Fan Manufacturer Standardizes on Pulsed MIG Welding for Aluminum
Greenheck Fan discusses the advantages of Pulsed MIG welding on aluminum
The greatest challenge with welding aluminum is that it is easy to burn through and/or cause distortion. The key benefit of Pulsed MIG welding in this application is the balance between providing sufficient energy to ensure good fusion yet controlling heat input to prevent warping or burn-through.
Greenheck Fan Corp.’s tagline—Building Value in Air—applies to every facet of its business. As customer demand drove the company to shift much of its product to be fabricated of aluminum (lightweight, aesthetic versatility), Greenheck addressed the need to optimize its aluminum welding applications while maintaining the ability to weld mild, stainless and galvanized steels effectively. The solution: an advanced Pulsed MIG welding system (Miller’s Invision™ MPa Plus System) that not only improved weld quality, but due to built-in efficiencies, also helped the company streamline its welding operations. Improvements include:
- Improved welding of thinner aluminum (reduced burn-through, blistering, reduced distortion).
- Improved productivity (faster travel speeds).
- Improved starts and stops to the weld (ensures quality).
- Standardizing on a larger diameter wire (greater deposition, lower cost per pound, simplification of inventory and equipment outlay).
- Dual wire feeder makes it fast and easy to switch between types of filler metal.
- Improved weld aesthetics compared to conventional MIG welding on aluminum.
“With the Pulsed MIG programs, it has made aluminum a lot easier to weld,” says Ken Tucker, continuous improvement leader—Facility 8, Greenheck. “It used to be very hard to weld thin materials. Now it’s a lot easier, a lot faster. It’s easier on the welding operator. You can pick up the lead, punch in the program on the machine, choose your wire and you’re off and running.”
A Worldwide Leader
Greenheck 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.
Greenheck air movement and control equipment is used in commercial, institutional, and industrial facilities, ranging from comfort ventilation to manufacturing processes. Founded in 1957, the company got its start as a sheet metal shop. Today, it has more than 2,400 employees, facilities in multiple states as well as China and Mexico and a line of hundreds of products including fans, dampers, louvers, kitchen ventilation systems, make-up air units, energy recovery systems and laboratory exhaust systems.
At any time, welding operators may be working on steel from 20 gauge to 1/2-inch, aluminum from .080-inch up to 1-inch, 18 gauge galvanized and stainless steel, and some copper parts. To simplify welding operations and training, Greenheck has added numerous Invision 352 MPa systems across multiple facilities for its ability to weld on a wide variety of materials and thicknesses. 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 also features Synergic Pulsed MIG Controls and Profile Pulse™ to simplify welding operation in difficult applications such as aluminum.
Growth in Aluminum
Greenheck has substantially increased its aluminum product offering based on customer demand. One key advantage is that aluminum is more versatile.
“Louvers and sun shades are outside the building, so they need to be more decorative,” says Dan Grabko, continuous improvement leader for Greenheck louvers and dampers. “We can anodize and paint aluminum, and make many kinds of shapes. We’ve had requests for some very unique shapes, and aluminum gives us the flexibility to make those shapes.”
Another reason for an increased demand for aluminum is that it’s lightweight for fan wheels and centrifugal products.
“Our customers are increasingly asking for smaller units made of aluminum to build a bank of smaller fans, so if one goes down for maintenance, there is still sufficient airflow,” says Tom Wirtz, continuous improvement leader, Greenheck. “With a single big fan, if it goes down, everything stops. Due to this increased demand for smaller units, we need to keep up productivity to satisfy our customers.”
Heat Under Control with Pulsed MIG Welding
The greatest challenge with welding aluminum is that it is easy to burn through and/or cause distortion. The key benefit of Pulsed MIG welding in this application is the balance between providing sufficient energy to ensure good fusion yet controlling heat input to prevent warping or burn-through. With Pulsed MIG machines, the welder rapidly and automatically switches between a high peak current (ensuring good fusion) and a low background current (lowers heat input and reduces distortion). On thin material, that’s important.
“With Pulsed MIG programs, we can run higher wire speeds, and because of the better arc control, we can run faster, flatten out our welds, get better control of our weld metal volume and eliminate overheating issues,” says Dan Apfelbeck, continuous improvement leader–fans and vents, Greenheck.
