Research On Efficient Toolpath Generation Method For Dental Restoration

At present, with the rising of our living standard, people’s requirement of oral health has beenheightened accordingly. Prosthodontics is not the simple repair of oral cavity, but also meeting thephysiological and beautiful requirements of patients, which bring out the higher demand for themachining efficiency and quality of dental restorations. The numerical control machining technologyof dental restoration is one of the most important and fundamental technologies of dental CAD/CAMsystem. Combined with the actual demands of dental clinic, choosing the dental restoration as theobject of study, relevant theories, algorithms and key technologies are studied deeply in thedissertation and a dental CAM software module is developed. The main contents and achievementsare as follows:(1) Research on the construction of cutter location model for dental restoration machining. Basedon Z-map model, the Z-map model of original mesh model is constructed. Then, the cutter locationsurface is constructed by judging the interfering relationship between the cutter and points of Z-mapmodel.(2) Combined with boundary extraction algorithm for binary image, a boundary extractionmethod for cutting area detection is proposed. In a cutting layer, the cutting area is transformed into abinary image which is composed of the parts of the cutter location surface above the cutting plane.Based on the map relationship between cutting area and binary image, the cutting area boundary canbe obtained by extracting the boundary of binary image.(3) A offset algorithm of tool path loop is proposed. A pixel area is constructed according to theoriginal tool path loop firstly, and then, a virtual cutter moves along the loop, cutting the pixel area,the boundary of pixel cutting area (the offset curve) is obtained by binary image extraction method.(4) A contour-parallel offset tool path linking algorithm without tool retraction is proposed. Withthe parent-child relationship built during the calculation of tool path loops, a single-root tool path looptree model is constructed and then divided into many sub-trees in accordance with its topology. As aresult, all tool path loops are split into several grouped tool path loop units. Finally, a CPO tool pathwithout tool retraction can be generated by traveling the tool path loop tree. As result, a single regioncan be machined without tool retractions, and thus, the machining efficiency is improved.