Assembled skin milling fixture and manufacturing method thereof

Abstract

The present invention belongs to the technical field of mechanical processing, and specifically relates to an assembled skin milling fixture and a manufacturing method thereof. In the assembled skin milling fixture provided by the present invention, an adjustable flexible column is converted into a fixed-height working profile assembly block, and a group of fixed assembly blocks are designed for different skin parts respectively, and areas with the same curvature can also be used universally. When in use, the same group of fixed assembly blocks are uniformly installed on the same set of universal positioning bases, and the effect of replacing the milling tooling can be achieved by replacing all or part of the assembly blocks. The assembled skin milling fixture provided by the present invention does not need to perform overall processing of the fixture profile, but only needs to select various local typical areas that support and fix the skin for profile processing, and the skin with the same curvature can also realize the borrowing of supporting assembly blocks, which can effectively reduce the processing cost of the skin milling tooling.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical processing, and in particular relates to an assembled skin milling fixture and a manufacturing method thereof. Background Art

[0002] After the forming process, aircraft skin parts undergo milling to achieve their final dimensions. This milling process is performed on a five-axis CNC machining center and requires a milling fixture. If a fixture were required for each skin, the required number of fixtures would be enormous, incurring significant tooling costs and making subsequent storage and maintenance difficult.

[0003] The most advanced skin milling method currently uses a flexible multi-point vacuum system to mill the skin's contours. This method uses multiple flexible lifting columns, each height adjusted according to the skin's curvature, to support the skin. However, the flexible multi-point equipment used in this method is complex, cumbersome to operate, and expensive. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an assembled skin milling fixture that can simplify the processing of working surfaces, achieve accurate connection between each combined block and the universal positioning base, and enable the tooling to be quickly positioned on a five-axis CNC machining center.

[0005] Specifically, in situations where flexible multi-point equipment is unavailable, the present invention transforms adjustable flexible columns into fixed-height work surface blocks. Different skin components are each designed with a set of fixed blocks, allowing for universal use in areas with the same curvature. During use, the same set of fixed blocks is uniformly mounted on a common positioning base, and replacing all or some of the blocks effectively replaces the milling tooling.

[0006] The technical solution of the present invention is:

[0007] A assembled skin milling fixture includes a universal base 1 of a zero-point positioning system and a skin support assembly block 2, wherein the universal base 1 of the zero-point positioning system includes a surface-straight steel plate 101, a cast hanger 102, a zero-point locator 103, transverse ribs 104 and longitudinal ribs 105, wherein the transverse ribs 104 and the longitudinal ribs 105 are located at the lower part of the universal base 1 of the zero-point positioning system, and the surface-straight steel plate 101 is located at the upper part of the universal base 1 of the zero-point positioning system, the transverse ribs 104 and the longitudinal ribs 105 support the surface-straight steel plate 101 to ensure the rigidity of the universal base 1 of the zero-point positioning system, the zero-point locator 103 is arranged on the upper surface of the surface-straight steel plate 101, and is evenly distributed horizontally and vertically; on the side wall of the universal base 1 of the zero-point positioning system, a cast hanger 102 is provided at the intersection of the transverse ribs 104 and the longitudinal ribs 105.

[0008] A skin support assembly block 2 is arranged on the universal base 1 of the zero-point positioning system, wherein the skin support assembly block 2 is arranged according to the structure and shape of the skin to be processed, and the distribution of the skin support assembly blocks 2 at the peripheral position of the skin to be processed is denser than the distribution of the skin support assembly blocks 2 at the internal position of the skin to be processed, so that the skin support assembly blocks 2 are interchangeable and the shaking of the skin to be processed during milling is controlled; positioning pins are also provided on the skin support assembly block 2, and the positioning pin holes of the skin to be processed are connected with the positioning pins on the skin support assembly block 2 to position the skin.

[0009] In a specific embodiment, the skin supporting assembly block 2 is made of magnetic material, so as to fix the skin to be processed by utilizing the adsorption force between the magnet and the skin supporting assembly block 2.

[0010] In a specific embodiment, the skin supporting assembly block 2 is provided with a vacuum adsorption device, and after the skin to be processed is positioned, the vacuum adsorption force is used to fix the skin to be processed.

