A processing technology of a sealing bushing

Abstract

This application belongs to the field of mechanical seal technology and provides a processing technology for a sealing bushing, including S1: joining a stainless steel sleeve with a step on one side and a graphite sleeve together to form a sealing bushing, wherein the outer diameter tolerance of the stainless steel sleeve is 0.03mm; S2: machining the inner hole of the graphite sleeve: using the outer diameter of the stainless steel sleeve as a reference, a tooling fixture is used to fit the graphite sleeve onto the outer circumference of the sealing bushing, wherein the gap between the outer diameter of the stainless steel sleeve and the inner diameter of the tooling fixture is D1, where 0.03mm < D1 ≤ 0.05mm. The inner diameter of the graphite sleeve is then precision machined on a machine tool using a fixture for mounting the sealing bushing. The coaxiality of the fixture and the machine tool's rotating axis is less than or equal to 0.01 mm. S3: Machining the outer hole of the stainless steel sleeve: One end of the mandrel, after wire cutting, is inserted into the inner diameter of the graphite sleeve. The gap between the outer diameter of the mandrel and the inner diameter of the machined graphite sleeve hole is D2, 0 ≤ D2 ≤ 0.01 mm. Both ends of the mandrel are held in place by ejector pins. A floating fixture is connected at the step of the stainless steel sleeve. The three-jaw chuck of the machine tool drives the sealing bushing to rotate through the floating fixture, simultaneously precision machining the outer diameter of the stainless steel sleeve. The advantage of this application is that the above production process ensures that the dimensional accuracy of the stainless steel sleeve and graphite sleeve after production meets the dimensional requirements.

Description

Technical Field

[0001] This application belongs to the field of mechanical seal technology, specifically relating to a processing technology for a sealing bushing. Background Technology

[0002] A composite sealing bushing, such as Figure 1 As shown, the composite bushing consists of two parts: an outer stainless steel sleeve 1 made of SS31 stainless steel and an inner graphite sleeve 2 made of imported graphite material. The stainless steel sleeve 1 and the graphite sleeve 2 are joined together by a heat fitting process and fixed by hammering in a pin 3. This type of sealing bushing uses the rotational seal between the graphite sleeve 2 and the bearing, which can withstand high temperatures, has a small coefficient of expansion, and good corrosion resistance. Furthermore, the stainless steel sleeve 1 is fitted on the outside of the graphite sleeve 2, resulting in high structural strength. Therefore, the working performance is stable and reliable, and it has been widely used.

[0003] However, this type of sealing bushing has high requirements for dimensional accuracy. The tolerance between the outer diameter of the stainless steel sleeve 1 and the inner hole of the graphite sleeve 2 is required to be between 0.01mm and 0.03mm. At the same time, the coaxiality between the outer diameter of the stainless steel sleeve 1 and the inner hole of the graphite sleeve 2 is required to be no more than 0.01mm. Conventional processing technology can no longer meet these requirements. Summary of the Invention

[0004] The purpose of this application is to provide a processing technology for sealing bushings, which ensures that the dimensional accuracy of the stainless steel bushings and graphite bushings after production meets the dimensional requirements.

[0005] The technical solution adopted by this application to solve the above-mentioned technical problems is as follows: A processing technology for a sealing bushing is proposed, including:

[0006] S1: A stainless steel sleeve with a step on one side and a graphite sleeve are joined together to form a sealing bushing. The outer diameter tolerance of the stainless steel sleeve is 0.03mm.

[0007] S2: Machining the inner hole of the graphite sleeve: Using the outer diameter of the stainless steel sleeve as a reference, the tooling fixture is fitted onto the outer circumference of the sealing bushing. The gap between the outer diameter of the stainless steel sleeve and the inner diameter of the tooling fixture is D1, 0.03mm < D1 ≤ 0.05mm. Then, the tooling fixture fitted onto the sealing bushing is clamped on the machine tool to finish machine the inner diameter of the graphite sleeve. The coaxiality between the tooling fixture and the rotating shaft of the machine tool is less than or equal to 0.01mm.

