High-speed grinding method and special tooling for super-long thin-walled silicon carbide pipe

Abstract

The application provides a high-speed grinding processing method and special tooling for an ultra-long silicon carbide thin-wall pipe fitting, and the method comprises the following steps: adopting equipment modification, blank pretreatment, special tooling clamping, grading grinding, wall thickness correction and inner hole finishing processing, and adding a high-speed spindle on a common turning and milling combined machine tool, first pretreating the blank ovality defect to find the circle, eliminating the original shape error of the blank from the source, then stably clamping and positioning through the special tooling, cooperating with rough grinding, wall thickness balancing adjustment, fine grinding and inner hole step-by-step processing, effectively solving the problems of easy eccentricity, uneven wall thickness and poor forming precision in the processing of the ultra-long thin-wall pipe fitting, and the whole process is closely connected and has high processing stability, so that the overall processing precision and the finished product qualification rate of the ultra-long silicon carbide thin-wall pipe fitting can be greatly improved under the premise of guaranteeing the structural integrity of the pipe fitting and avoiding deformation damage, and the method is suitable for large-scale precision machining production.

Description

Technical Field

[0001] This invention belongs to the field of precision machining technology of silicon carbide ceramics, specifically relating to a high-speed grinding method and special tooling for ultra-long silicon carbide thin-walled tubes. It is suitable for large-scale precision grinding production of ultra-long silicon carbide thin-walled tubes with a length ≥1000mm and a wall thickness ≤3mm, and can be applied to processing scenarios of aerospace, nuclear energy, and semiconductor high-temperature medium transport components. Background Technology

[0002] Silicon carbide (SiC) ceramics possess properties such as high hardness, high wear resistance, high temperature resistance, and excellent chemical inertness, making them the preferred material for core components of high-end equipment. Ultra-long thin-walled silicon carbide pipes are commonly used as pipelines for transporting high-temperature, high-pressure, and corrosive media, or as structural supports. After molding, these components require precision grinding to eliminate molding errors and ensure dimensional accuracy, roundness, and wall thickness uniformity. However, existing processing technologies have several shortcomings: Silicon carbide has a hardness close to that of diamond. Conventional turning tools wear out quickly, resulting in low processing efficiency and easy generation of surface micro-cracks and edge chipping defects. Existing isostatic pressing and segmented bonding processes for pipes are only means of preparing blanks and cannot achieve precision grinding of finished products.

[0003] Traditional three-jaw chucks and expansion sleeve clamping structures are prone to radial extrusion deformation when clamping thin-walled pipes. Stress release after machining causes dimensional deviations. Existing ceramic grinding fixtures are only suitable for conventional short pipes. For ultra-long pipes with a length of more than 1000mm, there is no effective support in the middle section, and the problems of machining vibration, eccentricity, and uneven wall thickness cannot be completely solved.

[0004] Conventional machine tools lack spindle systems suitable for high-speed grinding of hard and brittle materials. Low-speed grinding is prone to workpiece surface burns and coarse machining marks. The machining datum is fixed, and it is impossible to dynamically correct the center according to the wall thickness deviation of the pipe fitting, resulting in poor wall thickness consistency of finished products and low machining qualification rate.

[0005] In summary, existing processing technologies and tooling cannot meet the requirements for high-precision, low-deformation, and large-scale processing of ultra-long silicon carbide thin-walled tubes. A complete set of processing technologies and specialized clamping tooling is urgently needed to solve the above-mentioned problems. Summary of the Invention

[0006] The present invention aims to solve the problems mentioned in the background art by providing a high-speed grinding method for ultra-long silicon carbide thin-walled tubes.

[0007] The specific technical solution is as follows: A high-speed grinding method for ultra-long silicon carbide thin-walled tubes includes the following steps: S1. Equipment Modification: Install a high-speed spindle on a milling and turning machine tool; S2. Blank Inspection and Pre-treatment: Inspect the ovality of the pipe fitting blank. If the ovality exceeds the standard threshold, perform rough machining to find the roundness of the blank. S3. Clamping: Use special tooling to position and fix the pipe fittings; S4. Rough grinding: Use a diamond grinding wheel to perform rough grinding on the outer circle of the pipe fitting; S5. Wall thickness equalization adjustment: When the outer diameter of the pipe is ground to the reserved machining allowance, measure the wall thickness of each section of the pipe and adjust the relative position of the grinding wheel and the pipe according to the wall thickness distribution. S6. Precision grinding: The outer diameter of the pipe fitting is precision ground to the specified dimensions of the finished product; S7. Internal bore machining: Perform precision machining on the internal bore of the pipe fitting.

