Robotic arc welding is mainly used in automatic production of various auto parts, construction machinery and metal industries.
There are two types of arc welding robots: consumable welding and non-consumable welding. They have the characteristics of long-term welding, high productivity, high quality and high stability.
With the development of technology, arc welding robots are using machine vision and cloud data to develop towards intelligence.
1 System composition
The general arc welding robot system is composed of the following parts:
1. Robots
2. Automatic wire feeding device
3. Welding power supply
4. Welding gun
5. Positioner
6. Fixture
The system composition can also selectively expand the following devices according to different welding methods and different welding process requirements of specific workpieces to be welded:
1. Gun cleaning and thread cutting device
2. Cooling water tank
3. Flux transfer and recovery device (at SAW)
4. Mobile device
5. Welding positioner
6. Sensing device
7. Dust removal device and weld detection equipment
The following is a standard robot arc welding workstation
2 Three welding methods
1. Gas shielded arc welding:
Argon arc welding using argon as the shielding gas in the welding area and carbon dioxide arc welding using carbon dioxide as the shielding gas in the welding area are all gas shielded arc welding.
The basic principle is that when welding with the arc as the heat source, the protective gas is continuously sprayed from the nozzle of the spray gun to isolate the air from the molten metal in the welding area, so as to protect the liquid metal in the arc and welding pool from the pollution of oxygen, nitrogen, hydrogen, etc. in the atmosphere, so as to improve the welding quality.
2. TIG welding:
The metal tungsten rod with high melting point is used as an electrode to generate electric arc during welding and is also used for arc welding under argon protection. It is often used for welding of stainless steel, superalloy and other strict requirements.
3. Plasma arc welding:
A welding method developed from tungsten argon arc welding. Plasma arc is a kind of high temperature ion gas stream generated by ionization of ion gas, which is sprayed from the nozzle hole and compressed to form a slender arc column, which is higher than the conventional free arc, such as argon arc welding, which is only up to 5000-8000K. Plasma arc has a wide range of applications in the welding field because of its slender arc column and high energy density.
3 Three kinds of gas shielded welding
Arc welding robots mostly use gas shielded welding methods (MAG, MIG, TIG). The conventional welding power sources such as thyristor type, inverter type, waveform control type, pulse or non-pulse type can be installed on the robot for arc welding. Since the robot control cabinet adopts digital control, while the welding power supply is mostly analog control, 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 supporting welding equipment, which has been seeded with corresponding interface boards, so there is no additional interface box in the arc welding robot system above.
It should be pointed out that the arc time accounts for a large proportion in the work cycle of the arc welding robot. Therefore, when selecting the welding power supply, the capacity of the power supply should generally be determined according to the duration of 100%.
1. MIG welding (GMAW):
This welding method uses the burning arc between the continuously fed welding wire and the workpiece as the heat source, and the gas from the welding torch nozzle protects the arc for welding. The inert gas is generally argon.
2. TIG welding (inert gas tungsten arc welding):
The heat source of TIG welding is DC arc, the working voltage is 10-15V, but the current can reach 300A. The workpiece is used as the positive electrode, and the tungsten electrode in the welding torch is used as the negative electrode. The inert gas is generally argon.
3. MAG welding (GMAW):
MIG welding uses a certain amount of active gases, such as O2 and CO2, to be added into the inert gas as the shielding gas.
4 Arc welding system description
The arc welding process is much more complex than the spot welding process. The tool center point (TCP), that is, the movement track of the welding wire end, the welding gun attitude, and the welding parameters all require accurate control. Therefore, in addition to the general functions mentioned above, the robot for arc welding must also have some functions suitable for the requirements of arc welding.
Theoretically, a 5-axis robot can be used for arc welding, but it is difficult to use a 5-axis robot for complex shape welds. Therefore, unless the weld is relatively simple, 6-axis robot should be selected as far as possible.
When the arc welding robot performs zigzag corner welding or small-diameter round weld welding, its track should be close to the teaching track, and it should also have software functions of different swing styles for selection during programming, so as to perform swing welding, and the robot should also automatically stop moving forward at the pause point in each cycle to meet the process requirements. In addition, it shall also have the functions of contact locating, automatic finding the starting position of weld, arc tracking and automatic re-ignition.
5 Arc welding current during commissioning
Judgment of arc welding current during commissioning:
1. Low current:
Narrow weld bead, shallow penetration, easy to form too high, incomplete fusion, incomplete penetration, slag inclusion, air hole, electrode adhesion, arc break, no arc strike, etc;
2. High current:
Wide weld bead, large penetration, undercut, burnthrough, shrinkage, large spatter, overburning, large deformation, weld beading, etc.