Problems and Solutions in Welding Manipulator Application

1. Analysis and treatment of welding defects

The welding of the manipulator uses argon-rich mixed gas shielded welding. The welding defects that occur during the welding process generally include welding deviation, undercut, and porosity.

(1) If the welding deviation occurs, the welding position may be incorrect or there may be a problem when searching for the welding torch. At this time, it is necessary to consider whether the TCP (center position of the welding torch) is accurate and adjust it. If this situation occurs frequently, check the zero position of each axis of the manipulator, and re-zero to correct it.

(2) The occurrence of undercutting may be due to improper selection of welding parameters, incorrect angle of welding gun, or position of the welding gun. The power can be adjusted appropriately to change welding parameters, the attitude of welding gun, and the relative position of welding gun and workpiece.

(3) The occurrence of air holes may be due to poor gas protection, the primer of the workpiece is too thick or the protective gas is not dry enough, and it can be dealt with by adjusting accordingly.

(4) Excessive spattering may be due to improper selection of welding parameters, gas component reasons, or too long wire external elongation. The power can be adjusted appropriately to change the welding parameters. The gas ratio meter can be adjusted to adjust the ratio of mixed gas. The relative position of the workpiece.

(5) An arc crater is formed at the end of the welding seam after cooling, and the submerged arc crater function can be added to the working step during programming to fill it.

2. Failure analysis and treatment of manipulator

During the welding process, China welding manipulator encountered some failures. The following are common:

(1) A gunshot occurred. It may be due to the deviation of the workpiece assembly or the inaccurate TCP of the welding gun. You can check the assembly or correct the TCP of the welding gun.

(2) An arc fault occurs and the arc cannot be initiated. It may be because the welding wire does not touch the workpiece or the process parameters are too small. You can manually feed the wire, adjust the distance between the welding gun and the weld, or adjust the process parameters appropriately.

(3) Guard gas monitoring alarm. If the cooling water or shielding gas supply is faulty, check the cooling water or shielding gas pipeline.

3. Application experience of welding manipulator

As a teaching-reproducible manipulator, it is required that the assembly quality and accuracy of the workpiece must have a good consistency.

The application of welding manipulators should strictly control the quality of parts preparation and improve the accuracy of the welding assembly. The surface quality of the parts, bevel size, and assembly accuracy will affect the weld tracking effect.

The quality of part preparation and assembly accuracy of weldments can be improved from the following aspects.

(1) Prepare special welding process for welding manipulators, and carry out strict process regulations on part size, weld groove, and assembly size. General parts and groove size tolerance is controlled within ± 0.8mm, assembly size error is controlled within ± 1.5mm, the probability of welding defects such as blowholes and undercuts in the weld can be greatly reduced.

(2) Use high-precision assembly tooling to improve the assembly accuracy of weldments.

(3) The welding seam should be cleaned, free of debris such as oil stains, rust, welding slag, and cutting slag, and a solderable primer is allowed. Otherwise, it will affect the success rate of arc starting. Position welding is changed from electrode welding to gas shielded welding. At the same time, the spot welding part is polished to avoid slag shells or pores caused by the position welding, thereby avoiding the instability of the arc and even the generation of spatter.

Welding wire requirements

Welding manipulator can use barrel or disk welding wire according to need. In order to reduce the frequency of welding wire replacement, the manipulator should choose barreled welding wire, but due to the use of barreled welding wire, the wire feeding hose is very long, the resistance is large, and the quality requirements for the stiffness of the welding wire are high. When using copper wire with slightly poorer quality, the copper plating on the surface of the wire will reduce the internal volume of the catheter due to friction and shedding. When the wire is fed at high speed, the resistance will increase. Seam quality. In severe cases, the phenomenon of jamming occurs and the manipulator is shut down, so the welding wire conduit should be cleaned in time.

Welding Manipulator

Programming skills

(1) Choose a reasonable welding sequence. The welding sequence is formulated to reduce the welding deformation and the length of the welding gun-walking path.

(2) The space transition of the welding gun requires a short, smooth, and safe trajectory.

(3) Optimize welding parameters. In order to obtain the best welding parameters, make working test pieces for welding test and process qualification.

(4) Reasonable position of the positioner, the attitude of the welding gun, and position of the welding gun relative to the joint. After the workpiece is fixed on the positioner, if the welding seam is not the ideal position and angle, it is required to continuously adjust the positioner during programming, so that the welded weld reaches the horizontal position in sequence according to the welding sequence, and at the same time, the position of each axis of the robot must be continuously adjusted, Reasonably determine the position, angle and welding wire extension length of the welding gun relative to the joint. After the position of the workpiece is determined, it is difficult to observe the position of the welding gun relative to the joint through the programmer's eyes. This requires programmers to be good at summing up the accumulated experience.

(5) Insert the gun clearing procedure in time. After writing a welding program of a certain length, the gun cleaning program should be inserted in time to prevent the welding spatter from clogging the welding nozzle and the conductive nozzle, ensure the cleaning of the welding gun, increase the life of the nozzle, ensure reliable arc starting, and reduce welding spatter.

(6) The preparation of the program is generally not in one step. It is necessary to continuously check and modify the program during the welding process of the manipulator, adjust the welding parameters and the attitude of the welding gun, etc., to form a good program.

Operating costs and management

The price of imported manipulator parts is relatively high, and efforts should be made to reduce operating costs from all aspects. The welding process strengthens maintenance and improves the service life of consumable parts such as nozzles and conductive nozzles. In addition, preventive maintenance of the manipulator system can effectively increase the service life of components. High-quality management personnel, technicians, and operators are the necessary conditions for the robot to give full play to its efficiency. The use of welding robots in an enterprise is largely due to people, so we must ensure that there is a stable work team.

The application of welding manipulators in the manufacture of traction beams and bolster beams for electric locomotive car bodies greatly improve the welding quality stability and production efficiency of the products. The application of welding manipulators is a complex and comprehensive process, which puts forward new and stricter requirements on the design structure, welding process, component quality, and assembly quality of weldments. At the same time, the stability of the relevant staff also affects the quality of the application of the robot. It should continue to accumulate experience in the long-term application to maximize the benefits of the robot.