Machine Engineering – Innovations Report

Animal-inspired AI robot navigates unfamiliar terrain

Shrutika Srivastava — Mon, 14 Jul 2025 11:02:40 +0000

Researchers have created an Artificial Intelligence (AI) system that allows a quadrupedal robot to adjust its gait to various unknown terrains, akin to a genuine animal, marking what is considered a world first.

The innovative technology enables the robot to automatically modify its movement, rather than requiring instructions on when and how to adjust its stride, as is the case with current-generation robots. This advancement is regarded as a significant progression towards the potential deployment of legged robots in perilous environments where human safety may be compromised, such as nuclear decommissioning or search and rescue operations, where the failure to adapt to unforeseen circumstances could result in fatalities.

Robot learning to adapt its gait to simulated terrain. It simultaneously practised within hundreds of simulated environments. Image Credit: Joseph Humphreys, University of Leeds.

The project, undertaken by the University of Leeds and University College London (UCL), drew inspiration from the animal realm to instruct the robot in navigating unfamiliar terrain. This encompasses quadrupeds such as canines, felines, and equines, who are proficient at adapting to various terrains. These creatures alter their locomotion to conserve energy, sustain equilibrium, or react swiftly to dangers.

The researchers have developed a framework that instructs robots on how to transition between trotting, running, bounding, and other gaits, emulating mammalian behaviour in nature.

Modifying gaits as necessary

By incorporating the tactics employed by animals to traverse an uncertain environment, the robot swiftly adapts its gaits in response to varying terrain. Due to the data processing capabilities of AI, the robot, referred to as “Clarence,” acquired the requisite techniques in about nine hours, significantly quicker than the days or weeks typically required by most juvenile animals to traverse various surfaces with confidence.

In a paper published on July 11 in Nature Machine Intelligence, lead author Joseph Humphreys, a postgraduate researcher in the School of Mechanical Engineering at Leeds, elucidates how the framework allows the robot to adjust its stride in response to its environment, navigating diverse terrains such as uneven timber, loose wood chips, and overgrown vegetation, without necessitating modifications to the system itself.

He stated, “Our findings could have a significant impact on the future of legged robot motion control by reducing many of the previous limitations around adaptability.””

He stated: “This deep reinforcement learning framework teaches gait strategies and behaviour inspired by real animals – or ‘bio-inspired’ – such as saving energy, adjusting movements as needed, and gait memory, to achieve highly adaptable and optimal movement, even in environments never previously encountered.

“All of the training happens in simulation. You train the policy on a computer, then take it and put it on the robot and it is just as proficient as in the training. It’s similar to the Matrix, when Neo’s skill in martial arts is downloaded into his brain, but he doesn’t undergo any physical training in the real world.

“We then tested the robot in the real-world, on surfaces it had never experienced before, and it successfully navigated them all. It was really rewarding to watch it adapt to all the challenges we set and seeing how the animal behaviour we had studied had become almost second nature for it.”

Deep reinforcement learning agents typically excel at mastering a particular task but encounter difficulties in adapting to environmental changes. Animal brains possess inherent structures and information that facilitate learning. Certain agents may replicate this form of learning; but, their artificial systems typically lack the sophistication and intricacy of more advanced models. The researchers assert that they surmounted this problem by incorporating natural animal locomotion tactics into their system.

They claim to possess the inaugural framework that concurrently integrates all three essential elements of animal locomotion into a reinforcement learning system—specifically: gait transition strategies, gait procedural memory, and adaptive motion adjustment—facilitating genuine versatility for real-world application directly from simulation, without necessitating additional modifications on the physical robot.

The robot not only acquires the ability to move but also learns to choose which gait to employ, when to transition, and how to adapt it in real-time, even on unfamiliar terrain.

Professor Zhou, the principal author of the study from UCL Computer Science, stated: “This research was driven by a fundamental question: what if legged robots could move instinctively the way animals do? Instead of training robots for specific tasks, we wanted to give them the strategic intelligence animals use to adapt their gaits — using principles like balance, coordination, and energy efficiency.

