Reciprocating type center piece pneumatic clamp and cutter avoiding method

Abstract

The invention discloses a reciprocating type center piece pneumatic clamp and a tool avoiding method. The two end faces of the main supporting column are fixedly connected with the lower surface of the upper supporting plate and the upper surface of the lower supporting plate correspondingly to form a supporting body of the pneumatic clamp. The magnetic coupling rodless cylinders are evenly distributed on the upper surface of the lower supporting plate, the linear cylinders are installed on the upper surfaces of the magnetic coupling rodless cylinders respectively, cylinder piston rods of the linear cylinders penetrate through guide grooves in the upper supporting plate, and the upper ends of the linear cylinders are fixedly connected with the lower end face of the pressing plate. A force sensor is arranged between the upper end face of a piston rod of each air cylinder and the lower surface of the pressing plate. The outer end of the limiting groove in the pressing plate is clamped with a pin column on the upper end face of the limiting column. The vibration characteristic of the central part during machining can be monitored in real time, the clamping force is dynamically adjusted by adjusting the air inflow, it is ensured that the clamping force of the pressing plate on the central part is balanced, and deformation caused by too large local stress is avoided; high-precision automatic clamping of the helicopter propeller central part and dynamic cutter avoiding in the machining process can be achieved.

Description

Technical Field

[0001] This application relates to the field of machining tooling technology, specifically a central fixture for helicopter propellers. Background Technology

[0002] As a core component of the aircraft's transmission system, the central component is typically made of high-strength alloys or composite materials. Its complex structure includes high-precision holes, curved surfaces, and assembly interfaces, requiring strict adherence to dynamic balance, fatigue strength, and dimensional tolerance requirements. Currently, when machining central components, the outer surface is usually clamped first to machine the internal weight-reduction structure; after the weight-reduction structure is completed, the inner surface of the central component is clamped to complete the outer surface machining. The machining of the outer surface of the central component involves numerous steps and requires multiple disassemblies and adjustments, severely impacting machining accuracy and efficiency. Therefore, a central component fixture is needed to assist in the machining of central components.

[0003] In the invention with patent number CN202111599338.X, a tooling fixture for a rotor center component is proposed. This tooling fixture uses V-shaped clamping blocks to clamp the center component, which is easy to disassemble and effectively saves the number of tooling fixtures. However, when machining the outer shape of the center component, there is a problem of interference between the tool and the fixture, which requires the center component to be re-clamped.

[0004] In the invention with patent number CN202123171784.9, a central part turning fixture is proposed. By setting scale lines on the upper and lower surfaces of the screw and manually adjusting the clamping force, the clamping force at multiple points is consistent, which improves the stability of the fixture. However, this fixture cannot avoid the problem of tool and fixture interference when machining the outer surface of the central part. Summary of the Invention

[0005] To overcome the problems of low clamping efficiency and insufficient positioning accuracy of traditional fixtures in the semi-finishing process of central parts, this invention proposes a reciprocating pneumatic fixture for central parts and a tool avoidance method.

[0006] The reciprocating central component pneumatic clamp proposed in this invention includes a support plate, 6 limiting posts, 6 upper support posts, a main support post, and 6 clamping mechanisms. The support plate is divided into an upper support plate and a lower support plate. Each clamping mechanism includes a linear cylinder, a magnetically coupled rodless cylinder, a pressure plate, 6 force sensors, and 1 triaxial acceleration sensor.

[0007] The two end faces of the main support column are fixedly connected to the lower surface of the upper support plate and the upper surface of the lower support plate, respectively, to form the support body of the pneumatic clamp.

[0008] The magnetically coupled rodless cylinders in the six clamping mechanisms are evenly distributed on the upper surface of the lower support plate in the support body, and a linear cylinder is installed on the upper surface of each magnetically coupled rodless cylinder. The piston rod of the linear cylinder passes through the guide groove on the upper support plate, and its upper end is fixedly connected to the lower end face of the pressure plate; a force sensor is respectively located between the upper end face of the piston rod of each cylinder and the lower surface of the pressure plate.

[0009] Each upper support column is fixed to the inner side of the guide groove;

[0010] The six limiting posts are fixed to the upper surface of the upper support plate, located at the edge of the upper support plate, and are in the same radial direction as the guide groove;

[0011] The outer end of the upper limit groove of the pressure plate is engaged with the pin on the upper end face of the limit post.

[0012] Six force sensors are fixed to the lower surface of each pressure plate. The triaxial accelerometer is embedded and fixed to the outer circumferential surface of the upper support plate.

