Abstract: To overcome the advantage of the traditional time-step-based surface topography model,a modified time-step-based surface topography model was proposed such as the strong dependence of the size of cutting-edge element and cutting time-step on the workpiece grid size.The equation of cutting-edge swept surface was formulated using homogeneous coordinate transformation in 5-axis milling process.The in-cut cutting-edge element model was established based on the analysis of the contact relationship between ball-end milling cutter and workpiece at different tool orientation.Then,the triangle mesh was generated by using the positions of the adjacent cutting-edge element at the adjacent tool instantaneous rotation angle,and the intersection between the cutter and workpiece was solved using a triangle/segment intersection algorithm.the 5-axis ball-end milling experiments were carried out on AISI P20 steel to validate the modified time-step-based model.Compared with the traditional time-step-based surface topography model,the modified time-step-based surface topography model not only broken through the limitation of workpiece grid size on the size of cutting-edge element and cutting time-step in the traditional model,but also obtained higher prediction accuracy and calculation efficiency.

Key words: modified time-step algorithm, triangle mesh generation, surface topography modeling, prediction accuracy, calculation efficiency

摘要： 为解决传统时间步形貌模型存在的刀刃微元尺寸和切削时间离散步长对工件网格尺寸依赖性强、计算效率低、计算精度差等问题,提出一种改进的时间步形貌模型。首先,基于5轴铣削加工中刀具与工件之间的相对运动关系,运用齐次坐标变换原理建立刀刃扫掠面方程。其次,基于刀具不同倾斜角时与工件的接触关系,建立了切入刀刃模型。然后,根据刀刃微元端点在切削时间离散步的开始及结束时刻的空间位置,对刀刃扫掠面进行三角形网格划分,并提出了面向三角形与线段相交的刀具与工件布尔运算模型。最终,利用AISI P20模具钢球头铣刀5轴加工实验,验证了模型的有效性。研究表明,与传统时间步形貌模型相比,改进的时间步形貌模型不但突破了传统模型中工件网格尺寸对刀刃微元尺寸及切削时间离散步长的限制,而且获得了更高的预测精度及计算效率。

关键词: 改进时间步算法, 三角形网格划分, 铣削表面形貌建模, 预测精度, 计算效率