Compliant revolute joints (CRJs) offer advantages in terms of frictionless motion, compactness, and monolithic fabrication, but their practical application is often constrained by an inherent stiffness–flexibility trade-off. High rotational compliance is typically accompanied by insufficient resistance to off-axis deformation, leading to parasitic motion and reduced directional stability. To address this challenge, this study proposes a hybrid CRJ designed to enhance directional stiffness while maintaining large elastic rotational capability. The joint integrates stiff polylactic acid (PLA) reinforcement ribs within a compliant thermoplastic polyurethane (TPU) matrix, with material distribution strategically tailored to suppress off-axis deformation without compromising the intended rotational motion. The design is compatible with monolithic fabrication via dual-material fused deposition modelling (FDM). Finite element analysis, informed by experimentally characterised material and interfacial properties, is employed to evaluate the mechanical performance of the proposed joint. The results demonstrate that the hybrid joint exhibits a significantly higher ratio of off-axis to on-axis rotational stiffness compared with mono-material PLA and TPU joints, indicating effective suppression of parasitic deformation while preserving rotational compliance.

Ceramic materials are indispensable in aerospace, energy, and biomedical fields due to their high hardness, heat resistance, and corrosion resistance. However, their inherent brittleness makes it difficult to fabricate complex structures via traditional forming methods. 3D printing provides an effective near-net-shape route, among which Polymer-Derived Ceramics (PDCs) have become a research hotspot owing to binder-free composition, molecular design flexibility, and low-temperature sinterability. This review focuses on photopolymerisation-extrusion coupled moulding as a core strategy to resolve the long-standing trade-off between high precision and low defects in PDC 3D printing. We systematically review the material systems of ceramic precursors, analyze the principles of photopolymerisation-based printing for PDCs, clarify the reaction mechanisms, volumetric shrinkage mechanisms, and extrusion flow behaviors of photopolymerisation-assisted extrusion 3D printing. Emphasis is placed on how coupling mitigates contradictions between precision and defects, improves interlayer bonding, and reduces warpage and cracking. Finally, we summarize key bottlenecks and propose targeted future development directions, providing a clear reference for advancing high-performance ceramic precursor additive manufacturing.

The global manufacturing industry is undergoing a transformation towards lightweight and high-performance development, and aluminum alloys have become the dominant material for key components of high-end equipment. The conventional single-wire directed energy deposition-arc (single-wire DED-arc) suffers from inherent limitations, including excessive heat input and fixed compositions of commercial welding wires. While multi-wire directed energy deposition-arc (multi-wire DED-arc) technology presents significant advantages, its development still faces numerous challenges. This paper reviews the research status and engineering progress of multi-wire DED-arc technology for aluminum alloys, analyzes the synergistic regulation mechanism of three core process dimensions (wire feeding rate regulation, current-voltage synergistic control, and inter-wire geometric parameter optimization), and summarizes its applications in the automotive, rail transit, and aerospace fields. It further identifies the core advantages and key bottlenecks of this technology, establishes a unified theoretical framework for multi-wire DED-arc aluminum alloy forming, and can provide a valuable reference for future research in this field and the development of dedicated precision equipment.