沿过渡曲面纵向加工无干涉刀具轨迹生成方法研究

发布时间：2018-04-19 10:23

本文选题：过渡曲面 + 平头立铣刀　；参考：《华中科技大学》2015年硕士论文

【摘要】：在汽车车身、航空航天器及各种成形模具的设计和切削加工中,经常涉及到过渡曲面,作为两个母曲面之间光顺连接的曲面,对于提高产品外表的美观,增强零件的刚度,改善模具的冲压性能,避免冲压件起皱,具有十分重要的作用。通过深入分析和研究,目前只能采用球头铣刀或者成型刀来加工过渡曲面。球头铣刀在切削加工中,切削效率低,加工表面质量差,多次的往返加工影响过渡曲面的光顺性;而成型刀只能加工固定曲率的过渡曲面,不同曲率过渡曲面需要制作不同形状成型刀。对于非固定曲率的过渡曲面,只能采用球头铣刀加工,给实际生产带来极大不便。平头立铣刀通过偏转角度可以获得较大的有效切削半径,具有切削效率高,加工表面光顺等特点。针对球头铣刀或者成型刀在过渡曲面加工中存在的问题,本文提出了一种采用平头立铣刀沿过渡曲面脊线的纵向加工的方法。该方法以刀具的接触点为参照,基于空间过渡曲面在不同位置的曲率变化趋势,偏转平头立铣刀沿过渡曲面脊线的纵向和法向角度,利用平头立铣刀随着偏转角减小而有效切削半径增大的特点,在实际切削过程中尽量减小偏转角,增大有效切削半径,同时保证不发生刀具干涉。每个刀位点计算,通过建立过渡曲面脊线的空间模型,按照曲率匹配原则确定刀具初始位置,基于网格划分法和距离极值法,判断刀具是否发生过切干涉和碰撞干涉,根据刀具的干涉检查结果实时修正刀具的偏转角度,以调整刀具切削姿态和过渡曲面之间的位置关系,从而获得无干涉刀位点。如此类推,可以求得整张过渡曲面的无干涉刀具轨迹。然后,基于传统等残留高度刀具轨迹生成方法建立刀具轨迹的优化模型,对所生成的无干涉刀具轨迹进行光顺化处理,得到满足光顺约束条件的刀位点,最终拟合得到具有等残差光顺的无干涉刀具轨迹。通过仿真分析,本文提出的方法能够实现平头立铣刀沿过渡曲面脊线的纵向的无干涉切削加工,加工后表面残留高度较为均匀,波动较小。与球头铣刀比较,不仅切削加工效率高,而且表面光顺性好,可望在未来过渡曲面编程中得到实际应用验证。
[Abstract]:In the design and cutting of automobile body, aeronautical spacecraft and various forming dies, the transition surface is often involved. As a smooth connection surface between two parent surfaces, it can improve the appearance of the product and enhance the rigidity of the parts.It is very important to improve the stamping performance of die and avoid the wrinkle of stamping parts.Through deep analysis and research, only ball-end milling cutter or shaping cutter can be used to process the transition surface.In the cutting process of ball end milling cutter, the cutting efficiency is low, the quality of the machining surface is poor, and the fairing of the transition surface is affected by many round trips, while the shaping cutter can only process the transition surface with fixed curvature.The transition surface with different curvature needs to be made with different shapes.For the non-fixed curvature transition surface, only the ball end milling cutter can be used, which brings great inconvenience to the actual production.The flat end milling cutter can obtain a large effective cutting radius by deflection angle, which has the characteristics of high cutting efficiency and smooth machining surface.Aiming at the problems of ball end milling cutter or shaping cutter in the machining of transition surface, a method of longitudinal machining with flat end milling cutter along the ridge of transition surface is proposed in this paper.This method takes the contact point of the tool as the reference, and based on the curvature change trend of the spatial transition surface in different positions, the deflection end milling cutter along the longitudinal and normal angles of the ridge of the transition surface.Based on the feature that the cutting radius of flat end milling cutter increases with the decrease of deflection angle, the deflection angle is reduced and the effective cutting radius is increased in the actual cutting process, and the tool interference is guaranteed at the same time.According to the principle of curvature matching, the initial position of the tool is determined by establishing the spatial model of the ridge line of the transition surface. Based on the meshing method and the distance extremum method, whether or not the tool has overcut interference and collision interference is judged.According to the interference inspection results of the tool, the deflection angle of the tool can be adjusted in real time to adjust the position relationship between the cutting attitude and the transition surface, so as to obtain the position of the non-interference cutter.By analogy, the non-interference tool path of the whole transition surface can be obtained.Then, based on the traditional equal height tool path generation method, the optimization model of tool path is established, and the tool locus satisfying the fairing constraint condition is obtained by smoothing the generated non-interference tool path.Finally, the non-interference tool path with equal residual smoothing is obtained by fitting.Through simulation and analysis, the method proposed in this paper can realize the longitudinal non-interference cutting of flat end milling cutter along the ridge of transition curved surface, and the residual height of the surface after machining is more uniform and the fluctuation is relatively small.Compared with the ball end milling cutter, not only the cutting efficiency is high, but also the surface smoothness is good, which is expected to be verified by practical application in the future transition surface programming.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG54

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