A method for high-precision hole making of multi-ear type aircraft structure

Abstract

This invention pertains to aircraft assembly technology and relates to a high-precision drilling method for multi-lug aircraft structures. The high-precision rigid fixture of this invention offers the following advantages in improving the precision of multi-lug external beam joints for helicopters, ensuring processing quality, and increasing production efficiency: final hole accuracy is no less than H8 grade; hole wall surface finish is no less than Ra1.6; coaxiality of the front and rear holes of the same lug is no less than φ0.04mm; relative positional accuracy of the four sets of lug interfaces on each side is no less than 0.1mm; the number of drilling stages is reduced by at least 50% compared to traditional methods; drilling time is reduced by at least 40% compared to traditional methods; drilling tool life is long, reducing tool costs by 95%, resulting in superior economic efficiency; the drilling quality is consistent and stable, meets ergonomic requirements, reduces operator workload, and is easy to operate. This method has been validated through long-term application and exhibits high reliability and stable quality, making it widely applicable.

Description

Technical Field

[0001] This invention belongs to aircraft assembly technology and relates to a high-precision hole-making method for multi-lug aircraft structures. Background Technology

[0002] During missions, shipborne helicopters operate in high-temperature, high-humidity, and high-salt environments for extended periods, and the multi-ear external pylon joints, a critical structural component of these helicopters, remain constantly exposed. To ensure good corrosion resistance, strength, toughness, and ductility, difficult-to-machine materials such as 1Cr17Ni3A martensitic-ferritic stainless steel are often selected. In helicopter manufacturing, the precision machining of large-diameter multi-ear external pylon joints after airframe assembly is a critical process. Precision machining ensures accurate dimensions and a smooth surface for the joints, eliminates assembly stress to guarantee a tight fit with weapons, improves wear and corrosion resistance, extends service life, and ensures the reliability and stability of shipborne helicopters during long-term operation. Summary of the Invention

[0003] The purpose of this invention is:

[0004] In the traditional process of finishing multi-ear external beam joints, strip-shaped cutting chips are easily generated, causing scratches on the inner wall of the joint and resulting in excessive hole roughness. The inconsistent processing parameters such as feed rate can easily lead to excessive coaxiality of the front and rear holes of the fork lugs. The tooling structure lacks rigidity, making it difficult to guarantee the relative positional accuracy between the fork lug joints. The multi-ear external beam joint has a large hole diameter, often requiring the use of level 9 drilling, which is time-consuming and inefficient. When drilling manually, the operator needs to maintain a certain posture and continuously push the pneumatic drill forward along the drill jig, resulting in a large reaction force and causing fatigue and injury to the operator's waist and shoulders, which does not meet ergonomic requirements. The tools used for level 9 drilling are expensive and uneconomical. All of these factors restrict the finishing quality and efficiency of the holes in helicopter multi-ear external beam joints.

[0005] To address the above problems, this invention proposes a high-precision hole-making method for multi-lug aircraft structures. It combines high-precision, simple, and flexible rigid fixtures with advanced portable boring and reaming tools, and comprehensively improves the process flow, tool configuration, and process parameters to achieve high-quality and high-efficiency engineering applications, breaking through the difficulty of precision machining of holes in multi-lug aircraft structures.

[0006] The technical solution of this invention is:

[0007] This invention proposes a high-precision hole-making method for multi-lug aircraft structures, specifically including the following:

[0008] 1) Product rack positioning: The large helicopter component with integrated multi-fork lug structure is rack positioned on a high-precision rigid fixture. The high-precision rigid fixture mainly includes a main positioner 1, fork lug positioner 2, equipment drill template 3, overall frame 4, and sliding device 5. The main positioner 1 is fixed to the upper part of the overall frame 4; the fork lug positioner 2 is fixed to both sides of the overall frame 4; the equipment drill template 3 is installed on both sides of the overall frame 4, and the sliding device 5 is installed on the lower side of the overall frame 4. The main positioning reference is the upper structure of the large helicopter component, and the main reduction platform or engine platform is connected and surface-fitted with the hole of the main positioner 1. The auxiliary positioning is the connection and surface-fitting of the initial hole of the fork lug joint with the hole of the fork lug positioner 2. The sliding device 5 drives the fork lug positioner 2 and the equipment drill template 3 to reciprocate.

