Remote control welding technology in the hottest a

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Remote control welding technology in automobile manufacturing

a set of remote control laser welding system (RWS) has been put into full production in Magna autotek, bobra, Mexico. This set of RWS adopts high-power CO2 laser and movable reflector, and uses the energy of laser beam to weld sheet metal parts. The advent of CO2 laser with high power and excellent beam quality enables this technology to be applied to 1m × 1m or larger processing area. Compared with the traditional process, this method has the advantages of fast cycle and small land occupation. Magna autotek is a "first-class" automotive supplier, which uses remote-control laser welding technology for a part supplied to an automobile assembly plant

this part is the 2005 Volkswagen Jetta A5 door side impact bar, which is made of three stamping parts. 4. Please weld the grounding part at the grounding mark of the mortar tensile testing machine. There are 12 lap welds on this galvanized mild steel component. Full capacity production began last October and is expected to produce 317000 vehicles per year within five years. Because there are left door and right door, the annual output of side impact bars is 634000. Autotek factory implements a two shift working system of five days a week, which is equivalent to producing 235 pieces per hour, that is, each part takes about 15.3 seconds

laser welding is specified on the user's part drawing, because this part has been produced in Germany in this way, and the Mexican factory also uses the same parts to assemble cars. In order to determine the laser welding process most suitable for this purpose, autotek evaluated the nd:yag laser and remote welding CO2 laser for industrial robots. As mentioned above, this part is produced in Germany with nd:yag lasers and industrial robots. Autotek has made plans for these two welding methods, and inquired from some potential "integrated system suppliers" to obtain the investment cost. The conclusions for this application are summarized as follows:

◆ the investment cost of the two systems is roughly the same, and the cost of one RWS workstation and two nd:yag lasers is the same. It takes 24 seconds for the existing nd:yag system to weld a part. Cycle time analysis shows that RWS can weld 2 pieces in 26 seconds (almost twice the above results). Therefore, in actual production, RWS can achieve a full load productivity of one piece every 15.3 seconds

◆ the maintenance cost of RWS system is much lower. Rofin "strip type" CO2 laser does not need to replace any optical components, and the premixed gas cylinder only needs to be replaced every 8 months. The nd:yag laser needs to change the pump lamp frequently, which consumes a lot of power, and the protective cover of the focusing lens must be changed frequently

◆ RWS is easy to program and realize different weld shapes and swing welding functions. This feature provides greater flexibility for "customizing" the weld mode according to the part structure and improving the overall welding strength and part stiffness

◆ RWS provides higher laser power and the ability to "jump" from one welding position to another quickly (50ms). This greatly accelerates the production cycle and provides flexibility for welding other parts with this system in the future

based on this analysis, autotek concluded that RWS is a cost-effective and flexible solution for the purpose of welding side impact bars

principle of remote control laser welding

in the late 1990s, high-power (minimum 3KW) CO2 lasers have been able to provide high beam quality. As shown in Figure 2, the standard RWS includes a high-power (up to 6 kW) CO2 laser and a "remote control" long focal length (usually 1000mm-1600mm) scanning system. The computer-driven motion system can execute the programming path like a robot or CNC controller to complete the laser welding of sheet metal components

beam scanning motion depends on high-speed linear motor or "galvanometer" motor, which can be set by the manufacturer. This enables the beam to move rapidly from one welding position to another, taking less than 50ms. The scanner also provides customized programmable weld shapes (pin shape, ring shape, fish scale shape, etc.), so that users can adopt the most appropriate weld bead contour for special welds

comparison of welding characteristics

the following is a summary of the comparison between remote control laser welding and traditional processes to further illustrate the advantages of RWS process in cycle time and floor area

resistance welding: resistance welding or spot welding has the following typical parameters:

welding time + time of robot moving welding gun ≈ 3~4 s

2-3 layers can be welded, and the total thickness of standard base metal is ≈ mm

weldable galvanized and bare steel plates

when welding, the welding gun acts as a "clamp" to pull the base metal together

electric arc welding: electric arc welding (GMAW) generally has the following typical parameters:

welding speed ≈ 1m/min

using the wire feeding mechanism to weld different welds (fillet weld, butt weld, etc.), 2 layers can be welded

the thickness of base metal is usually 1~3 mm, and the total thickness is 2~6mm

weldable galvanized and bare steel plates

assembly clearance of about 1/2 welding wire diameter is allowed

laser welding: the remote-controlled CO2 laser welding machine has the following typical parameters:

welding speed ≈ 3~6 m/min

the welding time is about 0.2~0.3 s, assuming that a spot weld is ≈ 15mm

2-3 layers can be welded, and the total thickness of standard base metal is ≈ mm

galvanized or bare steel plates can be welded, but the emission of zinc volatiles must be solved

the maximum assembly clearance of the welding point is required to be about 0.1~0.2mm

