Summary of the hottest spot welding equipment for

2022-09-19
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Summary of automobile body spot welding equipment

resistance welding has the characteristics of using internal heat source, heat concentration, small heat affected zone, small product deformation, obtaining better surface processing quality, easy operation, and no use of additional welding consumables, which makes it one of the most commonly used welding methods with stable welding quality, high production efficiency, and easy to realize automatic mass production. It is widely used in automotive vehicles, aerospace Household appliances, steel furniture, transportation facilities, thin-walled containers, auto parts and other manufacturing fields, especially in recent years, the rapid development of China's automotive industry has led to the continuous increase in the application of resistance welding, and the output of resistance welding machines in China has increased significantly year by year. The annual output of resistance welding machines has jumped from thousands of sets a few years ago to tens of thousands in recent years

the application of resistance welding machine in the automotive industry is mainly to use resistance heat to melt the metal to form welding spots at the lap joint of the stamping thin plate body covering parts, so as to connect the welding parts as a whole. The welding points of a car body are about 3500~5000 points. Spot welding of automobile body is one of the main forms of resistance welding. The spot welding equipment used for automobile body welding accounts for more than 90% of all resistance welding products

there are three main types of spot welding machines used for automobile body welding:

ordinary spot welding machines, multi spot welding machines and spot welding robots

ordinary spot welding machine is a general spot welding equipment suitable for all kinds of occasions and welding objects, and it is also the main equipment constituting the automatic production line of automobile welding. According to its annual production program and annual output of automobiles, each automatic production line of automobile welding requires dozens to hundreds of ordinary spot welders. Ordinary spot welding machines are divided into mobile spot welding machines and fixed spot welding machines according to different machine structures and applications; According to their different structures, mobile spot welding machines are divided into hanging spot welding machines and portable spot welding machines

multi spot welding machine is a special welding equipment designed and manufactured for welding specific workpieces. Its advantage is high production efficiency, suitable for large-scale single variety production, and suitable for welding workpieces with complex structural shape, dense welding points, small joint overlap, difficult operation, difficult welding quality assurance and other factors. Its disadvantage is that the equipment has a lot of investment and strong specificity, which will be gradually replaced by the combination of welding robots and corresponding tooling fixtures. In addition to welding various vehicle components, multi-point welding machines are also used in the manufacturing industry of various thin metal components such as household appliances such as refrigerators, washing machines, steel furniture, transportation facilities, panel radiators and so on

robots have gradually risen to the leading position in the international and Shandong new material industry system. In recent years, the development speed has been accelerating, the application fields are becoming wider and wider, new technologies are constantly adopted, and the number of robots is increasing. Robots used in automobile factories are mainly used for handling, welding, coating and assembly. The level and number of robots used in the four processes of stamping, welding, painting and final assembly in the automobile factory represent the automation and modernization level of the factory. It is not uncommon for all robot operated automobile factories in foreign countries to gradually become the mainstream, which will also be the inevitable product and development direction of the development of the domestic automobile industry to a certain stage. The application robot can not only carry out complex process operations, adapt to the harsh working environment, replace heavy, monotonous and repetitive manual labor, ensure product quality, improve work efficiency, save energy, work safely, and eliminate all human factors affecting product quality, but also quickly form a flexible production system, which is especially suitable for new product development and multi variety production needs. The product has the advantages of fast model change, short cycle, and strong adaptability

no matter what type of spot welding machine, its structure is composed of three parts: power supply and control device (welding resistance controller), energy conversion device (welding transformer) and welding actuator (welding tongs or welding guns). The main difference between the three types of spot welding machines mentioned above is that the welding actuator is different. Ordinary spot welding machine is used by workers holding spot welding tongs to weld the workpiece point by point. As the name suggests, multi spot welding machine is welded by multiple spot welding guns installed on various forms of racks at the same time. Spot welding robot simulates manual action and uses spot welding tongs installed on mechanical arm to weld the workpiece

the development of modern resistance welding technology and process puts forward higher requirements for resistance welding controller, which cannot be realized without electronic computer. After the development of discrete components and integrated circuits, the control circuit of solder mask controller has developed to the stage of single-chip microcomputer. The application of computer makes the function of resistance welding controller more powerful, the performance more perfect and the reliability further improved

modern resistance welding controller should have the following functions:

1) reliably control the resistance welding machine to turn on and off the power supply

2) welding current is accurately adjustable

3) the welding time is accurate and adjustable without error

4) it can realize the simple or complex cycle of each part of the welding process

5) be able to store multiple sets of welding specifications

6) it can produce a variety of welding current waveforms

7) it has the function of multiple energization (multi pulse welding)

8) it has the function of closed-loop control of electrode pressure

9) it has the functions of fault self diagnosis, alarm and display as much as possible

