Clamp for machining mounting hole of inner cavity of branch plate and machining method

Abstract

The application discloses a kind of processing clamps and processing methods of support plate inner cavity mounting hole, comprising: bottom plate, for as structure support;First support component, set on the bottom plate, for being passed in workpiece and being supported in the support of inner ring of workpiece, first support component is opened with each support plate's circumferential distribution position and height position matching positioning slot in axial direction;Pressing assembly, for pressing in the support of inner ring of workpiece and being connected with first support piece to press tightly fixed workpiece;Second support component, set on the bottom plate, for being supported in the support of outer ring of workpiece, second support component is provided with the positioning structure matching with the circumferential distribution position and height position of each positioning slot;Positioning piece, along radial direction, is passed in positioning structure, and positioning piece sequentially includes first positioning section matched with the width of positioning slot, second positioning section matched with the size of tool for processing support plate inner cavity mounting hole, third positioning section matched with the inner diameter of positioning structure in axial direction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aero-engine, in particular, to a vane inner cavity mounting hole machining clamp. Furthermore, the present application also relates to a vane inner cavity mounting hole machining method comprising the vane inner cavity mounting hole machining clamp. BACKGROUND

[0002] Some castings of aero-engine parts need to process oil and gas pipe mounting holes in the vane inner cavity. The oil and gas pipe is connected with the turbine casing outside the mounting hole and is assembled with the power turbine bearing seat in the inner ring. It plays a connecting and bearing role in the engine. Typical parts include bearing seat support assembly, bearing casing assembly, inter-stage guide assembly and transition section assembly.

[0003] Taking the vane inner cavity mounting hole machining of a certain type of bearing seat support assembly as an example, the bearing seat support assembly is an important part of a certain type of engine. The material of the part is cast high-temperature alloy K438, which has high hardness and poor cutting performance, belonging to difficult-to-machine materials. The inner ring is assembled with the power turbine bearing seat, the outer circle is assembled with the turbine casing, and the inner and outer rings are connected by four vane plates. The external gas pipe passes through the vane plate and is connected with the power seat. The four vane plates are directly formed by casting. The diameter of the mounting hole in the vane plate is φ12, and the gap between the mounting hole and the inner wall of the vane plate is only 0.2-0.5. Due to the large angular deviation between the blank angular hole and the vane plate, when the blank angular hole is machined to φ12, the vane plate inner wall will be machined, resulting in thinning of the vane plate wall thickness and machining marks on the blank surface, with a 100% overage rate. Due to the casting deviation of the blank vane plate, the vane plate inner wall is easily scratched during the mounting hole machining process. The main reasons are: the angular deviation exists between the blank angular hole and the four blank vane plates; the gap between the φ12 hole and the vane plate inner wall is too small; and the angular position deviation between the four cast vane plates is large. SUMMARY

[0004] The present application provides a vane inner cavity mounting hole machining clamp and machining method to solve the technical problem that the gap is too small and the angular deviation is large in the prior art, which causes the vane inner cavity to be easily scratched during the machining of the oil and gas pipe mounting hole in the vane inner cavity of some castings of aero-engine parts.

[0005] According to one aspect of the present application, a vane inner cavity mounting hole machining clamp is provided, which is applied to the machining of a workpiece with a vane inner cavity in an aero-engine, comprising:

[0006] A bottom plate is used as a structural support;

[0007] A first supporting assembly is arranged on the bottom plate and is used to pass through the workpiece and support the inner ring of the workpiece. A positioning groove is formed on the first supporting assembly in the axial direction and matches the circumferential distribution position and height position of each vane plate;

[0008] The pressing assembly is used for pressing the supporting part of the inner ring of the workpiece and connecting with the first supporting part to press and fix the workpiece.

[0009] The second supporting assembly is arranged on the bottom plate and is used for supporting the supporting part of the outer ring of the workpiece. The second supporting assembly is provided with a positioning structure matched with the circumferential distribution position and the height position of each positioning groove.