[0008] In the above-mentioned high-speed grinding method for ultra-long silicon carbide thin-walled tubes, in the S5 wall thickness equalization adjustment process, the tube is centered and corrected by adjusting the relative position of the machine tool spindle and the tooling.

[0009] The above-mentioned high-speed grinding method for ultra-long silicon carbide thin-walled tubes, wherein the spindle speed range of the S4 rough grinding process is 3000-4000 rpm, and the depth of cut per pass is 0.1-0.3 mm.

[0010] In the above-mentioned high-speed grinding method for ultra-long silicon carbide thin-walled tubes, the spindle speed range of the S6 fine grinding process is 4000 to 6000 rpm.

[0011] The present invention also provides a special tooling for implementing the above-described method S3 process, comprising a base and an outer cylindrical support assembly; the base is mounted on a milling and turning machine tool, the outer cylindrical support assembly is sleeved on the outer peripheral wall of the pipe, the outer cylindrical support assembly rolls in contact with the outer wall of the pipe to provide radial support to the pipe; the top surface of the base is provided with a connecting support for connecting the outer cylindrical support assembly.

[0012] The aforementioned special tooling includes an outer circular support assembly comprising semi-circular brackets disposed on both sides of the pipe; the opposing ends of the two sets of semi-circular brackets are respectively fixed to connecting plates, and the two sets of connecting plates on the same side are locked together by fastening bolts.

[0013] The aforementioned special tooling includes a connecting support comprising multiple sets of threaded tubes; the multiple sets of threaded tubes are threadedly connected to the top surface of the base and arranged around the outer periphery of the tubes, and a corresponding side semi-circular bracket is inserted upward at the top of each set of threaded tubes, and a nut for pressing the semi-circular bracket is threadedly connected to it.

[0014] The present invention also provides a special tooling for implementing the above-described method S4 process, comprising a base; the base is mounted on a milling and turning machine tool, and a groove is provided on the top surface of the base for positioning the lower end of the pipe fitting; an end cap plate is mounted on the upper end of the pipe fitting via a connector on the top surface of the base.

[0015] The aforementioned special tooling includes a connector comprising multiple sets of annularly arranged threaded rods; the multiple sets of threaded rods are threadedly connected to the top surface of the base and placed inside the pipe, with an end-sealing plate passing through the top of each set of threaded rods, and threadedly connected to a nut for pressing the end-sealing plate.

[0016] The present invention also provides a special tooling for implementing the above-described method S7 process, comprising a base and a positioning sleeve; the base is mounted on a milling and turning machine tool, the positioning sleeve is fitted onto the outer periphery of the pipe fitting, and the bottom of the positioning sleeve is fixedly connected to the top surface of the base; multiple sets of positioning bolts are threaded onto the outer periphery of the positioning sleeve, and the multiple sets of positioning bolts are arranged in a ring at equal intervals from top to bottom along the axial direction of the positioning sleeve, with the end of each set of positioning bolts threaded through the positioning sleeve and abutting against the outer wall of the pipe fitting; a reinforcing frame is fixedly fitted onto the outer periphery of the positioning sleeve.

[0017] The present invention has the following beneficial effects: 1. This invention employs a complete set of processing techniques, including equipment modification, blank pretreatment, specialized tooling clamping, graded grinding, wall thickness correction, and internal hole finishing. By adding a high-speed spindle to a conventional milling and turning machine tool, it overcomes the limitations of conventional machine tool grinding conditions and adapts to the high-speed grinding requirements of hard and brittle silicon carbide materials. First, the ellipticity defect of the blank is pretreated to find the roundness, eliminating the original shape error of the blank from the source. Then, the blank is stably clamped and positioned using specialized tooling. Combined with rough grinding, wall thickness equalization adjustment, fine grinding, and step-by-step internal hole machining, this invention effectively solves the problems of easy eccentricity, uneven wall thickness, and poor forming accuracy in the processing of ultra-long thin-walled tubes. Furthermore, the entire process is tightly connected and has strong processing stability. It can significantly improve the overall processing accuracy and finished product qualification rate of ultra-long silicon carbide thin-walled tubes while ensuring the structural integrity of the tubes and avoiding deformation damage, making it suitable for large-scale precision machining production.

