CRAFT: A 3D-printed Modular Design Framework for Task-specific Continuum Robots

Continuum robots offer safe and adaptive interaction through body compliance, yet this same property often limits their load-bearing capability. Addressing this design tradeoff typically requires application-specific designs with long development cycles. We introduce CRAFT, a 3D-printed modular design framework for tendon-driven continuum robots that enables rapid mechanical reconfiguration to achieve task-specific stiffness and morphology. The framework comprises a library of six interchangeable modules with distinct stiffness profiles, directional compliance, and degrees of freedom, which can be stacked and reconfigured within minutes using inexpensive components. Each module exhibits predictable mechanical behaviour under bending, axial, and torsional loading, as verified through systematic experimental characterization. We demonstrate the generality of the approach through three representative robots: a reconfigured long teleoperated probe for aircraft-wing inspection (achieving a 41\% reduction in sag), a pipe-crawling robot for confined environments (capable of navigating a \SI{90}{\degree} bend and a \SI{30}{\degree} incline), and a soft robotic hand for fragile object manipulation (achieving an 85\% success rate in an egg-cracking task). Together, these results show how task-specific mechanical properties can be realized through modular composition rather than bespoke redesign, positioning CRAFT as a foundation for rapidly adaptable continuum robots.