Aluminum alloy inner buckle three-hole diameter-keeping burr-preventing processing method and clamp

Abstract

The application discloses a kind of aluminum alloy inner buckle three-hole diameter preventing burr processing method and fixture.The method obtains the final hole diameter of inner buckle, hole position, reference, burr-free requirement of inner cavity and the hole diameter change quantity before and after conductive oxidation, determines the hole diameter control value before conductive oxidation;The inner buckle is positioned in the fixture with reference surface and lateral profile, and the middle hole and two side holes are machined by three replaceable guide sleeves;A sacrificial back support assembly is provided on the outlet side of the hole, the hole outlet periphery material is supported by the annular surface of the hole, and the cutter penetration end is provided with a space for the cutter penetration end by the back support microcavity, and the chip or small burr is accommodated;During machining, the chip is removed by negative pressure or directional air blowing, and after machining, the hole diameter, effective hole depth, penetration state, hole mouth burr and hole residual chip are detected, and finally reviewed and feedback corrected after conductive oxidation.

Description

Technical Field

[0001] This invention relates to the fields of precision machining of aluminum alloy parts, positioning and clamping of three-hole parts, anti-burr machining of small holes, dimensional compensation before conductive oxidation and post-hole inspection, and particularly to a method and fixture for anti-burr machining of three holes in aluminum alloy internal fasteners with diameter preservation. Background Technology

[0002] Aluminum alloy internal fasteners are typically characterized by small size, concentrated hole positions, thin local wall thickness, high requirements for hole quality, and the need to meet final assembly dimensions even after surface treatment. For small aluminum alloy internal fasteners requiring conductive anodizing, hole diameter, hole burrs, internal cavity cleanliness, surface scratches, and residual marking dust can all affect subsequent assembly, conductive contact, or visual inspection.

[0003] Existing methods for machining small holes typically involve clamping with a standard pressure plate, drilling, reaming, chamfering, and manual deburring. While these methods are sufficient for general hole-type parts, they have the following drawbacks when applied to small internal fasteners with specific dimensional requirements and conductive oxidation requirements:

[0004] First, if the final aperture is processed directly and then conductive oxidation is performed, the conductive oxidation, cleaning, or subsequent surface treatment may cause changes in the aperture, resulting in the aperture after conductive oxidation deviating from the final size requirement.

[0005] Secondly, small internal fasteners with three holes arranged in a concentrated manner are easily affected by clamping force, cutting force and repeated clamping errors during processing, which can cause hole position displacement, hole shaft tilting or local deformation of the hole opening.

[0006] Third, ordinary guide fixtures generally focus on guiding the hole shaft on the inlet side, but lack effective support on the outlet side of the hole. When the tool passes through, burrs, flanges, or hole collapse are easily formed on the outlet side.

[0007] Fourth, if the ordinary back support block is in planar contact, although it can support the hole outlet, it is easy to clog the chips or squeeze the burrs at the hole opening when the tool passes through; if no back support is set at all, it is difficult to suppress the burrs on the exit side and the hole opening damage.

[0008] Fifth, if the residue inside the holes after three-hole processing, the microburrs at the hole openings, and the changes in hole diameter after conductive oxidation are not detected and reported, subsequent batches may still experience problems such as unstable hole diameter, dirt inside the holes, or residual powder from markings.

[0009] Therefore, it is necessary to provide a three-hole diameter-maintaining and anti-burr machining method and fixture suitable for aluminum alloy internal fasteners, so that the three-hole guiding machining can be completed under the same datum, with sacrificial back support and chip support on the hole exit side, and combined with hole diameter compensation before and after conductive oxidation, chip removal in the hole, post-hole inspection and subsequent batch feedback, so as to improve the final dimensional stability of the three holes and the hole quality. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a method and fixture for machining three holes of aluminum alloy internal fasteners with diameter protection and anti-burr, so as to solve the problems that in the prior art, after machining three holes of small aluminum alloy internal fasteners, burrs at the hole opening, debris inside the hole, deviation of the hole diameter from the final size after conductive oxidation, large repeated positioning error, and lack of effective support on the hole exit side are easy to occur.