[0008] S3: Machining the outer hole of the stainless steel sleeve: Insert one end of the mandrel after wire cutting into the inner diameter of the graphite sleeve. The gap between the outer diameter of the mandrel and the inner diameter of the machined graphite sleeve hole is D2, 0≤D2≤0.01mm. Hold both ends of the mandrel with ejector pins. Connect a floating fixture at the step of the stainless steel sleeve. Use the three-jaw chuck of the machine tool to drive the sealing bushing to rotate through the floating fixture. At the same time, the outer diameter of the stainless steel sleeve is precision machined.

[0009] Based on the above technical features, the outer diameter tolerance of the stainless steel sleeve formed by rough machining is 0.03mm. During the finish machining of the graphite sleeve's inner diameter, a tooling fixture is fitted onto the outside of the stainless steel sleeve, and the sealing bushing is clamped onto a three-jaw chuck using the tooling fixture, thus preventing wear on the outer diameter of the stainless steel sleeve by the three-jaw chuck. The clearance D1 between the tooling fixture and the stainless steel sleeve is 0.03mm < D1 ≤ 0.05mm. When the outer diameter of the stainless steel sleeve deviates by 0.015mm to both sides during rough machining, the clearance between the tooling fixture and the stainless steel sleeve ensures proper fit between the sealing bushing and the stainless steel sleeve. Furthermore, during the machining process, the coaxiality of the tooling fixture and the machine tool's rotating axis is less than or equal to 0.01mm. If the outer diameter of the stainless steel sleeve and the outer diameter of the tooling fixture are tightly fitted, the tolerance of the inner diameter of the graphite sleeve is also due to the coaxiality, i.e., 0.01mm. Considering the gap between the outer diameter of the stainless steel sleeve and the tooling fixture, the coaxiality tolerance of 0.01mm plus the outer diameter gap of 0.02mm means that the tolerance of the inner diameter of the graphite sleeve is between 0.01mm and 0.03mm, which meets the production requirements. After the inner diameter of the graphite sleeve is machined, the wire-cut mandrel is inserted and fixed to the graphite sleeve. The outer diameter of the stainless steel sleeve is then precision machined using the graphite sleeve as a reference to ensure that the machining tolerance of the outer diameter of the stainless steel sleeve is 0.01mm to 0.03mm. The gap between the outer diameter of the mandrel and the inner diameter of the machined graphite sleeve hole is D2, where 0≤D2≤0.01mm. This ensures that the coaxiality of the stainless steel sleeve and the graphite sleeve after production does not exceed 0.01mm, guaranteeing the production and processing accuracy.

[0010] Preferably, in step S1, the processing technology of the sealing bushing is as follows:

[0011] B1: Take a section of stainless steel pipe and machine it on a lathe to form a stainless steel sleeve with a stepped outer diameter. Leave a 0.3mm allowance for the outer diameter of the stainless steel sleeve and the outer diameter tolerance of the stainless steel sleeve is 0.03mm.

[0012] B2: Graphite sleeve formed by powder metallurgy, with a 0.5mm allowance in the inner diameter of the graphite sleeve;

[0013] B3: Utilizing the different thermal shrinkage ratios of stainless steel and graphite, a graphite sleeve is fitted inside a stainless steel sleeve using a heat-fitting process.

[0014] B4: Drill a fixing hole radially on the outer peripheral wall of the stainless steel sleeve. The fixing hole penetrates the stainless steel sleeve and extends to the outer peripheral wall of the graphite sleeve, but does not penetrate the outer peripheral wall of the graphite sleeve. Then, hammer a pin into the fixing hole, laser weld the pin and the fixing hole, and rough machine the laser welded area to ensure that the stainless steel sleeve is flat at the laser welded area.

