New Pulsed MIG Technology Fans Greenheck’s Productivity
How does a company grow from a small, two-person operation to one of the largest of its kind? Part of the answer comes with being able to find and maintain a trained workforce that is able to maintain high quality standards during expansion.
Greenheck, one of the nation’s largest ventilation product manufacturers, solved the welder shortage problem by instituting its own weld training program. Regardless of prior training, every welder in the company has gone through the program and has been trained to maintain the company’s high standards. As long as the desire to become a welder exists within the workforce or the surrounding community, Greenheck won’t run short.
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| By switching to the Millermatic 350P on its aluminum louver line, Greenheck saved 10 percent on rework and 25 percenton filler metal. |
But just as important is remaining current with evolving technology. A reliance on older or less-than-optimal equipment may lead to a company not fully realizing its profit potential. Greenheck discovered this when, while adding equipment to increase capacity, they found that new developments in pulsed MIG technology, specifically Miller Electric’s Millermatic® 350P pulsed MIG welder, saved them time and money.
Recently, Greenheck needed to add more equipment to its aluminum louver line to keep up with expansion. But rather than simply adding more of the same welding equipment, Josh Holtz, senior manufacturing engineer, asked if today’s technology held any additional benefits.
It was a good question and brought some unexpected rewards. It led to the purchase of 12 Millermatic 350Ps with a new pulsed MIG program. Purchased to increase capacity, they brought some added benefits: Not only were they $2,500 less expensive per unit than the welders currently being used and easier to operate, Greenheck saved 10 percent in rework time and lowered filler metal use on its aluminum louver product line by 25%.
Greenheck
It’s been almost 60 years since Bernie and Bob Greenheck first opened the doors to a tiny sheet metal shop in Schofield, Wisconsin. Today, the company that bears their name has grown to be a leading manufacturer of commercial and institutional ventilation equipment, with sales in excess of $350 million per year.
With over 2,000 employees and more than 1.4 million square feet of manufacturing and office space worldwide, Greenheck offers what may be the most comprehensive line of ventilation products available - fans and ventilators, centrifugal and vane axial fans, kitchen ventilation systems, dampers, louvers, make-up air units, and energy recovery ventilators, and laboratory exhaust systems - allowing a complete air movement and control system to be specified from a single source. Its air movement and control equipment is used in commercial, institutional, and industrial buildings.
Greenheck now has facilities in several states and China and continues to grow. In one five-year period, it increased its manufacturing space by an average of more than 65,000 square feet per year.
Company-wide, 180 welding operators work to maintain Greenheck’s high standards and quick turnaround times. Products that are not in stock can be built to customer specifications in 1-day, 3-day, 5-day and 10-day cycles. Regardless of prior welding experience, each welding operator has gone through Greenheck’s welding training program; the best of them are asked to teach others.
Welding Louvers
The louvers use aluminum alloys 5052 (magnesium alloy) and 6063 (magnesium-silicon alloy), ranging in thickness from .080 in. to 750 in., the majority being .080-in-.125-in. 6xxx series. Because the products are highly visible, the welds— T-, edge, butt and lap joints— need to be strong and cosmetically appealing. Previously, Greenheck used other inverter based welding sources with pulsed MIG capabilities. Although the other welders performed well, the Millermatic 350P with its improved technology was even better suited to the thin materials used on the line.
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A sampling of Greenheck’s aluminum louver line. The welds need to be cosmetically appealing on the highly visible products. The Millermatic 350P makes that easier.(Photo courtesy Greenheck Fan Co.)
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“Our experience with the older technology welders told us that they’re geared to run thicker materials,” Holtz explained. “They weld very well on thicker aluminum, such as 3/16-in. to ¼-in material. But we always had problems once we got to the hundred-thousandths and thinner. Most of the welds on the louver line need to be just 1/8-in. wide. That was very tough to achieve. Instead, we were welding 3/16-in. fillets. Sometimes they could even get larger due to the joint style and welding position. That was not only wasted metal, but with an increased weld size there’s more chance of burn-through or blistering.”
Aluminum presents some unique welding challenges. It conducts heat about six times faster than steel, requiring higher amperages and faster wire feed speeds. Second, aluminum has a relatively low melting point (1,220 degrees F). These two factors make it susceptible to burn-through, especially with thinner material.
If a weld does require rework, the welding operator is responsible for resolving the problem and ensuring that the weld meets Greenheck’s strict workmanship standards. This may involve wire brushing, crater fill-in or resolving burn-through issues—all of which takes time away from welding.
This extra time, as well as the extra filler metal used from making larger-than-necessary welds, added costs to the product—costs that had become an accepted part of the process. But when Greenheck had to add more welders to increase capacity, they found that recent technology developments allowed them to cut these hidden costs.
“We wanted to add the best machine we could find,” Holtz said. “As a rule, when purchasing welding equipment, we look at three main factors: performance, cost and reliability. In this case, we were looking for a welding system that could weld thin aluminum effectively, yield welds that were cosmetically appealing and was dependable and very versatile. We asked Miller if they had newer technology that would better fit the product line.”
Miller brought a Millermatic 350P for them to try. “We compared it to the other units on light aluminum,” Holtz recalled. “It offered much better performance on the material thickness we run. Its revised pulse program allowed us to weld thin aluminum more effectively. Its arc control characteristics make it very user friendly and flexible.”
