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Wire Arc Additive Technology Provides Fast, High-Quality Option for Making Large Parts

Category: Manufacturing Technology Mar 3, 2021


By Stephen LaMarca, Manufacturing Technology Analyst at AMT - The Association For Manufacturing Technology

It’s a beehive of activity at the Lincoln Electric Additive Solutions facility in Cleveland, Ohio, where 18 buzzing welding robots are busily 3D printing large metal parts. These systems are using wire arc additive technology, which, after years in development, is now ready to revolutionize large-scale metal manufacturing.

3D printing has been effective for small metal parts up to this point, but wire arc additive manufacturing is now a viable option for making large parts (bigger than a basketball) that have been traditionally casted or forged, as well as one-offs such as tooling, prototypes, and legacy parts.

Wire arc additive manufacturing combines metal inert gas (MIG) welding with CAD software to deposit layers of melted wire onto a positional turntable. With its robot arm, welding torch, and multi-axis table, the system may resemble a modified version of MIG welding, but it’s more complex than that.

Lincoln Electric has made a significant investment in developing this technology, recognizing that it’s a key growth area for the company and the manufacturing industry as a whole.

Solving Industry Challenges
The on-demand nature of wire arc additive manufacturing is ideal for heavy industrial equipment manufacturers in mining, construction, agriculture, and energy industries. These companies regularly face production delays, downtime and increased costs because of failing machine parts that are hard to replace, high shipping costs, long lead times for castings and forgings, and product testing/regulations that require redesigns. The ability to 3D print individual large parts eliminates these problems.

Depending on its size and complexity, a large-scale part may take only hours or days to manufacturer via the wire arc additive method. Compare that to parts that may take weeks or months to arrive from a casting provider.

“Castings have long lead times and often significant quality issues in porosity and dimensional accuracy,” said Mark Douglass, PhD, business development manager for Lincoln Electric Additive Solutions. “OEMs can't update their designs very often because the molds are expensive and take a long time to redesign.”

Expanding Expertise
Lincoln Electric’s Additive Solutions business unit and its 75,000-square foot facility are the culmination of  125 years of welding heritage supplemented by acquisitions and partnerships over the last decade to refine wire arc additive manufacturing to where it is today.  These relationships provide knowledge and capabilities throughout the additive value chain—from the power sources and wire feedstock to the software and machining.

Prototype alternator housing—working with internal LECO product team on new engine driven welder.

Using its deep welding experience, Lincoln Electric started looking into depositing metal using robots in the 1990s. By the late 2000s, Lincoln Electric had patented the laser hot wire process and was testing different wire materials for a method of cladding. In the last decade, Lincoln Electric expanded its in-house knowledge of robotics by acquiring automation companies such as Wolf Robotics, added in 2015.

In 2016, Lincoln Electric started a technical collaboration with the US Department of Energy’s  Manufacturing Development Facility at Oak Ridge National Laboratory (MDF at ORNL) to advance the development of large-scale metal additive technology. The goal was to use data analytics to increase throughput, improve quality and lower the cost of large-scale additively manufactured industrial metallic structures like parts and tooling.

“Working with Oak Ridge gave us a better understanding of the process and materials involved, but in particular the control of the process and the modeling,” Douglass said. “From a commercial standpoint, they bring a lot of eyeballs and get a lot of attention. It's the center of 3D printing R&D in the U.S. They have a lot of know-how to get attention in the industry, which is valuable as well.”

ORNL’s critical analysis indicated that wire alloys would speed up the printing process and reduce shipping costs compared to a traditional metal powder bed system.

“If industry is going to adopt a new technology, it has to be transformative, so we are looking at methods to change the way industry does traditional manufacturing,” said Lonnie J. Love, Ph.D., Corporate Fellow, Precision Manufacturing and Machining, Oak Ridge National Laboratory. “We’re built to help drive forward innovations very quickly.”

