WHAT YOU SHOULD KNOW ABOUT PULSED MIG WELDING OF ALUMINUM
Three manufacturers share their tales of pulsed MIG welding of aluminum and how new technologies have made the process more viable in their operations by reducing distortion and rework, improving productivity and standardizing wire size.
Aluminum poses a unique set of challenges – especially when it comes to welding. It has a lower relative melting point than other metals, yet requires heat to ensure proper puddle formation. Cleanliness is critical. And it is more sensitive to heat input and distortion than other metals.
Welding aluminum has traditionally been a TIG welding application and, to be sure, there are applications where TIG is still best suited. But new technology advances have made Pulsed MIG welding even more viable in applications where increased production speed is desired without sacrificing quality or appearance.
The key benefit of Pulsed MIG welding in aluminum welding applications is the balance between providing sufficient energy to ensure good fusion, yet controlling heat input to prevent warping or burn-through. In Pulsed MIG welding, the welding power source rapidly and automatically switches between a high peak current (ensuring good fusion) and a low background current (lowers heat input and reduces distortion).
Because of the pulsing of the current, the operator can vary the heat input into the parts and weld thinner gauge material without burning through or warping the part. It also creates improved aesthetics over conventional MIG welding and allows some manufacturers to standardize on a larger diameter wire for greater deposition, lower cost per pound, and simplification of inventory and equipment outlay.
In this article we will look at three manufacturers who have found recent successes with Pulsed MIG welding in aluminum applications: Greenheck Fan Corporation (Schofield, WI), Sportsfield Specialties (Delhi, NY), and Aluwind, Inc. (Castle Rock, CO).
STREAMLINED WELDING PROCESSES, SWITCHING BETWEEN METALS
Greenheck Fan is known worldwide as a leading manufacturer of quality air movement and control equipment. They offer the most comprehensive line of ventilation products in the industry, allowing a total air movement and control system to be specified from a single source.
As customer demand drove the company to shift much of its product to be fabricated of aluminum (lightweight, aesthetic versatility), the plant addressed the need to optimize its aluminum welding applications while maintaining the ability to weld mild, stainless and galvanized steels effectively. The solution was an Invision™ MPa Plus System Pulsed MIG welding system that not only improved weld quality, but due to built-in efficiencies, also helped the plant streamline its welding operations.
Matched with D-74 MPa Plus dual wire feeders, the system allows welders to quickly switch between two metals (typically aluminum and then a second wire such as stainless or silicon bronze). Built-in MIG and Pulsed MIG programs automatically set the optimal parameters for a variety of wires, and the system simplified the welding operation by using Synergic Pulsed MIG Controls and Profile Pulse™. “With Pulsed MIG programs, we can run higher wire speeds. Because of the better arc control, we run faster, flatten out our welds, get better control of our weld metal volume and eliminate overheating issues,” explains Dan Apfelbeck, the continuous improvement leader of fans and vents.
The Invision 352 MPa uses built-in Pulsed MIG programs for common 4000 and 5000 series aluminum wires ranging in diameter from .035 in to 1/16 in, as well as many of the other alloys (steel, stainless steel, silicon bronze, copper, nickel) found in the company product line. Operators previously had to set their parameters independently, but this new system ensures consistency between operators and workstations, and helps ensure quality each time an arc is struck.
“It takes the skill level of our welding group here and makes them aluminum welders,” smiles Apfelbeck. “Welding aluminum isn’t the same as giving a guy a steel gun and saying, ‘Here, weld this’. It’s a different animal. This machine plays a key role in allowing our welders to transition from a being steel operators to aluminum operators.”
Working with Pulsed MIG equipment enabled the shop to eliminate its reliance on .035 in wire for certain applications and transition to 3/64 in (.047 in) aluminum wire. “Using the new programs let us move to 3/64 in as our single wire diameter because we can now weld down to .050 in material with heavier wire and still eliminate burn-through and blistering,” notes Apfelbeck. “The larger wire diameter provides faster travel speeds, increased fill rates (deposition) and a lower cost per pound.”
It also allows the plant to simplify its equipment demands in certain departments. “In some areas, we’ve eliminated push-pull systems and gone to shorter push-only systems because of our ability to use the larger diameter wire,” adds Apfelbeck. “Our equipment outlay is much less. Maintenance and consumable costs have been reduced.”
Greenheck Fan Corporation, 400 Ross Avenue, Schofield, WI 54476, 715-359-6171, Fax: 715-355-2399, www.greenheck.com.
INCREASED WELDING PRODUCTION SPEED
Up to 50 tons per month of raw aluminum flows through the Aluwind plant in Castle Rock. Whether it comes in as sheet stock, square tube or profile stock, by the time it leaves the Castle Rock facility it has been fabricated into premium aluminum components for the wind tower industry. Aluminum is the material of choice for Aluwind because it is relatively lightweight and easy to handle, and the plant has honed its aluminum fabrication and welding practices over 17 years in business.
The shop reserves the Pulsed MIG process for welding on aluminum materials thicker than 3 mm (1/8 in and up) because it provides greater production speeds without sacrificing quality. The adjustability and performance of using a synergic AlumaFeed System enabled the shop to standardize on one type and size of wire (0.047 ER5356) and save considerable amounts of time through process efficiencies. “It just had a real nice-looking bead with Pulsed MIG,” remarks Jose Vasquez, the plant production manager. “There are some customers that require spray, but we’ve been able to prove and convince them otherwise to go with Pulsed MIG welding.”
