With the rising labor costs in the manufacturing industry and the continuous decline in robot product prices, people are increasingly pursuing more comfortable working conditions, and the application of robots is increasing every year.

Industrial robots consist of an operating machine (mechanical body), a controller, a servo drive system, and a detection sensing device. They are a type of electromechanical integrated automation production equipment that simulates human operation, automatic control, repeatable programming, and can complete various tasks in three-dimensional space. They are particularly suitable for flexible production with multiple varieties and variable batch sizes. It plays a crucial role in stabilizing, improving product quality, enhancing production efficiency, improving working conditions, and facilitating rapid product updates.

Since the early 1960s, when humans created * industrial robots, industrial robots have shown great vitality. In just over 40 years, industrial robot technology has developed rapidly, and industrial robots have been widely used in production in industrialized countries. At present, industrial robots have been widely used in fields such as automotive and automotive parts manufacturing, mechanical processing, electronics and electrical industry, rubber and plastic industry, food industry, wood and furniture manufacturing, etc. In industrial production, industrial robots such as welding robots, assembly robots, spraying robots, and handling robots have been widely adopted. This article focuses on introducing welding robots.

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

1. Characteristics of spot welding robots

Due to the use of integrated welding tongs, the welding transformer is installed behind the welding tongs, so the transformer of the spot welding robot must be minimized as much as possible. For transformers with smaller capacity, 50Hz AC can be used, while for transformers with larger capacity, the industry has begun to use inverter technology to convert 50Hz AC into 600-700Hz AC, reducing the volume and weight of the transformer. After transformation, it can be directly welded with 600-700Hz AC power, or it can be rectified again and welded with DC power. The welding parameters are adjusted by a timer. At present, the new timer has been computerized, so the robot control cabinet can directly control the timer without the need for additional interfaces. The welding tongs of spot welding robots use electric servo point welding tongs. The opening and closing of the welding tongs are driven by servo motors and feedback from the encoder, allowing the opening degree of the welding tongs to be selected and preset according to actual needs, and the clamping force between the electrodes can also be infinitely adjusted.

Electric servo spot welding tongs have the following advantages:

(1) The welding cycle of each welding point can be significantly reduced because the opening degree of the welding tongs is controlled by the robot. During the movement of the robot between points, the welding tongs can start to close; After welding a little bit, the welding tongs can be opened while the robot moves, without waiting for the robot to be in place before closing or opening before the robot moves.

(2) The opening degree of the welding tongs can be adjusted according to the condition of the workpiece. As long as there is no collision or interference, the opening degree can be minimized as much as possible to save the opening degree of the welding tongs and the time required for opening and closing the welding tongs.

(3) When the welding tongs are closed and pressurized, not only can the pressure be adjusted, but also the two electrodes are gently closed during closure, which can reduce impact deformation and noise.

　　

2. Characteristics of arc welding robots

Arc welding robots often use gas shielded welding methods (MAG, MIG, TIG), and commonly used welding power sources such as thyristor, inverter, waveform control, pulse or non pulse can be installed on the robot for arc welding. Due to the use of digital control in the robot control cabinet and analog control in the welding power supply, an interface needs to be added between the welding power supply and the control cabinet.

In recent years, foreign robot manufacturers have their own specific welding equipment, and corresponding interface boards have been inserted into these welding equipment, so there is no additional interface box in the arc welding robot system. It should be pointed out that in the working cycle of arc welding robots, the proportion of arc time is relatively large. Therefore, when selecting a welding power source, the capacity of the power source should generally be determined based on a 100% duration rate. The wire feeding mechanism can be installed on the upper arm of the robot or placed outside the robot. The former has a shorter hose between the welding gun and the wire feeding machine, which is conducive to maintaining the stability of wire feeding, while the latter has a longer hose. When the robot sends the welding gun to certain positions, causing the hose to be in a bent state, it will seriously affect the quality of wire feeding. Therefore, the installation method of the wire feeding machine must consider ensuring the stability of wire feeding.

　　

3. Problems and Solutions in the Application of Welding Robots

(1) Welding deviation issue: It may be due to incorrect welding position or problems finding the welding gun. At this point, it is necessary to consider whether the TCP (center point position of the welding gun) is accurate and make adjustments accordingly. If this situation occurs frequently, it is necessary to check the zero position of each axis of the robot and recalibrate it for correction.

(2) Edge biting problem: It may be due to improper selection of welding parameters, incorrect welding gun angle or welding gun position, which can be adjusted appropriately.

(3) Pore problem: It may be due to poor gas protection, thick primer on the workpiece, or insufficient drying of the protective gas. Corresponding adjustments can be made to deal with it.

(4) Excessive spatter problem: It may be due to improper selection of welding parameters, gas composition reasons, or excessive wire extension length. The machine power can be adjusted appropriately to change the welding parameters, the gas proportioner can be adjusted to adjust the mixed gas ratio, and the relative position between the welding gun and the workpiece can be adjusted.

(5) The problem of forming an arc pit at the end of the weld after cooling: When programmable, adding a buried arc pit function in the work step can fill it up.

　　

4. Common faults in robot systems during welding process

(1) Gun collision: It may be due to deviation in workpiece assembly or inaccurate TCP of the welding gun. The assembly situation can be checked or the TCP of the welding gun can be corrected.

(2) Arc failure occurs, unable to initiate arc: It may be due to the welding wire not contacting the workpiece or the process parameters being too small. Manual wire feeding can be used to adjust the distance between the welding gun and the weld seam, or adjust the process parameters appropriately.

(3) Protective gas monitoring alarm: There is a malfunction in the supply of cooling water or protective gas. Check the cooling water or protective gas pipeline.

　　

5. Programming skills for welding robots

(1) Choose a reasonable welding sequence to reduce welding deformation and the length of the welding gun walking path to formulate the welding sequence.

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

(3) Optimize welding parameters, in order to obtain welding parameters, make working specimens for welding tests and process evaluation.

(4) Adopt reasonable positioning of the positioner, welding gun posture, and relative position of the welding gun to the joint. After the workpiece is fixed on the positioner, if the weld seam is not in the ideal position and angle, it is required to continuously adjust the positioner during programming so that the welded seam reaches the horizontal position in the welding sequence step by step. At the same time, it is necessary to continuously adjust the position of each axis of the robot, reasonably determine the position, angle, and wire extension length of the welding gun relative to the joint. After determining the position of the workpiece, the position of the welding gun relative to the joint must be observed through the programmer's eyes, which is quite difficult. This requires programmers to be good at summarizing and accumulating experience.

(5) Insert the gun cleaning program in a timely manner. After writing a welding program of a certain length, the gun cleaning program should be inserted in a timely manner to prevent welding spatter from blocking the welding nozzle and conductive nozzle, ensure the cleanliness of the welding gun, improve the life of the nozzle, ensure reliable arc ignition, and reduce welding spatter.

(6) Programming generally cannot be done in one step. It requires continuous inspection and modification of the program during the robot welding process, adjustment of welding parameters and welding gun posture, etc., in order to form a good program.