Workpiece top holding force automatic adjustment method

Abstract

The application discloses a workpiece top holding force automatic adjustment method and relates to the technical field of mechanical manufacturing. L Data preparation: calculating the top holding force F L ; tailstock position adjustment: through the numerical control system, the servo motor is powered on to drive the tailstock to move forward to the target grinding station; feeding: through the mechanical arm, the workpiece to be processed is placed above the station; centering: through the servo hydraulic drive mechanism, the tailstock center is driven into the tailstock hole of the workpiece; grinding: the headstock drives the workpiece to grind through the workpiece automatic driving device, and the top holding force F L is adjusted according to different grinding positions of the workpiece; and discharging. The application can automatically adjust the top holding force of the workpiece and can adapt to different sizes and weight specifications and different machining precision requirements.

Description

Technical Field

[0001] This invention relates to the field of mechanical manufacturing technology, and specifically to a method for automatically adjusting the holding force of a workpiece. Background Technology

[0002] The headstock and tailstock are crucial functional components in cylindrical grinding machines, providing support and centering for the workpiece. During grinding, the headstock drives the workpiece to rotate, while the tailstock, relying on a simple mechanical structure, drives the center to extend and hold the workpiece, thus completing the centering action of the headstock and tailstock centers. There are two main structural types for the internal drive of the tailstock center to extend and retract: one type uses a lever to compress an internal spring, causing the tailstock center to retract. After the workpiece is lifted into position, the lever is released, and the spring forces the tailstock center to hold the workpiece end face in the center hole with a certain pressure; the other type uses a hydraulic cylinder to achieve the extension and retraction of the tailstock. When grinding shaft-type parts, the holding force affects the grinding quality. Excessive holding force causes elastic deformation of the workpiece, affecting machining accuracy due to springback; insufficient holding force results in insufficient contact rigidity between the tailstock center and the workpiece center hole, causing the workpiece to easily form a cone shape, and in severe cases, the workpiece may even fall, leading to a safety accident.

[0003] Modern automated production places higher demands on grinding machines, requiring greater efficiency and flexibility. To adapt to this automated machining, it is necessary to adjust the holding force in automated grinding of shaft parts to facilitate precision grinding of shaft parts with different sizes, weights, and machining accuracy requirements. Summary of the Invention

[0004] The main objective of this invention is to provide an automatic adjustment method for the holding force of workpieces of different sizes, weights, and processing precision requirements by detecting the holding force through a sensor and adjusting the holding force through hydraulic control, thereby solving the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for automatically adjusting the holding force of a workpiece includes the following steps:

[0007] S1. Recognition and Matching: Obtain relevant information about the workpiece to be processed through a machine vision system;

[0008] S2. Data Preparation: Calculate the bearing force F L And obtain the distance S from which the spring inside the tailstock extends forward from the position of maximum holding force. L ;

[0009] S3: Tailstock position adjustment: The servo motor is powered on by the CNC system to drive the tailstock forward to the target grinding station;

[0010] S4: Loading: The workpiece to be processed is placed above the workstation by a robotic arm.

[0011] S5: Centering: The tailstock tip moves backward using a servo hydraulic drive mechanism. After the workpiece is in place, the tailstock tip pushes into the tip hole of the workpiece.

[0012] S6: Grinding: The headstock drives the workpiece to perform grinding via an automatic workpiece drive device, and adjusts the holding force F according to the different grinding areas of the workpiece. L ;

[0013] S7: Unloading: After grinding is completed, the center of the tailstock retracts under the pull-back action of the servo hydraulic drive mechanism, and the workpiece is unloaded by the robot arm.

