基于时域仿真法的断续铣削颤振预测

Chatter Stability Prediction in Low Immersion Milling Based on Time-domain Simulation

颤振是影响铣削加工表面质量和限制切削效率的重要原因,准确获取稳定性叶瓣图是避免颤振的有效途径。精加工铣削常使用小径向切深/刀具直径比,产生过小的实时切削厚度,刀具容易脱离工件,造成显著非线性因素;过小的径向切深/刀具直径比也导致铣削加工高度断续。因此,常用的圆弧切削厚度已不能近似实际切削厚度,进而影响断续铣削加工颤振预测。采用考虑实际切削厚度的时域仿真法预测断续铣削加工颤振稳定性。该方法使用刀具实际运动轨迹计算切削厚度,并综合考虑了铣削过程中刀具和工件的动力学特性对切削厚度的影响。提出基于相关系数的无量纲颤振判定准则,并用于铣削仿真结果加工状态的判定。通过钛合金Ti6Al4V铣削验证试验结果,所提出的时域仿真法能准确预测小径向切深/刀具直径比所致的断续铣削加工稳定性叶瓣图,为高断续铣削加工无颤振加工参数选择提供了一种有效方法。

Chatter is a major limitation in the machining process, which affects the machined surface and productivity. An accurate stability lobes diagram is efficient to avoid chatter. A small radial depth of cut often used in finish milling means a small uncut chip thickness and highly interrupted machining process. The tool is easy to jump out from the workpiece, which causes obvious non-linearity. Hence, the common circular tooth path is improper to approximate the true tooth path, and influences the accuracy of the stability lobes diagram. A time domain simulation approach based on a dynamic chip thickness model to predict chatter stability in end milling is presented. The time domain simulation for the dynamic cutting process in end milling takes into account both the tool and workpiece dynamics and uses a true tooth trajectory for evaluation of the chip thickness. The variation in the correlation coefficient of the vibration signals between two concessive tool revolutions is examined for developing chatter criterion. The proposed method is assessed and verified using experimental data in low immersion milling of titanium alloy Ti6Al4V. The proposed approach provides a useful way for industrial planners to select chatter free cutting conditions in end milling.