Lincoln Electric recently printed tooling for a hydropower gen manufacturer for its welding process. They needed a really complex shape that provided gas backing for long, deep penetration welds. After having a hard time finding a fabricator or a machine shop that would make it for them, the manufacturer gave the file to Lincoln Electric and they were printing the next day. Parts arrived that same week.

However, Lincoln Electric needed to broaden its expertise in machining custom, built-to-order parts before it could offer a truly seamless manufacturing service.

“We realized when we were putting together the strategy for Additive Solutions to provide a one-stop shop, we needed a machine shop to talk with the additive team to have a smooth hand-off throughout the entire process,” Douglass said.

To gain that CNC machining knowledge, in 2019, Lincoln Electric acquired Baker Industries, a provider of custom tooling, parts, and fixtures with extensive in-house design and manufacturing capabilities, including machining and fabricating for the automotive and aerospace industries.

The combined expert team proved a “digital foundry” concept in which Additive Solutions and Baker work hand-in-hand to design with both additive and machining in mind to improve production efficiencies, reducing overall production time and costs. So far, Lincoln Electric  has 3D printed mild and high-strength steels, stainless steels, Invar, nickel, aluminum, and bronze alloys.

Production Invar tooling—lay-up mold for manufacturing carbon fiber composite aerospace parts.

Quality is Job One
Although speed is an important aspect of producing parts, quality is the top priority. By properly modeling the process in its proprietary slicing and path planning software, SculptPrint™ OS, and executing the print with a stable process, Lincoln Electric can prevent voids between layers and ensure parts are printed right the first time. That level of quality and accuracy is critical for OEMs, especially when running a stainless steel, nickel, or other expensive alloy.

“We're still certainly much faster than other processes, but we're not going to talk about doubling deposition rates until we know that we have achieved a high level of quality,” Douglass said. “We're focused on getting the quality of parts first, and then we can speed it up later.”

Prototype valve housing for Oil & Gas—printed in less than two days vs. typical 6-month lead time for casting.

Today, Lincoln Electric works with companies to print prototypes or production parts based on client-provided models and files. Then the discussion turns to the applications and challenges, which inform the recommended wire alloy.

“We don’t necessarily need to print with the same material as the sample part,” Douglass said. “ORNL’s research has shown that we can print a part in which the inside is a tough but inexpensive material like steel, but then the outer shell is hard martensitic stainless steel. We help customers think through ideas for materials as well as the design.”

The Future is Tooling
An especially promising growth area for wire arc additive manufacturing is in tooling. Baker Industries’ reach into the aerospace market has given Lincoln Electric access to aerospace customers where molds for producing carbon fiber composites are often especially complex. Using a billet or several welded plates to make a mold can be very time consuming and expensive.

“There are three killer applications for additive: tooling, tooling, and tooling,” Love said. “Because you only need one, it's of high value, and it has a long lead time. Lincoln can near net print molds in Invar and steel in the span of a week that would have otherwise taken months. Additive technology can really transform the tooling industry and bring more work back to the U.S.”

FutureView 
For more about Oak Ridge National Lab projects and other labratories' work, check out IMTS Network's series, FutureView:

The Manufacturing Demonstration Facility (MDF) at Oak Ridge National Laboratory, established in 2012, is one of the Department of Energy’s designated user facilities focused on performing early-stage research and development to improve the energy and material efficiency, productivity, and competitiveness of American manufacturers. Research focuses on manufacturing analysis and simulation, composites and polymer systems, metal powder systems, metrology and characterization, machine tooling, large-scale metal systems, and robotics and automation.

The MDF is a 110,000 sq. ft. facility housing integrated capabilities that drive the development of new materials, software, and systems for advanced manufacturing. From binder jetting to 3D tomography to in situ monitoring, the MDF leverages a range of equipment and expertise focused on reducing the carbon footprint of the manufacturing sector, efficiently utilizing abundant and available domestic energy resources, and supporting the production of clean energy products that boost the nation’s economy.

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