[0010] The positioning member is radially arranged in the positioning structure and sequentially includes a first positioning section matched with the width of the positioning groove, a second positioning section matched with the size of a tool used for machining the mounting hole of the inner cavity of the supporting plate, and a third positioning section matched with the inner diameter of the positioning structure.

[0011] As a further improvement of the above technical solution, the pressing assembly includes a pressing plate, a stud bolt, and a first nut. The pressing plate is pressed on the supporting part of the inner ring of the workpiece. The stud bolt is arranged in the pressing plate and is threadedly connected with the first supporting assembly. The first nut is threadedly connected with the stud bolt to lock the pressing plate.

[0012] As a further improvement of the above technical solution, the machining clamp includes first cylindrical pins arranged in the pressing plate and the first supporting assembly, respectively.

[0013] As a further improvement of the above technical solution, the positioning structure includes a fixing hole arranged in the second supporting assembly and a bushing arranged in the fixing hole. The inner diameter of the bushing is matched with the outer diameter of the third positioning section.

[0014] As a further improvement of the above technical solution, the fitting gap between the first positioning section and the positioning groove is 0.002-0.012 mm, and the fitting gap between the third positioning section and the positioning structure is 0.01-0.0275 mm.

[0015] As a further improvement of the above technical solution, the top of the second supporting assembly is provided with a supporting block used for cooperating with the supporting part of the outer ring of the workpiece.

[0016] As a further improvement of the above technical solution, the two ends of the positioning groove are respectively provided with a counterbore structure with a size larger than the width of the positioning groove.

[0017] As a further improvement of the above technical solution, the diameter of the third positioning section is larger than that of the second positioning section, and the diameter of the first positioning section is smaller than that of the second positioning section.

[0018] According to another aspect of the present application, a machining method of a mounting hole of an inner cavity of a supporting plate is also provided, which includes the machining clamp of the mounting hole of the inner cavity of the supporting plate. The machining method includes:

[0019] S1. Clamping the workpiece and fixture alignment;

[0020] S2. Machining the angular hole of the workpiece mounting edge;

[0021] S3. Inserting the positioning member into the corresponding positioning groove through the positioning structure;

[0022] S4. Rotating the workpiece in the first direction to the inner cavity of the support plate to abut against the positioning member, setting the dial to zero on one side of the support plate, rotating the workpiece in the second direction to abut against the positioning member in the inner cavity of the support plate, and then reading the dial value, rotating the workpiece in the first direction to half the dial value;

[0023] S5. Clamping the workpiece and fixture alignment;

[0024] S6. Machining the mounting hole of the inner cavity of the support plate.

[0025] As a further improvement of the above technical solution:

[0026] The workpiece has four inner cavities of the support plate, and step S3 comprises:

[0027] S31. Inserting the positioning member into the corresponding positioning groove through the positioning structure in the X reverse direction and the Y direction, if all the positioning members can be inserted, then proceed to step S4, if there is a positioning member that cannot be inserted into the positioning groove, proceed to step S32;

[0028] S32. Adjusting the position of the workpiece so that the positioning groove that cannot be inserted is adjusted to the X positive direction, and then inserting the positioning member into the corresponding positioning groove again through the X reverse direction and the Y direction, if all the positioning members can be inserted, then proceed to step S4, if there is a positioning member that cannot be inserted, then the angular deviation of the workpiece support plate is too large, and the workpiece needs to be replaced, and then proceed to step S1.

[0029] The present application has the following beneficial effects:

[0030] The machining fixture supports the support part of the inner ring and the support part of the outer ring of the workpiece through the first supporting assembly and the second supporting assembly respectively, and fixes and positions the clamped workpiece through the compression assembly; the positioning groove is arranged on the first supporting assembly, the positioning structure is arranged on the second supporting assembly, the circumferential distribution positions of the positioning grooves and the circumferential distribution positions of the positioning structures are matched with the distribution positions of the inner cavities of the support plates, and the height positions are also matched; the positioning member is positioned by the positioning groove and the positioning structure, the angular position accuracy of the positioning member is ensured, the second positioning section of the positioning member simulates the insertion of the machining tool into the inner cavity of the support plate, and in the case that all the positioning members can be smoothly inserted into the inner cavity of the support plate to the positioning groove, it can be judged that the machining tool will not be machined into the inner wall of the inner cavity of the support plate in actual machining, avoiding scratching of the workpiece during machining, ensuring that the appearance quality problem of machining is excluded before part machining, improving the machining preparation and alignment efficiency, and shortening the workpiece machining time.