[0018] 2. This invention achieves center-based correction of pipe fittings by adjusting the relative position of the machine tool spindle and the tooling, abandoning the traditional grinding method with a fixed machining center. Furthermore, addressing the issues of center offset and uneven wall thickness distribution that easily occur after clamping ultra-long thin-walled pipe fittings, it can flexibly correct the machining datum according to the actual wall thickness deviation of the pipe fitting, accurately compensating for center offset defects caused by clamping deviations, equipment assembly errors, and workpiece deformation. It can effectively improve the problems of excessively thin wall thickness on one side of the pipe fitting and local wall thickness exceeding tolerance, making the wall thickness distribution of each section of the pipe fitting more uniform and stable, significantly improving the overall shape and position accuracy of the pipe fitting, and ensuring the consistency of the datum for subsequent fine grinding and inner hole machining.

[0019] 3. This invention employs a higher rotational speed for precision grinding. Compared to rough grinding, high-speed precision grinding effectively reduces grinding marks and surface roughness, refines the machining texture on the outer surface of the pipe fitting, eliminates minor tool marks and machining defects left over from rough grinding, and ensures more stable contact between the grinding wheel and the workpiece and more uniform grinding force under high-speed grinding conditions. This allows for precise correction of minor dimensional deviations and shape errors in the pipe fitting, stably machining the outer diameter of the pipe fitting to the standard dimensions of the finished product. At the same time, it avoids problems such as surface burns and coarse machining marks that are prone to occur in low-speed grinding, significantly improving the surface quality and dimensional accuracy of the outer diameter of the pipe fitting, and ensuring the appearance and performance of the finished pipe fitting. Attached Figure Description

[0020] Figure 1 A schematic diagram of the high-speed grinding method for ultra-long silicon carbide thin-walled tubes provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the special tooling used in step 3 of the high-speed grinding method for ultra-long silicon carbide thin-walled tubes provided in this embodiment of the invention. Figure 3 This is a schematic diagram of the special tooling used in step 4 of the high-speed grinding method for ultra-long silicon carbide thin-walled tubes provided in this embodiment of the invention. Figure 4 This is a schematic diagram of the special tooling used in step 7 of the high-speed grinding method for ultra-long silicon carbide thin-walled tubes provided in this embodiment of the invention.

[0021] In the attached image: 100. Base; 101. Threaded pipe; 102. Semi-circular bracket; 103. Nut; 104. Connecting plate; 105. Fastening bolt; 200. End cap; 201. Threaded rod; 202. Nut; 300. Reinforcing frame; 301. Positioning bolt; 302. Positioning sleeve. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0024] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0025] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Please see Figure 1-4 This embodiment provides a high-speed grinding method for ultra-long silicon carbide thin-walled tubes, including the following steps: S1. Equipment Modification: Install a high-speed spindle on the milling and turning composite machine tool; S2. Blank Inspection and Pre-treatment: Inspect the ovality of the pipe blank. If the ovality exceeds the standard, perform rough machining to find the roundness. S3. Clamping: Use special tooling to fix the pipe fittings; S4. Rough grinding: Use a diamond grinding wheel to rough grind the outer circle; S5. Wall thickness uniformity adjustment: When the outer circle is machined to a certain allowance from the finished size, measure the wall thickness of each section of the pipe fitting, and adjust the relative position of the grinding wheel and the pipe fitting according to the wall thickness distribution. S6. Precision grinding: The outer diameter of the pipe fitting is precision ground to the finished size; S7. Internal Hole Machining: The internal hole of the pipe fitting is machined using a complete set of processes including equipment modification, blank pretreatment, special tooling clamping, staged grinding, wall thickness correction, and internal hole finishing. By adding a high-speed spindle to a conventional milling and turning machine, the limitations of conventional machine tool grinding conditions are overcome, making it suitable for the high-speed grinding requirements of hard and brittle silicon carbide materials. First, the ellipticity defects of the blank are pretreated to find the roundness, eliminating the original shape error of the blank from the source. Then, the blank is stably clamped and positioned using special tooling. Combined with rough grinding, wall thickness equalization adjustment, fine grinding, and step-by-step internal hole machining, the problems of easy eccentricity, uneven wall thickness, and poor forming accuracy in the machining of ultra-long thin-walled pipe fittings are effectively solved. The entire process is closely connected and has strong processing stability. It can significantly improve the overall machining accuracy and finished product qualification rate of ultra-long silicon carbide thin-walled pipe fittings while ensuring the structural integrity of the pipe fitting and avoiding deformation damage, making it suitable for large-scale precision machining production.

