覆盖件模具曲面曲率特征对球头刀铣削力的影响

Influence of Curvature Characteristics of Sculptured Surface on Milling Force in Ball-end Milling of Panel Moulds

针对自由曲面模具的铣削加工,提出一种综合考虑曲面曲率、刀具前倾角和侧偏角的瞬时铣削力预报方法。基于曲面几何特征,研究了进给方向、行距方向曲率半径对刀具切削角度的影响,以及刀具前倾角和轴向切触角对未变形切屑厚度的影响;基于微分思想,将自由曲面加工中任意刀齿切削周期内的切触区进行离散,结合三维次摆线切削轨迹建立未变形切屑模型,得到适合于自由曲面三轴球头铣削的瞬态铣削力,该模型能够综合考虑曲面曲率特征变化、刀具工件切触角度变化;基于二次曲面模具模型进行铣削加工试验,试验测试结果表明,预报的铣削力和试验测量结果在幅值上和变化趋势上具有一致性,在平稳切削时最大铣削力预测误差值在12%以内,验证了该方法能有效地预报自由曲面模具的球头铣削的瞬态铣削力。

A instantaneous milling force prediction method considering of the curvature, the lead angle and the tilt angle, is proposed for sculptured surface mould machining. In view of geometry features of the sculptured surface, the impacts of the curvature radius on feed direction and cross feed direction on cutting angles are explored. Furthermore, the impacts of the lead angle and axial tangential angle on the undeformed chip thickness are studied. By means of differential theory, the cutter-workpiece contact area in arbitrary rotation period of sculptured surfaces machining is discretized. Based on the 3D trochoidal tooth trajectory, the model of the undeformed chip thickness is established and the instantaneous milling force considering of the curvature features and cutting angles is obtained for three axis ball end milling of sculptured surfaces. Finally, experiments of machining mould with quadric surface are conducted to measure the milling force. The estimated milling forces match well with the actual cutting forces obtained from experiments. The error rate of estimated instantaneous milling forces is approximately 12%, which verifies the efficiency of this method to estimate the instantaneous milling force in milling of sculptured surface mould with sculptured surfaces.