[0011] On the other hand, the present invention provides a method for manufacturing a skin using the above-mentioned assembled skin milling fixture, which comprises the following steps:

[0012] Step 1: Construct a 3D manufacturing data set based on the skin to be processed;

[0013] Step 2: Design the distribution of each supporting assembly block 2 of the assembled skin milling fixture according to the three-dimensional manufacturing data set constructed in step 1);

[0014] Step 3: Each skin support assembly block 2 of the assembled skin milling fixture obtained in step 2) is processed separately, and the curved working surface is CNC milled by a zero-point positioning system;

[0015] Step 4: Number each skin support assembly block 2 of the assembled skin milling fixture obtained in step 3) and design an installation layout to avoid installation errors;

[0016] Step 5: Install and fix each skin support assembly block 2 of the assembled skin milling fixture on the universal base 1 of the zero point positioning system;

[0017] Step 6: Hoist the semi-finished skin parts to be processed onto the five-axis CNC machining center and position them using positioning pins and an assembled skin milling fixture; after positioning, use the adsorption force of magnets to fix the skin to be processed;

[0018] Step 7: Drill holes and mill edges of the skin to be processed;

[0019] Step 8: Remove the skin after processing.

[0020] The effects and benefits of the present invention are:

[0021] The assembled skin milling fixture and its manufacturing method provided by the present invention can realize accurate positioning of the assembled skin milling fixture and the five-axis CNC machining center through the use of a zero-point positioning system, and the zero-point positioning system is always connected to the equipment. Replacing the skin milling fixture is to replace each supporting assembly block, which not only realizes installation and positioning, but also avoids the process of lifting, installing, and aligning large fixtures, making fixture replacement and installation simpler and safer. The assembled skin milling fixture can also decompose and simplify the fixture working surface, so that each supporting assembly block can be individually CNC machined and surface ground, improving processing efficiency and processing accuracy. The assembled skin milling fixture does not need to perform overall processing of the fixture surface, but only needs to select each local typical area that supports and fixes the skin for surface processing, and the skin with the same curvature can also realize the borrowing of supporting assembly blocks, which can effectively reduce the processing cost of the skin milling fixture. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the installation distribution of the positioning pins of the zero-point positioning system.

[0023] Figures 2A to 2C This is a structural diagram of the universal base of the zero-point positioning system of the assembled skin milling fixture provided in an embodiment of the present invention, wherein Figure 2A is a side view, Figure 2B For top view, Figure 2C It is a schematic diagram of the three-dimensional structure.

[0024] Figure 3 This is a schematic diagram of the distribution of the skin support assembly blocks of the assembled skin milling fixture provided in an embodiment of the present invention.

[0025] Figure 4 It is a schematic structural diagram of the skin support assembly block of the assembled skin milling fixture provided in an embodiment of the present invention after installation.

[0026] Figure 5 This is a schematic diagram of the positional relationship of the skin parts installed in the assembled skin milling fixture provided in an embodiment of the present invention.

[0027] In the figure: 1 universal base of zero-point positioning system; 101 flat steel plate; 102 casting hanging rod; 103 zero-point locator; 104 transverse ribs; 105 longitudinal ribs; 2 skin support assembly block; 3 skin edge line. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0029] It should be understood that the accompanying drawings are not drawn to scale, but are merely simplified drawings for illustrating various features of the basic principles of the present invention. The specific design features of the present invention disclosed herein, including, for example, specific dimensions, directions, positions, and shapes, will be determined in part by the specific environment in which they are to be applied and used.

[0030] In the accompanying drawings, the same or equivalent components (elements) are marked with the same reference numerals.

[0031] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" and the like to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0032] In order to realize the use of assembled skin milling fixture, it is necessary to first have a multi-unit zero-point positioning system with zero-point locators evenly installed on the system; then divide the skin parts into sections and design each support block separately, and the skin with the same curvature can also be designed in a coordinated manner; then design and install zero-point positioning pins at the bottom of each support block, and the position corresponds to the position of the zero-point locator on the zero-point positioning system; finally, use a small-scale zero-point positioning system to perform CNC machining of the working surfaces of each support block of the assembled skin milling fixture.

