MXPA96001774A - Method and apparatus to join two pieces of workmeters between - Google Patents

Abstract

The present invention relates to a method for joining two sheet-like metal work pieces together, in which the work pieces are joined together to form a butt joint, which comprises the steps of: fixing the work pieces similar to sheets in predetermined positions for the execution of the joining operations by means of the steps of: subjecting each of the work pieces similar to sheets on the one hand to a magnetic force having a magnetic field that passes inside the side of the workpiece. work and that returns outside the side of the workpiece, and confine the magnetic field substantially to a ferromagnetic path between the location where the magnetic field passes inside and outside the side of the workpiece, and submit each of the work pieces similar to sheets on the other side at a pressure

Description

METHOD AND APPARATUS FOR JOINING TWO METAL WORK PIECES BETWEEN The present invention relates to a method and apparatus for joining two workpieces together by welding, in which the workpieces rest on supporting surfaces, are in particular butt-joined to each other at their ends to form a union to each other. stop or are arranged in an overlapped relationship and are subject to pressure from opposite ends to the supporting surfaces. Various welding processes are known for joining two workpieces together, particularly for the manufacture of body components for motor vehicles. Especially it is worth noting that laser welding in which the metal parts on plates are butted together to form composite boards. However, other welding processes are also within the scope of the invention. A laser welding operation is normally carried out in the following manner. The work pieces are butted together in pairs, without prepared edges, are placed without significant lateral pressure and are fixed by means of fasteners. A first application of force to work pieces occurs at this stage. The workpieces can then be processed, for example they can be coated, as described in EP-A 0565846, to bring the separation within tolerance. This processing causes a second application of a force to the positioning system, in which considerable lateral forces can occur. Finally, effects of forces acting mainly laterally as a result of thermal stresses in the laser welding process also occur. It is important to find a way to block the lateral forces that occur. For example, if a pretreatment is performed by coating or profiling according to EP-A 0565846, the average lateral force, ie the average lateral (horizontal) force over the length of the welded seam, which occurs as a result of such pretreatment. It can be as high as -30N / mm. Thermal stresses due to welding produce an additional average lateral force of 20N / mm that also needs to be blocked. This means that on a work piece of approximately 1600 mm long, a clamping pressure (vertical) of approximately lOt must be exerted. To apply such pressure to the work pieces, high pressure elements and elements as well as massive structures are required. These need expensive steel constructions and larger engines if for example they are designed to be transverse. This in turn leads to structural problems in the machine itself, which reaches a size and weight that has to be taken into account when the machine is installed. One possibility that is suggested for fixing workpieces safely is to provide the surface of the machine table and / or pressure elements with friction liners that increase the coefficient of friction. However, only limited improvements can be obtained in this way and in turn such friction coatings are likely to become clogged with the kind of dirt that occurs in the laser welding process - fatty powder due to subsequent cooling with oil, example. The objective underlying the present invention is to develop a method and apparatus of the aforementioned type whereby the lateral forces that occur can be blocked and the work pieces are fixed more securely in the joining process, using the same even less massive structures or structures. The method to achieve this goal is to subject the work pieces to a magnetic force. Preferably the workpieces are both pressed against a machine table and magnetically attracted by the machine table. Thus, two different forces act on the work pieces. These forces are not simply combined, but, surprisingly, the supporting force of the work piece is increased by a disproportionate amount. This can completely prevent the work pieces from sliding in the welding operation. An increase in clamping pressure, and the massive machinery structure that this comprises, is no longer necessary. In addition, it is feasible to provide a magnetic field strength that varies along the length of the work piece. This means, for example, that it can be arranged that the work piece is attracted more strongly in the central area than in the marginal areas in which the pressure elements have a better grip of the work piece. There are many possible alternatives that should be considered as encompassed in the invention. A simple apparatus, to carry out the method, has at least one magnetic element on the machine table, with which a pressure element is associated. The pressure element can be in the form of clamps in the fjxtures. However, it is preferred to use a continuous pressure beam that rests on the workpiece over its entire length. Alternatively, instead of a continuous magnetic element, a number of individual elements can be arranged side by side.