[0014] Furthermore, the relevant information about the workpiece to be processed in step S1 includes the workpiece length L, the workpiece geometric parameters after the previous process, the workpiece material, hardness, weight, and surface quality physicochemical parameters. When the workpiece length L satisfies: L min ≤L≤L max The subsequent automated workpiece holding grinding cycle is executed, where L max When selecting a spring for the tailstock design, the maximum length of the workpiece that can be supported by the maximum holding force is determined by the maximum spring force and the tailstock position adjustment limit position. min When designing the tailstock spring, the minimum length of the workpiece that can be supported by the minimum holding force should be selected.

[0015] Furthermore, F in step S2 L Satisfy F min ≤F L ≤F max , of which F L The required holding force F is the force required to be applied to the tip of the tailstock. min The minimum holding force F selected for the workpiece to be processed. max The maximum holding force selected for the workpiece to be processed; based on the spring stiffness curve, the required holding force F from the tailstock's center point. L F can be obtained L and F max The distance between them, that is, the distance S that the spring needs to extend forward from the position of maximum holding force. L .

[0016] Furthermore, in step S3, when the tailstock is at position R on the right end of the worktable, the moving distance ΔH is calculated, where ΔH = L. max -LS L At this point, the workpiece to be processed is clamped.

[0017] Furthermore, the tailstock includes a tailstock housing, and the tailstock housing is provided with a workpiece supporting mechanism and a servo hydraulic drive mechanism.

[0018] Furthermore, the workpiece holding mechanism includes a sleeve, a center, a pressure sensor, a washer, a spring, a rear cover, a first nut, a threaded seat, and a threaded sleeve; the front end of the tailstock housing has a spindle hole that slides with the sleeve; the front end of the sleeve has a tapered hole for mounting the center, and the rear end of the sleeve has a countersunk hole in which the pressure sensor, washer, and spring are sequentially installed; the rear end face of the tailstock housing is fitted with a rear cover by screws; the rear cover has a through hole at a coaxial position relative to the sleeve for mounting the threaded seat; the front end of the threaded seat has an external thread for mounting the first nut, and the threaded seat is fixed to the side wall of the rear cover by the first nut; the rear end of the threaded seat has a thread that movably connects with the threaded sleeve; the front end of the threaded sleeve has a countersunk hole for axial positioning of the spring;

[0019] By rotating the threaded sleeve, the spring is brought to a pre-compressed state; under the action of the spring pre-compressed force, the spring force F1 transmitted from the spring to the sleeve is measured by the pressure sensor between the sleeve and the gasket.

[0020] Furthermore, the servo hydraulic drive mechanism includes a hydraulic cylinder, a flange joint, a tension / compression sensor, a shift fork plate, a guide rod, a linear bearing, and a connecting plate; the cylinder body of the hydraulic cylinder is fixedly connected to the rear side plate of the rear cover; the connecting plate is fixedly connected to the rear end side of the sleeve; one end of the shift fork plate is provided with an arc-shaped groove, which abuts against the rear end of the sleeve and is fixedly connected to the side of the connecting plate; the other end of the shift fork plate is provided with a through hole for positioning and installing the flange joint at one end of the guide rod; the other end of the guide rod is supported in a hole provided in the tailstock housing by a linear bearing; the tension / compression sensor and the flange joint are sequentially installed on the other side of the shift fork plate where the guide rod is installed, and then it is threadedly connected to the piston rod of the hydraulic cylinder.

[0021] The hydraulic cylinder is externally connected to a three-position four-way solenoid valve and a servo proportional valve. The magnitude of the hydraulic force F2 is controlled by the servo proportional valve. The extension and retraction of the piston rod of the hydraulic cylinder are controlled by the three-position four-way solenoid valve. The hydraulic force F2 applied by the hydraulic cylinder to the shift fork plate is measured by a tension / compression sensor.

[0022] Furthermore, in step S6, the holding force F is calculated based on the magnitude and direction of the grinding force. L Then, based on F2 = F L The relationship between F1 and F2 is used to calculate the control quantity of the servo proportional valve, and then the hydraulic force F2 of the hydraulic cylinder is adjusted through a three-position four-way solenoid valve so that F1 and F2 satisfy F L Requirements.