[0011] To solve the above-mentioned technical problems, the present invention provides a three-hole diameter-maintaining and burr-resistant machining method for aluminum alloy internal fasteners. The aluminum alloy internal fastener has a reference surface, an inner cavity, a central hole located on the same side, and two side holes, and the aluminum alloy internal fastener undergoes conductive oxidation treatment after machining.

[0012] The method includes the following steps.

[0013] S10, obtain the final hole diameter requirements, hole position requirements, reference requirements, burr-free requirements for the inner cavity of the aluminum alloy fastener, and the change in hole diameter before and after conductive oxidation.

[0014] The final pore size requirement refers to the pore size requirement after conductive oxidation and subsequent cleaning, not just the pore size immediately after machining. The change in pore size before and after conductive oxidation can be determined using historical samples or trial-processed samples made under the same material and surface treatment conditions.

[0015] For the i-th hole, the hole diameter control value Dpre,i before conductive oxidation can be determined by the following formula: Dpre,i=Dfin,i-ΔDi Where Dfin,i is the final target aperture value of the i-th hole, and ΔDi is the aperture change of the i-th hole during the conductive oxidation and cleaning process. ΔDi is determined statistically by the difference between the aperture Dox,i after conductive oxidation and the aperture Dmach,i before conductive oxidation of the sample, i.e., ΔDi = mean(Dox,i - Dmach,i). Since different conductive oxidation processes, cleaning methods, and aperture sizes may lead to different directions of aperture change, ΔDi is allowed to be positive, zero, or negative.

[0016] S20 performs rough machining of the outer shape, pre-machining of the reference surface and pre-machining of the inner cavity on the aluminum alloy inner fastener blank, and reserves finishing allowance in the middle hole, two side holes and the hole opening area.

[0017] In one embodiment, the outer contour, reference surface, and inner cavity of the aluminum alloy inner fastener are machined first, and then the three holes are machined. For cases where the intermediate hole is a stepped hole, countersunk hole, threaded hole, or a stepped mating hole, a guide hole can be pre-made in the roughing stage, and the hole reaming, fine boring, or threading can be completed in the finishing stage.

[0018] S30: The aluminum alloy inner fastener is installed into a three-hole diameter-maintaining and burr-proof machining fixture. The fixture coordinate system is established with the reference surface and the lateral contour, and a controlled clamping state is formed through the low-deformation clamping assembly.

[0019] The fixture coordinate system can be established using a reference surface positioning component, a lateral limiting component, and at least one anti-rotation limiting component. The reference surface positioning component is used to mate with the reference surface of the aluminum alloy inner fastener, the lateral limiting component is used to limit the offset of the aluminum alloy inner fastener in the direction of the hole center line or perpendicular to the hole center line, and the anti-rotation limiting component is used to limit the rotation of the aluminum alloy inner fastener around the positioning reference.

[0020] The low-deformation clamping assembly applies controlled clamping force to the aluminum alloy inner fastener, ensuring that the part does not displace beyond the allowable positioning deviation during hole machining, while avoiding local deformation, surface damage, or deformation of the hole area due to excessive clamping force.

[0021] S40 aligns the three replaceable guide sleeves on the inlet-side guide plate with the theoretical hole axes of the central hole and the two side holes, respectively.

[0022] Three replaceable guide sleeves are mounted on the same inlet-side guide plate, corresponding to the central hole and two side holes respectively. Before machining, the axial positions of the three replaceable guide sleeves can be checked using a machine tool probe, standard mandrel, or guide sleeve calibration pin. Based on the check results, the machine tool coordinate zero point can be corrected, the inlet-side guide plate adjusted, or the corresponding guide sleeve replaced. Unified calibration between the three guide sleeves and the fixture coordinate system reduces hole position errors caused by multiple positioning operations for the three holes.

[0023] S50, a sacrificial back support assembly is provided on the outlet side of the middle hole and the two side holes, so that the sacrificial back support block supports the area around the hole outlet and the back support micro-cavity on the sacrificial back support block is opposite to the corresponding hole outlet area.

[0024] The sacrificial back support assembly includes a back support base, an elastic preload member, a back support adjustment screw, and a sacrificial back support block. The back support adjustment screw is used to adjust the contact state or back support gap between the sacrificial back support block and the outlet side surface of the aluminum alloy inner fastener hole. The elastic preload member is used to limit the instantaneous back support force of the sacrificial back support block on the aluminum alloy inner fastener.