[0013] The lower support plate has six mounting slots for magnetically coupled rodless cylinders evenly distributed along its outer edge. Between each mounting slot is a U-shaped groove for fixing to the vertical milling machine.

[0014] The upper support plate has a central mounting hole for the central component, and an annular boss at the upper end of the mounting hole; this annular boss serves as the mounting base for the central component. Guide grooves are evenly distributed around the circumference of the surface of the upper support plate.

[0015] Upper support columns are fixed on the inner side of the guide groove; limit columns are fixed on the outer side of the guide groove, and the center of the upper support column, the central axis of the guide groove and the center of the limit column are located on the same radial line of the upper support plate.

[0016] The upper support column has two symmetrical planes cut on its circumferential surface for attaching strain gauges.

[0017] The upper end face of the limiting post has a circular pin; the end face formed by the diameter difference between the pin and the limiting post is a horizontal support surface, which is used to support the pressure plate and ensure that the pressure plate is always in a horizontal state when the linear cylinder drives the pressure plate to press down; the circumferential surface of the pin is a vertical guide surface, which is the outer circumferential surface of the pin, and is used to guide the movement of the pressure plate in the vertical direction.

[0018] The pressure plate has a limiting groove. The limiting groove extends along the length of the pressure plate. The limiting groove has a U-shaped cross-section with a circular arc bottom. According to structural dimensions, the limiting groove is divided into two sections, where the radius of the outer groove bottom is smaller than the radius of the inner groove bottom, and the width of the groove opening at the outer end is smaller than the width of the groove opening at the inner end. The center of the circular arc at the bottom of the limiting grooves with different radii is located on the same vertical plane as the center of the upper support column.

[0019] The cylinder adapter plate is a rectangular plate. Magnetic coupling rodless cylinder mounting holes are evenly distributed at the four corners of the adapter plate, and linear cylinder mounting holes are evenly distributed along the diagonal inwards.

[0020] The reciprocating central component pneumatic fixture proposed in this invention is used for semi-finish milling of the outer circumferential surface of a helicopter central component and the fork and irregular groove located on the outer circumferential surface. The cutting width is 4 mm, the cutting depth is 3 mm, the cutting speed is 40 m / min, the feed rate is 280 mm / min, and a finishing allowance of 1 mm is reserved.

[0021] The process of avoiding the cutting tool during machining is as follows:

[0022] During the semi-finish milling of the outer circumferential surface of the central part and the fork and irregular groove located on the outer circumferential surface, the process of automatic tool avoidance by the reciprocating pneumatic fixture is as follows:

[0023] Ⅰ. Semi-finish milling of the outer circumference surface. Taking the bottom surface of the blank as a reference, the outer circumference of the blank is divided into 6 arc segments, namely arc segment a, arc segment b, arc segment c, arc segment d, arc segment e and arc segment f. There are irregular grooves at the junction of each arc segment, and each of the irregular grooves is the starting point of the semi-finish milling of each arc segment.

[0024] Using a 50 mm diameter high-power milling cutter, the outer circumferential surface of the six arc segments is semi-finished in five passes according to the set process parameters.

[0025] The specific process is as follows:

[0026] The milling cutter starts from the irregular groove opening and performs semi-finish milling on arc segment a according to the set process parameters and machining path.

[0027] The first semi-finish milling pass. When the tool leaves the irregular groove, the PLC sends a start command to the cylinder, causing the linear cylinder on the adjacent arc segment of the irregular groove on arc segment a to drive the pressure plate to rise vertically, thereby releasing the partial clamping of the blank; simultaneously, the rodless cylinder drives the linear cylinder to move 80 mm along the guide groove towards the outer edge. During this process, the displacement sensor receives the cylinder movement signal. When the pressure plate reaches 100 mm above the upper end face of the blank, the displacement sensor sends a feedback signal to the PLC. After receiving the signal from the displacement sensor, the PLC sends a stop command to the cylinder, completing the first semi-finish milling pass.

[0028] In the first semi-finish milling pass, although the pressure plate on arc segment a releases the local clamping of the blank, it is still possible to cut the outer circumferential surface of arc segment a under the clamping of the other 5 pressure plates. The semi-finish milling is performed on the outer circumferential surface of arc segment a that has been released from local clamping.

[0029] The milling cutter returns to the starting point along arc segment a and completes the semi-finish milling of the remaining four passes of arc segment a according to the set process parameters. The clamping mechanism resets, restoring partial clamping of the workpiece.

