Even though many consider MIG gun consumables to be a commodity — a simple ‘throw-away’ item — these components play a critical role in achieving good welding performance and quality. They can also affect the overall productivity and cost of your welding operation, often in some rather subtle ways. For both reasons, it’s crucial to find the best possible, longest lasting consumables for your application and maintain them with as much care as you would any other welding equipment.
MIG gun consumables, which comprise the front-end part of the gun — the nozzle, retaining head and contact tip — plus the liner, are at the heart of the welding process. These components are responsible for feeding the welding wire and for establishing the electrical conductivity necessary to produce the arc. And while the welding power source you use undoubtedly influences your operation’s performance, so too can your consumables. In fact, MIG gun consumables are one of the most overlooked portions of the welding operation. Without proper installation, storage and maintenance, these components can cause significant downtime for changeover and added cost for inventory, waste and rework.
Fortunately, through a few simple measures, you can extend the life of these components and positively affect the efficiency and profit of your welding operation. Here’s how.
Start at the beginning
Figure 1. Select a nozzle with a smooth surface to prevent spatter accumulation that can lead to downtime and shorten the life of the component. Note, this cut-away shows the inside nozzle insulator.
In the MIG welding process, the nozzle directs the shielding gas around the welding wire and arc to the weld puddle (Figure 1). Its purpose is to protect the weld from the atmosphere and other contaminants that can cause weld defects, such as porosity, that can lead to costly rework. Unfortunately, because of its proximity to the weld puddle, the nozzle is a common source of spatter accumulation that can obstruct the proper flow of shielding gas.
To prevent such problems, first consider the nozzle itself. Look for a smooth, non-porous surface free of sharp edges or flat spots, as it better resists spatter accumulation and, therefore, lasts longer. Also, choose nozzles that have some heft to them — they should look and feel sturdy. Heavier nozzles might cost more up front, but their longevity can help prevent downtime that will likely cost you more money over time.
Proper nozzle storage and handling is critical to extending the life of this component. First, keep the nozzle in its original packaging until you’re ready to use it. Unwrapping the nozzle to store it in a bin, while a common practice, dents and scratches the nozzle surface, making it more prone to spatter accumulation. Nozzles unprotected from the environment also can accumulate air-borne contaminants or debris, which, if introduced into the weld puddle, might cause defects that need to be reworked.
Generally, semi-automatic MIG gun applications use slip-on nozzles. When installing one, make certain to connect the nozzle to the retaining head securely to prevent shielding gas leaks that can lead to weld defects. Also, be mindful whether you have any debris, grease or oil on your hands or gloves. Keep the nozzle as clean as possible to prevent contamination from entering the weld puddle later or causing premature component failure.
Consider using an anti-spatter compound (gels are commonly used in semi-automatic applications) to reduce the amount of spatter that adheres to the nozzle. Apply the compound by dipping only the front 1.5 in. of the nozzle into the compound. Don’t submerge the nozzle, as this can saturate the internal porous insulator, causing it to fail prematurely, accumulate spatter more readily and produce an erratic arc — all factors that lead to downtime, extra costs and waste associated with changing over to a new nozzle.
Next, periodically inspect the inside and outside of the nozzle visually for spatter, ideally several times throughout the welding shift. If it appears clogged, clean the nozzle using a tool specifically designed for the job or replace it if necessary.
Finally, never use the nozzle to chip away at spatter or for any other hammering purpose. Doing so damages not only the MIG gun, but it can dent or misshapen the nozzle, rendering it unusable.
Good welding performance depends on good electrical conductivity. Look for a contact tip system — the contact tip and retaining head — that stays tight or has locking features (Figure 2). The retaining head (also called a diffuser) is the component that forms the connection between the nozzle and the MIG gun neck, and holds the contact tip in place. This component also provides the surface area necessary to carry the electrical current to the contact tip to produce an arc. If the connection between the retaining head and contact tip isn’t secure, it can introduce electrical resistance that leads to overheating, causing the components to fail.