A Direct Toolpath Constructive Design Method for Controllable Porous Structure Configuration with a TSP-based Sequence Planning Determination

Abstract

The inherent capabilities of additive manufacturing (AM) to fabricate porous lattice structures with controllable structural and functional properties have raised interest in the design methods for the production of extremely intricate internal geometries. Current popular methods of porous lattice structure design still follow the traditional flow, which mainly consists of computer-aided design (CAD) model construction, STereoLithography (STL) model conversion, slicing model acquisition, and toolpath configuration, which causes a loss of accuracy and manufacturability uncertainty in AM preparation stages. Moreover, toolpath configuration relies on a knowledge-based approach summarized by expert systems. In this process, geometrical construction information is always ignored when a CAD model is created or constructed. To fully use this geometrical information, avoid accuracy loss and ensure qualified manufacturability of porous lattice structures, this paper proposes a novel toolpath-based constructive design method to directly generate toolpath printing file of parametric and controllable porous lattice structures to facilitate model data exchange during the AM preparation stages. To optimize the laser jumping route between lattice cells, we use a hybrid travelling salesman problem (TSP) solver to determine the laser jumping points on contour scans. Four kinds of laser jumping orders are calculated and compared to select a minimal laser jumping route for sequence planning inside lattice cells. Hence, the proposed method can achieve high-precision lattice printing and avoid computational consumption in model conversion stages from a geometrical view. The optical metallographic images show that the shape accuracy of lattice patterns can be guaranteed. The existence of “grain boundaries” brought about by the multi-contour scanning strategy may lead to different mechanical properties.