[0027] In step five, the wall thickness equalization adjustment is achieved by adjusting the relative position of the machine tool spindle and the tooling to achieve center correction. This method eliminates the need for traditional grinding methods using a fixed machining center. Furthermore, it addresses the issues of center offset and uneven wall thickness distribution that often occur after clamping ultra-long thin-walled pipes. It allows for flexible correction of the machining datum based on the actual wall thickness deviation of the pipe, accurately compensating for center offset defects caused by clamping deviations, equipment assembly errors, and workpiece deformation. This effectively improves the problems of excessively thin wall thickness on one side of the pipe and local wall thickness deviations, resulting in a more uniform and stable wall thickness distribution across all sections of the pipe. This significantly improves the overall shape and position accuracy of the pipe and ensures the consistency of the datum for subsequent fine grinding and internal hole machining.

[0028] In step 4, the rough grinding speed is 3000 to 4000 rpm, and the depth of cut is 0.1 to 0.3 mm. Diamond grinding wheels are used for rough grinding of the outer diameter. Combined with matching rough grinding operating parameters, the remaining material is removed. Diamond grinding wheels have high hardness and good wear resistance, and are suitable for the grinding characteristics of hard and brittle silicon carbide materials. They can stably remove most of the machining allowance on the outer diameter of the pipe, efficiently correct the surface unevenness and shape error of the blank, and at the same time, reasonable rough grinding conditions can take into account both processing efficiency and workpiece stability, avoiding pipe vibration, edge chipping, and micro-cracks caused by excessive cutting impact during rough grinding. At the same time, uniform and controllable machining allowance is reserved for subsequent wall thickness adjustment and fine grinding processes, laying a good foundation for high-precision finishing.

[0029] In step 6, the precision grinding speed is 4000 to 6000 rpm. By using a higher speed for precision grinding, compared with rough grinding, high-speed precision grinding can effectively reduce grinding marks and surface roughness, refine the machining texture on the outer surface of the pipe fitting, eliminate the fine tool marks and machining defects left by rough grinding, and the contact between the grinding wheel and the workpiece is more stable and the grinding force is more uniform under high-speed grinding. It can accurately correct the minor dimensional deviations and shape errors of the pipe fitting, stably process the outer circle of the pipe fitting to the standard size of the finished product, and avoid the problems of surface burns and coarse machining marks that are easy to occur in low-speed grinding. It can significantly improve the surface quality and dimensional accuracy of the outer circle of the pipe fitting, and ensure the appearance and performance of the finished pipe fitting.

[0030] The special tooling used to implement step 3 of the method includes a base 100 and an outer cylindrical support assembly. The base 100 is mounted on a milling and turning machine tool. The outer cylindrical support assembly is sleeved on the outer circumferential surface of the pipe and rolls in contact with the outer wall of the pipe to provide radial support for the pipe. The top of the base 100 is provided with a connecting support for connecting the outer cylindrical support assembly. By sleeved on the outer circumference of the pipe and rolling in contact with the outer wall of the pipe, the pipe is provided with full circumferential flexible radial support, replacing the traditional single-point, rigid clamping method. This can effectively support the suspended parts of ultra-long pipes, greatly improve the overall clamping rigidity of the pipe, suppress the radial vibration and bending deformation of the pipe during grinding, and completely solve the clamping problem of ultra-long thin-walled pipes with large span, poor rigidity, and easy shaking. It is suitable for use in the entire grinding process of rough grinding and fine grinding of pipes.

[0031] The outer circular support assembly includes semi-circular brackets 102 disposed on both sides of the pipe fitting. A connecting plate 104 is fixedly connected to one end of each of the two sets of semi-circular brackets 102. The two sets of connecting plates 104 on the same side are connected together by fastening bolts 105. The outer circular support assembly adopts a splicing structure of semi-circular brackets 102 on both sides, connecting plates 104, and fastening bolts 105. The structure is simple and easy to assemble and disassemble. It can be flexibly adapted to different outer diameter silicon carbide thin-walled pipe fittings, and has strong versatility. Furthermore, the two sets of semi-circular brackets 102 are symmetrically arranged, which can form a symmetrical and uniform support force on both sides of the pipe fitting, avoiding pipe fitting eccentricity and deformation caused by uneven force on one side. The bolt-locking connection method can ensure that the bracket assembly is stable and will not loosen or shift during processing, maintaining a stable circumferential support state and effectively ensuring the positional accuracy and structural stability of the pipe fitting during processing.

