Personalisation of safety shoe inlay soles using dynamic foot data

Abstract

This thesis project was carried out as a part of Ultrapersonalised Products & Services (nextUPPS.nl) as a collaboration between TU Delft and Bata Industrials B.V. To integrate new technologies of Industry 4.0 to enhance product and user experience, Bata Industrials, with a facility in Best, Netherlands, partnered with nextUPPS. An opportunity was identified to implement mass personalization of inlay soles by leveraging emerging technologies such as 3D scanning and 3D printing. During this project, extensive literature research was conducted into the biomechanics of feet, the factors influencing the design of inlay soles and shoes, and advancements in 3D printing. State-of-the-art technologies and methodologies for personalized footwear, with a focus on orthotics, were also explored. Insights were gathered from experts in orthotics and inlay sole manufacturing. Additionally, data regarding dynamic plantar pressure during various activities and 3D scanning under different loads and postures were collected for subsequent analysis. Observations were made on this data to understand foot behavior, which helped filter relevant parameters for inlay sole development. Based on the research findings, a comprehensive list of requirements was formulated, encompassing all the gathered data that the inlay sole needed to adhere to. Fused Deposition Modeling (FDM) 3D printing of Thermoplastic polyurethane (TPU) was identified as a viable and cost-effective approach for manufacturing inlay soles. To investigate this, experiments were conducted involving the mechanical testing of samples with different lattice sizes and various TPU variants, aiming to optimize 3D printing materials and parameters. The potential for multi-material printing was also explored during these experiments. Using the insights gleaned from these efforts, a 3D-printable inlay sole was meticulously designed. Its internal structure featured a field-driven variable gyroid lattice pattern, informed by peak pressure pedobarographic data collected during walking. The shape of the inlay sole was derived from 3D scans of the user’s feet. Multiple iterations were undertaken, incorporating user feedback, prototyping, and expert interviews to refine its design. A prototype shell shoe was created specifically to evaluate the performance of the newly developed inlay sole with users. Pressure measurements and interviews were conducted comparing the new design to the conventional one. The test results confirm the design’s effectiveness and underscore the importance of personalization in the inlay sole. The conclusive insole design, along with the corresponding workflow, as well as recommendations for forthcoming actions, equips Bata to potentially launch and market the production of personalized inlay soles for their safety shoes in the future.