3D-Printed Carbon Preforms Are Overmolded In New Technology

Carbon fiber 3D printing and injection molding are integrated in a novel invention from a fast-rising Massachusetts technology startup. The concept targets small, complex parts now made from aluminum and other metals. Applications can range from under-the-hood automotive to jigs and fixtures.

In the concept developed by Markforged, which was formed just four years ago, continuous carbon fiber preforms are 3D printed and are then overmolded with thermoplastic to make strong net-shape parts at a potentially lower cost, lighter weight, and faster production times.

The invention is outlined in a patent application by Markforged founder and CEO Greg Mark that was published yesterday.

Markforged uses it own 3D printer with its patented continuous fiber filament (CFF) technology and its proprietary Eiger software that automatically creates a fiber pattern for “maximum” strength within the 3D print file. Markforged also manufactures continuous fiberglass; Kevlar; and high-strength, high-temperature fiberglass for its printers.

Reinforced plastic parts currently made via injection molding use discontinuous fiber, primarily glass. Use of preforms is limited to low-pressure molding processes, which primarily use thermoset materials.

The new Markforge invention allows high-volume production of very strong parts with a quality surface finish. The pressure of injection forms the preform into a final shape and can be used to dissolve removable thermoplastic preform support structures. The support preform is injection molded as a honeycombed structure with a contiguous outer surface that can be used as a winding substrate. The patent application indicates different ways the support material can be removed.

Two or more continuous fiber reinforcement preforms may be bonded to one another before being placed in the mold. The fiber deposition is an additively deposited thermoplastic continuous fiber reinforced prepreg tape having a width at least three times its height. The reinforcement volume is less than 20 percent of the entire reinforced molding.

The entry price for the company’s Onyx One CFF printer is $3,500. The Mark Two, at a price of $13,500, delivers metal-strength carbon composites for 10 times the strength of plastics, according to the company.  The fiber is in a polyamide matrix. The Mark X industrial-scale printer ($69,000) launched in October of 2016. It features in-process part inspection using a laser micrometer, a larger build size and other precision capabilities.

“Our belief is that every designer and engineer should have broad access to strong, elegant parts from a reliable printer they love to use.” says Greg Mark. “With the Onyx One, we provide our customers with superior parts in a seamless integrated system of hardware, material and software to deliver a quality experience at an accessible price point.”


About Doug Smock

Former Chief Editor at Plastics World and Senior Technical Editor Design News
Additive manufacturing, Carbon Composites, Design, Insert Molding, North America, Reinforcing Material , ,

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