Robot-assisted multi-axis embedded silicone printing for free-form volumetric model

Embedded silicone printing (ESP) enables the creation of complex soft structures by extruding silicone inks into a gel support matrix. However, issues such as excess local ink deposition and the staircase effect limit the quality of solid model prints, especially when the gel matrix is immiscible with silicone ink. This work presents a multi-axis ESP framework for fabricating volumetric silicone models with nearly solid infill and high surface quality. A field-based curved slicing strategy is introduced to preserve critical surface features and optimise layer height distribution, reducing height variation and ensuring model manufacturability. A boundary-conformal staggered toolpath algorithm further promotes uniform ink deposition, while adaptive toolpath width adjustment mitigates local overfilling and underfilling during curved printing. The framework is validated on a multi-axis robotic platform by fabricating wearable components, biomedical phantoms, and soft robotic structures. Characterization via surface scanning and X-ray CT confirms an infill ratio of 99.47% and a surface error below 1.5 mm (1% of the model size). The proposed framework greatly broadens the practical applications of ESP, enabling the fabrication of customised and functionally integrated soft devices.