CN118832390A - Machining method for variable-thickness omega-shaped thin-wall part - Google Patents

Abstract

The present invention belongs to the technical field of sheet metal parts processing for aircraft, and relates to a method for processing thin-walled parts with variable thickness "Ω" shape. The processing method uses a newly designed set of bending dies for auxiliary forming, and uses the process flow of "milling and cutting - gate pressure forming - roll bending forming - manual forming - heat treatment" to replace the process flow of traditional mechanical processing. The present invention is scalable and can be widely used in the manufacture of thin-walled sheet metal parts with variable thickness and large curvature. Compared with the traditional process flow of mechanical processing, the sheet metal processing has a small cutting amount, high material utilization rate, low processing cost, and high part strength.

Description

A processing method for variable thickness "Ω" shaped thin-walled parts

Technical Field

The invention belongs to the technical field of aviation aircraft sheet metal parts processing, and relates to a processing method for a variable thickness "Ω"-shaped thin-walled part.

Background Art

In the aviation manufacturing industry at home and abroad, there are skeleton and pressure plate parts in the aircraft canopy. The typical structure is large size, double curvature, small thickness, and both the inner and outer surfaces have thickness variation characteristics. At present, the main processing methods for large curvature and variable thickness thin-walled parts in the industry are mechanical processing and chemical milling. Among them, the chemical milling process is simple, low cost, and widely used. However, due to the low precision of its chemical milling process, the area that does not meet the size needs additional processing or even directly causes the product to be scrapped. If the traditional machining process is adopted, it is necessary to apply for a special machining and milling fixture. The tooling design and manufacturing cycle is long and the cost is huge. In addition, weak rigid parts are prone to cutting deformation during the machining process, and the external dimensions of the parts are difficult to guarantee. Therefore, there are problems such as long cycle, high cost, high processing difficulty, high labor intensity, low part precision, and poor surface quality in the production of such parts. In addition, the thin-walled parts obtained by mechanical processing are heavy and low in strength. They are prone to fatigue damage during use, which makes it difficult to meet the requirements of lightweight and long life of advanced aircraft.

Summary of the invention

The purpose of the present invention is to invent a forming device and processing method for variable thickness "Ω" shaped thin-walled parts. The processing method uses a newly designed set of bending dies to assist in forming, and uses the process flow of "milling and cutting - gate pressure forming - roll bending forming - manual forming - heat treatment" to replace the process flow of traditional mechanical processing. The bending die used in the present invention can solve the problems of difficult control of the profile, difficult heat treatment deformation and trimming, and poor surface quality during the forming process of variable thickness "Ω" shaped thin-walled parts, so as to achieve the purpose of improving the accuracy of the part shape, improving the surface quality, and reducing labor intensity. The technical solution is scalable and can be applied to the manufacture of arc-shaped large curvature thin-walled sheet metal parts.

In order to achieve the above object, the technical solution of the present invention is:

A method for processing a variable thickness "Ω"-shaped thin-walled part, the steps are as follows:

The first step is milling and cutting.

Milling is performed using CNC machine tools, with the three-dimensional unfolded data set obtained in the unfolded state of the part as the processing basis, and all the surfaces in the unfolded state are milled out for subsequent forming; the surfaces include outer edges and thickness.

After the sheet metal is milled, the end surface is filed and deburred with files and sandpaper. The profile and edge are inspected with a digital measuring machine to ensure that the shape and thickness limit deviation, surface roughness, etc. meet the standards. The use of mathematical calculations, geometric analysis, and physical verification can improve the accuracy of the three-dimensional unfolding data set, which is conducive to subsequent forming.

The second process is gate pressure forming.

The purpose of the gate forming process is to make the two ends of the milled flat blank into an "L" shape for subsequent roll bending. This process can be completed using a CNC bending machine, a universal tool, and a template. The template contains the bending height and bending angle marks;

The third process is rolling forming.

