Armor plate fabricator implements two-team welding/cleaning process
May 4, 2010
Like many companies, Ultra Machine and Fabrication Inc., Shelby, N.C., a fabricator of armored military vehicles, believed the welders should clean up their own weldments for spatter, slag, and other discontinuities. But when welders were spending less and less time under the hood, Ultra re-evaluated this philosophy and, as a result, implemented a separate postweld cleaning team.
“To serve those who protect.” It’s not the official motto of Ultra Machine & Fabrication Inc., but it sums up why people enjoy working for the company. At least that’s what Bob Dawson, director of welding, said.
“It’s a joy to be a part of something that we know is saving lives and protecting the men and women who are currently serving [in the military],” Dawson said.
In business since 1989, the Shelby, N.C.-based company has carved a niche by specializing in the forming, fabricating, and welding of armor plate for military all-terrain vehicles. The company has six welding robots in commission, but because of the size of its weldments, which generally weigh about 14,000 lbs., it relies heavily on manual welding processes, primarily flux-cored arc welding (FCAW) with a E71T-1M wire and GMAW-P with stainless steel wire. All of Ultra’s 200 certified welders are qualified to AWS D1.1/D1.1M:2008—Structural Welding Code-Steel; AWS D1.2/D1.2M:2008—Structural Welding Code-Aluminum; Dwg. 12479550—Ground Combat Vehicle Welding Code-Steel; and Dwg. 12472301—Ground Combat Vehicle Welding Code-Aluminum, as well as many other AWS and military codes and specifications.
“The military specifications are a little more detailed and critical than, let’s say, the structural welding code D1.1. It’s more in-depth and has tighter tolerances on the acceptance criteria,” Dawson said.
Welding armor plate is tricky business, especially given the tight heat input requirements. Regular structural steel components allow for up to 500-degrees-F interpass temperatures. Armored material, however, allows only up to a 300-degree-F interpass temperature. This makes weld sequencing critical to ensure that heat is dispersed properly throughout the part, preventing it from building up in one area. If the heat is not dispersed properly or if the 300-degree-F temperature barrier is broken, the weld is susceptible to hydrogen-induced cracking.
With the lives of servicemen and -women hanging in the balance, acceptance criteria at Ultra are heavily scrutinized. While the integrity of the weld is of the utmost importance, the appearance of the weld and the areas around it also is important.
“The military really pays attention to detail. I’ve been welding for 30 years, and if I see one area of discontinuity or spatter, it forces me to look at the weldment even harder. If I look at a part and it’s immaculate, it won’t get critiqued as thoroughly,” Dawson said.
Dawson was brought up with the idea that welders should clean up their own welds, and that’s exactly what they did. Welders at Ultra would finish laying a weld, remove their helmet and other PPE, grab their grinding mask and safety glasses, and grind away spatter or other surface imperfections before sending their weldment off for inspection. This wasn’t difficult work, but Dawson and Ultra International Vice President Gary Farmer realized that asking welders to weld and perform postwelding duties was an inefficient practice that took welders away from what they were being paid to do—weld.
“It’s kind of hard to have a highly paid welder operating a grinder when we need him to be under the hood welding,” Dawson explained.
Productivity was suffering as a result of the low arc-on time, but cutting down on postweld cleanup was not an option. This rationale prompted Dawson, Farmer, and others at Ultra to re-examine its operation and develop a practice that would make its welders more productive. That’s when Farmer implemented the two-team welding and cleanup process. The philosophy was simple: Let the welders do the welding, and form a separate crew to perform all postweld processes.
Implementing the process was easy. The company hired an entry-level work force to serve as the cleanup team and put them through a training regimen.
“We already had people on staff who weren’t hired as welders who agreed to do it. We trained them in blueprint reading, geometric dimensioning and tolerancing (GD&T), and symbol reading so they could read a print and know if a weld needed to be profiled and, if so, how to do that,” Dawson said.
The benefits to having a separate cleanup team were immediate. First, it allowed welders to concentrate fully on laying critical weld passes that would stand up to strict military acceptance criteria and pass final inspection. Second, with a higher arc-on time, weld production rates naturally increased. Dawson said that the system, on average, has cut four hours of production time per vehicle.
“When this project first started, it took a four-man welding team approximately 14 hours to complete each vehicle. Once we implemented the two-team process, a four-man welding team completed the vehicle in eight hours and the cleanup team cleaned each vehicle in about two hours. A vehicle comes off the line every 10 hours. I would not be afraid to say that when things are running smoothly, our procedure cuts five to six hours off the entire process.”
The training that the cleanup team received helped them to serve as another layer of inspection of the weldments. If an irregularity is spotted during postwelding processes, the cleanup team is authorized to stop the line and alert the certified welding inspector (CWI). For a recent project in which the company shipped more than 43,000 parts, only one was rejected, “and that wasn’t even due to welding; it was more of a dimensional problem. I think our numbers really speak for us,” Dawson said.
Starting out as a grinder at Ultra is in no way a dead-end job. On the contrary, Dawson noted that 40 to 50 percent of its work force started out as grinders.
“These guys are not just people who run grinders. They are trained in other areas as well, and many of them take the initiative to go beyond that.”