A method for processing thin-walled parts of aluminum alloy middle frame

Abstract

The present invention discloses a method for machining thin-walled aluminum alloy mid-frame parts. The method primarily includes the following steps: inspecting incoming materials, making lifting holes, making front and back bolt holes and counterbores, rough machining of the B side, rough machining of the A side, aging treatment, fine-finishing the reference surface, removing a portion of the process table on the A side, fine-machining the A side, fine-milling the closed angle of the A side, fine-milling the B side, drilling, and blanking. For thin-walled aluminum alloy parts like these, a high-speed milling process and a vacuum chuck fixture are employed. The process overlap is optimized, and portions of the process table are removed and retained appropriately, effectively controlling part deformation and improving machining quality. The present invention addresses the technical issues of the prior art in machining thin-walled aluminum alloy mid-frame parts, such as the tendency for parts to warp and deform, the difficulty in releasing residual stress, and low machining efficiency.

Description

Technical Field

[0001] The present invention relates to the field of aviation parts manufacturing, and in particular to a method for processing thin-walled aluminum alloy middle frame parts. Background Art

[0002] 7050 aluminum alloy is widely used in the manufacturing of aviation parts due to its high strength, high toughness, high fatigue resistance, and corrosion resistance. However, the finished blank has high residual stress and is prone to deformation. The interruption of its internal fiber structure and the large amount of roughing removal during processing will affect the changes in the internal stress of the blank material, causing the part to deform. At this time, the reasonable release of internal stress plays a very important role. This requires the development of appropriate process plans and the use of reasonable processing methods to reduce and control the impact of factors such as the blank's natural deformation and stress release deformation on the finished part, thereby ensuring the various performance of the part.

[0003] In the prior art, an aluminum alloy frame part for a certain aircraft model has a large closed angle, deep cavity, thin wall, and double-sided frame structure. The material is 7050-T7451 AMS4050J, and the blank weighs 335kg. Due to its large weight, the thickness of the web, flange, and other dimensions of the part are thin, mostly around 2mm. In terms of the part structure, the middle bone position is not conducive to the release of stress after the part is roughed out. During the processing, the process design is unreasonable, the removal amount during the roughing process is uneven, and the stress release of the part is insufficient, which will cause the part to deform and indirectly affect the hole size of the normal hole on the part. The later stage of the bench work is also extremely difficult, and it is easy to produce local stress concentration, which is very likely to cause cold work hardening, cracks and fractures. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for processing thin-walled parts of an aluminum alloy middle frame, so as to solve the technical problems in the prior art that parts are prone to warping and deformation, residual stress is difficult to release, and processing efficiency is low.

[0005] To achieve the above object, the present invention provides a method for processing thin-walled aluminum alloy middle frame parts, comprising the following steps:

[0006] S1. Material preparation and pre-processing: inspect incoming materials, make lifting holes, make front and back bolt holes and bolt countersunk holes;

[0007] S2, rough machining: Use high-speed milling method to rough machine the B surface, then rough machine the A surface, and then perform aging treatment to release the residual stress of the workpiece;

[0008] S3, Finishing: After finishing the reference surface, use the repaired reference surface as the reference ground for finishing. Remove the process table and auxiliary support ribs on the A surface. Use a high-speed five-axis machining center to finish mill the closed angle area of ​​the A surface. When machining the B surface, use a vacuum clamp with a vacuum compressor to ensure that the surface fits the mold before finishing the B surface.

[0009] S4, drilling and blanking, and finishing to obtain the finished product.

[0010] Furthermore, S1 is further divided into the following steps:

[0011] S11. Incoming material inspection: prepare blanks that meet the parts processing requirements and check the status of the blanks, which are rectangular parallelepiped profiles made of aluminum alloy;

[0012] S12, making lifting holes: making lifting holes on both sides of the blank by benchwork, wherein the positions of the lifting holes avoid the reserved parts positions to avoid the scrapping of parts due to the making of the lifting holes;

[0013] S13. Making bolt holes and bolt countersunk holes on the front and back sides: Use the side-top method to clamp the blank, make bolt holes and bolt countersunk holes on the front and back sides, so that the screw holes are evenly distributed on the process boss, set bolt holes in local areas prone to warping and deformation, and process stress relief grooves at the same time to fully release the residual stress of the workpiece after rough machining;

[0014] Furthermore, the B surface is divided into a partially open area and a closed area of ​​the part, and auxiliary support bars are provided in the open area and the closed area; the A surface has a process table and auxiliary support ribs.

