复杂曲面五轴铣削让刀误差精确预测与刀具姿态规划研究

Marine propeller kind of sculptured surface parts have typical features, such as densely distributed blades, distorted surfaces, large overlapping regions, thin wall, and long overhanging. These features make it difficult to plan the tool path, and machining system of its machine tool has weak stiffness. The cutting force induced tool deflection is increased accordingly, which has a significant effect on the machining accuracy and reduces service performance and life of the part considerably. In this project, aiming at five-axis machining of marine propeller kind of curved surface parts, the flexible cutting force prediction model considering the end deflection will be established. Then the end deflection and deflection induced error under the coupling action between force and deflection will be predicted accurately combining synthesize stiffness characteristic analysis of the whole five-axis machining system. Cutter orientation planning method with optimization objective of deflection induced error will be proposed. Geometry constraint of collision-free condition, kinematic constraint of axes smoothness condition, and physical optimization objective of deflection induced error will be modeled. Then the cutter orientation planning model will be build, whose fast optimization algorithm is also designed. On this basis, the tool deflection induced error is expected to be controlled, which can improve the machining accuracy of the parts. This research will provide core theory and critical technology for high accuracy five-axis milling of marine propeller kind of curved surface part, and expand the utilization of five-axis milling in the field of multi-blade sculptured surface parts.

舰船螺旋桨类复杂曲面零件具有叶片密集、型面扭曲、重叠区大和壁薄悬伸长等典型特征，不仅使其加工轨迹规划非常困难，还使得加工工艺系统呈现弱刚度特性，增大工艺系统末端受力变形，显著影响零件加工精度，从而较大降低零件的服役性能与寿命。本项目针对舰船螺旋桨类复杂曲面零件五轴铣削，在考虑工艺系统末端受力变形反馈基础上，建立柔性切削力预测模型，结合考虑多传动环节的末端综合刚度特性分析与半解析建模，精确预测力-变形耦合作用下的末端变形，及其在工件上映射的让刀误差。提出以让刀误差为优化目标的刀具姿态规划方法，构建避免干涉的几何特征约束、光顺机床轴进给的运动学约束和优化让刀误差的物理目标，并进行刀具姿态规划建模及其快速寻优算法设计。在此基础上，实现让刀误差精确控制和提高零件加工精度。研究成果将为舰船螺旋桨类零件高精度五轴铣削加工提供核心理论与关键技术，并拓展五轴铣削在多叶片复杂曲面零件制造领域的应用。

大型薄壁类复杂构件具有众多复杂内部相交特征，给其内部特征的准确识别带来极大挑战，毛坯模型内部特征的有效识别是实现加工余量确定、切削参数优化及刀具路径规划的重要基础。复杂薄壁类曲面零件具有特征密集、型面扭曲、重叠区大和壁薄悬伸长等典型特征，不仅使其加工轨迹规划非常困难，还使得机床加工系统呈现弱刚度特性，增大加工系统末端受力变形，显著影响零件加工精度，从而较大降低零件的服役性能与寿命。本项目对此设计基于特征矩阵的大型复杂构件毛坯模型相交特征分层识别算法，实现基于毛坯模型拓扑信息的多层次复杂相交特征识别。提出考虑刀具变形反馈的五轴铣削切削力预测方法。针对通用的圆弧铣刀特点，在考虑刀具姿态、刀具变形的情况下，确定圆弧铣刀切削刃的瞬时未变形切屑厚度和切削状态。采用迭代计算确定柔性变形量并构建刀具变形和切削力的相互反馈框架，以精确预测切削力。建立考虑工件曲面加工误差的刀具姿态规划模型。针对复杂曲面零件缩比模型的主体区域，确立了基于最小加工误差的刀具姿态规划优化目标，针对工件复杂特征简化了加工曲面和刀具姿态空间约束，基于最小材料去除率和最大加工残留高度给出了刀具姿态规划加工效率约束。建立刀具姿态规划优化模型，制定曲面切削区域刀具姿态规划优化流程，给出模型求解与刀轨生成的程序计算流程。