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Hybrid Lightweight Construction - The right mix is key
Date Published：3/15/2017 04:03:14 PM
Hybrid lightweight construction technologies are based on the ideal mix of materials
A smart combination of materials like steel, aluminum, magnesium or carbon fiber reinforced plastics (CFRP) is the goal.
The process gains the public’s attention mostly through the manufacture of mixed construction airplanes or cars, but vehicle and aircraft manufacturers are not the only ones active in this field, as a new development at Engel Austria GmbH from Schwertberg, Austria, shows.
The injection molding machine manufacturer established a technology center for lightweight construction composites at the headquarters of its large-scale machine plant in St. Valentin in 2012, to serve as a platform for interdisciplinary collaboration with international universities and partner companies. The cooperation partners there work on fiber composites, for example organic sheets and fiber bands with directed properties.
Working group thinking outside the box
Head of the center, Peter Egger, is actively involved with the new VDMA Hybrid Lightweight Technologies working group (WG), which developed out of the VDMA Forum Composite Technology, as its Chair. “It is only natural that knowledge gained in the forum was limited, since the group consisted solely of mechanical engineers,” Egger recalls. The new working group now represents the entire spectrum of lightweight construction. “This allows us to recognize the requirements of the market better. All in all, the idea is to achieve the very best results and not be afraid to think outside the box,” Egger says, welcoming the foundation of the platform.
The expertise of the Austrian mechanical engineering company can now inspire the members of the new VDMA WG to find their own hybrid solutions. For example, the technology center for lightweight composites has come up with a component for a new lightweight pick-and-place robot to supplement the company’s own range of robots. “We tweaked two things: the kinematics and the moving masses,” reports Egger. “Due to the mixed construction of cast aluminum and thermoplastic carbon fiber plastic tapes, the weight of the robot’s swivel arm could be reduced by 40 percent compared to the version made from pure cast aluminum.” The lightweight construction solution significantly increases the robot’s performance and energy efficiency. It requires less electrical energy for stopping, because the reduced weight creates less holding torque, and it also accelerates 20 percent more quickly.
Smart combination of materials
Marc Kirchhoff of Trumpf Laser- und Systemtechnik GmbH in Ditzingen is a member of the Board of the VDMA Hybrid Lightweight Technologies working group. The manager for lightweight construction and electromobility talks about participation in the working group: “Here, too, the trend is heading more and more towards hybrid lightweight construction, i.e. combining materials in a smart way.” In vehicle production, this means that cars are manufactured from a mixture of materials including steel, aluminum, plastics and even fiber reinforced plastics.
With regard to hybrid compounds, he says that the question of how the materials can be processed is ever-present. This is where the laser manufacturer comes in. “A laser provides many opportunities for processing these materials in the first place, such as cutting, texturing and the like,” says Kirchhoff. “The challenge is to combine all the different materials. A laser is one of the most suitable tools for producing mixed compounds of metal and plastic, for example.”
New impetus for hybrid technology
Even traditional mechanical engineering companies are already working with hybrid constructions. The employees at Trumpf are well versed in this area, since they also use hybrid technology in their own production. For example, the company combines classic steel frames with carbon fiber reinforced plastics in laser cutting machines. “We use CFRP, for example, for highly dynamic moving parts like the drive axles,” Kirchhoff reports, “but our customers who make highly productive machines also rely on weight saving measures for moving parts.”
All the industries share a common denominator: The success of hybrid lightweight construction depends entirely on early integration. “Ideally, the customer gets us on board early on, during construction,” says the expert. When the material is processed with the right technology, the user can get even more out of the lightweight construction, he says. For example, the type of aluminum determines whether it can be laser welded with or without an auxiliary wire. “If the user changes something based on our advice, we can make processing more productive,” Kirchhoff explains, based on his experience.
According to Lothar Gräbener, Director of Sales in the Hydraulics, Sheet Metal Forming and Lightweight Construction division at Schuler Pressen GmbH in Waghäusel, Germany and other European countries are comparatively well-positioned internationally when it comes to lightweight construction. But the competition does not rest, he says. His observations have revealed that the USA, China, Japan and Korea are also working on lightweight construction. Reason enough for the expert to be actively involved in the VDMA Hybrid Lightweight Technologies working group as a member of the Board.
Effective production technology
Gräbener sees a great deal of potential in vehicle and aircraft construction. He considers car and truck production especially interesting for mechanical and plant engineering companies, because their high quantities demand effective systems. “As a supplier of systems for sheet metal and solid forming, Schuler is heavily involved in the development of forming processes for the new lightweight construction materials,” Gräbener explains. “We invest in and develop new procedures and processes both in our own TechCenters and in collaboration with other facilities and universities.”
This year, for instance, Schuler opened a Hot Stamping TechCenter at its site in Göppingen. The focus is on a complete production system incorporating state-of-the-art technology, with which the company hopes to develop the hot stamping process further. Schuler customers can also use the system.