[0030] The cutter continues to move along the outer circumference of the workpiece, reaching the starting point of arc segment b. The process of the first semi-finish milling of arc segment a is repeated to complete the first semi-finish milling of arc segment b.

[0031] After completing the first semi-finish milling pass of arc segment b, the milling cutter returns to the starting point along arc segment b and completes the remaining four semi-finish milling passes of arc segment b according to the set process parameters. The clamping mechanism resets, restoring partial clamping of the workpiece.

[0032] Repeat the semi-finish milling process of arc segment a for 5 passes to sequentially complete the semi-finish milling of the remaining arc segments on the outer circumference surface of the blank.

[0033] Fork in the outer circumferential surface of a semi-finish milled workpiece.

[0034] The workpiece's outer circumferential surface is semi-finished through five passes.

[0035] Semi-finish milling of the fork opening is performed using a solid cutter with a diameter of 20 mm.

[0036] Starting from the a-segment irregular groove opening, the fork opening is semi-finished in the first pass according to the set process parameters and machining path.

[0037] The specific process is as follows:

[0038] When the cutting tool leaves the starting point of arc segment a, the PLC sends a start command to the cylinder. The linear cylinder drives the pressure plate to rise vertically, releasing the partial clamping of the blank. Simultaneously, the magnetically coupled rodless cylinder drives the linear cylinder to move outward along the outer edge of the guide groove. During this process, the displacement sensor receives the cylinder movement signal. When the pressure plate reaches a position 100mm above the upper end face of the blank, it sends a feedback signal to the PLC. After receiving the signal from the displacement sensor, the PLC sends a stop command to the cylinder, putting the pressure plate in a tool-avoiding state. The milling cutter completes the first pass of semi-finish milling of the fork.

[0039] When the milling cutter reaches the irregular groove of arc segment b, the PLC sends a reset command to the cylinder, causing the clamping mechanism that has completed the tool avoidance to resume partial clamping of the workpiece. The process of the first pass of semi-finish milling of the fork is repeated, and the semi-finish milling of the remaining passes of arc segment b is completed in sequence.

[0040] Repeat the semi-finish milling process of arc segment a for 5 passes to sequentially complete the semi-finish milling of the forks of the remaining arc segments on the outer circumference surface of the blank.

[0041] Ⅲ. Semi-finish milling of irregular grooves on the outer circumferential surface of workpieces.

[0042] Using a 12 mm diameter integral cutter, the irregular groove on the outer circumference surface of the workpiece is semi-finish milled in 5 passes.

[0043] Repeat the semi-finish milling process of the fork opening, and semi-finish mill the irregular groove on the outer circumferential surface of the workpiece according to the set process parameters and machining path.

[0044] At this point, the semi-finish milling of the outer circumferential surface of the reciprocating central pneumatic fixture, as well as the forks and irregular grooves distributed on the outer circumferential surface, has been completed.

[0045] This invention comprises a support device, a clamping mechanism, a tool avoidance mechanism, and a status monitoring system. The support device employs a double-layer structure design. The upper support plate has a central positioning hole for locating and fixing the center component. Six upper support columns are evenly distributed around the central positioning hole to support the center component. Guide grooves and limiting columns are distributed on the outer sides of the upper support columns. The clamping mechanism is integrated into the lower support plate.

[0046] The clamping mechanism employs a six-point evenly distributed layout, consisting of six pressure plates, six linear cylinders, six magnetically coupled rodless cylinders, six force sensors, and 24 displacement sensors. Each pressure plate is equipped with a limit groove. The linear cylinders are fixedly mounted on the lower support plate, and their piston rods are connected to the pressure plates via guide grooves on the upper support plate. The reciprocating motion of the piston rods in the vertical direction controls the pressure plates, achieving the clamping and releasing of the central part. This clamping mechanism also features a tool avoidance function. When a tool approaches, the magnetically coupled rodless cylinders drive the linear cylinders to move horizontally along the guide grooves, causing the limit pins to separate from the limit grooves on the pressure plates, thus achieving the tool avoidance function.

[0047] The condition monitoring system includes 6 force sensors, 24 displacement sensors and 1 triaxial accelerometer, which monitor the clamping force, the position of the linear cylinder piston, the position of the magnetically coupled rodless cylinder and the vibration response characteristics of the fixture during the machining of the central part, respectively.