[0025] A back support microcavity is provided on the side of the sacrificial back support block facing the hole exit. The back support microcavity includes a chip-receiving recess corresponding to the hole exit and a hole-mouth support ring surface surrounding the chip-receiving recess. The hole-mouth support ring surface is used to support the material around the hole exit, and the chip-receiving recess is used to provide clearance space for the tool exit end and to accommodate chips or microburrs.

[0026] When the above structure is adopted, the material around the hole exit can be supported by the back support, reducing the risk of forming flanges, burrs or hole collapse when the tool passes through; at the same time, the chip-receiving recess can prevent the flat back support from completely blocking the chip channel, reducing the risk of chips squeezing the edge of the hole or entering the inner cavity.

[0027] S60, machining the middle hole and two side holes in the same fixture coordinate system, and removing the chips inside the hole through the negative pressure chip removal channel or the directional air blowing channel during the hole machining process.

[0028] In one embodiment, when the intermediate hole is a stepped hole, countersunk hole, threaded hole, or stepped mating hole, a guide hole is formed first, followed by reaming, precision boring, or threading. The two side holes can be machined in a symmetrical alternating sequence, i.e., one side hole is machined first, followed by the other side hole, or the intermediate hole is machined first, followed by both side holes, to reduce part offset caused by unilateral cutting forces.

[0029] During hole machining, a negative pressure chip removal channel or a directional air blowing channel is connected to the hole machining area, allowing chips to be discharged in a predetermined direction. For aluminum alloy internal fasteners where burrs, dirt, or chips are not allowed to remain in the inner cavity, directional air blowing, negative pressure suction, or cleaning can be performed during or after hole machining to assist in chip removal.

[0030] S70 performs inspections on the machined intermediate hole and two side holes for hole diameter, effective hole depth, continuity status, hole burrs, and internal debris.

[0031] The inspection methods may include at least one of the following: go / no-go gauge, needle gauge, airflow detection, negative pressure detection, endoscopic visual inspection, or orifice magnification inspection. Go / no-go gauge and needle gauge are used to determine the orifice diameter, effective orifice depth, or continuity status; airflow detection or negative pressure detection is used to determine whether there are debris or blockages inside the orifice; endoscopic visual inspection or orifice magnification inspection is used to determine orifice burrs, orifice edge collapse, flange, or orifice wall residue.

[0032] S80, based on the test results, performs micro-finishing of the orifice, reverse deburring, or internal cleaning.

[0033] When burrs or partial flanges are detected at the orifice opening, micro-finishing, reverse deburring, brushing, soft abrasive treatment, or low-pressure cleaning can be used. For residual debris inside the orifice, negative pressure suction, directional air blowing, ultrasonic cleaning, or cleaning with a special cleaning needle can be used. During the process, care should be taken to avoid enlarging the orifice diameter, scratching the surface, or creating new debris shedding risks.

[0034] S90, conductive oxidation treatment is applied to the inner fasteners of the aluminum alloy.

[0035] Before conductive oxidation, the residue inside the hole, the burrs at the hole opening, and the cleanliness of the inner cavity can be checked to avoid the residue or burrs affecting the hole diameter and hole opening quality after conductive oxidation.

[0036] S100 performs a final check on the hole diameter, orifice burrs, internal cavity cleanliness, and residual state of the middle hole and two side holes after conductive oxidation treatment. The check results are used to correct the hole diameter control value before conductive oxidation in subsequent batches, or to determine the replacement, cleaning, or adjustment status of the guide sleeve or sacrificial back support assembly.

[0037] When the pore size after conductive oxidation deviates from the final target pore size value, the system or process personnel will correct ΔDi or Dpre,i for the next batch based on the direction and amount of deviation. If burrs at the pore opening, debris inside the pore, or abnormal ventilation resistance occur continuously, it indicates the need to replace the sacrificial back support block, clean the back support microcavity, replace the guide sleeve, or adjust the back support preload.

