Straight Shooters: Ruggedness and Flexibility Define Reliable Flux-Cored Welding Guns
Construction sites and outside welding yards are no place for delicate or inefficient equipment. Filled with dust, debris and heavy materials in every corner, and frequently exposed to the elements, the typical field welding site can be a challenging place for even the most robust welding operations.
In an environment like this, the self-shielded flux-cored welding process is generally preferable to the gas-shielded process for two reasons, says Tom Myers, Senior Application Engineer for Lincoln Electric. “One is just the reliability of the self-shielded process, even when there’s wind at the welding site. You can weld in wind up to 30 miles per hour, and you still won’t get the contaminants that you can get when the wind blows away your external shielding gas. Two is the portability. You don’t have to haul the extra shielding gas tanks around, and you don’t need an additional gas line.”
But the self-shielded flux-cored welding process is only as efficient and productive as the gun the operator holds to perform the welding. A welding gun designed for self-shielded flux-cored welding performs two important functions – cradling the wire coming from the wire feeder and extending the welding circuit out to the contact tip.
“The gun is basically a series of copper strands and tubes with an insulated outer jacket and an insulated hole or liner in the middle that the wire travels through,” says Myers. “So it’s transferring electricity all the way out to the contact tip. At that point, the wire touches the contact tip and becomes electrically charged. The wire is not energized until it gets to very end of the gun.”
That efficient transfer of electricity is not only a defining factor in the welding operation, but also in welding safety. “From the wire feeder to the contact point, every time electricity flows from one conductor to another within the gun, you need a nice, tight connection,” says Myers. “If you have a loose connection, you lose current and you lose efficiency. And it also heats up if you have bad connections. It’s primarily wasted energy, but it’s also a safety issue if the gun overheats. It can become too hot to hold, or potentially start a fire.”
A good gun also balances durability and comfort, Myers adds. “You want a gun that’s rugged, because it has to hold up to being dragged around,” he says. “But you also have to hold the gun all day long, so you don’t want it to be too heavy. It has to be lightweight and the cable must be flexible. Handling the gun for long hours has to be comfortable for the user.”
But even the most efficient gun is subject to damage on the construction site. Common threats are falling objects or heavy equipment running over the gun.
“A piece of steel might fall on the gun or a forklift may run over it and crush part of it or deform part of it,” says Myers. “Maybe not to the point where it’s severed, but enough to prevent the wire from smoothly feeding through it and thus resulting in unsteady wire feeding.”
While crushing incidents can damage a gun quickly, the general wear that results from repeated bending, flexing, and dragging over rough surfaces can be just as detrimental over time, he adds.
“Another concern is contaminants like dust, grease or metal shavings getting into the gun,” says Myers. “The liner that the wire feeds through is not much bigger than the diameter of the wire itself. So it doesn’t take much for contaminants to enter the system at the drive roll end and get compacted in there. That can be restrictive to the feeding process. It makes it harder to push the wire through.”
Damage to the gun inevitably results in bad welds. A cut or a kink in the gun’s internal liner, or damage to some other part of the gun that pushes against the liner, will hinder the smooth feeding of wire, says Myers.
“This may cause excessive dragging of the wire through the gun, which overburdens the drive motor in the wire feeder,” he says. “This could potentially stall out the motor, and even damage it. In addition, the wire could feed out of the gun in a jerking or surging motion. This in turn produces an erratic arc and poor welding conditions. The resulting weld would then be inconsistent.”
Damage to the copper stranding in the gun cable and/or the copper tubing in the gun handle and gun tube, as well as damaged or loose connections between these components, could decrease the welding current. “A drop in current would cause the welding to be ‘colder,’” says Myers. “This could also result in poor weld quality.”
General awareness of these hazards during operation is a good way to prevent damage to the gun. “Try to keep it as straight as possible, or keep it in a big loop, versus coiling it up numerous times,” says Myers. “Avoid sharp bends as much as possible, and be cautious of materials around the gun that could fall on it. When the gun is not in use, try to wrap it around the wire feeder, as opposed to just leaving it lying on the ground.”
As for contaminant buildup on the inside, regular maintenance is key. “You can take an air hose and blow out the gun every so often. With the older self-shielded guns, the liner inside is not changeable, so you have to periodically detach it from the wire feeder and blow air through it. With the newer guns, you can actually change the liner out. It’s meant to be removed on a periodic basis and thrown away so you can replace it with a new one.”
In the end, the self-shielded flux-cored welding gun is one of the most important parts of the welding system. “It’s the part the operator holds in his or her hand, and it’s probably the part of the system that’s subject to the most movement and repositioning,” says Myers. “So it has to be rugged yet flexible. If you use it properly and take care of it on a regular basis, it’s the ideal tool for field welding.”