Simplification of a G-Code Feeding Path in Roughing Multi-Axis Electrical Discharging Machining for Shrouded Blisks With a Contour Error Constraint

Abstract

Multi-axis electrical discharging machining (EDM) is the main manufacture method for shrouded blisks, which are key components of aero and rocket engines. Involving both linear and rotational axes, a feeding path for machining a narrow and twisted channel consists of a large number of G-code lines. Accelerations and decelerations at junctions, which connect two neighboring G-code lines, can significantly reduce the machining efficiency. In this paper, a new simplification of feeding paths in roughing EDM for shrouded blisks is proposed in order to reduce the number of junctions on a feeding path. However, deviating from the original feeding path, a simplified feeding path can bring over contour errors which can cause geometrical errors of workpieces. Contour error can thus serve as a criterion for simplifying the original path. Eight vertices of a hexahedron, which contains the electrode, are used to represent all points inside and on an electrode. Forward kinematics of a six-axis EDM machine is used to calculate the contour errors of the eight vertices when the electrode feeds along a simplified path. A simplified feeding path can be found provided that the contour error constraint is respected. Machining tests show that the use of a simplified feeding path in roughing EDM machining can reduce the average total machining time by 26.5% without significant impact on surface roughness and white layer thickness.