Application analysis and programming method of welding robot

Welding robot is an industrial robot engaged in welding (including cutting and spraying). It mainly includes two parts: robot and welding equipment. Among them, the robot is composed of the robot body and the control cabinet (hardware and software); while the welding equipment, taking arc welding and spot welding as examples, consists of a welding power source (including its control system), a wire feeder (arc welding), and a welding gun ( Clamp) and other parts. For smart robots, it should also be equipped with sensing systems, such as laser or camera sensors and their control devices.

1. Features of spot welding robot:

Since the integrated welding tongs are used and the welding transformer is installed behind the welding tongs, the transformer of the spot welding robot must be as small as possible. For transformers with smaller capacity, 50Hz power frequency AC can be used, and for transformers with larger capacity, the industry has begun to use inverter technology to change 50Hz power frequency AC into 600-700Hz AC, which reduces and reduces the size of the transformer. After voltage transformation, you can directly use 600-700Hz alternating current welding, or you can perform secondary rectification and direct current welding. The welding parameters are adjusted by the timer. At present, the new timer has been microcomputerized, so the robot control cabinet can directly control the timer without additional interfaces. The welding tongs of the spot welding robot use electric servo spot welding tongs. The opening and closing of the welding tongs are driven by a servo motor, and the encoder feedback, so that the opening degree of the welding tongs can be arbitrarily selected and preset according to actual needs. The pressing force can also be steplessly adjusted.

2. Problems and solutions in the application of welding robots:

(1) Welding deviation problem: It may be because the welding position is incorrect or there is a problem when looking for the welding gun. At this time, it is necessary to consider whether the TCP (position of the center point of the welding gun) is accurate and adjust it. If this happens frequently, check the zero position of each axis of the robot, and re-calibrate to correct it.

(2) Undercut problem: It may be improper selection of welding parameters, wrong welding gun angle or welding gun position, which can be adjusted appropriately.

(3) Porosity problem: Poor gas protection, too thick primer on the workpiece, or insufficient protection gas, which can be dealt with by adjusting accordingly.

(4) Excessive spattering problem: It may be due to improper selection of welding parameters, gas composition reasons, or too long outer elongation of the welding wire. You can adjust the power of the machine to change the welding parameters, and adjust the gas proportioner to adjust the mixed gas ratio. Adjust the relative position of the welding gun and the workpiece.

(5) An arc crater is formed after cooling at the end of the weld: When programmable, the submerged arc crater function can be added to the work step to fill it.

3. Features of arc welding robot:

Most arc welding robots use gas shielded welding methods (MAG, MIG, TIG), and the usual thyristor, inverter, waveform control, pulse or non-pulse welding power sources can be installed on the robot for arc welding. Since the robot control cabinet adopts digital control, and the welding power supply is mostly analog control, it is necessary to add an interface between the welding power supply and the control cabinet.

4. During the welding process, the common faults of the robot system:

(1) Gun collision: It may be due to deviations in the assembly of the workpiece or inaccurate TCP of the welding torch. You can check the assembly or correct the TCP of the welding torch.

(2) Arc failure occurs and the arc cannot be started: 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) Shielding gas monitoring alarm: there is a fault in the cooling water or shielding gas supply, check the cooling water or shielding gas pipeline.

5. Programming skills of welding robot:

(1) Choose a reasonable welding sequence, and formulate the welding sequence in order to reduce the welding deformation and the length of the welding path.

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

 (3) Insert the gun cleaning program in time. After writing a certain length of welding program, the gun cleaning program should be inserted in time to prevent welding spatter from blocking the welding nozzle and contact tip, ensure the cleaning of the welding gun, improve the life of the nozzle, and ensure reliable arc ignition. Reduce welding spatter.

(4) Use a reasonable position of the positioner, welding torch attitude, and the position of the welding torch 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 seam reaches the horizontal position successively according to the welding sequence. At the same time, it is necessary to continuously adjust the position of each axis of the robot, and reasonably determine the position and angle of the welding gun relative to the joint and the length of the welding wire. After the position of the workpiece is determined, the position of the welding gun relative to the joint must be observed by the programmer's eyes, which is more difficult. This requires programmers to be good at summing up experience.

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

(6) Generally, it is not possible to compile a program in one step. It is necessary to continuously inspect and modify the program during the robot welding process, adjust the welding parameters and the welding gun attitude, etc., to form a good program.