Lasers Drill Precision Holes Quickly
New laser techniques can quickly drill very high-precision holes for aerospace, medical and microelectronics applications
By Patrick Waurzyniak
Laser technology for drilling precision holes has taken a leap forward with faster, cheaper, high-accuracy fiber lasers, which are used in the aerospace industry for turbine engine hole-drilling and other industries. Short-pulse picosecond fiber lasers are likewise making inroads, drilling small, precise holes for the medical and microelectronics industries.
For aerospace turbine engines, drilling ultra-precise holes that enable the effusion cooling used in the hot sections of the modern aircraft turbine engine is a mission-critical task. Builders of aircraft and power-generation turbine engines worldwide have adopted laser-drilling techniques that replace mechanical and EDM holemaking operations with laser technologies.
Many aircraft engine builders have turned to laser technologies as aerospace engineers adopted new designs more suited to laser drilling, noted Terry VanderWert, president, Prima Power Laserdyne LLC (Champlin, MN), a developer of laser-drilling systems. “Pratt & Whitney’s aircraft engine manufacturing was one of the early customers when we got involved with the turbine engine business. Suppliers all over the world now produce turbine engine components using laser processes for turbine engine OEMs, particularly in the hot section, including turbine blades and vanes, combustors, various sheetmetal parts, and we’ve watched the evolution and participated in the adoption of lasers.
“What we found in the early days was that lasers were the new technology and lasers had to be demonstrated to be more productive—faster, better, and lower cost—than the incumbent technology around which the part was designed,” said VanderWert. “A lot of those sheetmetal parts were designed to be manufactured using mechanical processes such as punching or milling. But we were able to demonstrate that the laser could be more cost-effective and more precise.”
Improved Lasers Shape New Designs
In the early 1990s, working with Prima Power Laserdyne customers, designers began to develop new engine component designs to take advantage of lasers, VanderWert said. “Having seen what lasers could do, they came up with a whole new design of the engine involving smaller, shallow [hole] angles that can be as shallow as 10º from the surface,” he noted. “A hole is typically 0.5 mm in diameter. Implementing the design, which they call effusion cooling, improves the energy efficiency of, and reduces the emissions from, turbine engines.”
With effusion cooling, the number of holes in aircraft turbine engine designs has expanded, noted Mark Barry, Prima Power Laserdyne vice president. An early design from Allison in Indianapolis of a turbine engine combustor had 2000 holes, Barry recalled. “We thought, ‘2000 holes, that’s going to take forever,’” he said. “A portion of the JSF engine has 2.5 million holes in it. That’s the difference in the designs of 20–25 years ago and those of today.”
Current designs involve very complex hole shapes and hole patterns that can change throughout the part, Barry noted. “Years ago, we might drill at one particular angle to the surface; today, it’s multiple angles, different hole sizes and different patterns,” he said. “It’s become very complex and you can understand that the designers have this incredible urge to run their engines hotter and hotter, because the hotter the engine runs, the more fuel-efficient it is. And that’s what it’s all about—reducing emissions, increasing fuel efficiency and prolonging the life of the engine components.”
With effusion cooling, thousands of holes are drilled in the combustors used in the hot sections of turbine engines, Barry noted. The designs enable cooling the hot section of the engine that frequently runs into temperatures above the metal’s melting point, he adds. “The temperatures that the engines run today are above the melt point of the materials. So if it wasn’t for the effusion cooling laying a bou