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Introduction To Spot Welder
Apr 09, 2018

Spot welder is divided according to use, there is universal (universal), special type; According to the number of solder joints welding at the same time, there are single point, double point and multi-point. According to the mode of conduction, there are unilateral and bilateral; According to the transmission mode of the pressure mechanism, there are pedal type, motor - CAM type, air pressure, hydraulic type and compound type (gas hydraulic combination). According to the characteristics of operation, there are non-automation and automation; According to the method of installation, there are fixed, movable or portable (hanging type); According to the moving direction of the electrode of the welding machine (normal is the upper electrode), there is a vertical stroke (the electrode is in a straight line) and the arc stroke; According to the power supply mode, there are frequency welding machine (50 hz ac power supply), pulse welding machine (dc pulse welding machine, energy storage welding machine, etc.) and frequency conversion welding machine (such as low-frequency welding machine).

When the workpiece and the electrode must be the resistance of the workpiece depends on its resistivity. As a result, the resistivity is one of the important performance by welding materials. High resistivity of the metal its poor electrical conductivity, such as stainless steel low resistivity of the metal its conductivity is good (e.g., aluminum alloy). Therefore, generate heat easily when spot welding of stainless steel and heat dissipation, produce hot difficult during spot welding of aluminum alloy and heat dissipation is easy. When spot welding, the former small current (several thousand amperes) are available, and the latter will have to use a large current (tens of thousands of amp). Resistivity not only depends on the type of metal, but also relates to the heat treatment state, processing mode and temperature of the metal.

In order to ensure the weld size and weld strength, welding time and welding current can be complementary to each other in a certain range. In order to obtain a certain intensity of solder joints, large current and short time (strong condition, also known as hard specification) can be used, and small current and long time (weak condition, also known as soft specification) can be used. The selection of hard or soft specifications depends on the performance, thickness, and power of the welder used. There is an upper and lower limit for the current and time required for different properties and thickness of the metal.

Electrode pressure between the two electrodes has distinct effect on the total resistance R, with the increase of electrode pressure, R decrease, and the increase of welding current amplitude is small, can't influence caused by R reduce heat production decrease. Therefore, the solder strength decreases with the increase of welding pressure. The solution is to increase welding current while increasing welding pressure.