[0038] The present invention also provides a three-hole diameter-maintaining and burr-resistant machining fixture. The fixture includes a tooling base, a part positioning seat, a reference surface positioning assembly, a lateral limiting assembly, a low-deformation clamping assembly, an inlet-side guide plate, three replaceable guide sleeves, an outlet-side sacrificial back support assembly, a chip removal channel, and a post-hole inspection interface.

[0039] The fixture base is used to connect to the machine tool table. The part locating seat, mounted on the fixture base, is used to support the aluminum alloy inner fastener. The datum surface locating assembly and the lateral limiting assembly are used to establish the fixture coordinate system for the aluminum alloy inner fastener. The low-deformation clamping assembly is used to clamp the aluminum alloy inner fastener onto the part locating seat.

[0040] An inlet-side guide plate is positioned on the inlet side of the aluminum alloy inner fastener's hole. Three replaceable guide sleeves are respectively positioned on the inlet-side guide plate, corresponding to the central hole and the two side holes. An outlet-side sacrificial back support assembly is positioned on the outlet side of the aluminum alloy inner fastener's hole, and includes sacrificial back support blocks corresponding to the central hole and the two side holes.

[0041] The chip removal channel is connected to the hole machining area, and the post-hole inspection interface is used to connect an airflow detection device, a negative pressure detection device, or a hole residual state detection device.

[0042] In one embodiment, the sacrificial back support block is a replaceable structure, and each sacrificial back support block is provided with a back support microcavity opposite to the corresponding hole exit area. The back support microcavity includes a chip-receiving recess and a hole-mouth support ring surface. The material hardness of the sacrificial back support block is lower than the cutting edge hardness of the hole-making tool, and it has the compressive strength to support the material around the hole exit, so as to reduce damage to the hole and the tool, and facilitate quick replacement after the back support block wears out. Beneficial effects

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] First, the present invention moves the final pore size requirement after conductive oxidation to the machining stage, and determines the pore size control value before conductive oxidation by the change in pore size before and after conductive oxidation, which helps to reduce the risk of the pore size deviating from the final size requirement after conductive oxidation.

[0045] Secondly, the present invention establishes a unified fixture coordinate system through a reference surface positioning component, a lateral limiting component, and an inlet side guide plate, so that the middle hole and the two side holes can complete the guiding processing in the same positioning state, which is beneficial to reduce the hole position error and hole axis deviation of the three holes.

[0046] Third, the present invention provides a sacrificial back support assembly on the hole outlet side and supports the material around the hole outlet through the hole outlet support ring surface, which helps to reduce the risk of hole burrs, flanges or hole collapse when the tool passes through.

[0047] Fourth, the present invention provides a back support microcavity on the sacrificial back support block, which provides support for the orifice while also providing space for chips and tiny burrs, thus avoiding chip blockage or orifice compression by ordinary flat back supports.

[0048] Fifth, the present invention removes the chips from the hole through a negative pressure chip removal channel or a directional air blowing channel, and performs hole diameter, effective hole depth, continuity status, burrs and residual chips detection after hole processing, which helps to meet the processing requirements of burr-free and dirt-free inner cavity of small internal fasteners.

[0049] Sixth, the present invention reuses the final verification result after conductive oxidation treatment for the adjustment of the aperture control value, guide sleeve status or back support component status of the next batch, so that the three-hole diameter protection and anti-burr processing process forms a closed loop. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments are briefly described below. The following drawings are only some embodiments of the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0051] Figure 1 This is a flowchart illustrating the three-hole diameter-maintaining and burr-proof processing method for aluminum alloy internal fasteners according to the present invention. Figure 2 This is a schematic diagram of the overall structure of the three-hole diameter-maintaining and burr-resistant machining fixture of the present invention; Figure 3 This is a cross-sectional view of the inlet-side guide sleeve, aluminum alloy inner fastener, and outlet-side sacrificial back support assembly of the present invention. Figure 4 This is a schematic diagram illustrating the logic of pore size compensation before and after conductive oxidation, post-pore detection, and feedback correction in this invention.

