Important parts and accessories of MAG welding machine
The welding equipment consists of mainly welding power source, cables, wire feed mechanism having pair of wire driving rolls and electric motor, welding gun and wire electrode coiled spool, inert shielding gas cylinder, and pressure regulator, flow meter controls to regulate the current, electrode wire and gas.
The welding gun consists of two current conductors for shielding gas and a wire guide tube which is passed through welding nozzle. Unlike TIG welding where non-consumable filler rod is used, MIG welding uses consumable filler material on the metal work piece. Also, welding torch is replaced by welding gun in this type of welding to feed direct current to the metal work piece. The welding gun which holds and feeds the electrode and gas may be air-cooled or water-cooled. The nozzle used can be either straight or inclined for convenience to weld complex shapes and intricate joints.
The power source used can be AC transformer or DC generator but DC generator is recommended because with AC transformer, the unequal burn off rates during negative and positive half cycles is evident. DCRP (DC with reverse polarity) provides deep penetration. The power source of 400 Amps with flat or drooping characteristics can be applied for MIG welding. Arc length is better with flat characteristics weld source. For thin metal work piece, electrode is made negative in DC and for welding aluminum and magnesium, DC electrode is positive.
To feed the wire consistently to the weld metal work piece, wire feeding mechanism is installed which delivers the electrode wire at constant speed or different desired speeds. Electrodes come in the sizes ranging from 0.8 mm, 1.2 mm, 1.6 mm etc and different quantity from 1 kg spool and so on. The steel electrodes are copper coated. While welding, one need to ensure that the electrode and metal work piece should match in chemical composition in addition to deoxidizers. The available electrodes in the market are for welding of aluminum, magnesium, nickel, stainless steel and their alloys and low carbon steel.
A number of shielding gases and the mixtures are used in MIG welding for different metals and applications like argon and helium for welding aluminum, magnesium, copper and nickel. Carbon dioxide gas finds application in welding mild steel, nitrogen for copper again etc. Argon, helium, carbon dioxide and oxygen independently or in mixtures are mainly used gases in MIG welding. CO2 and helium gas encourage penetration and argon controls spatter.
Controls and solenoid valves are integrated in the equipment for regulating gas, water and wire feed mechanism.