[0033] Since the various assembling blocks of the assembled skin milling fixture provided by the present invention need to be installed on the same set of universal positioning bases, the assembling blocks and the bases have high positioning accuracy. Therefore, the zero-point positioning system is used to meet the requirements of accurate positioning of each assembling block and the universal positioning base. The zero-point positioning system is a clamping positioning system developed by the German AMF company, which can greatly optimize the production process, increase the actual processing time of the equipment, shorten the replacement time of the workpiece or fixture, improve the repeat positioning accuracy, and achieve positioning and clamping in one step. The zero-point positioning system is a single connection contact interface between four locating pins and the zero-point locator, with accurate positioning and applicable to almost any equipment. The four locating pins used in the zero-point positioning system have different functions: a zero-point locating pin serves to limit the freedom of the X and Y directions and becomes a reference base point; a one-way locating pin only limits the freedom of the rotation direction; and two fastening positioning pins only serve to increase the clamping force. This can ensure complete positioning and avoid over-positioning. The installation distribution of the locating pins of the zero-point positioning system is as follows: Figure 1 As shown, the upper right corner is the zero point positioning pin, the upper left corner is the one-way positioning pin, and the others are fastening positioning pins.

[0034] 1. Design of universal base for zero point positioning system

[0035] The universal base of the zero-point positioning system is to install multiple zero-point locators on a flat steel plate, and each zero-point locator is evenly distributed horizontally and vertically. In order to meet production needs, the zero-point positioning system must be larger than the outer dimensions of the required processed skin. However, due to the large outer dimensions of the skin, the outer shape of the universal base of the zero-point positioning system must also be large, which will affect the rigidity of the universal base of the zero-point positioning system. Therefore, the universal base of the zero-point positioning system is processed by integral casting of cast steel materials: the upper half is a flat steel plate, and is used to install the zero-point locator; the lower half is a horizontal and vertical rib structure, which is used to ensure the rigidity of the universal base of the zero-point positioning system. The structure of the universal base of the zero-point positioning system is as follows: Figures 2A to 2C As shown, in this embodiment, the universal base 1 of the zero-point positioning system includes a flat surface steel plate 101, a cast hanging rod 102, a zero-point locator 103, transverse ribs 104 and longitudinal ribs 105, wherein the transverse ribs 104 and the longitudinal ribs 105 are located at the lower part of the universal base 1 of the zero-point positioning system, and the flat surface steel plate 101 is located at the upper part of the universal base 1 of the zero-point positioning system. The transverse ribs 104 and the longitudinal ribs 105 support the flat surface steel plate 101 to ensure the rigidity of the universal base 1 of the zero-point positioning system. The zero-point locator 103 is arranged on the upper surface of the flat surface steel plate 101 and is evenly distributed horizontally and vertically. On the side wall of the universal base 1 of the zero-point positioning system, the cast hanging rod 102 is provided at the intersection of the transverse ribs 104 and the longitudinal ribs 105.

[0036] 2. Distribution of skin support assembly blocks

[0037] The existing flexible multi-point technology uses multiple support columns evenly spaced horizontally and vertically to support and fix the skin. In this embodiment, the assembled skin milling fixture uses working surface assemblies with fixed heights to support the skin. Each set of assemblies is designed according to the specific skin structure and shape, which can more fully consider the position where the skin shape needs to be cut, as well as the area where the openings inside the skin need to be avoided. The skin milling process is mainly to cut the skin shape, and the main cutting area is the periphery of the skin. Therefore, the supporting assemblies required in these areas are densely distributed and as large as possible. Both the internal and external removal areas of the skin should be supported and fixed, so that the shaking of the skin during milling can be effectively controlled. Support assemblies should be designed on both sides of the skin edge line, and the horizontal spacing of the support assemblies on both sides of the edge line is used as the milling cutter avoidance groove. The supporting assemblies designed in the internal area of ​​the skin are mainly used to support the skin. They do not need to be very dense, but they must be evenly positioned and interchangeable. At the same time, the through holes inside the skin can also be avoided by using the horizontal spacing of the support blocks. The distribution of the support blocks of a certain skin part is as follows: Figure 3 As shown, in this embodiment, a skin support assembly block 2 is set on the universal base 1 of the zero-point positioning system, wherein the skin support assembly block 2 is set according to the structure and shape of the skin to be processed, and the distribution of the skin support assembly blocks 2 at the peripheral position of the skin to be processed is denser than the distribution of the skin support assembly blocks 2 at the internal position of the skin to be processed, so that the skin support assembly blocks 2 are interchangeable and the jitter of the skin to be processed during milling is controlled.

