MIG WELDER
What this tool is used for:
The MIG welder is used for joining metal together.
General information:
MIG welding was developed in the 1940's and 60 years later the general principle is still very much the same. MIG welding uses an arc of electricity to create a short circuit between a continuously fed anode (+ the wire-fed welding torch) and a cathode ( - the metal being welded).The heat produced by the short circuit, along with a non-reactive (hence inert) gas melts the metal and allows them to mix together. Once the heat is removed, the metal begins to cool and solidify, and forms a new piece of fused metal. A few years ago the full name - Metal Inert Gas (MIG) welding was changed to Gas Metal Arc Welding (GMAW) but if you call it that most people won't know what you are talking about - the name MIG welding has stuck.
MIG welding is useful because you can use it to weld many different types of metals: carbon steel, stainless steel, aluminum, magnesium, copper, nickel, silicon bronze and other alloys.
Advantages of MIG welding:
The ability to join a wide range of metals and thicknesses
All-position welding capability
A good weld bead
A minimum of weld splatter
Easy to learn
Disadvantages of MIG welding:
MIG welding is best used on thin to medium thick metals
The use of an inert gas makes this type of welding less portable than arc welding which requires no external source of shielding gas
HOW DOES THE MIG WELDER WORK?
A MIG Welder has a couple of different parts. Inside the welder you will find a spool of wire and a series of rollers that pushes the wire out to the welding torch. There isn't much going on inside this part of the welder, so it's worth it to take just a minute and familiarize yourself with the different parts. If the wire feed jams up for any reason you will want to check this part of the machine out. A welder with internal feed assy is commonly known as a compact mig welder. The large spool of wire should be held on with a tension nut. The nut should be tight enough to keep the spool from unraveling so to avoids over-run (birds nesting) when trigger released, but not so tight that the rollers can't pull the wire from the spool. If you follow the wire from the spool you can see that it goes into a set of rollers that pull the wire off of the big roll, this then pushes the wire up to the torch to the tip ready for welding.
The Gas Supply.
Assuming you are using a shielding gas with your MIG welder there will be a cylinder of gas behind the MIG. This is either100% Argon or a mixture of CO2 and Argon. This gas shields the weld as it forms. Without the gas your welds will look brown, splattered and just generally not very nice. When welding in areas with a draught you may need to run more gas pressure to avoid getting porosity in the weld.
Once the wire passes through the rollers it is sent down a set of hoses which lead to the welding torch. The hoses carry the charged electrode and the argon gas.
The Welding Torch.
The welding torch is the business end of things. It's where most of your attention will be directed during the welding process.The torch consists of a trigger that controls the wire feed and the flow of electricity. The wire is guided by a replaceable copper tip that is made for each specific welder. Tips vary in size to fit whatever diameter wire you happen to be welding with.The outside of the tip of torch is covered by a metal shroudwhich protects the electrode and directs the flow of gas out the tip of the torch.
The Earth Clamp.
The earth clamp is the cathode (-) in the circuit and completes the circuit between the welder, the welding torch and the project. It should either be clipped directly to the piece of metal being welding or onto a metal welding table.The earth clamp must be making good contact with the piece being welded for it to work so be sure to grind off any rust or paint that may be preventing it from making a connection with your work.
SAFTEY PRECAUTIONS
MIG welding is a pretty safe thing to do so long as you follow a few important safety precautions. Because MIG welding produces lots of heat and lots of harmful light, you need to take a few steps to protect yourself.
The light that is generated by any form of arc welding is extremely bright. It will burn your eyes and your skin just like the sun will if you don't protect yourself. The first thing you will need to weld is a welding mask. Auto darkening masks are really helpful if you are going to do a lot of welding and make a great investment if you think you will be working with metal often. Manual masks require you to jerk your head,dropping the mask into position or require you to use a free hand to pull the mask down. Think of protecting others from the light as well and use a welding screen if it's available to make a border around yourself. The light has a tendency to draw on lookers who might need to shielded from being burned too.
Wear gloves and leathers to protect yourself from molten metal splattering off of your work piece. Some people like thin gloves for welding so you can have a lot of control. In TIG welding this is especially true, however for MIG welding you can wear whatever gloves you feel comfortable with. The leathers will not only protect your skin from the heat produced by welding but they will also protect your skin from the UV light produced by welding. If you are going to be doing any amount of welding more than just a minute or two you will want to cover up because UV burns happen fast!. If you are not going to wear leathers at least make sure that you are wearing clothing made from cotton. Plastic fibers like polyester and rayon will melt when they come into contact with molten metal and will burn you. Cotton will get a hole in it, but at least it won't burn and make hot metal goop.
Do not wear open toed shoes or synthetic shoes that have mesh over the top of your toes. Hot metal often falls straight down and I have burned many holes through the tops of my shoes. Molten metal + hot plastic goo from shoes = no fun. Wear leather shoes or boots if you have them or cover your shoes in something non-flammable to stop this.
Weld in a well ventilated area. Welding produces hazardous fumes which you shouldn't breathe in if you can avoid it. Wear either a mask, or a respirator if you are going to be welding for a prolonged amount of time. Important Safety Warning DO NOT WELD GALVANIZED STEEL. Galvanized steel contains a zinc coating that produces carcinogenic and poisonous gas when it is burned. Exposure to the stuff can result in heavy metal poisoning (welding shivers) - flu like symptoms that can persist for a few days, but that can also cause permanent damage.
Fire Fire Fire: Molten metal can spit several feet from a weld. Grinding sparks are even worse. Any sawdust, paper or plastic bags in the area can smolder and catch fire, so keep a tidy area for welding. Your attention will be focused on welding and it can be hard to see what's going on around you if something catches fire. Reduce the chance of that happening by clearing away all flammable objects from your weld area. Keep a fire extinguisher beside the exit door from your workshop. CO2 is the best type for welding.