[0023] Furthermore, in step S6, the holding force F is adjusted according to the grinding requirements of rough grinding, semi-finish grinding, and finish grinding of the workpiece. L Because the grinding requirements for rough grinding, semi-finish grinding, and finish grinding are different, the required holding force F varies. L It will also be different, depending on F LThe relationship between F2 and F1 is calculated to determine the control quantity of the servo proportional valve. The direction and magnitude of the hydraulic force F2 in the hydraulic cylinder are adjusted via a three-position four-way solenoid valve, ensuring that F1 and F2 satisfy the condition F... L Requirements.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] By configuring a pressure sensor to measure the force exerted by the spring on the tailstock sleeve, configuring a tension / compression sensor to measure the hydraulic force exerted by the hydraulic cylinder piston rod on the tailstock sleeve, and configuring a three-position four-way solenoid valve and a servo proportional valve to adjust the hydraulic force exerted by the hydraulic cylinder piston rod, the relationship between the magnitudes of the forces measured by the pressure sensor and the tension / compression sensor is changed, thereby realizing the automatic adjustment of the workpiece holding force. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the workpiece holding drive system used in the automatic adjustment method for workpiece holding force of the present invention.

[0027] Figure 2 This is a front view of the tailstock of the present invention.

[0028] Figure 3 This is a side view of the tailstock of the present invention.

[0029] Figure 4 This is a force-displacement adjustment diagram of the preload spring in the tailstock of the present invention.

[0030] Figure 5 This is a schematic diagram of the tailstock adjustment according to the present invention.

[0031] Among them, 11. Tailstock housing; 12. Rear cover; 13. First nut; 14. Threaded seat; 15. Threaded sleeve; 16. Top rod; 17. Tailstock displacement gauge; 18. Secondary slider; 19. Secondary guide rail; 20. Sleeve; 21. Center; 22. Pressure sensor; 23. Gasket; 24. Spring; 25. Hydraulic cylinder; 26. Flange joint; 27. Tension and compression sensor; 28. Shift fork plate; 29. ​​Guide rod; 30. Linear bearing; 40. Worktable; 41. Headstock; 42. Workpiece driving device; 43. Workpiece; 44. Tailstock; 45. Three-position four-way solenoid valve; 46. Servo proportional valve; 48. Guide rail positioning boss; 49. Rack positioning boss; 50. Slider positioning boss. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] like Figure 1As shown, the workpiece holding drive system applied to the automatic workpiece holding force adjustment method of the present invention includes a headstock 41, a workpiece driving device 42, and a tailstock 44. The headstock 41 is mounted above the worktable 40 relative to the tailstock 44, providing power to drive the workpiece 43; one end of the workpiece driving device 42 is mounted on the headstock 41, and the other end can hold the workpiece 43; an automatic positioning mechanism is provided below the tailstock 44, and the two extreme positions of the tailstock 44 relative to the headstock 41 are the front position O and the rear position R, and the distance between the front position O and the rear position R is H; a batch of workpieces 43 to be processed with different shaft diameters D1 and D2 and different lengths L can be placed on the workstation between the headstock 41 and the tailstock 44.

[0034] like Figure 2 As shown, the tailstock 44 has a center point 21 at its front end. The tailstock 44 includes a tailstock shell 11, and the tailstock shell 11 has a workpiece holding mechanism and a servo hydraulic drive mechanism inside.

