医用钛合金牙科修复体小直径球刀五轴高效铣削加工策略研究

Dental prostheses have complex shape with small size, and their material are usually biomedical titanium alloy. The dental prostheses require high accuracy and high machined surface quality. Five-axis machining with small-diameter cutters is necessary to mill the dental prostheses. The goal of this research is to short the machining time for five-axis dental prostheses milling with biomedical titanium alloy using small-diameter ball-end cutters, and the contents of this research are listed as follows: efficient tool orientation generation, cutting force prediction considering runout, feedrate schedule and machined surface topography prediction. Accordingly, the research will develop the strategies for efficient five-axis dental prostheses milling. The aims are listed as follows. A method of smoothing rotary axes movements within the tool orientation feasible regions will be developed, which can acquire the optimal solution efficiently. Methods of runout parameters identification and cutter-workpiece engagement extraction considering runout will be presented, improving cutting force prediction for five-axis ball-end milling with biomedical titanium alloy. In the basis of cutting force prediction, the multiple objective optimization model for feedrate schedule with multiple constraints will be established, shortening machining time while smoothing feedrate variation. A surface topography prediction method considering local feedrate and runout will be presented, which is the basis of feed-interval and pick-interval parameters selection. This research will provide the theoretical foundation of dental prostheses machining with high efficiency and quality.

牙科修复体体积小、形状复杂、材料多为医用钛合金，且对加工精度和表面加工质量要求高，需采用小直径球刀五轴铣削加工。本项目围绕缩短小直径球刀五轴加工医用钛合金牙科修复体时间的目标，拟从球刀高效刀轴矢量生成、考虑刀具跳动的球刀五轴铣削力预测、多目标多约束五轴加工进给速度规划和球刀五轴加工表面形貌预测四方面展开研究，提出修复体五轴高效加工策略。本项目旨在：研究可行空间中规划机床旋转轴运动平稳的刀轴矢量新方法，缩短计算时间且获得最优解；探究刀具跳动参数辨识方法和考虑刀具跳动的刀具-工件接触域提取方法，提高医用钛合金铣削力预测精度；在切削力预测的基础上，建立多目标多约束的进给速度规划模型，缩短加工时间且平滑进给速度变化；开展考虑刀具跳动和局部进给速度影响的球刀加工表面形貌预测研究，为刀具进给步距和侧向步距选择提供依据。本项目的研究成果可为医用钛合金牙科修复体高效高质量铣削加工提供理论基础。

牙科修复体体积小、形状复杂，需采用小直径球刀五轴铣削加工。五轴机床的两个旋转轴极大地提高了牙科修复体的加工精度，却给生成高质量的复杂曲面五轴加工刀具路径带来了不少难点。如何调整刀具姿态避免碰撞，同时满足几何误差、刀具运动光顺和机床各轴运动平滑等要求，一直是五轴加工刀具路径规划的难题。本研究提出了牙科修复体五轴加工刀轴矢量规划方法，使生成的加工刀具路径具有光顺的机床旋转轴运动轨迹；提出了鲁棒的侧铣加工刀具包络面建模方法，然后提出了基于刀具包络面的侧铣加工刀具路径几何误差分布快速计算方法；提出了平底锥铣刀多约束多目标的侧铣加工刀具路径生成方法，使生成的侧铣加工刀具路径具有光顺的机床旋转轴运动轨迹和刀具参考点轨迹；使用离散矢量法表示牙科修复体几何模型，研究了五轴铣削加工几何仿真方法和刀具-工件接触区域提取方法。项目研究成果对于复杂零件的数字化制造具有重要意义。