Carbon Fiber Bike Frame Made Possible with Robotic 3D Printing

Carbon-fiber-reinforced polymer offers the strength and light weight to compete with metal parts for many applications, but conventional processes for fabricating carbon fiber composites are labor-intensive and require long lead times for tooling. 3D printing with carbon fiber, however, offers a faster and easier alternative for manufacturing these parts, and can even enable designs not previously possible with carbon fiber composites.

A collaboration between robotic 3D printer developer Arevo, material supplier Hexcel and design firm Studio West illustrates these benefits through a project to develop a commuter bike with a 3D-printed carbon fiber frame. William “Bill” Stephens of Studio West created the simplified design for the bike, which was then optimized for the Arevo 3D printing process and manufactured using carbon fiber material from Hexcel.

The design and material chosen made the resulting frame strong enough that the team was able to remove a seat stay between the seat and the back wheel. This one-piece frame design would not have been possible to manufacture conventionally, but is a good fit for Arevo’s 3D printing technology. Called True3D, the process uses laser-based directed energy deposition (DED) to deposit thermoplastic carbon fiber towpreg (fibers bound with a thermoplastic resin). A robotic arm deposits the material in three axes, driven by Arevo-developed software algorithms. This deposition strategy allows for more precise orientation of the fibers, key to the final strength of the part. According to the company, the resulting parts are less than 1 percent porous and stronger than comparable parts printed in 2.5 axes.

To prepare the bike frame for 3D printing, the CAD file was imported into Arevo’s PathFinder software. This program uses part geometry and loading conditions to optimize carbon fiber orientation and placement, and also features Additive Finite Element Analysis (AFEA) algorithms, used to validate the bike design before printing.

The frame was 3D printed with Hexcel’s HexTow AS4 12K carbon fiber material, resulting in a tougher and less brittle construction compared to thermoset composite frames, the partners say. The bike was created with reduced development cost, as the frame required no tooling, and completed in less than 18 days. The collaborators say that future use of this process could reduce time to market for new products with carbon fiber parts, reduce inventory cost by enabling manufacturing on demand, and make it possible to customize bikes to the size of the rider.