Miller's Accu-Pulse™ Pulsed MIG Technology Tackles Exotic Metals, Provide 15 to 20 Percent Improvement, 1 Year Payback

Executive Summary

• Faster travel speeds (compared to short circuit transfer, or SCT)
• Higher deposition rates and deposition efficiency (compared to SCT)
• Reduced spatter for less clean-up time (compared to SCT)
• Minimized distortion (compared to spray transfer)
• Flexibility to weld thick or thin sections
• Lower fume emissions
• All-position welding (spray transfer is limited to the flat and horizontal positions)

New Pulsed MIG Technology Tackles Exotic Metals, Provide 15 to 20 Percent Improvement, 1 Year Payback

Tom Vincent uses the Accu-Pulse process to weld copper pipe that will help cool the side wall of an electric arc furnace As lead welder for aluminum-bronze and copper welding, Tom Vincent has taught 13 other AmeriFab welders how to weld with Miller’s Axcess 450 multi-MIG system and the Accu-Pulse process.

“I always said that pulsed MIG was made for welding aluminum bronze,” states Tom Vincent, lead welder at AmeriFab, Inc., the leading American engineer /fabricator of steel mill equipment.

Vincent explains that the aluminum bronze weld puddle is so fluid that it’s almost like water. “It drips,” he says, “and that makes it hard to carry the puddle uphill. But with Miller’s Accu-Pulse™ pulsed MIG process, welding aluminum bronze is like painting it on with a paintbrush. The metal sticks, and there’s no spatter. We achieved good results because we could adjust the pulsed MIG waveform to change inductance, which stiffened up the weld puddle. Now the puddle stays in the joint when we’re welding vertical up on pipe.”

Accu-Pulse is one of the unique GMAW processes available from Miller Electric Mfg. Co.’s Axcess® 450 multi-MIG systems. AmeriFab tested its first Axcess system in early 2006 and now has 14 systems. Because pulsed MIG provides better puddle control, and because Accu-Pulse technology adapts to individual operator preferences, operators can produce a better quality weld in less time and with less grinding or rework. As a result, AmeriFab estimates it improved productivity 15 to 20 percent in aluminum bronze and copper welding applications. These improvements produced a payback time of approximately one year.

American Innovation

AmeriFab (www.amerifabinc.com) of Indianapolis is one of the few companies to sell, engineer and manufacture equipment all of its own steel mill equipment. Having resources in one location enables the company to react quickly to customer needs, and it makes innovation easier.

“If we see customers having a problem, we don’t just reiterate the problem. We improve our equipment to provide a solution,” says Rick Manasek, title, AmeriFab. “If we can save customers money and time while providing them with quality equipment and a fair price, we believe they’ll stick with us.”

One such time saving innovation is a patent-pending aluminum bronze pipe for water-cooled ductwork whose heat transfer characteristics exceed those of normal steel (see Fig. 1). This pipe resists acidic attack while reducing the chance of thermal cracking. It extends periods between scheduled maintenance shutdowns, which is essential. Due to increased velocities and increased thermal loads caused by operating practices of modern electric arc furnaces and basic oxygen furnaces (BOFs), severe corrosion and abrasion are common problems within water-cooled ductwork.

Fig. 1–Aluminum bronze pipe is harder than steel, which reduces abrasion. It is a better thermal conductor than steel and possesses a better elongation capability. This reduces the chances of thermal cracking, making it the ideal material to build water-cooled duct and BOF hoods.

When welding copper, pulsed MIG provides better results that conventional MIG processes. The pulsing action agitates the weld puddle and pushes contaminants (copper carbide) out of the way.

AmeriFab is also known for welding water-cooled copper components for electric arc furnaces, such as sidewalls and roof panels. The thermal flux rate of copper versus steel allows for a much faster heat transfer. With power input into furnaces increasing, coupled with the need to reduce downtime, copper components become economically attractive. However, like aluminum bronze, copper is a challenge to weld using short circuit transfer or spray transfer MIG.

