Fiber-laser-pierced Technologies Deliver High-quality Cuts | Manufacturing Industries | advancedmanufacturing.org

Oct 31, 2024

Technology is constantly pushing to make the unimaginable a reality for aerospace manufacturing. It is an industry that does not accept “good enough” because only the most refined technology can bend the boundaries of today and bring us into tomorrow.

At the heart of this effort are very basic, elemental-metal building blocks: aluminum, chromium, iron, carbon, titanium, nickel, cobalt and other alloys.

Five-Axis laser-cutting cells equipped with robotic arms allow the fully automated cutting of complex parts.

Utilizing lasers to cut these metals for aeronautical and astronautical use was at one time a pipe dream, but is now a major contributing factor to delivering consistent repeatability with unprecedented precision and quality while minimizing scrap, optimizing workflow and reducing costs. Advanced machines equipped with five-axis lasers are piloting aerospace into the future.

Laser cutting initially brought the aerospace industry out of the world of hard tooling with CO2 lasers. However, these lasers had limited use and came at a significant cost—both monetarily and in productivity. CO2 lasers are strong, but the concentrated beams have a “halo,” a lower energy area immediately surrounding the focused beam, which alters the structure and affects the chemistry of the material it is cutting.

This heat-affected zone (HAZ) causes the perimeters to become brittle and more prone to fractures, negatively affecting the component’s fatigue performance and making it impossible to estimate the part’s lifespan. As a result, a secondary process would be required to mechanically remove the affected material, causing significant increases in labor and operating costs.

This, paired with safety regulations for aerospace, poses a low-capped contribution to advancements. Therefore, the majority of metal-fabrication processes were limited to punching, sheering, cold sawing and other non-thermal cutting methods in the CO2 laser era.

Then came the invention of the fiber-laser-pierced, non-thermal technologies, delivering high-quality cuts with a beam that generates extremely minimal HAZ. The pinpoint concentrated beam of the fiber laser significantly reduces the embrittlement of cut material at speeds far faster than non-thermal methods. While this yielded savings in scrap and labor, the extreme cost of these lasers posed a new challenge.

Over the past decade, competition, industrialization and further research around fiber lasers have driven down costs. Major milestones include the implementation of neodymium-doped fibers to improve laser efficiency, advances in widescale manufacturing of semiconductor diodes and an increase in laser lifespan through improvements in glass quality and durable coatings. Pairing fiber lasers with a head that can rotate around 3D objects while cutting was actualized by five-axis CNC technology—the last piece of the puzzle to compete with many popular non-thermal, metal-processing methods.

However, fiber lasers alone cannot provide solutions to all the needs of aerospace manufacturing. Machines housing lasers have evolved by robot manipulation, improved accuracy/repeatability and reduced scrap to enable wider use within the industry. Today, aerospace manufacturers are looking for technology that is:

The invention of robot manipulation systems to automatically feed, place and reposition material in different stages of the cutting process was a game changer for the industry. These robots present the material to the five-axis laser cutting head and stabilize the blank until the first stage of cutting is finished, the same way a fixture would. Then, the robot adjusts the part to a new location and orientation so the laser can continue the cut, enabling compatibility with preprocessed and complex-shaped parts that are common in aerospace.

Five-axis lasers are able to cut hydroformed, stamped, bent, deep drawn and other complex-shaped parts.

Assigning robots to automate the process eliminates the necessity for multistage fixtures, as the part is no longer required to be reset at the start of each stage. When combined with five-axis technology that can pivot around the part in 3D space, the laser cutting head can freely move across the entire part on its own, completely removing human error from the equation. In addition, the consistency and control actualized by five-axis laser cutting cells have contributed immeasurable value to rapid prototyping for bent tubing. This is especially pertinent to intricate and complex fuel lines, ventilation systems and hydraulics that pump life into aerospace vessels.

Most importantly, precision, accuracy and repeatability are key benefits that robot-equipped, five-axis laser-cutting cells provide aerospace fabricators. Because hard tooling no longer touches the part, external forces are not exerted on the metal during cutting, which is especially beneficial for thin materials that easily deform under the force asserted by hard tooling.

In addition, once the part is programmed, there is no need for human contact until the part is complete, providing the highest level of accuracy and repeatability as all variations potentially caused by humans are mitigated. This automation yields parts that can be processed tens of times faster than a human could do, with zero variation, translating to the minimization of scrap and an optimized return on investment.

Metal fabricators typically place speed among the highest values when evaluating tube or sheet-laser investments. The faster parts fly off the machines, the more quickly fab shops can move onto the next job. As laser power increases, metal can be cut at a much higher speed that is not 1:1 relative.

For example, increasing laser power from 12 kW to 20 kW could allow for more than double the speed output when cutting material of the same thickness. Despite being dramatically faster, the quality of the cut doesn’t necessarily reduce much, if at all. However, while quality is still a contributing factor in most industries, the threshold is significantly higher in aerospace manufacturing. Thus, the power used to cut aerospace parts must be fully controllable and preprogrammable to meet the requirements for optimal performance in the most extreme environments. This is what makes a five-axis laser-cutting cell truly shine.

Higher than optimal laser power output will create more HAZ in the finished part, which is unacceptable for aerospace. To mitigate this, the power on laser-cutting machines must be easily programmable and adjustable for complex parts. For example, when cutting a tube with many complex bends, the laser power must be actively and accurately throttled when moving around each corner. Rather than strength, the accuracy and speed of this power modulation become the deciding factor in producing high-quality parts the right way every time.

Similarly, the speed at which the laser moves when cutting the part is adapted in tandem with its output power to provide the highest quality cut for each unique material. Unlike high-volume parts, a laser cutting cell with a quick setup that produces high-quality parts from the get-go will yield the greatest value in aerospace manufacturing. Thus, carefully calculating and moderating the optimal power and speed for each unique cut from the start will minimize overall scrap, providing the most cost savings and the highest quality parts.

Popular parts for a five-axis laser cell cutting include hydraulic lines, fuel and oil lines, ventilation and exhaust systems, landing gear components, and covers for engine gears. Batteries and other parts that need to be shielded from heat or protected from human contact are also good candidates.

Aerospace manufacturing will always come with limitations. Hard tooling exerts extra force upon metal, which will affect the part’s end shape, and lasers will always expel heat that may cause chemical changes in the metal being cut.

A breakthrough in cooling technology would make the use of lasers more widespread in aerospace. For example, argon is currently used to keep the surface of the metal as cool as possible during laser cuts, but a new way to extract heat from the process could bring new possibilities. However, new processes must not pollute the freshly cut edges with inclusions of other elements that could alter the metal’s chemistry, so there is a need to invent a method of shielding the metal for cuts. It’s a catch-22 that is waiting for a breakthrough.

Interestingly, there are some very realistic possibilities on the horizon for implementing artificial intelligence and virtual or augmented reality to assist machine programming and control—especially when fine-tuning a laser-cutting head. These kinds of advancements will further reduce setup time for jobs and make the machines more user-friendly—a primary need for the industry.

In addition, advances in part scanning will unlock great potential. The ability to scan incoming blanks for inconsistencies would contribute to scrap reduction or elimination. There are currently some 3D-scanning technologies available, but they fall short in overall ROI and require more computing power to operate. Once this technology comes down in price, we’ll see some real advances in aerospace.

When considering laser cutting for aerospace parts, five-axis laser cells provide the most versatility for fabricators, enabling them to make precise and consistent cuts, efficiently cut atypical metals and support preprocessed parts.

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