[0009] 2) Pre-production inspection: Use inspection pins with initial hole diameters reduced by 0.8mm, 1.0mm, and 1.2mm to check the coaxiality of the initial hole of the fork-ear structure and the two holes of the fork-ear positioner. The inspection pins are used in descending order of size. Record the accumulated deviation data of the assembly error for tool adjustment.

[0010] 4) Pre-production preparation: The cutting tool is made of cemented carbide internal cooling tool with a front guide. The tool consists of an insert and a tool holder. The front guide diameter of each specification of tool holder is the same. The roughing and finishing of the hole are achieved by changing the insert and tool holder. According to the pre-production inspection data, the tool is adjusted using a tool setter for the final hole. After the tool is adjusted, the portable boring drill is positioned using the high-precision rigid fixture of the equipment drill template 3. The indexing chuck of the portable boring drill is inserted into the guide hole of the equipment drill template 3. The indexing chuck is rotated counterclockwise to ensure that the indexing chuck is locked with the equipment drill template 3. The portable boring drill is adjusted to the optimal working position using the rotary indexing head function.

[0011] 5) High-precision hole making: The hole making path is from left to right and from top to bottom. When making one set of holes, positioning pins need to be inserted to fix the three sets of holes on the same side and at least one set of holes on the opposite side. Four-stage hole making is adopted, namely one rough boring correction, two rough borings, and one fine boring. The speed range is 150rpm~200rpm, the feed rate range is 0.02~0.04mm / r, the rough boring depth of cut range is 0.2mm~0.8mm, and the fine boring depth of cut range is 0.15mm~0.25mm.

[0012] The main locator 1 consists of a platform hole locator, a platform surface locator, an extension mechanism, and multiple sets of positioning bolts. The extension mechanism is securely connected to the overall frame 4, and the platform hole locator and the platform surface locator are securely connected to the extension mechanism. The extension mechanism is an intermediate structure that connects the upper and lower parts. Multiple sets of positioning bolts are used to connect the product and the platform hole locator.

[0013] The number of positioning bolts corresponds to the number of platform holes on the product.

[0014] The fork ear positioner 2 consists of a fork ear hole positioner, a fork ear surface positioner, an extension mechanism, and a series of inspection pins. The extension mechanism is stably connected to the overall frame 4, and the fork ear hole positioner and the fork ear surface positioner are stably connected to the extension mechanism. The extension mechanism is an intermediate structure that connects the upper and lower parts. The series of inspection pins are used to inspect the connection between the product and the fork ear hole positioner.

[0015] The specifications and quantity of the series of inspection pins are determined based on the diameter and quantity of the holes being processed.

[0016] The series of specifications inspection pins are used to check the coaxiality of the product and the equipment drilling template 3.

[0017] The equipment drilling template 3 consists of a drilling mold and a support structure. One side of the support structure is firmly connected to the overall frame 4, and the other side is connected to the drilling mold. The support structure is an intermediate mechanism used for drilling holes in the equipment.

[0018] The overall frame 4 is a welded steel structure, capable of safely bearing its own weight, the weight of other modular structures, and the weight of the product. It is stably connected to the ground and to other modular structures.

[0019] The sliding device 5 consists of a slide rail assembly, upper / lower positioning supports, and a limiter; the upper / lower positioning supports are connected to the slide rail assembly and move back and forth with the slide rail assembly; the limiter is connected to the overall frame 4 and opens and closes with the upper / lower positioning supports to limit the position of the slide rail assembly.

[0020] The number of fork lug positioners 2 and equipment drilling templates 3 corresponds to the number of fork lugs.

