KraussMaffei (Munich, Germany) has developed FiberForm, a process for injection molding long fibers in polypropylene (PP) in quantities sufficient to reduce part weight by as much as 50% compared to components made with a short fiber-reinforced polyamide. The precise metering of the PP long glass fiber content is mainly the result of the use of special gravimetric metering modules, which had previously only been used in extrusion. A highly concentrated PP/long fiber granulate with 60% fiber content and equal parts polymer dilution (from PP) are metered and processed into plasticizing screws using two dosing units. Metering such high concentrates requires special material handling due to the complex flow properties present. By using the C-Flex M Walkwand feeder from Motan-Colortronic, uniform mass flow for this granulate type is said to be possible for the first time. KraussMaffei notes that with this system, fluctuations when setting the fiber content can be significantly reduced compared to conventional mixing concepts. KraussMaffei also reports that the FiberForm process can be combined with inline thermoforming of semifinished composite parts to provide injection overmolding capability.
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