Hybrid components of fiber-reinforced plastic and metal are formed and back-injected in a single step in a German automotive lightweighting research project called LEIKA.
Partners in the German government-funded project include KraussMaffei and the Institute for Lightweight Engineering and Polymer Technology at Dresden University of Technology.
“The resulting process and structure quality, together with the achieved cycle times of significantly less than two minutes, supports the potential of such hybridization on both the material and production end,” says Martin Würtele, director of injection molding technology development at KraussMaffei.
The system is being used to make a hybrid floor structure for electric vehicles in a development project. Metallic outer layers of steel are combined with a core of CFRP. “The first test results are excellent,” says Würtele. “The mass is reduced by 25 percent compared to an all-metal lightweight construction solution. Simultaneously, it was possible to demonstrate comparable performance under the most important load conditions with regard to stiffness and crash situations for components with significantly lower mass.”
Plastics can be used for compression in the mold or reinforcement for local areas in the component. Aspects include integration of a flat sheet die as well as a conveyor belt with an insertion robot.
“The new test system lets us project a large number of incredibly varied processes on a single system. This lets us offer significant added value to our partners from the automotive industry,” says Michael Krahl, project manager of LEIKA.
One of the goals is flexibility.
KraussMaffei designed a bolt-on unit of reduced height that is integrated with the production line, including a press, infrared oven, robot and conveyor belt. KM says that the unit is capable of both injection molding and extrusion, portioning the injection volume in the process.
Up to five areas can be reinforced locally in one cycle.
Integration of the conveyor belt makes it possible to deposit portions of plastic. “The speed of the conveyor belt results directly from the process parameters, such as injection speed or throughput. This is a clear advantage for the Institute for Lightweight Engineering and Polymer Technology because there is no longer any need to set the conveyor belt manually beforehand and there is no discharged melt. In the event of a change in discharge speed, the conveyor belt speed adapts automatically and with deliberate control,” says Würtele.
The unit has newly developed software that is completely integrated into the production line electrically.
KM also says the system has high shot weight consistency with an SP 12000 injection unit with direct drive. The motors for plasticizing and injection are arranged in a series and directly flange-mounted on the screw, making it possible to prevent transverse forces opposing the flow of force.