1. Classification of spot welding machines
Spot welding machines can be divided into universal types (universal, Special type) spot welding machine.
According to the number of solder joints welded at the same time, it is divided into: single-point type, double-point type and multi-point type.
Divided into: unilateral, bilateral.
According to the transmission mode of the pressurizing mechanism, it is divided into: pedal type, motor-cam type, pneumatic type, hydraulic type, compound type (pneumatic-hydraulic combined type).
According to the characteristics of operation, it is divided into: non-automation and automation.
According to the installation method, it is divided into: fixed, mobile or portable (hanging) spot welding machine.
According to the moving direction of the movable electrode (usually the upper electrode) of the welding machine, it is divided into: vertical stroke (the electrode moves in a straight line) and arc stroke.
Second, the working principle of spot welding machine
The process of spot welding is to open the cooling water; Enter between the upper and lower electrodes, apply pressure to make it in good contact; energize the contact surface of the two workpieces to heat, partially melt, and form a nugget; keep the pressure after power off, so that the nugget cools and solidifies under pressure to form a solder joint; remove pressure to remove the workpiece. Spot welding process parameters such as welding current, electrode pressure, energization time and electrode working surface size have a significant impact on welding quality.
The spot welding machine uses the high-temperature arc generated when the positive and negative poles are short-circuited instantaneously to melt the material to be welded between the electrodes to achieve the purpose of combining them. The structure of the spot welding machine is very simple. To put it bluntly, it is a high-power transformer that converts 220V AC into a low-voltage, high-current power supply, which can be either DC or AC. The welding transformer has its own characteristics, that is, it has the characteristics of a sharp drop in voltage.
After the electrode is ignited, the voltage drops, and the adjustment of the working voltage of the welding machine, in addition to the first 220/380 voltage conversion, the secondary coil also has a tap change voltage, and it is also adjusted by the iron core, which can be adjusted. Tune the iron core. The spot welding machine is generally a high-power transformer, which is made of the principle of inductance. The inductance will produce a huge voltage change when it is turned on and off, and the high-voltage arc generated when the positive and negative poles are short-circuited instantaneously is used to melt the solder on the electrode. for the purpose of combining them.
Third, the use of spot welding machine
1. When welding, the position of the electrode rod should be adjusted first, so that when the electrode is just pressed to the weldment, the electrode The arms remain parallel to each other.
2. The selection of the current adjustment switch series can be selected according to the thickness and material of the weldment. After the power is turned on, the power indicator light should be on, and the electrode pressure can be obtained by adjusting the spring pressure nut and changing its compression degree.
3. After completing the above adjustment, you can turn on the cooling water first and then turn on the power to prepare for welding. The procedure of the welding process: the weldment is placed between the two electrodes, the foot pedal is pressed, and the upper electrode is brought into contact with the weldment and pressurized. When the foot pedal is continued to be pressed, the power contact switch is turned on, so the transformer starts to work secondary. The loop is energized to heat the weldment. When the foot pedal is released after welding for a certain period of time, the electrode rises, and the power is first cut off by the tension of the spring and then restored to the original state, and the single-point welding process ends.
4. Preparation and assembly of weldments: All dirt, oil, scale and rust must be removed before welding of steel weldments. For hot-rolled steel, it is best to pickle and blast the welds Or use a grinding wheel to remove scale. Although the uncleaned weldment can be spot welded, it will seriously reduce the service life of the electrode, and at the same time reduce the production efficiency and quality of spot welding. Direct welding can be applied to medium and low carbon steels with a thin coating.
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