[0048] This invention enables the automatic clamping of the central component of a helicopter propeller. After the center of the central component is fixed in the positioning hole of the upper support plate, a linear cylinder drives the pressure plate upward, bringing it to a position 100 mm from the upper end face of the central component. Then, a magnetically coupled rodless cylinder drives the linear cylinder to move horizontally until the limiting post and the limiting groove of the pressure plate are precisely aligned and in complete contact. Finally, the linear cylinder drives the pressure plate downward to complete the clamping action. The entire process is monitored in real time by a force sensor, and the clamping force is dynamically adjusted to achieve high-precision and controllable clamping.

[0049] When machining the outer edge of a helicopter propeller central component, interference between the clamping plate and the cutting tool exists. This invention proposes a reciprocating pneumatic clamp for the central component, achieving dynamic tool avoidance without disassembling the central component during machining. During machining, when the cutting tool leaves the irregular groove of the blank, the PLC sends a start command to the cylinder. The linear cylinder drives the clamping plate to rise vertically, releasing the partial clamping of the central component. Simultaneously, the magnetically coupled rodless cylinder drives the linear cylinder to move outward along the guide groove, avoiding the cutting tool. The displacement sensor receives the cylinder movement signal. When the clamping plate reaches 100 mm above the upper surface of the central component, the displacement sensor sends a feedback signal to the PLC. Upon receiving the signal, the PLC sends a stop command to the cylinder. When the cutting tool reaches the next irregular groove, the PLC sends a reset command to the cylinder. The clamping mechanism that just completed the tool avoidance resumes partial clamping of the blank, completing the tool avoidance operation. When the cutting tool leaves the next irregular groove, the clamping mechanism at the next location repeats the tool avoidance operation.

[0050] This invention supports the central component through a positioning hole and six upper support columns. It achieves automatic clamping of the central component and tool avoidance through a linear cylinder and a magnetically coupled rodless cylinder. The clamping and disassembly are convenient, which improves processing efficiency and reduces processing costs.

[0051] The central component pneumatic clamp proposed in this invention can be controlled by PLC programming, and data communication is built based on the RS.485 bus standard. During automatic clamping of the central component, the pneumatic clamp can dynamically adjust the pressure of the linear cylinder by adjusting the air intake based on feedback from a force sensor, ensuring that the clamping force remains balanced. During tool avoidance, the central component pneumatic clamp achieves closed-loop control based on displacement sensor feedback, ensuring that only one clamping plate is in the released state during a single avoidance operation, while the remaining clamping plates are in the clamping state of the central component.

[0052] To achieve automatic clamping of the central component and tool avoidance of the pressure plate, the support device of this invention adopts a double-layer design, including an upper support plate, a main support column, and a lower support plate, providing sufficient space for cylinder installation. Due to the large number of critical functional surfaces and complex positioning of the helicopter's central component, the upper support plate has a positioning mounting hole in its center to achieve positioning and fixing of the central component. The lower support plate is a circular plate with six magnetically coupled rodless cylinder mounting slots evenly distributed along its outer edge. Between each magnetically coupled rodless cylinder mounting slot is a U-shaped groove for fixing to a vertical milling machine. Since the lower support plate needs to be installed on a vertical milling machine, and its dimensions must meet the installation requirements of the magnetically coupled rodless cylinders, the radius of the lower support plate is designed to be 800 mm.

[0053] As a key component in reciprocating pneumatic clamping fixtures for central components, the pressure plate must meet the following design requirements. The central component is generally made of titanium alloy or other composite materials; therefore, the hardness of the pressure plate must be lower than that of the central component to avoid damage during clamping. When clamping the central component, the pressure plate needs to be able to move radially along the upper support plate; therefore, a limiting groove with a wider inner end and a narrower outer end is provided on the pressure plate, with the outer end used to engage with the pin on the upper end face of the limiting post. During the clamping process of the central component, it must be ensured that the pressure plate will not bend due to the reaction force of the central component; therefore, the upper end face of the limiting post supports the pressure plate.

[0054] In traditional central part machining, the outer circumferential surface of the central part is first clamped with a clamping plate to machine its inner cavity. After the inner cavity is machined, the clamping plate is removed and re-clamped onto the inner cavity to machine the outer contour. This requires two separate machining operations for both the inner cavity and the outer contour. This repetitive clamping method significantly increases the positioning error of the central part, severely impacting machining efficiency. The reciprocating pneumatic chuck for central parts designed in this invention features tool avoidance, allowing for simultaneous machining of both the inner cavity and outer contour in a single clamping operation, while also achieving tool avoidance during the outer contour machining. This improves machining efficiency and reduces positioning errors caused by repeated clamping.