“By embedding those principles into an AI system, we’ve enabled robots to choose how to move based on real-time conditions, not pre-programmed rules. That means they can navigate unfamiliar environments safely and effectively, even those that they haven’t encountered before.

“Our long-term vision is to develop embodied AI systems — including humanoid robots — that move, adapt, and interact with the same fluidity and resilience as animals and humans.”

Practical applications

Engineers are progressively emulating nature, referred to as biomimicry, to address intricate mobility difficulties. The crew asserts that their accomplishment signifies a significant advancement in enhancing the adaptability and proficiency of legged robots to navigate real-world challenges, particularly in hazardous locations or areas with restricted access. A robot proficient at traversing unfamiliar, intricate terrain presents new opportunities for applications in disaster response, planetary exploration, agriculture, and infrastructure inspection.

It proposes a viable approach for incorporating biological intelligence into robotic systems and facilitating more ethical examinations of biomechanics hypotheses; rather than subjecting animals to invasive sensors or jeopardising their safety to analyse their stability recovery response, robots can be utilised instead.

By drawing inspiration from the elements that facilitate efficient animal locomotion, the researchers devised a framework adept at navigating intricate and hazardous terrain, even in the absence of exteroceptive sensors—such as vision, olfaction, and auditory perception—that assist humans in their mobility.

Concurrent practice across many terrains

Employing deep reinforcement learning—an enhanced form of trial and error—the robot concurrently trained across numerous environments, initially addressing the challenge of locomotion with various gaits, subsequently selecting the optimal gait for the terrain, thereby developing the capacity for highly adaptable movement.

To evaluate this gained flexibility in practical environments, the robot was released onto various surfaces such as woodchip, rocks, overgrown roots, and loose timber, while also subjecting its legs to repeated impacts from a sweeping brush to assess its recovery from trips. The researchers utilised a predefined pathway or a joystick, much to those employed in video games, to manoeuvre the robot.

Surprisingly, the robot was not subjected to any challenging terrain during training, underscoring the system’s adaptability and indicating that these skills have become instinctual for the robot.

The research, partially financed by the Royal Society and the Advanced Research and Invention Agency (ARIA), concentrated on facilitating resilient daily mobility. In future endeavours, the team aspires to incorporate other dynamic skills, like long-distance jumping, climbing, and traversing steep or vertical terrains.

While the methodology has thus far been evaluated solely on a single dog-sized quadruped robot, the foundational principles has wide-ranging applicability. Identical bio-inspired measures can be used to a diverse array of quadrupedal robots, irrespective of their dimensions or mass, provided they exhibit analogous morphology.

Original Publication
Authors: Joseph Humphreys and Chengxu Zhou.
Journal: Nature Machine Intelligence
DOI: 10.1038/s42256-025-01065-z
Method of Research: Computational simulation/modeling
Subject of Research: Not applicable
Article Title: Learning to Adapt through Bio-Inspired Gait Strategies for Versatile Quadruped Locomotion
Article Publication Date: 11-Jul-2025

Original Source: https://www.nature.com/articles/s42256-025-01065-z

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Nimble Dimples: Agile Underwater Vehicles Inspired by Golf

Shahbaz Alam — Mon, 19 May 2025 10:37:35 +0000

A spherical prototype that can change its surface from smooth to dimpled cuts through drag and generates lift

Captions // Photos on Flickr // Video on Youtube

Underwater or aerial vehicles with dimples like golf balls could be more efficient and maneuverable, a new prototype developed at the University of Michigan has demonstrated.

Golf ball dimples cut through pressure drag—the resistance force an object meets when moving through a fluid—propelling the ball 30% further than a smooth ball on average. Taking this as inspiration, a research team developed a spherical prototype with adjustable surface dimples and tested its aerodynamics in a controlled wind tunnel.

“A dynamically programmable outer skin on an underwater vehicle could drastically reduce drag while eliminating the need for protruding appendages like fins or rudders for maneuvering. By actively adjusting its surface texture, the vehicle could achieve precise maneuverability with enhanced efficiency and control,” said Anchal Sareen, U-M assistant professor of naval architecture and marine engineering and mechanical engineering and corresponding author of two studies published in Flow and The Physics of Fluids.