[0015] Based on the aforementioned technical features, after rough machining of the stainless steel sleeve and the graphite sleeve, they are assembled together using a heat-fitting process. Then, pins are used to secure the graphite sleeve and the stainless steel sleeve, completing the production of the sealing bushing. During the rough machining of the stainless steel sleeve and the graphite sleeve, repeated experiments revealed that a 0.3mm allowance for the outer diameter of the stainless steel sleeve and a 0.5mm allowance for the inner diameter of the graphite sleeve are most beneficial for positioning during the subsequent precision machining of the sealing bushing and for ensuring its machining accuracy.

[0016] Preferably, in step S2, the tooling fixture includes a reference sleeve and a threaded locking cylinder. The reference sleeve includes an integrally connected sleeve portion and a positioning portion. The sleeve portion is axially fitted with the outer peripheral wall of the stainless steel sleeve, and one end of the sleeve portion abuts against the stepped side of the stainless steel sleeve. The positioning portion abuts against the end of the stainless steel sleeve away from the stepped side. The threaded locking cylinder is threadedly connected to the end of the reference sleeve away from the positioning portion. The reference sleeve is used to connect with the three-jaw chuck of the machine tool.

[0017] With the above technical features, when precision machining the inner diameter of the graphite sleeve, the outer circumference of the sealing bushing is set using a tooling fixture, and then one end of the reference sleeve is clamped onto a three-jaw chuck to precision machine the inner diameter of the graphite sleeve. After machining, only the threaded locking sleeve needs to be removed to replace the product before machining the next graphite sleeve, avoiding repeated clamping and improving production efficiency.

[0018] Preferably, the tooling fixture further includes a transition sleeve, which is fitted around the outer periphery of the stainless steel sleeve and located between the stainless steel sleeve and the sleeve portion.

[0019] Through the above technical features, the reference sleeve can be used for sealing sleeves of different radial dimensions by means of the transition sleeve, thereby improving the applicability of the tooling fixture.

[0020] Preferably, the tooling fixture further includes an annular gasket, which abuts against the end of the sealing bushing away from the positioning part, and the gasket abuts between the sealing bushing and the threaded locking cylinder.

[0021] Through the above technical features, the reference sleeve can be used for sealing sleeves with different axial dimensions by means of a gasket, further improving the applicability of tooling fixtures.

[0022] Preferably, in step S3, the mandrel includes an integrally connected stepped portion and a plug portion. The stepped portion and the plug portion are both coaxially arranged columnar structures, and the outer diameter of the stepped portion is larger than the outer diameter of the plug portion. A positioning hole is provided at the axial center of the end of the stepped portion away from the plug portion, and a plug hole is provided at the axial center of the plug portion, which passes through the plug portion. The plug portion is cut into several parts by wire cutting at the axial center.

[0023] Through the above technical features, the gap between the outer diameter of the mandrel and the inner diameter of the machined graphite sleeve hole is D2, 0≤D2≤0.01mm, which facilitates the insertion of the mandrel into the graphite sleeve. Then, the mandrel after wire cutting is held tightly in the graphite sleeve by inserting a pin through the insertion hole, which plays a role in fixing the graphite sleeve. The mandrel is also fixed by pins at both ends, ensuring the coaxiality between the mandrel and the stainless steel sleeve during the processing, i.e., the coaxiality between the stainless steel sleeve and the graphite sleeve.

[0024] Preferably, the gap of the mandrel wire cutting is 0.01 mm.

[0025] The above technical features ensure that the mandrels will not disperse after wire cutting, and that the mandrels can be tightly held in the graphite sleeve after the ejector pin is inserted into the insertion hole.

[0026] Preferably, in step S3, the pins at both ends of the mandrel are a first pin and a second pin, respectively. The first pin abuts against the positioning hole, and one end of the second pin extends into and is inserted into the insertion hole.

[0027] Through the aforementioned technical features, the first and second ejector pins fix the mandrel axially, ensuring the coaxiality of the stainless steel sleeve with the mandrel during the machining of the outer diameter.

