Designing Interlocking Interfaces of Complex Geometries for Multimaterial 3D Printing

Multimaterial additive manufacturing enables the fabrication of complex components with distinct mechanical, thermal, or aesthetic properties. However, conventional CAD tools lack primitives for systematically generating interlocking features across freeform material boundaries, often resulting in weak interfacial adhesion and structural failure. We present a layer-wise framework for generating robust interlocking geometries of overlapping volumes, enabling multimaterial additive manufacturing. Our method begins by voxelizing the intersection region between two input meshes and, on each horizontal slice, employs an A*-driven splitting path to partition the layer into complementary halves. We replace the original intersecting volume with designed interlocking boundary primitives and reassemble the modified voxels into two watertight meshes. A continuity heuristic assigns each half to its corresponding original mesh, ensuring consistent connectivity across successive layers. We validate our approach on both simple geometries (intersecting cubes) and complex shapes (a rabbit with a backpack), demonstrating that our algorithm reliably generates valid interlocking patterns across a range of voxel sizes. Runtime analysis reveals that mesh reconstruction is the primary computational bottleneck, while voxelization scales with mesh complexity. The manufacturability and the mechanical robustness of the generated interfaces were validated by physical printing using a dual-extrusion FDM printer. This framework provides a foundation for computational design tools that enable automated generation of fabrication-ready multimaterial assemblies with watertight, mechanically robust interlocking interfaces.