These nimble vehicles could access typically hard-to-reach areas in the ocean while conducting surveillance, mapping new areas or collecting data on water conditions.

Sareen and colleagues formed the prototype by stretching a thin layer of latex over a hollow sphere dotted with holes, resembling a pickleball. A vacuum pump depressurizes the core, pulling the latex inwards to create precise dimples when switched on. Turning off the pump makes the sphere smooth again.

To find out how the dimples affected drag, the sphere was put to the test within a 3-meter-long wind tunnel, suspended by a thin rod and subjected to different wind velocities.

For each flow condition, the dimple depth could be finely adjusted by shifting the vacuum pump’s strength. Drag was measured using a load cell, a sensor that detects force exerted by airflow on the object. At the same time, an aerosol was sprayed into the wind tunnel while a high-speed laser and camera captured the motion of the tiny particles as they flowed around the sphere.

For high wind speeds, shallower dimples cut the drag more effectively while deeper dimples were more efficient at lower wind speeds. By adjusting dimple depth, the sphere reduced drag by 50% compared to a smooth counterpart for all conditions.

“The adaptive skin setup is able to notice changes in the speed of the incoming air and adjust dimples accordingly to maintain drag reductions. Applying this concept to underwater vehicles would reduce both drag and fuel consumption,” said Rodrigo Vilumbrales-Garcia, a postdoctoral research fellow of naval architecture and marine engineering at U-M and contributing author to the studies.

The smart morphable sphere can also generate lift, allowing for controlled movement. Often thought of as the upwards force responsible for keeping planes in the air, lift can work in any direction as long as it is perpendicular to the direction of the flow.

To achieve this, researchers designed the inner skeleton with holes on only one side, causing the sphere to develop one smooth and one dimpled side when activated.

This created asymmetric flow separation on the two sides of the sphere, deflecting the wake toward the smooth side. By Newton’s third law, the fluid applies an equal and opposite force toward the rough side, effectively pushing the sphere in the direction of the dimples. Dimples on the right generate force to the right while those on the left push left. This enables precise steering by selectively activating dimples on the desired side.

The team tested the new sphere in the same wind tunnel setup with varying wind velocity and dimple depth. With the optimal dimple depth, the half rough/half smooth sphere generated lift forces up to 80% of the drag force. The lift generation was as strong as the Magnus effect, but instead of using rotation, it was created entirely by modifying the surface texture.

“I was surprised that such a simple approach could produce results comparable to the Magnus effect, which requires continuous rotation,” said Putu Brahmanda Sudarsana, U-M graduate student in mechanical engineering and contributing author to the studies.

“In the long run, this could benefit, for example, compact spherical robotic submarines that prioritize maneuverability over speed for exploration and inspection. Typically, these submarines would require multiple propulsion systems, but this mechanism could help reduce that need.”

Looking ahead, Sareen anticipates collaborations that combine expertise in materials science and soft robotics, further advancing the capabilities of this dynamic skin technology.

“This smart dynamic skin technology could be a game-changer for unmanned aerial and underwater vehicles, offering a lightweight, energy-efficient and highly responsive alternative to traditional jointed control surfaces,” she said. “By enabling real-time adaptation to changing flow conditions, this innovation promises to enhance maneuverability, optimize performance and unlock new possibilities for vehicle design.”

Drag study: Adaptive drag reduction of a sphere using smart morphable skin (DOI: 10.1017/flo.2025.7)

Lift study: On the lift generation over a sphere using asymmetric roughness (DOI: 10.1063/5.0241948)

Original Publication
Authors: Rodrigo Vilumbrales-Garcia, Putu Brahmanda Sudarsana and Anchal Sareen.
Article Title: Adaptive drag reduction of a sphere using smart morphable skin
Article Publication Date: 19-May-2025
DOI: 10.1017/flo.2025.7

Media Contacts

Katherine McAlpine
University of Michigan
kmca@umich.edu

Patricia DeLacey
University of Michigan
pdelacey@umich.edu

Frequently Asked Questions

How does the depth of dimples on a sphere affect drag reduction in different flow conditions?