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Pulsed MIG
The Millermatic 350P’s pulsed spray transfer capabilities make it ideal for thin-gauge aluminum needs. Pulsed spray transfer, commonly called pulsed MIG or GMAW-P, puts less heat into the work yet maintains many benefits of spray transfer, such as good fusion, high deposition rates and/or fast travel speeds.
In pulsed spray transfer, the power source switches between a high peak current and a low background current. The peak current pinches off a spray transfer droplet and propels it toward the weldment. The background current maintains the arc, but is too low for metal transfer to occur. This is unlike spray transfer, which continuously transfers tiny drops of molten metal.
Good applications for pulsed MIG include those prone to such problems as lack of fusion, warpage, burn through, spatter, lack of puddle control and poor bead appearance. Short circuit transfer can be prone to poor fusion (especially at the toes of the weld) and porosity. Pulsed MIG can solve these problems because it lowers heat input to levels associated with short circuit transfer, yet maintains the good fusion of spray transfer.
Pulsed MIG provides good bead appearance because the tiny molten droplets being transferred do not create spatter. Also, because the weld puddle cools in-between pulses, it freezes faster. The puddle is less likely to sag or look excessively convex when welding out-of-position. Operators have so much control over the weld pool with pulsed MIG that they can create beads with a TIG-like appearance.
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Greenheck purchased 12 of the Millermatic 350Ps, moving the other power sources to other applications in the company where the material wasn’t as thin. About 40 operators, working in three shifts, now use the Millermatic 350Ps. With their purchase, the time spent on rework has dropped by 10% and filler metal use has dropped by 25%.
“We found that the 350P has a much more refined pulsed arc and we can control the amount of penetration and weld size,” said Holtz. “With the better arc control, we can keep the weld size small and the louvers are more cosmetically appealing. Now we can hit weld size where before we couldn’t.”
Miller recently updated the Millermatic 350P’s programming to provide exceptional performance in reducing weld spatter, increasing deposition rates and deposition efficiency and enhancing weld bead appearance. The new pulsed MIG technology it incorporates makes it especially suited for Greenheck’s aluminum louver line.
The Millermatic 350P can weld material from 22 gauge to ½ in. in a single pass. It can run on single- or three-phase input power and offers a duty-cycle rating of 60 percent at 300 amps/32 volts, a 25- to 400-amp output and line voltage compensation. There is no de-rating when run on single-phase power.
Holtz likes the welders’ all-in-one design, saying, “The Millermatic 350P puts a complete package into a very mobile unit. We don’t have to purchase a separate power source and feeder.”
The Millermatic 350P’s list price is $3980.00, an economical alternative to an industrial power source, pulsing controls and bench-top style wire feeder. Compared to the previous machine and push-pull wire feed system’s combined suggested price of $6,492. Greenheck saved 38% per machine by choosing the Millermatic 350P.
But that’s only part of the savings. For example, with a 10% reduction in rework, the company saves $4,160 per year.
Adding in the savings from a 25% reduction in filler metal more clearly shows the wisdom of the purchase. For instance, a 25% reduction in filler metal for a company using 1,000 pounds of .047-in 4043 filler wire per month at an average cost of $3.35 per pound would save $837 per month or $10,044 per year.
But one of the Millermatic 350P’s main benefits is its easily understood interface. To begin pulsed MIG with the Millermatic 350P, the operator simply selects the built-in program that matches the wire type and size, and the unit automatically sets the pulse parameters. Once the desired arc length is set, the operator only needs to adjust wire feed speed to weld a different thickness of metal.
With the Millermatic 350P’s ease of use, operator-friendly interface and pulsed MIG programming even novice operators are able to quickly make quality welds on aluminum— welds that rival TIG welds in appearance. This is an important consideration for Greenheck, which trains all of its welders, many of whom have never welded before participating in the program.
The Training Program
The welding training program ensures that Greenheck can find enough welders who can maintain its high standards. Finding qualified welders is a common issue. Greenheck makes its own.
“We had a hard time finding welders,” Holtz said. “We wanted a way to make more welders when we needed them, so we started our own internal training program. We hire people who will be good employees for us, or take some of our existing good employees who are interested in becoming welders, and we train them to weld. If they already know how to weld, that’s a positive. But regardless of welding experience, all welders go through the training program and learn what they need to know to weld at Greenheck.”
The instructors are specially designated employees who pass their knowledge on. “They’re continuous improvement leaders, dedicated to the welding operation, who conduct all the internal training,” Holtz said.
Under their guidance, welder-trainees learn the seven welding variables— amperage, voltage, contact-tip-to-work distance, travel angle, transverse angle, travel speed and wire p
osition—plus welding procedures, base metals and joint positions.
“It’s a fully comprehensive course on welding at Greenheck,” Holtz said. “Then our continuous improvement leaders follow them to the floor and work with them one-on-one. Usually within two or three weeks, they’re up to speed and can work on their own and be productive.”
With each weld, operators must meet Greenheck’s internal welding procedure specifications, which were created to ensure quality is maintained as the number of products and those producing them grow. There is a welding procedure specification for every material thickness, joint style and filler metal.
Now, with the Millermatic 350Ps onboard, meeting those specifications has become easier and more efficient than before. It’s just part of Greenheck’s ongoing commitment to quality and its customers.
“We try to be the easiest company to do business with and to make a quality product,” Holtz said. “Those are the things that allow us to grow like we have.”