[0021] The advantages of this invention are:

[0022] This invention proposes a high-precision drilling method for multi-lug aircraft structures, which offers the following advantages in improving the precision of multi-lug external beam joints for helicopters, ensuring processing quality, and increasing production efficiency: final hole accuracy is no less than H8 grade; hole wall smoothness is no less than Ra1.6; coaxiality of the front and rear holes of the same lug is no less than φ0.04mm; relative position accuracy of the four sets of lug interfaces on each side is no less than 0.1mm; the number of drilling stages is reduced by at least 50% compared to traditional methods; drilling time is reduced by at least 40% compared to traditional methods; drilling tool life is long, reducing tool costs by 95%, resulting in superior economic efficiency; the drilling quality is consistent and stable, meets ergonomic requirements, reduces operator workload, and is easy to operate. This method has been validated through long-term application and exhibits high reliability and stable quality, making it widely applicable. Attached Figure Description

[0023] Figure 1 This is the front view of a high-precision rigid fixture.

[0024] Figure 2Top view of a high-precision rigid fixture;

[0025] Figure 3 Right view of a high-precision rigid fixture;

[0026] Among them: 1-Main locator, 2-Fork ear locator, 3-Equipment drilling template, 4-Integral frame, 5-Sliding device. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings:

[0028] A high-precision drilling method for multi-lug aircraft structures, specifically including the following:

[0029] (1) Product rack positioning: The large helicopter component with integrated multi-fork lug structure is rack positioned on a high-precision rigid fixture. The high-precision rigid fixture mainly includes a main locator 1, a fork lug locator 2, an equipment drill template 3, an overall frame 4, and a sliding device 5. The main locator 1 is fixed on the upper part of the overall frame 4. The fork lug locator 2 is fixed on both sides of the overall frame 4. The equipment drill template 3 is installed on both sides of the overall frame 4, and the sliding device 5 is installed on the lower side of the overall frame 4. The main positioning reference is the upper structure of the large helicopter component. The main reduction platform or engine platform is connected to the hole of the main locator 1 and the surface is in contact with it. The auxiliary positioning is that the initial hole of the fork lug connector is connected to the hole of the fork lug locator 2 and the surface is in contact with it. The sliding device 5 drives the fork lug locator 2 and the equipment drill template 3 to reciprocate.

[0030] (2) Pre-production inspection: Use inspection pins with initial hole diameter reduced by 0.8mm, 1.0mm, and 1.2mm to check the coaxiality of the initial hole of the product's fork-type structure with the two holes of the fork-type positioner. The order of use of the inspection pins is from large to small. Record the data of the accumulated deviation of the assembly error for tool adjustment.

[0031] (3) Pre-production preparation: The tool material is cemented carbide internal cooling tool. The tool has a front guide and is composed of a cutting tool and a tool holder. The front guide diameter of each specification of tool holder is the same. The rough and fine machining of the hole is achieved by changing the cutting tool and the tool holder. According to the pre-production inspection data, the tool is adjusted by the tool setter for the final hole. After the tool is adjusted, the portable boring drill is positioned by the high-precision rigid fixture of the equipment drill template 3. The portable boring drill indexing chuck is inserted into the guide hole of the equipment drill template 3. The indexing chuck is rotated counterclockwise to ensure that the indexing chuck is locked with the equipment drill template 3. The portable boring drill is adjusted to the best working posture by using the rotary indexing head function.

[0032] (4) High-precision hole making: The hole making path is from left to right and from top to bottom. When making one set of holes, positioning pins need to be inserted to fix the three sets of holes on the same side and at least one set of holes on the opposite side. Four-stage hole making is adopted, namely rough boring and correction once, rough boring twice, and fine boring once. The speed range is 150rpm~200rpm, the feed rate range is 0.02~0.04mm / r, the rough boring depth of cut range is 0.2mm~0.8mm, and the fine boring depth of cut range is 0.15mm~0.25mm.

[0033] (5) Cleaning after hole making: Clean up the excess material generated during the hole making process.

[0034] The main locator (1) consists of a platform hole locator, a platform surface locator, an extension mechanism, and multiple sets of positioning bolts. The extension mechanism is securely connected to the overall frame 4 and is used for positioning and connecting the product to the platform structure, serving as the main positioning mechanism for product placement. The platform hole locator and the platform surface locator are securely connected to the extension mechanism, which is a connecting intermediate structure. Multiple sets of positioning bolts are used to connect the product to the platform hole locator. The number of positioning bolts corresponds to the number of platform holes on the product.

