Arc welding robots are industrial robots used for automatic arc welding. Their composition and principle are basically the same as those of spot welding robots. In the mid-1980s, Professors Cai Hegao and Wu Lin of Harbin Institute of Technology developed China's first arc welding robot - Huayu-I type arc welding robot.
Arc welding robots are mainly used in the welding production of various automotive parts. In this field, international manufacturers of large arc welding robots primarily supply unit products to complete equipment suppliers.
A typical arc welding robot consists of a teach pendant, control panel, robot body, automatic wire feeder, and welding power source. It can achieve continuous trajectory control and point-to-point control under computer control. It can also utilize linear and circular interpolation functions to weld spatial welds composed of straight lines and arcs. Arc welding robots mainly operate in two types: consumable electrode welding and non-consumable electrode welding. They are characterized by the ability to perform welding operations for extended periods, ensuring high productivity, high quality, and high stability. With technological advancements, arc welding robots are developing towards intelligentization.
The basic components of an arc welding robot system are: robot body, control system, teach pendant, welding power source, welding torch, welding fixture, and safety protection facilities.
Depending on the welding method and the specific welding process requirements of the workpiece, the system composition can be selectively expanded with the following devices: wire feeder, torch cleaning and wire cutting device, cooling water tank, flux conveying and recovery device (for SAW), moving device, welding positioner, sensing device, dust removal device, etc.
Features of arc welding robots
Arc welding robots mainly fall into two categories: consumable electrode welding and non-consumable electrode welding. They are characterized by their ability to perform welding operations continuously, ensuring high productivity, high quality, and high stability. Their processes are more complex than those of spot welding robots, requiring precise control of the tool center point (TCP), the trajectory of the welding wire tip, the welding torch posture, and welding parameters. Therefore, arc welding robots must also possess certain functions suitable for arc welding requirements.
While theoretically a 5-axis robot can be used for arc welding, it presents challenges for complex weld shapes. Therefore, unless the weld is relatively simple, a 6-axis robot should be used whenever possible.
When performing zigzag corner welding or small-diameter circular welds, the arc welding robot's trajectory should closely match the taught trajectory. Furthermore, it should have software functionality for different oscillation patterns, selectable during programming for oscillating welding. At the pause point in each cycle, the robot should automatically stop its forward movement to meet process requirements. In addition, it should have functions such as contact positioning, automatic weld start-up location, arc tracking, and automatic arc re-ignition.
Welding robots have a wide range of applications. Industrial robots and automated complete sets of equipment are key equipment in the production process and can be used in manufacturing, installation, testing, logistics and other production links. They are widely used in many industries such as automobile manufacturing and auto parts, construction machinery, rail transportation, low-voltage electrical appliances, power, IC equipment, military industry, tobacco, finance, pharmaceuticals, metallurgy and printing and publishing.
Three welding methods
1. Gas shielded arc welding:
Argon arc welding, which uses argon as the shielding gas for the welding area, and carbon dioxide shielded welding, which uses carbon dioxide as the shielding gas for the welding area, both belong to gas shielded arc welding.
The basic principle is that when welding with an electric arc as the heat source, a 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 electric arc and the liquid metal in the weld pool from contamination by oxygen, nitrogen, hydrogen and other substances in the atmosphere, thereby improving the welding quality.
2. Tungsten inert gas welding:
Arc welding, which uses a high-melting-point tungsten rod as one of the electrodes to generate the arc during welding and is protected by argon gas, is often used for welding stainless steel, high-temperature alloys and other materials with strict requirements.
3. Plasma arc welding:
Plasma arc welding is a welding method developed from tungsten inert gas (TIG) welding. It involves ionizing ionized gas to generate a high-temperature ionized gas stream, which is ejected from a nozzle orifice and compressed to form a slender arc column. This arc column is higher than that of conventional free arc welding, such as TIG welding which only reaches 5000-8000K. Due to its characteristics of a slender arc column and high energy density, plasma arc welding has wide applications in the welding field.
Three types of gas shielded welding
Arc welding robots mostly employ gas shielded welding methods (MAG, MIG, TIG). Common welding power supplies, such as thyristor-based, inverter-based, waveform-controlled, pulsed, or non-pulsed types, can be installed on the robot for arc welding. Since the robot control cabinet uses digital control, while the welding power supply is mostly analog control, an interface is needed between the welding power supply and the control cabinet.
In recent years, foreign robot manufacturers have developed their own specific welding equipment, which already includes corresponding interface boards. Therefore, the arc welding robot system shown in the image above does not have an additional interface box.
It should be noted that the arc time accounts for a large proportion of the working cycle of an arc welding robot. Therefore, when selecting a welding power source, the power supply capacity should generally be determined based on a 100% duty cycle.
1. MIG welding (Gas Metal Arc Welding):
This welding method uses an electric arc burning between a continuously fed welding wire and the workpiece as a heat source, and the arc is protected by gas ejected from the welding torch nozzle. The inert gas is usually argon.
2. TIG welding (Tungsten Inert Gas Welding):
TIG welding uses a direct current arc as its heat source, with a working voltage of 10–15 volts but a current of up to 300 amperes. 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 typically argon.
3. MAG welding (gas metal arc welding):
Gas metal arc welding (GMAW) uses an inert gas with a certain amount of active gas, such as O2 or CO2, as a shielding gas.
