Magnetorheological polishing apparatus and method for variable-diameter, high-aspect-ratio inner holes in small tubes

Abstract

This invention discloses a magnetorheological polishing apparatus and method for inner holes of slender tubes with variable diameter and large aspect ratio, belonging to the field of ultra-precision machining technology. The apparatus includes a device body, a reciprocating motion mechanism, a clamping assembly, a multi-magnetic field generator, a magnetic field driving system, and a magnetorheological polishing fluid supply and circulation system. The method includes preparing the magnetorheological fluid, injecting it into the target workpiece hole via a delivery pump, and stirring to ensure the liquid flows without sedimentation. The multi-magnetic field generator causes the magnetorheological fluid to form a flexible polishing film within the hole. The reciprocating motion mechanism drives the target workpiece in axial reciprocating motion, and the magnetic field driving system causes the multi-magnetic field generator to rotate around its own axis, ultimately achieving approximately uniform polishing pressure on the inner wall, thus completing high-quality and high-efficiency polishing. This invention is applicable to polishing slender through holes of different sizes and variable-diameter capillaries, solving the problem of easy deformation and runout of capillaries during processing, and helping to improve polishing efficiency.

Description

Technical Field

[0001] This invention belongs to the field of ultra-precision machining technology, specifically relating to a magnetorheological polishing device and method for inner holes of small tubes with variable diameter and large aspect ratio, especially suitable for polishing through holes with variable diameter and large aspect ratio. Background Technology

[0002] The applications of thin tubing (inner diameter less than 10 mm, length-to-diameter ratio greater than 20) are becoming increasingly widespread, such as delivery pipes used in refrigeration units, sample dispensing needles—core components of high-end biochemical analyzers and chemiluminescence immunoassay analyzers, capillaries used in biological detection and analysis, and minimally invasive catheters used in the medical industry. Although different fields have different performance requirements, most desire a high degree of smoothness in the inner wall of the thin tubing, especially a sufficiently smooth transition in the inner diameter, to reduce cleaning residue and avoid cross-contamination of liquids.

[0003] Currently, high-quality internal bores of small tubes with large aspect ratios are typically achieved using abrasive flow polishing or magnetic abrasive grinding to remove burrs from the inner wall. Abrasive flow polishing, leveraging the excellent conformal and flow characteristics of fluids, can polish various complex internal cavity structures and internal channels. However, the pressure of the abrasive medium on the target workpiece surface during processing is at the MPa level, and the polishing effect is significant when passing through channels with varying cross-sections and curvatures, while the polishing effect on straight channel surfaces is poor. There is a need to develop a controllable polishing method aimed at homogenizing material removal and to address the polishing problem of thin-walled, low-rigidity structural components. Magnetic abrasive grinding utilizes the characteristics of a magnetic field to assist abrasive particles in polishing, effectively improving the efficiency of internal bore polishing and the quality of the processed surface. It has advantages such as high adaptability and no need for tool compensation. However, when using traditional magnetic abrasive grinding methods to polish the internal bores of small tubes with large aspect ratios, the amount of magnetic abrasive particles is small, making it difficult to guarantee polishing efficiency and uniform surface quality.

[0004] Currently, polishing technology for deep micro-holes with varying diameters has reached a bottleneck. How to improve processing efficiency while ensuring the quality and uniformity of the processed surface has become a key technical problem that urgently needs to be solved in this field.

[0005] In the existing technology, magnetorheological polishing technology can reduce the surface roughness of devices to below 1 nm, obtain good surface and subsurface quality, and process a wide range of materials. However, it is mostly used for polishing the outer surface of large components and micro-devices, while research on polishing the inner wall of small tubes such as variable diameter sampling needles and capillaries is still limited and not mature enough. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned technical problems to a certain extent. To this end, the present invention proposes a magnetorheological polishing device and method for small tubes with variable diameter and large length-to-diameter ratio inner holes, so as to solve the problems of easy deformation and runout of capillaries in the processing of existing technology, as well as the problem of uneven surface quality caused by the difficulty of the target workpiece to rotate during the processing.

[0007] To achieve the above objectives, the present invention provides the following solution: a magnetorheological polishing apparatus and method for variable-diameter, high-aspect-ratio inner holes in small tubes, comprising:

[0008] The device body has multiple worktables at different horizontal heights, and each worktable has a coaxial central hole in the center.