Gräbener sees Schuler’s system solutions as a strength, since they enable the production of components with hybrid lightweight construction technology. For him, the various types of hybridization, such as hybrid manufacturing processes and material combinations of steel and aluminum or CFRP, are promising solutions.
Producing higher-strength components
As an example, Gräbener quotes the combination of hydroforming with press hardening, which allows significantly higher-strength components to be produced than in conventional hydroforming processes. Hydroforming is where a material is formed using an emulsion of water and oil that is subjected to a high pressure of several 1,000 bar. Press hardening involves forming with heated sheet metal, which has proven especially useful in vehicle body construction. The sheet steel plates are heated to 930 degrees Celsius before being fed into the forming press. The steel is then allowed to cool to below 400 degrees Celsius in the tool. The structural transformation that takes place during this process sets the steel, which more than doubles its strength. “The component’s sheet thickness can be reduced accordingly, and the overall weight of the body falls significantly,” reports Gräbener.
But Schuler is active in more than just new types of steel: new hybrid materials are a topic, too. “When it comes to the material combination for fiber reinforced plastics, the combination of long and continuous fibers offers particularly great potential for lightweight construction from an economic point of view,” Gräbener explains. “With this in mind, we are currently conducting a larger research project in collaboration with RWTH Aachen University.”
Networking at the mechanical engineering level
Nearly 100 years ago, what is now Herbert Hänchen GmbH & Co. KG in Ostfildern started repairing motors. The family company - now in its third generation - used this processing expertise to begin developing and producing hydraulic drives. Lightweight construction products are now also being made from CFRP in Ostfildern, and the company is actively involved in the VDMA Hybrid Lightweight Technologies working group. “It’s an ideal discussion network for us,” says Head of Marketing Sarah Bässler, praising the new working group. “What makes it attractive for us is that this is happening on a level of mechanical engineering that we are deeply rooted in.”
Rustproof CFRP components in small-scale production
“We are also looking for the users from mechanical engineering companies,” adds Klaus G. Wagner, Head of Development at Hänchen. “We want to convince them that CFRP products are superior to conventional components.” Hänchen began small-scale production of CFRP components for mechanical engineering eighteen months ago. This differs in every aspect from the classic manufacturing process, in which Hänchen produces hydraulic drives with high surface quality from metal via turning, milling, drilling and finally precision processing (honing). “Our initial goal was to provide light, rustproof CFRP alternatives to the cylinders and piston rods made from steel,” Wagner says.
The “art of sealing” from Ostfildern
The requirements for the material are high, as hydraulics have to withstand strong forces and operating pressures and be tight due to the use of hydraulic oil. Hänchen further developed the filament winding process - a special winding technique - in such a way that the CFRP cylinder stays reliably sealed. In this winding process, the quantity and direction of the fibers are designed with precision for each application. Furthermore, CFRP is an anisotropic material, in which the strength and thus the loading capacity depends on the position and direction of the carbon fibers. “With our process, we can lay out fibers in any direction required,” explains Wagner.
Another advantage of the process is that the components produced can be subsequently processed via honing, he says. The components then have an even, precise surface quality like that of classically produced steel components. “We can process piston rods in a way that makes them suitable for hydraulic cylinders,” Wagner explains. “This is thought to be unique in the world.”
The reaction from potential users has been mixed. While some remain to be convinced by Hänchen, others are already open to the idea despite the costs still being quite high - especially when CFRPs enable totally different solutions to steel and other metallic materials. “The anisotropic material requires us to think outside the box,” Bässler points out. “Some shapes work, others don’t.” Hänchen initially started with its core business, hydraulic drives. Today, the manufacturer uses the expertise it has gained for other components, such as rods and pipes. These are produced from CFRP not just because of the lightweight construction, but also because of other properties such as resistance to corrosion.
Software for greater efficiency
Altair Engineering GmbH from Böblingen plays an important and special role within the VDMA WG. “We want our software to give new impetus to our customers’ product development process, so that they can make the most of the potential of hybrid lightweight construction efficiently,” explains Frank Ehrhart, Technical Consultant at the Munich site.
“Part of the VDMA Hybrid Lightweight Technologies working group’s role is to find partners who will further develop the requirements of mechanical engineering together with us, in line with the ‘simulation-driven innovation’ approach.” In order to gain specific details for the design, Altair uses simulation methods that go beyond virtually structure testing. For topology optimization, for example, this might be information on where material is needed and where it is not.
Altair’s software also helps when designing fiber composites, such as when the goal is to find out the direction in which the fibers need to be laid out. The company also has a product design team that uses its engineering expertise to support customers when using new technology in the numerical design process. This ranges from developing global structures and architectures with the best mix of materials (multi-material design) to designing individual components and the best possible design of structures for 3D printing. “Asimulation-driven development process is the key to every lightweight construction material or process, so that the potential of the lightweight construction can be fully realized. Load-specific design plays an especially crucial role,” knows Ehrhart.