The purpose of roll bending is to make the straight section of the blank into the arc of the approximate shape of the part, so as to facilitate the subsequent manual trimming to the final shape. Since the part has a double curvature shape, the rolling machine is used as the equipment for rolling bending, the reverse cutting outer template is used as the basis, and the equal percentage line method is used for rolling bending. The flexible rolling bending technology can better control the straight section and improve the uniformity of deformation.

The fourth process is manual forming.

The tooling used for manual forming is a "bending die", which includes: a carcass, a base plate, base plate screws, a positioning block, a positioning pin, a positioning screw, a clamp, a clamping pin, a clamping screw, a part edge line, a reference hole, and a lifting eye screw.

The tooling "bending die" is used to form the parts that have been formed by gate pressure forming and roll bending to the final shape, and is also used for trimming heat treatment deformation. According to the assembly relationship of the parts in the aircraft cockpit, the tooling adopts a "concave" structure. In order to reduce the difficulty of processing, the carcass is composed of carcass I and carcass II, and the profile is designed according to the theoretical profile of the outer side of the part. The bottom plate is used to fix the carcass, with a thickness of about 50mm. It is fixed to the carcass with bottom plate screws to form the main structure of the tooling. According to the structural characteristics of the parts and the forming requirements, 3 positioning blocks are added to the carcass. The positioning blocks include positioning blocks I, II and III, which are used to determine the position of the parts during forming and trimming to prevent the parts from moving on the tooling and causing the profile to shift in the width direction. Among them, positioning blocks I and III are located on the same side of the part and at the two ends, and positioning block II is set in the middle of the other side of the part. The working edge of the positioning block is close to the edge of the part. After being accurately positioned with carcass I and carcass II by positioning pins, it is fixed with positioning screws. According to the shape characteristics of the parts, the parts need to be sheet metal formed section by section during trimming. In order to avoid the parts from moving in the length direction, the clamps are evenly set at the arc-shaped curvature of the parts. The clamps include clamps I, II and III. The clamps adopt a pressure plate structure, and the working part can be raised and lowered. The threaded structure can facilitate the clamping and unloading of parts. The clamps use a clamping pin to determine the position on the tire body and are fixed with a clamping screw. The edge line of the part is generated according to the shape of the part, which is used for the operator to quickly determine the position of the part during the forming process, and to monitor in real time whether the position of the part is offset to avoid errors caused by over-tolerance. A reference hole with a size of Φ10H7 is set on each side of the tire body, which is used as a tooling processing reference and inspection reference. The eye screw is installed on the side of the tire body for tooling lifting and handling. The above structure is made of Q235-A.F with a manufacturing tolerance of ±0.1.

The fifth process is heat treatment.

The purpose of heat treatment is to eliminate the internal stress after forming, improve the plasticity and organizational stability of the material, and obtain better comprehensive performance. After the heat treatment is completed, a "bending die" is used to trim the deformation.

Beneficial effects of the present invention:

In the manufacturing of aviation parts, the process of "milling and cutting - gate pressure forming - roll bending - manual forming - heat treatment" is used to replace the traditional mechanical processing process, and the newly designed bending die is used to assist in the shape and surface control of the formed parts, which improves the manufacturing accuracy of the aircraft cockpit cover variable thickness "Ω" shaped thin-walled parts, and the use of sheet metal processing improves the strength of the parts. In the newly designed process, the parts processing is mainly carried out by bending machines and roll bending machines, and the parts manufacturing is highly mechanized, the processing efficiency is high, and the quality is good.

The invention is scalable and can be widely used in manufacturing thin-walled sheet metal parts with variable thickness and large curvature. Compared with the traditional process flow using mechanical processing, the sheet metal processing has a small cutting amount, a high material utilization rate, a low processing cost, and a high part strength.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a typical parts appearance diagram;

Figure 2 is a schematic diagram of a milled part;

Figure 3 is a schematic diagram of a gate pressure member;

FIG4 is a schematic diagram of roll bending;

Fig. 5 is a structural diagram of a bending die;

FIG6( a ) is a front view of the bending mold structure;

Fig. 6(b) is a cross-sectional view of the bending mold structure A-A;

Figure 6(c) is a side view of the bending mold structure.

