Iso-parametric path planning to mitigate wheel wear in grinding of complex dental crowns

A novel isoparametric tool path generation strategy incorporating spacing control was developed to overcome machining challenges in complex dental restoration fabrication, with particular emphasis on mitigating undercut formation and minimizing tool wear. To enhance machining efficiency and accuracy, a preprocessing strategy was introduced for prioritized reconstruction of offset surfaces, facilitating spiral trajectory parameterization. A segmented 3D-to-2D mapping algorithm was developed, achieving a 44.43 % reduction in computational time while maintaining machining precision. The formation mechanism of undercuts in dental restoration structures was systematically analyzed. Based on this analysis, a surface formation prediction algorithm was established to accurately identify undercut areas in cavity regions after machining. This enables the implementation of localized overcut strategies to replace conventional global undercut approaches, thereby improving the fitting accuracy and stability of dental restorations. The wear characteristics of ball-end grinding wheels were investigated, with particular focus on the relationship between spiral trajectory spacing and tool wear. In undercut regions, the machining allowance was observed to significantly affect cutting depth, leading to increased grinding forces and accelerated tool wear. To mitigate this effect, a localized spacing reduction strategy was proposed, which effectively minimizes tool wear while only slightly increasing machining time. The effectiveness of the proposed methodology was verified through precision grinding experiments on complex dental restoration structures. These methods have the potential to be applied to a wide range of complex 3D machining and manufacturing problems.