【 Abstract 】 : Why can arc welding robot replace manual assembly welding work? In recent years, with the rapid development of the company, new technologies, new methods, new processes, new materials are gradually applied to the production and manufacturing

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Why can arc welding robot replace manual assembly welding work? In recent years, with the rapid development of the company, new technologies, new methods, new processes, new materials are gradually applied to the production and manufacturing. At present, the company's welding automation equipment is developing to welding automation production line and digital welding workshop. The application of welding robot in the welding of high-speed emu, intercity bullet train, tram locomotive, diesel locomotive and urban rail track is also in line with the development trend of mechanical manufacturing. Based on the above factors, the paper puts forward the popularization and application of the robot aluminum alloy body welding.

1. Application status

(1) Application status? At present, arc welding robot only carries out 4 lateral straight welds of bottom frame and side wall, top cover and side wall on the vehicle body assembly welding table. The total length of the weld is less than 40m, accounting for about 10% of the weld of the table.

(2) Existing problems:

First, the problem of low weld proportion of arc welding robot. Aluminum alloy car body manufacturing was introduced by the company from Siemens Vienna SJP factory in 2004. At present, the robot welding application of car body assembly welding stand has not been improved for nearly 13 years. Many long welds on the car body threshold and end wall are still welded by hand, which is not in line with the development trend of welding automation and digitization.

Second, the utilization of equipment. At present, the welding of arc welding robot on the team only works for about 1.5h for each car body, and the rest of the time the equipment is idle in the team. According to the 24h manufacturing cycle of each car, the arc welding robot only accounts for about 1/16, and the equipment utilization rate is seriously insufficient.

Third, the quality of welded joints. Since the welding quality of manual welding is related to the welder's skill level and personal status, the weld quality of the side wall unit is unstable. And the automatic welding seam of arc welding robot, its process parameters are the best parameters found after many times of process verification. Under the premise of good workpiece assembly, as long as the welding machine can run normally, its welding seam can ensure the consistency of joint quality. FIG. 3 shows the comparison of welds between automatic and manual welding.

Fourth, large amount of polishing after welding. After vehicle body assembly welding, in order to ensure the appearance of the vehicle body, the exterior weld of the vehicle body shall be polished and level before painting. The residual weld height of manual welding shall reach about 3mm, while the weld of automatic welding is generally less than 2mm, which reduces the polishing time of the exterior wall of the vehicle body by more than 1/3.

2. Improvement of arc welding robot process

(1) The application of robot welding of vehicle body assembly under the threshold? The threshold under the car body is a straight single HY straight fillet weld. The robot welding program is very easy and will not affect other people's work during the welding process. The welding parameters are adjusted appropriately according to manual welding parameters.

(2) The application of robot welding on the threshold of vehicle body assembly? The upper threshold of the car body is a full fusion of HV-shaped cross butt weld with CPB quality. Due to the high requirement of welding quality and the adoption of multi-layer and multi-channel welding, there is a certain difficulty in the welding process. Multiple process verification shall be conducted to determine reasonable welding parameters before welding.

(3) The application of robot welding of vehicle body assembly end wall? The difficult point in the application of robot welding of vehicle assembly end wall is a lap vertical fillet weld of the end wall. Since the robot welding used before is mostly flat welding and horizontal welding, vertical welding welding position is rarely used, and the robot welding Angle and technological parameters are different from the previous, it is necessary to simulate the workpiece for welding test, and then conduct the welding of the product after the specimen is qualified.

3. Verification process and record

(1) The verification process and record of automatic welding of vehicle body assembly under the threshold? The threshold profile (EN AW-6005A-T6) and the bottom frame side beam profile (EN AW-6005A-T6) were selected for the verification test of the automatic welding process of the lower threshold. (2) According to PWPS, conduct sample welding on the IGM automatic welder in class 3, and the welding parameters are shown in Table 1. (3) Sample after welding, the appearance and macroscopic metallographic examination, automatic welding seam appearance and macroscopic metallographic examination comply with ISO 10042 aluminum alloy and aluminum alloy arc welding joint - grade B evaluation standard requirements in defect quality grade. After the plate test, the welding parameters were verified and the products were welded. The verification results were shown in Figure 8.

