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GMAW gun and consumables

7 common mistakes and how to avoid them

Avoiding common mistakes and maintaining your GMAW gun and consumables properly will help you achieve good welding results and prolong the life of your equipment.

Gas metal arc welding (GMAW) offers numerous productivity benefits without sacrificing weld quality. However, many factors can interfere with successful GMAW performance.

By taking steps to avoid the following common mistakes related to your GMAW gun and consumables, you can improve performance and save money through reduced consumable waste.

No. 1: Cutting the Liner Too Long, Short

Cutting the liner the wrong length—usually too short—is a common problem in GMAW.

When the liner is the wrong length, it can become deformed by the force of the drive rolls pushing the wire forward, causing an oscillation in arc length. Like a big spring, when the liner deforms it takes up whatever free space there is in the conduit inside the gun. This can result in vibration, or “chatter,” in the gun. Ensuring the liner is the proper length can help prevent this problem.

Use a liner gauge as a guide. When installing a gun liner, make sure the gun is as straight as possible and that there is little to no twist in the cable.

Laying the welding cable flat and straight during welding will ensure the smoothest feeding. Twisting or coiling the cable can change the effective length of the liner and can cause the cable to take on a permanent set.

No. 2: Welding With Overheated Consumables

Overheated consumables—including the liner, contact tip, and nozzle—can cause a lot of problems. Be sure to use the proper wire stickout, pay attention to the gun’s duty cycle, and employ the right contact-tip-to-work distance to prevent consumables from overheating. Any steps that keep these items cooler will help limit the amount of vibration in the gun and reduce burnback.

While wire stickout that is too long is not desirable, keep in mind that stickout that is too short places the nozzle and contact tip too close to the weld pool, causing them to overheat. This hurts productivity by causing burnbacks and wire sticks and can shorten consumable life significantly.

No. 3: Using Poor Grounding

The life of contact tips and other front-end consumables can be shortened if a solid ground isn’t in place during GMAW.

Without a solid ground, the arc can become erratic and ultimately cause excessive heat buildup in the front of the gun. Anything that creates more heat also will create more resistance and more wear, damaging the contact tip and other front-end consumables and possibly affecting weld quality.

Using the wrong type of drive roll or setting drive roll tension improperly can cause erratic or poor wire feeding. For best results, consider the size and type of wire and match it to the correct drive roll.

To ensure a good ground, place the ground cable as close as possible to the workpiece. If it’s feasible, hook the ground cable on the weldment. If you can’t do that, hook it to a bench. But remember, the closer it is to the arc, the better.

No. 4: Setting Your GMAW GUN Voltage & Wire Feed Speed Incorrectly

Setting voltage and wire feed speed incorrectly can produce an erratic arc.

If you set the voltage too high, it can create too much heat in the handle of the gun, which in turn can eventually wreak havoc on the contact tip. When the wire feed speed is too fast, it can cause the wire to pile up instead of melting properly into the weld pool. This can also cause burnback or birdnesting. Wire feed speed that is too slow doesn’t feed the weld pool, so there is not proper penetration for a quality weld.

Always follow the manufacturer’s recommendations for the proper voltage and wire feed speed for the filler metal and thickness of the base material you’re welding.

No. 5: Managing Cables Poorly

Poor power cable management can lead to performance problems and cable damage. To help prevent damage or other issues, don’t pull the welding machine around using the cable. When the gun is hot, everything is more pliable. Yanking or pulling on the cable can stretch it or the liner and even cause the conduit to pull away from the gas pin, which can result in shielding gas problems.

Make sure to let the gun cool while it’s resting in a flat position, rather than draping or hanging the cable over a piece of plate or some other object. When a hot gun is draped or hung over something, the conduit can bend. When the gun and consumables cool, they can be misshaped, leading to marginal shielding gas coverage.

Also, be sure to store the gun and cable properly when they aren’t being used. Doing so will help prevent damage that can occur if a cable is run over by a forklift or other heavy equipment.

No. 6: Using the Wrong GMAW Gun

If you spend all day welding at 300 amps while using a 200-amp gun with a 30 or 40 percent duty cycle, you’ll find out that this gun will not be up to the task. Exceeding the gun’s duty cycle leads to overheating. Doing this frequently will shorten the life of the gun.

Make sure to choose the right gun for the application. Be mindful of the requirements of the job, and select a gun with enough duty cycle and amperage capacity. Also, take breaks to let the gun and consumables cool, which will further prevent overheating.

Changing shielding gas is another way you can help reduce the heat produced during welding. If you’re using an argon shielding gas, the higher the percentage of argon, the less cooling the shielding gas provides. However, keep in mind that many applications use argon shielding gas because it provides a cleaner process with much less spatter for reduced cleanup. So, while reducing the argon can help the process run cooler, there are other trade-offs that can impact productivity.

A key step to prevent your gun from overheating is to select a gun with enough duty cycle and amperage capacity for the application.

No. 7: Using the Incorrect Drive Roll, Setting

Using the wrong type of drive roll or setting drive roll tension incorrectly can cause erratic or poor wire feeding in GMAW. Consider the size and type of wire and match it to the correct drive roll.

Flux-cored wire is soft because of the tubular design and flux inside, so it requires a knurled drive roll, which has teeth that can grab the wire and help push it through. Knurled drive rolls typically should not be used with solid wire, since the teeth can cause shavings to break off the wire, clogging the liner and creating resistance in wire feeding. Instead, use U-groove or V-groove drive rolls with solid wire.

Setting the drive roll tension properly is another important step. Without the correct tension, erratic feeding can cause burnback or other problems. To set the drive roll tension correctly, start by releasing the drive rolls. Then increase the tension while feeding the wire into your gloved hand until the tension is one half-turn past wire slippage. Always keep the gun as straight as possible to avoid kinking in the cable that could lead to poor wire feeding.

Remember Routine GMAW Gun Maintenance

While avoiding these mistakes can help you achieve the best results in GMAW, it is equally important to properly maintain your gun and consumables, including the contact tip, nozzle, and liner.

Whenever you change consumables, check that the gas holes in the nozzle are clean and that the seat that holds the contact tip isn’t filled with spatter or debris. A clogged contact tip or nozzle can cause overheating in the gun and handle.

Also, check frequently that all connections are tight and as concentric as possible. Keeping the gun and cable as straight as possible during welding—and laying them flat to cool—makes for an effective and efficient GMAW gun.

Following these tips will help you minimize downtime, improve productivity and quality, and save money in your GMAW operation.

Dan Weimer is engineering lab technician at Bernard, 708-946-2281, www.bernardwelds.com.

About the Author

Dan Weimer

Engineering Lab Technician

449 W. Corning Road

Beecher, IL 60401

708-946-2281