A novel tool path planning algorithm of denture grinding based on iso-planar method

Dental restorations feature intricate surface contours, necessitating an effective path planning strategy of grinding tools to achieve precise outcomes. A novel tool path generation strategy based on offset surfaces was proposed for grinding of complex ceramic denture crowns. This strategy employed a half-edge data structure to reconstruct the topology of the triangular mesh model and leveraged the topological relationships among facets to develop a division algorithm specifically for denture crowns. Based on the structural characteristics of denture crowns and machine tool performance, these crowns were categorized into four areas. The vertex offset method was utilized to create offset surfaces for grids in each area, while the iso-planar method calculated the initial tool path corresponding to these offset surfaces. Optimization algorithms were introduced to rectify issues such as redundancy in tool paths, self-intersections, Z-shaped trajectories, overcutting in ridge regions, and the need for special optimization in cavity regions present in the original tool path. Given that the offset surface mesh derives from an original model mesh through an offset process, its density correlates with feature complexity; this property enables fewer tool points while still meeting accuracy requirements. Furthermore, these optimization algorithms effectively addressed defects found in initial paths and facilitated efficient high-precision grinding of denture crowns. Experimental results indicated that surface accuracy and machining efficiency achieved by this algorithm meet medical standards.