[0035] In this embodiment, the workpiece holding mechanism includes a sleeve 20, a center 21, a pressure sensor 22, a washer 23, a spring 24, a rear cover 12, a first nut 13, a threaded seat 14, and a threaded sleeve 15. The front end of the tailstock housing 11 has a spindle hole that slides through the sleeve 20. The front end of the sleeve 20 has a tapered hole for mounting the center 21, and the rear end of the sleeve 20 has a countersunk hole in which the pressure sensor 22, the washer 23, and the spring 24 are sequentially installed. The rear end face of the tailstock housing 11 is fitted with a rear cover 12 by screws. The rear cover 12 has a through hole at a coaxial position relative to the sleeve 20 for mounting the threaded seat 14. The front end of the threaded seat 14 has an external thread for mounting the first nut 13, which fixes the threaded seat 14 to the side wall of the rear cover 12. The rear end of the threaded seat 14 has a thread that is movably connected to the threaded sleeve 15. The front end of the threaded sleeve 15 has a countersunk hole for axially positioning the spring 24. During operation, the spring 24 is pre-compressed by rotating the threaded sleeve 15; under the action of the pre-compression of the spring 24, the spring force F1 transmitted from the spring 24 to the sleeve 20 is measured by the pressure sensor 22 between the sleeve 20 and the gasket 23.

[0036] In this embodiment, the servo hydraulic drive mechanism includes a hydraulic cylinder 25, a flange joint 26, a tension / compression sensor 27, a shift fork plate 28, a guide rod 29, a linear bearing 30, and a connecting plate 31. The cylinder body of the hydraulic cylinder 25 is fixed to the rear of the side plate of the rear cover 12 by screws. The connecting plate 31 is fixed to the rear end side of the sleeve 20 by screws. One end of the shift fork plate 28 is provided with an arc-shaped groove of the same size as the outer diameter of the sleeve 20. The arc-shaped groove abuts against the rear end of the sleeve 20 and is fixed to the side of the connecting plate 31 by screws. The other end of the shift fork plate 28 is provided with a through hole for positioning and installing the flange joint 26 at one end of the guide rod 29. The other end of the guide rod 29 is supported in a hole provided in the tailstock housing 11 by the linear bearing 30. The tension / compression sensor 27 and the flange joint 26 are sequentially installed on the other side of the shift fork plate 28 where the guide rod 29 is installed, and then the piston rod of the hydraulic cylinder 25 is threadedly connected to it. The hydraulic force F2 applied by the hydraulic cylinder 25 to the shift fork 28 is measured by the tension / compression sensor 27. The hydraulic cylinder 25 is externally connected to a three-position four-way solenoid valve 45 and a servo proportional valve 46. The magnitude of the hydraulic force F2 is controlled by the servo proportional valve 46, and the extension and retraction of the piston rod of the hydraulic cylinder 25 are controlled by the three-position four-way solenoid valve 45. When the hydraulic force F2 is opposite to the spring force F1, the holding force applied to the workpiece through the sleeve 20 and the center 21 can be reduced; when the hydraulic force F2 is the same as the spring force F1, the holding force applied to the workpiece through the sleeve 20 and the center 21 can be increased.

[0037] With the machine tool powered off, the tailstock 44 is in the forward position (O). Under the action of the internal spring 24, the tip 21 of the tailstock extends outward to the limit position determined by S. At this time, the shortest length of workpiece that can be supported is L. min The minimum bearing force is F min When the tailstock 44 is in the rear position (R), the sleeve 20 is compressed by the piston rod of the hydraulic cylinder 25, reaching the limit position determined by S. At this point, the maximum length of the workpiece that can be supported is L. max The maximum bearing force is F max ;F max It is the maximum spring force selected during spring design. If the hydraulic cylinder 25 does not participate in the adjustment of the supporting force, it is also the maximum supporting force of the workpiece provided by the spring 24 through the sleeve 20 and the center 21.

[0038] A pressure sensor 22 is installed on the rear side of the sleeve 20 to measure the spring force F1 exerted by the spring 24 behind the pressure sensor 22 on the sleeve 20. A tension / compression sensor 27 is installed at the front end of the piston rod of the hydraulic cylinder 25 to measure the hydraulic force F2 exerted by the piston rod of the hydraulic cylinder 25 on the sleeve 20. The hydraulic cylinder 25 is externally connected to a three-position four-way solenoid valve 45 and a servo proportional valve 46. The three-position four-way solenoid valve 45 controls the extension and retraction of the piston rod of the hydraulic cylinder 25, and the servo proportional valve 46 controls the oil supply pressure of the hydraulic cylinder 25, thereby changing the magnitude of the hydraulic force F2.