[0052] Explanation of reference numerals in the attached drawings: 1. Tooling base; 2. Part positioning seat; 3. Reference surface positioning assembly; 4. Lateral limiting assembly; 5. Low deformation clamping assembly; 6. Inlet side guide plate; 7. Replaceable guide sleeve; 71. Intermediate hole guide sleeve; 72. First side hole guide sleeve; 73. Second side hole guide sleeve; 8. Outlet side sacrificial back support assembly; 81. Back support seat; 82. Elastic preload component; 83. Back support adjusting screw; 84. Sacrificial back support block; 85. Back support microcavity; 851. Chip-collecting recess; 852. Hole opening support ring surface; 9. Chip removal channel; 10. Post-hole inspection interface; 11. Aluminum alloy inner fastener; 111. Reference surface; 112. Inner cavity; 113. Intermediate hole; 114. First side hole; 115. Second side hole; 116. Hole outlet side surface; 12. Marked area. Detailed Implementation

[0053] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the concept of the present invention, those skilled in the art can make equivalent adjustments to the guide sleeve size, back support preload, back support microcavity shape, chip removal method and post-hole inspection method based on the material grade, hole diameter, hole spacing, hole depth, surface treatment method, machine tool specifications and inspection method of the aluminum alloy inner fastener.

[0054] Example 1: Determination of Pore Size Compensation Amount Before Conductive Oxidation In this embodiment, the aluminum alloy inner fastener 11 is made of AL6061 material and undergoes conductive oxidation treatment after machining. The aluminum alloy inner fastener 11 includes a reference surface 111, an inner cavity 112, a central hole 113, a first side hole 114, a second side hole 115, and a marking area 12.

[0055] Since conductive oxidation and cleaning processes may cause changes in pore size, the change in pore size ΔDi before and after conductive oxidation is determined by using historical samples or trial-processed samples with the same material and surface treatment conditions before formal processing.

[0056] For the i-th hole, first measure the hole diameter Dmach,i before conductive oxidation treatment of the sample, then measure the hole diameter Dox,i after conductive oxidation treatment. The change in hole diameter for the i-th hole is obtained statistically from multiple samples. ΔDi=mean(Dox,i-Dmach,i) During formal production, the aperture control value Dpre,i before conductive oxidation is determined according to the following formula: Dpre,i=Dfin,i-ΔDi Where Dfin,i is the target final diameter value of the i-th hole. Through the above compensation, the hole diameter control in the machining stage is no longer simply equivalent to the hole diameter in the final drawing, but takes into account the dimensional change trend after conductive oxidation and cleaning.

[0057] Example 2: Fixture Positioning and Entrance Guidance The aluminum alloy inner fastener 11 is placed on the part positioning seat 2, so that the reference surface 111 is in contact with the reference surface positioning assembly 3. The lateral limiting assembly 4 makes light contact or gap limiting with the lateral contour of the aluminum alloy inner fastener 11 to limit the offset of the part in the direction of the hole center line or perpendicular to the hole center line. The low deformation clamping assembly 5 applies a controlled clamping force to the aluminum alloy inner fastener 11 to keep it stable during processing, while avoiding excessive local clamping deformation of the small aluminum alloy inner fastener.

[0058] The inlet-side guide plate 6 is installed on the inlet side of the hole in the aluminum alloy inner fastener 11. The inlet-side guide plate 6 is equipped with a middle hole guide sleeve 71, a first side hole guide sleeve 72, and a second side hole guide sleeve 73, which correspond to the middle hole 113, the first side hole 114, and the second side hole 115, respectively. Before machining, the positional relationship between the axis of each guide sleeve and the theoretical hole axis is checked using a standard mandrel or machine tool probe; if the deviation exceeds the allowable range, the position of the inlet-side guide plate 6 is adjusted, the machine tool coordinate zero point is corrected, or the corresponding replaceable guide sleeve 7 is replaced.

[0059] Example 3: Export Sacrificial Back Support and Back Support Microcavity The outlet-side sacrificial back support assembly 8 is disposed on the outlet side of the hole in the aluminum alloy inner fastener 11. Each outlet-side sacrificial back support assembly 8 includes a back support seat 81, an elastic preload member 82, a back support adjustment screw 83, and a sacrificial back support block 84.

[0060] A back support microcavity 85 is provided on the side of the sacrificial back support block 84 facing the hole exit side surface 116. The back support microcavity 85 includes a chip-receiving recess 851 and a hole-mouth support annular surface 852. The hole-mouth support annular surface 852 contacts or maintains a small back support gap with the peripheral area of ​​the hole exit to support the edge of the hole exit; the chip-receiving recess 851 is opposite to the central area of ​​the hole exit to provide clearance space for the tool exit end and to accommodate chips or small burrs.

