Bespoke bike maker harnesses AM

Metal 3D printing helped process a bike part to a high level of consistency to meet customer demand.

Angel Cycle Works, a bike manufacturer based in Oleiros, Spain, asked Spanish 3D printing specialist Optimus3D to provide a metal additive manufacturing (AM) process that could produce a chainstay bracket component in a small series quantity to a uniform quality standard. A chainstay on a bike is the pair of frame tubes that joins the bottom bracket shell to the rear axle holders.

Optimus3D, headquartered in the Álava Technology Park in Vitoria-Gasteiz, Northern Spain, provides 3D printing services to businesses in a broad range of sectors, including aerospace, automotive, general industrial and medical. It offers end-to-end help, comprising component design, prototype and volume production, post-processing and metrology.

“Our expertise in metal additive manufacturing is due in no small measure to our in-depth knowledge of manufacturing and reverse engineering,” said Pablo Capellan, project leader at Optimus 3D. “It means we can more readily adapt a client’s requirements to the 3D printing process, making full use of the complete spectrum of AM’s capabilities.”

Angel Cycle Works is a bike frame builder and component maker that offers hand-made bespoke frames and components in titanium. It produces high performance bikes for road, gravel, mountain and cyclo-cross environments.Because it required a high-quality, high-strength component that relied primarily on hand-welding and small series production, Angel Cycle Works decided investigate the use of AM as an alternative and approached Optimus3D for a solution.

“The challenge for Angel Cycle Works in manufacturing the titanium chainstay bracket component by hand fundamentally relates to the source metal itself,” said Capellan. “It simply isn’t the easiest of materials to work with. Particularly when hand-welding, deformations in the component’s integrity can occur, and staying perfectly true to a three-dimensional CAD model can be really very hard.

“That said, even when it comes to the alternative AM process, whether it’s building a component by melting metal either in layers or by deposition along a path, titanium can still present challenges.”

Productivity focus

In order to produce the component in volume, maximising the productivity of the AM process was a a key aspect of the process for Optimus3D. Not only did the company need to guarantee the complete accuracy and reliability of the component, but it also needed to ensure that each build volume was yielding the maximum number of components, to make the process as cost-effective as possible.
Optimus3D proposed the use of its RenAM 500S single laser AM system. The 3D printer, developed by UK-based AM specialist Renishaw, based in the town of Wotton-under-Edge, was specifically designed for building metal components in a production environment using powder bed fusion (also called laser melting). It has a build volume which measures 250 mm x 250 mm x 350 mm.

Importantly for the Angel Cycle Works bicycle component, the Renishaw system’s inert manufacturing atmosphere (a vacuum filled with high purity argon gas) helps ensure a better quality build environment for all qualified metals, including titanium Ti6AI4V, the metal powder to be used in this project.

Considering the component’s structure and dimensions, building up in a vertical orientation was the obvious, and generally best, first choice. However, recognising the potential deformation issue and the need to maximise productivity, Optimus3D instead decided to build the component up in the horizontal orientation.

“Our thinking was quite simple,” said Capellan. “By manufacturing the component horizontally, we could minimise the time spent producing the specific batch and help meet Angel Cycle Works budget target. It also meant we were better able to measure and handle deformation, as the chainstay bracket is long and thin, measuring 35 mm x 20 mm x 115 mm.”

However, as expected, manufacturing the component horizontally direct from the CAD file yielded an unacceptable 0.375 mm distortion in the most vulnerable area, Capellan explained.

“To remove this error, we teamed up with Renishaw engineers to arrive at an elegant solution that was based on finite element simulation.”

“Using third party Simufact Additive software, we were able to perfectly simulate the powder bed fusion process of the RenAM 500S system,” explained Alex Garcia, Renishaw application engineer. “What this then enabled us to do was to determine a precise compensation factor that could be used to accurately ‘pre-distort’ the component design.”

Customer demand

Using metal AM, Angel Cycle Works is now able to produce its previously hand-made titanium bicycle chainstay bracket to a guaranteed high level of consistency, with improved weight and strength characteristics, and in quantities that are better able to meet customer demand, according to the company.

While perhaps counter-intuitive to some thinking, Optimus3D’s decision to build-up components horizontally, and employ simulation software to adjust the design for manufacture, has seen worst case deformation reduced from 0.375mm to 0.086mm, well within the component’s 100µm tolerance.

Using metal AM means that during each build volume on the RenAM 500S system engineers can 3D print as many as 50 identical components at a time and on a very short leadtime. Component cost has also been dramatically reduced as a result and supply chain operations streamlined.

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