[0055] Helicopter central components are generally made of titanium alloy or other composite materials. Traditional clamping fixtures mostly rely on manual adjustment of clamping force, which cannot ensure consistent clamping force when clamping at multiple points, easily leading to material deformation and compromising fatigue strength and dimensional tolerances. The reciprocating pneumatic clamping fixture for central components designed in this invention integrates a triaxial accelerometer and a force sensor. This allows for real-time monitoring of the vibration characteristics of the central component during machining. Based on feedback from the force sensor, the clamping force is dynamically adjusted by regulating the air intake, ensuring a balanced clamping force on the central component and preventing excessive local stress that could lead to deformation. Attached Figure Description

[0056] Figure 1 This is an isometric view of the structure of the present invention.

[0057] Figure 2 for Figure 1 The main view.

[0058] Figure 3 for Figure 1 Top view.

[0059] Figure 4 This is a partial sectional view of the clamping mechanism.

[0060] Figure 5 This is a cross-sectional view of the support structure.

[0061] Figure 6 This is an isometric view of the limiting post.

[0062] Figure 7 Exploded view of the cylinder assembly.

[0063] Figure 8 This is an isometric view of the upper support plate.

[0064] Figure 9 Axonometric drawing of the main support column.

[0065] Figure 10 This is an isometric view of the lower support plate.

[0066] Figure 11 This is an isometric drawing of a tooling that includes a central component.

[0067] Figure 12 This is a top view of the central component.

[0068] In the diagram: 1. Upper support plate; 2. Pressure plate; 3. Limiting groove; 4. Limiting post; 5. Guide groove; 6. Cylinder piston rod; 7. Upper support post; 8. Main support post; 9. Lower support plate; 10. Linear cylinder; 11. Magnetic coupling rodless cylinder; 12. Force sensor; 13. Displacement sensor; 14. Triaxial accelerometer; 15. Positioning mounting hole; 16. Threaded hole; 17. Flange; 18. Horizontal support surface; 19. Vertical guide surface; 20. Cylinder adapter plate; 21. Outer circumferential surface of central component; 22. Fork; 23. Irregular groove. Detailed Implementation

[0069] This embodiment is a reciprocating central pneumatic clamp, including a support plate, 6 limiting posts 4, 6 upper support posts 7, a main support post 8, and 6 clamping mechanisms. The support plate is divided into an upper support plate 1 and a lower support plate 9. Each clamping mechanism includes a linear cylinder 10, a magnetically coupled rodless cylinder 11, a pressure plate 2, 6 force sensors 12, and 1 triaxial acceleration sensor 14.

[0070] The two end faces of the main support column 8 are fixedly connected to the lower surface of the upper support plate 1 and the upper surface of the lower support plate 9, respectively, to form the support body of the pneumatic clamp.

[0071] The six clamping mechanisms are all magnetically coupled rodless cylinders 11, which are evenly distributed on the upper surface of the lower support plate 9 in the support body. A linear cylinder 10 is installed on the upper surface of each magnetically coupled rodless cylinder. The piston rod 6 of the linear cylinder passes through the guide groove on the upper support plate 1, and its upper end is fixedly connected to the lower end face of the pressure plate 2. A force sensor 12 is located between the upper end face of each cylinder piston rod and the lower surface of the pressure plate.

[0072] The six limiting posts 4 are fixed to the upper surface of the upper support plate 1, located at the edge of the upper support plate, and are located in the same radial direction as the guide groove;

[0073] The outer end of the upper limit groove of the pressure plate 2 is engaged with the pin on the upper end face of the limit post 4.

[0074] The lower support plate 9 is a circular plate, and six mounting slots for magnetically coupled rodless cylinders 11 are evenly distributed on the outer edge of its upper surface. Between each mounting slot for a magnetically coupled rodless cylinder is a U-shaped groove for fixing it to a vertical milling machine.

[0075] The upper support plate 1 is also a circular plate with a central positioning mounting hole 15 for the central component. An annular boss is located at the upper end of this positioning mounting hole; this annular boss serves as the mounting base for the central component. Guide grooves are evenly distributed around the circumference of the upper support plate surface. Upper support columns 7 are fixed to the inner side of each guide groove; limit columns 4 are fixed to the outer side of each guide groove, ensuring that the centers of the upper support columns, the central axis of the guide grooves, and the centers of the limit columns are located on the same radial line of the upper support plate.