[0061] The contact state or back support gap between the sacrificial back support block 84 and the hole outlet side surface 116 can be controlled by adjusting the back support adjusting screw 83. The elastic preload member 82 is used to limit the instantaneous back support force and prevent the sacrificial back support block 84 from exerting excessive pressure on the aluminum alloy inner fastener 11. The sacrificial back support block 84 can be made of replaceable material and can be replaced after wear, chip blockage, or damage from being pierced by a tool.

[0062] Example 4: Three-hole machining and chip removal Machining of the intermediate hole 113, the first side hole 114, and the second side hole 115 under the same fixture coordinate system. For the intermediate hole 113, which is a stepped hole, countersunk hole, threaded hole, or a stepped mating hole, first machining the pilot hole, then performing reaming, fine boring, or threading. For the first side hole 114 and the second side hole 115, pilot drilling, reaming, or finishing drilling methods can be used.

[0063] The three holes can be machined in the order of middle hole 113, first side hole 114, and second side hole 115, or in a symmetrical alternating order of first side hole 114, middle hole 113, and second side hole 115. When using a symmetrical alternating order, the cutting force offset and slight part displacement caused by continuous machining on one side can be reduced.

[0064] During hole machining, the chip removal channel 9 is connected to the hole machining area. The chip removal channel 9 can be connected to a negative pressure suction device or a directional air blowing device to discharge the chips in the hole in a predetermined direction. For intermediate holes 113 or stepped hole areas where chips are prone to remain, short-term negative pressure suction or directional air blowing can be performed after each machining stage to reduce the risk of chips entering the inner cavity 112.

[0065] Example 5: Post-hole inspection, finishing and cleaning After the three holes are processed, the airflow detection device, negative pressure detection device or hole residual state detection device are connected through the hole detection interface 10 to detect the middle hole 113, the first side hole 114 and the second side hole 115.

[0066] In one implementation, a go / no-go gauge or a needle gauge is first used to check the hole diameter, effective hole depth, or continuity status. Then, airflow detection or negative pressure detection is used to determine whether there are debris or blockages inside the hole. For the hole opening area, magnified hole opening detection or endoscopic visual inspection can be used to determine whether there are burrs, flanges, hole opening collapse, or local scratches.

[0067] If burrs or slight edge curling are found at the orifice opening, perform minor finishing or reverse deburring. If debris or abnormal air resistance is found inside the orifice, treat it using negative pressure suction, directional air blowing, ultrasonic cleaning, or needle-assisted cleaning. The removal amount should be controlled during these processes to avoid enlarging the orifice diameter or causing new damage.

[0068] Example 6: Verification and Feedback Correction after Conductive Oxidation After machining, finishing, and cleaning, the aluminum alloy inner fastener 11 undergoes conductive oxidation treatment. Following this treatment, the final hole diameter of the central hole 113, the first side hole 114, and the second side hole 115 is checked, and the burrs at the hole openings, internal debris, and the cleanliness of the inner cavity are inspected. If the aluminum alloy inner fastener 11 has a marking area 12, the marking clarity, marking edge burrs, marking powder residue, and the state of any residue inside the hole are also checked.

[0069] If the pore diameter after conductive oxidation deviates from the final target pore diameter value, the pore diameter change ΔDi and the pore diameter control value Dpre,i before conductive oxidation are corrected for the corresponding pores in the next batch according to the direction and amount of deviation. If burrs or debris continuously appear at the pore opening or inside the pore, the wear condition of the sacrificial back support block 84, the blockage condition of the back support microcavity 85, the wear condition of the guide sleeve 7, and the unobstructed condition of the chip removal channel 9 are checked. Based on the inspection results, the sacrificial back support block 84 is replaced, the back support microcavity 85 is cleaned, the guide sleeve 7 is replaced, or the back support preload is adjusted.

[0070] Through the above feedback correction, the three-hole machining of the aluminum alloy inner fastener 11 can be transformed from single-process control to closed-loop control oriented towards the final size and hole quality after conductive oxidation.

