A device for polishing the inner and outer walls of an oil pipe

Abstract

This invention relates to the field of machining and automated surface treatment equipment, specifically to a grinding and polishing device for the inner and outer walls of oil pipes. It includes a bed base, a spindle box chuck, a tailstock center, an outer grinding mechanism, and an inner grinding mechanism. The device uses the spindle box and tailstock to stably support and clamp both ends of the oil pipe, and utilizes the grinding mechanisms on both sides to simultaneously process the inner and outer walls. Its core is the use of a hollow cantilever rod with a built-in support cylinder and an internal feed cylinder to provide dynamically adjustable radial support and pressure to the grinding head, ensuring constant pressure grinding of the inner wall of the oil pipe. This invention replaces the multiple clamping and transfer processes and secondary clamping of split-type equipment, solving the coaxiality deviation problem caused by these processes, effectively ensuring machining position accuracy and shortening the auxiliary processing time for process changes.

Description

Technical Field

[0001] This invention relates to the field of machining and automated surface treatment equipment, specifically to a device for grinding and polishing the inner and outer walls of oil pipes. Background Technology

[0002] In the current oil pipe processing and manufacturing environment, the inner and outer surfaces of slender pipes typically require precision rotary grinding and polishing. Existing solutions for surface treatment of the inner and outer walls of oil pipes generally employ a split-type grinding architecture, where the outer and inner walls of the workpiece are ground separately at different workstations or with independent equipment. While this solution provides basic surface material removal capabilities, the fragmented processing flow necessitates secondary clamping of the workpiece during multiple process transfers, leading to accumulated coaxiality deviations. Furthermore, in inner wall grinding scenarios, existing equipment often employs a long cantilever structure with a rigidly fixed grinding head at the end. When encountering fluctuations in the ellipticity of the pipe wall or local undulations, it can only rely on the bending of the long cantilever body for elastic avoidance, resulting in a delayed force response. This causes the grinding head to experience cutting overload at local diameter reduction points and missed grinding at local diameter expansion points. In addition, due to the high concentration of dust and oil inside the closed pipe cavity, conventional optical sensing elements are difficult to place and prone to failure, preventing effective feedback of internal morphological fluctuations to the actuator.

[0003] Therefore, how to eliminate the loss of positional accuracy caused by secondary clamping and achieve adaptive continuous dynamic adjustment of the long cantilever grinding end to the undulation of the pipe wall in a highly disturbed closed cavity has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a device for grinding and polishing the inner and outer walls of oil pipes. Specifically, the technical solution of the present invention includes:

[0005] A bed base is provided, with a spindle box fixedly connected to one end of the bed base. A three-jaw self-centering chuck is provided at the output end of the spindle box. A tailstock is slidably connected to the other end of the bed base. The three-jaw self-centering chuck is used to clamp one end of the oil pipe. The tip of the tailstock is used to support the outer wall of the other end of the oil pipe. An external grinding mechanism is provided on one side of the bed base parallel to the axis of the spindle box.

[0006] An internal grinding mechanism is provided on the other side of the bed base, parallel to the axis of the spindle box. The internal grinding mechanism includes an internal grinding slide and a hollow cantilever rod. One end of the hollow cantilever rod is rigidly fixed to the top surface of the internal grinding slide. The other end of the hollow cantilever rod extends into the oil pipe. An internal grinding spindle and an internal feed cylinder are provided inside the free end of the hollow cantilever rod. A flap wheel grinding head is connected to the front end of the internal grinding spindle. A support cylinder is provided on the side of the hollow cantilever rod facing away from the flap wheel grinding head.

[0007] In one embodiment: a rotating spindle is supported inside the spindle box by tapered roller bearings, the output flange of the rotating spindle is fixedly connected to the three-jaw self-centering chuck by bolts, a servo motor is fixedly connected above the spindle box, and the output shaft of the servo motor directly drives the rotating spindle to rotate via a synchronous belt.

[0008] In one embodiment: the external grinding mechanism includes a first linear guide rail, an external grinding slide, an external feed cylinder, and an external sander. The first linear guide rail is fixedly connected to one side of the bed base parallel to the axis of the rotating spindle. The external grinding slide is slidably connected to the first linear guide rail. The external feed cylinder is horizontally fixedly connected to the top surface of the external grinding slide. The push rod end of the external feed cylinder is connected to the external sander through a flange. The contact wheel of the external sander faces the outer wall of the oil pipe.

[0009] In one embodiment: a second linear guide is fixedly connected to the other side of the bed base parallel to the axis of the rotating spindle, the inner grinding slide is slidably connected to the second linear guide, and the top surface of the inner grinding slide is rigidly fixed to one end of the hollow cantilever rod by four high-strength bolts. The main body of the hollow cantilever rod is a seamless steel pipe with an outer diameter of 80mm and a wall thickness of 10mm.

[0010] In one embodiment: the free end of the hollow cantilever bar is machined with a transverse groove, the internal grinding spindle is slidably connected in the groove, the front end of the internal grinding spindle is connected to the flap wheel grinding head through a right angle gearbox, the rear of the groove is fixedly connected to the internal feed cylinder, and the push rod of the internal feed cylinder directly pushes the tail end of the internal grinding spindle.

[0011] In one embodiment: the hollow cantilever rod has a radial through hole machined on the side facing away from the flap wheel grinding head, the support cylinder is fixedly installed in the radial through hole, the piston rod of the support cylinder extends toward the inner wall of the oil pipe, and a polyurethane support wheel is hinged to the end of the piston rod of the support cylinder by a pin, and the polyurethane support wheel is in contact with the inner wall of the oil pipe.

[0012] In one embodiment: an electro-proportional valve is connected in series in the air intake circuits of the external feed cylinder, the internal feed cylinder, and the support cylinder; the internal grinding spindle is driven by a high-speed motor built into the hollow cantilever rod through a flexible coupling.

[0013] In one embodiment: the device further includes an industrial computer and a spindle angle encoder. The industrial computer is configured to perform current-based inner wall undulation detection. During the detection phase, the servo motor drives the three-jaw self-centering chuck to rotate the oil pipe at a set detection speed of 10 r / min. The inner grinding slide drives the hollow cantilever rod into the inside of the oil pipe. The electro-proportional valve of the support cylinder outputs a set constant air pressure to drive the polyurethane support wheel to press against the inner wall of the oil pipe.

[0014] The internal feed cylinder does not output pressure, the high-speed motor starts and maintains no-load speed, the industrial control computer combines the signal of the spindle angle encoder to obtain the current fluctuation parameters of the high-speed motor in real time, and obtains the radial deviation distribution of the pipe wall based on the current fluctuation parameters.

[0015] In one embodiment, the industrial computer is further configured to perform air pressure correction value calculation, and based on the detected radial deviation distribution, generate in advance the air pressure correction value for the next processing cycle corresponding to different pipe wall undulation regions.

