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Bikes Go 3D Printing

Bikes have been and are a huge part of my life. From the moment I first learned how to ride my bike, I discovered a freedom of movement that still provides the same rush today as it did back then. This passion continues as I ride my mountain or road bike every chance I get.

That being said, it’s only natural that I write about how one passion: bicycling, is being influenced by my other passions: design and 3D printing. As we know, 3D printing now finds itself in almost every manufacturing process across industrial, commercial and consumer products.

Over the past several years a handful of new bicycle brands have emerged that use 3D printing or ‘additive manufacturing’ as a core methodology in their production process. Sturdy, Huhn, Kingdom and Atherton are among these new brands successfully incorporating 3D printed components in the bikes they sell to their customers.

Moorhuhn 29" titanium mountain bike - image via Huhn

Benefits
Customization is the primary reason bike companies leverage 3D printing. Customization when it comes to a creating a bespoke bike fit for a particular customer via specific tube lengths and geometry and for creating unique parts that would be impossible otherwise to make via traditional processes such as forging or CNC milling.

3D printed parts are designed to minimize weight. These parts can be hollow where appropriate and can feature internal ribbing or other structures that increase stiffness and strength. As mentioned above, 3D printing allows for unlimited freedom in creating complex, freeform shapes that could not be machined or made by using conventional means.

The use of 3D printing in bike frame manufacture creates the opportunity for more sophisticated design integration and refinement that ultimately yields a more precisely engineered bike. A bike that is in most cases lighter and better performing than its conventional counterpart.

Process
The two primary materials used in bike 3D printing are carbon fiber and titanium. Both of these materials have a long, proven history in the bicycle world and are considered to be the most desired materials when it comes to building bike frames. Steel can also be 3D printed but most bike brands in this space prefer to take advantage of the excellent properties that both carbon fiber and titanium offer i.e. strength, lightweight, stiffness, anti-corrosion etc.

Sturdy, Huhn and Kingdom are among the few key brands that focus on all titanium bikes. Sturdy creates exquisite road bikes in the UK while Huhn and Kingdom offer cutting edge mountain bikes designed in Germany and Denmark respectively.

The main premise when it comes to 3D printing bike parts whether using using carbon fiber, titanium or steel is the same. Typically the main tubes - top tube, seat tube, down tube, seat and chain stays are joined by 3D printed lugs.

Lugs are the parts that connect these various tube components resulting in a completed bike frame. A bikes head tube essentially functions as a lug and is usually printed as well as the terminal ‘dropouts' at the ends of tubes. Credit goes to Ralf Hollies of Huhn for first printing titanium lugs for his beautiful VRZ 2 custom track bike back in 2011.

Joining all the frame components is done via conventional TIG welding for metals and bonding (gluing) for carbon fiber or mixed material applications.

printed titanium lug - image via Huhn

VRRZ 2 by Ralf Hollies - image via Huhn

titanium lug - image via Sturdy

titanium dropout - image via Sturdy

There are two approaches to 3D printing titanium: SLM (Selective Laser Melting) and EBM (Electron Beam Melting). In SLM, a high power laser melts a very thin layer of titanium powder effectively fusing the metal particles together at the atomic level. These layers are vertically built up until a fully formed 3D component is made. EBM is a very similar process, except an electron beam is used in a vacuum chamber instead of a laser. Noted advantages of EBM are stronger, denser parts, a higher yield and the ability to print significantly more complex geometries.

In general it takes a metal 3D printer anywhere from 16 to 20 hours hours to make a lug set for a single bike, laying down roughly 3500 layers of titanium powder per lug. After printing, lugs are removed from the build plate and heat treated to increase strength. The last step in the process involves cutting threads, milling out seats for bearings, sand blasting to smooth out rough surfaces and hand finishing/polishing to finalize. All the brands mentioned above employ both SLM and EBM technologies in the production of their frame components.

Atherton, an Australian mountain bike brand does things a little bit differently. Atherton’s custom creations are made up of both titanium and carbon fiber components. Like the other brands, Atherton 3D prints it’s lugs, head tubes, dropouts etc. but uses custom designed round or oval carbon fiber tubes in the construction of its bike frames in lieu of titanium tubes.

To assemble its bikes Atherton uses an industrial grade adhesive that bonds all the various frame components together. To achieve the perfect fit and alignment, a proprietary jig is used to keep all tubes and lugs in place during the bonding process. When the adhesive cures, the frame is painted then assembled, quality control checked and finally shipped to the customer.

What's Next
3D printing bike components is still a relatively new methodology in the industry. Apart from printing connective frame components, brands are also now experimenting with other bike parts and accessories.

Sturdy for example also prints its own titanium fork, seat post, cranks and stem. Global brands such as Specialized and Fizik both offer a 3D printed saddle comprised of a polymer based lattice design intended to reduce weight and increase comfort.

printed titanium crank - image via Sturdy

Arevo a 3D printing startup has released a unibody bike, the Superstrata where the frame is remarkably printed as one piece of carbon fiber.

As the technology improves and becomes more accessible bike brands will increasingly employ 3D printing in their manufacturing processes. My guess is that eventually all traditional production techniques of forging, metal tube extrusion, welding of joints etc. will be replaced by 3D printing.

Like in the Arevo model, all bike frames will be simply printed as a singular piece of titanium, carbon fiber or steel. Customization will not only address physical fit but also aesthetic considerations ranging from color to tube shape or surface decoration i.e. customer name, slogan, pattern etc.

Bicycle design will continue to evolve as 3D printing will help designers break free from the limitations of conventional production and enable them to truly push boundaries and apply their creative problem solving in completely new ways.

I would like to thank Tom Sturdy of Sturdy Cycles and Ralf Holleis of Huhn Cycles for generously sharing their product images with me.

Thank you, until next time! - Andreu O.

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