Buying advice for Welding Equipment
M.I.G. T.I.G. M.M.A. PLASMA
M.I.G.
There are various types of M.I.G. welders. They range from the home D.I.Y. type to heavy industrial machines up to about 500amps. There are transformer, thyristor and inverter machines. Transformer types have switched power settings, transformer/thyristor has variable settings, inverter machines have variable settings together with low no load power consumption (typically 100watt) and lightweight. They are made in single phase models which operate on 240 volt AC or three phase models on 415volt AC. Single phase models are available up to 300amps, three phase models are available up to 500amps or more. The machines are available as a compact machine or with a separate wire feeder. At the higher amperages water cooled versions are available. Water cooling has the advantage of a cooler welding torch in use, however this involves a more complicated torch and more to go wrong. Practically, if you can, an air cooled torch is more robust and cheaper to operate in an industrial environment. Depending on your intended use, you must purchase a machine with an adequate duty cycle. This means that the machine is capable of giving you the performance that you need without cutting out prematurely and costing you time waiting for it to cool down so that you can weld again. There are also specialised M.I.G. welders for welding stainless steel and aluminium. They are called synergic/pulse machines. Very simply put, the welding characteristic is controlled electronically. They are usually pre programmed for many types of materials, and have the option to program in your own settings as well. Another option for welding aluminium (and other materials) is to fit a spool-on-gun
T.I.G.
D.C. T.I.G. welding is used for most materials (other than aluminium), and A.C. T.I.G. for aluminium. Most modern A.C. T.I.G. welders will also switch to D.C., giving you the capability to weld most materials. Conventional transformer AC/DC machines are available in single phase(240volt) up to about 200amps, and three phase (415volt) to 500amps. There are small lightweight inverter T.I.G.'s available from 130amp to 500amps. The smallest D.C. machines can be used on 110volt input (as required by U.K. regulations in many industrial environments). Small AC/DC inverters are now available to 200amps with single phase(240volt) input. Larger machines are usually three phase input only. Most modern machines have High Frequency arc starting or they can be switched to Lift Arc starting if there is a risk of interference to computer/communication equipment.
M.M.A.
Originally most electric welding was done by Manual Metal Arc (or Stick Welding) using large A.C. transformer machines. It has mainly been superceded by M.I.G. due to the faster rate of welding. Nowadays M.M.A. is mainly used for repair and maintenance of plant and machinery, particularly outdoors, and for outside fabrication. Engine driven mobile welders are usually used for M.M.A. when there is no mains power available. It is often much quicker and easier to 'Stick Weld' a small job than it is to set up a M.I.G. especially if the job is in an awkward or windy location. Most modern sets are D.C. Inverter machines ranging from about 130 to 500amps. They have a very smooth welding arc together with the benefit of lightweight. Our latest 150 amp inverter weighs just 4.4kg.
PLASMA
Plasma can be used to cut most conductive materials. It is most commonly used for cutting stainless steel and aluminium. When used correctly it can give a very fine cut, almost distortion free, due to the small heat input into the parent material. In our experience you need to purchase a machine that will cut double the maximum capacity of the material that you are cutting, and possibly three times the capacity for aluminium. This will enable you to cut at much faster speeds and will keep the heat input into the material to a minimum. When cutting copper (the best conductor) we had to use a 50mm capacity machine to cut a 13mm copper tank. There are generally two types of machines produced, conventional transformer and inverter. The transformer range normally has switched power settings, and are much heavier in weight than the inverter machines. The inverters normally have variable power control enabling you to adjust the power to the material you are cutting. Most people use home produced compressed air as the plasma and cooling gas. It is absolutely essential that the air is free from oil and moisture to ensure that you get the best usage from the torch consumables.