[0031] In addition to the above described objects, features and advantages, the present application has other objects, features and advantages. These will become apparent from the following detailed description of the application, when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated by reference herein. The drawings illustrate preferred embodiments of the present application and, together with the description, serve to explain the application.

[0033] Figure 1 is a structural schematic diagram of a machining clamp of a preferred embodiment of the present application;

[0034] Figure 2 is a G-direction sectional view of Figure 1

[0035] Figure 3 is a structural schematic diagram of a workpiece of embodiment one of the present application;

[0036] Figure 4 is an A-direction sectional view of Figure 3

[0037] Figure 5 is a process diagram of step S3 of embodiment one of the present application;

[0038] Figure 6 is a clamping scheme diagram of comparative example one;

[0039] Figure 7 is a positioning scheme diagram of comparative example one;

[0040] Figure 8 is a clamping scheme diagram of comparative example two;

[0041] Figure 9 is a positioning scheme diagram of comparative example two.

[0042] LEGEND

[0043] 1, base plate; 11, lifting ring; 12, first screw; 13, second cylindrical pin; 2, first supporting assembly; 21, positioning groove; 3, second supporting assembly; 31, bushing; 32, supporting block; 33, second screw; 4, positioning member; 41, first positioning section; 42, second positioning section; 43, third positioning section; 5, pressing plate; 6, stud bolt; 7, first nut; 8, first cylindrical pin; 9, second nut. DETAILED DESCRIPTION

[0044] The embodiments of the present application will be described in detail below with reference to the drawings, but the present application can be implemented in various different ways as defined and covered by the following description.

[0045] As​​Figures 1 to 5 The support plate inner cavity mounting hole machining clamp of the embodiment is applied to machining of a workpiece with a support plate inner cavity in an aero-engine, and comprises:

[0046] A bottom plate 1 is used as a structural support;

[0047] A first supporting assembly 2 is arranged on the bottom plate 1 and is used to pass through the workpiece and support the inner ring of the workpiece. An axial positioning groove 21 is arranged on the first supporting assembly 2 and matches the circumferential distribution position and the height position of each support plate.

[0048] A pressing assembly is used to press the supporting part of the inner ring of the workpiece and is connected with the first supporting part to press and fix the workpiece;

[0049] A second supporting assembly 3 is arranged on the bottom plate 1 and is used to support the outer ring of the workpiece. The second supporting assembly 3 is provided with a positioning structure matching the circumferential distribution position and the height position of each positioning groove 21.

[0050] A positioning part 4 is arranged along the radial direction of the positioning structure. The positioning part 4 includes a first positioning section 41 matching the width of the positioning groove 21, a second positioning section 42 matching the size of a tool used to machine the support plate inner cavity mounting hole, and a third positioning section 43 matching the inner diameter of the positioning structure.

[0051] The first supporting assembly 2 includes a cylindrical first supporting part. The top of the first supporting part is closed to facilitate connection of the pressing assembly. The second supporting assembly 3 includes a cylindrical second supporting part. The bottom plate 1 is provided with a lifting ring 11 arranged symmetrically to facilitate lifting and transfer. The bottom plate 1 is connected with the first supporting part and the second supporting part through first screws 12 and is provided with a second cylindrical pin 13 to realize positioning. It should be understood that the positioning structure and the arrangement position of the positioning groove 21 match the theoretical design position of the support plate rather than the actual position.