The depth of dimples significantly impacts drag reduction. Shallower dimples are more effective at higher flow speeds, while deeper dimples can initially reduce drag but may lead to increased drag if the depth exceeds a certain point.

What is the significance of the predictive model developed in the study?

The predictive model links the optimal dimple depth to the flow conditions, allowing for real-time adjustments to minimize drag. This means that the surface can adapt to changing flow speeds, improving efficiency.

What practical applications could benefit from the findings of this research?

The findings could enhance the efficiency and maneuverability of unmanned underwater and aerial vehicles, making them more effective in various engineering applications by reducing drag.

Source: EurekAlert!

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Innovative Advances in High-Speed Industrial Stamping Processes

redaktion — Thu, 12 Dec 2024 09:20:06 +0000

In industrial stamping processes, several hundred sheet metal parts are typically produced per minute. Together with the stamped parts manufacturer Quittenbaum GmbH, researchers at Fraunhofer IPM have now for the first time developed and installed an optical inspection system that checks the dimensional accuracy of every single component in high-speed stamping processes – with an accuracy in the range of 100 micrometers.

The geometric deviations are depicted in 16 different views on the user interface. © Fraunhofer IPM

Connectors, sleeves or pins are stamped from sheet metal with high precision and in high volumes. They are used in numerous high-tech products such as automobiles, in telecommunications, in electronic systems or in medical technology. Until now, quality assurance has not been able to keep pace with the high production cycle in stamping processes. As a result, stamped parts are usually only tested on a random basis by visual inspection or with the help of CT scans. Using a free-fall inspection system, a team from Fraunhofer IPM has succeeded in checking the geometric dimensional accuracy of 3D precision parts in the production cycle for the first time. The system was tested in a production process for plug connectors made of copper sheet, of which 330 parts per minute are manufactured.

The system captures 330 parts per minute

A component feeder developed by the manufacturer transports the individual parts, which are up to 40 mm in size, from the punching machine into a test sphere without any further handling. As the parts fall through the sphere, they are captured from different perspectives by 16 high-resolution cameras. The objects are captured without shadows or reflections thanks to an indirect LED flash illumination. The measurement data is checked against the nominal CAD model so that defective parts can be ejected immediately. The high processing rate for this computationally intensive analysis is achieved by fast inspection algorithms, parallelized camera control and several evaluation computers. During test operation, defective parts with geometric deviations in the range of 100 micrometers were reliably identified. The measurements were verified on a random basis using CT scans.

In a follow-up project, the partners from Fraunhofer IPM and Quittenbaum intend to investigate how the surface of the stamped parts can be efficiently inspected.

The FrInSt project

Free-fall inspection system for 100-percent inline inspection of complex 3D precision stamp parts

This R&D cooperation project was funded by the Federal Ministry for Economic Affairs and Climate Action as part of the Central Innovation Program for SMEs (Zentrales Innovationsprogramm Mittelstand – ZIM, support code 5004202KK1)

Project term
2021/01/11 – 2024/29/02

Project partners
Fraunhofer IPM, Quittenbaum GmbH

Wissenschaftliche Ansprechpartner:

Dr. Tobias Schmid-Schirling tobias.schmid-schirling@ipm.fraunhofer.de

Weitere Informationen:

http://www.ipm.fraunhofer.de/en Fraunhofer Institute for Physical Measurement Techniques IPM

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Fastest Swimming Soft Robot Inspired by Manta Rays

redaktion — Thu, 05 Dec 2024 12:33:38 +0000

A team of researchers has beaten its own record for the fastest swimming soft robot, drawing inspiration from manta rays to improve their ability to control the robot’s movement in the water.

“Two years ago, we demonstrated an aquatic soft robot that was able to reach average speeds of 3.74 body lengths per second,” says Jie Yin, corresponding author of a paper on the work and an associate professor of mechanical and aerospace engineering at North Carolina State University. “We have improved on that design. Our new soft robot is more energy efficient and reaches a speed of 6.8 body lengths per second. In addition, the previous model could only swim on the surface of the water. Our new robot is capable of swimming up and down throughout the water column.”