[0016] In one embodiment: the industrial computer is also configured to perform synchronous processing and pressure regulation. During the synchronous processing stage, the servo motor increases the oil pipe speed to a normal processing speed of 300 r / min. The outer grinding slide and the inner grinding slide are synchronously fed axially along the linear guide rail. The outer feed cylinder outputs constant pressure.

[0017] The industrial control computer calls the air pressure correction value in real time and converts it into a control signal to send to the electric proportional valve based on the current axial position of the hollow cantilever rod and the rotation angle of the oil pipe. It dynamically adjusts the pressure of the internal feed cylinder and the support cylinder, and continuously monitors the actual cutting current of the high-speed motor during the machining process.

[0018] If the difference between the actual cutting current and the reference cutting current exceeds the preset allowable fluctuation threshold, the industrial control computer dynamically reduces the feedforward pressure command of the internal feed cylinder based on the difference; if the difference does not exceed the allowable fluctuation threshold, the feedforward pressure command generated by the current internal feed cylinder based on the air pressure correction value remains unchanged.

[0019] The present invention has the following beneficial effects:

[0020] 1. This invention arranges the external grinding mechanism and the internal grinding mechanism on both sides of the bed base, respectively. With the help of the three-jaw self-centering chuck of the spindle box and the tailstock center, the two ends of the oil pipe are stably supported and clamped, realizing the synchronous grinding of the inner and outer walls of the slender oil pipe in the same clamping state. This structure completely overcomes the coaxiality deviation problem that is easy to occur in traditional split equipment during multiple process transfers and secondary clamping, effectively ensuring the machining position accuracy and greatly improving production efficiency.

[0021] 2. This invention utilizes an industrial control computer to perform internal wall undulation detection based on high-speed motor current, accurately obtaining the radial deviation distribution of the pipe wall without the need to place optical sensors inside the oil- and dust-filled pipe cavity. During the processing stage, by calling the air pressure correction value in real time and combining it with an electric proportional valve, the output pressure of the internal feed cylinder and the support cylinder is dynamically adjusted, enabling the flap wheel grinding head to adapt to the local undulations and ellipticity errors of the pipe wall. This effectively avoids the problem of overload at local diameter reduction points or missed grinding at diameter expansion points in the long cantilever structure, achieving high-precision constant pressure grinding. Attached Figure Description

[0022] The following drawings, illustrating embodiments of this application, are incorporated herein by reference and are used to understand this application. The drawings illustrate embodiments of this application and their descriptions, serving to explain the principles of this application. In the drawings,

[0023] Figure 1 This is a schematic diagram of the overall structure of the device;

[0024] Figure 2 This is a cross-sectional view of the spindle box of the device;

[0025] Figure 3 This is a schematic diagram of the structure of the first linear guide rail and the outer grinding slide of the device;

[0026] Figure 4 This is a schematic diagram of the structure of the second linear guide rail and the inner grinding slide of the device;

[0027] Figure 5 This is a schematic diagram of the structure of the free end of the hollow cantilever rod and the polyurethane support wheel on it.

[0028] In the diagram: 1. Bed base; 2. Spindle box; 3. Three-jaw self-centering chuck; 4. Tailstock; 5. Center; 6. External grinding mechanism; 7. Internal grinding mechanism; 8. Internal grinding slide; 9. Hollow cantilever rod; 10. Internal grinding spindle; 11. Internal feed cylinder; 12. Flap wheel grinding head; 13. Support cylinder; 14. Tapered roller bearing; 15. Rotary spindle; 16. Output flange; 17. Bolt; 18. Servo motor; 9. Synchronous belt; 20. First linear guide; 21. External grinding slide; 22. External feed cylinder; 23. External belt sander; 24. Contact wheel; 25. Second linear guide; 26. High-strength bolt; 27. Slide groove; 28. Right-angle gearbox; 29. ​​Push rod; 30. Radial through hole; 31. Piston rod; 32. Pin shaft; 33. Polyurethane support wheel; 34. Electro-proportional valve; 35. High-speed motor; 36. Flexible coupling. Detailed Implementation

[0029] In the following description, numerous specific details are set forth to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that embodiments of this application may be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with embodiments of this application.

[0030] Example 1:

[0031] Combination Figure 1 A device for grinding and polishing the inner and outer walls of oil pipes, comprising:

[0032] A bed base 1 is provided, with a spindle box 2 fixedly connected to one end of the bed base 1. A three-jaw self-centering chuck 3 is provided at the output end of the spindle box 2. A tailstock 4 is longitudinally slidably connected to the other end of the bed base 1. The three-jaw self-centering chuck 3 is used to clamp one end of the oil pipe, and the tip 5 of the tailstock 4 is used to support the outer wall of the other end of the oil pipe. An external grinding mechanism 6 is provided on one side of the bed base 1 parallel to the axis of the spindle box 2, and an internal grinding mechanism 7 is provided on the other side of the bed base 1 parallel to the axis of the spindle box 2.

[0033] The internal grinding mechanism 7 includes an internal grinding slide 8 and a hollow cantilever rod 9. One end of the hollow cantilever rod 9 is rigidly fixed to the top surface of the internal grinding slide 8, and the other end of the hollow cantilever rod 9 extends into the oil pipe. An internal grinding spindle 10 and an internal feed cylinder 11 are installed inside the free end of the hollow cantilever rod 9. The front end of the internal grinding spindle 10 is connected to a flap wheel grinding head 12. A support cylinder 13 is installed on the side of the hollow cantilever rod 9 facing away from the flap wheel grinding head 12.

[0034] In this embodiment, the bed base 1 serves as the mounting foundation for the entire machine, used to maintain the relative positional accuracy between the spindle box 2, tailstock 4, external grinding mechanism 6, and internal grinding mechanism 7; the spindle box 2 cooperates with the three-jaw self-centering chuck 3 to complete the clamping drive of one end of the oil pipe, and the tip 5 of the tailstock 4 forms a support on the outer wall of the other end of the oil pipe, thereby stably holding the slender oil pipe on the predetermined axis of rotation, so as to solve the problem of coaxiality deviation caused by secondary clamping in traditional split equipment;

[0035] To ensure that the hollow cantilever rod 9 of the internal grinding mechanism 7 can be smoothly fed axially, the center 5 of the tailstock 4 adopts a sleeve-type hollow rotary center structure. Its inner diameter is larger than the maximum outer diameter of the hollow cantilever rod 9 and the flap wheel grinding head 12. While supporting the outer wall of the oil pipe through the inner conical surface, it also retains a smooth axial cavity channel for the vertically inserted hollow cantilever rod 9.