[0039] In another embodiment, the servo hydraulic drive mechanism further includes a push rod 16, which is installed in a threaded hole located at the center of the sleeve 20. The rear end of the push rod 16 is exposed after passing through a through hole in the threaded sleeve 15. By rotating the push rod 16, the push rod 16 can be moved forward to disengage the tip 21 from the tapered hole of the sleeve 20.

[0040] like Figure 3 As shown, an automatic positioning mechanism is provided below the tailstock 44. The automatic positioning mechanism includes a linear guide support device, a transmission drive device, and a displacement detection device. The linear guide support device includes a base 1, a guide rail, and a slider. The base 1 is slidably disposed on the top surface of the worktable 40. The guide rail is disposed on the base 1. The slider is disposed on the bottom surface of the tailstock 44 and is slidably connected to the guide rail. The transmission drive device is used to drive the tailstock 44 to slide along the axial direction of the guide rail. The displacement detection device is used to detect the sliding displacement information of the tailstock 44.

[0041] Preferably, the guide rail includes a main guide rail 4 and a secondary guide rail 19, and the slider includes a main slider 3 and a secondary slider 18; the top surface of the base 1 is provided with a guide rail positioning boss 48 that is consistent with the movement direction of the worktable 40, the main guide rail 4 is installed on the side of the guide rail positioning boss 48 by screws, the bottom surface of the tailstock 44 is provided with a slider positioning boss 50, and the main slider 3 is installed on the side of the slider positioning boss 50 by screws; the secondary guide rail 19 is disposed on the top surface of the base 1 and is parallel to the main guide rail 4, and the secondary slider 18 is disposed on the bottom surface of the tailstock 44.

[0042] In this embodiment, the slider positioning boss 50 and the auxiliary slider 18 are both disposed on the bottom surface of the tailstock housing 11; the bottom surface of the base 1 is slidably connected to the top surface of the worktable 40 and fixed above the worktable 40 by the side pressure plate. When the base needs to be moved, the side pressure plate can be loosened to push the base to slide on the worktable; during normal operation, the base 1 and the worktable 40 are locked so that the tailstock housing 11 can slide along the main guide rail 4 on the base 1.

[0043] Preferably, the transmission drive device includes a drive base 5, which is mounted on the side of the tailstock 44. A servo motor 7 is mounted on the top of the drive base 5. The output end of the servo motor 7 is connected to a worm shaft 6. The worm shaft 6 passes through the top wall of the drive base 5 and meshes with a worm wheel inside the drive base 5. The worm wheel shaft 8 on the worm wheel passes through the side wall of the drive base 5 and is connected to a gear 9. The gear 9 meshes with a rack 2. A rack positioning boss 49 is provided on the top surface of the base 1, which is aligned with the movement direction of the worktable 40. The rack 2 is mounted on the side of the rack positioning boss 49 by screws.

[0044] In this embodiment, the upper and lower side walls of the tailstock housing 11 are provided with first bearing seats for mounting the worm shaft 6, and the left and right side walls are provided with second bearing seats for mounting the worm wheel shaft 8. During operation, the servo motor 7 drives the worm shaft 6 to rotate. Through the transmission of the worm wheel and the worm wheel shaft 8, the gear 9 rotates. The meshing of the gear 9 and the rack 2 drives the tailstock housing 11 to slide along the axial direction of the main guide rail 4.