“The hard part about welding copper is keeping the puddle clean,” says Vincent. “The molten copper picks up scale from the puddle and the welding wire. Even with clean metal and filler wire, a copper carbide scale forms on top of the puddle. We can’t weld over the top of the scale because that creates holes and impurities in the weld. Pulsed MIG solves the problem because the pulsing action agitates the puddle and creates a cleaning action that pushes the carbide scale out of the way. The scale collects in front of the puddle, and the pulsing action keeps pushing it away. Pulsed MIG creates a very clean weld.”

Continuous Improvement

Manasek says that, “Our purpose is to build the best steel mill equipment available. As the premier manufacturer, we have an obligation and a philosophy to find the best equipment and method to do so. For us to invest in new pulsed MIG systems or other equipment, it signals that we’re seeking to do a better job all the time.”

He knew that the pulsed MIG process could improve aluminum bronze, copper and other welding applications. The classic benefits of pulsed MIG are:

• Faster travel speeds (compared to short circuit transfer, or SCT)
• Higher deposition rates and deposition efficiency (compared to SCT)
• Reduced spatter for less clean-up time (compared to SCT)
• Minimized distortion (compared to spray transfer)
• Flexibility to weld thick or thin sections
• Lower fume emissions
• All-position welding (spray transfer is limited to the flat and horizontal positions)

AmeriFab would benefit from pulsed MIG’s all-position ability. Most of its weldments weigh thousands of pounds. With conventional technology, the company needed to either take the time to move the weldment to make welds in-position or use the slower but cooler short circuit transfer process to weld out-of-position. The complex geometry of pipe welding typically demands welding out-of-position, and most procedures specify welding vertical up to ensure good fusion (and prevent cold lap).

However, AmeriFab, like many high volume fabricators and manufacturers, did not adapt older pulsed MIG technology because of its drawbacks.

“I can’t speak for all of today’s systems, but I could tell you in the past it was very difficult to be consistent and to train people to use the pulsed MIG controls,” says Manasek. “Providers talked about these synergic controls and so forth. They weren’t very operator-friendly, and I think it discouraged people from using them. Having tried various pulsed machines, I can tell you that they were short-lived as far as our attempt to go forward with more machines.”

In addition to pulsed MIG welding on aluminum-bronze and copper, AmeriFab uses Axcess to weld cooling systems made from A106B carbon steel using processes like short circuit transfer MIG.

Comfortable and in Control

Within the last five years, newer pulsed MIG technologies have been developed to specifically address the ease-of-use issue. For example, Accu-Pulse gives operators only three easily adjustable controls: wire feed speed, arc length (called Arc Adjust) and arc cone width (called Arc Control).

When introducing pulsed MIG technology to operators whose personal comfort zone and experience is with traditional MIG or flux cored welding technology, the biggest obstacles are arc length and arc control. In the past, the limits of available pulsing technology forced operators to weld with a longer arc length to help prevent short circuits (“wire stubbing”), resulting in spatter. Longer arc lengths (about 3/4-in.) increase the difficulty of controlling the weld puddle (imagine trying to slowly push a billiard ball around with a pool cue). Longer arc lengths also tend to produce undercut if travel speeds are not reduced to compensate, which in turn leads to over-welding.

Accu-Pulse enables operators to adjust the arc length to one that meets their personal preference–generally in the range of 3/8 to 1/2 in.–regardless of electrode stick out. Further, Accu-Pulse produces a more focused arc column so operators have excellent directional control over the weld puddle. In addition, Arc Control lets operators adjust the width of the column, such as narrow column for deep joints or inside corners and a wide column for cover passes or to catch both sides of joint. Where old technology forced the operator to adapt, new pulsed MIG technology adapts to operator’s individual preference and keeps them in their comfort zone.

The entire Axcess 450 system fits onto a wheeled cart that enables operators to move it around the large weldments that are typical of AmeriFab products.

New technologies such as Accu-Pulse offer the following benefits (and maintain all the positive aspects of pulsed MIG as noted above):

• Easier to modify waveforms
• Improved travel speed
• Colder (less heat input)
• Reduced undercut
• Better puddle control
• Reduced distortion
• Less spatter
• Improved arc stability
• Reduced overwelding
• Better overall operator appeal

After seeing Miller’s Axcess systems at the 2005 AWS/FABTECH show in Chicago, Manasek asked his long-time distributor, Steve Werner of Sutton-Garten, for a more in-depth demonstration. Vincent, the lead welder on aluminum bronze and copper, would test the first system.

