The Drawn Arc stud welding method is a process by which a metal stud is joined to a metal workpiece by heating both parts with an electrical arc. It permits strong, one-sided welds on base metals with thicknesses starting at 0.046 in. (1.2 mm), and produces welds in as little as 0.06 sec., according to Image Industries.

Drawn arc is used in heavy construction for such applications as bridges, and in building nuclear submarines, Hobson said. The process uses a DC power supply to create the arc, a stud welding tool, metal fasteners and in some cases, ferrules. There are three common techniques:

• For drawn arc stud welding, a flux-loaded stud is put into the stud weld tool chuck, and a ferrule is placed over the end.
• In short arc stud welding, which is similar to drawn arc, no ferrule is used. This processs offers the shortest welding times of all the drawn arc stud welding options.
• The gas arc stud welding process uses insert shielding gas, and no flux or ferrule, so it is easier to automate, although it provides less control over fillets and less depth of penetration than the drawn arc process.

Hobson said that in drawn arc stud welding, the operator has to strike the arc.

“We have a lifting mechanism that lifts the arc. The operator puts the weld stud in the tool, loads a ceramic shield, positions the stud against the workpiece, and pulls the trigger on the weld tool. That sends a signal to the power supply to begin an ‘arc start’ current,” Hobson said.

The lifting mechanism in the tool is energized, and when it draws it back it establishes an arc, then turns on the main welding current and that melts the stud. The mechanism de-energizes and pushes the fastener into the weld puddle, with the whole process taking ½ sec. for a 3 in. fastener.

Terry Sterling, marketing director for the Fastener Division of Nelson Stud Welding (www.nelsonstud.com), said because stud welding is used in more than 200 industries, it is not impacted by downturns in any one industry.

“Stud welding is a growth market, especially now with many new applications in the alternative energy markets,” he said.

Nelson Stud Welding introduced a line of inverter technology equipment about a year ago that allows the company to produce a welding system that is very lightweight and portable, while delivering the energy of a larger system.

“In certain markets this is a very important feature, especially in ship building and construction,” Sterling said.

The Nelweld N1500i(tm) is a third generation inverter that Nelson offers.

It is a digital system that the company said has 50 percent more output power than comparable products. That means it can weld larger studs, weld more studs per minute and drive more cable, the company said. Nelson Stud Welding said it was designed to have precision control at 60,000 Hz frequency to ensure a stable arc, accurate heat input and high quality welds. Nelson Stud Welding said the unit can produce consistent welds despite inconsistent plate surface, the position of the weld position, and the conditions of the gun and cable. It combines control of the weld process and control of shielding gas and power in one composite cable.

Nelson Stud Welding's systems include portable equipment for electric arc, capacitor discharge and gas arc or short cycle stud welding processes, and systems that can be custom designed to meet specific requirements using an extensive array of accessories and add-on components including software.

Nelson Stud Welding builds high-production welding systems, and has provided stud welding equipment to large volume OEM customers worldwide.

The versatility and speed of stud welding is proving an advantage in many areas of construction and manufacturing because it provides freedom in designing products especially when appearance is a concern.

“As designers are trying to find new and cost effective ways of fastening components, they're looking at stud welding. If you don't want welds showing on the reverse side, stud welding is ideal because it's a single-sided fastening process. Our biggest challenge is getting to the designer to show them the flexibility and cost savings they get by using the process,” Blake Hobson at Image Industries said.