[0076] The upper support column 7 is cylindrical in shape, with two symmetrical planes cut on its side near the top for attaching strain gauges.

[0077] The upper end face of the limiting post 4 has a circular pin; the end face formed by the diameter difference between the pin and the limiting post is a horizontal support surface 18, which is used to support the pressure plate and ensure that the pressure plate is always in a horizontal state when the linear cylinder drives the pressure plate to press down; the circumferential surface of the pin is a vertical guide surface 19, which is the outer circumferential surface of the pin and is used to guide the movement of the pressure plate in the vertical direction.

[0078] The pressure plate 2 is a rectangular plate. A limiting groove is present on this pressure plate, extending along its length. The limiting groove has a U-shaped cross-section with a circular arc bottom. The limiting groove is divided into two sections according to structural dimensions, with the radius of the outer groove bottom being smaller than that of the inner groove bottom, and the width of the groove opening at the outer end being smaller than that at the inner end. The centers of the circular arcs at the bottom of the limiting grooves with different radii are all located on the same vertical plane as the center of the upper support column 7.

[0079] The cylinder adapter plate 20 is a rectangular plate. There are four threaded holes evenly distributed at the four corners of the adapter plate for connecting magnetically coupled rodless cylinders, and another four threaded holes evenly distributed along the diagonal inwards for connecting linear cylinders.

[0080] The force sensor 12 and the triaxial accelerometer 14 are described, wherein there are six force sensors, each fixed to the lower surface of one of the pressure plates. A flange connected to the pressure plate is mounted on the upper surface of each force sensor, and a flange connected to the cylinder piston rod is mounted on its lower surface.

[0081] Both the selected linear cylinder and the magnetically coupled rodless cylinder are equipped with displacement sensors 13.

[0082] The triaxial accelerometer 14 is embedded and fixed on the outer circumferential surface of the upper support plate.

[0083] The reciprocating pneumatic fixture for central components proposed in this embodiment is used for semi-finish milling of the outer circumferential surface of helicopter central components and the forks and irregular grooves located on the outer circumferential surface.

[0084] The process parameters for the semi-finish milling are as follows: cutting width is 4 mm, cutting depth is 3 mm, cutting speed is 40 m / min, feed rate is 280 mm / min, and a finishing allowance of 1 mm is reserved.

[0085] When semi-finish milling the outer circumferential surface of the central part and the fork and irregular groove located on the outer circumferential surface, there is a problem of interference between the tool and the pressure plate. The tool avoidance method of the reciprocating central part pneumatic fixture proposed in this embodiment is explained as follows.

[0086] During the semi-finish milling of the outer circumferential surface of the central part and the fork and irregular groove located on the outer circumferential surface, the process of automatic tool avoidance by the reciprocating pneumatic fixture is as follows:

[0087] Ⅰ. Semi-finish milling of the outer circumference surface. Using the bottom surface of the blank as a reference, the outer circumference of the blank is divided into six arc segments: arc segment a, arc segment b, arc segment c, arc segment d, arc segment e, and arc segment f. Each arc segment has a shaped groove at its junction, and each shaped groove serves as the starting point for the semi-finish milling of that arc segment.

[0088] Using a 50 mm diameter high-power milling cutter, the outer circumferential surface containing the six arc segments is semi-finished in five passes.

[0089] The specific process is as follows:

[0090] The milling cutter starts from the irregular groove opening and performs semi-finish milling on arc segment a according to the set process parameters and machining path.

[0091] The first semi-finish milling pass. When the tool leaves the irregular groove, the PLC sends a start command to the cylinder, causing the linear cylinder 10 on the adjacent arc segment of the irregular groove on arc segment a to drive the pressure plate 2 to rise vertically, thereby releasing the partial clamping of the blank; at the same time, the rodless cylinder 11 drives the linear cylinder to move 80 mm along the guide groove towards the outer edge. During this process, the displacement sensor receives the cylinder movement signal. When the pressure plate reaches 100 mm above the upper end face of the blank, the displacement sensor sends a feedback signal to the PLC. After receiving the signal from the displacement sensor, the PLC sends a stop command to the cylinder, completing the first semi-finish milling pass.

[0092] In the first semi-finish milling pass, although the pressure plate on arc segment a releases the local clamping of the blank, it is still possible to cut the outer circumferential surface of arc segment a under the clamping of the other 5 pressure plates. The semi-finish milling is performed on the outer circumferential surface of arc segment a that has been released from local clamping.

