MIG welding aluminium is hard, but Mig welding aluminium with a spool gun can make it a lot less difficult!
The fact that Mig, or to give it its proper name, Gas metal arc welding (GMAW) aluminium is hard is probably not news to most of you who read this blog. The soft nature of using an aluminium filler wire results in kinks and bind problems within the MIG gun lead. These kinks and binds make the wire fold up inside the gun, often resulting into something called a “bird’s nest”; these are hard to clear. One is therefore forced to calculate, in the costings of the end product, the wastage of wire and down time of production when using a MIG gun lead. The solution to overcome this situation in MIG welding of aluminium is to bypass the MIG lead completely by replacing it with a Spool gun. In these notes we describe a Spool gun, in case any among you are complete beginners learning the discipline required for the welding of metals by this method, and the basic practices of how to use it.
Metal inert gas (MIG) welding is a sub type of gas metal arc welding. MIG welding is an automatic welding process, which uses a consumable electrode to produce the weld. The MIG welding process is a more advanced process than the TIG welding aluminium process and is more suitable for thicker pieces of aluminium construction. MIG welding is a faster method of production enabling the operator to achieve nonstop welds. MIG welding also results in less deformation of the metal being worked.
As stated above, MIG welding without a spool gun is not an easy process. The wire that you feed through the MIG gun gets folds and kinks, which can be avoided by a special type of weld gun called a Spool gun. A Spool gun is made much like a “Tommy Gun: that is often depicted in gangster scenes of the 1930’s. It contains a large spool of aluminium filler wire, which rests on the MIG weld gun. There is trigger on the handle that controls the the motor that feeds the aluminum wire through at a consistent speed allowing the elimination of those kinks and folds.
Spool guns use welding tips, giving the welder maximum control over his work. For a top results the gun must be pushed and not pulled. Pulling can result in a sooty weld, although, sometimes you just have to pull, in which case, one must try to reduce the sootiness this action causes, as much as one can. Use a stainless steel brush to remove the soot. Use Argon gas, or a mixture of Argon with Helium – The shielding gas of choice for the spool gun is usually 100% Argon, or a 50/50 mixture of Argon and Helium gas.
The Argon and Helium mixture is often used with thicker sections of metal. Always keep in mind what the manufacturer of the gun has advised as to use as the shielding gas. Many Gun manufacturers insist that on the use of 100% Argon use a longer stick-out. MIG welding uses spray transfer, so a longer stick-out will prevent the burning up of tips. ¾ of an inch is a good stick-out and will give less tip wear. Start with a fast wire speed – It is always a good idea to start with faster wire speed and go from there to a slower wire speed.
NOTE: If the power is too low, then the wire will hit the metal and break the arc, whereas if the power is too high, the wire will push through the molten puddle and you’ll get drips. The sound when welding steel is that of frying bacon . Not so with aluminium. With aluminium you get a high pitched “humm” sound.
Mig welding aluminium with a spool gun, as you can see has many advantages and is a technique that you should seriously consider if struggling to get robust welds on aluminium .