[0015] Furthermore, S2 further includes the following steps:

[0016] S21, rough machining of surface B: After removing part of the process table, the profile is fixed by screw clamping. The screw clamping is installed from the middle to both sides to avoid deformation and clamping errors of the parts caused by uneven force;

[0017] S22, rough machining of surface A: To support the subsequent part machining, rough machining of surface A retains some support bodies to reduce part deformation. Figure 7 As shown;

[0018] S23, aging treatment: Place the parts flat on the aging platform for a specified time (not less than 48 hours), in a natural state, without stress, to allow them to deform freely and fully release the residual stress of the workpiece.

[0019] Furthermore, rough machining adopts high-speed milling CNC machining, and the machining tool adopts a disposable replaceable blade tool holder. The diameter of the tool processing part is 25mm, the length is 25mm, the total length is 150mm, and the overhang after clamping is 85mm. The parameters of the milling elements are the number of revolutions 12000r / min, the feed rate 8500mm / min, and the cutting depth 2mm. The part's partially open area adopts the part's external cutting, and the part's partially closed area adopts the spiral cutting or oblique cutting, and the minimum bevel length is not less than 70% of the tool diameter. When editing the tool path of the CNC machine tool, the tool path at the part corner and the included angle must be set to R corner smooth transition to make the tool run smoothly during actual machining. After roughing, a 3mm allowance is left, and a large flow of coolant is used to wash away aluminum chips, reduce the cutting temperature, and reduce the influence of temperature on part deformation.

[0020] Furthermore, S3 also includes the following steps:

[0021] S31, fine-tuning the reference surface: After aging treatment, the part will be deformed due to the release of residual stress. When performing subsequent processing, do not directly use screws to forcefully change the deformation. After the forced locking process is completed, when the other side is processed, if the part still has a large deformation, fix it with glue at the bottom of the part or place an appropriate number of feeler gauges at the deformed hollow at the bottom to support it before performing the locking process.

[0022] S32, Finish milling of surface A: Use the repaired reference surface as the reference bottom surface for this sequence of finishing. Remove the process table and auxiliary support ribs on the A surface to provide sufficient tool avoidance space for subsequent processing of the closed angle area of ​​the A surface.

[0023] S33, Finish milling of surface B: Since part of the process table is removed during the machining of surface A, the process coordinates originally located at the bottom of the part are transferred to the middle of the part during the machining of surface B. Then, a profiling vacuum fixture is used, and a vacuum compressor is used to ensure surface fit. The transfer of coordinates and the coordination of the vacuum profiling fixture reduce the influence of web deformation on the finishing of the part, thereby improving machining accuracy.

[0024] Furthermore, the finish milling of surface A is carried out by using a high-speed five-axis machining center to finish mill the closed angle area of ​​surface A. First, a 16R3 aluminum milling cutter is used to roughen the closed angle as a whole, and then a fixed-axis cutting method is used to semi-finish and finish the side wall area of ​​the closed angle area in sequence; the cutting depth of the side edge cutting in the fixed tool axis direction is 1mm, and the cutting depth of the bottom angle R3 in the fixed tool axis direction is 0.25mm.

[0025] Based on the above technical solution, the present invention can produce the following beneficial effects:

[0026] The present invention provides a method for processing thin-walled parts of an aluminum alloy middle frame. Through processing analysis of thin-walled parts in an aluminum alloy frame, a high-speed milling processing scheme and a vacuum suction cup fixture are adopted for aluminum alloy thin-walled parts similar to this item. The process overlap is optimized to reasonably remove and retain part of the process table so that the deformation of the parts is effectively controlled, the processing quality is improved, and the stability of the processing state is enhanced. The method has the advantages of high cutting efficiency, good processing quality, and stable processing state.

