height positions as the respective reference position.

[0056] Starting from this position, in a first alternative, during the welding processstep Dthe linear servo drives 8.1 to 8.8 can be driven individually during the further forward movement with a predefined clamping force of for example 2 kN. Although this leads to a very homogeneous force profile during the welding process, as may be seen from FIG. 5, the feed displacement x

(=setting displacement of the two components 2, 4 respective to one another) achieved in this case may vary greatly however from drive to drive because of the melting process between the two components 2, 4. For example, the reaching of a setpoint setting displacement of all drives of 0.5 mm may be defined as a switch-off criterion for ending the welding process.

[0057] In the alternative shown in FIGS. 6 and 7 of the control of the welding process, for step C different clamping force setpoint values F.sub.SETPOINT are predefined for the various linear actuating drives 8.1 to 8.8. Thus, matching values of 1.8 kN are defined for the linear drives 8.1 to 8.4, while about 2.3 kN to 2.5 kN are applied to the linear drives 8.5 to 8.8 arranged in the rear row in order to establish the reference position. The starting positions of the individual linear servo drives may therefore deviate even more significantly than in the previous exemplary embodiment. As may be seen clearly from FIG. 7, however, during the subsequent welding, while regulating the linear servo drives 8.1 to 8.8 to a defined setpoint clamping force, a substantially more homogeneous profile of the feed displacement x is achieved. This significantly improves the dimensional accuracy of the workpiece produced from the components 2, 4.

[0058] In the regulating strategy explained with the aid of FIG. 8 for the welding process, in a similar way to the previous procedure, it is again assumed that the zero point of the individual linear servo drives and correspondingly the reference position for the welding process is again adjusted by means of the reaching of a defined setpoint clamping force. Then, however, for the welding process the linear servo drives are coupled in terms of control technology so that the drive for which the highest counterforce is determined with the aid of the clamping force detector 15 is used as a leading axis, which specifies the feed displacement x for all linear servo drives 8.1 to 8.8. Correspondingly, in FIG. 8 their feed displacements correspond to one another within the system tolerances. Naturally, the feed process and therefore the setting displacement achieved are very homogeneous, which in turn favors the dimensional accuracy of the workpiece. However, this leads to clamping forces that vary during the welding process. Again, the reaching of a setpoint feed displacement of for example 0.5 mm is established as a switch-off criterion for the welding process.

[0059] With the aid of FIG. 9, a variant of the regulating strategy according to FIG. 8 will be explained. Here, although the linear servo drive applying the highest clamping force is again used as a leading axis, this however specifies a matching setting or feed displacement only for one group of linear servo drives (lower graph in FIG. 9). A second group of linear servo drives is controlled in such a way that they travel a significantly greater feed displacement (upper graph in FIG. 9). Tolerances can therefore be compensated for even better. In particular, dimensional accuracy of the overall component may be ensured even in the event of dimensional deviations of the individual components 2, 4. The reaching of an individual setpoint setting displacement may be the switch-off criterion in this case.

[0060] Lastly, variants (not graphically represented) for regulating strategies during the welding, in which the reference position is again defined as in the exemplary embodiments above, are also to be added.

[0061] In one variant, dimensional accuracy of the individual components may be ensured by an individual setting displacement adjustment, the actual dimensioning of the component being determined by means of the reference position and the setpoint dimensioning being known from the CAD data of the component. By comparing the actual and setpoint dimensioning, a locally required feed displacement may be calculated by the controller 9 and corresponding driving of the individual linear servo drives 8.1 to 8.8 may be carried out individually. Selection criteria may in this case again be that each linear servo drive has reached its individual setpoint setting displacement, in which case the clamping force, determining its forward movement speed, of the individual linear servo drives 8.1 to 8.8 may be adjusted according to the setpoint setting displacement of the individual drives, in such a way that the setpoint setting displacements are travelling at the same time and the melting of the components 2, 4 ends simultaneously at all points of the weld seam.

[0062] In another variant, operation may be carried out according to the manner of butt welding, by each linear servo drive being force-regulated individually. If a predefined setpoint clamping force is measured as exceeded with the aid of the respective clamping force detector 15 on a respective linear servo drive, it is deduced from this that the workpiece holders 1, 3 have been moved to the end in the region of this linear servo drive, so that the linear servo drive is switched off.