Effect of Extruder Type, Shore Hardness, and Infill Ratio on the Mechanical Properties of FDM Manufactured TPU Parts
Abstract
This study investigates the effects of Shore A hardness, extruder type, and infill ratio on ultimate tensile strength (UTS), elastic modulus (E), and elongation at break (%) in FDM-printed thermoplastic polyurethane (TPU) specimens using a multifactor experimental design, ANOVA, and regression models. Unlike previous studies that often focus on printing parameters or material hardness individually, this work presents a holistic evaluation of how Direct Drive and Bowden Tube extruder systems modify the tensile response across different hardness levels and structural densities. ASTM D638 Type-IV tensile tests indicate that Shore hardness is the most dominant factor governing mechanical performance. Considering extruder configuration, the Direct Drive system outperforms the Bowden setup because its shorter filament path and more stable material flow improve interlayer fusion. Numerically, the strongest mechanical resistance was achieved using the Direct Drive system with 95A hardness and 100% infill, yielding the highest UTS (41.2 MPa) and elastic modulus (43.8 MPa). Conversely, the weakest results occurred with the Bowden Tube system at 70A hardness and 50% infill, resulting in the lowest UTS (22.4 MPa) and elastic modulus (18.7 MPa). Maximum ductility was observed at 70A hardness and 100% infill with the Direct Drive system, reaching 703% elongation at break, while the lowest elongation (285%) was recorded using the Bowden Tube at 95A and 50% infill. Overall, the findings recommend 70A + high infill + Direct Drive for applications requiring flexibility, and 95A + 100% infill for applications demanding high strength.
Keywords
FDM, TPU, Extruder type, Tensile test, Taguchi methods
Supporting Institution
This study was funded by the author.
Ethical Statement
Ethical approval and informed consent were not required, as this study involved no human participants or vertebrate animals.
References
- Adib, A. Z., Pratama, J., Salim, U. A., Suyitno, S., Mahardika, M., & Arifvianto, B. (2024). Effect of Core Material Thickness on the Shore Hardness of the Sandwich-Structured Multi-Material 3D-Printed Parts. Applied Mechanics and Materials, 920, 35-42..
- Albardawil, A., Aditya, A. R. M., Mubarok, M. Y., Islami, L. A., & Mardiyana, D. (2025). Improving the mechanical performance of TPU95A filament in FDM 3D printing via parameter optimization using the taguchi method. Engineering Proceedings, 107(1), 62.
- Amor, R. B., Zrida, M., Laurent, H., & Souissi, S. (2024). Influence of geometry and 3D printing parameters on the mechanical properties of PLA tensile specimens. In International Conference on Advances in Mechanical Engineering (pp. 199–209).
- Arifvianto, B., Iman, T. N., Prayoga, B. T., Dharmastiti, R., Salim, U. A., Mahardika, M., & Suyitno. (2021). Tensile properties of the FFF-processed thermoplastic polyurethane (TPU) elastomer. The International Journal of Advanced Manufacturing Technology, 117(5), 1709–1719.
- Bacak, S., Özkavak, H. V., & Sofu, M. M. (2021). Comparison of mechanical properties of 3D-printed specimens manufactured via FDM with various inner geometries. Journal of the Institute of Science and Technology, 11(2), 1444–1454.
- Boğa, C., Seyedzavvar, M., & Zehir, B. (2021). Experimental investigation on the effects of internal architecture on the mechanical properties of 3D printed PLA components. Avrupa Bilim ve Teknoloji Dergisi, (24), 119-124.
- Bruère, V. M., Lion, A., Holtmannspötter, J., & Johlitz, M. (2023). The influence of printing parameters on the mechanical properties of 3D printed TPU-based elastomers. Progress in Additive Manufacturing, 8(4), 693–701.
- Chandramohan, P., Bala Santhosh, M. S., & Raghu, R. (2024). Process parameters optimization through response surface methodology for enhanced strength of additively manufactured thermoplastic polyurethane parts. In International Conference on Additive Manufacturing (pp. 351–368).
- Davis, C. S., Hillgartner, K. E., Han, S. H., & Seppala, J. E. (2017). Mechanical strength of welding zones produced by polymer extrusion additive manufacturing. Additive Manufacturing, 16, 162–166.
- Demir, H. (2022). Novel extruder heat block designs to improve the thermal efficiency of 3D printers. Avrupa Bilim ve Teknoloji Dergisi. 38, 491–500.