The announcement that Empire Cycles Ltd. in cooperation with Renishaw has created the first MX6-R mountain bike to be constructed using a 3-D printer once again provides proof of the ingenuity of modern manufacturing engineers and designers. The creation of a complete titanium frame in a generative manufacturing process using 3-D printing is an important milestone, not only for the technology itself, but also for the world of mountain bikes.
But this ambitious project also required the support of a number of conventional techniques to bring it to a successful conclusion. Thanks to extensive input from its machine manufacturer Merlin Engineering and WNT, its partner for machining tools, Empire Cycles was able to rise up to this demanding challenge with success.
The use of generative manufacturing processes such as 3-D printing has seen tremendous progress, but precision machining remains absolutely necessary to achieve the tight tolerances required for the bike's safety in individual areas of the frame.
“Machining these areas was crucial to the success of the project, because the 3-D printing is not able to achieve the required tolerances and finishes. Honestly, without the metal cutting knowledge of WNT and Merlin, this mountain bike wouldn't exist”, says Chris Williams, Managing Director of Empire Cycles.
Additive manufacturing and 3-D printing both posed their very own special challenges to the production process, especially when it came to processing the frame components, where a reduction in the bike's weight was targeted by using less material. This meant that the remaining material for machining was quite minimal, in some places only 2 mm thick.
For Scott Bradley, application engineer at WNT, this meant rethinking the processing strategies to be used in this project: “Conventional titanium machining strategies tell us that climb milling is the optimal solution to obtaining a hard surface on the material.
In preparation for this project, the initial tests we performed indicated that conventional milling was the best option for these parts, in terms of the depth of cut, clamping and the thin walls of the metal.
To maximise the processing power, WNT opted to use its A 2011 indexable milling cutter that had been developed as an alternative to solid carbide cutters, with a diameter between 16 and 40 mm. [The series extends to 80 mm diameter.]
With their soft cutting and radial force compensation, they are the ideal solution for milling thin-walled components on machines with high cutting speed and low power.
For the processing of the control head and the frame at Merlin Engineering, HCF 6240 indexable inserts from WNT with the extra hard Dragonskin coating were chosen because they were specifically designed for the machining of titanium and run smoothly and quietly. For the bottom bracket, however, indexable inserts were used that were developed for the machining of super-alloys. After processing, the frame parts were connected and the mountain bike assembled with wheels, hubs, brakes, chain rings and pedals supplied by Hope Technology.
“For many years we have been working closely with Empire Cycles and WNT provided support in processing the frame of the original MX-6 cross country bike from solid aluminium. The development of the world's first high-performance mountain bike frame with 3-D printing is a significant milestone in production. However, it is also reassuring that machining is still critical to the completion of the final product and will make this process possible in practice”, says Claude Sun, Managing Director, WNT Germany.