In the figure: 1. carcass; 2. base plate; 3. base plate screw; 4. positioning block; 5. positioning pin; 6. positioning screw; 7. clamp; 8. clamping pin; 9. clamping screw; 10. part edge line; 11. reference hole; 12. eye screw.

Specific embodiments

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which this application can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the effects and purposes that can be achieved by this application.

Embodiment 1:

This forming device and processing method mainly consists of milling cutting, gate pressure forming, roll bending, manual trimming, heat treatment and other processes. It can realize the manufacture of variable thickness "Ω"-shaped thin-walled parts and can reduce material costs and improve part structural strength. The specific steps are briefly introduced as follows with examples.

As shown in Figures 1 to 6, the processing method of variable thickness "Ω" shaped thin-walled parts is based on milling, gate forming, roll bending, manual trimming and heat treatment, etc., and is achieved by using a "bending die". The "bending die" structure includes: carcass 1, base plate 2, base plate screw 3, positioning block 4, positioning pin 5, positioning screw 6, clamp 7, clamp pin 8, clamp screw 9, part edge line 10, reference hole 11, eye screw 12.

The tooling "bending die" is used to form the parts that have been formed by gate pressure forming and roll bending to the final shape, and is also used for the trimming of heat treatment deformation. According to the assembly relationship of the parts in the aircraft cockpit, the tooling adopts a "concave" structure. In order to reduce the difficulty of processing, its structural carcass 1 consists of two parts, I and II, and the profile is designed according to the theoretical shape of the outer side of the part. The bottom plate 2 is used to fix the carcass 1, with a thickness of 50mm, and is fixed to the carcass 1 by the bottom plate screws 3, thus forming the main structure of the tooling. According to the structural characteristics of the parts and the forming requirements, three positioning blocks 4 are added to the carcass 1 to determine the position of the parts during forming and trimming, and to prevent the parts from moving on the tooling and causing the profile to shift in the width direction. Among them, the positioning blocks I and III are located on the same side of the part and at the two ends, and the positioning block II is set in the middle of the other side of the part. The working edge of the positioning block 4 is close to the edge of the part, and after being accurately positioned with the carcass 1 by the positioning pin 5, it is fixed with the positioning screw 6. According to the shape characteristics of the parts, the parts need to be sheet metal formed section by section during trimming. In order to avoid the parts from moving in the length direction, the clamps 7 are evenly arranged at the arc-shaped curvature of the parts. The clamps 7 include clamps I, II, and III. The clamps 7 adopt a pressure plate structure, and the working part can be raised and lowered. The threaded structure can facilitate the clamping and unloading of parts. The clamps 7 use a clamping pin 8 to determine the position on the carcass 1 and are fixed with a clamping screw 9. The edge line 10 of the part is generated according to the shape of the part, which is used for the operator to quickly determine the position of the part during the forming process, and to monitor whether the position of the part is offset to avoid errors caused by over-tolerance. A reference hole 11 is set on each side of the carcass 1, with a size of Φ10H7, which is used as a tooling processing reference and inspection reference. The eye screws 12 are installed on the sides of the carcass I and carcass II for tooling hoisting and transportation.

The above structure is made of Q235-A.F, with a surface manufacturing tolerance of ±0.1mm, and the roughness of the part surface area and the holes on the drilling template for installing the drill sleeve is not higher than Ra1.6.

Embodiment 2:

The processing method of a variable thickness "Ω"-shaped thin-walled part comprises the following steps:

Step 1: Milling and cutting.

Aluminum alloy sheets with a thickness of δ6.0 and a size of 2500mm×500mm were processed, of which 2500mm was in the fiber direction. Milling was performed using a CNC machine tool, and the three-dimensional unfolded data set obtained in the unfolded state of the part was used as the processing basis. All the outer edges and thickness of the profiles in the unfolded state were milled out for subsequent forming.

After the sheet metal is milled, the end surface is filed and deburred with files and sandpaper. The profile and edge are inspected with a digital measuring machine to ensure that the shape and thickness limit deviation, surface roughness, etc. meet the standards.

