Automated rigid bodies synthesis for AM compliant mechanisms

Compliant mechanisms achieve motion through elastic deformation rather than traditional rigid-body joints, eliminating wear, backlash, friction, and the need for lubrication. These advantages make them ideal for high-precision applications and harsh environments. While the design of compliant joints is well-studied, the design of the rigid bodies – connecting the joints and transmitting forces/motions – is often overlooked. Existing approaches such as manual modelling, parametric design, and topology optimisation are inadequate for automation due to their fragmented workflows, limited flexibility, and lack of real-time responsiveness. This paper introduces a computational framework for the design of rigid bodies in compliant mechanisms, considering both functional, non-functional objectives and additive manufacturing constraints. Building on guiding curve-based design approaches, the method enables seamless integration of the rigid bodies' synthesis into a fully automated compliant mechanism design pipeline. The process involves: (1) initialising a curve network to connect interfaces while minimising mass, (2) optimising the network to avoid mechanical interferences, maximise non-functional criteria, and satisfy AM constraints, (3) synthesising 3D tubes with locally tuned cross-sections to eliminate critical overhangs, and (4) generating smooth geometries with integrated non-sacrificial supports to reduce post-processing. The proposed methodology ensures manufacturable, reliable, and high-performance designs, advancing the automation of functional AM-enabled compliant mechanisms.