[0028] Preferably, in step S3, a positioning block is slidably connected to the machine tool, and a snap-fit ​​assembly for fixing the positioning block to the machine tool is provided. The positioning block is provided with some rotating holes facing the three-jaw chuck. The rotating holes are coaxially arranged with the three-jaw chuck, and a bearing is provided in the rotating holes. One end of the first ejector pin is snapped into the three-jaw chuck, and one end of the second ejector pin is rotatably connected in the rotating hole.

[0029] Through the aforementioned technical features, the rotation of the three-jaw chuck drives the first ejector pin to rotate relative to the positioning hole, and also drives the second ejector pin to rotate around the rotating hole, enabling the cutting tool to perform static machining on the outer diameter of the stainless steel sleeve. The positioning block is slidably connected to the machine tool, and the position of the positioning hole can be flexibly adjusted according to the length of the sealing sleeve, thus accommodating sealing sleeves of different sizes.

[0030] Preferably, in step S3, the floating fixture includes an annular fixed sleeve and a plurality of fixed posts evenly distributed circumferentially on the fixed sleeve, and an abutment post connected to the fixed sleeve and extending axially. The fixed sleeve is provided with threaded holes corresponding to the fixed posts, and the fixed posts are threadedly connected to the threaded holes. The fixed posts are used to lock the fixed sleeve to the stepped portion, and the abutment post is used to abut against one side of the jaws of the machine tool three-jaw chuck.

[0031] Using the above-mentioned technical features, the fixing sleeve is fitted onto the outer periphery of the step portion, and then the fixing column is rotated so that the fixing column abuts against the outer periphery of the step portion, locking the fixing sleeve at the step portion. Then, the abutting column is pressed against one side of the jaw of the three-jaw chuck. During the rotation of the three-jaw chuck, the abutting column is pushed to rotate, thereby driving the mandrel and sealing bushing to rotate synchronously.

[0032] In summary, this application has the following beneficial effects:

[0033] (1) The above-mentioned production process can achieve a tolerance of 0.01mm to 0.03mm between the outer diameter of the stainless steel sleeve and the inner diameter of the graphite sleeve, and the coaxiality of the outer diameter of the stainless steel sleeve and the inner diameter of the graphite sleeve does not exceed 0.01mm. Moreover, the production process is simple and convenient and the production efficiency is high.

[0034] (2) When processing sealing bushings of different sizes, the tooling fixture of this application can be used to process the next graphite bushing by simply removing the threaded locking sleeve and replacing the product, avoiding repeated clamping, resulting in high production efficiency. Furthermore, by setting transition sleeves and gaskets, the applicability of the tooling fixture is improved.

[0035] (3) This application uses the mandrel after wire cutting to fix the sealing bushing, and the fixing of the mandrel by the pins on both sides of the mandrel ensures the coaxiality of the outer diameter of the stainless steel sleeve and the inner diameter of the graphite sleeve. Attached Figure Description

[0036] Figure 1 This is a cross-sectional structural diagram of the sealing bushing of this application;

[0037] Figure 2 A cross-sectional structural diagram of the tooling fixture and sealing bushing according to one embodiment of this application;

[0038] Figure 3 This is a schematic diagram of the structure of a machine tool according to one embodiment of this application;

[0039] Figure 4 This is a schematic diagram of the structure of a core rod according to one embodiment of this application;

[0040] Figure 5 A schematic diagram of the mandrel and sealing bushing according to one embodiment of this application;

[0041] Figure 6 This is a structural schematic diagram of a floating fixture according to one embodiment of this application.

[0042] In the diagram, 1. Stainless steel sleeve; 11. Step; 12. Fixing hole; 2. Graphite sleeve; 3. Pin; 4. Tooling fixture; 41. Reference sleeve; 411. Sleeve part; 412. Positioning part; 42. Threaded locking sleeve; 43. Transition sleeve; 44. Washer; 5. Mandrel; 51. Step part; 511. Positioning hole; 52. Insertion part; 521. Insertion hole; 6. Floating fixture; 61. Fixing sleeve; 611. Threaded hole; 612. Abutment post; 62. Fixing post; 7. Machine tool; 71. Three-jaw chuck; 72. First ejector pin; 73. Second ejector pin; 74. Positioning block. Detailed Implementation

[0043] The following are specific embodiments of this application, which are described in conjunction with the accompanying drawings to further illustrate the technical solutions of this application. However, this application is not limited to these embodiments.

