r cost and worked with the laser manufacturer [IPG Photonics] in the development of a QCW [Quasi Continuous Wave] laser with relatively high peak power and relatively low average power.”
Process Stability Is Key
Laser-drilling system designs mandate rigid structures and process controls. With the Laserdyne 795 laser system, users can drill, cut and weld medium to large 3D parts with a unique moving beam motion system. “Accuracy, ease of use, and process stability are critical,” Barry said of drilling effusion holes in turbine components that can cost thousands of dollars by the time the part reaches the laser system.
Much of Laserdyne’s software development centers on the requirement for consistent holemaking techniques, Barry added. “Back in the early days, everybody drilled round holes. When I say holes, you imagine holes that are circular. The idea of a shaped hole is foreign to most people,” he said. “With shaped holes, a question is ‘How exactly do you measure the hole?’ In the past 10 years, we have seen more requirements based on airflow through the hole. The airflow was almost a second requirement to the hole diameter. Blueprints today often specify an airflow with the hole diameter as a reference only. It challenges the people that are making the part.”
With the company’s current laser systems, users can measure the flow, and in the background, Laserdyne software adjusts hole size up or down, assuring the part meets design criteria. “Some parts are relatively simple, and you can drill the entire part and adjust,” Barry said. “All of this is done in the background with statistical process control. Another trend is to have different flow in different areas of the part; you can drill a portion of the part, adjust hole size if needed to achieve the correct overall flow, drill the next area, and repeat the process until the part is complete. The in-process flow check is the basis for these adjustments. The critical part of all laser drilling is to have the process under control. If the user has a good feeling about the hole size and geometry, then they can check it less.”
The latest capabilities enable users to drill production parts to air-flow tolerances of ±3% on parts with thermal barrier coating (TBC) or ±1% on simple metallic parts, Barry said.
Micro Drilling for Medical
Laser micromachining in medical or microelectronics applications often uses short-pulse fiber laser markers for drilling holes in applications including wafers, medical cannulae and microchannels for fluids, noted Mark L. Boyle, laser product engineer, Miyachi Unitek Corp. (Monrovia, CA).
A laser systems integrator, Miyachi Unitek integrates 1070-nm, pulsed fiber lasers into complete laser systems for drilling holes in metals and other materials for a range of different applications. “We also have the vanadate green and vanadate UV technologies, for plastics and for some metals, and also the picosecond lasers,” Boyle said. “We’re running the whole gamut of IR to UV and nanosecond to picosecond lasers, but metal processing with fiber lasers is really where we’ve been focused.
With short-pulse lasers, users can get very fine precision and very clean walls, Boyle noted. “It’s all dependent on what the user requires. What we find is for most applications, most people are fine with the results from an IR laser. Now and then they’ll have stiffer requirements on the edge quality of those holes. As you go smaller and smaller, into the hundreds of microns, to sub-hundred micron, everything becomes a lot more critical because you don’t want any melt around it, you don’t want it to re-form and grow back over the hole.”
Picosecond lasers offer the advantage of virtually no HAZ for holemaking operations, Boyle said. “Particularly from the picosecond lasers, those are no HAZ or very little HAZ. When you get to the nanosecond lasers, particularly the IR has a little bit more, but in some cases, you can still get a very good edge quality.”
These picosecond lasers have applications drilling metals, stainless, and aluminum, Boyle said, to about a 10-µm typical h