Special types of spot welding
To improve performance, multi-point welding is used in which one cycle of the machine is welded by a few points. The electrodes are pressed against the product, which lies on the conductive copper lining. Current flows through the circuit electrode - a product - a copper lining - the product - the second electrode. Welded together two points. This method is called two-point one-sided welding. Multipoint machines typically have a hydraulic drive and operate on the principle of two-point one-sided welding.
Oil distributor distributes oil under high pressure in the cylinders and presses the individual electrodes to the product of two respective electrodes by applying a current to them, then the current is switched off, the electrodes are retracted, the oil is fed into the next couple of cylinders and so on, until the finished welding of the entire site. These machines can have up to 100 or more electrodes.
In some multi-point machines all at once the electrodes are pressed against the product, which provides a lower warpage, and greater accuracy of the product. The current spread between the electrodes pressed a special commutator having a very sophisticated device and comprising electrodes in pairs, carrying out the process of two-point one-sided welding. Both types of machines are only applicable in mass production, and for each part requires a rather complex manufacturing of devices with the appropriate placement of the electrodes and the hydraulic cylinders.
A few simple simultaneous welding of several points raised by means of welding or welding projections, which is a kind of spot welding. In this case, one of the workpiece or both pre vyshtampovyvayut protrusions (reliefs)
in places subject to welding. Trained lay down the details in a special welding machine that bears the name of "welding press." Welding of lugs may also be at the point of powerful machines with a straight course of the electrode and the electrode is replaced by a normal point-specific electrode for projection welding, plate-shaped solid. Simultaneously with the inclusion of current top electrode compresses the parts and compressed them to complete destruction of the projections. Thus, over the course of a machine is so spot welds, as it was stamped projections, their number can reach up to several dozen in one piece. To obtain high-quality welding requires accurate punching and a snug fit on all parts collected projections.
The method of projection welding can provide high performance. The electrodes are in good working conditions and have a great life because of their contact surface is very high and the pressure and current projections are concentrated in the welded parts.
The disadvantage of projection welding is a significant electrical power required for welding presses. The magnitude of this power for the welding of a 15-30 bulge that. Pressure on a ledge is typically 200-600 kg. A variety of projection welding is a welding rod to the ends of the sheets. This socket or T-shaped welding can be performed on normal pin machines in more simple devices. End of the rod is often attached to a spherical shape, and the end of the rod cross-section increases the pre-landing.
Usually on the spot weld machines is relatively small parts that can lay motionless in a fixed spot the car.
See also:
Electric Resistance Welding
Pliers for Welding
Spot Welding
The Spot Welding Process
The Spot Welding Process (Part 2)
Special Types of Spot Welding
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