[0052] It can be understood that the machining clamp supports the support part of the inner ring and the support part of the outer ring of the workpiece by respectively arranging the first supporting assembly 2 and the second supporting assembly 3, clamps and positions the workpiece by the pressing assembly, and arranges the positioning groove 21 on the first supporting assembly 2 and the positioning structure on the second supporting assembly 3. The circumferential distribution positions of each positioning groove 21 and the circumferential distribution positions of each positioning structure are matched with the distribution positions of the inner cavity of the support plate, and the height positions are also matched. The positioning groove 21 and the positioning structure are used for two-point positioning of the positioning piece 4, so as to ensure the angular position accuracy of the positioning piece 4. The second positioning section 42 of the positioning piece 4 simulates the insertion of the machining tool into the inner cavity of the support plate. In the case that each positioning piece 4 can be smoothly inserted into the inner cavity of the support plate to the positioning groove 21, it can be judged that the machining tool will not be machined into the inner wall of the inner cavity of the support plate in actual machining, so as to avoid the scratch of the workpiece during machining, ensure that the poor appearance quality problem of machining is excluded before the machining of the part, improve the machining preparation and alignment efficiency, and shorten the workpiece machining time.

[0053] In the embodiment, the pressing assembly includes a pressing plate 5, a double-headed bolt 6 and a first nut 7. The pressing plate 5 is pressed onto the support part of the inner ring of the workpiece. The double-headed bolt 6 is arranged in the pressing plate 5 and is threadedly connected with the first supporting assembly 2. The first nut 7 is threadedly connected with the double-headed bolt 6 to lock the pressing plate 5. The end part of the first supporting structure is provided with a stepped structure to position the workpiece radially and ensure the concentricity. At the same time, the contact with the workpiece is more uniform in pressing and clamping stress, so as to reduce the deformation of the clamped workpiece. Further, the matching end face of the pressing plate 5 is provided with a groove matched with the stepped structure, so that the stepped structure is embedded in the groove when the pressing plate 5 is pressed onto the workpiece, so as to realize the radial positioning and matching of the two. In order to make the pressing more stable, the second nut 9 is arranged on the double-headed bolt 6 between the pressing plate 5 and the closed end face of the first supporting piece, and is screwed to abut against the first supporting piece, so as to make the first nut 7 more stable and reliable after being screwed.

[0054] In the embodiment, the diameter of the third positioning section 43 is greater than that of the second positioning section 42, and the diameter of the first positioning section 41 is smaller than that of the second positioning section 42, that is, the positioning piece 4 is a stepped pin. The positioning piece 4 is inserted from the outermost ring positioning structure. The first positioning section 41 is matched with the positioning groove 21 after passing through the positioning structure and the inner cavity of the support plate. At this time, the second positioning section 42 is inserted into the inner cavity of the support plate, and the third positioning section 43 is inserted into the positioning structure.

[0055] Further, the machining clamp includes a first cylindrical pin 8 arranged in the pressing plate 5 and the first supporting assembly 2 respectively. The pressing plate 5 and the first supporting assembly 2 are respectively provided with positioning holes. The first cylindrical pin 8 is a stepped pin, and the lower part thereof has a smaller diameter than the upper part. After the pressing plate 5 is pressed onto the workpiece, the first cylindrical pin 8 is inserted into the positioning hole of the pressing plate 5 to the positioning hole of the first supporting assembly 2 from top to bottom, so as to realize the radial positioning of the pressing plate 5 and ensure the concentricity.

[0056] In the embodiment, the positioning structure includes a fixing hole formed in the second supporting component 3 and a bushing 31 arranged in the fixing hole, and the inner diameter of the bushing 31 matches the outer diameter of the third positioning section 43; during clamping, the positioning component 4 needs to be inserted into the positioning structure to the positioning groove 21, and the inner wall of the positioning structure will be worn after long-term use, which affects the positioning accuracy. Therefore, the positioning structure is arranged as the fixing hole formed in the second supporting component 3 and the detachable bushing 31 arranged in the fixing hole, and the positioning accuracy of the positioning component 4 is ensured by the bushing 31. After wear, only the bushing 31 needs to be replaced, which is lower in maintenance cost and simpler in operation.