Step 2: Gate pressure forming.

The purpose of the gate forming process is to make the two ends of the milled flat blank into an "L" shape for subsequent stretch bending. This process can be completed using a CNC bending machine, a universal tool, and a template containing the bending height and bending angle marks. First, select a suitable gate knife and the corresponding knife pillow notch according to the bending radius and bending angle of the part section, and install the gate knife on the fixed block of the CNC bending machine to connect the gate knife with the slider of the bending machine. According to the bending height and bending angle shown on the template, set the position of the rear baffle of the bending machine and the bottom dead center of the slider stroke. Then, feed the flat blank in, the bottom surface of the sheet fits with the upper surface of the knife pillow, and the end face fits with the rear baffle. Step on the mold closing switch of the equipment, and the slider slides down to close the mold. Release the mold closing switch, take out the part after the slider moves up, measure the bending height and bending angle. If the size meets the requirements, enter the subsequent process. If the size is unqualified, adjust the position of the rear baffle of the bending machine and the bottom dead center of the slider stroke and re-form until the size is qualified;

Step three: rolling and bending.

The purpose of roll bending is to make the straight section of the blank into the arc of the approximate shape of the part, so as to facilitate the subsequent manual trimming to the final shape. Since the part has a double curvature shape, the rolling machine is used as the equipment for rolling bending, the reverse cutting outer template is used as the basis, and the equal percentage line method is used for rolling bending. During rolling bending, the three rollers remain parallel to each other, and the upper and lower positions of the upper roller are adjusted according to the curvature of the part, so as to realize the rolling deformation of the variable curvature cylindrical part. The equal percentage line method rolling method is to regard the part as approximately composed of several different radii R, and divide it into sections according to the radius R, and roll it in batches, that is, the curvature is rolled from small to large. During rolling bending, first set a fixed upper roller position so that the raw material is rolled into a single curvature shape as a whole; then adjust the position of the upper roller in the double curvature area of the part, and roll the area to obtain a local double curvature shape; after rolling all the double curvature positions of the part step by step, the overall double curvature shape of the part is obtained.

After the roll forming is completed, unload the roller pressure and lift the upper roller to a sufficient space to avoid interference and damage when taking out the parts.

Step 4: Manual forming.

First, place the "bending die" horizontally on the workbench, manually loosen the thread on the clamp 7, lift the clamp 7, and place the part with the "Ω" shape obtained through the processes of "milling and cutting-gate pressing-rolling forming" in the carcass 1. The two ends of the part are aligned with the edge line on the carcass 1 and are close to the positioning block I and the positioning block III. At this time, there is a gap between the arc-shaped area in the middle of the part and the tooling. Then, use a hammer, aluminum hammer and other tools to manually form the arc-shaped area with a gap in the middle. During the process, the position of the two ends of the part is ensured to be kept as uniform as possible without shifting. After the part is basically fitted with the tooling, keep the two ends aligned with the edge line on the carcass 1 and close to the positioning block I and the positioning block III, tighten the thread on the clamp 7, and fix the part in the "bending die". Finally, trim the overall surface of the part to ensure that the gap between the part and the carcass 1 is not greater than 0.5mm, and the deviation from the edge line is not greater than 0.1mm. After completing the above work, loosen the threads on the clamp 7, unload the part and place it on the platform, use a feeler gauge to check the flatness of the end face to ensure that the gap between it and the platform is no more than 1mm. If it is out of tolerance, the part needs to be re-clamped in the "bending die" for correction until its fitting gap, flatness and edge line meet the requirements.

Step five: heat treatment.

The parts obtained by manual trimming are quenched and heat treated to eliminate the internal stress after forming, improve the plasticity and organizational stability of the material, and obtain better comprehensive performance. After the parts are quenched, they are kept at room temperature for 120h-240h, and sent to the physical and chemical department for conductivity or hardness inspection according to the standard. The conductivity acceptance value is: 18.5MS/m-20MS/m. If the conductivity is unqualified, it is allowed to be accepted according to the hardness, and the acceptance value is ≥62HRB. If both the conductivity and hardness tests are unqualified, repeat the step of this step for heat treatment until the physical and chemical properties are qualified and then enter the subsequent process.

