A method and device for controlling the aperture during the hole-making process of a laminated structure

Abstract

The present invention discloses a method and device for controlling the hole diameter during the hole-making process of a laminated structure, belonging to the technical field of high-precision hole-making. The method includes the following steps: obtaining the optimal cooling and lubrication method in the laminated structure composed of different materials, and inputting the corresponding hole-making parameters into the process database; designing a machining strategy based on the laminated structure composed of N different materials in combination with the optimal cooling and lubrication method; judging the position of the drill bit in the laminated structure; and executing the corresponding machining steps. The method and device for controlling the hole diameter during the hole-making process of the laminated structure according to the present invention can select a suitable cooling medium pressure and type according to the material characteristics of the machining object and the tool wear state when machining different material layers of the laminated structure, realize fine adjustment of the diameter of the special drill bit, and thus reduce the hole diameter tolerance of the laminated structure composed of different materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-precision hole making, and particularly relates to a method and device for controlling the hole diameter during the hole making process of a laminated structure. Background Art

[0002] Bolt connection and riveting are the most commonly used component connection methods in aircraft assembly. This mechanical connection method requires the preparation of a large number of assembly holes. To improve the hole making efficiency, a drill bit is usually used to perform hole making processing in a single drilling operation when making holes in a laminated structure. For example, for a carbon fiber reinforced resin matrix composite / titanium alloy laminated structure, the carbon fiber reinforced resin matrix composite usually shows a hole diameter smaller than the drill bit diameter after processing, while the titanium alloy shows a hole diameter larger than the drill bit diameter. Although the hole diameter tolerance within a single layer of material is small, for the overall laminated structure, the hole making diameter tolerance reaches a relatively large value, resulting in a decline in hole making quality.

[0003] At the same time, in the honing process, a cooling and lubricating medium is used to drive the movement of the honing strip and change the pressure change between the honing strip and the hole wall, thereby realizing the adjustment of the hole diameter during honing processing. Although the cooling and lubricating medium is commonly used to control the hole diameter in the honing process, the honing process and the drilling process of the laminated structure mentioned above have significant differences in both tool structure and control method, and cannot be applied to the applications described in this article. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to control the fine adjustment of the drill bit diameter during the hole making of a laminated structure, actively control the hole making diameter of the laminated structure, and improve the hole making diameter accuracy of the laminated material.

[0005] Technical Solution: A method for controlling the hole diameter during the hole making process of a laminated structure includes the following steps:

[0006] S1, input the corresponding hole making parameters into the process database to obtain the optimal cooling and lubrication method in the laminated structure composed of different materials;

[0007] S2, based on the laminated structure composed of N different materials, combined with the optimal cooling and lubrication method in S1, design a processing strategy;

[0008] S3, determine the position of the drill bit in the laminated structure;

[0009] S4, execute the corresponding processing steps.

[0010] In a further embodiment, the content of the processing strategy in S2 includes the cooling and lubrication methods within the N material layers, the cooling and lubrication methods at the N - 1 laminated interfaces, and the fine adjustment of the drill bit diameter.

[0011] In a further embodiment, the method for determining the position of the drill bit in the laminated structure in S3 is to locally design the drill bit as an induction part, and the induction part is provided with a diameter fine-tuning mechanism, and the diameter fine-tuning mechanism is used to sense the diameter change in the laminated structure during hole making.

[0012] In a further embodiment, it includes a drill bit for hole making, an internal cooling channel arranged in the drill bit, one end of a connecting pipe connected to the input end of the internal cooling channel, a control unit connected to the other end of the connecting pipe, and a diameter fine-tuning mechanism connected to the output end of the internal cooling channel, and the diameter fine-tuning mechanism is arranged on the circumference of the drill bit.

[0013] In a further embodiment, the control unit controls the diameter fine-tuning mechanism to change the local diameter of the drill bit by controlling the pressure of the cooling lubricant in the internal cooling channel.

