A specialized Dutch injection molder is using fusible core technology to replace aluminum aircraft components at significant weight and cost savings. Among the announced projects, fuel housings, pumps and filters are molded in carbon fiber reinforced polyetheretherketone (PEEK).
Egmond Plastic of Alkmaar, the Netherlands, molds parts with fusible core technology, which dates to 1968 but was not widely used until applied to automotive intake manifolds in the 1980s. Applications in aircraft are gaining speed as OEMs drive out weight to improve fuel economies and extend aircraft range.
In a press release issued by Victrex, Richard Brandwijk, managing director at Egmond Plastic, says: “Our technology, in combination with carbon fiber-reinforced Victrex PEEK polymer, delivers numerous benefits. These include cost reduction, enhanced manufacturing speed, and weight reduction leading to improved fuel efficiency and reduced CO2 emissions. Along with part consolidation, this exceptional technology and material combination enables the design of very complex parts, beyond the capabilities of standard injection molding and metal processes.”
He said that cost savings of more than 30 percent and weight savings of up to 50 percent can be achieved compared to existing metal designs.
Fuel housings for aerospace applications have complex inner geometries that are not moldable using conventional injection molding technology. Fusible-core technology enables molding of complex hollow housings, manifolds, and pipes
According to Victrex, reinforced PEEK has superior fatigue performance when compared to aluminum while meeting all the engineering requirements, including stiffness, effective flame, smoke and toxicity (FST) performance, and resistance to aggressive chemicals, including resistance to jet fuel and Skydrol hydraulic fluid. Parts be as large as 30 cm x 30 cm x 40 cm (11.8 in x 11.8 in x 15.8 in), and typically the process is used for production runs of up to 2,000 parts.
The technology is also used in a filter housing supplied by PTI for the Boeing 787. It replaced a housing made of two aluminum components.
Egmond’s fusible-core technology has also been used in a fuel pump for the Eurofighter Typhoon jet fighter for more than 20 years.
Egmond also molds parts from Ultem polyetherimide (PEI) for aircraft applications.
The disadvantage of the fusible core technology is significant upfront costs for tooling. As a result, economics require production runs of at least a few hundred parts, depending on the cost to produce the part through conventional methods. Production times are not generally significant because of the long lead times to build new aircraft.
One of the first U.S. patents for fusible core was awarded to Dunlop in 1981 for racket frames. Solvay was awarded a patent for the technology in 1993. The process is also called lost core molding and was widely commercialized to produce automotive intake manifolds from glass-filled polyamide.
The process involves these steps: production of a core, inserting the core into the mold, filling the mold, removal of the molded part and then melting out the core. As a result undercuts can be made that are not possible in standard molding.
Egmond Plastic, which makes its own molds, operates injection molding machines with clamping forces ranging from 150 to 800 metric tons.