[0057] Similarly, the top of the second supporting component 3 is provided with a supporting block 32 connected with the second supporting component through a second screw 33, the supporting block 32 is used for cooperating with the supporting part of the outer ring of the workpiece, and the top of the supporting block 32 serves as a positioning reference. During long-term taking and placing of the workpiece, the supporting block 32 will be worn, and only the supporting block 32 needs to be replaced during later maintenance.

[0058] In the embodiment, the cooperation gap between the first positioning section 41 and the positioning groove 21 is 0.002-0.012 mm, and the cooperation gap between the third positioning section 43 and the positioning structure is 0.01-0.0275 mm, so as to reduce the positioning error; the positioning component 4 has straightness and coaxiality, and therefore the cooperation gap at the bushing 31 is greater than the cooperation gap of the positioning groove 21, so as to adjust the position and ensure accurate insertion of the positioning component 4.

[0059] In the embodiment, the two ends of the positioning groove 21 are respectively provided with a counterbore structure with a size greater than the width of the positioning groove 21. After the counterbore structure is arranged at the two ends of the positioning groove 21, the positioning groove 21 can be machined from the end part.

[0060] It can be understood that the bottom plate 1 and the clamps around and other positions are hollowed out to reduce weight; holes matched with the hole positions on the workpiece are formed on the cooperation surfaces of the clamps, and the hole diameters are increased by 1 mm compared with the hole positions on the workpiece.

[0061] The mounting hole machining method of the inner cavity of the supporting plate in the embodiment is applied to the mounting hole machining clamp of the inner cavity of the supporting plate, and the machining method comprises the following steps:

[0062] S1. Clamping the workpiece and aligning the clamp; specifically, the workpiece is pressed into the clamp and locked by the pressing plate 5; the clamping surface runout is ≤0.02, the clamp positioning circle runout is ≤0.02, and the hole F runout is ≤0.05;

[0063] S2. Machining the angular hole of the workpiece mounting edge; the blank angular hole is converted into a precision hole to define the angular direction;

[0064] S3. Inserting the positioning component 4 into the corresponding positioning groove 21 through the positioning structure;

[0065] S4. Rotate the workpiece in the first direction to the close-fitting positioning member 4 in the inner cavity of the support plate, set the dial gauge on the side of the support plate to zero, rotate the workpiece in the second direction to the close-fitting positioning member 4 in the inner cavity of the support plate to read the dial gauge value, and rotate the workpiece in the first direction to half the dial gauge value. After this step, the second positioning section 42 of the positioning member 4 is located in the middle of the inner cavity of the support plate, and the clamping state is maintained to effectively avoid tool scratches in the inner cavity of the support plate in subsequent machining;

[0066] S5. Clamping the workpiece and fixture alignment; keep the current circumferential position of the workpiece, lock the pressing plate 5; align the fixture support surface runout ≤0.02, align the workpiece first reference D runout ≤0.02; align the angular hole A reference after processing in step S2;

[0067] S6. Machining the mounting hole of the support plate inner cavity.

[0068] Example one

[0069] This embodiment applies the fixture and machining method of the preferred embodiment described above, and the machined workpiece is a bearing seat support assembly, which is assembled with the inner ring and the power turbine bearing seat, the outer circle is assembled with the turbine casing, the inner and outer rings are connected by four support plates, the external air pipe passes through the support plate and is connected with the power seat, the four support plates are directly formed by casting, the diameter of the mounting hole in the support plate is φ12, and the gap between the mounting hole and the inner wall of the support plate inner cavity is only 0.2-0.5mm, and the angular relationship between the blank angular hole and the support plate is too large;

[0070] The fixture is designed with four wide φ6 positioning grooves 21 and φ14 bushings 31, and the relative axial position of the positioning grooves 21 and the bushings 31 is consistent with the theoretical position of the distance from the center of the inner cavity of the workpiece support plate to the first reference D; the positioning groove 21 is gap fitted with the first positioning section 41 (single side 0.002-0.012mm), the bushing 31 is gap fitted with the third positioning section 43 (single side 0.01-0.0275mm), and the blank support plate bottom hole is φ8;