[0038] 3. Position design of zero point positioning pin

[0039] In the zero-point positioning system, the positioning of the workpiece is multi-unit positioning, such as 2-unit zero-point positioning, 4-unit zero-point positioning, 6-unit zero-point positioning, and even 8-unit zero-point positioning, which can be determined according to the size of the workpiece. The assembled skin milling fixture supports the skin surface in blocks to form multiple supporting assembly blocks. In order to meet the diversity of the skin and the interchangeability of each supporting assembly block, the external dimensions of each supporting assembly block should be as small as possible, and 2-unit zero-point positioning is mostly used. In special cases, 4-unit zero-point positioning can be used. Figure 3 As shown, the skin support blocks all use two-unit zero-point positioning, and there are support blocks in both horizontal and vertical directions. After the positions of each skin support block of the assembled milling fixture are determined, the installation position of the zero-point positioning pin is designed at the corresponding position on the bottom of each support block based on its correspondence with the zero-point positioning system.

[0040] 4. Manufacturing of assembled skin milling fixture

[0041] The assembled skin milling fixture decomposes the overall curvature profile of the skin into multiple small-sized assembly blocks. It no longer requires a large five-axis CNC machining center for overall processing. A small CNC milling machine can process each supporting assembly block, and multiple devices can perform processing simultaneously.

[0042] In order to ensure the accuracy of the processing of each supporting assembly block of the assembled skin milling fixture, one or more sets of small zero point positioning systems can be prepared in advance. The center distance of the zero point locator on the zero point positioning system must be consistent with the center distance of the zero point locator on the zero point positioning system. Figures 2A to 2C The center distances of the zero point locators on the universal base of the large zero point positioning system shown are identical.

[0043] After the blanks are prepared for each supporting assembly of the assembled skin milling fixture, the zero-point locating pin mounting holes are first machined on the bottom surface. The zero-point locating pins are then installed. A small zero-point positioning system is then used for rapid positioning on the CNC milling equipment. Finally, the working surfaces are CNC milled. This machining method not only ensures machining accuracy but also improves efficiency.

[0044] 5. Other auxiliary designs

[0045] In addition to supporting the skin, each supporting assembly block of the assembled skin milling fixture also has the function of positioning and fixing the skin.

[0046] The skin can be positioned using locating pins. Pre-machined locating pin holes are then installed on the corresponding support assembly blocks of the assembled skin milling fixture. Once the skin locating pin holes are connected to the locating pins on the support assembly blocks, the skin is positioned.

[0047] There are two ways to fix the skin: the first way is to use magnetic materials to process the various supporting assembly blocks of the assembled skin milling and cutting fixture. After the skin is positioned, the skin is fixed by the adsorption force between the magnets and the supporting assembly blocks; the second way is to install a vacuum adsorption device on each supporting assembly block of the assembled skin milling and cutting fixture. After the skin is positioned, the skin is fixed by the vacuum adsorption force.

[0048] Example

[0049] 1. According to the scientific research and production tasks, the shape milling of the fuselage skin parts in a passenger aircraft project required the design of an assembled skin milling fixture. There were two skin parts in total, which were the skins in the same position on two models of aircraft. Both were single-curvature skins with the same curvature:

[0050] Part 1: Material brand: 2198-T3S, material specification: 0.125 inches,

[0051] Dimensions (net length × net width × chord height): 3197 × 1603 × 158 mm;

[0052] Part 2: Material grade: 2198-T3S, material specification: 0.125 inches,

[0053] Dimensions (net length × net width × chord height): 5330 × 1603 × 158 mm.

[0054] 2. Comparing the two skin parts' structures reveals that, aside from their length, all other dimensions are identical. The added tabs are the same size, and after aligning the skins' trailing edges, all internal holes in the two skins overlap. Therefore, with the trailing edges of the two skins aligned, a single 3D manufacturing dataset is generated.

[0055] 3. Based on the three-dimensional manufacturing data set, the distribution design of each skin support assembly block 2 of the assembled skin milling fixture is carried out, and the following is obtained: Figure 3 The distribution results of .

[0056] 4. Each supporting assembly block of the assembled skin milling fixture is processed separately, and a small zero-point positioning system is used to perform CNC milling of the curved working surface.

[0057] 5. Number each supporting assembly block of the processed assembled skin milling fixture and design an installation layout to avoid installation errors.