[0036] The external grinding mechanism 6 is arranged on one side of the bed base 1 and is used to perform synchronous grinding on the outer wall of the oil pipe; the internal grinding mechanism 7 is arranged on the other side and uses the internal grinding slide 8 to drive the hollow cantilever rod 9 to enter the cavity along the oil pipe axis; the free end of the hollow cantilever rod 9 is equipped with an internal grinding spindle 10 and an internal feed cylinder 11, the flap wheel grinding head 12 is located at the front end of the internal grinding spindle 10, and the support cylinder 13 is located on the side opposite to the flap wheel grinding head 12. The two constitute a radially arranged execution unit.

[0037] The key technical feature of this structure is that the radial feed force output by the internal feed cylinder 11 and the back support force output by the support cylinder 13 work together in the area where the flap wheel grinding head 12 is located, so that the long cantilever internal grinding part no longer relies solely on the rigidity of the cantilever rod body to bear the cutting reaction force, but forms an adjustable force support relationship near the inner wall of the oil pipe.

[0038] With the above structure, the contact pressure of the flap wheel grinding head 12 against the inner wall of the oil pipe can be continuously changed by air pressure adjustment. This can adapt to the ellipticity error, local undulations and oxide scale thickness changes in the inner wall of the oil pipe, reduce the probability of overload at local diameter reduction and missed grinding at local diameter expansion of the fixed grinding head, and enable the inner and outer wall processing to be completed simultaneously under the same clamping state.

[0039] Combination Figure 2 The spindle box 2 is supported by a tapered roller bearing 14. The output flange 16 of the spindle 15 is fixedly connected to a three-jaw self-centering chuck 3 by bolts 17. A servo motor 18 is fixedly connected to the top of the spindle box 2. The output shaft of the servo motor 18 directly drives the spindle 15 to rotate through a synchronous belt 19.

[0040] In this embodiment, the rotating spindle 15 is supported by a tapered roller bearing 14 inside the spindle box 2. The tapered roller bearing 14 in this device is a spindle support unit that simultaneously bears radial and axial loads. Its purpose is to withstand the combined load introduced by the grinding of the inner and outer walls when the oil pipe rotates, and to maintain the rotational stability of the chuck end. The output end of the rotating spindle 15 is connected to the three-jaw self-centering chuck 3 by bolts 17 through a flange. This connection method facilitates the disassembly and maintenance of the chuck, and also facilitates the replacement of clamps with different clamping capacities according to the specifications of the oil pipe.

[0041] The servo motor 18 is fixed above the spindle box 2 and transmits power to the rotating spindle 15 through the synchronous belt 19. The technical consideration of the synchronous belt 19 transmission in this embodiment is to isolate the vibration and impact of the motor end and maintain a stable transmission ratio, so that the spindle speed can be maintained at a low speed during the contour detection stage and can be increased to the set processing speed during the formal processing stage.

[0042] The control signal of the servo motor 18 is output by the industrial control computer. The industrial control computer switches the spindle speed according to different process stages to ensure that the low-speed sampling conditions required for inner wall undulation detection and the high-speed cutting conditions required for formal grinding are met respectively. Since the spindle drive part has controllable speed and stable rotation accuracy, the subsequent morphology inversion based on current change has a repeatable data basis.

[0043] Combination Figure 3 The external grinding mechanism 6 includes a first linear guide 20, an external grinding slide 21, an external feed cylinder 22, and an external sander 23. The first linear guide 20 is fixedly connected to one side of the bed base 1 parallel to the axis of the rotating spindle 15. The external grinding slide 21 is slidably connected to the first linear guide 20. The external feed cylinder 22 is fixedly connected to the top surface of the external grinding slide 21 laterally. The push rod end of the external feed cylinder 22 is connected to the external sander 23 through a flange. The contact wheel 24 of the external sander 23 faces the outer wall of the oil pipe.

[0044] In this embodiment, the first linear guide 20 is installed on one side of the bed base 1 along the axis of the rotating spindle 15. The outer grinding slide 21 and the first linear guide 20 form a linear sliding pair, which is used to support the outer belt sander 23 and realize the feed movement along the oil pipe axis. The outer feed cylinder 22 is horizontally fixed on the top surface of the outer grinding slide 21, and its push rod 29 end is connected to the outer belt sander 23 through a flange, so that the outer belt sander 23 can apply continuously adjustable contact pressure to the outer wall of the oil pipe in the radial direction.

[0045] The contact wheel 24 is positioned directly opposite the outer wall of the oil pipe. Its function is to stably transmit the grinding pressure after the abrasive belt is tensioned to the workpiece surface. The reason why the external grinding mechanism 6 uses cylinder feeding instead of rigid fixed-distance pressing is that when there are manufacturing tolerances and differences in surface rust thickness in the outer diameter of the oil pipe, the external feed cylinder 22 can automatically compensate for the contact amount by setting the pressure, so as to avoid the abrasive belt slipping due to local high points or insufficient removal due to local low points.

[0046] The axial movement of the outer grinding slide 21 can be driven by an independent drive unit or moved synchronously with the linkage mechanism of the inner grinding slide 8, thereby ensuring that the corresponding axial areas of the inner and outer walls are processed simultaneously in the same processing cycle. This structure allows the outer wall grinding part to maintain a relatively simple constant pressure working mode and forms a division of labor with the adaptive control of the inner wall side, which not only meets the conventional grinding requirements of the outer surface, but also provides a structural basis for the synchronous processing of the whole machine.

[0047] Combination Figure 4On the other side of the bed base 1, a second linear guide rail 25 is fixedly connected to the axis of the rotating spindle 15. The inner grinding slide 8 is slidably connected to the second linear guide rail 25. The top surface of the inner grinding slide 8 is rigidly fixed to one end of the hollow cantilever rod 9 by four high-strength bolts 26. The main body of the hollow cantilever rod 9 is a seamless steel pipe with an outer diameter of 80mm and a wall thickness of 10mm.

[0048] In this embodiment, the second linear guide 25 is located on the side of the bed base 1 opposite to the outer grinding mechanism 6, and its extension direction is parallel to the axis of the rotating spindle 15. The inner grinding slide 8 slides axially on the guide to send the hollow cantilever rod 9 into the oil pipe at different length positions. In addition, high-precision linear displacement sensors or grating rulers are arranged parallel to the first linear guide 20 and the second linear guide 25 to detect the real axial feed displacement of the outer grinding slide 21 and the inner grinding slide 8 in real time, and to feed back the collected linear guide feed displacement signal to the industrial control computer in real time.

[0049] The hollow cantilever rod 9 is rigidly fixed to the top surface of the inner grinding slide plate 8 by four high-strength bolts 26. This connection method is used to limit the relative displacement and rotation angle of the cantilever root and reduce the amount of vibration amplified by the loosening of the root after the long rod enters the oil pipe. The main body of the hollow cantilever rod 9 is made of seamless steel pipe with an outer diameter of 80mm and a wall thickness of 10mm. Its material is continuous and the wall thickness is uniform, which is suitable for taking into account bending stiffness, internal wiring and air distribution space and structural feasibility.

