The new "black gold"
Carbon fibers are especially lightweight, strong and rigid. These properties make plastic components reinforced with carbon fiber an ideal candidate for reducing the fuel consumption of automobiles and extending the range of electric vehicles. So far, the high cost of manufacturing carbon fiber components has stood in the way of more widespread use. This is about to change, however, thanks to a new method developed by LIBA that significantly reduces the cost of production.
As a raw material, carbon fiber has earned a reputation as the new "black gold". It is expensive, and processing it into sheets of fabric and finally into components made of carbon fiber reinforced plastic (CFRP) is a time consuming process involving a number of manual steps. CFRP parts have therefore generally been reserved for applications where a high strength-to-weight ratio takes priority over cost. Primary areas of application currently include Formula 1 race cars, speed boats, rotor blades for especially large wind turbines, satellite panels and medical equipment.
Yet there is a fundamental shift transforming the market. Advancements across every stage of the fiber composite production chain over the past few years are very promising. There are many indications that the "new black gold" will usher in an age of lightweight construction and redefine the future of transportation and logistics.
Exceptionally efficient production
The pace of these developments is being set by innovative systems manufacturers such as renowned textile specialist LIBA Maschinenfabrik. LIBA's long tradition of proven machine technology served as the foundation for its new Copcentra MAX 5 CNC machine, which provides remarkably efficient production of multi-axial carbon fiber fabric.
The machine is fed rovings of splayed carbon fiber tape. These have either been produced directly on the machine or supplied from elsewhere. The tape is laid out in parallel strips to form layers between 50 and 150 inches wide, with each layer oriented in a different direction (multi-axial). The strips of tape are held at each end by clamps mounted on chains. These transport the fabric throughout the approximately 35 meter long system.
Once the fabric has reached up to seven layers, it is passed through a warping station, where the layers are stitch-bonded with warp thread. Still held in place by the clamps, the fabric is transported for a buffer distance through the system to prevent later steps from disturbing the stitching process. Then the edges of the fabric are trimmed, the fabric is rolled up and the waste material still held by the clamps is vacuumed away.
High quality with high productivity
The fact that the Copcentra MAX 5 CNC works with strips of tape cut precisely to length plays an important role in its unparalleled efficiency. Other machines typically run a single continuous tape, which invariably leads to excess waste around the clamps that needs to be trimmed off later. LIBA's solution handles the carbon fiber like the valuable raw material it is, and consequently utilizes it much more economically than conventional systems.
The manufacture of carbon fiber fabric demands high productivity, a safe production process and a consistently high level of quality. At the same time, large-scale production lines must also be extremely flexible in order to accommodate new or specific requirements.
To establish this level of flexibility, LIBA developed a broad palate of machine modules. Among them are online and offline systems for producing carbon tape, guide bar controllers with linear motors and modules for preparing zero-degree layers, coating and bonding modules and more.
"Our modular machines can be combined in virtually any arrangement to create systems that are tailored specifically to the unique needs of our customers," explains Rainer Seuß, LIBA's expert on multi-axial technology. His colleague, Wolfgang Jahn, who is responsible for control technology adds, with visible pride: "We're able to implement customer-specific control solutions in a matter of only a few man-hours."
This flexibility and speed is all the more impressive considering that even the basic model of the Copcentra MAX 5 CNC incorporates 35 real axes and 10 virtual axes. Yet LIBA has already delivered systems with various auxiliary modules that brought the total to 65 real axes and 20 virtual axes. LIBA attributes its ability to engineer the control system so rapidly in spite of such complexity to the completely integrated automation solution from B&R.
"Since we upgraded the Copcentra MAX 5 CNC to a B&R automation solution, we now have the same drive and control architecture throughout every machine we offer, all based on standard B&R products. We use the Power Panel PP420 as our control and HMI platform, ACOPOSmulti drives and X20 I/O modules, as well as B&R's integrated safety technology," reports Jan Märtin, head of design and development at LIBA.
1000 variants with a single software project
The trick to LIBA's efficiency and flexibility is that the same software project runs on every machine. The system and its automation components such as axes, I/O modules and safety technology are configured at runtime. The necessary system data is provided in XML files. "This is what allows us to manage the control solutions for our 60 machines and 1000 variants, some of which have very significant differences in their configurations," reasons Jahn.
LIBA's approach has clear advantages for system operators as well: To implement an update, all they need to do is upload the new software project to the controller – the configuration file remains unchanged. All the updates take effect automatically the next time the machine is started. Regardless of which specific machines are being used, all customers benefit immediately and effortlessly from LIBA's latest software developments.
"Its just as simple to modify machines in the field," promises Jahn. "Use any text editor to modify the configuration file to match the new system configuration – then simply restart the machine and you're done. There's absolutely no programming required."
Complex synchronized movements with absolute precision
The Copcentra MAX 5 CNC demands quite a lot from its control and drive technology. "The controller must be able to maintain high-precision, synchronous links between a large number of axes in order to implement intricate movement sequences," explains Seuß. "This is essential to creating a precise and efficient process that is able to achieve the desired levels of production speed and quality." To make all this possible, the axes must communicate with each other at high speeds, and the path curve control needs to know their exact positions at all times.
"With the combination of ACOPOSmulti drive technology and the fast real-time communication bus POWERLINK, we have found an optimal solution. It combines superior dynamic properties with excellent precision, and offers us many other advantages that we didn't have before switching to B&R," adds Jahn.
For example, LIBA uses a common DC bus with regenerative power to ensure an absolutely synchronous shutdown, even in the event of a power failure. "In many countries we supply, power failures are almost a daily occurrence. With our old technology, getting the machine up and running again after each outage was a time-consuming process," explains Märtin. "Now we're able to utilize the existing kinetic energy to ensure a controlled shutdown, which leaves the system ready to be restarted immediately."
For cases where the machine doesn't store sufficient energy – because the axes are running too slowly or the guide bar controllers use linear motors – LIBA has developed a kinetic buffer axis where an induction motor with a flywheel mass is brought to a high speed. This buffer axis is connected to the same DC bus as the other drives, so its movement serves as an auxiliary source of energy in the system. This energy can be used to power a controlled shutdown when necessary.
Together with all the other cutting-edge features, this helps the Copcentra MAX 5 CNC produce carbon fiber fabric with outstanding efficiency. The path is now cleared for widespread use of carbon fibers to shape the future of the transportation and logistics industries.