A look inside:
Laser machining key to precision fabrication
Eric Nelson (right), vice president and chief technology officer, LAI International, stands next to a ring-cutting workstation. LAI International uses 10 multi-axis LASERDYNE systems to produce part features like aerospace and land-based turbine components. These systems regularly hold airfoil shape accuracy within 0.004-in. true position.
Multi-axis laser technology has a reputation for pushing the envelope, often driven by a champion of the technology who embraces it with creativity and zeal and takes it to new levels.
LAI International, a strategic supplier of precision components and sub-assemblies for original equipment manufacturers, champions advanced laser machining in multiple LAI facilities nationwide. For more than three decades, Eric Nelson, vice president and chief technology officer, LAI International, has stayed committed to one brand of laser system, LASERDYNE, applying, challenging, and helping to improve multi-axis laser technology for the most difficult aerospace and power-generation applications. Along the way, he has literally done it all — from pioneering the use of factory rebuilt systems, to beta testing and offering suggestions for developing hardware and software features that have become standard offerings, to routinely increasing productivity and quality with the laser systems he utilizes.
“We operate seven multi-axis laser systems here LAI International’s facility in Maine,” says Nelson, “five LASERDYNE 780 BeamDirectors and two LASERDYNE 890 BeamDirectors. All are refurbished systems that we regularly upgrade with LASERDYNE’s new software and hardware so that functionally they have the capabilities of new machines. By keeping up on everything new at LASERDYNE and implementing those things that can immediately help us, we provide customers like General Electric and Pratt & Whitney with the most productive and highest quality processes. We produce the really difficult parts efficiently for them.”
LAI also operates three additional LASERDYNE systems with 94-W laser process controls at its facility in Tucson, AZ. The workstations can handle rotary parts up to 48-in. diameter, pre-formed parts up to 24-in. high, and materials with thicknesses from the thinnest gauges to 1 in.
“We employ percussion, trepanning, and drill-on-the-fly laser drilling techniques for effusion cooling holes as well as full five-axis laser cutting on the pre-formed parts our customers supply,” says Mike Grantham, technical director, LAI Southwestern Laser, a division of LAI International. “This facility can drill holes as small as 0.005 in. in diameter at angles from 20° to 90° to the surface.”
Complex hole shapes are laser cut with 0.004-in. accuracy and high repeatability. Fifty sets of these parts are produced each week by LAI International using LASERDYNE laser systems.
Laser-processed vanes and turbine spacers
Rich Technology International is a diversified contract manufacturer and one of the five LAI International manufacturing facilities dedicated to supplying precision engineered components and assemblies for the aircraft, power-generation, and defense industries. With its laser systems, Rich Technology International does high-volume work and specializes in processing difficult materials such as Inconel, stainless steel, super-cobalt alloy, hybrid nickel, chrome steel, and Hastelloy X. Half of its laser jobs are for the aerospace industry and the other half is devoted to land-based turbines. Some of the work cannot be done efficiently using other processes such as EDM or waterjet machining. The laser work can call for drilling thousands of holes in a single part, everything from 0.003 in.-diameter rounds to percussion drilling and trepanning special shapes. Drilling angles range from 90° to as low as 10° to the surface.
A typical job — spacer bands for land-based turbines — requires laser cutting a series of accurately spaced complex profiles along the part contour. Part runs for this job average 40 to 50 sets a week using one of the refurbished LASERDYNE 890 BeamDirector systems equipped with a 3,000-W CO2 laser. The material is 440 stainless steel with a chrome additive — a very hard material — but processed efficiently on the system with consistently smooth, burr-free edges. Accuracies are a tight 0.004-in. true position total tolerance for the special airfoil shape, and speeds are relatively fast considering the geometry of the part features, says Nelson.
“Achieving this level of productivity and accuracies from one job to another is possible because of how LASERDYNE designs and integrates its system features,” he says. “Everything works perfectly together — the controller, software, motors, laser — because everything is LASERDYNE’s design and manufacture.”
A perfect example is LASERDYNE’s Automatic Focus Control (AFC). It’s a feature Nelson swears by and one with which he provided LASERDYNE feedback and saw refined through the years. AFC guides the motion system, maintaining critical focus position and following the contour of the part regardless of slight surface irregularities. With AFC, all machine axes react to sensing of the part surface, creating unlimited R-axis correction with high speed and unmatched sensitivity. AFC allows top machine speeds so that productivity is maximized without downtime or scrapped parts.
LAI International uses the trepanning laser drilling process with its LASERDYNE systems to produce hundreds of precision-shaped cooling holes in aerospace combustor components.