[0093] The milling cutter returns to the starting point along arc segment a and completes the semi-finish milling of the remaining four passes of arc segment a according to the set process parameters. The clamping mechanism resets, restoring partial clamping of the workpiece.

[0094] The cutter continues to move along the outer circumference of the workpiece, reaching the starting point of arc segment b. The process of the first semi-finish milling of arc segment a is repeated to complete the first semi-finish milling of arc segment b.

[0095] After completing the first semi-finish milling pass of arc segment b, the milling cutter returns to the starting point along arc segment b and completes the remaining four semi-finish milling passes of arc segment b according to the set process parameters. The clamping mechanism resets, restoring partial clamping of the workpiece.

[0096] Repeat the semi-finish milling process of arc segment a for 5 passes to sequentially complete the semi-finish milling of the remaining arc segments on the outer circumference surface of the blank.

[0097] Fork in the outer circumferential surface of a semi-finish milled workpiece.

[0098] The workpiece's outer circumferential surface is semi-finished through five passes.

[0099] Semi-finish milling of the fork opening is performed using a solid cutter with a diameter of 20 mm.

[0100] Starting from the a-segment irregular groove opening, the fork opening is semi-finished in the first pass according to the set process parameters and machining path.

[0101] The specific process is as follows:

[0102] When the cutting tool leaves the starting point of arc segment a, the PLC sends a start command to the cylinder. The linear cylinder 10 drives the pressure plate 2 to rise vertically, releasing the partial clamping of the blank. Simultaneously, the magnetically coupled rodless cylinder 11 drives the linear cylinder to move outward along the outer edge of the guide groove. During this process, the displacement sensor receives the cylinder movement signal. When the pressure plate reaches a position 100mm above the upper end face of the blank, it sends a feedback signal to the PLC. After receiving the signal from the displacement sensor, the PLC sends a stop command to the cylinder, putting the pressure plate in a tool-avoiding state. The milling cutter completes the first pass of semi-finish milling of the fork.

[0103] When the milling cutter reaches the irregular groove of arc segment b, the PLC sends a reset command to the cylinder, causing the clamping mechanism that has completed the tool avoidance to resume partial clamping of the workpiece. The process of the first pass of semi-finish milling of the fork is repeated, and the semi-finish milling of the remaining passes of arc segment b is completed in sequence.

[0104] Repeat the semi-finish milling process of arc segment a for 5 passes to sequentially complete the semi-finish milling of the forks of the remaining arc segments on the outer circumference surface of the blank.

[0105] Ⅲ. Semi-finish milling of irregular grooves on the outer circumferential surface of workpieces.

[0106] Using a 12 mm diameter integral cutter, the irregular groove on the outer circumference surface of the workpiece is semi-finish milled in 5 passes.

[0107] Repeat the semi-finish milling process of the fork opening, and semi-finish mill the irregular groove on the outer circumferential surface of the workpiece according to the set process parameters and machining path.

[0108] At this point, the semi-finish milling of the outer circumferential surface of the reciprocating central pneumatic fixture, as well as the forks and irregular grooves distributed on the outer circumferential surface, has been completed.

Claims

1. A reciprocating central piece pneumatic clamp, characterized in that, It includes support plate, 6 limit column (4), 6 upper support column (7), main support column (8) and 6 clamping mechanism, wherein, the support plate is divided into upper support plate (1) and lower support plate (9); the clamping mechanism all includes linear cylinder (10), magnetic coupling rodless cylinder (11), pressing plate (2), 6 force sensors (12) and 1 three-axis acceleration sensor (14); The both ends of the main support column (8) are fixedly connected with the lower surface of the upper support plate (1) and the upper surface of the lower support plate (9), forming the support body of the pneumatic clamp; The magnetic coupling rodless cylinder (11) of the 6 clamping mechanisms is evenly distributed on the upper surface of the lower support plate (9) in the support body, and a linear cylinder (10) is installed on the upper surface of each magnetic coupling rodless cylinder; the cylinder piston rod (6) of the linear cylinder penetrates through the guide groove on the upper support plate (1), and the upper end is fixedly connected with the lower end surface of the pressing plate (2); there is a force sensor (12) between the upper end surface of each cylinder piston rod and the lower surface of the pressing plate; Each upper support column (7) is fixed on the inner side of the guide groove; The 6 limit columns (4) are fixed on the upper surface of the upper support plate (1) and located at the edge of the upper support plate and in the same radial direction as the guide groove; The outer end of the limit slot (3) on the pressing plate (2) is clamped with the pin column on the upper end surface of the limit column (4); 6 force sensors are fixed on the lower surface of each pressing plate; the three-axis acceleration sensor (14) is embedded and fixed on the outer circumferential surface of the upper support plate.

