Wire feeders for constant-voltage FCAW systems are generally simple devices that provide a constant wire feed speed. The power supply provides sufficient current to maintain an arc at the voltage that is preset at the power supply. A change in wire feed speed results in a change in the welding current.
Both air-cooled and water-cooled welding guns are used in the semiautomatic FCAW process. Air-cooled guns are generally preferred, because they are simpler to maintain, lighter in weight, and less bulky. Water-cooled guns may be required when welding currents over 500 A are used, especially when the shielding gas is rich in argon.
A trigger switch on the welding gun is closed to initiate wire feeding, welding current flow, and shielding gas flow. The electrode is delivered from the wire feeder to the gun through a flexible conduit. Standard conduit lengths are 3, 3.7, 4.6, and 6 m (10, 12, 15, and 20 ft). Other lengths may also be available.
Mechanized and automatic FCAW equipment is not substantially different from that used in the semiautomatic FCAW process. The power supply should be rated for 100% duty cycle. Power supplies capable of outputs up to 1000 A may be required for some applications. Constant-current systems are very seldom used for mechanized and automatic welding.
- The wire feed system is separated into a drive motor assembly and a welding control device, the latter of which often has a system to automatically start the travel mechanism when wire feed, current flow, and shielding gas flow are initiated.
- The welding control device is often equipped with a voltmeter and ammeter, as well. The welding gun in mechanized and automatic systems is often mounted directly to the drive motor assembly, eliminating the need for a conduit.
- The gun is usually straight, but curved-neck guns are also used. Both water- and air-cooled guns are used, depending on the welding current level and shielding gas.
- Most of the commonly available air-cooled guns can be used at levels up to 500 A with CO2 shielding gas.
- When argon rich shielding gas is used, the same gun may only be suitable for use at levels up to 300 A. Water-cooled guns are generally used at higher current levels.
- Various travel mechanisms are used, depending on the applications. These mechanisms include side-beam carriages, tractor-type carriages, and robots.
- In many cases, the amount of fumes generated by the FCAW process is sufficient to require fume-removal equipment.
- Although such equipment can be as simple as exhaust fans in the shop roof, local fume collection is often necessary.
- These systems can be either collection hoods (located above the welding gun) or fume extractor guns. These guns are more efficient at collecting fumes, but are heavier and more bulky than standard welding guns.
- Fume collection hoods must be repositioned each time the welding location is moved in order to be effective.