[0014] In a further embodiment, it further includes a position sensor, the position sensor is connected to the control unit, and the position sensor is used to sense the position of the drill bit in the laminated structure and send the position information to the control unit.

[0015] In a further embodiment, the connection between the internal cooling channel and the connecting pipe is reinforced by a rotary joint.

[0016] Beneficial effects: Compared with the prior art, the remarkable advantage of the present invention is that when processing different material layers of the laminated structure, according to the material characteristics of the processing object and the tool wear state, the appropriate cooling medium pressure and type can be selected to realize the fine-tuning of the diameter of the special drill bit, thereby reducing the hole diameter tolerance of the laminated structure composed of different materials. Brief Description of the Drawings

[0017] Figure 1 is the schematic diagram of the hole-making device for adaptive machining of the composite material / metal laminated structure in the present invention.

[0018] Figure 2 is the flow chart of the adaptive control of the hole diameter for hole making of the laminated structure in the present invention.

[0019] Figure 3 is the schematic diagram of the drill bit with the function of diameter fine-tuning.

[0020] Figure 4 is the cross-sectional view of the drill bit with the function of diameter fine-tuning. Detailed Embodiments

[0021] The following describes the detailed embodiments of the present invention with reference to the accompanying drawings.

[0022] Embodiment 1

[0023] Based on the technical problems mentioned in the above background, this embodiment proposes a method for controlling the hole diameter during the hole-making process of a laminated structure, which specifically includes the following content:

[0024] At the beginning of drilling, data such as the material to be processed, the processing tool, and the target hole diameter are first input into the processing system, and by comparing with the process database, the optimal cooling and lubrication methods for the single-layer material in the laminated structure and different laminated interfaces in the laminated structure are obtained.

[0025] Among them, if there is a laminated structure composed of two different materials, the processing process strategy is divided into the cooling and lubrication methods within the two material layers and the cooling and lubrication method at one laminated interface.

[0026] If there is a laminated structure composed of n different materials, the processing process strategy is divided into the cooling and lubrication methods within the n material layers and the cooling and lubrication methods at n - 1 laminated interfaces.

[0027] Here, the process database needs to be obtained by combining processing experiments and theoretical modeling. The process database is the summary and induction of existing process knowledge to form some basic process-specific data. The process database in this embodiment is a database that establishes the relationship between cooling pressure and tools, materials, and hole-making diameters through methods such as experiments.

[0028] Among them, the above-mentioned processing experiment refers to drilling a specific material under the condition of known coolant pressure using drill bit 3, and finally measuring the hole diameter size of the drilled hole.

[0029] Step 2: During the actual drilling process, judge the position of the variable part of the diameter of drill bit 3 through a detection method. If the preset processing position in the preset strategy is reached, execute the preset cooling and lubrication method. There are many ways to judge the position of the drill bit in the laminate, such as measuring the plate thickness and calculating the relative position. Here, the preset strategy refers to the hole-making strategy formulated for the target laminate material before processing. For example, coolant pressure a is used in laminate material component A, and coolant pressure b is used in laminate material component B.

[0030] The content of the processing strategy in this embodiment includes the cooling and lubrication methods within N material layers, the cooling and lubrication methods at N - 1 laminated interfaces, and the fine adjustment of the diameter of drill bit 3.

[0031] In addition to the adaptive adjustment of the hole diameter for the laminated structure composed of two materials, the advantage of this embodiment is that it can also adjust the hole diameter for laminated structures of two or more layers.

[0032] Due to its independence in aperture control, it can adjust the cooling and lubrication strategy in real time according to the tool wear situation, so as to achieve online compensation for the influence of tool wear on the aperture.

