Engine-driven welders are versatile tools with enough diversity in size and capability to match most any application. With horsepower ratings from approximately 10 to 70 and fuel choices including gasoline, diesel and LPG, these machines vary in welding power from 50 to 800 amps and are capable of processes ranging from SMAW (stick) in smaller models—to stick, TIG, MIG, flux-cored and arc gouging in multipurpose models—to models that further add advanced processes, such as pulsed MIG. Most also produce auxiliary electrical power for job-site tools and lights, some add an air compressor for pneumatic tools and one-machine gouging, and a few even provide auxiliary hydraulic power.
Although manufacturers have continually refined the design of these machines, a combination of market forces is today prompting significant changes in engine-driven units: among them are emissions control, user concerns about productivity and operating costs, and the need to adapt equipment to better serve a changing work force.
Emissions-control implications
The complexity of designing these machines for emissions compliance varies, of course, with horsepower ratings and fuel source. For example, Vanair’s Air N Arc models—most of which use engines with 25 horsepower or less—were developed from the start in the early 2000s with an eye towards compliance, says the company’s Donnie Stone.
“We developed these units looking long term,” says Stone, “so there was never any interim period where we were forced to come to a quick solution about emissions technology and packaging.”
But for manufacturers of higher-horsepower machines, the road to emissions compliance has been somewhat steeper. According to Ben Froland, product manager, industrial engine drives, Miller Electric, accommodating Tier 4-Final technology into diesel-engine-driven models, especially those with more than 25 horsepower, has been a technical challenge that has increased prices.
“Buyers are thinking more carefully about purchases these days,” says Froland, “asking whether they can shift to smaller units or to those more versatile in order to trim the number of machines required. That said, buyers still must remain mindful of possible future requirements when choosing equipment.”
“Once you get into an engine-drive with more than 25 horsepower, prices are definitely higher,” says John Wasko, Lincoln Electric’s product manager for engine-driven welders. “Customers typically welding 90 percent of the time between 200 and 300 amps might not need a 400- or 500-amp machine any more—as long as they understand the smaller machine’s capabilities and possible limitations. At the same time, buyers want to think about the future and make sure they buy a machine that will get them there.”
More than Tier 4
Increased costs for higher-horsepower Tier 4-compliant machines, coupled with the end user’s concern about reducing operating costs, has manufacturers of engine-driven units focusing on value-added designs.
Vanair, for example, has added auxiliary-hydraulic capability to two of its 300-amp Air N Arc models, which already combine a welding unit, generator, air compressor and battery boosting/charging system into a single package. A 10.5-gpm, variable-displacement pump draws fluid from the service truck’s reservoir for one model and from an integral reservoir on the other. According to Vanair’s Stone, the hydraulic flow can power a service truck’s crane or run hydraulic tools, thus relieving the truck’s engine and PTO from powering these functions.
Emissions compliance, however, remains a primary driver of value-added designs:
“Given the expense of Tier 4-Final,” says Lee Seufer, business unit manager, engine-drive welders for Lincoln, “we made a conscious decision to give customers more than just a clean-burning engine that runs smoother and starts better in cold weather. We’ve also boosted the overall performance of these units and made them more bullet-proof in nasty weather with such features as encapsulated printed circuits boards and sealed switches.”
Lincoln’s Wasko points to what he terms the value-added design of the company’s new Dual Vantage 700-I model, a 69-horsepower, multi-process, 700-amp welder/generator that allows two operators to share the welding power. In addition, the machine can accommodate inverters to add more operators.
“Whether stick or wire-welding,” says Wasko, “construction welders rarely use more than 300 amps. If you have two operators on the same machine, you can increase production with a lower capital investment and also have only one engine to service. We are seeing an increasing need for users to get more than one arc off an engine-drive, and we’ll likely expand on that concept in the future.”
Wasko also calls attention to Lincoln’s new engine-driven “3-in-1” Air Vantage models, the 64-horsepower 600SD and 69-horsepower 650, which combine in one unit a multi-process welder, generator and rotary-screw air compressor that provides 60 cfm at 100 psi for heavy-duty carbon-arc gouging and pneumatic tools.
Miller’s Froland says that the value-added aspects of the company’s Tier 4 models includes incorporating a “secondary switcher” design that results in generally lighter, more efficient machines with greater output, expanded duty cycles, and increased arc control.
