Research On Feedrate Scheduling Method In Five-axis Machining Of Sculptured Surfaces

Sculptured surface parts have been widely applied in aerospace, mold manufacturing and other industrial fields, and its processing level is a reflection of the competitiveness of a country or an enterprise in these fields. As the most important machining method for sculptured surface parts, five-axis CNC machining technology has aroused widespread concerns. During the machining process, the feed rate and its change have a significant impact on machining accuracy, surface quality and cutting efficiency. Theodore, the issue of feed rate scheduling has its very important position in five-axis CNC machining technology.This paper presents an adaptive feed rate scheduling method with multi-constraints for parametric curve interpolation. The constraints including chord error limit, the velocity and tangential acceleration limits of cutter tip, the angular velocity and acceleration limits of tool axis, the velocity and acceleration limits of machine’s axes, have been taken into account in feed rate scheduling from the perspectives of geometric precision, cutting performance and the drive performance of machine tools.Actually, the tool path can be can be described by two NURBS curves in five-axis CNC machining. It’s easy to derive the analytic relations between the above mentioned constraints and the cutter tip velocity by using the kinematics transformation of machine tools, and the geometric information, such as curvature, tangent vector which is contained in NURBS curve itself. Then, the linear programming model can be developed after sampling the tool path with a suitable parameter interval, and the implementation of linear approximation to the analytical relations. The developed model aims to minimize the sum of squared velocity of cutter tip. The cutter tip velocity of each sampled position with all the given constraints satisfied can be obtained after the linear programming problem is solved, and then, the ultimate feed rate curve can be built by fitting all the discrete data of cutter tip velocity.An simulation verification experiment is carried out on a dual-NURBS-curve tool path with a relatively complex shape in this paper. Additionally, other two kinds of frequently-used feed rate scheduling methods were also simulated as an experiment control. The simulation results show that the novel proposed feed rate scheduling method in this paper can satisfy all the given constraints, and greatly improve the performances of machining accuracy, dynamic characteristics and so on. In a word, the adaptive feed rate scheduling method proposed in this paper provides a good solution method to the acceleration and deceleration control in five-axis CNC machining. Hence, it has a broad applicable prospect.