[0071] The above embodiments are used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent substitutions or modifications made under the concept of the present invention to the reference positioning method, guide sleeve arrangement method, sacrificial back support block structure, back support microcavity shape, chip removal method, post-hole detection method, pre-conductive oxidation aperture compensation method, or feedback correction method should be included within the scope of protection of the present invention.

Claims

1. A method for machining three holes in an aluminum alloy internal fastener to prevent burrs and maintain diameter, characterized in that, The aluminum alloy inner fastener has a reference surface, an inner cavity, a central hole on the same side, and two side holes, and the aluminum alloy inner fastener undergoes conductive oxidation treatment after machining; the method includes the following steps: S10, obtain the final hole diameter requirements, hole position requirements, reference requirements, burr-free requirements for the inner cavity of the aluminum alloy fastener, and the change in hole diameter before and after conductive oxidation. S20 performs rough machining of the outer shape, pre-machining of the reference surface and pre-machining of the inner cavity on the aluminum alloy inner fastener blank, and reserves finishing allowance in the middle hole, two side holes and the hole opening area. S30, the aluminum alloy inner fastener is installed into the three-hole diameter-maintaining and anti-burr processing fixture, the fixture coordinate system is established with the reference surface and the side profile, and a controlled clamping state is formed through the low deformation clamping component; S40, aligning the three replaceable guide sleeves on the inlet-side guide plate with the theoretical hole axes of the central hole and the two side holes respectively; S50, a sacrificial back support assembly is provided on the outlet side of the middle hole and the two side holes, so that the sacrificial back support block supports the area around the hole outlet and the back support micro cavity on the sacrificial back support block is opposite to the corresponding hole outlet area. S60, the middle hole and two side holes are machined in the same fixture coordinate system, and the chips in the hole are discharged through the negative pressure chip removal channel or the directional air blowing channel during the hole machining process; S70, the machined intermediate hole and two side holes are inspected for hole diameter, effective hole depth, continuity status, hole burrs and internal debris; S80, based on the test results, perform micro-finishing of the orifice, reverse deburring, or internal cleaning of the orifice; S90, conductive oxidation treatment is applied to the aluminum alloy inner fasteners; S100 performs a final check on the hole diameter, orifice burrs, internal cavity cleanliness, and residual state of the middle hole and two side holes after conductive oxidation treatment. The check results are used to correct the hole diameter control value before conductive oxidation in subsequent batches, or to determine the replacement, cleaning, or adjustment status of the guide sleeve or sacrificial back support assembly.

2. The method for machining three holes for diameter protection and burr prevention of aluminum alloy internal fasteners according to claim 1, characterized in that, The change in pore diameter before and after conductive oxidation is determined by historical samples or trial-processed samples under the same material and surface treatment conditions; for the i-th pore, the pore diameter control value Dpre,i before conductive oxidation satisfies: Dpre,i=Dfin,i-ΔDi Where Dfin,i is the final target value of the ith hole diameter, and ΔDi is the change in ith hole diameter during conductive oxidation and cleaning. ΔDi is determined by the statistical difference between the ith hole diameter Dox,i after conductive oxidation and the ith hole diameter Dmach,i before conductive oxidation, i.e., ΔDi=mean(Dox,i-Dmach,i), and ΔDi is allowed to be positive, zero or negative.

3. The method for machining three holes for diameter protection and burr prevention of aluminum alloy internal fasteners according to claim 1, characterized in that, The fixture coordinate system is established by a reference surface positioning component, a lateral limiting component, and at least one anti-rotation limiting component; the reference surface positioning component is used to mate with the reference surface of the aluminum alloy inner fastener, the lateral limiting component is used to limit the offset of the aluminum alloy inner fastener in the direction of the hole center line or perpendicular to the hole center line, and the anti-rotation limiting component is used to limit the rotation of the aluminum alloy inner fastener relative to the fixture coordinate system.

4. The method for machining aluminum alloy internal fasteners with three holes for diameter protection and burr prevention according to claim 1, characterized in that, The three replaceable guide sleeves are set on the same inlet-side guide plate and correspond to the middle hole and two side holes respectively. Before the hole is machined, the axial position of the three replaceable guide sleeves is detected by the machine tool probe, standard mandrel or guide sleeve calibration pin, and the machine tool coordinate zero point is corrected, the inlet-side guide plate is adjusted or the corresponding guide sleeve is replaced according to the detection results.