Step six: manual trimming.

The deformation produced during the heat treatment process is trimmed using a "bending die" in the same way as step 4.

Step 7: Parts surface treatment.

The parts are anodized and painted to improve their corrosion resistance.

Complete the above steps to obtain the final part.

Embodiment 3:

A method for processing a variable thickness "Ω"-shaped thin-walled part, the steps are as follows:

The first process is milling and cutting;

Milling is carried out by CNC machine tools, with the three-dimensional unfolded data set obtained in the unfolded state of the part as the processing basis, and all the profiles in the unfolded state are milled out for subsequent forming; the profiles include the outer edge and thickness;

After the sheet metal is milled, the end surface is filed and deburred with files and sandpaper; the profile and edge are inspected with a digital measuring machine to ensure that the shape and thickness limit deviation and surface roughness meet the standards; mathematical calculation, geometric analysis, and physical verification are used;

The second process is gate pressure forming;

The purpose of the gate forming process is to make the two ends of the milled flat blank into an "L" shape for subsequent roll bending. This process can be completed using a CNC bending machine, a universal tool, and a template. The template contains the bending height and bending angle marks.

The third process is rolling forming;

The purpose of roll bending is to make the straight section of the blank into the arc of the approximate shape of the part, so as to facilitate the subsequent manual trimming to the final shape; since the part has a double curvature shape, the rolling machine is used as the equipment for rolling bending, the reverse cutting external template is used as the basis, and the equal percentage line method is used for rolling bending; the flexible rolling bending technology is used to improve the uniformity of deformation;

The fourth process is manual forming;

The tooling used for manual forming is a "bending die".

The tooling "bending die" is used to form the parts that have been formed into a prototype by gate pressing and roll bending to the final shape, and is also used to trim the deformation caused by heat treatment; according to the assembly relationship of the parts in the aircraft cockpit, the tooling adopts a "concave" structure;

The fifth process is heat treatment;

After the heat treatment is completed, a "bending die" is used to trim the deformation.

The tooling "bending die" includes: a carcass 1, a base plate 2, a base plate screw 3, a positioning block 4, a positioning pin 5, a positioning screw 6, a clamp 7, a clamp pin 8, a clamp screw 9, a part edge line 10, a reference hole 11, and a lifting eye screw 12; the base plate 2 is used to fix the carcass 1, and is fixed to the carcass 1 by the base plate screw 3, and three positioning blocks 4 are added to the carcass 1, and the positioning blocks 4 include positioning blocks I, II, and III, and positioning blocks I and III are located on the same side of the part and at both ends, and positioning block II is set in the middle of the other side of the part; after precise positioning with the carcass I and II by the positioning pin 5, the positioning screw 6 is used to fix it; clamps 7 are evenly arranged at the arc-shaped curvature of the part, and the clamps 7 include clamps I, II, and III; the clamps 7 use clamping pins 8 to determine the position on the carcass 1 and are fixed with clamping screws 9.

The carcass 1 of the tooling "bending die" is composed of two parts, carcass I and carcass II, and the profile is designed according to the theoretical outer shape of the part.

The clamp 7 of the tooling "bending die" adopts a pressure plate structure.

A reference hole 11 is provided on each side of the carcass 1 of the tooling "bending die", and the size of the reference hole 11 is Φ10H7.