LAI International uses trepanning, percussion drilling, and drill-on-the-fly laser processing techniques in which the AFC feature is extremely important in the laser drilling processes. Trepanning is a process for creating holes where the part is held stationary and the laser beam is moved with simultaneous multiple action motion to create a round hole or any feature by cutting the periphery of the shape. LASERDYNE’s extremely accurate and repeatable laser positioning systems allow for very unique and tight tolerance trepanned features such as those pictured.
By contrast, percussion drilling delivers one or more pulses from the laser to a part while the laser beam and part are stationary. More than one pulse may be required depending on the material type and thickness. A variation of percussion drilling is “drill-on-the fly” where pulses are delivered to the part by the stationary laser while the part is rotated. The hole placement is a function of rotational speed and laser pulse frequency. If multiple pulses are required, drill-on-the-fly software developed by LASERDYNE engineers is used to synchronize the movement of the part to the laser pulses, ensuring that multiple pulses are delivered to the exact location required. By changing the laser pulse energy, pulse count, or lens focal length, the characteristics of the drilled hole size and taper can be controlled to meet the requirements of the part. Drill-on-the-fly software also allows changes of the pulse shape during the process to improve hole geometry.
“System repeatability (±0.0001 in.) of the machine really comes into play on our jobs,” Nelson says. Our LASERDYNE 890 and 780 BeamDirectors with their Automatic Focus Control features are designed so we maintain extremely good accuracy with consistency through the entire work envelope.”
Integrated design and manufacture
Nelson explains why he chose LASERDYNE’s multi-axis laser technology early on and stayed with it for decades: “Like any customer when multi-axis laser began in the 1980s, I wanted to go with the best. After exploring different models and makes, only one manufacturer offered systems with fully integrated software and hardware components of their own exclusive design and manufacture. That was LASERDYNE. They are the only manufacturer who manufactures their own controllers, workstations, and lasers. This was true in the 1980s and still true now. All of the modules work together the way they should, and if there’s a problem or an opportunity to improve the process there is one point of responsibility to get it right and that’s always been LASERDYNE. It’s key to doing the best work, the real reason we are able to push the technology edge and do multi-axis laser work where alternative processes and systems either have limitations or just won’t do the job.”
Peter Thompson, technical director of LASERDYNE, explains his company’s approach to integrating all system components:
“We learned in the early days of LASERDYNE that the key to getting the most from multi-axis laser processing required integrating the laser, motion system and control, user interface, and process sensors. The only way to do that was to design, manufacture, and integrate all of these components ourselves in the system. Our goal has always been to provide systems that were capable of the finest precision laser processing. Designing and manufacturing all of the major components of the system also allows us to introduce technology as it becomes available and to more tightly integrate the various components. The end result is superior process capability and control.”
Aircraft vane components (top) made of Inconel are laser drilled using a LASERDYNE 780 BeamDirector.
“Drilling with today’s systems integrates the optics of the laser with sensors in the machine tool structure and with the motion system,” says Thompson. “All are optimized for the unique work required of multi-axis laser processing. Remember, there are no significant tool forces with multi-axis laser processing and especially laser drilling. Without precise control over key components, it would be difficult for users like Eric Nelson at LAI International to achieve the performance levels, the speeds, and quality our systems deliver. The performance LAI is achieving is just too difficult to accomplish by ‘bolting together’ a collection of commercially off-the-shelf components. That is why we refer to our products as ‘systems’ and not just lasers or machine tools.”
Smaller aircraft engine components
With equipment options that include waterjet and EDM, Nelson’s equipment preference for laser drilling aircraft vane sector components is a LASERDYNE system with a BeamDirector because it provides higher feed rates and is more accurate, he says.
In the aircraft vane components job pictured, the Inconel part sets up quickly with minimal clamping pressure. Multi-axis laser machining is essentially a non-contact process, so highly rigid part clamping is not required. Using an updated LASERDYNE 780 BeamDirector equipped with a 1,500-W CO2 laser, 1,500 to 2,000 of these parts are laser processed at LAI, week after week, with only minimal operator adjustments.
Repeatability like this with positioning accuracy is a cumulative result of many factors working together that affect the overall laser system’s accuracy and the quality of the parts produced. Even system frames have an important influence on the successful integration of system components. The bases of the LASERDYNE 780 and 890 BeamDirector systems are carefully engineered foundations on which integrated accuracy features have been built. Most laser machining systems are not rigid enough to isolate and eliminate the vibrations induced by continuous back and forth movement of a few thousandths of an inch necessary in many of our projects, says Nelson.
“The multi-axis laser stands out as a very unique manufacturing system in today’s broad array of fabricating systems,” reports Nelson. “Getting the most out of a machine is one thing. Getting the most out of an entire manufacturing technology is something else. And it is much more challenging today because part features, hole configuration and size, material difficulty, speed, and quality required have exceeded anything thought possible even just a few years ago, let alone when this all began in the mid-1980s. With LASERDYNE, we’re meeting those challenges and more.”
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