[0044] This application discloses a processing technology for a sealing bushing, including:

[0045] B1: Take a section of stainless steel pipe and process it on a lathe to form a stainless steel sleeve 1 with a stepped outer diameter 11. Leave a 0.3mm allowance for the outer diameter of the stainless steel sleeve 1.

[0046] B2: Graphite sleeve 2 is formed by powder metallurgy, with a 0.5mm allowance in the inner diameter of graphite sleeve 2;

[0047] B3: Utilizing the different thermal shrinkage ratios of stainless steel and graphite, the graphite sleeve 2 is fitted inside the stainless steel sleeve 1 through a heat fitting process.

[0048] B4: Drill a fixing hole 12 radially on the outer peripheral wall of the stainless steel sleeve 1. The fixing hole 12 penetrates the stainless steel sleeve 1 and extends to the outer peripheral wall of the graphite sleeve 2, but does not penetrate the outer peripheral wall of the graphite sleeve 2. Then, hammer a pin 3 into the fixing hole 12, laser weld the pin 3 and the fixing hole 12, and perform rough machining on the laser welded area to ensure that the stainless steel sleeve 1 is flat at the laser welded area.

[0049] After rough machining of the stainless steel sleeve 1 and graphite sleeve 2 using the above processing technology, the stainless steel sleeve 1 and graphite sleeve 2 are assembled together using a hot fitting process. Then, the graphite sleeve 2 and stainless steel sleeve 1 are fixed by a pin 3, thus completing the production of the sealing bushing.

[0050] After the sealing bushing fixing sleeve 61 is installed, the outer diameter of the stainless steel sleeve 1 and the inner diameter of the graphite sleeve 2 are precision machined.

[0051] The machining process for the inner diameter of the graphite sleeve 2 is as follows: taking the outer diameter of the stainless steel sleeve 1 as the reference, the tooling fixture 4 is fitted onto the outer circumference of the sealing bushing. The gap between the outer diameter of the stainless steel sleeve 1 and the inner diameter of the tooling fixture 4 is D1, 0.03mm < D1 ≤ 0.05mm. Then, the tooling fixture 4 fitted onto the sealing bushing is clamped on the machine tool 7 to perform precision machining on the inner diameter of the graphite sleeve 2. The coaxiality of the rotating shaft of the tooling fixture 4 and the machine tool 7 is less than or equal to 0.01mm.

[0052] The outer diameter tolerance of the stainless steel sleeve 1, formed by rough machining, is 0.03 mm. During the finish machining of the inner diameter of the graphite sleeve 2, a fixture 4 is fitted onto the outside of the stainless steel sleeve 1, and the sealing bushing is clamped onto a three-jaw chuck 71 using the fixture 4, preventing wear on the outer diameter of the stainless steel sleeve 1 by the three-jaw chuck 71. The clearance D1 between the fixture 4 and the stainless steel sleeve 1 is 0.03 mm < D1 ≤ 0.05 mm. When the outer diameter of the stainless steel sleeve 1 shifts 0.015 mm to either side during rough machining, the clearance between the fixture 4 and the stainless steel sleeve 1 ensures proper fit between the sealing bushing and the stainless steel sleeve 1. Furthermore, during the machining process, the coaxiality of the tooling fixture 4 and the rotating axis of the machine tool 7 is less than or equal to 0.01mm. If the outer diameter of the stainless steel sleeve and the outer diameter of the tooling fixture 4 are tightly fitted, the tolerance of the inner diameter of the graphite sleeve 2 is caused by the coaxiality, i.e., 0.01mm. Considering that there is a gap between the outer diameter of the stainless steel sleeve 1 and the tooling fixture 4, the coaxiality tolerance of 0.01mm plus the outer diameter gap of 0.02mm means that the tolerance of the inner diameter of the graphite sleeve 2 is between 0.01mm and 0.03mm, which meets the production requirements.