[0033] Embodiment 2

[0034] Based on the aperture control method in the hole-making process of the laminated structure in Embodiment 1, a specific implementation device is proposed in this embodiment, including a drill bit 3, an internal cooling channel 8, a connecting pipe 6, a control unit 5, a diameter fine-tuning mechanism 4, a position sensor 9, and a rotary joint 7, as Figure 1 shown. In this embodiment, the titanium alloy material layer 1 of the laminated structure and the carbon fiber reinforced resin matrix composite (CFRP) layer 2 of the laminated structure are taken as examples for explanation. The diameter fine-tuning mechanism 4 is installed on the drill bit 3. This fine-tuning mechanism 4 is a prior art and will not be elaborated here. The internal cooling channel 8 is installed inside the drill bit 3. The output end of the internal cooling channel 8 is connected to the diameter fine-tuning mechanism 4, and the input end of the internal cooling channel 8 is connected to the connecting pipe 6 through the rotary joint 7. The other end of the connecting pipe 6 is connected to the control unit 5. At the same time, the position sensor 9 is connected to the control unit 5 to sense the position of the drill bit 3.

[0035] Figure 3 Shows a schematic diagram of a drill bit with a diameter fine-tuning mechanism. The drill bit mainly includes a drill rod 11, a drill tip 12, and a diameter fine-tuning mechanism 13. The function of the drill rod is to provide the clamping position of the drill bit and the chip fluting. The drill tip plays the role of removing materials in the drilling process. Since this drill bit needs to install a diameter fine-tuning mechanism, the drill bit adopts a split design, and the drill tip and the drill rod are fixedly connected by a screw 14.

[0036] The cross-sectional view of the structure of the drill bit with the diameter fine-tuning function is as Figure 4 shown. There is a screw rod 18 with a hollow interior and an external threaded structure at the rear end of the drill rod. Its function is to limit the retraction of the ejector rod 16 and play the role of conveying the coolant pressure.

[0037] During the working process, the coolant passes through the inner hole of the screw rod 18 and enters the cavity at the rear of the ejector rod. Due to the function of the sealing ring 17, the coolant cannot enter the front of the ejector rod and can only act on the rear of the ejector rod with a certain pressure, applying a pressure to it to ensure that the ejector rod will only move unidirectionally along the axial direction of the drill bit after being pressurized.

[0038] The ejector rod 16 transmits the liquid pressure to the front end. After offsetting the restoring force of the spring 15 and the resilience force during the material cutting process, the adjustable sub-edge 13 of the drill bit is pushed outwards. Since the contact surface between the adjustable sub-edge 13 of the drill bit and the ejector rod 16 presents a wedge shape, the axial expansion and contraction of the ejector rod will cause the radial expansion of the adjustable sub-edge 13 of the drill bit. The greater the coolant pressure at the rear end of the ejector rod, the greater the unidirectional force borne by the ejector rod, the greater the axial expansion and contraction amount of the ejector rod, and the greater the radial expansion amount of the adjustable sub-edge of the drill bit. Thus, the purpose of controlling the diameter of the adjustable sub-edge of the drill bit through the cooling medium pressure and further controlling the drilling diameter is achieved.

[0039] In this embodiment, the control unit 5 is configured to control the diameter fine-tuning mechanism 4 by increasing or decreasing the pressure of the cooling lubricant in the internal cooling channel 8, thereby changing the diameter of the sensing part of the drill bit 3.

[0040] Due to the differences in physical properties between different materials in the laminated structure, there are significant differences in the diameters of the drilled holes.

[0041] The following table shows the material properties of each component in the laminated structure

[0042]

[0043] Generally, for the same tool, the drilled hole diameter in the CFRP layer is smaller than the tool diameter, and the drilled hole diameter in the titanium alloy layer is larger than the tool diameter.

[0044] Therefore, for the titanium alloy / CFRP laminated structure, when the position sensor senses that the diameter fine-tuning mechanism 4 of the drill bit 3 is in the titanium alloy layer 1, the machine tool control system will send an instruction to the cooling lubricant control unit according to the preset strategy. Then, the control unit 5 will send an instruction to the proportional valve through the PLC, and the pressure sensor will feedback the pressure to the PLC to start reducing the cooling medium pressure. Thus, the pressure input to the diameter fine-tuning mechanism 4 on the drill bit 3 will decrease, the diameter fine-tuning mechanism 4 will contract, and the drilled hole diameter will relatively decrease.

