Chery's technology as one of the highlights, laser brazing technique Chery A5 series models of welding production line applications to improve work efficiency, reduce production costs, to achieve the perfect body welding appearance.

Significant advantage of laser welding

In the automotive industry, the resistance spot welding is the most commonly used method, but the process there is a large weld spatter, electrode life is short, take the side of a large amount of stitched and other difficult issues, and CO2 welding, MIG welding, copper brazing and other Welding Electrodes Manufacturer methods greatly influenced by the current and voltage, stability is difficult to obtain reliable guarantee.

In recent years, laser welding as a high-quality, high precision, low distortion, high efficiency and high speed welding, machining and metal materials is becoming an important means of manufacturing, more and more widely used in automobile manufacturing.

Laser welding is a high-intensity laser beam radiation to the metal surface by laser interaction with metal, the metal can absorb the laser light into heat after cooling crystallization of molten metal welding. In practical engineering applications, the advantage lies in the following areas:

(1) laser beam of the laser focus spot small, high power density, can be welded some of the high melting point, high strength alloy material;

(2) high degree of automation, welding speed, high efficiency, can easily make any complex shape of the weld;

(3) heat affected zone is small, the material deformation is small, without follow-up treatment processes;

(4) easy to guide the laser beam, focused to achieve the direction of the change;

(5) high efficiency, stable and reliable processing quality, economic and social good.

Of course, compared with conventional welding methods, laser welding equipment is expensive, one-time investment is large, high technical requirements, current application in our industry is still quite limited, but high production efficiency and ease of automatic control and other significant features that its very suitable for mass production lines and flexible manufacturing, our company has been in the A5 series models welding production line using laser welding technology, its successful application has been showing its features and advantages.

Welding process
A5 series here in my company car trunk lid outer panel sub-assembly laser brazing process as an example of the advantages of laser welding and value.

A5 series models of the body welding panels using cold-rolled carbon steel plate (thickness 0.8 ~ 1mm), brazing wire used φ1.2mm silicon bronze alloy wire (CuSi3).

Main welding process is: focusing the laser beam generator, the first radiation emitted on the surface of the wire, welding wire heated to temperatures sufficient to melt the metal melt, melt into the cracks between the pieces of the next panel, in a suitable laser heating conditions , between the melt and the plates can form a good metallurgical bonding brazing layer, to achieve a good connection, and the panels themselves are not high-temperature laser ablation of serious injury. Process shown in Figure 1.
Laser soldering system components

I am using a laser soldering system from the master PLC, laser welding robots, fixtures, laser control systems, laser generator, circulating water cooler and wire agencies and other components (see Figure 2), where the master PLC responsible for laser welding robots, the communication between the fixture and the whole system and coordination of security, the robot is the master laser generator, circulating water cooler, wire communication between agencies, to work together.
(1) the master PLC

The system uses the master PLC SIEMENS-S7-300, CPU is 315-2DP. S7-300 is a small modular PLC system that can meet the performance requirements of the application medium, characterized by a modular, easy to implement distributed control, easy-to-user control, and control task is increased when the free expansion.

(2) laser welding robot

The system uses the FANUC-M710i industrial robots, control cabinet model R-J3Ib, with a new generation AC servo motor and 32-bit microprocessor-based intelligent controller. Built-in sealing tools utility function, according to robot speed real-time adjustment of laser power and wire feed speed. With RS232, ModelA / B, ProcessI / O and communication interfaces such as Profibus.

(3) Fixture

Fixture system, developed by the Japanese FUJI by master PLC control, with sufficient assembly, welding space, does not affect the quality of welding operations and processes observed, without prejudice to the weldment handling, with good manufacturing processes and high mechanical efficiency. Positioning components and clamping mechanism are using generic, standardized parts. Laser welding robot and fixture shown in Figure 3.
(4) laser generator

TRUMPF's use of the German model HL3006D of Nd: YAG laser generator (see Figure 4), work by the YAG crystal material, light source and the pump cavity with a maximum output power of 3kW, rated input power of 98kW. In practice, the laser energy part of the wire used for melt, part of the preheated workpiece to ensure melting of the wire in the base material has a good spreading to form a uniform appearance of the weld.
(5) circulating water cooler

Use of recycled water in Japan ORION cooler for cooling the laser generator. Three-loop cooling method: pure water, industrial circulating cooling water, pure water, cooling water, water cooled laser generator, laser generator to ensure the temperature control system is about 180 ℃.

(6) wire feeder

The agency as a laser robot slaves, mainly with laser robot has three digital and one analog signal communication, are located in wire devices CON5 interfaces, CON7 interface and CON2 the interface.
Engineering Applications
In laser welding filler wire link, the manufacturer's recommended parameters of the theory is the focus in the wire, 2mm above the surface, so that 80% of the beam irradiation on the wire, 20% of the beam irradiation in the vicinity of panels, but the actual system application process but there are some problems, we promptly adjusted and repeated tests, the final focus of the laser set at 12mm at the top of the workpiece, the wire close to the plates into the workpiece on the spot diameter of about 3mm, wire diameter of 1.2mm. As the spot diameter of about 3mm, thus spreading the solder to be bound by the range of about 3mm in width. Taking into account the actual needs of the welding speed and weld deposited the amount of molten solder filling, suitable wire feed speed matching the appropriate laser power and beam diameter is necessary.
Integrated production reality, the larger the larger the power with the wire feed speed can be welded, but the greater heat input will result in a serious knee panels deformation effects A5 series models trunk lid outer panel surface quality. Therefore, stiffness of the workpiece itself is less the case that only by reducing the heat input to control the deformation of the workpiece. However, the smaller the amount of heat input with the lower bound to the wire feed speed, the consequences are too few of the deposited molten solder and inadequate warm-up panels, this will directly result in an incomplete and poor weld the shape. The issues are equipment manufacturers and our technical staff repeated debugging, and finally a successful test of a reasonable Welding Electrode Materials parameters, welding and brazing sheet metal contact at full spreading, uniform and beautiful solid weld to meet the final appearance quality requirements. Different parameters of the actual welding effect as shown in the table.
Conclusion
Laser brazing is the expansion of conventional laser welding, laser welding can reduce the precision clamping of joints, laser power, laser focus on the stringent performance requirements, while improving the performance of welding metallurgy, welding of dissimilar materials to achieve, it is also very use of space, but also with industrial robot welding cell composed of flexible, more conducive to all-position welding seam.
The rapid development of automobile industry require auto manufacturers to improve production while improving manufacturing quality, and thus the main car factory production lines are fully automated to the direction of gradual development, body welding line is no exception. Laser welding technology is being developed to meet this demand, not only automated, so that a substantial increase in production efficiency, and achieve a high quality of welding to achieve a perfect body appearance, enhance the brand of automobile industry also plays an important the role.