Allowance-free numerical-control method for aircraft skin

Abstract

The invention discloses an allowance-free numerical-control method for an aircraft skin. The skin is clamped through three-dimensional scanning to obtain the actual pose and the shape point cloud of the skin; a machining original point adapter and an assembling hole adapter are additionally arranged on a flexible tool to obtain point cloud data of the machining original point adapter and the assembling hole adapter; the assembling hole pose and a tool original point coordinate system are fitted out through a point cloud fitting technique; a theoretical digital-analog milling boundary is mapped to a skin point cloud face through a finite element technology to serve as a milling boundary; and the machining original point coordinate system serves as a machining original point, and the milling boundary serves as a machining path to write numerical-control machining programs. According to the allowance-free numerical-control method, a numerical-control machine tool is utilized to establish an actual machining original point with the machining original point adapter to carry out machining. The allowance-free numerical-control method is not high in requirement for locating accuracy of all clamping point, so that the producing cost of the flexible toll can be greatly simplified.

Description

technical field [0001] The invention relates to the technical field of aircraft skin milling without margin, in particular to a method for CNC milling without margin of aircraft skin. Background technique [0002] The traditional aircraft skin margin removal method is to fix the skin blank on a special trimming die, and the workers manually operate the cutting equipment to trim the edge according to the model, which requires a large amount of labor and low trimming accuracy. Therefore, the milling and cutting of skin blanks by adopting the skin non-residue CNC milling process based on suction cup-type flexible tooling (flexible tooling) can significantly improve the quality and efficiency of milling and reduce the number of tooling, and is the main method to achieve no-residue milling of skin . [0003] However, the main process of the existing sucker-type flexible tooling for skin without margin CNC milling process is as follows: 1. Digital-analog virtual assembly: accordi...

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Problems solved by technology

[0004] According to the above process, there are the following disadvantages in the skin milling without margin: the development cost of the flexible tooling based on this process is high, and the positioning accuracy of the suction cup of the existing flexible tooling is synthesized by the positioning accuracy of the X-axis, Y-axis, and Z-axis of the support rod

The flexible tooling assembly hole locator relies on workers to manually complete the positioning and locking of the x-axis, y-axis, z-axis, A angle, and C angle. The positioning accuracy of each axis is relatively large, resulting in the relative position of the actual clamped skin and the origin of the tool It is inconsistent with the relative position in the assembly digital model, and the NC machining program is compiled based on the three-dimensional assembly digital model, which will cause the overall deviation of the processed skin compared with the digital model

2) The shape and surface of the skin in the actual clamping and assembly of the digital model are inconsistent. On the one hand, due to the large distance between the suction cups, the surface fitted with the suction cup clamping points as discrete points is difficult to be consistent with the theoretical shape and surface, and the edge difference is even greater ; On the other hand, the suction cup of the flexible tooling can swing with the movement, and the clamping (adsorption) of the suction cup is elastic, which will cause the actual suction cup clamping point to be inconsistent with the discrete points of the shape and surface, and the shape and surface after adsorption are inconsistent with the theoretical inconsistent shape

Based on the above-mentioned deficiencies in many aspects, the existing CNC milling process based on suction cup-type flexible tooling without margin can not be widely used in actual production

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