Soft 3D-Printed Endoskeleton for Precise Tendon Routing in Soft Robotics
Emanuele Solfiti, Alessio Mondini, Emanuela Del Dottore, Barbara Mazzolai, Alberto Parmiggiani
AI summary
Problem
Encapsulating curved tendons in soft polymeric matrices during casting is challenging due to maintaining structural compliance, ensuring accurate tendon positioning, and avoiding multi-step processes or rigid inserts that compromise flexibility.
Approach
A semi-automated design workflow generates a flexible, 3D-printed endoskeleton that guides tendons through predefined eyelets; it is anchored in a mold and embedded in a single-step silicone casting process to preserve the intended path while matching the surrounding material's compliance.
Key results
- Marginal stiffening effect on silicone body confirmed via tensile/compression tests
- Tendon-pulling poses closely match finite element simulation predictions
- Semi-automatic workflow generates custom endoskeletons for arbitrary 3D tendon paths
- Single-step casting preserves complex tendon routing without delamination
Why it matters
Provides soft robotics researchers and manufacturers with a streamlined, compliant, and reproducible method for fabricating complex tendon-driven actuators.
Abstract
This paper presents the design, development, and testing of a soft 3D-printed endoskeleton for arbitrary cable routing in tendon-driven soft actuators. The endoskeleton is embedded in a silicone body, and it is fixed to the mold prior to the casting process. It enables tendons to be placed through predefined eyelets, ensuring accurate positioning within the soft body. To minimize its impact on the overall stiffness of the soft body, the endoskeleton was designed with a slim profile, flexible connections, and 3D-printed with elastic material (Shore A hardness 50), selected to roughly match the mechanical properties of the surrounding silicone matrix (typically with Shore 00 hardness 20–30). Key features of the proposed solution include a 3D-printable guide for tendon routing that is (1) fully soft, (2) easy to place, (3) rapidly reconfigurable for arbitrary tendon paths, (4) adaptable to variable soft body geometries, and (5) easy to fabricate with single-step casting. The current work describes the design, manufacturing, simulation, and testing of a simplified case study in which the endoskeleton is employed to reproduce a target pose predicted by FE analysis with good matching, demonstrating the effectiveness of the approach.