A mapping-based graded infill structure design method and continuous printing path planning

Cellular infill structures are widely used in many fields due to their excellent properties. The additive manufacturing technologies make it possible to fabricate complicated cellular infill structures with different functions. This paper presents a design method for graded infill structures that can quantitatively control the density of the infill structures. Given a 2D filling region represented by a triangular mesh, the proposed method first expands the original region according to a predefined scalar density field, and the extent of expansion is positively related to the density field. The design of graded infill structures mainly relies on the established mapping between the original region and the expanded region. Specifically, the uniform filling patterns are designed in the expanded region, and the graded infill structures are obtained by the inverse mapping process. The continuous printing path planning algorithms for both the graded lattice and the honeycomb infill structures are developed. In addition, the 2D method is also generalized to curved surfaces and 3D cases. Both physical and simulation experiments were conducted, and the results show that graded structures exhibit superior mechanical strength compared to uniform filling. Additionally, the structural stiffness can be adjusted by modifying design parameters such as cell dimensions and expansion coefficients. Graded honeycomb structures demonstrate higher strength than graded lattice structures, the greatest improvements are observed around the filling ratio of 31 %, with strength increases of 216 % for uniform filling and 100 % for non-uniform filling. The proposed method has significant potential for application in additive manufacturing, particularly in extrusion-based printing processes such as fused deposition modeling (FDM) and wire arc additive manufacturing (WAAM).