[0050] This size combination is not simply about increasing the cross-section of the rod, but rather works in conjunction with the support cylinder 13 subsequently located near the free end: the seamless steel pipe provides basic structural rigidity, and the support cylinder 13 provides local reaction force support near the grinding point. With the two working together, the deflection and vibration amplitude of the cantilever rod under cutting load can be reduced. The hollow structure also has another technical function, namely, providing an internal arrangement channel for the high-speed motor 35, cables, air circuits and coupling components, reducing the risk of interference between exposed pipelines and the inner wall when entering the oil pipe, and improving the feasibility of the slender internal grinding mechanism.

[0051] Example 2:

[0052] Combination Figure 4 and Figure 5 As shown, the free end of the hollow cantilever rod 9 has a transverse groove 27 machined inside. The inner grinding spindle 10 is slidably connected in the groove 27. The front end of the inner grinding spindle 10 is connected to the flap wheel grinding head 12 through the right angle gear box 28. The rear of the groove 27 is fixedly connected to the inner feed cylinder 11. The push rod 29 of the inner feed cylinder 11 directly pushes the tail end of the inner grinding spindle 10.

[0053] In this embodiment, the hollow cantilever rod 9 has a transverse groove 27 machined inside its free end. The transverse direction in this device refers to the radial adjustment direction relative to the axial feed direction of the oil pipe. The internal grinding spindle 10 is slidably installed in the groove 27, and its sliding pair is used to directly transmit the linear displacement and thrust output by the internal feed cylinder 11 to the grinding end.

[0054] The flap wheel grinding head 12 is connected to the front end of the inner grinding spindle 10 through a right-angle gearbox 28. The right-angle gearbox 28 converts the power transmission direction inside the spindle into an output direction suitable for inner wall grinding, so that the working surface of the flap wheel grinding head 12 faces the inner wall of the oil pipe. The inner feed cylinder 11 is fixed behind the slide groove 27, and the push rod 29 directly pushes the tail end of the inner grinding spindle 10 to reduce the gap and elastic deformation generated in the intermediate force transmission link.

[0055] The problem solved by this structural design is that if the grinding head is rigidly fixed to the end of the cantilever rod, it can only rely on the bending of the entire cantilever rod to elastically avoid fluctuations in the inner diameter, which can easily cause response delay and uneven grinding. With the use of a sliding internal grinding spindle 10, the grinding head can move radially forward and backward in a local range at the free end. The feed cylinder adjusts the direct contact pressure near the grinding head, rather than the large displacement deflection of the entire long rod. Therefore, it is more suitable for performing continuous pressure adjustment based on changes in cutting load. The combination of the right-angle gearbox 28 and the flap wheel grinding head 12 also concentrates the grinding contact area in the predetermined inner wall strip area, which makes it easier to control the amount of material removed and the surface roughness.

[0056] The hollow cantilever rod 9 has a radial through hole 30 on the side facing away from the flap wheel grinding head 12. The support cylinder 13 is fixedly installed in the radial through hole 30. The piston rod 31 of the support cylinder 13 extends toward the inner wall of the oil pipe. The end of the piston rod 31 of the support cylinder 13 is hinged to a polyurethane support wheel 33 through a pin 32. The polyurethane support wheel 33 is in contact with the inner wall of the oil pipe.

[0057] In this embodiment, the hollow cantilever rod 9 has a radial through hole 30 machined on the side opposite to the flap wheel grinding head 12. The support cylinder 13 is installed in the through hole, so that the point of application of the support reaction force is set close to the grinding action area to shorten the force transmission path. The piston rod 31 of the support cylinder 13 extends into the inner wall of the oil pipe, and the end is hinged to the polyurethane support wheel 33 via a pin 32. The function of the pin 32 hinge is to allow the support wheel to adaptively adjust its contact posture and reduce the edge stress concentration between the wheel surface and the inner wall. The function of the polyurethane material is to provide a certain elasticity and frictional stability, so that the support wheel can continuously fit against the inner wall without amplifying local impacts like a rigid metal wheel.

[0058] The function of this support unit in this device is not only to provide back support, but also to undertake the task of shape mechanical transmission. When the oil pipe has ellipticity or local radial undulation, the support wheel will roll along the inner wall and undergo a small radial displacement. This displacement is geometrically constrained by the installation position of the support cylinder 13 and the end of the cantilever rod, so that the relative contact state between the opposite flap wheel grinding head 12 and the pipe wall changes accordingly.

[0059] Thus, the shape and position error of the inner wall of the oil pipe is converted into a measurable change in the cutting load at the grinding head end; with this mechanical transmission method, there is no need to set up optical measuring devices in a high dust and oil environment, which can provide an feasible physical channel for subsequent identification of inner wall undulations using motor current.

[0060] An electric proportional valve 34 is connected in series on the air intake circuits of the external feed cylinder 22, the internal feed cylinder 11 and the support cylinder 13. The internal grinding spindle 10 is driven by a high-speed motor 35 built into the hollow cantilever rod 9 through a flexible coupling 36.

[0061] In this embodiment, the air intake circuits of the external feed cylinder 22, the internal feed cylinder 11, and the support cylinder 13 are connected in series with an electro-proportional valve 34. The specific meaning of the electro-proportional valve 34 in this device is that it is an actuator that receives continuous control signals and outputs corresponding continuous pressure, which is different from a common solenoid valve that only has an on / off function. After adopting the electro-proportional valve 34, the output pressure of the three sets of cylinders can be continuously adjusted within a set range. The external feed cylinder 22 is used to maintain the grinding pressure of the outer wall, the internal feed cylinder 11 is used to adjust the feed amount of the flap wheel grinding head 12 to the inner wall, and the support cylinder 13 is used to adjust the back support stiffness.

[0062] The internal grinding spindle 10 is driven by a high-speed motor 35 inside the cantilever. The high-speed motor 35 is connected to the internal grinding spindle 10 via a flexible coupling 36. The technical function of the flexible coupling 36 is to compensate for the slight deviation between the axis of the high-speed motor 35 and the axis of the internal grinding spindle 10 caused by cantilever deformation, installation error or thermal expansion, reduce the probability of additional bending moment being transmitted to the bearing of the high-speed motor 35, and reduce the pulsation in power transmission.

[0063] Since the high-speed motor 35 is located inside the hollow cantilever rod 9, the power transmission path is shortened, and the rotational inertia is concentrated near the inner grinding end, so the current change responds more directly to the cutting load. After the electric proportional valve 34 and the current signal of the high-speed motor 35 are combined, they form the basic hardware link from cutting load identification to air pressure regulation, which enables the subsequent detection and compensation methods to be implemented.