The soft robot has fins shaped like those of a manta ray, and is made of a material that is stable when the fins are spread wide. The fins are attached to a flexible, silicone body that contains a chamber that can be pumped full of air. Inflating the air chamber forces the fins to bend – similar to the down stroke when a manta flaps its fins. When the air is let out of the chamber, the fins spontaneously snap back into their initial position. Video of the robot can be seen here: https://youtu.be/pXB9Ip7qa0o.

“Pumping air into the chamber introduces energy into the system,” says Haitao Qing, first author of the paper and a Ph.D. student at NC State. “The fins want to return to their stable state, so releasing the air also releases the energy in the fins. That means we only need one actuator for the robot and allows for more rapid actuation.”

Studying the fluid dynamics of manta rays also played a key role in controlling the vertical movement of the soft robot.

“We observed the swimming motion of manta rays and were able to mimic that behavior in order to control whether the robot swims toward the surface, swims downward, or maintains its position in the water column,” says Jiacheng Guo, co-author of the paper and a Ph.D. student at the University of Virginia. “When manta rays swim, they produce two jets of water that move them forward. Mantas alter their trajectory by altering their swimming motion. We adopted a similar technique for controlling the vertical movement of this swimming robot. We’re still working on techniques that will give us fine control over lateral movements.”

“Specifically, simulations and experiments showed us that the downward jet produced by our robot is more powerful than its upward jet,” says Yuanhang Zhu, co-author of the paper and an assistant professor of mechanical engineering at the University of California, Riverside. “If the robot flaps its fins quickly, it will rise upward. But if we slow down the actuation frequency, this allows the robot to sink slightly in between flapping its fins – allowing it to either dive downward or swim at the same depth.”

“Another factor that comes into play is that we are powering this robot with compressed air,” Qing says. “That’s relevant because when the robot’s fins are at rest, the air chamber is empty, reducing the robot’s buoyancy. And when the robot is flapping its fins slowly, the fins are at rest more often. In other words, the faster the robot flaps its fins, the more time the air chamber is full, making it more buoyant.”

The researchers have demonstrated the soft robot’s functionality in two different ways. First, one iteration of the robot was able to navigate a course of obstacles arrayed on the surface and floor of a water tank. Second, the researchers demonstrated that the untethered robot was capable of hauling a payload on the surface of the water, including its own air and power source.

“This is a highly engineered design, but the fundamental concepts are fairly simple,” Yin says. “And with only a single actuation input, our robot can navigate a complex vertical environment. We are now working on improving lateral movement, and exploring other modes of actuation, which will significantly enhance this system’s capabilities. Our goal is to do this with a design that retains that elegant simplicity.”

The paper, “Spontaneous Snapping-Induced Jet Flows for Fast, Maneuverable Surface and Underwater Soft Flapping Swimmer,” is published open access in the journal Science Advances. The paper was co-authored by Yinding Chi and Yaoye Hong, former Ph.D. students at NC State; and by Daniel Quinn and Haibo Dong of UVA.

This work was done with support from the National Science Foundation under grants 2126072 and 2329674; and from the Office of Naval Research under grant N00014-22-1-2616.

Journal: Science Advances
Method of Research: Experimental study
Subject of Research: Not applicable
Article Title: Spontaneous Snapping-Induced Jet Flows for Fast, Maneuverable Surface and Underwater Soft Flapping Swimmer
Article Publication Date: 4-Dec-2024
COI Statement: none

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Understanding Detonation: The Science of Supersonic Combustion

redaktion — Wed, 04 Dec 2024 13:39:33 +0000

Detonation is a supersonic combustion wave, characterized by a shock wave driven by the energy release from closely coupled chemical reactions. It is a typical form of pressure gain combustion, converting chemical energy into thrust efficiently. The concept of harnessing detonation to improve thermodynamic cycle efficiency and enhance the performance of aerospace propulsion systems has been a subject of interest for many years. Since the 1950s, various types of detonation engines have been proposed, including pulse detonation engines, oblique detonation engines, and rotating detonation engines. However, these three types of detonation engines encounter challenges such as poor thrust continuity, high starting Mach numbers, and insufficient performance gains, which limit the widespread application of detonation propulsion technology.