[0009] The reciprocating motion mechanism includes a guide rail vertically fixed to the device body, a slider sliding on the guide rail, and a ball screw, coupling, and servo motor that drive the slider to reciprocate.

[0010] The clamping assembly, fixedly connected to the slider, has an ER chuck coaxially arranged with the central hole, the ER chuck being used to clamp the target workpiece;

[0011] A multi-magnetic field generating device is rotatably connected between two worktables and has a magnetic field channel for accommodating the target workpiece. The magnetic field channel is coaxial with the central hole. The multi-magnetic field generating device includes a pressure plate, a connecting rod, a connecting shaft, a tapered roller bearing, a turntable, and permanent magnets. The turntables are connected by the connecting rod to form a multi-layer structure. The multi-layer structure is placed in the central hole of the two worktables through the upper and lower connecting shafts and the tapered roller bearings. Each turntable has a pair of permanent magnets fixedly attached to it. The permanent magnets are mounted on the turntable by the pressure plate and screws. The number of layers of the turntable is determined according to the length to be processed of the target workpiece, the length of the connecting rod, and the reciprocating stroke of the target workpiece. The relationship is: C = (LT) / l + 1, where C is the number of layers, L is the length to be processed of the target workpiece, T is the reciprocating stroke of the target workpiece, and l is the length of the connecting rod.

[0012] A magnetic field drive system is connected to the multiple magnetic field generators to control the rotation of the magnetic field.

[0013] The magnetorheological polishing fluid supply circulation system is connected to the target workpiece and circulates the magnetorheological fluid into the inner hole of the target workpiece.

[0014] Preferably, when the outer diameter of the target workpiece is less than 5 mm, a pair of magnetic poles are arranged on each turntable; when the outer diameter of the target workpiece is between 5 and 10 mm, two pairs of magnetic poles are arranged on each turntable, and the two pairs of magnetic poles are arranged symmetrically.

[0015] Preferably, the permanent magnet is an N35 permanent magnet as the magnetic field source.

[0016] Preferably, the magnetic field strength can be adjusted within the range of 0 to 0.45T by adjusting the installation position of the permanent magnet.

[0017] Preferably, the rotational speed range of the magnetic field driving system driving the multi-magnetic field generating device is 0 to 1000 rpm, and the radial and axial runout of the turntable in the multi-magnetic field generating device is within 0.01 mm.

[0018] The present invention discloses the following technical effects:

[0019] This invention provides a magnetorheological polishing device and method for inner holes of small tubes with variable diameter and large length-to-diameter ratio, which significantly improves the smoothness of the inner wall of deep micro-holes with variable diameter. It is suitable for polishing slender thin-walled through holes with an inner diameter of less than 10 mm and capillaries with variable diameter. It solves the problem of easy deformation and runout during processing due to the low stiffness of capillaries, and helps to improve the polishing efficiency of inner holes of capillary-like parts made of non-ferromagnetic materials. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the magnetorheological polishing device according to an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the reciprocating motion mechanism in the magnetorheological polishing apparatus according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the clamping component in the magnetorheological polishing apparatus according to an embodiment of the present invention;

[0024] Figure 4 This is a half-sectional view of the multi-magnetic field generating device in the magnetorheological polishing apparatus of this invention.

[0025] Figure 5 This is a schematic diagram illustrating the working principle of the magnetorheological polishing device according to an embodiment of the present invention.

[0026] Figure 6 This is an optimized magnetic field distribution diagram of a pair of magnetic poles in the magnetorheological polishing apparatus of this invention.

[0027] The components include: 1. Device body; 2. Reciprocating motion mechanism; 21. Ball screw; 22. Guide rail; 23. Slider; 24. Coupling; 25. Servo motor; 3. Clamping assembly; 31. Connecting piece; 32. ER chuck; 33. Rubber bushing; 34. Locking nut; 35. Plastic bushing; 36. Plastic sliding bearing; 4. Multi-magnetic field generator; 41. Permanent magnet; 42. Pressure plate; 43. Turntable; 44. Connecting rod; 45. Connecting shaft; 46. Tapered roller bearing; 47. End cap; 5. Magnetic field drive system; 51. Synchronous belt; 52. Pulley; 53. Stepper motor; 54. Motor support; 6. Magnetorheological polishing fluid supply and circulation system; 61. Delivery pump; 62. Electric stirrer; 63. Liquid container; 64. Clamp; 65. Hose clamp; 66. Hose; 7. Target workpiece. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1:

[0031] Reference Figure 1 As shown, the present invention provides a magnetorheological polishing device and method for a variable diameter, high aspect ratio inner hole of a small tube, comprising a device body 1, a reciprocating motion mechanism 2, a clamping assembly 3, a multi-magnetic field generating device 4, a magnetic field driving system 5, and a magnetorheological polishing fluid supply and circulation system 6. The device body 1 includes a three-layer horizontal worktable, which is "E"-shaped and consists of upper, middle, and lower layers. Each of the upper, middle, and lower worktables has a central hole. The device body 1 also includes a vertical body located behind the worktable, on which a reciprocating motion mechanism 2 is mounted. The clamping assembly 3 is slidably connected. A multi-magnetic field generator 4 is fixed between the upper and middle worktables. The multi-magnetic field generator 4 has a magnetic field channel inside that allows the target workpiece 7 to pass through. The magnetic field channel is coaxial with the central hole on the three-layer worktable. A magnetic field drive system 5 is located on one side of the device body 1, providing rotational driving force for the multi-magnetic field generator 4. A magnetorheological polishing slurry supply and circulation system 6 pumps polishing slurry into the target workpiece 7 and provides power for the circulation of the polishing slurry.

[0032] Specifically, such as Figure 2 As shown, the reciprocating motion mechanism 2 includes a ball screw 21, a guide rail 22, a slider 23, a coupling 24, and a servo motor 25. The ball screw 21 and the guide rail 22 are precisely and vertically mounted on the device body 1 by screws (not shown in the figure). At the same time, the height and position of the ball screw 21 and the guide rail 22 need to be accurately set to ensure that the center hole of the frustum of the connecting member 31 is coaxial with the center hole of the device body 1, and the coaxiality is not less than 0.01mm. It is also necessary to ensure that the movable stroke of the slider 23 is not less than the length of the connecting rod 44, so that the connecting member 31 will not experience motion interference. The servo motor 25 drives the ball screw 21 through the coupling 24. The slider 23 is driven by the ball screw 21 to reciprocate on the guide rail 22, thereby causing the target workpiece 7 (a thin long tube) to perform axial reciprocating motion.

[0033] Further optimization of the scheme results in the reciprocating motion mechanism 2 having a repeatability positioning accuracy of 0.1mm, a stroke of 300mm, and a reciprocating motion speed of 0-40mm / s;

[0034] Specifically, such as Figure 3 As shown, the clamping assembly 3 includes a connector 31, an ER chuck 32, a rubber bushing 33, a locking nut 34, a plastic bushing 35, and a plastic sliding bearing 36. The connector 31 is connected to the slider 23 by screws (not shown in the figure). The ER chuck 32 is placed in the connector 31 and then tightened by the locking nut 34. The plastic sliding bearing 36 and the plastic bushing 35 are connected by screws (not shown in the figure) and placed on a circular platform below the device body 1. The plastic bushing 35 is in contact with the target workpiece 7. The ER chuck 32 and the plastic bushing 35 are selected according to the outer diameter of the target workpiece 7. If the diameter of the target workpiece 7 is too small, for example, the outer diameter is less than 1 mm, an additional rubber bushing 33 is needed to cooperate with the ER chuck 32 to complete the clamping of the target workpiece 7 with a very small outer diameter.

[0035] In a further optimized scheme, the ER chuck 32 clamps the target workpiece 7. For target workpieces 7 with different diameters, the ER chuck 32 can be replaced or a rubber bushing 33 can be added to clamp and automatically center the workpiece. Thus, the reciprocating motion mechanism 2 can drive the target workpiece 7 to perform axial reciprocating linear motion.

[0036] Specifically, such as Figure 4As shown, the multi-magnetic field generating device 4 includes a permanent magnet 41, a pressure plate 42, a turntable 43, a connecting rod 44, a connecting shaft 45, a tapered roller bearing 46, and an end cover 47. The turntable 43 is connected by the connecting rod 44 to form a multi-layer structure. The number of layers C is set according to the processing length L of the target workpiece 7, rounded up. The formula for determining the number of layers C is: C = (LT) / l + 1; where T is the reciprocating stroke of the target workpiece 7, and l is the length of the connecting rod 44; the target workpiece 7 needs to leave a certain margin. Sufficient length for clamping; the permanent magnet 41 is placed on the turntable 43 via the pressure plate 42 and screws, so that each turntable 43 will generate a magnetic field, i.e., multiple magnetic fields are set on the target workpiece 7; the multi-layer structure is placed in the central hole of the worktable via the upper and lower connecting shafts 45 and the tapered roller bearing 46, and the coaxiality with the central hole must be within 0.01mm; the upper tapered roller bearing 46 contacts the end cover 47 to achieve axial fixation of the multi-layer structure.

