Research on the Technology of Welding Manipulator in the Production of Locomotive Frame (Part 2)

3. Welding process

(1) Equipment selection Consider: ① The structure welds are symmetrically distributed. ② The welding space of most welds in the framework is limited, and the accessibility of welding torches is high. ③ Weld cross sections are V-butt welds with single bevels and single Y-fillet welds. Arc current / voltage fluctuations at the tip of the wire during manipulator swing are obvious. ④The size and position deviation of the frame assembly and the two wires of the twin wire welding gun are not synchronized. We decided to use: IMG double-gun slide rail welding robot RT1330S, which is used by companies with single-wire extension welding torches, with arc tracking (instead of common lasers or other additional tracking systems). The welding manipulator equipment needs to be welded by simulating working test pieces before welding work can be performed.

(2) Technical quality requirements before welding of the frame manipulator ① Strictly control the size, shape and position tolerances of the single beam of the frame frame to meet the requirements of the drawing. ② After assembly, it is required to control the gap of butt welds at 3 ± 1 mm and the gap of T-type fillet welds at 0-2mm. ③ The deviation of the coordinates of each weld position from the reference point after assembly is within 2mm. ④ In order to eliminate the problems caused by the assembly error when welding the manipulator to the bottom and ensure the quality of the root welding, all the welds are bottom-welded by the manual MAG (135) method.

(3) Welding quality requirements Welders are required to take up their positions after obtaining the corresponding ISO9606-1 and EN1418 qualifications, and at the same time passing the welding simulation test specimens.

(4) Welding process evaluation and test In order to ensure the welding quality of the robot, we perform the process evaluation by working test pieces to determine the welding parameters of the robot.

First, the work flow: According to the requirements of ISO 15614-1, the welding process of the manipulator needs to be evaluated. The main process is: statistics of welding joints → determination of process evaluation items → release of test plates for process evaluation → preparation of pre-welding rules (PWPS) → robot Welding and recording real-time data → appearance test of the test piece (100% VT) → non-destructive testing (100% MT 100% UT (butt weld)) → destructive test (metallographic tensile and reverse bending test) → formal Welding Procedure Specification (WPS)

Second, the welding procedure specification (WPS) After the welding procedure qualification, we have determined the following welding procedure specification (WPS).

First, butt welds: the welding position PA, and the weld bead is arranged in 3 layers and 5 passes.

Third, in order to further verify the physical welding quality of the product and the accessibility of the robotic torch operation, we performed a physical simulation test. Because the overall welding seam of the frame is arranged in a symmetrical structure, the real mold is carried out with a half-edge frame. The product accessories that may affect the accessibility of the manipulator on the part of the frame are replaced by steel plates.

According to the above process parameters, the welding process file is prepared for welding. After welding, the non-destructive test (NDT) is performed on the simulated test piece welds according to the drawings and anatomic sampling is performed (two sections of each type of welds of the same type), and metallographic and HV10 hardness The test meets the requirements.

Fourth, after the simulation test, it was found that at the corner of the triple weld between each beam beam side plate, side beam wing plate, and beam plate, the robot arm could not perform continuous welding because the corner was too small, and we used manual welding under the tire. 

China Welding Manipulator

4. Programming of the welding manipulator

The programming of the welding of the framework robot is performed in the teach mode.

(1) Reasonably use the tracking positioning system to effectively confirm the arc starting position of the weld. As shown in Figure 3, by repeatedly positioning in three directions, the welding arc starting point is repositioned.

(2) The joint cooperation between the external axis and the internal axis of the manipulator is reasonably used, and the welding is performed by double-gun symmetrical welding, as shown in Fig. 4, under the premise of ensuring product quality, taking into account production efficiency, and welding a single layer for the first time. After the flip is symmetrically connected, the other filling layers are welded in 2 layers at a time.

(3) Due to the use of arc-quenching plates in the design of the butt welds on the structure, the butt welds are welded according to the normal welding steps, and the remaining connection welds need to be re-welded to reduce defects in the welded joints.

5. Application

After completing the robotic welding process evaluation test and physical simulation test of the locomotive frame, we prepared the welding parameters and specifications of the vehicle model. After passing the first frame fatigue test verification, we carried out small-scale production of the locomotive frame The locomotive has been put into operation, and the user has no feedback on quality problems, which indicates that the welding process of the manipulator is applicable to the welding production of the frame. So far, our company has realized a total of 11 different models of robotic welding production of bogie products for similar internal combustion and electric locomotive bogie products.

6. Conclusion

We selected a locomotive frame with a typical representative for the welding process qualification test and physical simulation test of a China welding manipulator. Through the tests, reasonable welding parameters and specifications were obtained. Subsequently, the first verification and small batch production were performed, which showed that the welding manipulator can meet the welding production of the locomotive frame, and the process is reliable. It provided valuable reference for the preparation and implementation of the welding process of the manipulator for similar structures in the later period, and also for the later The locomotive framework will realize a certain exploration of intelligent manufacturing.