Method for continuously conveying and butt-welding sheet metal parts and use of said method

Abstract

To increase cycle time, and therefore to lower production costs, in the industrial production of welded sheet metal partsin particular tailored blanks for the automotive industrythe invention describes a method based on a constant-speed conveying system and a flying optics system, which method manages without complex cooling of the hot weld seam and uses means for holding the workpieces on one side with a high force on the conveyor belt. In this way it is possible greatly to reduce the negative influence the blank spacing has on the cycle time of the machine. Overall, fewer drives are required in the machine and it is possible for a simplified machine concept to be employed without detriment to the quality of the blanks to be welded.

Claims

1. A method for conveying and butt-welding sheet metal, in which flat sheet metal workpieces are placed by a feeder on at least two conveyor belts which are moved continuously in a horizontal direction TR with a constant speed v.sub.TR, so that two respective to be welded edges of the two individual workpieces are butted together with formation of a gap and fixed with a holder on the surface of the conveyor belts, divided into individual segments, such that the individual workpieces can be held in the same position over a distance L, further with at least one welding lens for laser welding which is movable longitudinally and in height, and with a stationary quality sensor for monitoring a seam geometry before welding and for monitoring a weld seam after welding, as well as a remover unit for removal of the welded workpieces, characterized in that, during welding of the workpieces, the at least one welding lens is moved with formation of a weld seam with a speed v.sub.OS which is equal to the speed v.sub.TR of the conveyor belts reduced by a welding speed v.sub.S, in a same longitudinal direction as the conveying direction TR, and in that, after welding of the two individual workpieces into a welded blank, the at least one welding lens is moved with a speed v.sub.OR, a multiple of the speed v.sub.TR of the conveyor belts, in a direction opposite the conveying direction TR to a starting point OSA of a next seam to be welded.

2. The method according to claim 1, characterized in that the conveyor belts are driven by a chain drive via at least one drive sprocket, wherein the individual segments of the conveyor belts are designed as pole plates.

3. The method according to claim 1, characterized in that the holder is formed as an immobile magnetic holder, or as a vacuum module.

4. The method according to claim 3, characterized in that the magnetic holder comprises permanent magnets or switchable permanent magnets or electromagnets.

5. The method according to claim 1, wherein the holder comprises electromagnets, characterized in that, for fixing the individual workpieces to be welded on the conveyor belts, the holder is switched on via a control unit designed to be switched on and off, and is supplied with current, whereby a magnetic flux is generated which is transmitted via the holder to the segments, and for removing the welded blank after welding, the magnetic flux is switched off by switching off the current.

6. The method according to claim 5, characterized in that the magnetic flux is closed via the holder and the segments and the metallic individual workpieces, whereby a force F in the range of 10-12 N/cm2 is exerted on the workpiece such that during conveying the workpiece is fixed on one side from below on the conveyor belts.

7. The method according to claim 1, characterized in that, for fixing the individual workpiece, a magnetic flux is generated which exerts a magnetic force on the individual workpieces, whereby a gap closure between the individual workpieces to be welded takes place.

8. The method according to claim 1, characterized in that the monitoring of the remaining gap between the individual workpieces to be welded occurs by means of a camera, and a gap closure of the gap between the individual workpieces takes place by supplying filler wire between the individual workpieces.

9. The method according to claim 2, characterized in that the chain drive is designed as a belt drive or shuttle drive.

10. The method according to claim 1, characterized in that the sheet metal parts are butt-welded to form tailored blanks for a motor vehicle body.

11. The method according to claim 1, wherein the two individual workpieces are fixed on the surface of the conveyor belts only from below such that an accessibility from above is ensured.

12. The method according to claim 1 used in the construction of motor vehicle bodies in the automotive industry.

13. A method for conveying and laser butt-welding sheet metal workpieces, the method comprising steps of by means of a feeder placing the to be welded workpieces onto conveyor belts divided into individual segments, moving said conveyor belts continuously in a horizontal conveying direction TR with a constant speed v.sub.TR, butting together two edges of the workpieces with formation of a gap, by means of a holder fixing the workpieces on the surface of the conveyor belts only from below such that an accessibility from above is ensure, by means of at least one welding lens movable in the horizontal conveying direction and in a vertical direction welding the workpieces thereby forming a weld seam and creating a welded part, wherein during welding the welding lens is moved in the conveying direction TR with a speed v.sub.OS which is equal to the speed v.sub.TR reduced by a welding speed v.sub.S, after welding of the workpieces, moving the welding lens to a starting point OSA of a subsequent welding process in a direction opposite the conveying direction TR with a speed v.sub.OR which is a multiple of the speed v.sub.TR, by means of a stationary quality sensor monitoring a seam geometry before welding and monitoring the weld seam after welding, after releasing the fixation of the welded part, by means of a remover unit removing the welded part from the conveyor belts.