[0053] like Figure 2 As shown, the tooling fixture 4 used in the above-mentioned graphite inner diameter machining process includes a reference sleeve 41 and a threaded locking cylinder 42. The reference sleeve 41 includes an integrally connected sleeve portion 411 and a positioning portion 412. The sleeve portion 411 is axially fitted onto the outer peripheral wall of the stainless steel sleeve 1. One end of the sleeve portion 411 abuts against one side of the step 11 of the stainless steel sleeve 1. The positioning portion 412 abuts against the end of the stainless steel sleeve 1 away from the step 11. The threaded locking cylinder 42 is threadedly connected to the end of the reference sleeve 41 away from the positioning portion 412. The reference sleeve 41 is used to connect with the three-jaw chuck 71 of the machine tool 7. Thus, by clamping the reference sleeve 41 with the three-jaw chuck 71, wear on the outer diameter of the stainless steel sleeve 1 is avoided. The inner diameter of the graphite sleeve 2 is precision machined by clamping one end of the reference sleeve 41 onto the three-jaw chuck 71. After machining, only the threaded locking cylinder 42 needs to be removed to replace the product before machining the next graphite sleeve 2, avoiding repeated clamping and improving production efficiency.

[0054] The tooling fixture 4 also includes a transition sleeve 43 that fits between the stainless steel sleeve 1 and the sleeve portion 411, making the tooling fixture 4 suitable for sealing bushings of different radial dimensions; the tooling fixture 4 also includes a gasket 44 that abuts against the sealing bushing and the threaded locking sleeve 42, making the tooling fixture 4 suitable for sealing bushings of different axial dimensions, thus providing the applicability of the tooling fixture 4.

[0055] The machining process of the outer diameter of the stainless steel sleeve 1 is as follows: the end of the mandrel 5 after wire cutting is inserted into the inner diameter of the graphite sleeve 2. The gap between the outer diameter of the mandrel 5 and the inner diameter of the machined graphite sleeve 2 hole is D2, 0≤D2≤0.01mm. The two ends of the mandrel 5 are respectively held by the ejector pin. The floating fixture 6 is connected at the step 11 of the stainless steel sleeve 1. The three-jaw chuck 71 of the machine tool 7 drives the sealing bushing to rotate through the floating fixture 6. At the same time, the outer diameter of the stainless steel sleeve 1 is precision machined.

[0056] After the inner diameter of the graphite sleeve 2 is machined, the wire-cut mandrel 5 is inserted and fixed to the graphite sleeve 2. The outer diameter of the stainless steel sleeve 1 is precision machined with the graphite sleeve 2 as the reference to ensure that the machining tolerance of the outer diameter of the stainless steel sleeve 1 is 0.01mm to 0.03mm. The gap between the outer diameter of the mandrel 5 and the inner diameter of the machined graphite sleeve 2 hole is D2, 0≤D2≤0.01mm, to ensure that the coaxiality of the stainless steel sleeve 1 and the graphite sleeve 2 after production does not exceed 0.01mm, thus ensuring the production and processing accuracy.

[0057] like Figure 3 As shown, the tooling fixture 4 used in the machining process of the outer diameter of the stainless steel sleeve 1 includes a machine tool 7 connected to a three-jaw chuck and a mandrel 5.

[0058] like Figure 4 , Figure 5 As shown, the core rod 5 includes an integrally connected stepped portion 51 and a plug portion 52. Both the stepped portion 51 and the plug portion 52 are coaxially arranged columnar structures, and the outer diameter of the stepped portion 51 is larger than the outer diameter of the plug portion 52. A positioning hole 511 is provided at the axial center of the end of the stepped portion 51 away from the plug portion 52. A plug hole 521 is provided at the axial center of the plug portion 52, which passes through the plug portion 52. The plug portion 52 is cut into several parts by wire cutting at the axial center.