In the case of thin plates, say 1-4 mm thick, it may be that the field lines pass through the plate. Therefore, an additional layer of ferromagnetic material can preferably be provided between the pressure element and the plate, ensuring an optimum formation of the magnetic field and the maximum effect. The pressure element itself, where it rests on the plate, can be made in the same way as ferromagnetic material. It is also feasible to subject the work pieces juxtaposed to different magnetic orientations. This means that the work pieces will be attracted to each other in the region of the same welding joint, reducing the width of the separation. This particularly improves the quality of the welded seam. It is also possible to carry out the invention in a continuous feeding arrangement according to US 5328083, for example, by providing endless tracks with magnets. Advantages, features and additional features of the present invention will be described in the following description of the preferred embodiments given by an example, and with reference to the drawings, in which: Figure 1 is a diagrammatic plan view of an apparatus for joining two pieces of work together by laser welding; Figure 2 is a diagrammatic side view of the apparatus according to Figure 1; Figure 3 is a diagrammatic front view of the two workpieces with a variant to reduce a joint gap; Figure 4 shows a cross-section through the apparatus according to the invention using a sleeve for welding different pairs of plates; Figure 5 is a plan view of the apparatus shown in Figure 4. As shown in Figure 1, the two workpieces 1.1 and 1.2 will be joined together, by welding, in particular by laser welding. The two workpieces 1.1 and 1.2 rest with their ends spliced together forming a butt joint 2. These are joined together in the region of the butt joint 2 by a laser 3 (see Figure 2) which directs a beam laser 4 on this stop joint 2. In Figure 1 a shock point is shown as 5. Both work pieces 1.1 and 1.2 are traversed in the x direction with respect to the laser 3, and a profile roll 6 is placed forward of the laser 3 as described in detail in EP-A 0565846. The profile roller 6 produces a groove in the region of the butt joint 2, displacing the material towards the butt joint 2 and thus reducing the width of the joint to cap 2 to a minimum. This process is called "coating". Both work pieces 1.1 and 1.2 rest on a machine table 7, which in the present case is constructed in two sections. A gap 8 is formed between the two sections of the machine table 7.1 and 7.2 and the laser beam 4 is able to pass through this separation. Workpieces 1.1 and 1.2 are attached to the sections of the machine table 7.1 and 7.2 respectively. This is done by providing at least one pressure beam 9.1 and 9.2 on each section, pressing down uniformly as far as possible along the entire length of the work pieces 1.1 and 1.2 respectively. The pressure beams 9.1, 9.2 can be subjected to the pressures required by the corresponding pressure boosters 10 acting at both ends or distributed over their length. Examples of suitable pressure boosters are hydraulic or pneumatic cylinders, but hydraulic or pneumatic pressure elements can also be used, but electrical or mechanical pressure elements can also be used; There is no intention to restrict the idea of invention in this aspect. What is significant for the present invention is that at least one magnetic element 11 (see Figure 2) should be included in the sections of the machine table 7.1 and 7.2. This magnetic element 11 may consist of a continuous plate, but it is also possible that it is formed by small separate elements. It is also feasible that the individual elements have different orientations, and / or are operated with different intensities of magnetic fields. In another embodiment of the invention according to Figure 3, the two magnetic elements 11.1 and 11.2 in the sections of the machine 7.1 and 7.2 have different orientations. This makes it possible to influence the two workpieces 1.1 and 1.2 magnetically so that a magnetic force is applied in the region of the butt joint 2 which pulls the two work pieces 1.1 and 1.2 together with which the width of the workpiece is reduced. the separation of the union 2. This results in a better welded-seam. Practical experiments have shown that the holding force experienced by the workpieces 1.1 and 1.2 of the pressure beams 9 and the magnetic elements 11 is greater, in a disproportionate amount, than the holding force of the pressure beams or elements. magnetic acting individually. The sustaining forces are not simply additive but increase in a disproportionate amount. Furthermore, the twisting or undulation of workpieces 1.1 and 1.2 is avoided, especially after laser welding.