[0037] In this embodiment, more specifically, the multi-magnetic field generating device 4 includes 3 pairs of permanent magnets 41, 6 pressure plates 42, 3 turntables 43, 6 connecting rods 44, 2 connecting shafts 45, 2 tapered roller bearings 46, and an end cap 47. The 3 turntables 43 are connected by 6 connecting rods 44 to form a three-layer structure. The 3 pairs of permanent magnets 41 are respectively placed on the 3 turntables 43 by 6 pressure plates 42 and screws (not shown in the figure), that is, generating 3 segments of magnetic field on the target workpiece 7. The three-layer structure is placed in the central hole of the device body 1 by the upper and lower 2 connecting shafts 45 and 2 tapered roller bearings 46. The upper tapered roller bearing 46 is in contact with the end cap 47 to achieve axial fixation of the three-layer structure.

[0038] In a further optimized design, the permanent magnets 41 are symmetrically mounted on the turntable 43 with a pair of magnetic poles N-S or S-N. The pair of magnetic poles arranged in a radial section have a significant magnetic field gradient, allowing the polishing film to rotate or flow smoothly. In addition, the symmetrically mounted pair of magnetic poles acts as an auxiliary support, achieving lateral force balance for the target workpiece 7 and ensuring uniform distribution of the local magnetic field in the axial section of the inner hole. Through process experiments, it has been found that the arrangement of a pair of magnetic poles has a significant magnetic field gradient in the radial section, which can prevent the flexible polishing film from being unable to rotate or flow due to complete solidification. When the outer diameter of the target workpiece 7 is less than 5mm, each layer of the turntable 43 preferably has only one pair of magnetic poles to ensure the polishing quality of the inner wall. When the outer diameter of the target workpiece 7 is between 5 and 10mm, in order to further improve polishing efficiency without affecting the polishing quality, each layer of the turntable 43 can be arranged with two pairs of magnetic poles. Each symmetrically mounted pair of magnetic poles acts as an auxiliary support, achieving lateral force balance for the target workpiece 7 and uniform distribution of the local magnetic field in the axial section of the inner hole.

[0039] To further optimize the design, each pair of magnetic poles on the turntable 43 needs to be arranged in a continuous 45-degree rotation pattern, which is beneficial to realize the continuous helical motion of the abrasive particles in the magnetorheological fluid, thereby improving polishing efficiency and quality. The permanent magnet 41 can slide and be fixed on the groove of the turntable 43 to adjust the magnetic field strength on the inner wall of the target workpiece 7, so that the magnetorheological fluid can rotate smoothly under the action of magnetic force and generate sufficient and uniform polishing pressure. The adjustable range of the magnetic field strength is 0 to 0.45T.

[0040] To further optimize the solution, for the inner hole at the diameter change point of the target workpiece 7, the magnetic field strength at the diameter change point of the target workpiece 7 is adjusted by replacing the connecting rod 44 with one of different lengths and adjusting the position of the permanent magnet 41. This achieves a gradient change in the magnetic field in the vertical direction and ensures that the polishing pressure of the inner wall at the diameter change point is the same as before the diameter change under the influence of fluid pressure, thereby achieving uniform polishing and smooth transition of the inner wall of the diameter change inner hole.

[0041] In a further optimized design, the permanent magnet 41 is an N35 permanent magnet 41 as the magnetic field source. In this embodiment, all other components besides the permanent magnet 41 are made of non-ferromagnetic materials, such as aluminum alloys and engineering plastics. If the structure is magnetic, it should be demagnetized or magnetically shielded.