The threshold is a straight line welding seam, easy to program, only need one working step to complete the welding, and the weld shape is good, automatic welding seam appearance and macroscopic metallographic conform to ISO 10042 aluminum alloy and aluminum alloy arc welding joint - grade B evaluation standard requirements in defect quality grade.

(2) The automatic welding verification process and record of the door beam welded to the vehicle body assembly? 1. Select EN AW-6005A-T6 for upper door beam profile and EN AW-6005A-T6 for upper threshold automatic welding process verification test. (2) Conduct sample welding according to PWPS on the IGM automatic welder in class 3 of the car body. The welding parameters are shown in Table 2. (3) Sample after welding, the appearance and macroscopic metallographic examination, automatic welding seam appearance and macroscopic metallographic examination comply with ISO 10042 aluminum alloy and aluminum alloy arc welding joint - grade B evaluation standard requirements in defect quality grade. (4) After the plate test, the product was welded with verified welding parameters, and the verification results are shown in Figure 10.

(3) The automatic welding verification process and record of the car body assembly welding end wall? Two pieces of 300×150mm test plates (EN AW 5083) are selected for each group of tests to carry out the end wall automatic welding test. (2) Two groups of welding parameters are selected to conduct sample welding on the IGM automatic welder of the car body. The welding parameters are shown in Table 3. (3) Sample after welding, appearance and macroscopic metallographic examination, welding parameter 2 is better than welding parameter 1 depth of penetration, automatic welding seam appearance and macroscopic metallographic in accordance with ISO 10042 aluminum alloy and aluminum alloy arc welding joint - grade B evaluation standard requirements in defect quality grade. (4) After the plate test, the welding parameters were verified, considering the actual situation of the end wall automatic welding is more complex, so select a section of end wall products for product process verification. For the first welding of the end wall product, due to the large welding gun Angle (85°), the weld forming is poor. After the adjustment of the Angle to 75°, the weld forming is better. The appearance of automatic welding welding seam and the macroscopic metallographic phase meet the requirements of ISO 10042 aluminum alloy and aluminum alloy arc welding joint - Grade B evaluation standard in defect quality grade.

4. Effect comparison before and after improvement

(1) The improved effect after the body threshold welding? Before the improvement, there are three sections of welding joints on the threshold, and three joints and three arcs on each, which not only affects the quality of welding seam, but also increases the amount of grinding under the platform. And automatic from beginning to end of the completion of a welding, almost no polishing under the table, and the appearance of the weld shape beautiful.

(2) The improved effect after welding the upper door beam of the vehicle body? Over use second three welding, the welding quantity is bigger, before using manual welding, due to the manual operation, the appearance of weld forming rugged, in order to ensure the weld is not lower than the parent metal, the weld reinforcement is bigger, increased the audience outside wall, grinding time, and the automatic weld can not only guarantee the quality of weld (can adjust welding parameter control over high), and reduce the labor intensity of welders.

(3) The improved effect after welding the car body end wall? Welding of car body end wall by hand; Because the welding seam is long, so there are many joints, and the automatic welding is completed once from beginning to end, which not only guarantees the appearance quality of the welding seam, but also reduces the polishing of the joint under the platform.

5. Conclusion

Through the popularization and application of arc welding robot in aluminum alloy car-body compound, car body compound welding robot welding equipment each section of car body welding time increased to more than 4 h, the utilization rate of arc welding robot welding products high 2 ~ 3 times, car body, the proportion of automatic welding compound increased from 6% to 16%, save when the welding, grinding 500 h a year of above. At the same time, it can reduce the adverse factors such as the shaking of welding gun in the welder operation, ensure the uniform stability of welding seam and improve the welding quality, which proves that the improved effect of the welding application of aluminum alloy body of arc welding robot this time is good, and provides reference for the application of welding robot of other body body welding stations in the future.