cycle time comparison: as mentioned above, the laser welding speed is faster than the traditional process. In any case, the significant gain of cycle time also comes from the "rapid movement" of the laser beam between the welds, that is, the rapid change of welding position. The robot usually needs 0.5~3s to move to the next welding position, while the remote welding machine is less than 50ms. If the welding time is added to the "fast moving" time, it can be concluded that the cycle time of remote welding is about 2 times faster than that of robot nd:yag, and 6-10 times faster than that of resistance welding or arc welding

comparison of floor area: remote control welding method is 2-6 times faster than other welding methods, so it generally requires a smaller floor area. This is indeed the case, because the number of welding power sources and the number of welding stations and transmission equipment have been significantly reduced. Compared with other welding methods, RWS devices may only occupy 25~50% of the space, which varies according to the purpose

flexibility comparison: the welding gun has no actual contact with the parts, so the welding table can be adjusted at any time to adapt to other parts, just change the tooling and call different procedures. In this way, it has the ability to process a series of low to medium batch stamping sheet metal assemblies in one stop. If the product contains many parts that need to enter and leave the small work area, intelligent logistics solutions will be needed

system layout and description

magna autotek is determined to become an "integrated supplier" to better control tooling design and better understand the whole process. The system layout and tooling design began in March, 2003. By December, 2003, the system was assembled and the first part was welded. The laser, scanner and cooler are all installed on the top of the interlayer to save space. Under the scanner box is a rotary workbench, which is equipped with two sets of clamps, so one set of clamps can weld parts while the other set of clamps can load. Stairs are the access to the mezzanine for routine system maintenance. The whole laser unit must be located on a special base to absorb the vibration of the stamping workshop less than 25 meters away from the laser unit. In order to avoid major accidents, it is absolutely necessary to measure the vibration before installation. The ground vibration must be less than the limit specified by the laser manufacturer. Moreover, the installation of exhaust system must be considered, because the smoke can absorb the laser

the design idea of the actual system is a rotary double station manual loading and unloading workbench. Two clamps installed in one station are used for the welding of the left door assembly, and two clamps installed in another station are used for the welding of the right door assembly. The operator unloads the welded components, puts them into the box, then loads a group of new stamping parts, and presses the "cycle start" key. Then, the workbench rotates, the welding procedure is started, and the process is repeated. In order to protect eyes, a half wall rotates with the rotary table, providing an opaque sealing environment for the welding process. For the safety of factory personnel, the system is sealed with thin metal plates to form a "class I" safety welding system

tooling and plasma suppression: Although the remote control laser welding method is fast and greatly saves space, there are indeed some problems that must be considered in tooling and parts assembly. The laser beam has no force, unlike in the case of spot welding, the electrode is installed on the clamp driven by the welding gun or hydraulic cylinder. As mentioned above, arc welding uses a wire feeding mechanism and takes into account the weld gap. Therefore, in order to locate and fix the parts to be welded, laser welding requires tooling fixtures

in addition, when laser welding galvanized materials, it is necessary to try to discharge zinc volatiles. Otherwise, the zinc will volatilize during the welding process, causing additional pores and pores in the weld. If galvanized materials are welded, the tooling must be combined with the special part fixture to jointly provide the method of volatile matter discharge

regardless of the metal coating (galvanized or uncoated), CO2 welding usually needs to suppress and/or disperse the plasma generated in the laser welding process, because the plasma interferes with the laser beam, which may cause the welding process to be unstable or completely unable to weld. "Plasma suppression gas" or "shielding gas" can be helium, nitrogen, air or a mixture of gases, depending on the specific purpose and laser power. In order to successfully apply remote welding technology, the position and opening sequence of gas nozzles are also important factors worth considering

autotek has designed and manufactured tooling fixtures by itself, which meets the needs of proper clamping of parts and positioning of protective gas nozzles. The first set of prototype tooling is expected to help you in future experiments. It will be completed in January 2003 to build a national aviation material production base and a national military civilian integration innovation demonstration zone, and conduct trial welding at the promatek r&d center in magna, Brampton, Ontario. As part of its continuous process improvement, autotek is now making the third improvement to the part fixture

part design: stamping parts suppliers using laser welding technology have solved the problem of volatile emissions by stamping a pit or round pit in the area to be welded. This feature can be directly on the stamping die or added after the stamping process. The final result is to form a gap of 0.1~0.2 mm, leaving a channel for the volatilization of zinc

unlike spot welding, laser welds are very narrow and require only one side welding. The scanning mirror of the remote welding machine can generate different weld shapes or styles under program control. In addition, laser welded parts are more rigid than spot welded parts and are not easy to bend

these concepts must be kept in mind in the design process of parts in order to make full use of the advantages of laser welding. The weld width is relatively small, which may reduce the weight of parts. For laser welding, the clearance holes required by many spot welding applications are unnecessary

autotek has considered the above problems for this anti side impact bar welding project. It can be seen from Figure 5 that small round pits are punched at the parts to be welded, which provides convenience for the volatilization of zinc. There are 12 welds on the part to form a solid and rigid component

the development of remote control welding tooling and parts is still relatively new. Although standard parts are used in the manufacturing fixture, special parts

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