The tooling "bending die" is made of Q235-A.F with a manufacturing tolerance of ±0.1.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the implementation rules without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A method for processing a variable thickness "Ω"-shaped thin-walled part, characterized in that the steps are as follows: The first process is milling and cutting; Milling is carried out by CNC machine tools, with the three-dimensional unfolded data set obtained in the unfolded state of the part as the processing basis, and all the profiles in the unfolded state are milled out for subsequent forming; the profiles include the outer edge and thickness; After the sheet metal is milled, the end surface is filed and deburred with files and sandpaper; the profile and edge are inspected with a digital measuring machine to ensure that the shape and thickness limit deviation and surface roughness meet the standards; mathematical calculation, geometric analysis, and physical verification are used; The second process is gate pressure forming; The purpose of the gate forming process is to make the two ends of the milled flat blank into an "L" shape for subsequent roll bending. This process can be completed using a CNC bending machine, a universal tool, and a template. The template contains the bending height and bending angle marks. The third process is rolling forming; The purpose of roll bending is to make the straight section of the blank into the arc of the approximate shape of the part, so as to facilitate the subsequent manual trimming to the final shape; since the part has a double curvature shape, the rolling machine is used as the equipment for rolling bending, the reverse cutting external template is used as the basis, and the equal percentage line method is used for rolling bending; the flexible rolling bending technology is used to improve the uniformity of deformation; The fourth process is manual forming; The tooling used for manual forming is a "bending die". The tooling "bending die" is used to form the parts that have been formed into a prototype by gate pressing and roll bending to the final shape, and is also used to trim the deformation caused by heat treatment; according to the assembly relationship of the parts in the aircraft cockpit, the tooling adopts a "concave" structure; The fifth process is heat treatment; After the heat treatment is completed, a "bending die" is used to trim the deformation. 2. A method for processing a variable thickness "Ω"-shaped thin-walled part as claimed in claim 1, characterized in that the tooling "bending die" comprises: a carcass (1), a base plate (2), a base plate screw (3), a positioning block (4), a positioning pin (5), a positioning screw (6), a clamp (7), a clamping pin (8), a clamping screw (9), a part edge line (10), a reference hole (11), and a lifting eye screw (12); the base plate (2) is used to fix the carcass (1), and is fixed to the carcass (1) by the base plate screw (3), and 3 positioning screws are added to the carcass (1). Positioning blocks (4), the positioning blocks (4) include positioning blocks I, positioning blocks II and positioning blocks III, the positioning blocks I and positioning blocks III are located at the same side of the part and at the two end positions, and the positioning block II is arranged at the middle position of the other side of the part; after being accurately positioned with the carcass I and carcass II by using positioning pins (5), they are fixed by using positioning screws (6); pressers (7) are evenly arranged at the arc-shaped curvature of the part, the pressers (7) include pressers I, pressers II and pressers III; the pressers (7) use pressing pins (8) to determine the position of the pressers on the carcass (1), and are fixed by using pressing screws (9). 3. A method for processing a variable thickness "Ω"-shaped thin-walled part as described in claim 1 or 2, characterized in that the carcass (1) of the tooling "bending die" consists of two parts, carcass I and carcass II, and the profile is designed according to the theoretical shape of the outer side of the part. 4. A method for processing a variable thickness "Ω"-shaped thin-walled part as described in claim 1 or 2, characterized in that the clamp (7) of the tooling "bending die" adopts a pressure plate structure. 5. A method for processing a variable thickness "Ω"-shaped thin-walled part as described in claim 3, characterized in that the clamp (7) of the tooling "bending die" adopts a pressure plate structure. 6. A method for processing a variable thickness "Ω"-shaped thin-walled part as described in claim 1, 2 or 5, characterized in that a reference hole (11) with a size of Φ10H7 is provided on each side of the carcass (1) of the tooling "bending die". 7. A method for processing a variable thickness "Ω"-shaped thin-walled part as described in claim 3, characterized in that a reference hole (11) with a size of Φ10H7 is provided on each side of the carcass (1) of the tooling "bending die". 8. A method for processing a variable thickness "Ω"-shaped thin-walled part as described in claim 4, characterized in that a reference hole (11) with a size of Φ10H7 is provided on each side of the carcass (1) of the tooling "bending die". 9. A method for processing a variable thickness "Ω"-shaped thin-walled part as described in claim 1, 2 or 5, characterized in that the tooling "bending die" is made of Q235-A.F with a manufacturing tolerance of ±0.1. 10. A method for processing a variable thickness "Ω"-shaped thin-walled part as described in claim 1, 2 or 5, characterized in that the tooling "bending die" is made of Q235-A.F with a manufacturing tolerance of ±0.1.