[0064] Example 3:

[0065] The device also includes an industrial control computer and a spindle angle encoder. The industrial control computer is configured to perform current-based detection of inner wall undulations. During the detection phase, the servo motor 18 drives the three-jaw self-centering chuck 3 to rotate the oil pipe at a set detection speed of 10 r / min. The inner grinding slide 8 drives the hollow cantilever rod 9 into the oil pipe. The electro-proportional valve 34 of the support cylinder 13 outputs a set constant air pressure to drive the polyurethane support wheel 33 to press against the inner wall of the oil pipe. The inner feed cylinder 11 does not output pressure. The high-speed motor 35 starts and maintains the no-load speed. The industrial control computer combines the signal from the spindle angle encoder to obtain the current fluctuation parameters of the high-speed motor 35 in real time, and obtains the radial deviation distribution of the pipe wall based on the current fluctuation parameters.

[0066] In this embodiment, the industrial control computer undertakes the data acquisition and calculation tasks during the detection phase; the current-based inner wall undulation detection refers to not directly measuring the geometric dimensions of the pipe wall, but using the change in current of the high-speed motor 35 caused by the slight contact between the flap wheel grinding head 12 and the inner wall under near-no-load conditions to deduce the radial undulation of the pipe wall; during the detection phase, the servo motor 18 drives the oil pipe to rotate at a low speed of 10 r / min. The purpose of setting this speed is to reduce centrifugal effect and impact interference, so that the support wheel contact displacement and current change maintain a relatively stable correspondence;

[0067] After the internal grinding slide 8 sends the hollow cantilever rod 9 into the oil pipe, the support cylinder 13 outputs a low constant air pressure through the electric proportional valve 34, so that only the polyurethane support wheel 33 keeps in contact with the inner wall. The internal feed cylinder 11 does not output pressure, and the flap wheel grinding head 12 does not undertake the actual grinding and removal task at this stage. The high-speed motor 35 maintains the no-load speed, and the industrial control computer synchronously collects the motor current signal and the spindle angular position signal, and subtracts the current fluctuation within one circumference range from the no-load current reference value to obtain the current difference sequence.

[0068] The empirical conversion coefficient is used to convert the current difference into a radial deviation value. This conversion logic essentially constitutes a current-morphology inversion model. The purpose of this model is to accurately estimate the true physical morphology of the local pipe wall under the working conditions of high dust and oil interference inside the closed cavity and the inability to place optical sensors, by using the small changes in the load of the high-speed motor 35. In terms of logical structure, the model receives the smoothed current difference as an input variable, combines it with the preset empirical conversion coefficient, and outputs the radial deviation value through linear mapping.

[0069] The model as a whole characterizes the positive correlation physical causal relationship between the increase in frictional resistance torque caused by mechanical contact when the flapper grinding head 12 has a slight interference with the pipe wall and the increase in electromagnetic torque required for the motor to maintain a constant speed. The model can be obtained by calibration test based on standard pipe samples of the same material, or by coefficient table pre-stored in the industrial control computer based on the oil pipe material grade and grinding head specifications.

[0070] The industrial control computer establishes a correspondence between the angular position and the radial deviation value, forming radial deviation distribution data. The technical effect of this detection method is that it converts the displacement disturbance generated by the mechanical contact of the support wheel into current signal characteristics, avoiding the introduction of external sensors that are susceptible to dust and oil interference in the closed cavity.

[0071] In this embodiment, the no-load current reference value refers to the stable current reference value of the high-speed motor 35 when the louver grinding head 12 does not press against the pipe wall and only overcomes its own bearing friction and air resistance. Its physical significance is to serve as a comparative baseline to distinguish between idling and being disturbed by the inner wall.

[0072] The determination of the benchmark value can be performed in the following order: the hollow cantilever rod 9 is inserted into the oil pipe, but a gap is maintained between the flap wheel grinding head 12 and the inner wall; the current of the high-speed motor 35 is continuously collected for a period of time at a predetermined no-load speed; after filtering out the start-up transient and occasional spikes, the average value of the stable range is taken as the no-load current benchmark value for this test cycle; if the same specification oil pipe is processed continuously, the benchmark value obtained from the previous calibration can also be called, and a quick comparison and correction can be performed before this test;

[0073] The physical meaning of the current difference is the amount of load increase of the actual sampled current relative to the no-load state. Its sign and magnitude correspond to the direction and strength of the disturbance to the grinding head, respectively. When the current difference is close to zero, it means that the radial interference of the inner wall at that angle to the grinding head is lower than the threshold. When the current difference continues to increase, it means that there is an inner wall protrusion that exceeds the tolerance zone or the contact force increases at that angle.

[0074] The empirical conversion coefficient is not determined by abstract assignment, but by establishing a correspondence between known radial deviation and corresponding current increment through calibration of a standard sample tube: during calibration, a standard sample tube with a measured inner diameter is selected and run at the same speed, support pressure, and motor speed as in the testing stage. The current increment at different known deviation positions is recorded, and the radial displacement corresponding to the unit current increment is taken as the conversion basis. The industrial control computer prioritizes the following processing flow during calculation:

[0075] Step 1: Synchronously read the spindle angle encoder signal and the analog current signal of the high-speed motor 35 driver at a fixed sampling period, and package them into a synchronous data frame with a timestamp.

[0076] Step 2: Using the no-load current reference value, calculate the current difference at each sampling angle point by point;

[0077] Step 3: Smooth the current difference between multiple consecutive sampling points to reduce isolated jumps caused by brush noise, power supply ripple, or accidental particle contact.

[0078] Step 4: Multiply the smoothed current difference by the empirical conversion factor to convert it into the corresponding radial deviation value.

[0079] Step 5: Store the radial deviation distribution as a circle according to the angular order;

[0080] The theoretical basis for the above linear mapping is that, under near-unload conditions and with a small contact depth, the interference deformation between the flap wheel grinding head 12 and the pipe wall is approximately proportional to the normal pressing force. The frictional resistance torque generated by the normal pressing force is also proportional to the electromagnetic torque increment required for the motor to maintain a constant low speed. Therefore, the current difference can be used as a reliable physical quantity to characterize the radial deviation distribution. The radial deviation distribution generated thereby is transmitted to the air pressure correction value calculation module as the input basis for the pressure pre-adjustment of the inner feed cylinder 11 and the support cylinder 13 in the next processing cycle.

[0081] The industrial computer is also configured to perform air pressure correction value calculation, and based on the detected radial deviation distribution, generate in advance the air pressure correction value for the next processing cycle corresponding to different pipe wall undulation areas;

[0082] In this embodiment, after obtaining the radial deviation distribution, the industrial control computer further performs the calculation of the air pressure correction value. The air pressure correction value refers to the increment or decrease relative to the basic working pressure of each cylinder. Its calculation goal is to keep the cutting load of the flap wheel grinding head 12 within a predetermined range when it enters different radial regions. This calculation process constructs a feedforward air pressure compensation model inside the system. The purpose of this model is to adjust the output of the pneumatic actuator in advance based on the known undulation morphology of the inner wall in order to actively adapt to changes in pipe diameter.

