At present, China's industrial production has used a large number of robots, of which about 60% are used in welding production. There are also a wide range of departments and industries that can use robots for welding production, such as automobiles, motorcycles, engineering machinery, agricultural machinery, home appliances, etc.
At present, China's industrial production has used a large number of robots, of which about 60% are used in welding production. There are also a wide range of departments and industries that can use robots for welding production, such as automobiles, motorcycles, engineering machinery, agricultural machinery, home appliances, etc. Of course, the advantages of using arc welding robots are also very significant:
polystyrene foam or EPS packaging
â‘ Stabilize and improve product quality, and reduce rework or scrap rates.
â‘¡ Make the production system universal and facilitate product modification.
â‘¢ Improve labor productivity and reduce production costs.
â‘£ Improve the working environment and ensure production safety.
⑤ Reduce the level of proficiency in the type of work and no longer require each operator to be skilled in the type of work.
â‘¥ Solving the shortage of labor or skilled workers...etc.
Because of this, in addition to some large enterprises, more and more small and medium-sized enterprises also hope to introduce arc welding robots. To this end, we introduce some application examples of arc welding robots, introduce their system composition, system characteristics, welding process characteristics, introduction effects, etc., as well as other industry cases, in order to jointly promote the further improvement of the application level of China's arc welding robots.
Welding production of low-voltage electrical cabinet bodies
Low-voltage electrical cabinets are a widely used product in the electrical industry. The switch cabinet body is the component with the largest workload in the switch cabinet. There are about 80 to 100 welds in a cabinet, with a total length of about 2 meters. The cabinet is of medium size, making it ideal for completing welding work with a small robotic arc welding workstation. The welds on the cabinet are all straight, but the space layout is complex, the inner cavity is small and there are many parts. It can be seen that the selection of welding parameters for cabinet welding is not difficult. The key lies in:
â‘ Distribution of production processes.
â‘¡Design and manufacture of fixtures.
â‘¢Whether the production rhythm can meet the requirements.
1. System composition and system characteristics:
The system consists of an arc welding robot, a set of welding equipment, a positioner, a set of welding fixtures and ancillary equipment. The robot is a MOTOMAN SK6 robot produced by Yaskawa Electric of Japan. The robot has a grip weight of 6Kg and a movement range radius of 1325mm. The welding power source is an inverter welding machine produced by Japan's NASTOA Company, with a rated current of 350A. The positioner is a single-turn head and tail frame mechanism driven by an AC servo motor with an external axis function and can carry 350Kg. The clamp is an automatic clamp driven by a cylinder. The system also uses a set of gun cleaning and wire cutting equipment manufactured by the German BINZEL company to clean the welding gun. The system adopts manual loading and unloading and robot automatic welding. During the welding process, the positioner can be rotated arbitrarily with the robot to maintain the best welding posture of the weld seam and welding gun.
2. Product features and welding requirements:
The robot welding system is not an independent link in a production workshop. It is related to all its front and rear links, especially the production link that provides welding blanks. Because the robot uses teaching and reproduction to complete the action trajectory, its own repeated positioning accuracy is very high (±0.1). In this way, the accuracy of the workpiece affects the feasibility of robot welding. Robots require precise and consistent assembly of workpieces. If robots are provided with high-precision workpieces, high-quality welds can be produced quickly. In low-precision situations, welding can also be completed by adding tracking functions. But this will inevitably increase investment and reduce production efficiency.
In this example, all the steel plates of the switch cabinet are cut by laser, which can achieve high precision. But sometimes there are consistency problems, which are mainly caused by inaccurate positioning of the steel plate during blanking. When estimating the allowable workpiece deviation for robot welding, half the diameter of the welding wire is usually used as the standard. When this limit is exceeded, normal welding will not be possible. This deviation includes two aspects: the error of the workpiece itself and the positioning error of the fixture.
3. Arc welding robot jig design
Fixtures play a key role in robotic welding. The success or failure of many robot welding systems is also the success or failure of fixture design. Compared with manual welding fixtures, robot fixtures have completely different design ideas and methods. It is a highly professional job and requires special fields. rich experience.
1. The robot does not have the ability to judge. It meticulously performs the work taught by the programmer every time, which places high requirements on the accuracy of the fixture, not only to ensure the accuracy of the workpiece itself but also to ensure that the robot can function normally. Complete the welding job. Therefore, robot welding fixtures generally undergo strict accuracy testing. These are not the key to the problem. The key is how the fixture can avoid or reduce the negative impact of these errors on robot welding when the workpiece error is large, thereby avoiding the use of expensive welding seam tracking functions. For example, in the welding of low-voltage electrical cabinets, the width error of the large groove plate is 3.8mm, and the height error is 2.2mm. Such large errors cannot be tolerated by robot welding. For this reason, when discussing the plan with the user, it was proposed that the part cannot be completely welded, but one side can be welded and the remaining side can be repaired manually. In this way, when designing the fixture, one side is used for positioning, and the other side is positioned with an elastic stop to adapt to the positioning requirements of workpieces of different sizes.
2. Robots are far less flexible than humans, and robot automatic welding guns are larger than manual welding guns. Therefore, when designing fixtures, sufficient space and paths must be considered for the use of the welding guns. All welds on the workpiece should be checked. In order to obtain a good welding posture, the fixture should be as slender as possible. In order to ensure the reliability of the fixture, the fixture should be as strong and strong as possible. This is a contradiction. Sometimes It can be solved by sacrificing a certain welding posture, but it must undergo a welding test. There are some welds that cannot be completed by robots. This is determined by the characteristics of robot welding itself. As a user of a robot welding system, you should understand that the real meaning of using a robot is not to replace all human work, but to take advantage of its strengths and do the work it is good at. Only in this way can the role of the robot be fully utilized, otherwise it will do everything. , but the result is that it doesn’t work well.
3. Complex workpieces are best completed in several processes, so that on the one hand, the fixture can be simpler and more reliable, and on the other hand, it can also facilitate the free operation of the welding gun. When the automatic welding process is not arranged, a manual pre-welding process can be added to fix some parts first (equivalent to positioning and clamping at the same time), and then weld together with other parts. Pre-welded fixtures must also consider accuracy requirements.
4. Welding thermal deformation is the most difficult phenomenon to grasp during the welding process, and it also brings some new issues to fixture design. First of all, we must consider the user's allowable degree of workpiece deformation, and reduce welding deformation as much as possible by decomposing the welding process and improving the welding sequence. The problem of unloading the workpiece after welding should also be considered. Sometimes it is necessary to add a booster mechanism to eject the workpiece or pull out the positioning pin.
5. The design of automatic fixtures should also fully consider reducing the labor intensity of the operator and improving personal and equipment safety. The fixture should be able to automatically determine whether the clamping is in place, whether the workpiece is incorrect, whether the action sequence of each mechanism is correct, etc.
4. Production rhythm and productivity:
As robot manufacturers and system suppliers, we can generally estimate the production cycle based on user workpiece requirements, but in any case, this deviates from actual production. When production cycle time becomes an important factor, actual values ​​should be measured through experiments. Shortening the production cycle can improve productivity. For single-station production, the auxiliary time other than welding time has a direct impact on the production cycle, because during this period the robot can only wait. For systems with more than two stations, the impact of auxiliary time is much smaller, as long as the auxiliary time If the time does not exceed the welding operation time, it can be considered to have no impact, so the general system adopts the dual-station form.