[0035] The fork-ear positioner 2 consists of a fork-ear hole positioner, a fork-ear face positioner, an extension mechanism, and a series of inspection pins. The extension mechanism is securely connected to the overall frame 4 and is used to inspect and position the multi-fork-ear structure of the product. The fork-ear hole positioner and the fork-ear face positioner are securely connected to the extension mechanism, which serves as an intermediate structure connecting the upper and lower parts. The series of inspection pins are used to inspect the connection between the product and the fork-ear hole positioner. The specifications and quantity of the series of inspection pins are determined based on the diameter and quantity of the holes being processed. The series of inspection pins are used to check the coaxiality of the product and the drilling template 3 of the equipment, and are also used for auxiliary positioning of the product.

[0036] The equipment drilling template 3 consists of a drilling mold and a support structure. One side of the support structure is firmly connected to the overall frame 4, and the other side is connected to the drilling mold. The support structure is an intermediate mechanism used for drilling holes in the equipment.

[0037] The fork lug locator 2 works in conjunction with the equipment drilling template 3. For example, if a series of auxiliary positioning pins on the fork lug locator are removed, the equipment drilling template 3 and a portable boring machine are used to drill a hole in the fork lug. After drilling, the positioning pin is reconnected. Then, drilling is performed on the next fork lug, and so on, drilling holes in different positions. To ensure accuracy, the fork lug locator 2 and the equipment drilling template 3 are not connected; they are each independently connected to the overall frame 4.

[0038] The overall frame 4 is a welded steel structure, capable of safely bearing its own weight, the weight of other modular structures, and the weight of the product. It is stably connected to the ground and to other modular structures.

[0039] The sliding device 5 consists of a slide rail assembly, upper / lower positioning supports, and a limiter; the upper / lower positioning supports are connected to the slide rail assembly and move back and forth with the slide rail assembly; the limiter is connected to the overall frame 4 and opens and closes with the upper / lower positioning supports to limit the position of the slide rail assembly.

[0040] Before the product enters the high-precision rigid fixture, the sliding device 5 is used to slide the equipment drill template 3 to the outside. After the product enters the high-precision rigid fixture, the sliding device 5 is pushed to move the equipment drill template 3 toward the product. The upper / lower positioning support of the sliding device 5 is in contact with the limiter. After there is no gap between the contact surfaces, the upper / lower positioning support is connected to the limiter and pressed tightly with the positioning bolts.

[0041] The number of fork lug positioners 2 and equipment drilling templates 3 corresponds to the number of fork lugs.

[0042] Example

[0043] The integrated weapon pylon structure of a certain type of aircraft is located in the middle of the overall frame 4 and sliding device 5. Considering the advantages of the forged frame's superior machining, improved connection strength, and reduced weight, the product design integrates eight sets (four on the left and four on the right, with final hole accuracies of 5-φ20H8mm and 3-φ24H8mm respectively) of fork-shaped integrated weapon pylon mounting interfaces into the overall frame 4 and sliding device 5. This differs from the separate parts of other helicopter integrated weapon pylon mounting interfaces, allowing for coordinated assembly to ensure relative accuracy. The overall frame 4 and sliding device 5 of this type of aircraft are all... The integral frame 4 and sliding device 5 are assembled using four φ10mm positioning holes on the frame. During the manufacturing of integral frame 4 and sliding device 5, the positional tolerance of the weapon beam mounting interface relative to the positioning hole on the frame is φ0.5mm, and the positional tolerance of the tooling positioner of integral frame 4 and sliding device 5 is φ0.2mm. The accumulation of errors caused the relative positional accuracy of the four sets of fork-type interfaces on the left and right sides to exceed the engineering requirement of 0.1mm. Therefore, the assembly error can only be eliminated by precision machining after component assembly to ensure the relative positional accuracy between the weapon beam mounting interfaces.

[0044] Based on the above requirements, an invention applies a high-precision drilling method for multi-lug aircraft structures to ensure assembly quality and efficiency, specifically including the following:

[0045] (1) Product rack positioning. The large component of the middle body, which integrates the overall frame 4 and the sliding device 5, is racked and positioned on a high-precision rigid fixture. The high-precision rigid fixture mainly includes the main locator 1, the fork ear locator 2 (8 sets, 1 set for each fork ear joint), the equipment drilling template 3 (8 sets, 1 set for each fork ear joint), the overall frame 4, and the sliding device 5 (2 sets, 1 set on each side). The main positioning reference is the connection and surface fit between the main reduction platform on the upper side of the middle body and the hole of the main locator 1. The auxiliary positioning is the connection and surface fit between the initial holes of the 8 sets of fork ear joints and the holes of the fork ear locator 2. The sliding device 5 drives the fork ear locator 2 and the equipment drilling template (3) to reciprocate.

