CN-122018425-A - Numerical control five-axis fairing tool path generation method based on free-form surface model

CN122018425ACN 122018425 ACN122018425 ACN 122018425ACN-122018425-A

Abstract

The invention discloses a numerical control five-axis fairing tool path generation method based on a free-form surface model, which comprises the steps of firstly determining an initial tool sub-path of a to-be-processed parameter curved surface, carrying out boundary extension and resampling on the current tool sub-path to obtain a reference central line, carrying out bias on the reference central line by utilizing a contour height bias algorithm to obtain a contour height bias line, obtaining a corresponding pareto optimal solution set based on a multi-objective evolutionary algorithm aiming at the contour height bias line, obtaining an optimal fairing path point set based on the obtained pareto optimal solution set, finally fitting to obtain a next tool sub-path, carrying out cyclic treatment one by one until all tool sub-paths are obtained, and connecting all obtained tool sub-paths to obtain a complete numerical control five-axis fairing tool path. The method realizes effective balance of equal residual height paths and smoothness in numerical control machining of complex curved surfaces, obviously reduces path curvature fluctuation, and optimizes global machining efficiency and surface forming quality.

Inventors

FU JIANZHONG
Wu Runmao
LIN ZHIWEI
JIN HUIHUI

Assignees

浙江大学
浙江先端数控机床技术创新中心有限公司

Dates

Publication Date: 20260512
Application Date: 20260410

Claims (10)

1. A numerical control five-axis fairing tool path generation method based on a free-form surface model is characterized by comprising the steps of firstly determining an initial tool sub-path of a to-be-processed parameter surface, conducting boundary extension and resampling on the current tool sub-path to obtain a reference center line, conducting bias on the current reference center line by means of a contour bias algorithm to obtain a contour bias line, obtaining a corresponding pareto optimal solution set based on a multi-objective evolutionary algorithm aiming at the current contour bias line, obtaining an optimal fairing path point set based on the currently obtained pareto optimal solution set, finally fitting to obtain a next tool sub-path, conducting one-by-one circulation processing by taking the tool sub-path as the current tool sub-path until all tool sub-paths are obtained, and connecting all obtained tool sub-paths to obtain a complete numerical control five-axis fairing tool path.
2. The method for generating the numerical control five-axis fairing tool path based on the free-form surface model according to claim 1 is characterized in that when determining an initial tool sub-path of a parameter surface to be processed, an initial guide line is firstly determined based on topological characteristics of the parameter surface to be processed, and discrete sampling is carried out on the initial guide line to obtain the initial tool sub-path.
3. The method for generating the numerical control five-axis fairing tool path based on the free-form surface model according to claim 1, wherein the boundary extension of the current tool sub-path is realized based on unit guide vectors at the head end and the tail end of the current tool sub-path and a curved surface bounding box of the curved surface model.
4. The method for generating a numerical control five-axis fairing tool path based on a free-form surface model as set forth in claim 3, wherein when the boundary continuation is performed on the current tool sub-path: Extracting a plurality of discrete point columns at the head end and the tail end of a current cutter sub-path, respectively calculating the weighted average value of the direction vectors of the discrete point columns to obtain unit guide vectors with the head end and the tail end extending outwards; Acquiring a curved surface bounding box of the curved surface model, expanding the curved surface bounding box in three coordinate directions, and constructing an expanded curved surface bounding box; And based on the unit guide vector, extending the head and tail end points of the current cutter sub-path outwards in a straight line, calculating a space intersection point between the head and tail end points and the plane of the extended curved surface bounding box, and completing boundary extension of the current cutter sub-path by taking the obtained intersection point as an extension end point.
5. The method for generating the numerical control five-axis fairing tool path based on the free-form surface model according to claim 1, wherein when solving the pareto optimal solution set, firstly, self-adaptive segmentation processing is carried out on a current reference center line and an equal residual height bias line, and then, a corresponding pareto optimal solution set is obtained for each sub-path segment based on a multi-objective evolutionary algorithm.
6. The method for generating the numerical control five-axis fairing tool path based on the free-form surface model according to claim 5, wherein the segmentation processing is performed by adopting a constrained heuristic forward search algorithm.
7. The method for generating a numerical control five-axis fairing path based on a free-form surface model according to claim 5, wherein after the adaptive segmentation processing is performed on the current reference center line and the equal residual height offset line, a shared point expansion data set based on an overlapping domain is built, the shared point expansion data set is used as input, and the corresponding pareto optimal solution set is obtained by utilizing the multi-objective evolutionary algorithm.
8. The method for generating a numerical control five-axis fairing path based on a free-form surface model according to claim 5, wherein the multi-objective evolutionary algorithm comprises the following two objective functions: taking the deviation between the minimum reference center line and the area surrounded by the equal residual height offset line and the deviation between the minimum reference center line and the area surrounded by the target fairing path as a first objective function; the second objective function is a track smoothness index based on a bending energy metric that minimizes the target fairing path.
9. The method for generating a numerical control five-axis fairing path based on a free-form surface model according to claim 1, wherein the optimal fairing path point set is identified and screened from the pareto optimal solution set by utilizing a marginal effect analysis method based on curve fitting.
10. The method for generating a numerical control five-axis fairing path based on a free-form surface model according to claim 9, wherein the marginal effect analysis method based on curve fitting comprises the following specific steps: (5-1) fitting a discrete pareto optimal solution set by adopting a spline curve with monotonicity constraint, and constructing a fitting curve which strictly monotonically decreases and passes through partial solution points; (5-2) calculating the absolute value of the derivative of the fitted curve; (5-3) the absolute value of the derivative is reduced to a preset threshold value, and a coordinate point meeting the preset derivative threshold value is determined as a theoretical optimal decision point; (5-4) searching the discrete solution closest to the theoretical optimal decision point Euclidean distance in the pareto optimal solution set, and taking the discrete solution as a final output fairing path point set.

