Inverse Operation Based Planning for Hybrid Additive-Subtractive Manufacturing

What is it about?

This work presents a novel process planning method for hybrid additive-subtractive manufacturing, which combines the flexibility of 3D printing with the precision of CNC milling. Current manufacturing approaches often fail to fabricate extremely complex geometries because they cannot effectively place or remove support structures in intricate areas. To solve this, we propose an "inverse operation" strategy. Instead of planning the sequence from start to finish, our algorithm starts with the final target model and works backward to an empty state. In this inverse process, we treat subtractive machining as "adding" material (accretion) and additive printing as "removing" it (erosion). This unique formulation allows the system to intelligently plan removable temporary supports, theoretically guaranteeing that arbitrary 3D shapes—even those with complex internal topologies—can be successfully fabricated.

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Why is it important?

This research is unique because it addresses and theoretically proves a fundamental question in digital fabrication: "Can any model be fabricated?". Unlike traditional forward-search strategies that often encounter topological "dead-ends" where supports cannot be added or removed, our inverse planning ensures completeness for arbitrary shapes. This breakthrough has significant implications for engineering design, particularly Topology Optimization (TO). It eliminates the need for restrictive manufacturing constraints (like self-support requirements) that typically compromise performance. For instance, our experiments demonstrated that a beam optimized without these constraints and fabricated using our method achieved over 30% higher stiffness than one produced with standard constraints. Furthermore, the developed algorithm is highly scalable, capable of processing high-resolution models containing nearly one million solid voxels.

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