Synergic Pulsed MIG welding gives the operator the power to adjust both the wire feed speed and the output parameters with one knob on the handle of the gun (with compatible guns). As the operator adjusts wire feed speed, the system automatically adjusts the machine’s parameters to match the change in wire feed speed. This means the welder can continuously work around the part without making trips back and forth to the machine every time a new joint configuration or thickness is encountered.
The gun also has a trigger schedule select function for the operator to toggle between two pre-set weld parameters for the 5000 series aluminum wire Aluwind uses that are built right into the machine for simplified settings. “Every one of our welders uses these features, from adjusting the power output from the gun to switching from weld mode to tack mode,” says Vazquez. “Having all of these controls on the gun definitely creates a nice smooth transition, because the welder doesn’t have to turn around and go readjust the settings at the machine. That is particularly helpful if they are on the other side of the table.”
The shop constantly moves around the platforms, making it tough for welders to go back to their machine every time and change a setting. With the synergic knob, they look over at the display, they set it, and they weld. “We do everything from vertical to horizontal and overhead in some cases, on the same part,” says welder Joe Buckley. “This means I can switch the wire feed speed right at my hand instead of at the workstation. I never have to go back over to the workstation.”
While it may not seem like a lot of time from weld to weld, the time lost tinkering with controls on the power source adds up over the course of a day. “If all you are saving is 45 minutes to an hour each day, it’s huge,” says Buckley. “Even just a few minutes makes a difference when you’re bidding competitive contracts, so we have to be as fast as we can.”
Aluwind Inc., 701 Topeka Way, Castle Rock, CO 80109, 720-236-1500, us@aluwind.com, www.aluwind.com.
IMPROVED FEEDING OF ALUMINUM WIRE
Sportsfield Specialties manufactures athletic field equipment, including goalposts, soccer goals, sandpit jumps, hurdles, high jumps and batting cages, for a wide range of sports at all levels, from youth sports up to the pros. The company specializes in modular products such as press boxes and dugouts. The majority of these products are fabricated out of aluminum and stainless steel for function, appearance and formability.
One historical problem with MIG welding aluminum is wire feeding. Being softer and more pliable than other metals, aluminum filler wire has caused frequent birdnesting that is a serious drain on productivity because it takes the operator time to purge the ruined wire, change out the contact tip (an added cost factor), re-feed the wire and start welding again.
Aluminum spool guns – MIG guns with one lb spools of wire affixed to the gun – solved some of the feeding issues but hamper accessibility to certain joints because they add bulk to the gun. They also require frequent spool changes, as one lb of wire doesn’t last long in a production welding environment. It was also standard practice to change the contact tip each time a spool was changed out, which adds further cost and time.
The shop uses a Millermatic 350P® matched with an XR™-Aluma-Pro™ MIG gun that features push-pull wire feeding technology. Push-pull optimizes feeding performance by ensuring proper drive roll tension, helping solve problems relating to birdnesting, erratic feeding and arc fluctuations. It also improves feeding to a point where the company can rely on using 16 lb spools of wire housed in the power source versus the one lb spools on the gun.
Its design is also smaller and ergonomically friendly, making it easier to get into tight spaces. “We used to weld with spool guns that were very difficult to get in some of the tight areas,” says Robert Barriger, the production supervisor. “We tried flexible nozzles, but they created too much clean up and were very time consuming. The push-pull gun makes it easier to get into tight spots, with a lot less spatter.”
With conventional MIG spool guns using one lb wire spools, one welder in the shop can go through 15 spools on a typical day. But using the XR-Aluma-Pro gun, welder Anthony Rodriguez saves considerable time changing out spools of wire. “I can put in over eight hours of work without changing the wire or the tip,” he adds. “It makes it a lot easier to work with.”
“Between changing spools from a spool gun to one of these – and having a 16 lb spool vs. a one lb spool – I can see this saving upwards of an hour a day,” notes Robert Palmer, another welder/fabricator on the floor. The elimination of frequent birdnesting with conventional spool guns that burn a lot of time during a shift, plus the additional cost of wasted wire and contact tips, is also a major timesaver. “You lose a good 15 minutes of time when the spool birdnests,” said Palmer. “Also, the tip is gone and you need to replace that, too. When you think about it, the money saved on replacing tips adds up fast.”
As with the other manufacturers, this shop has also seen general improvements in welding speed (compared to TIG) and weld quality (compared to conventional MIG). For manufacturers, these factors make a compelling argument for exploring Pulsed MIG welding in aluminum welding applications. “This gives you good appearance, with no spatter all over it,” states Barriger. “I think if you lined up and raced the Pulsed MIG and TIG, you would probably get 4 in out of the TIG vs. 12 in out of Pulsed MIG. That’s more parts per day.”
Sportsfield Specialties, 41155 State Highway 10, Delhi, NY 13753, 607-746-8911, Fax: 607-746-8481, www.sportsfieldspecialties.com.
CONCLUSION
You should know that Pulsed MIG welding technology has advanced to the point where quality, productivity, performance and aesthetics make it an excellent option in heavy production environments. Specifically with aluminum, where the equipment and programs have been designed to meet the specific demands of this challenging material. It may be worth a look.
Mike Vandenberg, Jeff Herb and Chris Roehl are product managers at Miller Electric Mfg. Co., 1635 W. Spencer Street, PO Box 1079, Appleton, WI 54912, 920-735-4162, Fax: 920-735-4013, www.millerwelds.com.