[0058] 6. Install and secure the various supporting blocks of the assembled skin milling fixture to the zero-point positioning system according to the installation layout diagram. Since the zero-point positioning system has been fixed and aligned with the five-axis CNC machining, alignment is achieved after the milling fixture is installed.

[0059] 7. Hoist the semi-finished skin parts to be processed onto the five-axis CNC machining center and position them using positioning pins and the assembled skin milling fixture. After positioning, the skin is fixed using the adsorption force of magnets.

[0060] 8. Drill holes and mill edges of the skin according to the programmed processing procedure.

[0061] 9. After processing, the skin will be disassembled and finalized using the inspection jig. The skin shape is accurate and the fitting gap meets the requirements and can be delivered.

[0062] The descriptions presented in the above exemplary embodiments are only intended to illustrate the technical solutions of the present invention and are not intended to be exhaustive or to limit the present invention to the precise forms described. Obviously, it is possible for a person of ordinary skill in the art to make many changes and variations based on the above teachings. The exemplary embodiments are selected and described in order to explain the specific principles of the present invention and its practical applications, so that other persons skilled in the art can easily understand, implement and utilize the various exemplary embodiments of the present invention and its various selected forms and modified forms. The scope of protection of the present invention is intended to be defined by the appended claims and their equivalents.

Claims

1. An assembled skin milling fixture, characterized in that: The assembled skin milling fixture comprises a universal base (1) of a zero-point positioning system and a skin support assembly block (2), wherein: The universal base (1) of the zero-point positioning system comprises a flat steel plate (101), a cast suspension rod (102), a zero-point locator (103), transverse ribs (104) and longitudinal ribs (105), wherein the transverse ribs (104) and longitudinal ribs (105) are located at the lower part of the universal base (1) of the zero-point positioning system, the flat steel plate (101) is located at the upper part of the universal base (1) of the zero-point positioning system, the transverse ribs (104) and longitudinal ribs (105) support the flat steel plate (101) to ensure the rigidity of the universal base (1) of the zero-point positioning system, and the zero-point locator (103) is arranged on the upper surface of the flat steel plate (101) in a uniformly distributed manner in the horizontal and vertical directions; a cast suspension rod (102) is arranged on the side wall of the universal base (1) of the zero-point positioning system at the intersection of the transverse ribs (104) and the longitudinal ribs (105); A skin support assembly block (2) is arranged on the universal base (1) of the zero-point positioning system, wherein the skin support assembly block (2) is arranged according to the structure and shape of the skin to be processed, and the skin support assembly blocks (2) are distributed more densely at the peripheral position of the skin to be processed than at the internal position of the skin to be processed, so that the skin support assembly blocks (2) are interchangeable and the shaking of the skin to be processed during milling is controlled; a positioning pin is also arranged on the skin support assembly block (2), and the positioning pin hole of the skin to be processed is connected to the positioning pin on the skin support assembly block (2) to position the skin; The skin support assembly block (2) is made of magnetic material, so as to fix the skin to be processed by utilizing the adsorption force between the magnet and the skin support assembly block (2); Alternatively, a vacuum adsorption device is provided on the skin supporting assembly block (2), and after the skin to be processed is positioned, the skin to be processed is fixed by utilizing the vacuum adsorption force.

2. A method for manufacturing skin using the assembled skin milling fixture according to claim 1, characterized in that: It includes the following steps: Step 1: construct a three-dimensional manufacturing data set according to the skin to be processed; Step 2: Design the distribution of each supporting assembly block (2) of the assembled skin milling fixture according to the three-dimensional manufacturing data set constructed in step 1); Step 3, processing each skin support assembly block (2) of the assembled skin milling fixture obtained in step 2) respectively, and performing CNC milling processing of the curved working surface through a zero point positioning system; Step 4: numbering each skin support assembly block (2) of the assembled skin milling fixture obtained in step 3), and designing an installation layout diagram to avoid installation errors; Step 5: Install and fix each skin support assembly block (2) of the assembled skin milling fixture on the universal base (1) of the zero point positioning system; Step 6: hoist the semi-finished skin parts to be processed onto the five-axis CNC machining center, and use positioning pins and an assembled skin milling fixture to position them; after positioning, use the adsorption force of the magnet to fix the skin to be processed; Step 7: Drill holes and mill edges of the skin to be processed; Step 8: Remove the skin after processing.

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