Abstract
A new practical workflow for the laser Powder Bed Fusion (PBF) process, incorporating topological design, mechanical simulation, manufacture, and validation by computed tomography is presented, uniquely applied to a consumer product (crank for a high-performance racing bicycle), an approach that is tangible and adoptable by industry. The lightweight crank design was realised using topology optimisation software, developing an optimal design iteratively from a simple primitive within a design space and with the addition of load boundary conditions (obtained from prior biomechanical crank force–angle models) and constraints. Parametric design modification was necessary to meet the Design for Additive Manufacturing (DfAM) considerations for PBF to reduce build time, material usage, and post-processing labour. Static testing proved performance close to current market leaders with the PBF manufactured crank found to be stiffer than the benchmark design (static load deflection of 7.0 ± 0.5 mm c.f. 7.67 mm for a Shimano crank at a competitive mass (155 g vs. 175 g). Dynamic mechanical performance proved inadequate, with failure at 2495 ± 125 cycles; the failure mechanism was consistent in both its form and location. This research is valuable and novel as it demonstrates a complete workflow from design, manufacture, post-treatment, and validation of a highly loaded PBF manufactured consumer component, offering practitioners a validated approach to the application of PBF for components with application outside of the accepted sectors (aerospace, biomedical, autosports, space, and power generation).
Highlights
A high-performance bicycle crank is considered to be one that would be installed on a racing bicycle, the elite of which are operated by professional cycling teams such as those competing in theTour de France
Lack of design capability and the knowledge required to take full advantage of the benefits offered by Additive Manufacturing (AM) were highlighted in this recent UK Government report [31]
The research presented in this paper provides a methodology through which a product can be fundamentally redesigned, manufactured using state of the art AM metals technology, and validated, an approach that can be adopted by industry to engage with this technology and harness the benefits
Summary
A high-performance bicycle crank is considered to be one that would be installed on a racing bicycle, the elite of which are operated by professional cycling teams such as those competing in the. Sci. 2018, 8, 1360 manufactured using Carbon-Fibre-Reinforced Polymer (CFRP) [6] with titanium or aluminium inserts for mechanical interfaces These methods offer limited opportunity for design innovation. TO has been used previously for designing minimal weight structures [7,8,9] where low stiffness is a major consideration in order to cycle more efficiently and effectively, maximising mass is critical to high component performance in the end-use application (e.g., in saving fuel [7,9], performance over both long and short distances through improved power transmission and reduced increasing stability, and decreasing cost [8]). Application this approach to the design has and manufacture of anbeen elite bicycle obtain a paper combination of low mass and high stiffness hasmanufacture, not previouslypost-treatment, been seen. The application of Powder Bed Fusion (PBF) to highly loaded components
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