[0059] The mandrel 5 connects one end of the insertion part 52 into the graphite sleeve 2 of the sealing bushing, then the first ejector pin 72 abuts against the positioning hole 511 of the step 11 and engages the first ejector pin 72 with the three-jaw chuck 71, then the second ejector pin 73 is inserted into the insertion hole 521, so that the insertion part 52 of the mandrel 5 is separated and tightened at the insertion hole 521 along the line cut, and one end of the second ejector pin 73 is rotatably connected to the rotating hole of the positioning block 74.

[0060] like Figure 6As shown, when the floating fixture 6 is connected to the mandrel 5, the fixing sleeve 61 is fitted onto the outer periphery of the step 11. Then, the fixing post 62 is rotated so that the fixing post 62 abuts against the outer periphery of the step 11, locking the fixing sleeve 61 at the step 11. Then, the abutting post 612 is pressed against one side of the jaw of the three-jaw chuck 71. During the rotation of the three-jaw chuck 71, the abutting post 612 is pushed to rotate, thereby driving the mandrel 5 and the sealing bushing to rotate synchronously. The outer diameter of the stainless steel sleeve 1 is machined on a lathe using a cutting tool.

[0061] Working principle: First, rough machining of stainless steel sleeve 1 and graphite sleeve 2 is completed, as well as heat fitting and fixing of stainless steel sleeve 1 and graphite sleeve 2; then, the inner diameter of graphite sleeve 2 is precision machined using tooling fixture 4; finally, the outer diameter of stainless steel sleeve 1 is precision machined using mandrel 5 and floating fixture 6, so that the tolerance of the outer diameter of stainless steel sleeve 1 and the inner hole of graphite sleeve 2 is between 0.01mm and 0.03mm, and the coaxiality of the outer diameter of stainless steel sleeve 1 and the inner hole of graphite sleeve 2 does not exceed 0.01mm.

[0062] The specific embodiments described herein are merely illustrative examples. Those skilled in the art to which this application pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the scope defined in this application.

Claims

1. A process for machining a bushing, characterized in that, include: Step S1: Sleeve together a stainless steel sleeve (1) with a step (11) on one side and a graphite sleeve (2) to form a sealing bushing. The outer diameter tolerance of the stainless steel sleeve (1) is 0.03 mm. Step S2: Machining the inner hole of the graphite sleeve (2): Based on the outer diameter of the stainless steel sleeve (1), the tooling fixture (4) is fitted onto the outer circumference of the sealing bushing. The gap between the outer diameter of the stainless steel sleeve (1) and the inner diameter of the tooling fixture (4) is D1, 0.03mm < D1 ≤ 0.05mm. Then, the tooling fixture (4) fitted onto the sealing bushing is clamped on the three-jaw chuck (71) of the machine tool (7) to finish the inner diameter of the graphite sleeve (2). The coaxiality of the tooling fixture (4) and the rotating shaft of the machine tool (7) is less than or equal to 0.01mm. Step S3: Machining the outer hole of the stainless steel sleeve (1): Insert one end of the mandrel (5) after wire cutting into the inner diameter of the graphite sleeve (2). The gap between the outer diameter of the mandrel (5) and the inner diameter of the machined graphite sleeve (2) hole is D2, 0≤D2≤0.01mm. Hold both ends of the mandrel (5) with pins respectively. Connect the floating fixture (6) at the step (11) of the stainless steel sleeve (1). Use the three-jaw chuck (71) of the machine tool (7) to drive the sealing bushing to rotate through the floating fixture (6). At the same time, the outer diameter of the stainless steel sleeve (1) is precision machined. In step S2, the tooling fixture (4) includes a reference sleeve (41) and a threaded locking cylinder (42). The reference sleeve (41) includes an integrally connected sleeve portion (411) and a positioning portion (412). The sleeve portion (411) is axially fitted with the outer peripheral wall of the stainless steel sleeve (1), and one end of the sleeve portion (411) abuts against one side of the step (11) of the stainless steel sleeve (1). The positioning portion (412) abuts against the end of the stainless steel sleeve (1) away from the step (11). The threaded locking cylinder (42) is threadedly connected to the end of the reference sleeve (41) away from the positioning portion (412). The reference sleeve (41) is used to connect with the three-jaw chuck (71) of the machine tool (7). In step S3, the floating fixture (6) includes an annular fixed sleeve (61) and a plurality of fixed posts (62) evenly distributed circumferentially on the fixed sleeve (61), and an abutment post (612) connected to the fixed sleeve (61) and extending axially. The fixed sleeve (61) is provided with a threaded hole (611) corresponding to the fixed post (62). The fixed post (62) is threadedly connected to the threaded hole (611). The fixed post (62) is used to lock the fixed sleeve (61) on the stepped portion (51). The abutment post (612) is used to abut against one side of the jaw of the three-jaw chuck (71) of the machine tool (7).