Froland also cites the value-added features of Miller’s recently introduced dual-operator Big Blue 800 Series—including the 800 Duo Pro, Duo Pro SF and 800 Duo Air Pak. Each of these welder/generator, multi-process models, he says, can deliver two premium arcs, up to 400 amps each, and can accept added inverters to allow up to six operators to work off a single machine, without arc interaction, while using different processes and settings.
The 800 Duo Air Pak uses a screw-type air compressor (60 cfm/100 psi) that is ideal for gouging and running pneumatic tools, says Froland, and the 800 Duo Pro SF is capable of running the pulsed MIG process, as well as Miller’s RMD (Regulated Metal Deposition) process.
Advanced processes
Miller’s RMD process, says Joe Ryan, marketing segment manager for the company’s pipe-welding products, is designed for process pipe welding and was developed to replace TIG welding in “open-root” applications. Ryan explains that in the RMD process, arc voltage and current diminish as the wire approaches the work, providing a “stable, calm metal transfer between the filler metal and the weld pool” that promotes faster welding speeds and thicker welds.
“The RMD process gets more work done faster with high quality,” says Ryan. “Used in conjunction with the pulsed MIG process, RMD offers the prospect of a ‘one-wire solution’ from root to cap.”
Another advance for engine-driven welder/generators, typically in higher-amperage machines, is the capability to handle the pulsed MIG process, which, says Lincoln’s Seufer, has been typically a shop-only process.
“Pulsed MIG gives greater control over arc behavior,” says Seufer. “The process uses a peak current and a background current that pulse rapidly up and down, allowing closer control of the heat going into the weld and reducing spatter and fumes.”
Lincoln’s Wasko adds that the pulsed MIG process can simplify certain difficult welds: “If you’re welding difficult material or a difficult joint configuration, pulse and other advanced-system capabilities allow handling those situations more easily than in the past.”
Advanced wire feeders
Although using a wire feeder with an engine-driven unit is not new, more advanced feeders used in the field provide added control at the weld site.
“With a cable 100 or 200 feet long,” says Wasko, “the welder and the wire feeder can be some distance from the engine-drive. With advances in wire feeders, the control interface at the feeder allows the operator to set wire-feed speed and voltage, for example, without running back to the power unit.”
Seufer adds that advanced wire feeders also simplify the adjustments required at the feeder: “We’ve added the capacity for the wire feeder to be programmed with settings for a number of different processes, and operators can very easily recall them by just pushing a button. Programs can include those for stainless and aluminum to further expand capabilities.”
According to Miller’s Froland, refinements in wire feeders help expand the use of advanced processes, such as pulsed MIG and the company’s RMD process.
“Usually these advanced processes are only available in the shop, because they generally require a special control cable,” says Froland. “But the new feeder now allows those processes to be done in the field by communicating on the standard weld cables. Before, you’d either have to walk back to the power source to make adjustments or string a remote cable to the feeder if you wanted control at the weld joint.”
Vanair’s Stone makes the point that all Air N Arc constant-voltage-mode models will operate any voltage-sensing, suitcase-type wire feeder on the market, a design, he says, that saves customers with existing equipment from having to purchase even more equipment.
Miller’s Ryan notes another factor in the industry that is having an effect on the design of welding units generally, including engine-driven models:
“The construction market’s labor force is aging and many are retiring,” says Ryan. “This is affecting the welding industry at all levels—not just welders, but also metallurgists and welding engineers. As a manufacturer, one way we’re addressing the issue is by reducing machine complexity—reducing the number of adjustments that less-experienced welders are required to make at the machine interface.”
In this regard, says Ryan, Miller analyzed which controls were infrequently used and removed them from the front panel. In other instances, controls were re-identified for clarity, for example, changing from the somewhat vague label “trim” to “arc length,” which operators intuitively understand, he says, as a way to fine-tune the arc without adding wire feed. Other small but helpful changes, says Ryan, include enlarging buttons that are easily pushed by gloved hands and making cables easier to connect to ensure correct polarity.
“The other issue to address is productivity,” says Ryan, “how do you make experienced welders more productive? We do that by introducing advanced processes, like RMD and pulse, which are both wire-welding processes. Typical travel speed for TIG welding, for example, might be 4 inches per minute, but with a wire process, it’s up around 12 to 14 inches.”