[0045] Preferably, the displacement detection device includes a tailstock displacement probe 10 and a tailstock displacement gauge 17. The tailstock displacement probe 10 is mounted on the tailstock 44, and the tailstock displacement gauge 17 is mounted on the base 1. The tailstock displacement gauge 17 is parallel to the main guide rail 4.

[0046] In this embodiment, both the tailstock displacement probe 10 and the tailstock displacement measuring scale 17 are electrically connected to the CNC system of the grinding machine. The CNC system can control the servo motor 7 to be powered on. Subsequently, the rotational motion of the motor shaft drives the tailstock housing 11 to slide along the axial direction of the main guide rail 4 through the meshing of the worm shaft 6 and the worm wheel shaft 8. At this time, the magnitude of the sliding displacement information is measured by the relative displacement between the tailstock displacement probe 10 and the tailstock displacement measuring scale 17. This sliding displacement information is transmitted to the CNC system to form a closed-loop feedback control.

[0047] In this embodiment, the workpiece driving device 42 is a self-centering chuck, and three jaws are evenly arranged on the self-centering chuck.

[0048] like Figure 4 As shown, the minimum holding force F obtained based on the workpiece characteristics min and maximum holding force F max The spring deformation is S, and the required holding force is F. L At that time, the magnitude of the spring rebound deformation can be obtained from the spring stiffness curve shown in the figure as S. L That is, the distance that the sleeve 20 extends outward.

[0049] like Figure 5As shown, the automatic adjustment method for the workpiece holding force during the grinding process is carried out according to the following steps:

[0050] S1. Recognition and Matching: Obtain relevant information about the workpiece to be processed through a machine vision system;

[0051] S2. Data Preparation: Calculate the bearing force F L And obtain the distance S by which the spring 24 inside the tailstock 44 extends forward from the position of maximum holding force. L ;

[0052] S3: Tailstock 44 position adjustment: The servo motor is powered on by the CNC system, driving the tailstock to move forward to the target grinding position;

[0053] S4: Loading: The workpiece to be processed is placed above the workstation by a robotic arm.

[0054] S5: Centering: The tailstock tip moves backward using a servo hydraulic drive mechanism. After the workpiece is in place, the tailstock tip pushes into the tip hole of the workpiece.

[0055] S6: Grinding: The headstock drives the workpiece to perform grinding via an automatic workpiece drive device, and adjusts the holding force F according to the different grinding areas of the workpiece. L ;

[0056] S7: Unloading: After grinding is completed, the center of the tailstock retracts under the pull-back action of the servo hydraulic drive mechanism, and the workpiece is unloaded by the robot arm.

[0057] In this embodiment, the relevant information of the workpiece to be processed in step S1 includes the workpiece length L, the workpiece geometric parameters after the previous process, the workpiece material, hardness, weight, and surface quality physicochemical parameters. When the workpiece length L satisfies: L min ≤L≤L max The subsequent automated workpiece holding grinding cycle is executed, where L max When selecting a spring for the tailstock design, the maximum length of the workpiece that can be supported by the maximum holding force is determined by the maximum spring force and the tailstock position adjustment limit position. min When designing the tailstock spring, the minimum length of the workpiece that can be supported by the minimum holding force should be selected.

[0058] In this embodiment, F in step S2 L Satisfy F min ≤F L ≤F max , of which F L The required holding force F is the force required to be applied to the tip of the tailstock. min The minimum holding force F selected for the workpiece to be processed. max The maximum holding force selected for the workpiece to be processed; based on the spring stiffness curve, the required holding force F from the tailstock's center point.L F can be obtained L and F max The distance between them, that is, the distance S that the spring needs to extend forward from the position of maximum holding force. L .

[0059] In this embodiment, in step S3, when the tailstock is at position R on the right end of the worktable, the moving distance ΔH is calculated, where ΔH = L. max -LS L At this point, the workpiece to be processed is clamped.