[0083] In terms of data flow and logical structure, the model receives the radial deviation distribution generated in the previous stage as the input variable. After passing through the piecewise linear proportional calculation module, it outputs the feed air pressure correction value to the inward feed cylinder 11 and the support air pressure correction value to the support cylinder 13. The physical relationship represented by the model is: by increasing or decreasing the air pressure in advance, the local mechanical interference or separation caused by the protrusion or depression of the pipe wall is offset, so that the flap wheel grinding head 12 always maintains a constant normal pressure in the complex inner wall environment, thereby avoiding motor stalling caused by local overload or missed grinding caused by local disconnection.

[0084] For the bulging area where the pipe diameter is reduced, the industrial control computer identifies the corresponding angle range from the radial deviation distribution and calculates the negative correction value of the inner feed cylinder 11 and the positive correction value of the support cylinder 13 according to the preset proportional relationship. After the inner feed pressure is reduced, the tendency of the grinding head to press into the inner wall is reduced. After the support pressure is increased, the back support at the cantilever end is strengthened, thereby reducing local overcutting and cantilever deflection.

[0085] For the concave area with increased pipe diameter, the industrial control computer calculates the positive correction value of the internal feed cylinder 11 to give the grinding head additional pressure and reduce the area of ​​missed grinding; the preset proportional relationship can be a linear proportional relationship or a piecewise linear proportional relationship, as long as the correction value changes in the same direction as the radial deviation increases.

[0086] The industrial control computer uses the angular position, axial position and correction value to form a lookup table or function mapping for use in the next machining cycle. The technical significance of this pre-calculation method is that it converts the morphological information obtained in the detection stage into pressure commands at the execution end in advance, reduces the impact of the response lag of the pneumatic actuator on the grinding uniformity, and enables the system to have the corresponding mechanical preparation before reaching the undulating area.

[0087] In this embodiment, the basic working pressure refers to the conventional output pressure of the cylinder determined by trial cutting under the conditions of standard pipe diameter, standard grinding head specifications and target surface roughness. The basic working pressure of the internal feed cylinder 11 is used to provide the average pressure required for normal grinding, and the basic working pressure of the support cylinder 13 is used to provide the average back support force to maintain the stability of the cantilever end.

[0088] The determination of raised and recessed areas does not rely on abstract subjective judgment, but is based on the positive and negative deviation direction of the radial deviation distribution relative to the reference radius of the inner circle of the target: when the radial deviation at a certain angle position is such that the inner wall moves closer to the grinding head side, it is determined to be a raised area; when the radial deviation at a certain angle position is such that the inner wall moves away from the grinding head side, it is determined to be a recessed area.

[0089] To avoid misinterpreting random noise as true morphology, the industrial control computer prioritizes continuous filtering of radial deviation distribution, generating correction values ​​only for regions where multiple consecutive adjacent sampling angles exceed the minimum recognition amplitude. The minimum recognition amplitude serves to eliminate minor disturbances that do not significantly alter the cutting load; its value can be determined through calibration. The calibration boundary conditions are: current changes can be repeated during trial cutting, and no visible over- or under-wear has occurred on the inner wall surface. The calculation process for the air pressure correction value can be executed in the following order:

[0090] Step 1: Read the angular position, corresponding radial deviation value, and axial position of the cantilever rod within the current revolution from the test results;

[0091] Step 2: Compare the radial deviation value with the minimum identification amplitude. If it is less than this amplitude, keep the basic working pressure unchanged.

[0092] Step 3: If the amplitude is greater than this value, determine whether it belongs to a raised area or a recessed area;

[0093] Step 4: If it is a raised area, a negative correction value is generated for the inner feed cylinder 11 and a positive correction value is generated for the support cylinder 13. The absolute values ​​of the negative correction value and the positive correction value are proportional to the magnitude of the radial deviation value.

[0094] Step 5: If it is a concave area, a positive correction value is generated for the inner feed cylinder 11, while the support cylinder 13 maintains the basic working pressure.

[0095] Step 6: Write the calculation results into a two-dimensional array lookup table in angular order. The row index of the array corresponds to the axial feed coordinate, and the column index corresponds to the rotation angle coordinate.

[0096] Step 7: Perform a safety limit judgment on the calculated pressure correction values ​​of the internal feed cylinder 11 and the support cylinder 13. If the correction value exceeds the preset physical execution boundary, it will be forcibly cut off to the maximum allowable limit value to prevent the control command from causing cylinder overload damage.

[0097] The aforementioned preset proportional relationship can be implemented using two independent proportional coefficients applied to the inner feed branch and the support branch respectively. This technical implication is that it allows the same radial deviation to correspond to different correction sensitivities on the feed side and the support side, thereby balancing the grinding head's fit capability and the cantilever's stability. In addition, the industrial control computer and each pneumatic electrical proportional valve 34 exchange data via an industrial fieldbus or a high-frequency digital-to-analog converter interface to ensure that the feedforward air pressure command is accurately delivered to the execution end within a very short communication cycle. Through the above step-by-step processing, the source of the air pressure correction value, the judgment criteria, and its triggering role in the control logic are all clearly defined.

[0098] The industrial control computer is also configured to perform synchronous processing and pressure regulation. During the synchronous processing stage, the servo motor 18 increases the oil pipe speed to the normal processing speed of 300 r / min. The outer grinding slide 21 and the inner grinding slide 8 are synchronously fed axially along the linear guide rail. The outer feed cylinder 22 outputs constant pressure. The industrial control computer calls the air pressure correction value in real time and converts it into a control signal to send to the electric proportional valve 34 according to the current axial position of the hollow cantilever rod 9 and the rotation angle of the oil pipe. It dynamically adjusts the pressure of the inner feed cylinder 11 and the support cylinder 13, and continuously monitors the actual cutting current of the high-speed motor 35 during the processing.

[0099] If the difference between the actual cutting current and the reference cutting current exceeds the preset allowable fluctuation threshold, the industrial control computer dynamically reduces the feedforward pressure command of the internal feed cylinder 11 based on the difference; if the difference does not exceed the allowable fluctuation threshold, the feedforward pressure command generated by the current internal feed cylinder 11 based on the air pressure correction value remains unchanged.