In a recent article featured in the Chinese Journal of Aeronautics, Dr. Haocheng Wen and Prof. Bing Wang from Tsinghua University proposed a new concept for detonative propulsion, called the Ram-Rotor Detonation Engine, which is expected to break through the limitations of the above-mentioned detonation engines.

“The original intention of developing this new engine is to improve the structures of rotating detonation engines,” said Dr. Haocheng Wen, “this concept is also inspired by the ram-rotor compressor.” The ram-rotor detonation engine, abbreviated as RRDE, mainly consists of a rotating rotor with blades, and a stationary casing. The blades on the rotor are distributed in a helical symmetric manner. The combustible mixture undergoes compression, detonation combustion, and expansion within the variable cross-sectional channels between the blades.

The authors performed primary theoretical and numerical investigation on the RRDE. They established a theoretical model to analyze the relationship between the propulsion performance and parameters such as inlet velocity, rotor rim velocity, and equivalence ratio. It is indicated that for the stoichiometric hydrogen/air mixture, the total pressure gain of RRDE can exceed 3. Furthermore, they also conducted numerical simulations on the typical structure of RRDE and obtained the characteristic flow field and propulsion performance of engine. Their simulation results demonstrate that the detonation wave can stabilize and remain stationary within the blades by the given configuration, and can adapt to the variations in parameters such as the equivalence ratio within a certain range. “Our study primarily verifies the performance benefits and operation feasibility of the RRDE.” said Dr. Haocheng Wen.

The authors believe that the RRDE has several advantages, including a simple and compact structure, high efficiency, and the adaptability to a wide-range of flight Mach number. However, they also candidly acknowledge that the realization of the RRDE is confronted with numerous challenges that demand resolution, such as the stabilization mechanism of detonation wave, supersonic boundary layer interference, implementation of high-speed rotor, as well as thermal protection, etc. “Our team is conducting ongoing research on key scientific and engineering issues in RRDE.” said Prof. Bing Wang. They expect the RRDE can provide high-performance propulsion for the supersonic vehicles in the future.

About Chinese Journal of Aeronautics

Chinese Journal of Aeronautics (CJA) is an open access, peer-reviewed international journal covering all aspects of aerospace engineering, monthly published by Elsevier. The Journal reports the scientific and technological achievements and frontiers in aeronautic engineering and astronautic engineering, in both theory and practice. CJA is indexed in SCI (IF = 5.3, top 4/52, Q1), EI, IAA, AJ, CSA, Scopus.

Original Source

Haocheng Wen, Bing Wang. Primary investigation on Ram-Rotor Detonation Engine [J]. Chinese Journal of Aeronautics, 2024, 37(11):66-80, https://doi.org/10.1016/j.cja.2024.05.016.

Journal: Chinese Journal of Aeronautics
DOI: 10.1016/j.cja.2024.05.016
Article Title: Primary investigation on Ram-Rotor Detonation Engine
Article Publication Date: 6-Nov-2024

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Mass Production of Fuel Cell Bipolar Plates Revolutionizes Energy

redaktion — Mon, 02 Dec 2024 11:30:48 +0000

A thing of the past!

Bipolar plates for fuel cells are mass produced every second. The forming tools used to manufacture them are milled from high-quality metal alloys that provide them with high wear resistance. In the National Action Plan for Fuel Cell Production (H2GO), the Fraunhofer Institute for Laser Technology ILT in Aachen is breaking new ground: Instead of milling the tools from an expensive solid block, the institute is using extreme high-speed laser material deposition (EHLA) to apply wear-resistant functional layers to low-cost structural steel close to the final contour. This reduces costs, construction time and tool wear.

“We are taking a completely new approach,” reports Dora Maischner, project manager at Fraunhofer ILT. “Until now, forming tools for bipolar plates have been milled from high-quality tool steel in processes that take hours. We apply a wear-resistant functional layer close to the final contour on low-cost material.“ The researcher is working on a sub-project of R2HP (Ready to Hydrogen Production). This sub-project is part of the large-scale research project H2GO – National Action Plan for Fuel Cell Production, in which 18 institutes of the Fraunhofer-Gesellschaft are involved throughout Germany. Fraunhofer ILT is working with the neighboring Fraunhofer Institute for Production Technology IPT and the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz to develop the new process for manufacturing bipolar half plates. They aim to increase the service life of the highly stressed and precisely structured forming tools, while at the same time reducing their costs and construction times, and also to establish an efficient repair process for damaged or worn tools. The key to this is the extreme high-speed laser material deposition (EHLA) developed at Fraunhofer ILT.