[0060] In this embodiment, in step S6, the holding force F is calculated based on the magnitude and direction of the grinding force. L Then, based on F2 = F L - The relationship between F1 and F2 is used to calculate the control quantity of the servo proportional valve, and then the output force F2 of the hydraulic cylinder is adjusted through a three-position four-way solenoid valve so that F1 and F2 satisfy F L Requirements.

[0061] In this embodiment, in step S6, the holding force F is changed according to the grinding requirements of rough grinding, semi-fine grinding, and fine grinding of the workpiece. L Because the grinding requirements for rough grinding, semi-finish grinding, and finish grinding are different, the required holding force F varies. L It will also be different, depending on F L The relationship between F2 and F1 is calculated to determine the control quantity of the servo proportional valve. The direction and magnitude of the hydraulic force F2 in the hydraulic cylinder are adjusted via a three-position four-way solenoid valve, ensuring that F1 and F2 satisfy the condition F... L Requirements.

[0062] Based on the identification of workpiece characteristics, this invention adjusts the position of the tailstock on the worktable through an automatic positioning mechanism to meet the rough grinding, semi-fine grinding, and fine grinding of workpieces of different lengths. By using pressure and tension / compression sensors installed in the tailstock, the holding force is adjusted in accordance with the different shaft diameters of the workpieces and the grinding force requirements of the corresponding grinding processes, thereby achieving better grinding processability and improving grinding efficiency and quality.

[0063] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for automatically adjusting the holding force of a workpiece, characterized in that, Includes the following steps: S1. Recognition and Matching: Obtain relevant information about the workpiece to be processed through a machine vision system; S2. Data Preparation: Calculate the bearing force F L And obtain the distance S from which the spring inside the tailstock extends forward from the position of maximum holding force. L ; S3: Tailstock position adjustment: The servo motor is powered on by the CNC system to drive the tailstock forward to the target grinding station; S4: Loading: The workpiece to be processed is placed above the workstation by a robotic arm. S5: Centering: The tailstock tip moves backward using a servo hydraulic drive mechanism. After the workpiece is in place, the tailstock tip pushes into the tip hole of the workpiece. S6: Grinding: The headstock drives the workpiece to perform grinding via an automatic workpiece drive device, and adjusts the holding force F according to the different grinding areas of the workpiece. L ; S7: Unloading: After grinding is completed, the tailstock center retracts under the pull-back action of the servo hydraulic drive mechanism, and the workpiece is unloaded by the robot arm after being released. The tailstock includes a tailstock housing, and the tailstock housing is provided with a workpiece holding mechanism and a servo hydraulic drive mechanism. The workpiece holding mechanism includes a sleeve, a center, a pressure sensor, a washer, a spring, a rear cover, a first nut, a threaded seat, and a threaded sleeve. The front end of the tailstock housing has a spindle hole that slides through the sleeve. The front end of the sleeve has a tapered hole for mounting the center, and the rear end of the sleeve has a countersunk hole in which the pressure sensor, washer, and spring are sequentially installed. The rear end face of the tailstock housing is fitted with a rear cover by screws. The rear cover has a through hole at a coaxial position relative to the sleeve for mounting the threaded seat. The front end of the threaded seat has an external thread for mounting the first nut, which fixes the threaded seat to the side wall of the rear cover. The rear end of the threaded seat has an internal thread that movably connects with the threaded sleeve. The front end of the threaded sleeve has a countersunk hole for axial positioning of the spring. By rotating the threaded sleeve, the spring is brought to a preloaded state; under the action of the spring preload, the spring force F1 transmitted from the spring to the sleeve is measured by the pressure sensor between the sleeve and the gasket; The servo hydraulic drive mechanism includes a hydraulic cylinder, a flange joint, a tension / compression sensor, a shift fork plate, a guide rod, a linear bearing, and a connecting plate. The cylinder body of the hydraulic cylinder is fixedly connected to the rear side plate of the rear cover. The connecting plate is fixedly connected to the rear side of the sleeve. One end of the shift fork plate has an arc-shaped groove, which abuts against the rear end of the sleeve and is fixedly connected to the side of the connecting plate. The other end of the shift fork plate has a through hole for positioning and installing the flange joint at one end of the guide rod. The other end of the guide rod is supported in a hole in the tailstock housing by a linear bearing. The tension / compression sensor and the flange joint are sequentially installed on the other side of the shift fork plate where the guide rod is installed, and then the piston rod of the hydraulic cylinder is threadedly connected to it. The hydraulic cylinder is externally connected to a three-position four-way solenoid valve and a servo proportional valve. The magnitude of the hydraulic force F2 is controlled by the servo proportional valve. The extension and retraction of the piston rod of the hydraulic cylinder are controlled by the three-position four-way solenoid valve. The hydraulic force F2 applied by the hydraulic cylinder to the shift fork plate is measured by the tension and pressure sensor. An automatic positioning mechanism is provided below the tailstock. The automatic positioning mechanism includes a linear guide support device, a transmission drive device, and a displacement detection device. The linear guide support device includes a base, a guide rail, and a slider. The base is slidably disposed on the top surface of the worktable, the guide rail is disposed on the base, and the slider is disposed on the bottom surface of the tailstock. The slider is slidably connected to the guide rail. The transmission drive device is used to drive the tailstock to slide along the axial direction of the guide rail, and the displacement detection device is used to detect the sliding displacement information of the tailstock.

