Influence of the hottest long-distance laser weldi

Influence of long-distance laser welding on automobile manufacturing

in 2004, a laser based long-distance welding system (RWS) was fully put into production in Magna autotek, Puebla, Mexico. This RWS uses a high-power CO2 laser beam and a movable mirror to guide the laser to weld sheet metal parts. The emergence of high-power CO2 lasers with good beam quality enables the technology to operate in a working area of 1 m x 1 m or larger. Compared with traditional technology, the advantages of this technology include faster cycle time and smaller floor area (production area). Magna autotek, a "tier 1" automotive supplier, has produced a part for other automotive assembly plants using long-distance laser welding technology

this part is used in 2005 Volkswagen Jetta A5. It is a door beam impact member assembly, which is composed of three single stamping parts welded together. On galvanized mild steel, there are 12 overlapping welds (see Figure 1). Full production began in October last year, and it is estimated that the annual production volume will be 317000 vehicles in the five-year period. Because there are left door and right door, it requires 634000 door beam stamping assemblies to be produced every year. Because autotek operates in two shifts and works five days a week, it shows that the productivity of the system is 235 parts per hour, and it takes only 15.3 seconds to produce one part on average

Figure 1 Stamping assembly: there are 12 overlapping welds on galvanized low carbon steel

because laser welding has been used for production in Germany, it is specified in the customer's drawing that laser welding should be used. Therefore, this factory in Mexico will use the same parts to assemble vehicles. Autotek evaluated the nd:yag laser installed on the manipulator and the CO2 laser with remote welding function, in order to select the best processing technology for it. As has been noted, this part has been produced in Germany with nd:yag lasers and industrial robots. Autotek wants to get information about processing and investment costs from potential system suppliers. The following is a summary of several conclusions related to this application:

* the investment costs of these two systems are similar, because two nd:yag lasers are required, while only one RWS workstation is required. It takes 24 seconds for the existing nd:yag system to process a part. Cycle analysis shows that RWS can produce two parts in 26 seconds (almost twice the output). Therefore, with one RWS, the total production capacity can be achieved: 15.3 seconds to produce a part

* RWS has a much lower system maintenance cost. Rofin "flat panel" CO2 laser does not need to replace any optical elements, but only needs to replace a premixed gas bottle every 8 months. The lamp of nd:yag laser needs to be replaced frequently, and the cost of electricity is high. The focusing optical system requires frequent replacement of the protective "cover"

* RWS is easy to program for various weld shapes and braiding functions. This provides greater flexibility for creating various weld patterns, and can better meet the design requirements of customers to achieve higher overall weld strength and part hardness

* RWS has high laser power and can quickly move from one solder joint to the next, with a jump time of only 50ms. This greatly accelerates the production cycle and provides convenience for assembling other parts with the system in the future

on the basis of this analysis, autotek confirmed that RWS is a solution with lower cost and higher flexibility for its door beam stamping assembly application

key points of long-distance laser welding

in the late 1990s, high-power (3 kW and above) CO2 lasers have appeared, and the beam quality is very good. The typical RWS shown in Figure 2 includes a high-power (up to 6 kW) CO2 laser and a "long distance" scanning system with a long focal length (typically 1000 mm-1600 mm). The computer-driven motion system can complete the laser welding of sheet metal components to be welded by walking a certain distance according to the program, just like the manipulator or CNC controller

Figure 2 Typical long-distance welding system

the scanning movement of the beam can be realized by using high-speed, linear motor or "galvanometer" according to the requirements of the manufacturer. This accelerates the moving speed from one solder joint to the next, and the moving time is less than 50ms. The scanner can also provide customers with programmable weld shapes (seams, circles, braids and other patterns), allowing users to adopt the best path for special welding

comparison of welding characteristics

in order to further illustrate the advantages of RWS in processing cycle and floor area, long-distance laser welding is compared with traditional welding methods. The results are as follows:

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

* welding time + time of robot moving welding gun ≈ seconds

* weldable layer, Total material thickness ≈ mm

* weldable coated or uncoated steel plate

* the welding gun acts as a "clamp". During welding, the materials are pulled together

electric arc welding - typical parameters of electric arc welding (GMAW) are as follows:

* welding Cedric Kennedy specializes in recycling waste plastics into 3D printing materials. The connection speed is ≈ 1 meter/minute

* two layers can be welded using wire feeder, The connection structure can be various (ribbon, butt joint, etc.)