[0100] In this embodiment, the industrial control computer executes the synchronous processing and pressure regulation process. During the synchronous processing stage, the servo motor 18 increases the oil pipe speed to 300 r / min. The outer grinding slide 21 and the inner grinding slide 8 maintain the corresponding axial feed relationship along their respective linear guides, so that the outer wall contact wheel 24 and the inner wall flap wheel grinding head 12 perform synchronous processing on the same axial area of ​​the oil pipe. The outer feed cylinder 22 maintains a constant pressure because the outer wall is supported by the chuck and the tailstock 4. The influence of the outer diameter change on the grinding stability is within the allowable fluctuation range preset by the process, and there is no need for dynamic air pressure compensation.

[0101] On the inner wall side, the industrial control computer extracts the corresponding correction value from the established air pressure correction mapping based on the current axial position of the cantilever rod and the rotation angle of the oil pipe, and converts it into a control signal for the electric proportional valve 34, which is then sent to the inner feed cylinder 11 and the support cylinder 13 respectively, so that the grinding head pressing force and the back support force are continuously adjusted according to the change of the workpiece position; the reference cutting current in this embodiment means the reference current value corresponding to the high-speed motor 35 during stable grinding under standard pipe diameter, standard material and target surface roughness conditions;

[0102] During the machining process, the industrial control computer continuously collects the actual cutting current and compares it with the reference cutting current. When the actual cutting current is higher than the reference value, it indicates that the actual cutting resistance in the current area is higher than the preset level. This increase may come from local hard oxide scale, material hardness fluctuations, or minor morphological changes that were not fully reflected in the previous detection cycle. The industrial control computer multiplies the current difference by the proportional gain coefficient to obtain the additional pressure reduction, and adds it to the current pressure command of the internal feed cylinder 11, so that the flap wheel grinding head 12 produces controlled micro-retraction.

[0103] The proportional gain coefficient can be determined through trial cutting calibration. Its function is to convert the current increment into a compensation amount that matches the pneumatic actuator. The online cutting logic here actually executes a transient load feedback regulation model. The purpose of this model is to handle sudden surges in cutting resistance caused by random hard points or material inhomogeneities that are not detected in the feedforward detection stage.

[0104] In terms of logical structure, the model receives the difference between the actual cutting current and the reference cutting current in real time as an abnormal load input. When the difference exceeds the allowable fluctuation range, the additional pressure reduction is calculated by the proportional gain module and superimposed as a negative feedback signal on the current command of the internal feed cylinder 11.

[0105] The physical relationship represented by this model is as follows: a sudden change in the hardness or allowance of the material in the cutting area will be instantly converted into an increase in cutting force, which is reflected as a rise in motor current. By capturing this sudden change in electrical signal, the system rapidly reduces the radial feed air pressure and uses the compressibility of gas to make the grinding head produce a quantitative radial yield corresponding to the abnormal load, thereby releasing the instantaneously accumulated cutting stress and protecting the grinding head and motor from mechanical impact damage.

[0106] By combining feedforward air pressure correction with online pressure reduction based on actual current, the grinding force of the inner wall can be maintained within a predetermined range, thereby reducing the vibration tendency and the risk of local over-grinding under long cantilever conditions, and improving the consistency of synchronous grinding of the inner and outer walls. In this embodiment, the reference cutting current is not a single theoretical value, but a reference interval center value or stable average value established by standard trial cutting before formal processing. Its physical meaning is to characterize the normal cutting load level that the inner grinding system can maintain for a long time under the conditions of target removal amount and target surface roughness.

[0107] The process of determining the reference cutting current can be performed in the following order: Select a sample oil pipe with material, wall thickness and inner diameter within the standard range; perform stable grinding under the set spindle speed, grinding head speed, basic working pressure and axial feed speed; continuously collect the current of the high-speed motor 35 in a stable machining range, and remove the start-stop section, reversing section and obvious abnormal peaks; take the average value of the remaining data as the reference cutting current.

[0108] The technical function of the proportional gain coefficient is to limit the sensitivity of the conversion of current deviation into pressure reduction. Its determination method preferentially adopts step-by-step trial-and-error calibration: while keeping other process parameters constant, several known load increase conditions are artificially introduced, and the appropriate yield pressure corresponding to the current increase is recorded. Then, the pressure reduction amplitude corresponding to a unit current difference is determined. The real-time processing flow for synchronous processing and pressure regulation can be clearly defined as follows:

[0109] Step 1: The industrial control computer determines the current rotation angle of the oil pipe based on the encoder or spindle angular position signal, and determines the current axial position based on the linear guide feed displacement signal.

[0110] Step 2: Retrieve the corresponding internal feed correction value and support correction value from the pre-established lookup table according to the angular position and axial position;

[0111] Step 3: The correction value is superimposed with the respective basic working pressure to form the feedforward pressure command generated based on the air pressure correction value at the current moment, and sent to the corresponding electro-proportional valve 34;

[0112] Step 4: Simultaneously collect the actual cutting current of the high-speed motor 35 during grinding.

[0113] Step 5: Compare the actual cutting current with the reference cutting current. When the difference between the two falls within the allowable fluctuation range, keep the current feedforward pressure command generated based on the air pressure correction value unchanged.

[0114] Step Six: When the actual cutting current exceeds the reference cutting current and exceeds the allowable fluctuation range, it is determined that the cutting load is too high. Only then will the industrial control computer activate the online reduction logic, converting the excess current difference into an additional pressure reduction amount and adding it to the current pressure command of the internal feed cylinder 11. The additional pressure reduction amount can be calculated using the formula...

[0115]

[0116] To achieve, among which, Additional pressure reduction, The proportional gain factor is used to convert the current difference into pressure reduction. This is the actual cutting current. As the reference cutting current, The amplitude of one side of the allowable current fluctuation band;

[0117] Step 7: When the actual cutting current falls back to the allowable fluctuation range, the additional pressure reduction amount gradually decreases according to the preset time constant by performing first-order inertial decay until it exits, thereby preventing mechanical structure oscillation caused by sudden changes in air pressure command, and only retaining the feedforward correction value given by the lookup table.

[0118] The purpose of the allowable fluctuation band is to avoid over-adjustment of normal small fluctuations. Its value can be preset based on the natural fluctuation range of the stable current during standard trial cutting. The control cycle of the above-mentioned online reduction logic is set to no more than 5ms, so that the data flow process from abnormal current data acquisition, logic calculation to correction signal issuance has microsecond-level response capability, providing a solid hardware and software foundation for the technical effect of instantaneous release of cutting stress. Thus, the feedforward correction is responsible for responding to detected topographic fluctuations in advance, and the online reduction is responsible for suppressing unforeseen load surges. The input sources, triggering conditions and output destinations of the two in the control flow are clearly corresponding.

[0119] This application has been described through the above embodiments; however, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit this application to the described embodiments. Those skilled in the art will understand that many more variations and modifications can be made based on the teachings of this application, and all such variations and modifications fall within the scope of protection claimed in this application.

