News: British bicycle brand Empire Cycles has collaborated with additive manufacturing company Renishaw to build the world’s first 3D printed metal bicycle frame.
Thanks to a 3D printer developed by Renishaw print metal parts, Empire Cycles created a titanium alloy frame that is over a third lighter than a traditional frame, increasing design flexibility while reducing production costs.
“The main advantage for Empire Cycles is the performance benefits that this construction method imparts,” says the brand, which first approached Renishaw with its design.
“As no tooling is required, continuous design improvements can be made easily, and since component cost is based on volume, not complexity, some very lightweight parts will be possible at minimal cost.”
According to the brand, 3D printing makes the frame of the MX-6 Evo bike lighter without losing strength by using topology optimization – the process by which material is removed from low-stress areas until the design is optimized for the load carrier. Using as little material as possible means the frame is as light as possible.
Even though titanium is denser than the aluminum alloys Empire Cycles normally uses, topology optimization allows the weight of the bike to be reduced to 1400 grams, which is 33% less than the previous 2100 grams.
While some carbon fiber bikes are lighter, Empire Cycles claims this frame is sturdier. “The durability of carbon fiber cannot be compared to that of a metal bike,” said Chris Williams, general manager of Empire Cycles.
“They are great for road bikes, but when you start to rush down a mountain you risk damaging the frame. I over-engineer my bikes to make sure there are no complaints to the title of the guarantee,” he added.
Here is a press release from Renishaw:
First 3D printed metal bike frame made by Renishaw for Empire Cycles
Renishaw, the UK’s only manufacturer of a metal-based additive manufacturing machine that prints metal parts, has collaborated with a leading UK bike design and manufacturing company to create the world’s first 3D printed metal bike frame in the world. Empire Cycles designed the MTB to take advantage of Renishaw’s additive manufacturing technology, allowing them to create a strong yet lightweight titanium frame through topology optimization – the new frame is around 33% lighter than the original. ‘original.
The frame was additively fabricated from titanium alloy in sections and glued together. This offers a number of advantages:
Freedom of design
» Fast iterations; flexibility to make design improvements through to production
» Possibility of making derived shapes by topological optimization (see overleaf)
» Ultimate customization and customization – create unique pieces as easily as production batches
» Complex shape with internal reinforcement features
» Hollow structures
» Built-in features, such as driver name
Performance, titanium alloy
» 44% lighter seatpost bracket than aluminum alloy version
» Extremely resistant – tested according to EN 14766
» Corrosion resistant and durable
What is its strength?
Titanium alloys have a high ultimate tensile strength (UTS) of over 900 MPa when processed using additive manufacturing and near-perfect densities of over 99.7% are achieved; it’s better than casting, and since any porosity is both small and spherical, it has little effect on strength.
The aim of the project is to produce a fully functional bicycle, so the seat post holder has been tested according to the EN 14766 mountain bike standard; it withstood 50,000 cycles of 1,200 N. Testing continued up to 6 times the standard without failure.
Testing of the finished bike frame will continue, both in the lab using Bureau Veritas UK and on the mountainside using wearable sensors in partnership with Swansea University.
What is topology optimization?
From the Greek word for place, “topo”, topology optimization software is the term given to programs that are used to determine the “logical place” for material – normally using iterative steps and finite element analysis. Material is removed from areas of low stress until an optimized design for the load bearing is developed. The resulting model is both light (due to the low volume) and strong. The historic challenge of manufacturing these shapes can now be overcome through additive manufacturing, allowing physical 3D models to be made.
How light is it?
Titanium alloys are denser than aluminum alloys, with relative densities of around 4 g/cm3 and 3 g/cm3 respectively. Therefore, the only way to make a titanium alloy version of a part lighter than its aluminum alloy counterpart is to significantly modify the design to remove any material that does not contribute to the overall strength of the part.
The stock aluminum alloy seatpost bracket weighs 360g and the hollow titanium version weighs 200g, a weight saving of 44%. This is only the first iteration; with further analysis and testing, it could be further reduced.
The stock bike frame weighs 2100g. Redesigned to use additive manufacturing, the weight drops to 1400g, a weight saving of 33%.