[0032] The connecting support includes multiple sets of threaded tubes 101 threaded to the top of the base 100 and located on the outer circumference of the pipe fitting. The top of each set of threaded tubes 101 passes through the corresponding side semi-circular bracket 102 and is threadedly connected to a nut 103 for pressing the semi-circular bracket 102. By adopting a threaded locking structure of multiple sets of threaded tubes 101 and nuts 103, the threaded tubes 101 are arranged vertically between the base 100 and the semi-circular bracket 102, which can realize flexible adjustment of the bracket support height and support force. It can adapt to the clamping requirements of ultra-long thin-walled pipe fittings with different lengths and outer diameters, and has a wider adaptability. In addition, the multi-point annular arrangement of the threaded support structure can evenly distribute the support load and avoid local stress concentration and squeezing damage to the outer wall of the thin-walled pipe fitting. At the same time, the threaded locking structure is firmly assembled and accurately positioned, which can maintain the stability of the tooling structure for a long time, effectively resist grinding cutting force and vibration interference, and continuously ensure the clamping accuracy of the pipe fitting.

[0033] The special tooling used to implement step 4 includes a base 100 mounted on a milling and turning machine. The top of the base 100 has a groove for inserting the pipe fitting. The top of the base 100 is connected to an end sealing plate 200 located on the upper end of the pipe fitting via a connector. The insertion groove on the top of the base 100 enables quick alignment and insertion of the pipe fitting end, quickly restricts the radial displacement of the bottom of the pipe fitting, simplifies the clamping process, and improves clamping efficiency. At the same time, the top and the end sealing plate 200 form a closed clamping structure, which can provide overall limiting constraint on the upper end of the pipe fitting, effectively improving the overall structural rigidity of the pipe fitting. In addition, considering the large allowance and strong cutting impact of rough grinding, this tooling can effectively resist processing vibration, prevent the overall shaking and displacement of the pipe fitting, ensure the stability of the rough grinding process from the clamping level, and reduce rough grinding deformation error.

[0034] The connector includes multiple sets of threaded rods 201 arranged in a ring, which are threaded to the top of the base 100 and located inside the pipe. The top of each set of threaded rods 201 passes through the end cap 200 and is threaded to a nut 202 that presses against the end cap 200. By using a ring-shaped clamping structure of threaded rods 201 and nuts 202 inside the pipe, unlike the traditional external clamping method, multi-point uniform clamping and fixing is achieved from inside the pipe. This will not cause squeezing or impact damage to the outer wall of the thin-walled pipe, and will protect the unprocessed outer wall structure of the pipe. At the same time, the ring-shaped multi-point clamping structure is uniformly stressed, which can avoid problems such as local deformation of the pipe and warping of the end. It can stably constrain the axial and radial displacement of the pipe, further improve the clamping reliability under rough grinding conditions, and effectively reduce the deformation error and position deviation of rough grinding.

[0035] The special tooling used to implement step 7 includes a base 100 installed on a milling and turning machine tool and a positioning sleeve 302 sleeved on the outer circumferential surface of the pipe. The bottom of the positioning sleeve 302 is fixedly connected to the top of the base 100. The outer circumferential surface of the positioning sleeve 302 is threaded with multiple sets of positioning bolts 301 arranged equidistantly from top to bottom and in a ring. The end thread of each set of positioning bolts 301 passes through the positioning sleeve 302 and abuts against the pipe. The outer circumferential surface of the positioning sleeve 302 is fixedly fitted with a reinforcing frame 300. Through the structure of the positioning sleeve 302 and the multi-point positioning bolts 301, the outer circumference of the pipe can be uniformly tightened and positioned at multiple points in a ring, accurately correcting the machining center of the pipe and ensuring the coaxiality of the pipe and the machine tool spindle. This fundamentally solves the problems of eccentricity and out-of-tolerance roundness in the machining of the inner hole. Furthermore, the reinforcing frame 300 on the outer side of the positioning sleeve 302 significantly improves the overall structural strength and rigidity of the positioning sleeve 302, avoiding deformation of the tooling itself and positioning failure during the machining process. At the same time, the positioning bolts 301, which are evenly arranged from top to bottom, can achieve uniform multi-point positioning along the entire length of the pipe, adapting to the precision machining requirements of the inner hole of ultra-long pipes, effectively offsetting cutting vibration and machining stress, accurately ensuring the dimensional accuracy, roundness, and coaxiality of the inner hole of the pipe, and improving the quality of the inner hole machining.

