狭长勺型结构件高效插铣加工稳定性预测与刀具设计

Hydroelectric energy industry plays an important role in national strategic emerging industry development plan, domestic manufacturing and processing technology for key parts of the whole CNC machining turbine runner is not yet perfect. According to the problem of efficient plunge milling process faced by parts of multi-constrained long-narrow dippers structure classes (as pelton), such as processing chatter, processing interference, uneasy control processing contour error and so on are easily caused by the overhang of toolholder(ratio of length and diameter is up to 14:1), the following researches are advanced in this project: plunge machining area for parts of this class is molded. tool path geometry molding and its simulation are carried out.Composite contour error,which is caused by eccentric of tool and vibration created by milling force of considering eccentric effect, is predicted. Chatter stability lobe of efficient plunge milling considered the eccentric effect is studied. Geometry parameters of cutting tool is optimal designed, aiming at controling processing contour error of typical parts.Through the above researches, requirement of conforming contour error for parts in stability lobe are realized with plunge milling. Thus， new technology ,new methods and tool design technology with independent intellectual property rights are formed in order to provide practical technical support and theoretical guidance on overall CNC machining for Chinese hydraulic turbine runner.

水电能源行业在国家战略性新兴产业发展规划中占有重要地位，其中国内对整体数控加工水轮机转轮的关键零部件制造加工技术尚不完善。针对多约束狭长勺型结构类零部件（如水斗）面临高效插铣加工问题：如刀柄悬伸长（长度与直径比已超过14:1）容易引起加工颤振、加工过程容易干涉和加工轮廓误差不易控制等，本项目开展以下研究：进行该类型件插铣加工区域建模和刀位轨迹几何建模及其仿真；实现考虑偏心效应的铣削力导致刀具偏移及其振动引起的综合轮廓误差的预测；进行考虑偏心效应的高效插铣加工颤振稳定域的研究；以典型件加工轮廓误差控制为目的，进行刀具几何结构的优化设计。通过上述的研究，在颤振稳定域内插铣加工出符合轮廓误差要求的零部件。从而形成具有自主知识产权的新工艺新方法及新型刀具设计技术，为我国水轮机组转轮的整体数控加工提供理论指导及实用技术支持。

针对大型异型曲面狭窄空间插铣加工时，将可行加工域与插铣刀位轨迹进行规划，使粗加工材料去除量达到最大化；插铣刀具的长径比过大易引起颤振进行插铣过程稳定性研究。.首先，转轮水斗进刀空间狭窄，研究数控加工走刀路线生成，对加工程序进行干涉碰撞仿真检查。研究转轮水斗内表面型面特点，将球头刀路等残留高度法应用到插铣加工，应用插铣加工分层理论制定插铣加工刀路轨迹规划。根据机床运动直线型加减速度和S型加减速控制法，建立插铣加工过程时间模型，应用遗传算法优化插铣加工切削参数，加工效率提高25%。.其次，基于刚性力学原理建立插铣的铣削力模型，即将插铣刀底刃离散成微元来求微元的切削力，并叠加成插铣的铣削力。根据插铣铣削力系数辨识模型，对铣削力进行仿真预测，插铣试验辨识铣削力系数。基于离散傅里叶变换研究在强迫振动下的表面位置误差形成机理，理论和试验研究切削参数和刀具结构参数对表面位置误差影响。.再次，建立插铣三自由度动力学模型及考虑再生效应的插铣切厚模型，对大长径比的插铣系统试验模态分析，识别加工系统的模态参数，并进行插铣时域仿真。基于半离散法对动力学模型求解，得到铣颤振稳定域预测图。仿真研究插铣加工系统动态特性对稳定域的影响，结果表明提高插铣系统的固有频率、阻尼比和刚度均能提高插铣过程的稳定性。变切深插铣试验结果表明取最大李雅普诺夫指数阈值0.6为插铣稳定性判据。.最后，进行插铣刀主偏角参数化设计，仿真研究插铣刀主偏角和刀尖前角对加工变形的影响。基于蒙特卡罗方法优化插铣刀刀齿间距角度，试验研究表明不等齿距插铣刀比等齿距的插铣刀减小铣削力、降低铣削振动和减轻刀具磨损。基于大变形弹塑性有限元理论研究刀具刃口结构对切削温度和刀具磨损影响，同时研究插铣刀的刀尖前角对铣削温度、铣削力和刀具应力影响。基于插铣刀后刀面磨粒、粘结和扩散磨损机理，试验表明插铣刀具后期以扩散磨损为主。