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Oct 30, 2018

Manufacturer Relies on Hobart Filler Metals to Produce Military Equipment

The critical medical devices manufactured by Fort Defiance Industries (FDI) are used by the U.S. military and disaster relief operations in life and death situations where the stakes are high. Product quality and reliability are critical.

“In everything we do, we really try to exceed expectations and deliver excellence,” says Chris Yerger, Fort Defiance Industries chief executive officer.

Launched 12 years, the company has steadily grown and added product offerings at its Loudon, Tennessee, facility. FDI became known as the “can-do company” for its ability to solve problems for customers, especially the U.S. Department of Defense.

Close-up of welder TIG welding on aluminum pressure vessel

Fort Defiance Industries manufactures the steam sterilizers to ASME Section VIII Division 1 welding code for boiler and pressure vessels, using Hobart MaxalTig 4943 aluminum filler metal.

“If the military had an issue, we said ‘we can do it, we’ll help you solve that problem,’” Yerger says. “So that reputation was developed early on.”

While Fort Defiance Industries manufactures a variety of products — from water systems to pumps and electrical panels — a key offering is an automated field steam sterilizer produced for the Department of Defense. The units can sterilize 36 pounds of surgical instruments per load and process 100 loads using only 10 gallons of water. They’re also designed for easy transport and setup.

The steam sterilizers undergo rigorous quality testing to ensure high reliability in remote and harsh environments. Choosing Hobart® MaxalTig® 4943 aluminum filler metal for manufacturing the sterilizers resulted in significantly better weld strength compared to other options FDI considered.

“We wanted to do everything we could to still have good weldability, really good aesthetics, but also have as strong a weld as we possibly could,” says Ken Owens, FDI welding team leader. “It was clear the 4943 would give us increased strength.”

Quality is the top priority
The autoclave sterilizer, which contains a pressure chamber where the sterilization happens, is fabricated from 6061 aluminum alloy, so it’s lightweight for portability but also very strong and rugged for field conditions. The design uses a variety of weld joints, including full penetration v-groove joints and various sizes of fillet welds.

Environmental shot of welding lab with safety screens
Tennessee-based Fort Defiance Industries engineers and
manufactures medical devices used by military field hospitals,
disaster relief operations and remote area clinics.

The company’s autoclave design is unique because it’s automated and also features a closed-loop system with water recovery capabilities, making it more efficient and reliable. Previous field steam sterilizer designs used almost 2 gallons of water with every cycle and they were manual, which required someone to monitor the system and adjust valves for the sterilization process to work properly.

Because the application requires leak-tight welds with high strength, Fort Defiance Industries manufactures the sterilizers to ASME Section VIII Division 1 welding code for boiler and pressure vessels. All the company’s welding operators are also X-ray and 6g pipe welding certified. FDI is also certified to ISO 13485 standards, which are stringent regulatory requirements for medical devices.

Using welding procedures and filler metals that reduce the risk of porosity is another key factor in the success of producing this equipment.

“We’ve got to stay focused on the quality of our welds. If we don’t do this well, we have something that could rupture and potentially cause harm,” Yerger says. “We have to follow very strict procedures.”

Increased weld strength
In bidding for the contract to produce the field sterilizers, Fort Defiance Industries had to quickly develop a prototype that was reliable, durable and stood up to rigorous testing. It was clear that selecting the right filler metal was an important part of the equation to ensure the necessary weld quality and strength.

FDI compared the 4943 aluminum filler metal with a 4043 filler metal, using in-house tensile testing. The company also sent the welds to outside certified labs for extensive testing.

“The tensile strength was the biggest thing,” Owens says. “We saw about 2,000 psi bump in tensile strength with the 4943.”

Welder TIG welding on end of aluminum pressure vessel
The 4943 filler metal provides a 2,000 psi bump in tensile strength compared to 4043 filler metal, while also delivering weldability, a fluid puddle and good aesthetics in the finished product.

It was also important for the company to choose a filler metal with consistent weldability, a fluid puddle and one that produces proper aesthetics in the finished product.

“It’s just an all-around good rod. We get the extra strength we’re looking for, and it has great weldability,” says Tim McKee, a Fort Defiance Industries welder. “We have a little bit of everything on this pressure vessel — all kinds of different welds. We don’t have to go back and do a lot of fixing because it’s right the first time.”

A Hobart representative helped FDI adjust welding parameters with the 4943 rod, including recommendations for the best way to prevent porosity in the application. Using the 4943 filler metal, Fort Defiance Industries has manufactured about 180 steam sterilizers and will produce hundreds more to satisfy the government contract it secured. The company also hopes to expand to more international military customers.

The right rod — and a versatile machine
Fort Defiance Industries requires a welding power source that offers the flexibility to weld very thin sheet metal up to 1-inch-thick materials. They turned to Miller Electric Mfg. LLC, a welding equipment manufacturer also owned by Hobart parent company, Illinois Tool Works (ITW).  The Miller® Dynasty® machines they chose to use in the manufacturing operation are programmable, so operators can pre-program their preferred settings and easily cycle through them with the touch of a button to make changes. This helps save time in setup and parameter changeover.

“The speed between jobs is a benefit,” Owens says. “You don’t have to come back to the machine and dial in settings. They’re already there and you know what program to use, so each welder can tailor the arc to his needs.”

The machines also deliver a more focused arc for better penetration. The ability to dial in the arc is especially helpful in tight weld joints.

“We can really fine-tune to get into that tight joint or to help us out on the porosity side, to where we have little or no porosity,” McKee says.

Three autoclaves partially built, including front door and pressure vessel body
Fort Defiance Industries’ main product is an automated field steam
sterilizer used by the U.S. military in field hospitals, shown here
in the process of production.


The machine’s wireless foot pedal also helps improve productivity, maneuverability and reliability by eliminating the control cable — saving time in cable management and reducing clutter in the work area.

“I love the wireless foot pedal,” McKee says. “They’re great machines. We can focus it in and do a really good job.”

Seeing results
Hobart was a partner in the welding process from the beginning, helping FDI assess and determine the right procedures and filler metal for the job.

“It’s been a very positive experience,” Yerger says. “Hobart has been very helpful and supportive of what we’re doing here at Fort Defiance Industries.”

“We knew we would get extra strength from it [4943], and that gave us a lot of peace of mind,” Yerger says. “It’s a big deal from a safety standpoint, so that increased strength was the primary reason we went with the product.”

 “We’re building something for our military,” McKee adds. “You don’t want it to fail.”