[0042] Specifically, such as Figure 5 As shown, the magnetic field drive system 5 includes a synchronous belt 51, two pulleys 52, a stepper motor 53, a motor support 54, and a controller (not shown in the figure). The reduction ratio is 2:1 to increase the torque of the connecting shaft 45. The two pulleys 52 are respectively connected to the connecting shaft 45 of the multi-magnetic field generator 4 and the stepper motor 53. The synchronous belt 51 is connected to the two pulleys 52, and the installation height and position of the stepper motor 53 are adjusted to ensure that the installation height of the two pulleys 52 is the same and that the synchronous belt 51 is tensioned. The controller can simultaneously control the operation of the servo motor 25 and the stepper motor 53.

[0043] Further optimization of the scheme: the speed range of the stepper motor 53 is 0 to 2000 rpm, and the speed range of the multi-magnetic field generator 4 is 0 to 1000 rpm. It is also required that the radial and axial runout of the turntable 43 in the multi-magnetic field generator 4 is within 0.01 mm.

[0044] In a further optimized scheme, the controller controls the operation of the multi-magnetic field generating device 4 and the reciprocating motion mechanism 2. That is, the controller can simultaneously control the reciprocating axial motion of the target workpiece 7 and the rotational motion of the magnetic field, i.e., the moving speed, stroke and rotation speed, thereby expanding the magnetic field action area, increasing the polishing length of the target workpiece 7, improving the uniformity of the inner wall processing surface quality, and realizing the helical motion of the abrasive grains.

[0045] Specifically, such as Figure 5 As shown, the magnetorheological polishing fluid supply and circulation system 6 includes a delivery pump 61, an electric stirrer 62, a liquid container 63, a clamp 64, a hose clamp 65, and a hose 66. Magnetorheological fluid circulates within the hose 66. The hose 66 is first connected from the delivery pump 61 to the target workpiece 7, then from the target workpiece 7 to the liquid container 63, and finally from the liquid container 63 back to the delivery pump 61, forming a magnetorheological fluid circulation loop. The clamp 64 clamps the hose 66 and the target workpiece 7 tightly. The hose clamp 65 secures the hose 66. The electric stirrer 62 is fixed to the liquid container 63, allowing control of its stirring speed and ensuring that the magnetorheological fluid does not easily precipitate.

[0046] With further optimization, the delivery pump 61 can provide a hydraulic pressure range of 0–4 MPa and a flow rate range of 0–18 L / min.

[0047] In a further optimized scheme, the magnetorheological fluid is input into the target workpiece 7 by the delivery pump 61. The resulting fluid flow, combined with the reciprocating axial motion of the target workpiece 7 and the rotational motion of the multi-magnetic field generating device 4, constitutes the composite motion of the abrasive particles, that is, the continuous spiral motion of the abrasive particles is realized, thereby completing the all-round polishing of the inner wall of the target workpiece 7 to be processed.

[0048] Example 2:

[0049] Embodiment 2 of the present invention provides a magnetorheological polishing method for the inner hole of a small tube with variable diameter and large length-to-diameter ratio. The method uses the magnetorheological polishing device for the inner hole of a small tube with variable diameter and large length-to-diameter ratio described in Embodiment 1 above. Taking a stainless steel tube as the target workpiece 7 as an example, the length of the stainless steel tube is 30cm, the inner diameter before diameter change is 1mm, and the inner diameter after diameter change is 0.7mm. The specific operation steps are as follows:

[0050] Step S1: Prepare the magnetorheological fluid. Following the principle of preparing and using immediately, prepare the magnetorheological fluid according to the group. Pour the prepared magnetorheological fluid into the liquid container 63 and start stirring. Under the continuous stirring of the electric stirrer 62, ensure that the magnetorheological fluid does not settle, so that it has the best polishing effect.

[0051] In some embodiments, the magnetorheological fluid is prepared by comprising 36% by volume hydroxyl iron powder, 6% by volume silicon carbide abrasive or diamond abrasive, 57% by volume aqueous liquid, and the balance being a stabilizer.

[0052] Step S2, Install the target workpiece 7: First, pass one end of the target workpiece 7 through the ER chuck 32 or the rubber bushing 33, and tighten the locking nut 34 so that the ER chuck 32 clamps the target workpiece 7. At the same time, the other end of the target workpiece 7 can pass through the plastic bushing 35. Then the reciprocating motion mechanism 2 can drive the target workpiece 7 to perform axial reciprocating linear motion.