Description

Numerical control five-axis fairing tool path generation method based on free-form surface model Technical Field The invention belongs to the technical field of numerical control machining and tool path planning, and particularly relates to a free-form surface five-axis numerical control tool path fairing generation method based on multi-objective optimization. Background In modern manufacturing industry, numerical control machining technology (CNC) plays a crucial role, especially in the fields of aerospace, automobile, mold manufacturing and the like, where high precision machining of complex parts is required. The five-axis numerical control machining technology is used as an advanced form of numerical control machining, has the advantages of high machining flexibility, excellent precision, capability of processing complex curved surfaces and the like, and is particularly suitable for machining shell pieces in the aerospace field, such as aircraft wings, fuselage shells, engine shells and the like. These complex parts typically have large curvatures, free-form surfaces and thin-walled structures, requiring high precision, high quality machining, whereas five-axis numerically controlled machining can cut in multiple angles and directions, meeting these requirements. In modern numerical control processing, the equal residual height method aims at maximizing the utilization of local curvature information of curved surfaces, so that the residual height distribution between adjacent tracks is uniform and constant, and the maximum line spacing and the minimum path number are realized in theory. The method generally adopts a recursive bias strategy to generate, namely, an initial track is selected, and the next track point meeting the residual height constraint is calculated point by point based on sampling points. Although the equal residual height method has obvious advantages in shortening the total length of the path, two major challenges are faced, namely, the shape of the whole path is highly dependent on the initial track, if the initial selection is improper, the subsequent path is seriously deviated from the ideal feeding direction, and the smoothness is insufficient, and at the curvature abrupt change, the geometric bias is extremely easy to introduce sharp points or discontinuities, so that the processing stability is influenced. Disclosure of Invention In view of the defects of the prior art, the invention provides a five-axis numerical control tool path fairing generation method based on multi-objective optimization, which is used for solving the defects of path drift, poor fairing and the like of a residual high tool path in the prior art. In order to achieve the above purpose, the invention adopts the following technical scheme: A numerical control five-axis fairing tool path generation method based on a free-form surface model comprises the steps of firstly determining an initial tool sub-path of a to-be-processed parameter curved surface, then conducting boundary extension and resampling on a current tool sub-path to obtain a reference center line, conducting bias on the current reference center line by means of a constant residual height bias algorithm to obtain a constant residual height bias line, obtaining a corresponding pareto optimal solution set based on a multi-objective evolutionary algorithm aiming at the current constant residual height bias line, obtaining an optimal fairing path point set based on the current pareto optimal solution set, finally fitting to obtain a next tool sub-path, conducting one-by-one circulation processing by taking the tool sub-path as the current tool sub-path until all tool sub-paths are obtained, and connecting all obtained tool sub-paths to obtain a complete numerical control five-axis fairing tool path. Further, the numerical control fairing tool path generating method based on multi-objective optimization comprises the following steps: (1) Optimizing an initial guide line based on the topological characteristic of the parameter curved surface to be processed, and carrying out self-adaptive discrete processing by combining chord height error constraint to construct an initial cutter sub-path; (2) Carrying out boundary continuation and resampling on the current cutter sub-path, and extracting a reference center line for generating an equal residual height path; (3) Generating a bias line based on the reference center line by using a contour height offset algorithm as a next tool sub-path to be processed; (4) Performing self-adaptive segmentation processing on the current reference center line and the equal residual height offset line, and constructing a shared point expansion data set based on an overlapping domain to form a plurality of sub-path segments; (5) Constructing a multi-objective optimization model (or a multi-objective evolutionary algorithm) based on parameter domain linear interpolation for each sub-path segment, aiming at minimizing curva