“The adaptive Pulsed MIG programs make operations easier,” adds Grabko. “Operators get a consistent arc because the equipment reacts to changes in the arc at higher processing speeds.”
The Invision 352 MPa features built-in Pulsed MIG programs for common 4000 and 5000 series aluminum wires ranging in diameter from .035 to 1/16 inch, as well as many of the other alloys found in Greenheck’s products (steel, stainless steel, silicon bronze, copper, nickel). Operators previously had to set their parameters independently — 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,” says 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 has played a key role in allowing operators to transition from a steel to an aluminum operator.”
One specific application at Greenheck where this is evident is in the fabrication of its model SWB (single wide blower) centrifugal fan. The wheel contained inside is constructed of 1100 and 3003 aluminum, and welded with MAXAL’s 4043 aluminum wire. The structure itself features aluminum components no more than .060 and .080 inches thick. As a rotating fan with plunging angles and narrow spaces between each blade, it proves difficult to achieve the proper gun angle and not blow through the back of the material.
“Due to the Pulsed MIG procedures and the ability to minimize heat input, burn-through and blistering, and to control the weld metal volume, just about anyone can do it now,” says Apfelbeck.
This is important for a company like Greenheck which runs three shifts and requires its welders to be proficient at numerous products.
“Welders with a lot of buttons tend to complicate things from one shift to another, creating issues between operators,” he says. “One operator may like to run it one way and another operator run it a different way. Previously, I was constantly out on the floor helping people adjust the more complicated machines. The Invision 352 MPa has a single knob control. You grab the gun and pull the trigger, set it to whichever material you are welding, and all you have to do is turn the wire feed speed up or down. No more inter-shift conflicts with the operators.”
One-Knob Synergic Controls Saves Time
Ninety percent of the louvers manufactured by Greenheck are built from 6061 aluminum and welded with a 4043 MAXAL filler wire. They are also built from stainless or mild steel, depending on what the customer wants. The largest louvers get up to 10 feet long and 8 feet wide. When spliced together, they may cover the entire side of a building. Constructed of varying material thicknesses and joint configurations, this creates a consistent need to adjust wire feed speed and Pulsed MIG settings (pulses per second) to prevent burn-through and distortion. In the past, this required the welder to stop between each varying joint, go back to the machine, and make adjustments.
With the Synergic Controls featured on this new Pulsed MIG technology, welders are able to adjust wire feed speed via a knob on the MIG gun (it’s important to note that wire feed speed controls amperage). Based on these adjustments, the machine also automatically adjusts the pulsing parameters. The result is an arc perfectly tailored to the thickness and joint type without the operator having to make trips back to the machine.
“You used to have to adjust for every change of wire speed,” says Grabko. “Now, with this one-knob control, you don’t have to do that. Depending on the unit and the configuration, this saves operators 5 percent in time based on the time it takes to go back and forth between the unit.”
Greenheck has also optimized some of its units in extended reach applications with XR-AlumaPro™ Plus push-pull guns. The consistent feeding of a push-pull gun, even with relatively soft aluminum wires, helps ensure the operator is only putting as much heat and metal into a joint as is desired. The MAXAL wire is also specifically formulated to provide excellent soft-start characteristics and minimal burnback. Manual applications achieve a greater weld bead quality with minimal oscillation.
MAXAL wire also features superior feedability with reduced bird-nesting, extended liner and consumable life, and excellent x-ray quality. The combination of machine, wire and gun truly optimizes wire feeding.
“If a wire feed slows down or has too much voltage, it can blow through the aluminum,” says Grabko. “When we are welding fan blades that are .060-inch thick, if there is any hesitation in the feed, it will burn a hole. Depending on the fan unit, we may have to throw out the entire thing because of a hole. With the new Pulsed MIG systems, we have reduced reject work by 10 percent.”
Benefits of Transitioning to Larger Diameter Wires
Working with Pulsed MIG equipment has allowed Greenheck to eliminate its reliance on .035 inch wire in certain applications and transition to 3/64-inch (.047 inch) aluminum wire.
“With the new Pulsed MIG programs, it has allowed us to go to one wire diameter: 3/64-inch,” says Apfelbeck. “This is because we can weld down to .050-inch material with heavier wire and still eliminate burn-through and blistering. The larger wire diameter allows for faster travel speeds, increases fill rate (deposition) and is a lower cost per pound.”