[0045] When the position sensor 9 senses that the diameter fine-tuning mechanism 4 of the drill bit 3 is in the CFRP layer 2, the control unit 5 will start increasing the cooling medium pressure, for example, by increasing the opening degree of the proportional valve. Thus, the pressure input to the diameter fine-tuning mechanism 4 of the drill bit 3 will increase, the drill bit 3 will be in the large diameter state, and the drilled hole diameter in the CFRP layer will relatively increase.

[0046] Compared with the traditional drilling method, this device can relatively increase the drilled hole diameter in the titanium alloy layer and relatively decrease the drilled hole diameter in the CFRP. Then, the difference in the drilled hole diameters of the titanium alloy / CFRP laminated structure will decrease, achieving a reduction in the drilled hole diameter tolerance of the laminated structure.

[0047] Embodiment 3

[0048] Different from Example 1, the laminated structure in this example refers to a structure composed of at least two different materials.

[0049] Example 4

[0050] Different from Example 1, in this example, the diameter adjustment of drill bit 3 can be the adjustment of the main cutting edge diameter of drill bit 3 or the adjustment of the secondary cutting edge diameter of drill bit 3.

[0051] Example 5

[0052] Based on the content of Example 2, the drilling process in this example can be a traditional hole-making technology or special drilling technologies such as low-frequency vibration-assisted hole-making technology and ultrasonic vibration-assisted hole-making technology.

Claims

1. An apparatus for the method of controlling the hole diameter during the hole-making process using a laminated structure, the method of controlling the hole diameter during the hole-making process using a laminated structure includes the following steps: S1. Input the corresponding hole-making parameters into the process database to obtain the optimal cooling and lubrication method in the process database for the laminated structure composed of different materials; S2. Based on the laminated structure composed of N materials, combined with the optimal cooling and lubrication method in S1, design a machining strategy; the content of the machining strategy includes the cooling and lubrication methods within the N material layers, the cooling and lubrication methods at the N - 1 laminated interfaces, and the fine adjustment of the drill bit diameter; S3. Determine the position of the drill bit in the laminated structure; S4. Execute the corresponding machining steps; It is characterized in that it includes a drill bit (3) for hole-making, an internal cooling channel (8) arranged in the drill bit (3), one end of a connecting pipe (6) connected to the input end of the internal cooling channel (8), a control unit (5) connected to the other end of the connecting pipe (6), and a diameter fine adjustment mechanism (4) connected to the output end of the internal cooling channel (8), and the diameter fine adjustment mechanism (4) is arranged on the circumference of the drill bit; The drill bit includes a drill rod (11), a drill tip (12), and an adjustable secondary cutting edge (13). There is a screw rod (18) with a hollow interior and an external threaded structure at the rear end of the drill rod. A push rod (16) is provided to transmit the liquid pressure to the front end. The coolant passes through the inner hole of the screw rod (18) and enters the cavity at the rear of the push rod (16) and acts on the rear of the push rod with a certain pressure to apply an acting pressure to the push rod (16). The push rod (16) moves unidirectionally along the axial direction of the drill bit under the action of the pressure; the contact surface between the adjustable secondary cutting edge (13) and the push rod (16) is wedge-shaped, and the axial expansion and contraction of the push rod bring about the radial expansion of the adjustable secondary cutting edge (13) of the drill bit.

2. The device for the aperture control method during the hole-making process using a laminated structure according to claim 1, characterized in that, It further includes a position sensor (9), the position sensor (9) is connected to the control unit (5), and the position sensor (9) is used to sense the position of the drill bit in the laminated structure and send the position information to the control unit (5).

3. The device for the aperture control method during the hole-making process using a stacked structure according to claim 1, characterized in that, The connection between the internal cooling channel (8) and the connecting pipe (6) is reinforced by a rotary joint (7).

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