MIG Welder Metal Inert Gas Welding, Fusion welding process limited to application on structures of limited quality. Exploit the high temperature caused by an electric arc between an electrode body fuse (wire, DC power supply and reverse polarity) and the work piece. The wire electrode is the filler material. Typically, the progress of the wire occurs through a mechanism of thrust, this method is impractical for aluminum and its alloys because the risks of a failure of the wire are high. There is a device located in the torch, which pulls the wire (which can be pushed together). The speed of the wire varies between 10-20 m / min and controlled by the current variation of the arc, the power is independent.

The MIG is easier, more convenient, faster than TIG is used when the productivity and operational simplicity are important. It is characterized by high current density (100-250 A / mm ²) that enables high-speed storage. The equipment complex, expensive, difficult to transport, bulky, not suitable for solder joints in awkward positions, are major disadvantages. The welding system includes an electrical circuit, a circuit for gas protection, a circuit of cooling water (most modern guns are autoraffreddanti, the gas itself provides protection to prevent overheating), the torch containing the wire and the feed device for the wire.

During the welding wire electrode, the bath, the arch, the surrounding material, are protected from atmospheric contamination by inert gas flowing from the gun. It is important to define the modalities of transfer of the filler material which is determined by the electrical parameters of welding, the filler wire and gas type:

Transportation spray (spray-arc):

Every drop is spread freely and detaches from wire drawing to a bath of melting effect of electrodynamic forces (voltage 25-35 V, current density 120-200 A / mm ²), covering the distance corresponding to the length of the arc. It is characterized by a quiet arc, deep penetration, no spray, good aesthetics. To obtain a satisfactory umbilical having characteristics requires a deposit rate of more than 100 drops per second used for pieces with a thickness greater than 4-5 mm placed on the flat since the smelting bath is large.

Transfer pulsed arc (pulsed-arc):

It presents a basic current (direct current in reverse polarity), which aims to keep on learning and maintaining the molten bath and the wire without involving transfer between metal electrode and bathroom at regular intervals overlaps the basic current a current at greater intensity to restore the conditions of spray-arc, with the transfer of the drop to the smelting bath. It should be noted that the intensity of current pulse is higher than that of conventional spray transfer, are also provided for lower powers. This technique is very versatile, suitable both for thin layers with joints in various positions, both for high thicknesses (if greater than 15 mm is recommended pre-heating). The shielding gas is argon provided in quantities between 15-20 l / min, 0.8-1.2 mm diameter wire on small thickness, 20-25 l / min, wire diameter 1,6-2,4 mm at greater thickness. For this procedure are defined synergic welding where the operator acts on a control knob connected to the generator containing the memory (chip) introduced by the manufacturer or user, in which there are the optimal parameters of the pulses of current to be the best mode transfer of filler material, gas protection, in relation to the diameter of the wire and the position of welding. The procedure described is most suitable for remote control and so robotic.