Additive manufacturing, also referred to as 3-D printing or AM, is one of the fastest growing technology sectors today. Understanding the growing need for support in the rising use of AM, Lincoln Electric is entering the next chapter with an AM business for large metal parts. This is a new and different business model for Lincoln, where the company is making parts for customers instead of providing the equipment, consumables or automation.
Lincoln Electric Additive Solutions metal additive manufacturing service launched in mid-2019, providing large-scale metal printing of industrial parts, tooling and prototypes for general industrial, aerospace, heavy equipment and automotive customers. This AM platform helps customers improve lead times, designs and quality in their operations. To carry out these services to customers, Lincoln invested in a separate building that will have more than 20 robotic cells for AM by early 2020.
Lincoln was able to develop its unique AM process by digging into its deep knowledge of welding technology, robotics and motion control software to build up parts in a fraction of the time compared to traditional manufacturing methods.
“We’ve developed everything necessary in-house – the equipment, the software behind everything and the process control,” says Mark Douglass, business development manager for the new service. “It is based on our extensive capabilities in robotics and integration, plus we have welding knowledge in fume control, wire, power supplies and torches. All of that gives us a unique capability in the industry. We are vertically integrated, which sets us apart from the vast majority of competition.
“What is also unique is our focus on large parts,” he continues. “Parts measured in feet and meters are what we’re targeting. Currently, the vast majority of metal AM is focused on smaller parts using powder, but our wire-based technology is very suitable to large parts.”
Support not needed
Still a printing process where metal parts are built up layer by layer, the Lincoln process is an all-robotic system that uses wire arc or laser hot-wire additive to build up parts on a positioner that can hold up to 1,500 kg of material – with plans to scale the positioners to larger sizes.
The wire used in the process itself can be a variety of materials, depending on the application. Lincoln is currently using low-alloy steels; stainless steels, including 300 series and 410 stainless steels; nickel-based alloys and Invar.
With large-scale wire-based metal AM, the part is manipulated during the metal deposition. One of the most significant benefits of Lincoln’s process is the ability to manage coordinated motion between the robot and the positioner to produce complex shapes without needing a support structure.
Support structures are a significant cost that are often built into AM parts with complex shapes. They are needed if the part has overhang features, for example, otherwise gravity will cause the molten metal to drip, at best, or fall away completely, at worst.
“Many AM processes can only print vertically with all the layers in the same plane,” Douglass says. “If a job requires something that hangs out at 90 degrees, like a shelf, for example, they often layer additional material underneath the shelf to support it while it’s being built. But that requires more print time and more material, which eventually has to be removed, so that adds more costs, as well.
“We can print parts near net without the support structures,” he adds. “With our ability in the CAD world to figure out how to make the part and then execute it with a robot and positioner, we can continuously move the part so we don’t get drips, material falling out and other issues. In our process, we have a separate positioner that presents the part to the robot to be able to lay in the metal without a support structure. We have the ability to control the motion of the positioner and the robot and, therefore, change the angle of the presentation to the torch or laser head.”
To achieve the complex path planning and coordinated motion between the robot and positioner, advanced software is critical. “The ability to move a part while the robot is also moving isn’t easy to do,” Douglass says. “In standard automation, you may have a positioner with coordinated motion between the positioner and the robot, but this is another level beyond that and we use our proprietary CAD to Path Planning software to get us there.”
The software provides Lincoln the ability to analyze the part design in “slices” to develop a robotic path plan. This, in turn, optimizes printing to attain the best quality and minimize production time.
“Additive manufacturing is building layer by layer, but when we slice it, we also have to determine how to actually lay down the material,” Douglass explains. “For example, we could use a zigzag pattern or a circular pattern. Understandably, there are different ways to do it based on the shape of the part.
“We’re very good at executing the path planning while also monitoring what is happening in the middle of the deposition so that we’re not deviating from the plan,” he continues. “In manufacturing, it is common for the process to get out of control. But, fortunately, we have controls in place to compensate for that and eliminate deviations.”
Making parts
Initially, tooling for the aerospace and automotive industries is an area of focus for Lincoln. This includes the aerospace molds and fixtures used to make composite parts. The molds are often made from Invar, a low-metal expansion alloy. In addition to the molds, fixtures and other tooling are required as the composite parts are cut to size and put together.
“There is a broad world of tooling in aerospace that our technology fits,” Douglass says. “Traditionally, a significant amount of fabrication, such as bending, forming and machining, is required to make a mold. On top of that, sometimes the raw material, typically Invar plate, isn’t always in stock, which can add significant delays to the delivery of the mold. Our raw material, on the other hand, is wire that we can control because we manufacture it.
“Oftentimes, it takes three to five weeks to manufacture the mold – even longer for very large and complex tools – plus any additional time spent waiting on the raw material,” he continues. “In the studies we’ve performed and for parts we’ve made so far, we’re printing them in less than two weeks.”
In automotive, the Lincoln process is well suited for a variety of large-scale parts, including stamping dies and various molds. For dies, a good application for AM in general is producing conformal cooling channels within the die, which are typically created through drilling. Because drilling is linear, it limits the ability to cool the parts and extract the heat out of the die. AM, however, allows the flexibility to shape the channels in different ways to cool the part faster, increasing productivity and reducing cycle times.
In addition, Lincoln sees significant opportunity in using large-format metal AM to replace steel castings in heavy equipment and other industries. Low volume production or prototype castings can easily take six months or significantly longer to procure, and often are of poor quality requiring significant amounts of welding repair once received. Lincoln can manufacture parts with mechanical properties and quality that rival and even improve upon castings.
Overall, large-scale industrial parts are a broad market for Lincoln’s services. The company bases the expertise and ability it has today as significant reasons for pursuing the services strategy to provide parts rather than selling the equipment. Lincoln also recognizes the barriers that many customers might have in carrying out AM in-house.
“Our equipment would require an expensive capital investment and then the end user has to find at least two or three people to operate the equipment, understand how to use it and develop their own processes,” Douglass says. “It would be a significant risk to put down a large investment and not know what the overall end result will be. We have one of the best processes in the world and we can do large-scale, complex shapes in a quality way.”
