Titanium is a low density and high strength, low weight material, perfect for bikes. But, the metal alloy is very expensive. Could a 3-d printed version lower the price of admission?
Renishaw, an additive manufacturing firm, joined forces with Empire Cycles to build the one-off titanium MX-6 Evo mountain bike. Empire already offers a production aluminum version of the MX-6.
The frame was built using an AM250 laser melting machine manufactured by Renishaw. In the build process, a high-power ytterbium fibre laser was used to selectively fuse together particles of a titanium alloy powder. Layers of those fused-together particles were built up one upon the other, to form the finished sections of the frame. Those sections were then bonded together using an adhesive.
Because titanium has a higher density than aluminum, less of it had to be used if Empire wanted a finished bike that was lighter than the stock model. To make that happen, topological optimization software was used – it structurally assessed computer models of each part of the frame, and determined where less material could be used without negatively affecting strength.
As a result, at a total of 3 lbs, the finished Evo frame weighs 33 percent less than its aluminum counterpart. When its seatpost bracket was tested, it exceeded the EN 14766 mountain bike strength standard by six times. The strength of the frame as a whole is still being tested.
So, how could this project lead to cheaper titanium frames? For one thing, in the laser melting process, there's no waste – all of the titanium alloy powder that isn't fused to make one frame can be reused in another, plus the topological optimization process ensures that less of it is needed in the first place. Additionally, no special machining has to be created or set up for specific frame designs, which would be the case with cast metal.
It should also be relatively simple to tweak frame designs as needed, or to add custom features to individual frames. And finally, it shouldn't be any more difficult to create components with complex shapes than those that are relatively basic.