[0046] (2) Pre-production inspection. Use Φ17.7mm, Φ17.5mm, and Φ17.3mm inspection pins to check the coaxiality of the Φ18.5mm initial hole of the product with the (2) hole of the fork lug locator. Use Φ21.7mm, Φ21.5mm, and Φ21.3mm inspection pins to check the coaxiality of the Φ22.5mm initial hole of the product with the 2 holes of the fork lug locator. The order of use of the inspection pins is from large to small. Record the accumulated deviation data of the assembly error for tool adjustment.

[0047] (3) Pre-production preparation. The cutting tool is made of cemented carbide internal cooling tool with a front guide. The tool consists of a separable insert and a tool holder. The front guide diameter of each specification of tool holder is the same. The roughing and finishing of the hole are achieved by changing the insert and tool holder. The tool setting instrument is used to adjust the φ20mm and φ24mm precision boring tools. The tool setting requirements for φ20 are: OH (main dial indicator) = +0.002mm to +0.005mm, and the difference between BT (sub-dial dial indicator) and the main dial indicator is 10±2μm. The tool setting requirements for φ24 are: OH = +0.023mm to +0.026mm, and the difference between BT (sub-dial dial indicator) and the main dial indicator is 10±2μm. After tool setting, the portable boring drill is positioned using the drilling template 3 of the equipment. The drill bushing is inserted into the guide hole of the drilling template, and the tool is rotated counterclockwise to ensure that the drill bushing lug is locked with the drilling template. The tool is then adjusted to the optimal working position using the rotatable indexing head function.

[0048] (4) High-precision hole making. No other operations are allowed on the machine during hole making. No personnel other than the hole making operator are allowed on the machine. The hole making path is from left to right and from top to bottom. To ensure the stability of the reaming state, when making one set of holes, positioning pins need to be inserted to fix the three sets of holes on the same side and at least one set of holes on the opposite side. Four-stage hole making is adopted, namely, rough boring and correction once, rough boring twice, and fine boring once. The speed is 183 rpm, the feed rate is 0.032 mm / r, and the rough boring depth is 0.2 mm. The drilling sequence for Φ20H8 is: φ18.75mm (rough boring and correction) → φ19.3mm (rough boring) → φ19.8mm (rough boring) → φ20H8 (finish boring); The drilling sequence for Φ24H8 is: φ22.75mm (rough boring and correction) → φ23.3mm (rough boring) → φ23.8mm (rough boring) → φ24H8 (finish boring).

[0049] (5) Cleaning after hole making. Clean up any excess material generated during the hole making process.

