Fiber composite technology has proven very promising in the production of composite components. The rejects of materials are significantly reduced in this production process. The Broetje-Automation Group has developed the "Staxx Kompakt 1700", a machining center for large-scale production in the automotive industry, with which components can be manufactured inexpensively according to this process. At the heart of this system is an axle portal that supports the Indunorm Bewegungstechnik custom designed. Most important requirement: The system is very robust and still lightweight.
The Staxx Compact 1700 in action
"Automotive engineering is increasingly relying on fiber composite materials," says Dr. Christian Boge, Head of Composites Automation at BA Composites GmbH based in Grenzach-Wyhlen in the district of Lörrach in Baden-Württemberg, a subsidiary of the Broetje-Automation Group. "Lightweight construction is becoming increasingly important in this industry, ensuring energy savings and therefore lower CO2Emissions. "In particular, components are manufactured from the body structure. Moving parts that weigh less, also allow further cost reductions. Because bearing and load-bearing elements can also be made lighter by the reduced dynamic loads - downsizing is the keyword here. "We can make complex shaped parts that are still very strong," he says.
Broetje-Automation has expanded its technology base with the subsidiary in order to react to the developments and increasing demands of the market. BA Composites manufactures machines and equipment that enable users to produce composite components using Automated Fiber Placement (AFP) and the Tape Laying Process (ATL). "The machining centers are both standardized and tailor-made solutions, which we implement in close cooperation with our customers," explains Dr. med. Boge (right picture).
Both technologies have been successful in the production of composite structures in the aerospace industry. "However, no breakthrough is in sight for mass production in the automotive industry," Boge. "And especially in this industry, we see great potential - especially for the AFP process. With the Staxx Compact 1700, the engineers have now developed a future-oriented four-axis machining center that enables fiber laying technology economically. "
Avoid rejectsDuring development, it was important to combine the advantages of fiber laying with the requirements of the automotive industry. This means that the level of production costs is often decisive for vehicle manufacturers when awarding orders. "With our machining center, the user can process inexpensive carbon fiber materials. Our plant largely avoids waste and rejects. An integrated air conditioning technology allows the installation in normal production halls ", describes Dr. med. Boge.
The machining center can also be combined with automation technologies such as parts or pallet handling. "The Staxx Compact 1700 thus combines this sophisticated technology with a solid process and a high degree of automation for maximum throughput," explains Dr. med. Boge. A key component in the machine is a gantry type two-axis YZ gantry gantry for moving the fiber lay head. For this purpose, the company relies on a solution from Indunorm Bewegungstechnik GmbH with its headquarters in Duisburg and a new location in Stuttgart.
Very stiff and weight optimized"We got to know each other at the Metav in Düsseldorf," recalls Folko Ridder, Technical Director at Indunorm, who has held the first talks. "The machining center had to be very rigid due to the high static and dynamic loads," adds Axel Joostberens of Indunorm (picture left) and responsible for the projecting of the axle system into the system. "It took a sophisticated axle gantry, which is not only extremely rigid but also lightweight, to optimize the weight of the entire machine."
Toothed belt-driven linear axes with ball chain guides type SHS from THK are used. Indunorm is the largest distribution partner for linear movement technology of this brand in Europe. The axes used are designed for performance, efficiency and, in particular, refinement. The rows of balls are arranged in a contact angle of 45 degrees. Therefore, this series can absorb forces evenly from all directions. Due to the THK-specific X arrangement of the four circular arc grooves with two-point contact, the LM block can compensate for assembly errors even under prestress and implement precise, smooth-running linear movements.
"We determined the loads for the axle gantry beforehand from the moving masses, the center of gravity and the dynamic characteristics," says Rainer Graf, designer of the axle system at Indunorm, describing the procedure. The view was always on an optimal relationship between stiffness and weight. With the help of the finite element method, the engineers were able to predict, evaluate and optimize the structural behavior especially of the angle bracket with regard to its mechanics. Aluminum profiles would not have met the requirements or the structure would have become too massive. "We therefore rely on cleverly designed, non-machined sheet metal structures in which the linear guide elements and the components for the drive technology are integrated, mounted and aligned," explains Graf.
A high-quality powder coating of the sheet metal parts ensures long-term corrosion protection of the components. Taking into account the specifications and specifications drawn up in advance, the required interfaces were also defined during the project phase and correspondingly reconstructed. The engineers from Indunorm have also designed the servomotors required for driving the linear axes with planetary gearboxes. "After the construction and alignment of the two-axis system, the linearities, angularities and positioning errors in the room were also measured. We have graphically prepared the corresponding measurement results and provided them for the documentation, "says Dietmar Heim, Managing Director of the Indunorm location in Stuttgart.
Focus on maximum flexibilityThe Staxx Compact 1700 manufactures the components in the form of carbon fiber stacks. "After starting the system, the fibers are guided in narrow strips from a coil store over coated rollers into the laying head," says the development manager describing the system. There, the material is tempered. The laying head then leads the fiber ribbons over a negative tool and presses it to its base. Blades now cut off every single ribbon. This reduces waste waste to a minimum. The desired component thickness is created by the multiple deposition of such individual layers, each with adjustable fiber orientation. "The advantage is that with this procedure local reinforcements are also possible within a component", says dr. Boge. As a result, the AFP offers additional possibilities for providing targeted local adaptations to geometric boundary conditions or structure-mechanical specifications.
So that the user is flexible in the production of the components, BA Composites has equipped the machining center with a further X-axis linear axis and a turntable. This construction handles pallets that are equipped with the components. "Here we use a rack drive and THK linear guideways," explains Axel Joostberens. "We designed and delivered these components and integrated them constructively into the base frame."
Intensive cooperation was worthwhileThe rapid implementation of this project - from the establishment of contact to the delivery of the customer-specific axis portal in September 2014 - was only possible thanks to the close and trusting cooperation. In Paris, BA Composites convinced the jury of the JEC Europe 2015 Innovation Award with the Staxx Compact 1700 and won the prize in the "Process" category.