[0027] At the same time, the reasonable release of stress and the reasonable transfer of process coordinates can effectively reduce the impact of part deformation on its processing itself, reduce the amount of benchwork and grinding, and the risk of correction; it also provides a reference value for the subsequent customization of process solutions for this type of parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural diagram of an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of the structure of side A of an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the structure of side B of an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of a lifting hole according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the processing of screw holes and stress grooves according to an embodiment of the present invention;

[0033] Figure 6 This is a partial enlarged view of the open area of ​​an embodiment of the present invention;

[0034] Figure 7 This is a partial enlarged view of the closed area of ​​an embodiment of the present invention;

[0035] Figure 8 This is a schematic diagram of the structure of the B side after clamping according to an embodiment of the present invention;

[0036] Figure 9 This is a diagram of the auxiliary rib structure on the B side after clamping according to an embodiment of the present invention;

[0037] Figure 10 This is a schematic diagram of the structure of surface A after clamping according to an embodiment of the present invention;

[0038] Figure 11 This is a structural diagram of the auxiliary support block on the A side after clamping according to an embodiment of the present invention;

[0039] Figure 12 This is a structural diagram of the auxiliary support body on the A side after clamping according to an embodiment of the present invention;

[0040] Figure 13This is a schematic diagram of a method for deforming and locking parts according to an embodiment of the present invention;

[0041] Figure 14 This is a schematic diagram of an embodiment of the present invention after some process tables and auxiliary bodies are removed;

[0042] Figure 15 Schematic diagram of clamping of a contoured vacuum clamp according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a method for processing thin-walled aluminum alloy middle frame parts of the present invention in conjunction with the accompanying drawings.

[0044] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] As shown in the figure, the present invention provides a method for processing thin-walled aluminum alloy middle frame parts, comprising the following steps:

[0046] S1. Material preparation and pre-processing: inspect incoming materials, make lifting holes, make front and back bolt holes and bolt countersunk holes;

[0047] S2, rough machining: Use high-speed milling method to rough machine the B surface, then rough machine the A surface, and then perform aging treatment to release the residual stress of the workpiece;

[0048] S3, Finishing: After finishing the reference surface, use the repaired reference surface as the reference ground for finishing. Remove the process table and auxiliary support ribs on the A surface. Use a high-speed five-axis machining center to finish mill the closed angle area of ​​the A surface. When machining the B surface, use a vacuum clamp with a vacuum compressor to ensure that the surface fits the mold before finishing the B surface.

[0049] S4, drilling and blanking, and finishing to obtain the finished product.

[0050] Furthermore, S1 is further divided into the following steps:

[0051] S11. Incoming material inspection: prepare blanks that meet the parts processing requirements and check the status of the blanks, which are rectangular parallelepiped profiles made of aluminum alloy;

[0052] S12, making lifting holes: making lifting holes on both sides of the blank by benchwork, wherein the positions of the lifting holes avoid the reserved parts positions to avoid the scrapping of parts due to the making of the lifting holes;

[0053] S13. Making bolt holes and bolt countersunk holes on the front and back sides: Use the side-top method to clamp the blank, make bolt holes and bolt countersunk holes on the front and back sides, so that the screw holes are evenly distributed on the process boss, set bolt holes in local areas prone to warping and deformation, and process stress relief grooves at the same time to fully release the residual stress of the workpiece after rough machining;

[0054] Furthermore, a method for processing thin-walled parts of an aluminum alloy middle frame is provided, characterized in that the B surface is divided into a local open area and a closed area of ​​the part, and auxiliary support bars are provided in the open area and the closed area; the A surface has a process table and auxiliary support ribs.

[0055] Furthermore, S2 further includes the following steps:

[0056] S21, rough machining of surface B: After removing part of the process table, the profile is fixed by screw clamping. The screw clamping is installed from the middle to both sides to avoid deformation and clamping errors of the parts caused by uneven force;

[0057] S22, rough machining of surface A: To support the subsequent part machining, rough machining of surface A retains some support bodies to reduce part deformation. Figure 7 As shown;

[0058] S23, aging treatment: Place the parts flat on the aging platform for a specified time (not less than 48 hours), in a natural state, without stress, to allow them to deform freely and fully release the residual stress of the workpiece.

