Optimizing Mechanical Performance in 3D-Printed Flatfoot Orthopaedic Insoles: A Comparative Analysis of Custom and Standard Infill Design Variations

Yuming Shi, Rafiu King Raji

Article
2025 / Volume 8 / Pages 435-453
Received 31 March 2025; Accepted 13 May 2025; Published 18 June 2025
https://doi.org/10.31881/TLR.2025.011

Abstract
3D printing is a common method for manufacturing Flatfoot Orthopaedic Insoles (FOI). The current manufacturing process relies on pre-defined infill structures provided by slicing software. However, these structures may fail to meet the specific FOIs’ mechanical property requirements, making mainstream 3D-printed insoles less durable than traditional ones. The purpose of this study is to improve FOI’s durability, by using Full Control Gcode Designer (FCGD), specialized 3D print-path design software, to create a dedicated infill structure for FOI. Employing sinusoidal curves as a basis, various structures were designed by tweaking three parameters: sinusoidal amplitude, extruded filament width, and connecting layer design. The specimens, along with control group samples made with standard insole infill structures, were produced using Thermoplastic Polyurethane (TPU) filament. Bending and repetitive compression tests were undertaken to determine the influence of these parameters on bending durability and resistance to repetitive compression stress. The results highlight a significant impact of these parameters on FOI’s durability, indicating that the specified parameter combination can effectively improve the bending durability and resistance to repetitive compression stress in comparison to the mainstream infill structure. This study conducted a comprehensive analysis and established that these parameter combinations can produce an optimal performance for a 3D-printed flatfoot orthopaedic insole.

Keywords
footwear design, Insole infill structure, thermoplastic polyurethane (TPU), additive manufacturing