5. The method for machining three holes for diameter protection and burr prevention of aluminum alloy internal fasteners according to claim 1, characterized in that, The sacrificial back support block has a back support micro-cavity on the side facing the outlet of the aluminum alloy inner fastener hole. The back support micro-cavity includes a chip-collecting recess corresponding to the hole outlet and an orifice support ring surface surrounding the chip-collecting recess. The orifice support ring surface is used to support the material around the hole outlet, and the chip-collecting recess is used to provide clearance space for the tool protruding end and to accommodate chips or micro burrs.

6. The method for machining three holes for diameter protection and burr prevention of aluminum alloy internal fasteners according to claim 1, characterized in that, The sacrificial back support assembly includes a back support base, an elastic preload member, a back support adjustment screw, and a sacrificial back support block; the back support adjustment screw is used to adjust the contact state or back support gap between the sacrificial back support block and the outlet side surface of the aluminum alloy inner fastener hole, and the elastic preload member is used to limit the instantaneous back support force of the sacrificial back support block on the aluminum alloy inner fastener.

7. The method for machining three holes for diameter protection and burr prevention of aluminum alloy internal fasteners according to claim 1, characterized in that, The detection in S70 includes: using at least one of the following methods to determine the hole diameter, effective hole depth, continuity status, hole burrs, and internal debris: go / no-go gauge, needle gauge, airflow detection, negative pressure detection, endoscopic visual detection, or hole magnification detection; when internal debris, hole burrs, abnormal effective hole depth, abnormal continuity status, or abnormal airflow resistance are detected, S80 is executed.

8. The method for machining three holes for diameter protection and burr prevention of aluminum alloy internal fasteners according to claim 1, characterized in that, The intermediate hole is one of the following: stepped hole, countersunk hole, threaded hole, or stepped mating hole; when machining the intermediate hole, a guide bottom hole is first formed, and then hole enlargement, fine reaming, fine boring, or threading is performed; the two side holes are machined in a symmetrical alternating sequence to reduce part offset caused by unilateral cutting force.

9. The method for machining three holes for diameter protection and burr prevention of aluminum alloy internal fasteners according to claim 1, characterized in that, When aluminum alloy internal fasteners have marking areas, the marking process should be carried out before or after conductive oxidation treatment. When reviewing the marking areas, at least the clarity of the markings, burrs on the marking edges, residual powder on the markings, and the state of residue inside the holes should be checked.

10. A three-hole diameter-maintaining and burr-resistant machining fixture for implementing the method according to any one of claims 1 to 8, characterized in that, It includes a tooling base, a part positioning seat, a reference surface positioning assembly, a lateral limiting assembly, a low-deformation clamping assembly, an inlet-side guide plate, three replaceable guide sleeves, an outlet-side sacrificial back support assembly, a chip removal channel, and a post-hole inspection interface; The part positioning seat is set on the tooling base and is used to support the aluminum alloy inner fastener; The reference plane positioning component and the lateral limiting component are used to establish the clamp coordinate system of the aluminum alloy inner fastener; The low-deformation clamping assembly is used to clamp the aluminum alloy inner fastener onto the part positioning seat; The inlet-side guide plate is set on the inlet side of the hole of the aluminum alloy inner fastener, and three replaceable guide sleeves are respectively set on the inlet-side guide plate and correspond to the middle hole and two side holes respectively. The outlet-side sacrificial back support assembly is disposed on the outlet side of the hole of the aluminum alloy inner fastener, and includes sacrificial back support blocks corresponding to the middle hole and the two side holes respectively. The chip removal channel is connected to the hole processing area, and the post-hole detection interface is used to connect an airflow detection device, a negative pressure detection device, or a hole residual state detection device. The sacrificial back support block is a replaceable structure, and each sacrificial back support block is provided with a back support micro cavity opposite to the corresponding hole exit area; the back support micro cavity includes a chip-receiving recess and a hole opening support ring surface, and the material hardness of the sacrificial back support block is lower than the cutting edge hardness of the hole machining tool, and has compressive strength capable of supporting the material around the hole exit.

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