[0053] Step S3: Set up the liquid circuit: First, connect the rubber hose 66 from the delivery pump 61 to the upper end of the target workpiece 7, then connect it from the lower end of the target workpiece 7 to the liquid container 63, and finally connect it from the liquid container 63 to the delivery pump 61. At the same time, use the clamp 64 to clamp the hose 66 and the target workpiece 7, use the hose clamp 65 to fix the hose 66, and leave a certain length of hose 66 to avoid interference during the movement of the target workpiece 7. Then start the delivery pump 61 and set the flow rate according to the size of the target workpiece 7.

[0054] Step S4: Setting up and adjusting the magnetic field strength: After the target workpiece 7 is filled with magnetorheological fluid, the permanent magnets 41 are symmetrically installed on the turntable 43 with a pair of magnetic poles NS using the pressure plate 42 and screws; the pair of permanent magnets 41 in each layer are arranged at a continuous rotation of 45 degrees, which helps to realize the continuous spiral movement of abrasive particles in the magnetorheological fluid and improve polishing efficiency and quality; in addition, the position of the permanent magnets 41 on the groove of the turntable 43 is adjusted to change the magnetic field strength on the inner wall of the target workpiece 7, thereby changing the viscosity of the magnetorheological fluid, ensuring that the viscosity is not too high and will not affect the smooth movement of the flexible polishing film; in addition, for the pipe wall after the diameter change, the position of the permanent magnets 41 in the corresponding layer is adjusted so that the magnetic field in the vertical direction of the target workpiece 7 has a gradient change, so as to achieve uniform polishing of the inner wall of the inner hole of the diameter change.

[0055] Step S5: Polishing: Start the controller in the magnetic field drive system 5, and simultaneously make the target workpiece 7 perform axial reciprocating motion and magnetic field rotation, increase the processing length of the target workpiece 7 and realize the helical motion of the abrasive particles in the magnetorheological fluid. Then, use the controller to adjust the reciprocating stroke, reciprocating speed, rotation speed and running time to effectively control the polishing quality of the inner wall.

[0056] Step S6: Clean the inner hole of the target workpiece 7: First, remove the permanent magnet 41, then replace the liquid in the liquid container 63. The replacement liquid can be deionized water or alcohol. Use the delivery pump 61 to input deionized water or alcohol to thoroughly clean the polished inner hole. Repeat the above operation step S6 until it is clean.

[0057] In this embodiment, the magnetorheological polishing method is suitable for polishing thin-walled variable-diameter inner holes with an inner diameter of less than 10 mm and a length of more than 10 mm.

[0058] In some embodiments, the polishing apparatus described above can be easily modified into a horizontal structure, and its operation becomes: the target workpiece 7 is stationary, while the multi-magnetic field generator 4 rotates and reciprocates simultaneously. In this configuration, the polishing length of the inner wall of the target workpiece 7 can be further increased.

[0059] Compared with the prior art, the embodiments of the present invention disclose the following beneficial effects:

[0060] 1. In this invention, a self-prepared magnetorheological fluid and a multi-magnetic field generating device 4 are used to enable the magnetorheological fluid to rotate and flow smoothly in a thin tube; the multi-magnetic field generating device 4 changes the magnetic field strength on the inner wall of the target workpiece 7, which can not only generate a nearly uniformly distributed magnetic field, but also realize the gradient change of the magnetic field in the vertical direction, thus making it suitable for polishing slender thin-walled through holes with an inner diameter of less than 10 mm and variable diameter capillaries.

[0061] 2. In this invention, each pair of magnetic poles of the multi-magnetic field generating device 4 is equivalent to an auxiliary support, which is conducive to achieving lateral force balance of the target workpiece 7 and solves the problem that the capillary itself is prone to deformation and jumping during processing due to its low stiffness.

[0062] 3. This invention is applicable to the polishing of the inner hole of capillary-like parts made of non-ferromagnetic materials. The multi-magnetic field design can improve polishing efficiency while obtaining uniform and better surface quality. The vertical structure can avoid the uneven surface quality caused by the horizontal structure, which is difficult for the target workpiece 7 of the cyclically input magnetorheological fluid to rotate.

[0063] 4. The present invention has a novel structural design, is easy to operate and modify. For example, it can be transformed into a horizontal structure through simple modification. Its working mode is changed to the target workpiece 7 being stationary while the multi-magnetic field generating device 4 rotates and reciprocates. In this form, the polishing length of the inner wall of the target workpiece 7 can be further increased.

[0064] All aspects not detailed in this invention are conventional technical means known to those skilled in the art.