[0059] Furthermore, rough machining adopts high-speed milling CNC machining, and the machining tool adopts a disposable replaceable blade tool holder. The diameter of the tool processing part is 25mm, the length is 25mm, the total length is 150mm, and the overhang after clamping is 85mm. The parameters of the milling elements are the number of revolutions 12000r / min, the feed rate 8500mm / min, and the cutting depth 2mm. The part's partially open area adopts the part's external cutting, and the part's partially closed area adopts the spiral cutting or oblique cutting, and the minimum bevel length is not less than 70% of the tool diameter. When editing the tool path of the CNC machine tool, the tool path at the part corner and the included angle must be set to R corner smooth transition to make the tool run smoothly during actual machining. After roughing, a 3mm allowance is left, and a large flow of coolant is used to wash away aluminum chips, reduce the cutting temperature, and reduce the influence of temperature on part deformation.

[0060] Furthermore, considering the impact of the part's own weight during subsequent machining, extension bars connected to the ribs were designed to provide critical support during the machining of side A. Also, considering that retaining a large area of ​​rib extension would increase rib tensile stress, the extended auxiliary ribs were designed as nine independent structures. This provides excellent support while effectively reducing deformation during side A machining.

[0061] Furthermore, S3 also includes the following steps:

[0062] S31, fine-tuning the reference surface: After aging treatment, the part will be deformed due to the release of residual stress. When performing subsequent processing, do not directly use screws to forcefully change the deformation. After the forced locking process is completed, when the other side is processed, if the part still has a large deformation, fix it with glue at the bottom of the part or place an appropriate number of feeler gauges at the deformed hollow at the bottom to support it before performing the locking process.

[0063] S32, Finish milling of surface A: Use the repaired reference surface as the reference bottom surface for this sequence of finishing. Remove the process table and auxiliary support ribs on the A surface to provide sufficient tool avoidance space for subsequent processing of the closed angle area of ​​the A surface.

[0064] S33, Finish milling of surface B: Since part of the process table is removed during the machining of surface A, the process coordinates originally located at the bottom of the part are transferred to the middle of the part during the machining of surface B. Then, a profiling vacuum fixture is used, and a vacuum compressor is used to ensure surface fit. The transfer of coordinates and the coordination of the vacuum profiling fixture reduce the influence of web deformation on the finishing of the part, thereby improving machining accuracy.

[0065] Furthermore, the finish milling of surface A is carried out by using a high-speed five-axis machining center to finish mill the closed angle area of ​​surface A. First, a 16R3 aluminum milling cutter is used to roughen the closed angle as a whole, and then a fixed-axis cutting method is used to semi-finish and finish the side wall area of ​​the closed angle area in sequence; the cutting depth of the side edge cutting in the fixed tool axis direction is 1mm, and the cutting depth of the bottom angle R3 in the fixed tool axis direction is 0.25mm.

