With the development of electronic technology, computer technology, numerical control technology and robot technology, the automatic arc welding robot workstation has become increasingly mature since it was used in production in the 1960s, and has the following advantages:
1) to stabilize and improve the welding quality;
2) improve labor productivity;
3) Improve the labor intensity of workers, and they can work in harmful environment;
4) The requirements for workers' operation technology are reduced;
5) Shorten the preparation period of product upgrade and reduce the corresponding equipment investment.
So it has been widely used in all walks of life.
form
Welding robots mainly include robots and welding equipment. A robot consists of a robot body and a control cabinet (hardware and software). Welding equipment, such as arc welding and spot welding, consists of welding power supply (including its control system), wire feeder (arc welding), welding gun (pliers) and so on. Intelligent robots should also have sensing systems, such as laser or camera sensors and their control devices.
Structural form and performance
The welding robots produced in the world are basically articulated robots, and most of them are six-axis. Among them, 1, 2 and 3 axes can send the end tool to different spatial positions, while 4, 5 and 6 axes can meet the different requirements of tool posture. There are two main forms of mechanical structure of welding robot body: one is parallelogram structure, and the other is side (pendulum) structure. The main advantage of the side (pendulum) structure is that the upper and lower arms have a large range of motion, making the workspace of the robot almost a sphere. Therefore, this robot can work upside down on the frame, saving floor space and facilitating the flow of ground objects. However, the second and third axes of this lateral robot are cantilever structures, which reduces the rigidity of the robot. Generally suitable for robots with small load, used for arc welding, cutting or spraying. The upper arm of the parallelogram robot is driven by a pull rod. The pull rod and the lower arm form two sides of a parallelogram. Hence the name. The workspace of the parallelogram robot developed in the early days is relatively small (confined to the front of the robot), so it is difficult to do handstand work. However, a new type of parallelogram robot (parallel robot) developed since the late 1980s can extend the workspace to the top, back and bottom of the robot, and there is no problem of measuring the stiffness of the robot, so it has attracted widespread attention. This structure is not only suitable for light robots, but also for heavy robots. In recent years, the robots used for spot welding (load 100 ~ 150 kg) are mostly parallelogram robots.
The axes of the above two robots are in rotary motion, so servo motors are used to drive them through cycloidal pinwheel (RV) reducer (1 ~ 3 axis) and harmonic reducer (1 ~ 6 axis). Before the mid-1980s, DC servo motors were used in electric robots. Since the late 1980s, countries have switched to AC servo motors. Because the AC motor has no carbon brush and good dynamic characteristics, the new robot not only has low accident rate, but also greatly increases the maintenance-free time and accelerates (decelerates) quickly. The load of some new light robots is below 16kg, and the maximum moving speed of the tool center point (TCP) can reach more than 3m/s, with accurate positioning and small vibration. At the same time, the control cabinet of the robot has been changed to a 32-bit microcomputer and a new algorithm, which makes it have the function of path self-optimization and the running trajectory is closer to the teaching trajectory.
Characteristics of spot welding robot Basic functions of spot welding robot
The requirements of spot welding for welding robots are not very high. Because spot welding only needs point control, there is no strict requirement on the moving trajectory of the electrode holder between points, which is why the robot can only be used for spot welding at the earliest. The spot welding robot should not only have enough load capacity, but also be fast, stable and accurate when moving from one point to another, so as to reduce the moving time and improve the speed. High working efficiency. How much load capacity the spot welding robot needs depends on the type of electrode holder used. For the electrode holder separated from the transformer, a robot with a load of 30 ~ 45 kg is enough. However, on the one hand, this kind of electrode holder is not conducive to the robot to extend the electrode holder into the workpiece for welding because of the long secondary cable and high power consumption; On the other hand, the cable keeps swinging with the movement of the robot, and the cable is quickly damaged. Therefore, the number of integrated electrode holders is increasing gradually. The mass of this electrode holder and transformer is about 70kg. Considering that the robot should have enough load capacity and can send the electrode holder to the space for welding at a large acceleration, the heavy robot with load of 100 ~ 150 kg is generally selected. In order to meet the requirement of short distance and fast movement of electrode holder in continuous spot welding. The new heavy robot has the function of completing 50mm displacement in 0.3s, which puts forward higher requirements for the performance of the motor, the operation speed and algorithm of the microcomputer.
Welding equipment of spot welding robot
The welding equipment of spot welding robot adopts integrated electrode holder, and the welding transformer is installed behind the electrode holder, so the transformer must be miniaturized as much as possible. For small-capacity transformers, 50Hz power frequency alternating current can be used, while for large-capacity transformers, inverter technology has been used to change 50Hz power frequency alternating current into 600 ~ 700 Hz alternating current to reduce and lighten the volume of transformers. After modification, it can be welded directly with 600 ~ 700 Hz alternating current, or with DC after secondary rectification. Welding parameters are adjusted by timer. The new timer has been computerized, so the robot control cabinet can directly control the timer without additional interface. The electrode holder of spot welding robot generally adopts pneumatic electrode holder, and the opening between two electrodes of pneumatic electrode holder generally has only two strokes. Moreover, once the electrode pressure is set, it cannot be changed at will. In recent years, a new type of electric servo spot welder has appeared. The opening and closing of the electrode holder is driven by the servo motor and fed back by the encoder. The opening of the electrode holder can be arbitrarily selected and preset according to the actual needs. And the pressure between the electrodes can be adjusted steplessly. This new type of electric servo spot welding pliers has the following advantages:
1) The welding cycle of each solder joint can be greatly shortened, because the opening of the electrode holder is precisely controlled by the robot, and the electrode holder can be closed when the robot moves from one point to another; With a little welding, the electrode holder opens and the robot can move at the same time. There is no need to wait until the robot is in place before the electrode holder is closed, or the robot moves after the electrode holder is fully opened.
2) The opening of the electrode holder can be adjusted at will according to the situation of the workpiece, as long as the opening is reduced as far as possible without collision and interference, the opening of the electrode holder can be saved, and the time occupied by the opening and closing of the electrode holder can be saved.
3) When the electrode holder is closed and pressurized, not only can the pressure be adjusted, but also the two electrodes are slightly closed when closed, thus reducing impact deformation and noise.
Million car purchase subsidy