[0036] It is worth noting that in the S5 wall thickness equalization adjustment process, the radial feed compensation of the grinding wheel is... Determined by the following equation: ; in: The first along the axial direction of the pipe fitting One measurement section location (unit: mm); For the first The first section Measured wall thickness in each angular direction (unit: mm); This is the arithmetic mean of the wall thickness of the cross section (unit: mm). This represents the number of measurement points for the wall thickness of this cross-section; The axial center position of the pipe fitting (unit: mm); Total length of the pipe fitting (unit: mm); The material stiffness correction factor (dimensionless, ranging from 0.6 to 0.9) is determined by the ratio of the elastic modulus of silicon carbide ceramic to the contact stiffness of the grinding wheel. The wall thickness deviation attenuation factor (dimensionless, ranging from 1.5 to 3.0) is used to characterize the priority attenuation rate of deviation correction along the axial direction. For the first Radial feed compensation of the grinding wheel at each cross section (unit: mm), a positive value indicates increased feed, and a negative value indicates decreased feed.

[0037] The derivation of the equation is as follows: 1. Objective In the wall thickness equalization adjustment process, the radial position of the grinding wheel needs to be dynamically adjusted according to the measured wall thickness distribution of each section so that the final wall thickness approaches uniformity.

[0038] 2. Definition of Deviation Definition of the first The first section The wall thickness deviation at each measuring point is: ; This deviation reflects the degree to which the wall thickness at that point deviates from the average value of that section.

[0039] 3. Average deviation of cross section To avoid interference from single-point noise, the arithmetic mean of the deviations at all measuring points on this cross-section is taken: ; This value reflects the overall tendency of the cross section to be thicker (positive) or thinner (negative).

[0040] 4. Axial attenuation weight The midsection of ultra-long, thin-walled tubular components exhibits poor rigidity and is more sensitive to center offset, while the ends are subject to stronger tooling constraints. Therefore, an axial attenuation weighting function is introduced: ; when When the weight is 1, the correction priority is the highest; Attenuation towards both ends, attenuation rate from control.

[0041] 5. Material stiffness correction Silicon carbide is highly brittle, and the feed compensation should not be too large, otherwise it is prone to edge chipping. A correction factor is introduced. The elastic modulus of the material Contact stiffness with grinding wheel Ratio calibration: ; This coefficient ensures that the compensation amount is within the material safety threshold.

[0042] 6. Final Equation Based on the above logic, the radial feed compensation amount of the grinding wheel is obtained as follows: ; Right now: .

[0043] Parameter Description Summary Table:

[0044] Example, known conditions: Total length of pipe fittings ,center ; A certain cross section At this location, the wall thickness at four measuring points is 2.8, 3.0, 3.2, and 3.0 mm. average value ; Deviation sequence: -0.2, 0, +0.2, 0 → Average deviation ; but This section requires no compensation.

[0045] Another section At the locations, the wall thickness at the measuring points is 3.4, 3.5, 3.5, and 3.6 mm. Average value 3.5mm, average deviation +0.1mm; Weight ; Pick ; but ; This indicates that the feed for this section should be increased by 0.041 mm to reduce the thickness.

[0046] Working principle and process integration: Measurement: In the S5 process, the wall thickness data of each section is obtained using an online thickness gauge; Calculation: Substitute into the above equation and calculate section by section. ; Execution: The radial feed of the grinding wheel is adjusted in real time through the CNC system to differentiate the feed amount for each section; Iteration: Before fine grinding, the measurement can be repeated. If the deviation still exceeds the threshold, repeat the above steps. Effect: It enables active, quantitative, and controllable correction of wall thickness uniformity, replacing the traditional experience-based "borrowing center" method.