“You could read the manual,” says Vincent, “but the best thing to do is have someone turn the control knobs while you’re welding. Everyone here was used to setting voltage and amperage with conventional MIG. To take the confusion out learning Accu-Pulse, you need to experience the results of Arc Adjust and Arc Control rather than just reading about them.”

Acquisition and Training

Vincent tested AmeriFab’s first Axcess for several months. After continued success, he and Manasek decided on a two-pronged plan. First, the company would begin replacing some of its older, less efficient welders with Axcess systems. Second, AmeriFab would target the new Axcess systems at operators for whom the new technology would have the biggest impact. These tended to be more experienced operators welding on tougher jobs. Vincent worked with these operators in a designated training area until they were completely comfortable with the equipment and the Accu-Pulse process. Training typically took one or two weeks.

“Proper training is the key to success when introducing new equipment and technology,” states Manasek. “If I put you behind the wheel of an Indy car and you don’t know which buttons to push, you’re not going to get off the starting line. Without instruction, you’ll be intimidated by the technology, and that creates problems. Change is difficult for anyone without proper information and training, which is why we work with operators until they feel comfortable with new equipment and can see its benefits. Our training philosophy makes a big difference with the acceptance rate.”

As of November 2007, AmeriFab has purchased 14 Axcess systems, which are located in three different buildings, two of which are offsite from the headquarters facility. To ensure consistency between locations and operators, Vincent uses his Palm OS-based handheld as a file management tool.

“I use my Palm to download the same pulsing programs to all 14 machines and lock the operators out of the program. I give them recommended parameters for wire feed speed, Arc Control and Arc Adjust. They can change those parameters to suit their preference, but they can’t accidentally delete the program or change the waveform.”

Manasek comments that, “When you can lock in essential variables, it makes a big difference with consistency of our quality. We build premium equipment, and these pieces are critical steel mill components. Because we can control critical welding variables, it offers comfort to ourselves and to our customers.”

Even though the Axcess multi-MIG system is one of the welding industry’s most advanced products, it is also one of its most operator-friendly systems.

If AmeriFab wanted to control parameters even more closely, Vincent could use his Palm to give operators a limited window of adjustment for wire feed speed, Arc Control and Arc Adjust values.

Worth the Investment

In addition to targeting its most skilled welders, “AmeriFab has used Axcess to improve operator performance,” says Werner of Sutton-Garten. “One huge benefit of new pulsed MIG technology is that you can take a welder who is maybe a B or C+ player and turn them into an A player. Axcess enables them to increase their skill levels faster compared to training on a conventional machine. It provides them with more tools to control the arc, and those tools are easy to use. Further, Accu-Pulse provides operators with better puddle control, which enables them to put in a better quality weld.”

Manasek does note that AmeriFab still purchases conventional technology welders, mostly Miller’s Deltaweld™ 452 and 652 models paired with Miller’s 70 Series dual reel digital wire feeders and Tregaskiss’ air-cooled TOUGH GUN® MIG torches. The Deltaweld works well for applications where AmeriFab welds carbon steel (of which there is a lot) and/or uses standard MIG and flux cored processes.

“We buy about two Axcess 450s to every Deltaweld,” Manasek says. “We’ve been in business for 15 years, and a lot of our older Miller welders are becoming inefficient. Those are the systems we target for replacement, typically two or three at a time.”

AmeriFab proves its commitment to continuous improvement through its capital investments. An Axcess 450 multi-MIG system costs about one-third more than a Deltaweld 452-based system, even though both have the same welding output. However, because Axcess is software-based system, its never becomes obsolete. If Miller makes a process enhancement or develops a new program, Vincent can receive the program via e-mail, load it into his Palm and then update the software on all of the company’s Axcess systems.

While a software-based welding system and using a Palm may sound intimidating, it isn’t. Vincent notes that although he is not computer savvy, he found Axcess and the Palm easy to use after demonstration and coaching from Steve Werner.

Manasek sums up AmeriFab’s experience succinctly, saying, “The fact that we have 14 new Axcess machines here tells you that we’ve had success training our people, that they’ve accepted the controls and that they’re simple to use.”