

Resistance Weld
■ Principle and advantages of resistance welding
Resistance welding is a kind of welding method by overlapping metal workpieces and applying appropriate pressure to make them heat up at the welding point through large current, and finally welding metal workpieces together. Since the voltage is only a few volts when welding, the welding process is relatively safe. In addition, there is almost no smoke during welding, which can keep the maintenance environment clean and tidy.
Resistance welding is widely used in automatic production systems because of its stable welding quality, simple operation and high cost performance ratio of input and output.
■ Configuration of a Resistance Welder and the Role of Each Part
Resistance welder sandwiches an object to be welded by the welding electrodes, and applies electric current while applying a pressure.
■ Welding Power Supply:
It controls the magnitude, time and waveform of electric current.
■ Welding Transformer:
It converts the electric current from the power supply to a larger current.
■ Welding Head:
It controls the pressure to be applied.
■ Welding Electrode:
It contacts the object to be welded to apply pressure and electric current.
■ Secondary Cable:
Connection transformer with weld head.
■ Features of Welding Source
● AC Inverter power supply
The advantages of inverter welding power sources are good thermal efficiency and stable welding quality. Because the characteristic polarity effect of AC is very small, it can obtain equal welding effect and is the most suitable welding power source for hot pressure welding.
In addition, since the transformer of AC welding power source can be used, the upgrade is convenient.
※ Polarity effect
The current between different kinds of metals will generate Joule heat and heat absorption and exothermic phenomena, so the temperature difference between positive and negative electrodes will occur. Polarity effect will cause single side click wear and uneven solder joints.
Solution: Because this problem is caused by unidirectional DC, it can be solved by using AC or polarity switching.
● Energy storage welding power source
The energy storage welding power source obtains large current by charging and discharging capacitors, which is suitable for materials with superior thermal conductivity, such as aluminum, nickel, copper, etc. After the capacitor is charged, it can conduct stable welding even if the input electric quantity decreases. However, because the current rises rapidly and the tilt angle cannot be controlled, splashing is easy to occur.
● DC inverter welding power supply
As there is no current stop time of AC power supply, it can provide heat continuously, with advantages of high thermal efficiency, short welding time, small thermal impact, and power loss suppression. Through the control of inverter high-speed circuit, spatter can be prevented and welding quality can be stabilized, which is suitable for ultra precision welding. In addition, due to the small volume of the transformer, it is easier to set up an automatic production line.
● Transistor welding power supply
The welding power source, which controls the current through transistors, can inhibit spatter and is suitable for ultra precision welding. Because the current control speed is very fast, it can be used in the welding of extremely thin wires (filament, etc.), which is most suitable for the ground resistance material.
● AC welding power supply
AC welding power source is the simplest welding power source by controlling the AC conduction angle. The thermal efficiency is relatively poor, and the workpiece is prone to thermal impact, so it is not suitable for ultra precision welding. The most commonly used materials are iron based materials that are relatively easy to weld.
■ Comparison of various welding power sources
■ Type of welding electrification mode
■ Welding method of enameled wire
■ Resistance Welding Properties of Materials