Spot welding, as know as resistant spot welding, is a technique of resistant welding. This technique is mainly used in welding pieces of sheet material or different materials together by applying heat produced by current and pressure.
The working purpose spot welding bases is passing the current through the copper alloy electrode and the two metal materials. When the current pass through the materials, it would produce heats to melt the materials and join the materials which are ready to weld together.
Moreover, this welding technique is the oldest welding processes. In other words, the spot welding had been developed well. Now, this useful welding technique has been applied in various industries.
Spot welding is one of the most economical welding techniques since this welding technique allows the materials welded together without the help of other metals. Thus, the cost would be deducted.
Spot welder, as known as spot welding machine, is the machine that used to perform the technique of spot welding.
Mostly, the spot welding machine looks like a big clamp. The tip of the big clamp is mainly made of copper since copper contains good conductive. In general, spot welding machines can be designed portable.
On the spot welding machine, electrode and the clamps, or we can call them tool holders.
When the spot welding machine works, the materials that are ready to weld would be put between the clamps. Then, the current would be released from the two copper clamps and in some level milt the welding spot of these two materials. After that, the two materials would be joined together stably.
Then, after the welding is down, the workpiece, that means the metal sheets joined together, would be cooled by the coolant holes in the center of the electrodes. Both water and a brine solution may be used as coolants in spot welding mechanisms.
Portable spot welders can be various according to various categories or different functions.
Below are common spot welding machines:
● Pedestal Type Welding Machine
This type of welding machine contains a fixed vertical pedestal frame, integral transformer, and control cabinet. This is not a portable one.
During the welding progress, the bottom arm is fixed to the frame for stability purpose because the weight of workpieces would lay on it. The top arm would be hinged so that it can move down in arch or straight.
The strength of the welding machine would not be the same all the time. It depends on the size of the electrode diameter or contract face, thickness of the workpiece, electrode pressure, welding current and current flow time. For example, the strength of the spot would be weak due to the low current and short welding time.
Therefore, in general, the welding time would be suggested to limit between 0.25-1.5 seconds. It the thickness of the sheet metal is over 5 mm, the duration would be longer.
When the machine is working, the temperature capacity could reach 500 degree Celsius.
● Resistance Butt Welding Machine
The resistance butt welding machine is also called upset welding machine. Equipment on the welder could be various, such as bedframe, table-top and guides, a platen that can be moved, one or multiple clamps, a feeding and upset mechanism, a transformer, a tap-change switch, and other switches etc.
When working with this kind of welding machine, the machine will stable the pressure the two electrodes make. Then the current would pass through the two electrodes and the elements ready to weld and join the materials together.
Resistance butt welding is mainly used to weld the round rods and bars up to 25 mm diameter
● Flash-Butt Welding Machine
Flash-butt welding is a welding technique that joining materials together by heat and rapid pressure.
When applying the technique, the points that are ready to weld would be heat by high current at low voltage. The surface of the welding materials would be connected a little bit.
When the current flow through the two materials, the current would cause the exposure and milt the material. When the material is milted, the technician would quickly press them together and cut down the current. Thus, the welding process is down.
● Seam Welding Machine
This is also a portable spot welding machine. On this machine, there are rollers controlled by the system.
When operating this portable spot welding machine, the materials ready to be joined would be clamped between two copper roller or wheel electrode drive systems. Then, the current would pass through one or two copper rollers and weld the materials together.
The portable seam welding machine could be found in factories manufacture tanks, exhaust systems, barrels, drip-moldings on car body parts etc.
● Projection Welding Machine
Basically, projection welding machine works by pressure. The two materials ready to weld would be designed one flat and one with protrusion. When the switch is on and the current pass through the protrusion, pressure would be added onto the protrusion and weld the two materials together.
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