[0047] Based on the above technical solutions, the working steps of this solution are summarized and organized. First, the equipment was modified by adding a high-speed spindle to the conventional milling and turning machine tool to improve the upper limit of the machine tool speed and the processing stability, providing an equipment foundation for high-speed grinding operations and meeting the speed requirements of high-precision grinding of silicon carbide pipes. After the equipment modification is completed, blank inspection and pretreatment are carried out. The focus is on inspecting the ellipticity of the pipe blank. For the problem of ellipticity exceeding the tolerance during the blank forming process, the basic shape of the blank is corrected by rough machining to find the roundness, eliminating the shape deviation of the original blank, laying the foundation for subsequent precision grinding, and avoiding the continuous accumulation of original errors that affect the accuracy of the finished product. Subsequently, specialized tooling is used to clamp and fix the pre-treated pipe fittings. Considering the characteristic that thin-walled pipe fittings are easily deformed by pressure, a general-purpose rough and finish machining outer circle support clamping tooling is used to achieve precise clamping and positioning. The tooling uses the base 100 fixed on the milling and turning machine tool as the bearing foundation to ensure that the clamping reference is consistent with the machine tool machining reference. The outer circle support assembly is assembled on the top of the base 100 through a connecting support composed of threaded pipe 101 and nut 103. The outer circle support assembly is spliced ​​by semi-circular brackets 102 on both sides of the pipe fitting, connecting plates 104, and fastening bolts 105. It can be flexibly opened and closed according to the outer diameter of the pipe fitting, forming a ring-shaped rolling support structure on the outer circumference of the pipe fitting. The tooling replaces traditional rigid clamping with multi-point uniform support, which can flexibly adjust the support height and locking force, effectively offset the radial cutting force of grinding, suppress pipe vibration, avoid stress concentration and extrusion deformation problems of single-point support, limit the radial and axial sway of pipe, ensure the clamping stability and workpiece integrity of ultra-long thin-walled pipe, and provide a precise machining benchmark for subsequent grinding processes. After clamping, rough grinding of the outer circle is carried out to adapt to the high hardness and brittleness of silicon carbide material. Diamond grinding wheel is used to perform overall rough grinding of the outer circle of the pipe fitting, quickly remove excess material from the outer circle of the pipe fitting, correct surface unevenness defects, and initially form the basic outline of the outer circle of the pipe fitting. At the same time, reasonable machining allowance is reserved for subsequent wall thickness adjustment and fine grinding. This process utilizes a special end-sealing clamping fixture for rough grinding. The fixture base 100 has a pipe insertion groove on its top, ensuring precise alignment of the pipe bottom and limiting radial displacement. Multiple threaded rods 201 are arranged in a ring inside the base 100, vertically penetrating the end-sealing plate 200 at the upper end of the pipe and locking with nuts 202, forming a fixed structure with internal multi-point clamping and a closed top. This fixture applies uniform clamping force from inside the pipe, preventing external clamping from damaging the outer wall of the thin-walled pipe. Simultaneously, the end-sealing plate 200 enhances the overall rigidity of the pipe, effectively resisting vibrations and impacts generated by large-mass cutting during rough grinding, preventing loosening and displacement of the pipe, and ensuring a stable and reliable rough grinding process. After rough grinding with a pre-existing allowance, the core wall thickness equalization adjustment process is carried out. The workpiece is centered and corrected by precisely adjusting the relative position of the machine tool spindle and the tooling. Specifically, the actual wall thickness distribution of each section of the pipe is detected, the deviation areas of excessive or insufficient wall thickness are located, and the relative position of the grinding wheel and the pipe is dynamically adjusted according to the real-time wall thickness distribution data. This corrects the center offset problem caused by clamping, equipment deviation, and the characteristics of the workpiece itself during the pipe processing, and equalizes the wall thickness of each section of the pipe, thus completely improving the defect of uneven wall thickness in the finished product. After the wall thickness correction is completed, the outer diameter is finely ground. The grinding speed of the machine tool spindle is increased, and the outer diameter of the rough-ground pipe is finely ground to gradually grind to the finished product design size. At the same time, the surface roughness of the outer diameter of the pipe is optimized and minor shape errors are corrected to ensure the dimensional accuracy of the outer diameter and the surface processing quality. Finally, the inner hole of the pipe fitting is machined. Based on the accuracy of the outer circle machining and the uniformity of the wall thickness, the inner hole of the pipe fitting is machined in a regular and fine manner using a special inner hole machining positioning fixture. The fixture base 100 is fixed to the machine tool, and the top is connected to the positioning sleeve 302 fitted on the outer periphery of the pipe fitting. The positioning sleeve 302 is provided with a reinforcing frame 300 on the outside to improve the overall structural strength and avoid deformation of the fixture itself during the machining process. Multiple sets of positioning bolts 301 are arranged equidistantly around the outer circumference of the positioning sleeve 302. The ends of the bolts are pressed against the outer wall of the pipe fitting. The machining center of the pipe fitting is corrected by a multi-point uniform limiting method, which ensures the coaxiality of the pipe fitting and the machine tool spindle. This effectively avoids problems such as dimensional deviation and roundness deviation caused by pipe fitting eccentricity and shaking during inner hole machining, offsets cutting vibration and stress load, and accurately ensures the machining accuracy and form and position tolerance of the inner hole. Finally, it produces ultra-long silicon carbide thin-walled finished pipe fittings with accurate dimensions, uniform wall thickness and qualified performance.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-speed grinding method for ultra-long silicon carbide thin-walled tubes, characterized in that, Includes the following steps: S1. Equipment Modification: Install a high-speed spindle on a milling and turning machine tool; S2. Blank Inspection and Pre-treatment: Inspect the ovality of the pipe fitting blank. If the ovality exceeds the standard threshold, perform rough machining to find the roundness of the blank. S3. Clamping: Use special tooling to position and fix the pipe fittings; S4. Rough grinding: Use a diamond grinding wheel to perform rough grinding on the outer circle of the pipe fitting; S5. Wall thickness equalization adjustment: When the outer diameter of the pipe is ground to the reserved machining allowance, measure the wall thickness of each section of the pipe and adjust the relative position of the grinding wheel and the pipe according to the wall thickness distribution. S6. Precision grinding: The outer diameter of the pipe fitting is precision ground to the specified dimensions of the finished product; S7. Internal bore machining: Perform precision machining on the internal bore of the pipe fitting.