* the material thickness is typically mm, and the total thickness is mm

* weldable coated or uncoated steel plate

* the "gap" between the welded parts is allowed to be about 1/2 of the diameter of the welding wire

laser welding -- CO2 long-distance laser welding machine has the following typical parameters:

* welding speed ≈ M/min

* welding time is about 0 3 seconds, weld length 15 mm ≈ a spot weld

* weldable layer, total material thickness ≈ mm

* weldable coated or uncoated steel plate, but the discharge of zinc must be considered

* it is required that the welded parts should be as close as possible, and the maximum allowable gap is 0 2 mm

cycle time comparison -- as mentioned above, laser welding time is much faster than traditional methods. However, the advantage of cycle time is also related to rapid movement or rapid replacement between different solder joints. The time required for the manipulator to move from one point to the next is about 0 Second, with the remote welding machine, this time is less than 50ms. By combining the welding time with the "fast moving" time, we can draw the following conclusion: the cycle time of long-distance welding is twice faster than that of nd: YAG plus manipulator welding, and times faster than that of resistance welding and arc welding

floor space comparison -- because the long-distance welding process is times faster than other welding procedures, it requires less production space. Now, this has become a reality, because the total number of welding energy, welding stations and transmission equipment has been greatly reduced. In different applications, the plant area required for the installation of RWS is only% of that required by other welding processes

flexibility comparison -- because during laser welding, the welding gun does not actually contact the parts (so the term "remote distance" is used), so when processing different parts, the welding station is easy to deal with, just simply changing the fixture and calling different programs. In this way, a welding station can process small and medium batches of metal parts and accessories. Products with multiple parts are moved in and out of a small production space, which requires an intelligent logistics solution

system layout and description

magna autotek decides to integrate the system by itself, so that it can better control fixture design and better understand the machining process. In June, 2003, the system layout and fixture design began. By December, 2003, the system had been installed and the first part had been welded. The laser scanning box and cooler are installed on the top of the middle layer to reduce the floor area. There is a rotary table under the scanning box, on which two clamps are fixed. When the parts on one fixture are welded, the parts can be loaded and unloaded on the other fixture. With the help of the escalator, you can go to the middle floor for routine maintenance. The whole laser welding room must be placed on a special foundation to absorb the vibration within 25 meters around the welding room. In order to avoid major problems, it is absolutely necessary to measure the vibration before installation. The floor vibration must be less than the limit specified by the laser supplier. Because dust and smoke will absorb the laser, the exhaust system must also be considered

Figure 3 The remote welding system during assembly contains a two-stop rotary table

which can be loaded and unloaded manually. The actual system is shown in Figure 3. The key is a two-stop rotary table that can be loaded and unloaded manually. One station has two clamps for right-hand assembly; Another station also has two clamps for left-hand assembly. After the operators remove the welded components, put them into the liuteng box, and then install a group of new stamping parts, push the "cycle start", the rotary table rotates, the welding procedure starts, and the process repeats. Local walls rotate with the rotary table, which can provide "shelter" during welding to protect eyes. The whole system is protected with sheet metal to create a "level 1" welding system to ensure the safety of employees

fixture and plasma suppression - long distance laser solution, on the one hand, has the advantages of fast processing speed and small floor area, but it also faces challenges in the coordination of fixture and parts. The laser has no force and long service life. Unlike spot welding, the electrode is attached to the gun or the positioning mechanism driven by the cylinder. As pointed out earlier, welding rods are used for arc welding, so a certain gap is allowed in the weld. Laser welding is done by ourselves, that is, no filler is used. Therefore, laser welding requires the fixture to be placed and fixed in the welded area

in addition, when laser welding galvanized materials, it is required to try to discharge the volatiles of zinc. Otherwise, zinc will explode through the weld, resulting in porosity and multiple bursts. For galvanized materials, fixtures must work in conjunction with special part features to provide a means of venting gases

regardless of the condition of metal coating (galvanized or bare), CO2 welding generally requires trying to suppress the plasma generated in the welding process or blow it away. This is because the plasma interferes with the laser beam, which makes the welding process unstable or makes the welding completely fail. The plasma suppression or "shielding gas" can be helium, nitrogen, air or some combination of gases, depending on the application and the power used. In order to successfully carry out long-distance welding, it is also very important to arrange the position of gas nozzles and determine the time to open them

Figure 4 Part fixture that can meet the needs of properly clamping parts and shielding gas nozzle position

autotek designed and built its own fixture. The fixture can meet the needs of properly clamping parts and the best shielding gas nozzle position at the same time. The first prototype fixture was completed in June 2003, and the welding work was completed on the promatek r&d equipment in magna, Brampton, Ontario. Now, autotek is repeating its part fixture for the third time to continuously improve the quality of laser welding. The fixture used is shown in Figure 4. Pay attention to the positioning method and the shielding gas nozzle position near the weld. Goldilocks pp-lgf products have excellent mechanical properties

part design - stamping parts suppliers for laser welding have solved the exhaust problem by embossing or forming dimples in the welded area. This feature can be incorporated into the stamping die or in the stamping process