UK firm 3D-prints first metal mountain bike frame

British bicycle company, Empire Cycles, has developed what the company says is the first fully 3D-printed titanium mountain bike frame. Using a combination of Altair Engineering’s solidThinking Inspire software and Renishaw’s AM250 laser sintering AM system, the UK-based manufacturer says it has created a design that is not only stronger than a similar aluminium allow frame but also 33 percent lighter.

The company started with Altair’s topological optimization software, which iteratively “evolves” an initial CAD model by progressively stripping away material while still maintaining target stress and strength parameters. Such optimizations, while creating functional designs using less material, also typically result in organic shapes that can be difficult or expensive to manufacture conventionally.

Partnering with Renishaw, Empire was able to leverage the additive process’ advantages, including blending complex shapes and filling hollow structures with internal strengthening features, while eliminating the need for expensive tooling.

Given the AM250’s 12-inch build height, the frame was printed in smaller interlocking parts. The 3D-printer’s high-powered fiber laser produced fully dense metal parts direct from 3D CAD data in thicknesses ranging from 20 to 100 microns, using a range of fine metal powders. The parts were then bonded using adhesive from Mouldlife, which was tested by technical specialists at 3M test facilities.

The result, says the company, showed a significant reduction in weight. The original aluminium alloy seat post bracket, for example, fell from 12 oz. to 7 oz. for the hollow titanium version, a weight savings of 44 percent. Similarly, the 3D-printed titanium bike frame weighted in at 3.1 lbs. compared to 4.6 lbs. for the original aluminium frame, a 33 percent weight savings.

The lighter weight is significant considering that titanium alloys are typically denser than aluminium alloys. In addition, titanium has an Ultimate Tensile Strength (UTS) of more than 900 MPa, when processed using additive manufacturing. Combined with the AM process’ near perfect densities –- greater than 99.7 percent — the 3D printed parts performed better than those casted. For example, the seat post bracket was tested using the mountain bike standard EN 14766, and it withstood 50,000 cycles of 270 lb ft (1200 N). Testing continued to six times the standard without failure.

Empire and Renishaw plan to continue testing the completed bicycle frame in the laboratory, using Bureau Veritas UK, and in the field, using portable sensors in partnership with Swansea University.
www.empire-cycles.com
www.renishaw.com
www.altair.com