But above all it is not necessary to have costly constructions and massive structures to produce sufficient clamping force. It has also been found that the fixing method selected from workpieces 1.1 and 1.2 results in better heat dissipation. Figure 4 is a cross-section through an apparatus for carrying out the present invention. This shows a machine frame 16.1, 30 with the ends of the lower part 16.1 of the frame specifically designed 10.1 and 10.2. A clamping table or sleeve 20 runs on the frame 16.1, 30 and is supported thereon by C-shaped elements, 20.1, 20.2, 29.1, 29.2. The magnets 23 form the support surfaces for plates 1.1 and 1.2. The pressure shoes 25, preferably of ferromagnetic material, are pressed against the plates 1.1, 1.2 by pressure elements 27. The pressure caused by the pressure elements 27 is combined with that of the magnets 23 with an effect more than proportional, with the result that the arrangement is capable of supporting more than proportionally larger lateral forces. The dissipation of heat due to welding in the joint 3 is supported by cooling ducts 24.1 and 24.2. From Figure 5 it can be seen that the sleeve, of which two yokes 29.1 and 29.2 are visible, runs along the entire length of the apparatus. At the point shown it is in a loading station F, through which it passes to the welding station S, and from there to a discharge station E from which the welded work pieces are separated. In the welding station, the butt joint is preferably coated by a coating unit 31 as described in EP-A 0565846. The coating unit 31 is preferably followed by a separation monitor 32 allowing the laser beam 2 located together to the machine detect the line of separation. After the butt joint has been welded by the laser 33, the welded seam is preferably treated in a brush unit 34 and greased in a cooling station 35. These treatments are followed by a quality inspection 36 and if necessary, the liner 37. Workpieces 1.1 and 1.2 pass through all these treatments while they are attached to the sleeve. Having described the invention as above, property is claimed as contained in the following:

Claims (12)

1. A method for joining two metallic workpieces together, in which the workpieces are in particular spliced together to form a butt joint and are joined together in the region of this butt joint, characterized in that, to fix the work pieces in their predetermined position for the execution of the joining operations, these are subjected on one side to a magnetic force.

2. The method according to claim 1, characterized in that the workpieces are subjected to the other side under pressure.

3. The method according to claim 1 or 2, characterized in that the workpieces are pressed against the table of the machine or the links of an endless traction arrangement and are magnetically attracted thereby.

4. The method according to claim 1, 2 or 3, characterized in that the intensity of the magnetic field can be varied over the length of the work pieces.

5. The method according to any of claims 1 to 4, characterized in that the workpieces are subjected to magnetic fields with different magnetic orientations.

6. An apparatus for carrying out the method according to any one of claims 1 to 5, comprising elements for performing the joining operations and a laser welding device for the metal plates, and a holding table or a continuous feeding arrangement. for the plates to be welded, which can also guide the plates in the lateral direction, by friction coupling elements, characterized in that the clamping table or the continuous feed arrangement has at least one magnetic element acting on the workpiece .

7. The apparatus according to claim 6, characterized in that the pressure element is disposed at the opposite end of the workpiece to the magnetic element.

8. The apparatus according to claim 7, characterized in that the pressure element comprises a pressure beam driven by at least one pressure driver.

9. The apparatus according to claim 7 or claim 8, characterized in that the pressure element comprises a ferromagnetic material.

10. The apparatus according to any of claims 6 to 9, characterized in that the magnetic element or elements are included in a machine table.

11. The apparatus according to any of claims 6 to 10, characterized in that the magnetic element is formed by a plurality of individual elements.

12. The apparatus according to claim 11, characterized in that the individual elements of the magnetic element have different field strengths.