Claims

1. A high-precision hole-making method for multi-lug aircraft structures, characterized in that, Specifically, it includes the following: 1) Product rack positioning: The helicopter large component with integrated multi-fork lug structure is rack positioned on a high-precision rigid fixture. The high-precision rigid fixture mainly includes a main locator (1), a fork lug locator (2), an equipment drill template (3), an overall frame (4), and a sliding device (5). The main locator (1) is fixed on the upper part of the overall frame (4). The fork lug locator (2) is fixed on both sides of the overall frame (4). The equipment drill template (3) is installed on both sides of the overall frame (4), and the sliding device (5) is installed on the lower side of the overall frame (4). The main positioning reference is the upper structure of the helicopter large component. The main reduction platform or engine platform is connected to the hole of the main locator (1) and the surface is in contact. The auxiliary positioning is that the initial hole of the fork lug connector is connected to the hole of the fork lug locator (2) and the surface is in contact. The sliding device (5) drives the fork lug locator (2) and the equipment drill template (3) to reciprocate. 2) Pre-production inspection: Use inspection pins with initial hole diameter reduced by 0.8mm, 1.0mm, and 1.2mm to check the coaxiality of the initial hole of the product's fork-ear structure with the hole of the fork-ear locator (2). The order of use of the inspection pins is from large to small. Record the data of the accumulated deviation of the assembly error for tool adjustment. 4) Pre-production preparation: The tool material is cemented carbide internal cooling tool. The tool has a front guide and is composed of a cutting tool and a tool holder. The front guide diameter of each specification of tool holder is the same. The rough and fine machining of the hole is achieved by changing the cutting tool and the tool holder. According to the pre-production inspection data, the tool is adjusted by the tool setter for the final hole. After the tool is adjusted, the portable boring drill is positioned by the high-precision rigid fixture of the equipment drilling template (3). The portable boring drill indexing chuck is inserted into the guide hole of the equipment drilling template (3). The indexing chuck is rotated counterclockwise to ensure that the indexing chuck is locked with the equipment drilling template (3). The portable boring drill is adjusted to the best working posture by using the rotary indexing head function. 5) High-precision hole making: The hole making path is from left to right and from top to bottom. When making one set of holes, positioning pins need to be inserted to fix the three sets of holes on the same side and at least one set of holes on the opposite side. Four-stage hole making is adopted, namely one rough boring correction, two rough borings, and one fine boring. The speed range is 150rpm~200rpm, the feed rate range is 0.02~0.04mm / r, the rough boring depth of cut range is 0.2mm~0.8mm, and the fine boring depth of cut range is 0.15mm~0.25mm.

2. The high-precision hole-making method for multi-lug aircraft structures according to claim 1, characterized in that, The main locator (1) consists of a platform hole locator, a platform surface locator, an extension mechanism, and multiple sets of positioning bolts; the extension mechanism is stably connected to the overall frame (4), the platform hole locator and the platform surface locator are stably connected to the extension mechanism, the extension mechanism is an intermediate structure that connects the upper and lower parts, and multiple sets of positioning bolts are used to connect the product and the platform hole locator.

3. The high-precision hole-making method for multi-lug aircraft structures according to claim 2, characterized in that, The number of positioning bolts corresponds to the number of platform holes on the product.

4. The high-precision hole-making method for multi-lug aircraft structures according to claim 1, characterized in that, The fork ear positioner (2) consists of a fork ear hole positioner, a fork ear surface positioner, an extension mechanism, and a series of specification inspection pins. The extension mechanism is stably connected to the overall frame (4). The fork ear hole positioner and the fork ear surface positioner are stably connected to the extension mechanism. The extension mechanism is an intermediate structure that connects the upper and lower parts. The series of inspection pins are used to inspect the connection between the product and the fork lug locator.

5. The high-precision hole-making method for multi-lug aircraft structures according to claim 4, characterized in that, The specifications and quantity of the series of inspection pins are determined based on the diameter and quantity of the holes being processed.

6. The high-precision hole-making method for multi-lug aircraft structures according to claim 4, characterized in that, The series of specifications inspection pins are used to check the coaxiality of the product and the equipment drilling template (3).

7. The high-precision hole-making method for multi-lug aircraft structures according to claim 1, characterized in that, The equipment drilling template (3) consists of a drilling mold and a support structure. One side of the support structure is firmly connected to the overall frame (4), and the other side is connected to the drilling mold. The support structure is an intermediate mechanism used for drilling holes in the equipment.

8. The high-precision hole-making method for multi-lug aircraft structures according to claim 1, characterized in that, The overall frame (4) is a steel welded structure that can safely bear its own weight, the weight of other module structures and the weight of the product, and is stably connected to the ground and other module structures.

9. The high-precision hole-making method for multi-lug aircraft structures according to claim 1, characterized in that, The sliding device (5) consists of a slide rail assembly, upper / lower positioning supports, and a limiter; the upper / lower positioning supports are connected to the slide rail assembly and move back and forth with the slide rail assembly; the limiter is connected to the overall frame (4) and opens and closes with the upper / lower positioning supports to limit the position of the slide rail assembly.

10. The high-precision hole-making method for multi-lug aircraft structures according to claim 1, characterized in that, The number of fork lug positioners (2) and equipment drilling templates (3) corresponds to the number of fork lugs.

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