[0071] After the hole of the φ12 blank angular hole is aligned in step S1, the angular hole is finished in step S2;

[0072] It should be noted that the workpiece has four support plate inner cavities, and the bearing seat support assembly, the load-bearing casing assembly, the inter-stage guide assembly, and the transition section assembly in the prior art all have four inner cavities, which are uniformly distributed at an angle of 90°, as shown in Figure 5 , step S3 includes:

[0073] S31. Insert the positioning member 4 into the corresponding positioning groove 21 from the X reverse and Y direction positioning structure, if the positioning member 4 can be inserted, proceed to step S4, if there is a positioning member 4 that cannot be inserted into the positioning groove 21, proceed to step S32;

[0074] S32. Adjust the workpiece position so that the positioning slot 21 that cannot be inserted is adjusted to the X positive direction, and the positioning piece 4 is inserted into the corresponding positioning slot 21 again from the X negative direction and the Y direction. If all the positioning pieces 4 can be inserted, proceed to step S4. If there is a positioning piece 4 that cannot be inserted, the workpiece support plate angular deviation is too large, and the workpiece needs to be replaced, and proceed to step S1.

[0075] It should be noted that the oil and gas pipe mounting hole of the workpiece has different hole diameters. In step S3, the positioning pin that cannot be inserted is adjusted to the X positive direction, and the positioning piece 4 is inserted into the other support plate inner cavity. In the case that the positioning piece 4 can be smoothly inserted into the other three support plate inner cavities, the support plate inner cavity in the X positive direction is used as the machining position of the mounting hole with the smallest hole diameter, which can effectively prevent the workpiece from being scratched and ensure that the workpiece is smoothly machined.

[0076] After completing the workpiece machining through steps S3-S6, the inner wall of the workpiece support plate inner cavity is not scratched, the quality is stable, and the qualified rate is 100%.

[0077] Comparative Example 1

[0078] In this comparative example, reference is made to Figure 6 and Figure 7 The difference between this example and Example 1 is that the four φ8 angular pins are inserted into the angular holes and the 6mm wide vertical slots fixed in the center of the fixture are inserted, and the four angular pins are inserted into the angular holes. Since the φ8 blank hole tolerance is too large, the workpiece can still be rotated greatly after the angular pin is inserted, the distance between the φ8 blank hole and the slot on the fixture is too short, and the angular pin cannot be rotated, and the support plate is a special-shaped support plate, and the angular hole is used as the angular hole. The axial position of the hole cannot be determined, therefore, the clamping scheme of Comparative Example 1 has scratches on the inner wall of the workpiece, the depth is relatively deep, and there is no obvious rule.

[0079] Comparative Example 2

[0080] In this comparative example, reference is made to Figure 8 and Figure 9 The difference between this example and Example 1 is that the four blank support plates are used to determine the angular direction, the four external height-adjustable sliders are used to fix the axial height, the four φ12 angular pins are inserted into the support plates through the positioning holes of the sliders, and the milling cutter and the angular pin are in the same position during subsequent machining. However, the length of the positioning hole of the external slider is too short, resulting in a jump of 0.8mm between the end and the front end of the angular pin, which cannot achieve the angular positioning function, therefore, the inner wall of the workpiece machined by the scheme of Comparative Example 2 is partially machined, the depth is relatively shallow, and the quality stability is poor.