Revolutionary approach to tool production

Modern ELHA 3D systems achieve speeds of more than 30 meters per minute. Thanks to digital process chains, the wear-resistant functional layers can be applied quickly and efficiently using the additive process. In addition, the three-dimensional material structure can be controlled so precisely that the highly wear-resistant layer welded onto low-cost structural steel comes very close to the intended final contour. Previously, it was milled from a solid block in an hour-long process that is very demanding on the milling tool; now it only needs to be finished in a targeted manner. The new EHLA-based process chain also minimizes costs because only a thin functional layer of high-quality material needs to be applied. At the same time, since the material is applied to near-net-shape and the mechanical processing is minimized, the construction time and tool costs for the milling heads, subject to enormous stresses from the high-strength material, can be reduced considerably.

Test facility in the H2GO project: Fraunhofer ILT coats components for fuel cells quickly and precisely with wear-resistant coatings on an EHLA system in preparation for large-scale production. © Fraunhofer ILT, Aachen, Germany

What makes the EHLA process so special? The powder melts above the workpiece in the laser beam – in other words, it is deposited on its surface already in liquid form. “In the EHLA process, it is not the component but the powder that absorbs a large part of the laser energy before it hits the workpiece,“ explains Viktor Glushych, group manager Coating LMD and Heat Treatment at Fraunhofer ILT. The patented process significantly accelerates the deposition process compared to conventional laser cladding processes, minimizes the thermal load on the components and creates more homogeneous microstructures in the metal layers. This, in turn, improves wear resistance.

Increased wear resistance

The coating materials used in the ongoing research project are the high-speed steel 1.3343 and the martensitic stainless steel alloy Ferro55, both of which are characterized by high hardness and wear resistance. Maischner explains: “1.3343 has a hardness of around 830 HV0.5 and Ferro55 around 820 HV0.5. This puts them in the range of the standard tool steel 1.2379, which is used in both hardened and unhardened states.“ The wear protection can be applied at a coating speed of 30 meters per minute; a coating thickness of approx. 1.2 millimeters is achieved per layer. The required coating thickness can be set by applying several layers, a coating thickness of one millimeter in this case. The digital control system ensures that the material forms precisely and selectively, an advantage that makes it possible to produce robust wear protection coatings. According to the team’s findings, the coating structure is even more important for wear protection than the hardness of the material. “This is because wear resistance depends to a very high degree on the microstructure of the material,” says Glushych.“EHLA produces extremely fine-grained microstructures, which improve the mechanical properties and, thus, significantly reduce abrasion. The fine-grained structure gives the coatings high resistance to wear, even under heavy loads.”

The moment of truth comes with the sliding friction wear test

In order to precisely evaluate wear resistance, Fraunhofer ILT uses a sliding friction wear test from the Clausthal University of Technology, which simulates realistic wear scenarios for the application. The system presses a pin onto a counter plate with a defined force and moves it back and forth. The amount of material removed can then be measured very precisely. The results to date indicate significant advantages of the test specimens coated using EHLA compared to those manufactured with conventional materials.

To demonstrate the new EHLA-based process chain in practice, the team has set up a demonstrator on which it has used EHLA to coat simple structural steel (St37) with the high-speed steel 1.3343 close to the final contour. Both conventional milling and structuring with ultrashort pulse lasers are used for finishing at Fraunhofer ILT. Since mechanically processing materials with high hardness causes significant tool wear, the non-contact laser process is of great industrial interest. “Our aim in the project is to prove that the entire process chain from coating to structuring the biopolar plates is already covered by near-series processes,“ explains Maischner. The researchers want to test the resilience and wear resistance of different forming tools on a test stand at Fraunhofer IPT by the end of this year. They are focusing on forming processes close to series use, in which a bipolar plate has to be stamped every second, as required for efficient industrial production.“The method allows us to realistically test the service life of tools coated with EHLA,“ explains Maischner.