2. The process for machining a bushing according to claim 1, characterized in that, In step S1, the machining process of the sealing bushing is as follows: B1: Take a section of stainless steel pipe and process it on a lathe to form a stainless steel sleeve (1) with a stepped (11) outer diameter. Leave a 0.3mm allowance for the outer diameter of the stainless steel sleeve (1). B2: Graphite sleeve (2) is formed by powder metallurgy, with a 0.5mm allowance in the inner diameter of the graphite sleeve (2); B3: Taking advantage of the different thermal shrinkage ratios of stainless steel and graphite, the graphite sleeve (2) is fitted into the stainless steel sleeve (1) through a heat fitting process. B4: Drill a fixing hole (12) radially on the outer peripheral wall of the stainless steel sleeve (1). The fixing hole (12) penetrates the stainless steel sleeve (1) and extends to the outer peripheral wall of the graphite sleeve (2). The fixing hole (12) does not penetrate the outer peripheral wall of the graphite sleeve (2). Then, hammer a pin (3) into the fixing hole (12). Laser weld the pin (3) and the fixing hole (12). Roughly process the laser weld to ensure that the stainless steel sleeve (1) is flat at the laser weld.

3. The process of claim 1 wherein, The tooling fixture (4) also includes a transition sleeve (43), which is sleeved on the outer periphery of the stainless steel sleeve (1) and located between the stainless steel sleeve (1) and the sleeve portion (411).

4. The process of claim 1 wherein, The tooling fixture (4) further includes an annular gasket (44), which abuts against the end of the sealing bushing away from the positioning part (412) and between the sealing bushing and the threaded locking cylinder (42).

5. The process of claim 1 wherein, In step S3, the mandrel (5) includes an integrally connected stepped portion (51) and a plug portion (52). The stepped portion (51) and the plug portion (52) are both coaxially arranged columnar structures, and the outer diameter of the stepped portion (51) is larger than the outer diameter of the plug portion (52). A positioning hole (511) is provided at the axial center of the end of the stepped portion (51) away from the plug portion (52), and a through hole is provided at the axial center of the plug portion (52). The insertion hole (521) of the insertion part (52) is divided into several parts by wire cutting at the axis.

6. The process of machining a bushing according to claim 5, wherein, The gap of the wire cutting of the mandrel (5) is D3, and D3 is 0.01mm.

7. The process of claim 5 wherein, In step S3, the pins at both ends of the core rod (5) are a first pin (72) and a second pin (73), respectively. The first pin (72) abuts against the positioning hole (511), and one end of the second pin (73) extends into and is inserted into the insertion hole (521).

8. The process of machining a bushing according to claim 7, wherein, In step S3, a positioning block (74) is slidably connected to the machine tool (7), and a snap-fit ​​assembly is used to fix the positioning block (74) to the machine tool (7). The positioning block (74) has some rotating holes facing the three-jaw chuck (71). The rotating holes are coaxially arranged with the three-jaw chuck (71), and a bearing is provided in the rotating holes. One end of the first ejector pin (72) is snapped with the three-jaw chuck (71), and one end of the second ejector pin (73) is rotatably connected in the rotating holes.

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