Robots and Laser Welding, the Perfect Fit
From those early days when Unimate first reached across the assembly line, robotic welding has flourished to become a permanent resident on the plant floor. Now, with the advent of high-power laser technologies at lower ownership costs, robotic laser welding is bringing more flexibility and productivity to the workspace.
Robotic laser cladding (Courtesy of F.W. Gartner Thermal Spraying)An often unsung hero, robotic laser cladding, is saving parts from the industrial salvage yard and fortifying new components. Its applications are remarkable in size and scope. Meanwhile, hybrid laser arc welding is making inroads with the promise of higher deposition rates. A dip into the pool of emerging technologies reveals remote laser welding, hot-wire laser cladding and laser additive manufacturing.
“The newer technologies will generally give you higher productivity than what you will get with traditional welding processes,” says Michael Flagg, Manager, Application Engineering for The Lincoln Electric Company in Cleveland, Ohio. “They allow you to weld on materials that in the past may not have been weldable, such as exotic metals or metals prone to cracking that require less heat input and more control. They also give you more freedom and flexibility in the products you’re manufacturing.”
“Higher speed, higher deposition rates and better first-run quality – all of that figures into getting the product finished in a shorter amount of time.”
Lasers Shining Brighter
Advances in laser technology over the last decade are exciting interest in laser welding processes. Giants in traditional welding are on board with the movement and even leading the way.
“With the recent improvements in diode lasers, especially diodes that are pumping other lasers such as fiber and disk, it’s more effective for a wider range of applications,” says Paul Denney, Senior Laser Applications Engineer at Lincoln Electric. “The new fiber lasers and disk lasers are 25 to 30 percent wall plug efficient, compared to 8 percent or less for CO2 and NdYAG lasers of the past. They have much better beam quality, which means in many cases you can get a lot deeper and go a lot faster.”
Denney, the former director of the Laser Applications Laboratory at the Connecticut Center for Advanced Technology, and an MIT graduate with 25 patents and more than 30 years experience in laser materials processing, joined the company in 2010. That same year Lincoln Electric announced a strategic partnership with optical fiber laser pioneer IPG Photonics Corporation.
Fiber Lasers Dominate
Denney briefly explains the differences between the three main types of laser technologies. “Ytterbium fiber laser (or simply put, fiber laser) means that the ytterbium is a doping agent. It’s basically an element (Yb) that goes into a fiber and that’s what creates the light that we see. For CO2 lasers, you’re exciting a gas. In NdYAG lasers, you’re exciting a crystal.”
“In a fiber laser, it’s also a crystal that is excited, but they stretch it out so it’s about 15 meters long and 10 microns in diameter. That eliminates some of the thermal management issues. Then, instead of exciting the crystal with lamps or light like in NdYAG, which is less efficient, they use a group of diode lasers that are fiber optically connected to that bigger fiber to excite it. A disk laser is also ytterbium-based, but they take that crystal and cut it to a very thin wafer, where a reflective side acts also as a heat sink.”
According to Denney, fiber and disk lasers are the two big technologies competing for applications in today’s industrial market. “High-powered NdYAG lasers, the flavor of the month in the late 1990s and early 2000s, are going away. Their quality and power levels were limited and the efficiency was poor.”
“A large majority of laser cutting systems still use CO2 lasers, because the wattage per dollar is cheaper,” says Denney. “Fiber is taking some of the cutting away from CO2 lasers. We’ll have to wait and see how far it progresses into that market.”
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