[0065] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0066] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A magnetorheological polishing apparatus for variable-diameter, high aspect ratio inner holes in small tubes, characterized in that, include: The device body (1) has multiple worktables at different horizontal heights, and each worktable has a coaxial central hole in the center. The reciprocating motion mechanism (2) includes a guide rail (22) vertically fixed on the device body (1), a slider (23) sliding on the guide rail (22), and a ball screw (21), a coupling (24) and a servo motor (25) that drive the slider (23) to reciprocate. The clamping assembly (3) is fixed to the slider (23) and has an ER chuck (32) coaxially arranged with the central hole. The ER chuck (32) is used to clamp the target workpiece (7). A multi-magnetic field generating device (4) is rotatably connected between the two workbenches and has a magnetic field channel for accommodating the target workpiece (7) to pass through. The magnetic field channel is coaxial with the central hole. The multi-magnetic field generating device (4) includes a pressure plate (42), a connecting rod (44), a connecting shaft (45), a tapered roller bearing (46), a turntable (43), and a permanent magnet (41). The turntable (43) is connected by the connecting rod (44) to form a multi-layer structure. The multi-layer structure is placed between the two workbenches through the upper and lower connecting shafts (45) and the tapered roller bearing (46). In the central hole of the platform, a pair of permanent magnets (41) are fixed on each of the turntables (43). The permanent magnets (41) are mounted on the turntables (43) by the pressure plate (42) and screws. The number of layers of the turntables (43) is determined according to the processing length of the target workpiece (7), the length of the connecting rod (44) and the reciprocating stroke of the target workpiece (7). The relationship is: C=(LT) / l+1, where C is the number of layers, L is the processing length of the target workpiece (7), T is the reciprocating stroke of the target workpiece (7) and l is the length of the connecting rod (44). The magnetic field drive system (5) is connected to the multi-magnetic field generator (4) to control the rotation of the magnetic field; The magnetorheological polishing fluid supply circulation system (6) is connected to the target workpiece (7) and circulates the magnetorheological fluid into the inner hole of the target workpiece (7).

2. The magnetorheological polishing apparatus for variable-diameter, high-aspect-ratio inner holes of small tubes according to claim 1, characterized in that, When the outer diameter of the target workpiece (7) is less than 5 mm, a pair of magnetic poles are arranged on each of the turntables (43); when the outer diameter of the target workpiece (7) is between 5 and 10 mm, two pairs of magnetic poles are arranged on each of the turntables (43), and the two pairs of magnetic poles are arranged symmetrically.

3. The magnetorheological polishing apparatus for variable-diameter, high-aspect-ratio inner holes of small tubes according to claim 1 or 2, characterized in that, The permanent magnet (41) is selected from N35 permanent magnets (41) as the magnetic field source.

4. The magnetorheological polishing apparatus for variable-diameter, high-aspect-ratio inner holes of small tubes according to claim 1, characterized in that, By adjusting the installation position of the permanent magnet (41), the magnetic field strength can be adjusted within the range of 0 to 0.45T.

5. The magnetorheological polishing apparatus for variable-diameter, high-aspect-ratio inner holes of small tubes according to claim 1, characterized in that, The rotational speed range of the magnetic field drive system (5) driving the multi-magnetic field generator (4) is 0 to 1000 rpm, and the radial and axial circular runout of the turntable (43) in the multi-magnetic field generator (4) is within 0.01 mm.

6. A magnetorheological polishing method for variable-diameter, high-aspect-ratio inner holes in small tubes, characterized in that, The magnetorheological polishing apparatus for variable-diameter, high-aspect-ratio inner holes of small tubes according to any one of claims 1 to 5, wherein the magnetorheological polishing method comprises the following steps: Step S1: Prepare magnetorheological fluid; Step S2: Install the target workpiece (7); Step S3: Set up the liquid circuit; Step S4: Set up the magnetic field and adjust its strength; Step S5: Polishing; Step S6: Clean the inner hole of the target workpiece (7).

7. The magnetorheological polishing method for variable-diameter, high-aspect-ratio inner holes of small tubes according to claim 6, characterized in that, In step S1, the magnetorheological fluid is prepared by comprising 36% by volume of hydroxyl iron powder, 6% by volume of silicon carbide abrasive or diamond abrasive, 57% by volume of aqueous liquid, and the balance being a stabilizer.

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