Function

• The purpose of all welders is to join similar types of metal together by melting them at a high temperature and adding a filler into the molten puddle of metal for extra strength. The filler material used is a metal of the same type that is being welded. MIG welding uses a wire that is fed from a spool and through a center tip on the hand-held torch. A button on the torch advances the wire into the molten puddle as well as energizes the electrical current to melt the metal. An inert gas, generally argon, is also blown into the small welding area as a gas stream. This stream of gas keeps out any air impurities from the molten puddle of metal. The combination of electrical current, automatic wire feed and the inert gas stream makes for a fast and efficient method of welding.
  
  

Types

• MIG welders have the capability of welding not only carbon-based steels but aluminum as well. The wire must be changed from that of steel welding along with the type of gas used for the inert gas stream. Some inert gas manufacturers offer specialized blends of gas for the different types of metal to be joined together.
  
  

Identification

• MIG welders can be identified by the spool attachment that contains the wire used as the filler in the welding process. Some machines have the spool drive mechanism attached internally to the welding unit. Others have a torch attachment where it fits on the torch head itself. The torch-attached spool arrangement can be bulky in practice, since it may be difficult to reach certain areas for welding.
  A gas regulator is another identification of an inert gas welder. The gas regulator controls the flow and pressure of the gas, which is held in a high-pressure tank or bottle. The tanks may contain a pressure of 2,000 to 3,000 pounds per square inch (psi). The welding process requires a low pressure of 20 to 30 psi. The high-pressure tank allows for a large storage capacity to perform long runs of welding.
  
  

Size

• MIG welders range in size from large industrial machines that require three-phase electricity to the home "buzz box" that can be plugged into any wall outlet. The home or small shop units are about the size of a 12-pack cooler and are easily carried. The bulk of the unit is the large gas bottle that must be attached to the MIG welder. This gas connection is generally a lightweight rubber hose and can have a length of up to 50 feet. The regulator is always attached directly to the gas bottle so the hose and small MIG unit can be carried anywhere within the length limits of the gas hose and electrical plug-in to the wall.
  
  

Warning

• All welders emit a very bright, blue to white arc light. This light can create a hazardous situation to any exposed skin and unprotected eyes. Certain precautions must be taken when welding. Proper eye and face protection in the form of an approved welding hood should be used. The welding hood covers the entire face, and the dark lenses allow only the proper light to enter into the hood during the welding process. Protective clothing and gloves should also be worn, since MIG welding emits a shower of sparks during the arc burning. The area in which welding takes place should be clear of all burnable debris, and you should never weld around any flammable material such as gasoline.