Claims

1. A device for grinding and polishing the inner and outer walls of oil pipes, comprising: A bed base (1) is characterized in that: a spindle box (2) is fixedly connected to one end of the bed base (1), a three-jaw self-centering chuck (3) is provided at the output end of the spindle box (2), and a tailstock (4) is longitudinally slidably connected to the other end of the bed base (1). The three-jaw self-centering chuck (3) is used to clamp one end of the oil pipe, and the tip (5) of the tailstock (4) is used to support the outer wall of the other end of the oil pipe. An external grinding mechanism (6) is provided on one side of the bed base (1) parallel to the axis of the spindle box (2), and an internal grinding mechanism (7) is provided on the other side of the bed base (1) parallel to the axis of the spindle box (2). The internal grinding mechanism (7) includes an internal grinding slide (8) and a hollow cantilever rod (9). The top surface of the inner grinding slide (8) is rigidly fixed to one end of the hollow cantilever rod (9), and the other end of the hollow cantilever rod (9) extends into the oil pipe. The free end of the hollow cantilever rod (9) is provided with an inner grinding spindle (10) and an inner feed cylinder (11). The front end of the inner grinding spindle (10) is connected to a flap wheel grinding head (12). A support cylinder (13) is provided on the side of the hollow cantilever rod (9) facing away from the flap wheel grinding head (12).

2. The oil pipe inner and outer wall grinding and polishing device as described in claim 1, characterized in that: The spindle box (2) is supported by a tapered roller bearing (14) for a rotating spindle (15). The output flange (16) of the rotating spindle (15) is fixedly connected to the three-jaw self-centering chuck (3) by bolts (17). A servo motor (18) is fixedly connected above the spindle box (2). The output shaft of the servo motor (18) directly drives the rotating spindle (15) to rotate via a synchronous belt (19).

3. The oil pipe inner and outer wall grinding and polishing device as described in claim 2, characterized in that: The external grinding mechanism (6) includes a first linear guide rail (20), an external grinding slide (21), an external feed cylinder (22), and an external sander (23). The first linear guide rail (20) is fixedly connected to one side of the bed base (1) parallel to the axis of the rotating spindle (15). The external grinding slide (21) is slidably connected to the first linear guide rail (20). The external feed cylinder (22) is fixedly connected to the top surface of the external grinding slide (21) laterally. The push rod end of the external feed cylinder (22) is connected to the external sander (23) through a flange. The contact wheel (24) of the external sander (23) faces the outer wall of the oil pipe.

4. The oil pipe inner and outer wall grinding and polishing device as described in claim 3, characterized in that: The other side of the bed base (1) is fixedly connected to a second linear guide rail (25) parallel to the axis of the rotating spindle (15). The inner grinding slide (8) is slidably connected to the second linear guide rail (25). The top surface of the inner grinding slide (8) is rigidly fixed to one end of the hollow cantilever rod (9) by four high-strength bolts (26). The main body of the hollow cantilever rod (9) is a seamless steel pipe with an outer diameter of 80 mm and a wall thickness of 10 mm.

5. The oil pipe inner and outer wall grinding and polishing device as described in claim 4, characterized in that: The hollow cantilever rod (9) has a transverse groove (27) machined inside its free end. The internal grinding spindle (10) is slidably connected in the groove (27). The front end of the internal grinding spindle (10) is connected to the flap wheel grinding head (12) through a right angle gearbox (28). The internal feed cylinder (11) is fixedly connected to the rear of the groove (27). The push rod (29) of the internal feed cylinder (11) directly pushes the tail end of the internal grinding spindle (10).

6. The oil pipe inner and outer wall grinding and polishing device as described in claim 5, characterized in that: The hollow cantilever rod (9) has a radial through hole (30) on the side facing away from the flap wheel grinding head (12). The support cylinder (13) is fixedly installed in the radial through hole (30). The piston rod (31) of the support cylinder (13) extends toward the inner wall of the oil pipe. The end of the piston rod (31) of the support cylinder (13) is hinged to a polyurethane support wheel (33) through a pin (32). The polyurethane support wheel (33) fits against the inner wall of the oil pipe.

7. The oil pipe inner and outer wall grinding and polishing device as described in claim 6, characterized in that: An electric proportional valve (34) is connected in series on the air intake circuit of the external feed cylinder (22), the internal feed cylinder (11) and the support cylinder (13). The internal grinding spindle (10) is driven by a high-speed motor (35) built into the hollow cantilever rod (9) through a flexible coupling (36).

8. The oil pipe inner and outer wall grinding and polishing device as described in claim 7, characterized in that: The device also includes an industrial control computer and a spindle angle encoder. The industrial control computer is configured to perform current-based inner wall undulation detection. During the detection phase, the servo motor (18) drives the three-jaw self-centering chuck (3) to rotate the oil pipe at a set detection speed of 10 r / min. The inner grinding slide (8) drives the hollow cantilever rod (9) into the oil pipe. The electric proportional valve (34) of the support cylinder (13) outputs a set constant air pressure to drive the polyurethane support wheel (33) to press against the inner wall of the oil pipe. The internal feed cylinder (11) does not output pressure, the high-speed motor (35) starts and maintains no-load speed, the industrial control computer obtains the current fluctuation parameters of the high-speed motor (35) in real time in conjunction with the signal of the spindle angle encoder, and obtains the radial deviation distribution of the pipe wall according to the current fluctuation parameters.

9. The oil pipe inner and outer wall grinding and polishing device as described in claim 8, characterized in that: The industrial control computer is also configured to perform air pressure correction value calculation, and based on the detected radial deviation distribution, generate in advance the air pressure correction value for the next processing cycle corresponding to different pipe wall undulation regions.

10. The oil pipe inner and outer wall grinding and polishing device as described in claim 9, characterized in that: The industrial control computer is also configured to perform synchronous processing and pressure regulation. During the synchronous processing stage, the servo motor (18) increases the oil pipe speed to the normal processing speed of 300r / min. The outer grinding slide (21) and the inner grinding slide (8) are synchronously fed along the linear guide axial direction. The outer feed cylinder (22) outputs constant pressure. The industrial control computer calls the air pressure correction value in real time and converts it into a control signal to send to the electric proportional valve (34) according to the current axial position of the hollow cantilever rod (9) and the rotation angle of the oil pipe. It dynamically adjusts the pressure of the inner feed cylinder (11) and the support cylinder (13) and continuously monitors the actual cutting current of the high-speed motor (35) during the processing. If the difference between the actual cutting current and the reference cutting current exceeds the preset allowable fluctuation threshold, the industrial control computer dynamically reduces the feedforward pressure command of the internal feed cylinder (11) according to the difference; if the difference does not exceed the allowable fluctuation threshold, the feedforward pressure command generated by the current internal feed cylinder (11) based on the air pressure correction value remains unchanged.

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