[0081] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A support plate inner cavity mounting hole processing clamp applied to the processing of a workpiece with a support plate inner cavity in an aero-engine, characterized in that, The application relates to a machining clamp for machining mounting holes in an inner cavity of a support plate. The machining clamp comprises a bottom plate (1) for serving as a structural support; a first supporting assembly (2) arranged on the bottom plate (1) and used for supporting a supporting part of an inner ring of a workpiece; a pressing assembly used for pressing the supporting part of the inner ring of the workpiece and connected with the first supporting assembly (2) to press and fix the workpiece; a second supporting assembly (3) arranged on the bottom plate (1) and used for supporting a supporting part of an outer ring of the workpiece; a positioning member (4) arranged in the positioning structure in a radial direction and sequentially comprising a first positioning section (41) matched with the width of the positioning slot (21), a second positioning section (42) matched with the size of a tool used for machining the mounting hole in the inner cavity of the support plate, and a third positioning section (43) matched with the inner diameter of the positioning structure. The pressing assembly comprises a pressing plate (5) pressed on the supporting part of the inner ring of the workpiece, a stud bolt (6) arranged in the pressing plate (5) and threadedly connected with the first supporting assembly (2), and a first nut (7) threadedly connected with the stud bolt (6) to lock the pressing plate (5). The machining clamp comprises a first cylindrical pin (8) arranged in the pressing plate (5) and the first supporting assembly (2) respectively. The positioning structure comprises a fixing hole arranged in the second supporting assembly (3) and a bushing (31) arranged in the fixing hole, and the inner diameter of the bushing (31) is matched with the outer diameter of the third positioning section (43). The matching gap between the first positioning section (41) and the positioning slot (21) is 0.002-0.012 mm, and the matching gap between the third positioning section (43) and the positioning structure is 0.01-0.0275 mm.

2. The strut lumen mounting hole machining fixture of claim 1, wherein, The top of the second supporting assembly (3) is provided with a supporting block (32) used for matching with the supporting part of the outer ring of the workpiece.

3. The strut lumen mounting hole machining fixture of claim 2, wherein, The two ends of the positioning slot (21) are respectively provided with hole expansion structures with a size larger than the width of the positioning slot (21).

4. The strut lumen mounting hole machining fixture of claim 1, wherein, The diameter of the third positioning section (43) is larger than that of the second positioning section (42), and the diameter of the first positioning section (41) is smaller than that of the second positioning section (42).

5. The strut lumen mounting hole machining fixture of Claim 1, wherein, The machining method is applied to the machining clamp for machining the mounting hole in the inner cavity of the support plate, and the machining method comprises the following steps:

6. The strut lumen mounting hole machining fixture of Claim 1, wherein, S1, clamping the workpiece and the clamp and aligning; 7. The strut lumen mounting hole machining fixture of Claim 1, wherein, S2, machining an angular hole of a mounting edge of the workpiece; 8. The strut lumen mounting hole machining fixture of Claim 1, wherein, S3, inserting the positioning member into the corresponding positioning slot through the positioning structure; 9. A method for machining mounting holes in the inner cavity of a support plate, characterized in that: S4, rotating the workpiece to the inner cavity of the support plate in a first direction until the inner cavity of the support plate abuts against the positioning member, reading a zero value of a pressure gauge, rotating the workpiece to the inner cavity of the support plate in a second direction until the inner cavity of the support plate abuts against the positioning member, reading a pressure gauge value, and rotating the workpiece to a half pressure gauge value in the first direction; S5, clamping the workpiece and the clamp and aligning; S6, machining the mounting hole in the inner cavity of the support plate. ​ ​ ​ ​ 10. The method of strut inner cavity mounting hole machining according to claim 9, wherein, The workpiece has four inner cavities of supporting plates, and step S3 comprises: S31. Inserting the positioning members into the corresponding positioning grooves from the X reverse and Y direction positioning structure, if all the positioning members can be inserted, then turn to step S4, if there is a positioning member that cannot be inserted into the positioning groove, turn to step S32; S32. Adjusting the position of the workpiece, so that the positioning groove that cannot be inserted is adjusted to the X positive direction, and then inserting the positioning members into the corresponding positioning grooves from the X reverse and Y direction again, if all the positioning members can be inserted, then turn to step S4, if there is a positioning member that cannot be inserted, then the angular deviation of the workpiece supporting plate is too large, the workpiece is replaced, and then turn to step S1.

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