Description

(1) The present invention is explained in more detail below by means of embodiments with reference to drawings.

(2) FIG. 1 shows a schematic representation of an inventive arrangement with conveyor belts in cross-section,

(3) FIG. 2 shows a first plan view of the conveyor belts of the inventive arrangement outfitted with blanks at the beginning of welding, again in schematic representation,

(4) FIG. 3 shows a second plan view of the conveyor belts of the inventive arrangement outfitted with blanks during welding, again in schematic representation,

(5) FIG. 4 shows a third plan view of the conveyor belts of the inventive arrangement outfitted with blanks during welding, again in schematic representation, and

(6) FIG. 5 shows a fourth plan view of the conveyor belts of the inventive arrangement outfitted with blanks during return of the welding lens, again in schematic representation.

(7) FIG. 1 shows a magnetic chain conveyor 11 with the endless conveyor belt 3 movable in the conveying direction TR via the drive sprockets 1, the speed v.sub.TR of which conveyor belt 3 lies in the range of 1-30 m/min, and the segments 2 of which conveyor belt 3, which are preferably, but not exclusively, designed as circumferential pole plates, form a flat surface over a length L, upon which flat surface magnetizable individual workpieces 30a, 30b are placed in a first process step by means of feeding means 12 and held on the conveyor belt 3 with great force through preferably magnetic holding means 6, whereby a stationary first quality system 8 serves to monitor the position and gap width of the individual workpieces 30a, 30b to be welded. The distance D between the blanks 30a, 30b, 40, 50 is dependent on the layout of the individual workpieces 30a, 30b to be welded, where D can be kept small for rectangular horizontal sections of the individual workpieces 30a, 30b, and must be selected to be larger for, for example, rhomboidal layouts of the individual workpieces 30a, 30b. In a second process step, the individual workpieces 30a, 30b are connected with one another in the welding direction SRO in a material-locking manner into a welded blank 50 by means of the movable welding lens 7, whereby the quality of the weld seam is checked with a second stationary quality system 9 from above and optionally with an additional stationary camera 10 from below. When the belt has traveled the length L, the welded blank 50 is removed from the continuously running conveyor belt 3 in a third process step by means of means 13 for removing welded blanks after the previous release of the holding means 6.

(8) FIG. 2 shows a first plan view of the start of the welding process. The two conveyor belts 3, 4, each consisting of the segments 2, separated by the gap 5 both move continuously in the conveying direction TR at the same speed v.sub.TR. The blank before welding 30, consisting of the individual workpieces 30a, 30b to be welded, is fixed in the region of the edges 31, 32 on the conveyor belts 3, 4 with formation of the smallest possible gap 33. The blank being processed 40 has a minimal gap 43 in the region of the edges 41, 42due to cutting tolerancesand the welding lens 7 is positioned in the initial position OSA. The already-welded blank 50 is provided with a weld seam 51 and can be removed from the conveyor belts in a following process step.

(9) FIG. 3 shows a second plan view of the welding process. The welding lens 7 moves with a speed v.sub.OS=v.sub.TRv.sub.S in the same direction SRO as the conveying direction TR of the conveyor belts 3, 4 and welds the blank being processed 40 in the region of the edges 41, 42, which are separated from one another by a minimal gap 43present due to cutting tolerancespossibly by supplying filler wire. The welding lens 7 has moved from the position at the beginning of the weld seam OSA in the conveying direction TR. The two not yet welded blanks 30 are positioned for a subsequent welding process.

(10) FIG. 4 shows a third plan view of the end of the welding process. The welded blank is supplied with the weld seam 51 and the welding lens is now located in the position at the end of the weld seam OSE.

(11) FIG. 5 shows a fourth plan view of the return of the welding lens 7. After the welding lens 7 has reached the end of the welding position OSE, it moves with the speed v.sub.OR, which is a multiple of the conveying speed v.sub.TR, in the direction RRO opposite the conveying direction TR until it has reached the initial position OSA for welding the next blank to be welded 30.