10) it can realize welding quality monitoring

resistance welding quality monitoring includes two aspects: real-time stabilization of welding parameters and reflection of welding spot status. The realization of resistance welding quality monitoring is of great significance to improve the reliability of welding joints and ensure welding quality

at present, the quality monitoring method adopted by the resistance welding controller is mainly to implement constant current control on the basis of power supply voltage compensation. Constant current control is a simple, reliable and easy to implement method. By comparing the current sampling (usually the primary current) with the given value, and by adjusting the conduction angle of the main power switch - thyristor, the input voltage of the welding transformer is adjusted to ensure the constant secondary current. Constant current control can stabilize the welding current when the power supply voltage fluctuates and the welding loop impedance changes, so as to keep the size of the nugget consistent and ensure the welding quality. However, it only controls the constant current of the welding circuit, not the constant current forming the solder joint. Therefore, this method cannot overcome the factors affecting the current density, such as current shunt, electrode wear, etc. Due to the abnormal current detected by constant current monitoring, the welding speed may be affected when the welding current is compensated. For multi spot welding machine and spot welding robot controlled by program, abnormal current may lead to program error

in addition to constant current control, dynamic resistance monitoring, thermal expansion monitoring, ultrasonic monitoring, infrared monitoring and other monitoring methods are used in products

dynamic resistance refers to the rule of resistance change during the heating and cooling process of the solder joint, which can better reflect the formation process of the solder joint nugget, and can sensitively reflect the surface state of the weldment, the change of material thickness, current shunt and the change of power supply voltage. It can be calculated by measuring the welding current and the voltage between electrodes. Similarly, the energy forming the solder joint - the product of the welding current and the voltage between the electrodes can also be used as monitoring information

the resistance welding controller should also have many functions, such as self-adaptive power factor, automatic compensation of electrode wear welding current, electrode update alarm, convenient Chinese menu programming and so on. There is a group control interface, which is convenient for communication between welding machines and centralized management of welding machines. The use of upper computer and centralized control manager can realize the connection and centralized management of dozens or even hundreds of controllers

at present, the resistance welding machine widely used is mainly single-phase AC power frequency welding machine, which is a kind of large capacity electrical equipment. The main power switch - thyristor turns on and off 50 Hz AC, and the welding transformer converts the electric energy into low-voltage phenolic insulation board voltage, several to twenty volts; High current, the commonly used car body welding current is about 8000 to 15000 a; The welding current required for chassis and some parts is even higher. Although it is necessary to install the welding machine on the three-phase power supply in a balanced way, the uncertainty of the equipment operation cannot guarantee the balanced power consumption of the three-phase power supply; When multiple welding machines are powered on at the same time, the voltage will be greatly reduced, the power factor will be reduced, and the welding quality will be affected; The nonlinearity of thyristor components makes the sine wave waveform of power supply seriously distorted, resulting in electromagnetic interference. In addition, more than 90% of the energy of single-phase AC resistance welding machine, especially the split suspension spot welding machine, is consumed in the welding circuit (mainly water welding cable), and the energy utilization rate is extremely low. Therefore, single-phase AC power frequency resistance welding power supply is not an ideal power supply, whether from the perspective of energy conservation or electrical balance, or from the perspective of welding quality and applicability to materials

from the perspective of development, the control technology of power frequency resistance welding has not made major breakthroughs in the past one or two decades, and it still stays in the early control technologies such as constant current control and constant voltage control. For example, constant power (or constant heat) control, due to the low speed of power frequency control (cycle order, 20ms/cycle), has not achieved good application results. Although dynamic resistance monitoring is an ideal quality monitoring method, due to the complexity of its sampling sensor and some unsuitable material limitations, such as the flat resistance curve of stainless steel plate, it has not been widely promoted in production, and only a few products are used in the welding of aerospace vehicles. Therefore, the research on resistance welding control technology should focus on new products such as inverter resistance welding machine and robot welding tongs

in the research of power frequency welding resistance controller, in addition to welding quality monitoring, we should also work hard on some useful self inspection and protection functions as well as reliability, mainly including:

1) electrode adhesion detection function, which is a necessary function for robot welding tongs control, multi spot welding machines and automatic welding machines

2) when the welding transformer breaks down, the air switch will trip automatically, which is related to personal safety

mobile spot welding machine is the main equipment to complete the assembly and welding task of automobile body on the automatic production line of automobile body welding. It is suitable for welding weldments and large thin-wall structural workpieces with large structural size, complex shape and inconvenient to move. The suspended spot welding machine in the mobile spot welding machine is divided into two structural forms. One is the split suspended spot welding machine in which the resistance welding controller and the welding transformer are arranged separately, and the controller and the welding transformer are electrically connected by soft cables. China's early products introduced from the Soviet Union, Japan and other countries and China's products in the 1990s are mainly based on this. The other is a one-piece suspension spot welding machine, which integrates the welding resistance controller and the welding transformer, and the whole machine has a compact and reasonable structure; Save space, installation materials and power pipes, and operate the controller conveniently; This type of welding machine is used in European and American countries, and it is also the leading product of mobile spot welding machine in China at present. The welding actuators of the two welding machines are exactly the same. The welding current is transmitted by the welding tongs at the connection point of the water welding cable. Usually, two welding tongs are equipped to work in turn. The utility model has the advantages of flexible and convenient operation and various forms of welding tongs. The disadvantages are long welding circuit, high impedance, low power factor and large power loss; At the same time, due to the frequent twisted use of the water welding cable under the condition of high current, the water welding cable becomes

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