Spot welding machine according to the use of points, there is a universal type (universal type), dedicated type; according to the number of solder joints at the same time, there are single-point, double-point, multi-point; according to the conductive way points, there is a single side, Bilateral; According to the transmission mechanism of the pressurizing mechanism, there are foot type, motor-cam type, pneumatic type, hydraulic type, compound type (pneumatic combination type); according to the characteristics of operation, there is non-automation and automation; The installation method is divided into fixed, movable or portable type (suspended type); in accordance with the direction of movement of the movable electrode (usually the upper electrode) of the welding machine, there is a vertical stroke (electrode for linear motion), circular arc travel; According to the power supply method, there are power frequency welding machines (using 50 Hz AC power supply), pulse welding machines (DC pulse welding machines, energy storage welding machines, etc.), and frequency conversion welding machines (such as low-frequency welding machines).
When the workpiece and electrode are certain, the resistance of the workpiece depends on its resistivity. Therefore, the resistivity is an important property of the material being welded. The metal with high resistivity has poor conductivity (such as stainless steel). The metal with low resistivity has good conductivity. (such as aluminum alloy). Therefore, spot welding of stainless steel is easy to produce heat and difficult to dissipate heat. It is difficult to produce heat when spot welding aluminum alloy and easy to dissipate heat. When spot welding, the former can use less current (several thousand amps), while the latter must use a very large current (a few Million. The resistivity depends not only on the type of metal, but also on the state of heat treatment, processing method, and temperature of the metal.
In order to ensure the size of the nugget and the strength of the solder joint, the welding time and the welding current can complement each other within a certain range. In order to obtain a certain strength of the solder joints, it is possible to use large currents and short-times (strong conditions, also called hard gauges), and also small currents and long periods (weak conditions, also called soft gauges). The choice of hard or soft specifications depends on the properties of the metal, the thickness, and the power of the welder used. There is an upper limit and a lower limit for the current and time required for metals of different properties and thicknesses, whichever is applicable.
The electrode pressure has a significant effect on the total resistance R between the two electrodes. With the increase of the electrode pressure, R significantly decreases, but the magnitude of the welding current increase is not large, and the heat generation caused by the decrease of R cannot be reduced. Therefore, the total strength of the solder joints decreases as the welding pressure increases. The solution is to increase the welding current while increasing the welding pressure.