Re-use: tools with multiple lives

The team is also focusing on the efficient production and reuse of tools. “We are already in contact with companies that manufacture tools for bipolar plates and have received very positive feedback,“ explains Glushych. What is attracting interest, in particular, is the possibility of building up functional layers close to the final contour at the typical EHLA process speeds and, thus, significantly shortening the time-consuming machining ablative steps. The option of reconditioning worn tools using the same EHLA process has also met with positive feedback. This is because instead of having to melt down tools at the end of their service life, the industry can rebuild the defective or worn contours and mechanically finish them using EHLA in accordance with the digitally stored construction plan.

The new process chain can thus pave the way for repeated re-use of tools; such closed-loop processes are in demand because they prevent the downgrading of high-quality alloys and also eliminate the need to melt down worn tools and to transport the parts, both of which consume a great deal of energy. As soon as the tool wears out, users can mill the layer back to a defined, digitally stored contour on site and coat it again using EHLA. “This procedure conserves resources and allows tools to be used for the long-term,“ emphasize the Fraunhofer researchers.

EHLA coating reduces fine dust pollution

Successes in the passenger car sector may encourage other potential users to enter this new form of toolmaking. EHLA has proven to be an effective process for wear protection coating: In the case of brake discs, the thin, firmly adhering EHLA protective coatings have been able to significantly minimize abrasion. The advantage not only benefits car owners, but also can significantly reduce the amount of particulate matter in the environment. This know-how forms the ideal basis for advancing the mass production of ultra-thin bipolar plates for commercial vehicles.

H2GO – National Action Plan for Fuel Cell Production

The H2GO project started in May 2022 and will run until November 2025. The Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz is coordinating the joint project, which is funded by the Federal Ministry of Digital and Transport (BMDV) with 80 million euros. Eighteen Fraunhofer Institutes are developing cost-effective production methods for fuel cells in order to convert heavy duty vehicles to emission-free drivetrains. “With our funding, we want to help generate marketable products from research on an industrial scale,“ explained Transport Minister Dr. Volker Wissing at the project launch.

EHLA process – an innovation from Fraunhofer ILT

The Fraunhofer Institute for Laser Technology ILT has continued to develop the patented Extreme High-Speed Laser Material Deposition (EHLA) process for new applications since 2012. This allows surfaces to be protected against wear and corrosion in an efficient and environmentally friendly manner. In the EHLA process, the powder is melted directly in the laser beam before it hits the component. As a result, the powder absorbs the majority of the laser energy, which significantly reduces the thermal load on the base material. Coating speeds reach several hundred meters per minute and layers with a thickness of 30 to 400 micrometers can be produced.

The process is also cost-effective, as up to 90 percent or more of the material used is actually applied to the component. Applications can be found in the automotive and aviation industries as well as in offshore facilities, where resistance to wear and corrosion is required.

The process has become more versatile with the extension to EHLA3D: Fraunhofer ILT has transferred the process to high-speed kinematics in collaboration with the machine manufacturers Ponticon and Makino. Now EHLA3D not only enables fast coating, but also the precise additive manufacturing of complex, three-dimensional geometries with various high-strength materials such as tool steels, titanium and aluminum.

EHLA has received several awards, including the Joseph von Fraunhofer Prize in 2017 and second place in the Steel Innovation Award in the “Steel in Research and Development“ category in 2018, as well as the first Berthold Leibinger Innovation Award.

Wissenschaftliche Ansprechpartner:

Viktor Glushych M. Sc
Head of Coating LMD and Heat Treatment Group
Telephone +49 241 8906-152
viktor.glushych@ilt.fraunhofer.de

Dipl.-Ing. Dora Maischner
Group Coating LMD and Heat Treatment
Telephone +49 241 8906-8017
dora.maischner@ilt.fraunhofer.de

Fraunhofer Institute for Laser Technology ILT
Steinbachstraße 15
52074 Aachen, Germany
www.ilt.fraunhofer.de

Weitere Informationen:

https://www.ilt.fraunhofer.de/en.html

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