Injection overmolding of unidirectional fibers and preforms is an attractive process for many good reasons. It’s fast, consistent and repeatable, and it can be performed with a machine that is relatively easy to acquire, program and control. Injection molding’s disadvantage, however, is it requires tooling that is typically very expensive — certainly more expensive than tools for compression molding. Further, overmolding requires that the composite be encapsulated within the tool, and if it’s a larger part, that means larger tooling. Add it all up and the cost of composites overmolding can exceed its benefits.
Robert Davies, CEO of Fibrtec (Atlanta, Texas, U.S.), has developed an interesting solution to this particular overmolding dilemma. His system uses a hybrid injection/compression overmolding process of his own design to combine smaller injection molded parts or inserts within a larger compression molded part. In essence, the approach flips the script on the overmolding strategy. Rather than injection mold around a composite preform, Davies’ solution involves compression molding around an injection molded part.
“What [Fibrtec] decided to do was injection mold the bosses, features, ribs and those kinds of things, and position them in place into the same compression molding tool that the laminate was going to be consolidated in,” says Mike Favaloro, president and CEO of composites consultancy CompositeTechs LLC (Amesbury, Mass., U.S.), who spoke about the process at the Composites Overmolding conference in Novi, Mich., U.S., in 2018.
“Since you have to consolidate the laminate anyway, why not consolidate the laminate with the injection molded parts in place?” he adds.
With Fibrtec’s process, ribs, bosses and similar features are injection molded off-line using thermoplastic resins, lower cost tooling and conventional injection molding machines. The injection molded insert is then robotically placed in a compression mold with a preform.
Related Content
Plant tour: Arris Composites, Berkeley, Calif., U.S.
The creator of Additive Molding is leveraging automation and thermoplastics to provide high-volume, high-quality, sustainable composites manufacturing services.
Read MoreJEC World 2023 highlights: Innovative prepregs, bio-resins, automation, business development
CW’s Jeff Sloan checks in with JEC innovations from Solvay, A&P, Nikkiso, Voith, Hexcel, KraussMaffei, FILL, Web Industries, Sicomin, Bakelite Synthetics, Westlake Epoxy and Reliance Industries.
Read MoreThermoset-thermoplastic joining, natural fibers enable sustainability-focused brake cover
Award-winning motorcycle brake disc cover showcases potential for KTM Technologies’ Conexus joining technology and flax fiber composites.
Read MoreLow-void, large-scale, high-volume 3D-printed composites
Among its many composites-related projects, Oak Ridge National Laboratory recently installed its first AMCM test cell, combining extrusion with compression molding for fast, low-void, low-porosity thermoplastic composite parts.
Read MoreRead Next
Overmolded hybrid parts open new composites markets
A process that combines continuous carbon fiber-reinforced PAEK with chopped fiber/PEEK overmolding is making inroads in the aerospace market. Parts that previously could not be produced cost-effectively from composites can now be made at less cost than their metal counterparts.
Read MoreCW’s 2024 Top Shops survey offers new approach to benchmarking
Respondents that complete the survey by April 30, 2024, have the chance to be recognized as an honoree.
Read MoreFrom the CW Archives: The tale of the thermoplastic cryotank
In 2006, guest columnist Bob Hartunian related the story of his efforts two decades prior, while at McDonnell Douglas, to develop a thermoplastic composite crytank for hydrogen storage. He learned a lot of lessons.
Read More