2. The method for automatically adjusting the workpiece holding force as described in claim 1, characterized in that, In step S1, the relevant information about the workpiece to be processed includes the workpiece length L, the workpiece geometry parameters after the previous process, the workpiece material, hardness, weight, and surface quality physicochemical parameters. When the workpiece length L satisfies: L min ≤L≤L max The subsequent automated workpiece holding grinding cycle is executed, where L min L is the minimum length of the workpiece that can be supported, given by the minimum supporting force when designing the tailstock. max The maximum length of the workpiece that can be supported is given by the maximum top holding force when designing the tailstock.

3. The method for automatically adjusting the workpiece holding force as described in claim 1, characterized in that, F in step S2 L Satisfy F min ≤F L ≤F max , of which F L The required holding force F is the force required to be applied to the tip of the tailstock. min The minimum holding force F selected for the workpiece to be processed. max The maximum holding force selected for the workpiece to be processed; based on the spring stiffness curve, the required holding force F from the tailstock's center point. L F can be obtained L and F max The distance between them, that is, the distance S that the spring needs to extend forward from the position of maximum holding force. L .

4. The method for automatically adjusting the workpiece holding force as described in claim 2, characterized in that, In step S3, when the tailstock is at position R on the right end of the worktable, the moving distance ΔH is calculated, where ΔH = L. max -LS L At this point, the workpiece to be processed is clamped.

5. The method for automatically adjusting the workpiece holding force as described in claim 1, characterized in that, In step S6, the holding force F is calculated based on the magnitude and direction of the grinding force. L Then, based on F2 = F L The relationship between -F1 and the control quantity of the servo proportional valve is calculated, and then the hydraulic force F2 of the hydraulic cylinder is adjusted through the three-position four-way solenoid valve, so that F L And F2 satisfies F L Requirements.

6. The method for automatically adjusting the workpiece holding force as described in claim 1, characterized in that, In step S6, the holding force F is adjusted according to the grinding requirements of rough grinding, semi-finish grinding, and finish grinding of the workpiece. L Because the grinding requirements for rough grinding, semi-finish grinding, and finish grinding are different, the required holding force F varies. L It will also be different, depending on F L The relationship between F2 and F1 is calculated to determine the control quantity of the servo proportional valve. The direction and magnitude of the hydraulic force F2 in the hydraulic cylinder are adjusted via a three-position four-way solenoid valve, ensuring that F1 and F2 satisfy the condition F... L Requirements.

Images