[0066] It will be appreciated that the present invention has been described with reference to certain embodiments, and those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. Furthermore, under the teachings of the present invention, these features and embodiments may be modified to suit specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A method for processing thin-walled parts of an aluminum alloy middle frame, characterized in that: The steps include: S1. Material preparation and pre-processing: inspect incoming materials, make lifting holes, make front and back bolt holes and bolt countersunk holes; S2. Rough machining: Use high-speed milling to rough-machining the B side, then rough-machining the A side, and then aging treatment to release the residual stress of the workpiece; the rough machining adopts high-speed milling CNC machining, and the machining tool adopts a disposable replaceable blade type tool holder, the tool machining part diameter is 25mm, the length is 25mm, the total length is 150mm, and the overhang after clamping is 85mm; the parameters of the milling elements are speed 12000r / min, feed rate 8500mm / min, and cutting depth 2mm; the part is cut from the outside of the part for the partially open area, and the part is cut with a spiral cut or an oblique cut for the partially closed area, and the minimum bevel length is not less than 70% of the tool diameter; when editing the tool path of the CNC machine tool, the tool path at the part corner and the included angle must be set to R corner smooth transition, so that the tool can run smoothly during actual machining; leave a 3mm allowance after roughing, and use a large flow of coolant to wash away aluminum chips, reduce the cutting temperature, and reduce the influence of temperature on part deformation; S3. Finishing: After finishing the reference surface, use the repaired reference surface as the reference surface for finishing. Remove the process table and auxiliary support ribs on the A surface. Use the high-speed five-axis machining center to finish mill the closed angle area of ​​the A surface. When machining the B surface, use the vacuum clamp with a vacuum compressor to ensure that the surface fits the mold before finishing the B surface. S31, fine-tuning the reference surface: After aging treatment, the parts are deformed due to the release of residual stress. When performing subsequent processing, glue is applied to the bottom of the parts to fix them or an appropriate number of feeler gauges are placed on the deformed hollow parts at the bottom to support them before tightening. S32, Finish milling of surface A: Use the repaired reference surface as the reference bottom surface for this sequence of finishing. Remove the process table and auxiliary support ribs on the A surface to provide sufficient tool avoidance space for subsequent processing of the closed angle area of ​​the A surface. S33, Finish Milling of Side B: Because part of the process table is removed during the machining of Side A, the process coordinates originally located on the bottom of the part are moved to the middle of the part during the machining of Side B. A profiling vacuum fixture is then used, and a vacuum compressor is used to ensure surface fit. The coordinate transfer and the vacuum profiling fixture reduce the impact of web deformation on part finishing, improving machining accuracy. S4, drilling and blanking, and finishing to obtain the finished product; The fine milling of surface A is to use a high-speed five-axis machining center to fine mill the closed angle area of ​​surface A. First, a 16R3 aluminum milling cutter is used to roughen the closed angle as a whole, and then a fixed-axis cutting method is used to semi-finish and finish the side wall area of ​​the closed angle area in sequence; the side edge cutting has a fixed tool axis cutting depth of 1mm, and the bottom angle R3 has a fixed tool axis cutting depth of 0.25mm.

2. The method for processing thin-walled aluminum alloy middle frame parts according to claim 1, characterized in that: The S1 is further divided into the following steps: S11. Incoming material inspection: prepare blanks that meet the parts processing requirements and check the status of the blanks, which are rectangular parallelepiped profiles made of aluminum alloy; S12, making lifting holes: making lifting holes on both sides of the blank by benchwork, wherein the positions of the lifting holes avoid the reserved parts positions to avoid the scrapping of parts due to the making of the lifting holes; S13. Make bolt holes and bolt countersunk holes on the front and back sides: Use the side-top method to clamp the blank, make bolt holes and bolt countersunk holes on the front and back sides, make the screw holes evenly distributed on the process boss, set bolt holes in the local areas prone to warping and deformation, and process stress relief grooves at the same time to fully release the residual stress of the workpiece after rough machining.

3. The method for processing thin-walled aluminum alloy middle frame parts according to claim 1, characterized in that: The method for processing thin-walled parts of an aluminum alloy middle frame is characterized in that the B surface is divided into a local open area and a closed area of ​​the part, and auxiliary support bars are provided in the open area and the closed area; the A surface has a process table and auxiliary support ribs.

4. The method for processing thin-walled aluminum alloy middle frame parts according to claim 1, characterized in that: The method for processing thin-walled parts of an aluminum alloy middle frame is characterized in that S2 further includes the following steps: S21, rough machining of surface B: After removing part of the process table, the profile is fixed by screw clamping. The screw clamping is installed from the middle to both sides to avoid deformation and clamping errors of the parts caused by uneven force; S22, rough machining of surface A: To support the subsequent part machining, rough machining of surface A retains part of the support body to reduce part deformation; S23, aging treatment: Place the parts flat on the aging platform for no less than 48 hours, in a natural state, without stress, to allow them to deform freely and fully release the residual stress of the workpiece.

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