Tips to follow; pitfalls to avoid
October 20, 2011
For GMAW consumables in particular, several pitfalls exist that can shorten their life span. Taking the time to learn tips for keeping them clean and lasting longer can positively affect productivity, quality, and the bottom line.
When it comes to welding, many variables can influence productivity and quality. The power source, filler metals, and consumables all factor into the equation and require special attention during the selection process. You must manage these variables properly to ensure their longevity and to help minimize downtime for maintenance and repair.
For GMAW consumables in particular, several pitfalls exist that can shorten their lifespan. Taking the time to learn tips for keeping them clean and lasting longer can positively affect productivity, quality, and the bottom line.
The welding process generates heat that significantly affects the cleanliness and longevity of GMAW consumables. Processes like pulsed GMAW and other high-amperage applications tend to subject consumables to high heat levels, as do those that generate a lot of reflective heat. As the consumables heat up during welding, the material (usually copper or brass) becomes soft, making the surface areaa much more prone to spatter accumulation.
To avoid this problem, you must determine the best consumables for each application and manage them properly throughout the course of a welding shift. For example, high-amperage applications (above 300 amps) most often benefit from using heavy-duty consumables because they have greater mass and are more capable of dissipating heat. However, if the welding procedure requires you to change the contact tip frequently, a standard-duty contact tip may suffice.
Your goal should be to determine which consumables—heavy- or standard-duty—are most capable of withstanding the duty cycle and heat of the application. A reliable welding integrator often can help you make this determination.
When used sparingly, antispatter compound can help keep GMAW consumables clean in both semiautomatic and robotic welding applications (see Figure 1).
In a semiautomatic application, dip only the front 1.5 in. of the nozzle into the antispatter compound. Submerging the entire nozzle can saturate its fiberglass insulator and potentially plug up the gas holes on the diffuser. This buildup may cause premature nozzle failure or unbalanced gas coverage that can lead to weld porosity.
In robotic applications, use the minimum amount of antispatter compound required for the application. Too much antispatter can build up on the consumables or cause the nozzle to become clogged with debris, leading to poor gas coverage, inconsistent electrical conductivity, or shortened consumable life.
Another important way to combat spatter is to inspect the nozzle for buildup on a regular basis and clean it with a soft wire brush or spatter-cleaning tool as needed. Never hit the nozzle against the tooling or workpiece to loosen spatter. Doing so can dent, misshape, or compromise the smooth surface finish of the nozzle, which creates greater areas for spatter to adhere to and reduces the life of the consumable.
Always keep GMAW consumables in their original packaging until they are ready for use. Opening them and placing them in a bin can lead to scratches or dents that allow spatter to adhere and will ultimately shorten the products’ life. Similarly, removing contact tips or diffusers from their packaging and storing them in open or dirty containers can cause dirt and oil to accumulate in the threads, which can impede their properly seating together.
Keep storage containers for new consumables separate from those for discarded ones to avoid selecting an old contact tip or nozzle that may have dents or scratches and be prone to spatter accumulation. Always wear clean gloves when handling or replacing contact tips, nozzles, and diffusers to prevent dirt, oil, or other contaminants from adhering to them.
Installing GMAW consumables correctly and inspecting them periodically for good connections minimizes the chance of poor conductivity and the spatter accumulation or premature failure that can result. Always follow the GMAW consumable manufacturer’s suggestions for installing contact tips and gas diffusers. Use a pair of channel-lock pliers or other recommended installation tools to install tips and diffusers. Never use wire cutters or side cutters, as too much pressure from these tools can damage the inside diameter of the contact tip. These tools also tend to scratch the surface of the consumables, leaving marks that attract spatter.
A good rule of thumb is to hand-tighten the contact tip until it is fully seated into the diffuser, then grip the contact tip with an appropriate tool as close to the base as possible, tightening it one-quarter to one-half turn past finger tight. This procedure helps ensure a good connection, minimizing electrical resistance, overheating, and damage to the consumables, as well as excessive spatter accumulation. Follow the same procedure for installing and tightening the diffuser so that it fully connects with the gooseneck.
Some contact tips can be installed and held in place by hand-tightening the nozzle. Check the manufacturer’s recommendation for proper installation instructions.
Inspect consumable connections regularly to ensure that they are secure.
A liner that is trimmed and installed improperly can cause a host of wire feeding problems that require downtime to rectify (see Figure 2). It also affects GMAW consumables’ performance, cleanliness, and longevity. Cutting a liner too short causes the liner to misalign with or in the gas diffuser. A misaligned liner will feed the wire off-center, and the contact can fail prematurely as a result.
Debris often builds up between the liner and the retaining head when the liner is too short, causing wire feeding issues and poor weld quality. In some cases the gap that is present between the gas diffuser and liner when a liner has been cut too short will cause the welding wire to catch, shaving off a tiny portion of the wire. The small shavings can plug up the contact tip and cause it to fail quickly.
A liner that’s too long can kink, which again leads to wire feeding issues that shorten the life of the contact tip. Always be sure to remove any burrs or sharp edges after cutting a liner to ensure smooth and consistent welding wire feeding.
Always consult with the liner manufacturer’s recommendation for proper trimming and installation instructions. Also be sure to wear gloves when handling the liner, and avoid dragging it on the ground to keep debris away from the GMAW gun. Debris can contaminate the weld and hinder consumable performance.
The position of the contact tip (extended or recessed) affects consumable lifespan and cleanliness. The nozzle used in conjunction with a specific contact tip and the wire size also makes a difference. The farther the contact tip extends from the nozzle and the closer it is to the arc, the more prone it is to damage from reflective heat by way of spatter accumulation and burnbacks. A recessed contact tip can help prevent these problems while also providing better shielding gas coverage.
For applications that require access into restricted areas, it is important to select a nozzle that provides that access but isn’t tapered so much that it impedes the space around the contact tip. If there isn’t enough space for shielding gas to flow out of the nozzle, the shielding gas could hit the workpiece and begin jetting back or swirling. This action pulls oxygen into the weld pool and increases the risk for spatter. As the bore size on the nozzle decreases, there is less mass to that portion of the consumable, increasing the risk for heat absorption and spatter adherence.
As a general rule, select the largest consumable that will work for the application while still providing necessary joint access. Larger consumables are more able to resist heat and spatter buildup, and they often last longer as a result.
Selecting consumables with the right material for the application is important too. For example, brass nozzles tend to resist spatter well and are good for lower-amperage applications (100 to 300 amps), whereas copper nozzles are better for high-amperage applications (more than 300 amps) or for those with longer arc-on time.
Lastly, always pay attention to the manner in which you manage consumables. Using the same consumables throughout the welding operation can help you to maintain consistent performance and troubleshoot problems more quickly when they occur. The result can be longer-lasting, cleaner consumables that provide more reliable performance and quality.