Mig welding maintenance and specifications

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Shop Area: Metal Shop

Tool: MIG Welder

Requires in-person training: Yes 

Procedure Number

MT 130-03, Rev. 1




The Millermatic 211 is both a stick welder and a MIG welder, see sister Stick Welding Guide UG 130-02 and Maintenance Guide MT 130-02

Millermatic 211 Stick and MIG Welder.png



Maintaining MIG (GMAW) Welders
Unlike stick welders, wire welders (MIG and/or flux-cored welding) include many more peripheral items – including the gun liner, gun contact tips and the shielding gas hose – and therefore require much more regular care and attention. Again, always unplug the machine before performing any maintenance tasks.

Steel drive rolls typically do not experience a great deal of wear. However, when the wire runs across them, it can introduce a great deal of dirt and dust that can build up on the drive rolls. To combat the buildup of grime, it’s a good idea to blow out the inside of the feeder section of the machine with compressed air at least once a week to keep the drive rolls clean and in the best shape for feeding thin .025 - .035 inch welding wire. Alternately, you can remove the rolls and clean them with a wire brush. Most important – no matter which method you opt to use – always make sure the wire feeder is powered off before inspecting or cleaning the drive rolls.

Because the wire runs through the drive rolls and into the gun liner, it can create dirt and dust buildup in the liner. Again, it’s good practice to blow out the liner with compressed air from the contact tip end of the gun approximately once a week to remove accumulated dust and dirt, especially if you’re not using your welder on a regular basis.

Next, always ensure that the liner is cut to the proper length – if it’s too short, dirt and dust can build up between the liner and the retaining head, causing problems with your wire feeder. And, to make sure your gun liner is always protected and maintained, never drive or roll anything heavy over the gun cable – it will flatten the liner, and you’ll typically have to replace it.

Often overlooked areas in welder maintenance, the gun contact tips, cone and diffuser are essential to maintain for trouble-free welding performance. Because these components work together to facilitate the necessary electrical conductivity and gas dispersion for the MIG process to occur, you won’t be able to weld properly if these elements of your system aren’t kept in top shape.

While welding, the gun nozzle, which helps to shield the weld, often becomes filled with spatter. Make sure to keep the nozzle clean in order to avoid inhibiting the flow of gas and preventing your ability to weld. Using nozzle dip will help keep the nozzle clean. Similar to the consistency of jelly, a product referred to as nozzle dip can help prevent spatter from sticking to the nozzle. Simply dip the nozzle in the product every once in a while welding to reduce the buildup of spatter. However, don’t fully submerge the entire nozzle, as doing so can damage the porous insulator in the nozzle’s interior – just dip the tip. Also, store the nozzle in the manufacturers packaging to prevent damage – if you toss it in a bin or other container, it may get dented or scratched, creating defect areas that can collect spatter.

The diffuser screws into the gun tube inside of the nozzle and disperses the shielding gas required for MIG or gas-shielded flux-cored welding. Like on the nozzle, the buildup of spatter on the diffuser also will inhibit the flow of gas. On a regular basis, remove the cone and check the diffuser to ensure that it’s not clogged. If there is spatter in the diffuser, use a wire brush or rag to wipe it clean.

To ensure that your gun contact tips stay in the best shape, try not to touch the tip to the work piece. Every time you make unwanted electrical connection between the tip and the work piece, the tip is damaged. Often, it is possible to burn the tip enough to modify the path of the wire through the tip and affect weld quality. Also, for best performance, be sure to change the tip to a model with the correct hole size every time you change the wire diameter size.

Still, despite a welder’s best efforts, gun contact tips do eventually need to be replaced. After significant use, the hole diameter in the tip will elongate, affecting wire placement in the joint.

Also, tips will wear out and become covered in spatter. This signals that it’s time to purchase a new one.

Other concerns when MIG welding include paying attention to the shielding gas bottle – make sure it is always chained up, either to the machine or somewhere in the shop. If it falls over with a regulator on it, the gas will try to escape and the gas stream could potentially hurt someone. To prevent the escape of gas when not in use, remove the regulator and fasten a threaded protector cap to the top of the bottle to keep the valve system safe and help prevent a rupture.

To keep your shielding gas hose in good shape, coil it loosely and store it off the ground to prevent it from twisting or kinking, which may cause damage. Also make sure to examine it regularly for any holes or potential leakage spots. Store it somewhere cool and dry.

Perhaps the simplest tip for maintaining your MIG welder is to prevent dust by keeping a cover on top of the machine when not in use.  And, it’s good practice to have a certified technician service/inspect your guns periodically.

Though MIG welding has many more machine maintenance requirements than stick welding, one maintenance benefit of the GMAW process is that the wire is generally copper coated, which means it’s less likely to rust, eliminating the need for a rod oven.

While caring for MIG equipment has many elements, there’s an easy way to spot a potential maintenance problem – visible porosity holes in your weld. With any gas-shielded process, visible porosity in the weld indicates a procedural problem or a shielding gas problem – it signifies that you’re out of gas, the nozzle is clogged or there’s a hole in your shielding gas line. So, pay attention to your weld quality – it’s an easy barometer of whether or not your machine maintenance is up to date.


Stick Welding Specs.png

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