It has also allowed the company 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 the ability to use the larger diameter wire,” he adds. “Our equipment outlay is much less. Maintenance and consumable costs have been reduced.”
Improved Starts and Stops
One of the greatest challenges with welding thin aluminum occurs at the very beginning and very end of a weld. With conventional MIG technology it is more difficult to put in the right amount of heat at the beginning of the weld without blowing through the thin material. Likewise, it’s difficult to achieve the proper crater fill at the end of the weld with the older machines. New Pulsed MIG technology provides superior arc starts by automatically providing more energy at the start of the weld, which helps ensure good fusion and then reduces energy to normal parameters for optimal welding characteristics. The agitation in the weld puddle created by Pulsed MIG also helps “clean” the layer of oxide typically found on aluminum.
“Aluminum has an oxide on it,” explains Tucker. “The cleaning action with these Pulsed MIG programs helps with the oxide and it makes it easier to weld.”
The same goes for the end of the weld: Today’s Pulsed MIG technology ramps down to a cooler welding parameter to fill in the crater, as well as tailors the amount of ramping to compensate for the heat dissipation characteristics of aluminum.
“Crater filling is a challenge,” he adds. “These new machines help with options that automatically crater-fill at the end of the weld.”
Appearance of the Weld, Increased Productivity
The aesthetics of the weld bead are critical in Greenheck’s aluminum welding applications. Customers like to see flat welds. Some customers request the “stacked dime” appearance that was once done either with the TIG process or with technique and timing by a seasoned MIG welder. The Profile Pulse™ feature on the Invision 352 MPa allows any operator to achieve that aesthetic appearance with minimal time and training. Profile Pulse allows the operator to adjust the pulse frequency to increase or decrease the space between the ripple patterns to achieve the desired weld appearance. Compared to TIG and conventional MIG, Pulsed MIG is able to accomplish this with higher travel speeds and lower heat input.
“Pulsed MIG has higher travel speeds — as much as 50 to 60 inches per minute — compared to TIG welding at 8 to 10 inches per minute,” says Wirtz. “It’s good for productivity as well as quality. Lower heat input maintains the strength in the base metal.”
The Invision 352 MPa’s Pulsed MIG programs have also eliminated spatter on structural steel for Greenheck operators. This eliminates unproductive time related to weld cleanup. Operators increase productivity by 10 to 15 percent by eliminating the time spent cleaning up spatter.
“We don’t want to pay our welders to do cleanup when they should be welding,” says Grabko. “Structural steel tends to have more spatter, so the Pulsed MIG machine helps a lot in that area.”
Training Made Easy
Due to the reduction in highly skilled workers in the industry, Greenheck focuses on equipment that is user-friendly for newer welding operators, but still delivers the quality weld that customers demand.
“The new equipment has helped a lot with operator training,” Wirtz says. “We can stay on the leading edge of technology — having a machine that is simple to use, yet it gets the job done. It’s easier for the guys on the floor. There aren’t as many controls to worry about. They can adjust hot starts and crater fills right on the machine instead of manually doing them. When you are doing a consistent product in one area, you can set that machine and be up and running faster, and with more consistent results.”
“You can take an operator that has worked 30 years and a brand-new operator and put them on one of those machines and we don’t have any issue with weld quality,” says Apfelbeck.
Partners in Quality
Quality workmanship has been the cornerstone of Greenheck’s success. The company cares about its employees, so they, in turn, strive to make better quality products that leave the competition scrambling to catch up. Greenheck expects the same from its partners, which is why it works with Miller and other ITW Welding companies such as MAXAL. For Greenheck, customer service is important. With over $400 million in sales each year, if there are equipment problems, it can impact the bottom line.
“When you have a company that doesn’t give you the customer service you need, helping to solve issues on a day-to-day basis, it really creates problems in your product flow,” Apfelbeck says. “With Miller and the ITW Welding companies we work with, when we have an issue, we get solutions very quickly. Response time is same-day. We’ve found that Miller’s customer service is unmatched in the industry and we’ve chosen to become a “blue” shop because of that. We rank customer service at the top of our list for vendors.”