2. The high-speed grinding method for ultra-long silicon carbide thin-walled tubes according to claim 1, characterized in that, In the S5 wall thickness equalization adjustment process, the pipe fitting is corrected by adjusting the relative position of the machine tool spindle and the tooling.

3. The high-speed grinding method for ultra-long silicon carbide thin-walled tubes according to claim 1, characterized in that, The spindle speed range of the S4 rough grinding process is 3000-4000 rpm, and the depth of cut per pass is 0.1-0.3 mm.

4. The high-speed grinding method for ultra-long silicon carbide thin-walled tubes according to claim 2, characterized in that, The spindle speed range for the S6 precision grinding process is 4000–6000 rpm.

5. A special tooling for implementing the S3 step of the method according to claim 1, characterized in that, It includes a base (100) and an outer circular support assembly; the base (100) is mounted on a milling and turning machine tool, the outer circular support assembly is sleeved on the outer peripheral wall of the pipe, and the outer circular support assembly rolls in contact with the outer wall of the pipe to provide radial support to the pipe; the top surface of the base (100) is provided with a connecting support for connecting the outer circular support assembly.

6. The special tooling according to claim 5, characterized in that, The outer circular support assembly includes semi-circular brackets (102) disposed on both sides of the pipe fitting; the opposite ends of the two sets of semi-circular brackets (102) are respectively fixed to connecting plates (104), and the two sets of connecting plates (104) on the same side are locked together by fastening bolts (105).

7. The special tooling according to claim 5, characterized in that, The connecting support includes multiple sets of threaded tubes (101); the multiple sets of threaded tubes (101) are threaded to the top surface of the base (100) and arranged around the outer periphery of the tubes, and the top of each set of threaded tubes (101) is provided with a corresponding side semi-circular bracket (102) and is threaded to a nut (103) for pressing the semi-circular bracket (102).

8. A special tooling for implementing step S4 of the method according to claim 1, characterized in that, Includes a base (100); the base (100) is assembled on a milling and turning machine tool, and a groove is provided on the top surface of the base (100) for the lower end of the pipe to be inserted and positioned; the top surface of the base (100) is fitted with an end cap (200) on the upper end of the pipe through a connector.

9. The special tooling according to claim 8, characterized in that, The connector includes multiple sets of annularly arranged threaded rods (201); the multiple sets of threaded rods (201) are threaded to the top surface of the base (100) and placed inside the pipe, and the top of each set of threaded rods (201) is inserted through an end sealing plate (200) and threaded to a nut (202) for pressing the end sealing plate (200).

10. A special tooling for implementing step S7 of the method according to claim 1, characterized in that, The device includes a base (100) and a positioning sleeve (302); the base (100) is mounted on a milling and turning machine tool, the positioning sleeve (302) is sleeved on the outer periphery of the pipe fitting, and the bottom of the positioning sleeve (302) is fixedly connected to the top surface of the base (100); the outer periphery of the positioning sleeve (302) is threaded with multiple sets of positioning bolts (301), the multiple sets of positioning bolts (301) are arranged in a ring at equal intervals from top to bottom along the axial direction of the positioning sleeve (302), and the end of each set of positioning bolts (301) is threaded through the positioning sleeve (302) and abuts against the outer wall of the pipe fitting; the outer periphery of the positioning sleeve (302) is fixedly sleeved with a reinforcing frame (300).

Images