2. The reciprocating central piece pneumatic clamp according to claim 1, wherein, The upper surface of the lower support plate (9) is evenly distributed with 6 installation grooves of magnetic coupling rodless cylinder (11); between each magnetic coupling rodless cylinder installation groove, there is a U-shaped groove for fixing with the vertical milling machine; The upper support plate (1) has a positioning installation hole (15) of a central part in the center, and an annular boss is arranged on the upper end hole of the positioning installation hole; the annular boss is the mounting seat of the central part; the guide grooves (5) are evenly distributed on the circumference of the surface of the upper support plate; The upper support column (7) is fixed on the inner side of the guide groove; the limit column (4) is fixed on the outer side of the guide groove, and the center of the upper support column, the central axis of the guide groove and the center of the limit column are located on the same radial line of the upper support plate; The circumferential surface of the upper end of the upper support column (7) is cut with two symmetrical planes for pasting strain gauges.

3. The reciprocating central piece pneumatic clamp according to claim 1, wherein, The upper end surface of the limit column (4) has a circular pin column; the end surface formed by the diameter difference between the pin column and the limit column is a horizontal support surface (18) for supporting the pressing plate, ensuring that the pressing plate is always in a horizontal state when the linear cylinder drives the pressing plate to press down; the circumferential surface of the pin column is a vertical guide surface (19), which is the outer circumferential surface of the pin column, for guiding the movement of the pressing plate in the vertical direction.

4. The reciprocating central piece pneumatic clamp of claim 1, wherein, The pressing plate (2) is provided with a limiting groove (3); the limiting groove extends along the length direction of the pressing plate; the cross section of the limiting groove is U-shaped, the groove bottom is circular arc-shaped; the limiting groove is divided into two sections according to the structural size, the radius of the groove bottom of the outer end is smaller than that of the inner end, and the width of the groove opening of the outer end is smaller than that of the inner end; the centers of the circular arc groove bottoms with different radii are located on the same vertical plane with the center of the upper supporting column (7).

5. The reciprocating central member pneumatic clamp of claim 1 wherein, The air cylinder adapter plate (20) is a rectangular plate; magnetic coupling rodless air cylinder mounting holes are uniformly distributed at the four corners of the adapter plate, and straight air cylinder mounting holes are uniformly distributed inward along the diagonal lines.

6. A method for avoiding a tool in the reciprocating central part pneumatic clamp of claim 1, the reciprocating central part pneumatic clamp being used for semi-finishing milling the inner cavity, the outer circumferential surface and the fork and special-shaped groove located on the outer circumferential surface of the helicopter central part; the process parameters of the semi-finishing milling are as follows: the cutting width is 4 mm, the cutting depth is 3 mm, the cutting speed is 40 m / min, the feed speed is 280 mm / min, and the allowance for finishing is 1 mm; It is characterized in that: When semi-finishing milling the outer circumferential surface and the fork and special-shaped groove located on the outer circumferential surface of the central part, the process of automatically avoiding a tool in the reciprocating pneumatic clamp is as follows: Ⅰ. Semi-finishing milling the outer circumferential surface: Divide the outer circumferential surface of the blank into six arc segments, namely a arc segment, b arc segment, c arc segment, d arc segment, e arc segment and f arc segment, with the bottom surface of the blank as the reference; each arc segment has a special-shaped groove at the joint, and each special-shaped groove is the starting point of semi-finishing milling of each arc segment; Use a strong milling cutter with a diameter of 50 mm to semi-finish mill the outer circumferential surface of the six arc segments by five passes in turn according to the set process parameters; Half-finishing of the outer circumferential surface of the workpiece: Semi-finish mill the fork of the outer circumferential surface of the workpiece by five passes; Use a whole cutter with a diameter of 20 mm to semi-finish mill the fork; Take the a arc segment special-shaped groove opening as the starting point, and semi-finish mill the fork by the first pass according to the set process parameters and machining path; Ⅲ. Semi-finishing milling the special-shaped groove of the outer circumferential surface of the workpiece: Use a whole cutter with a diameter of 12 mm to semi-finish mill the special-shaped groove of the outer circumferential surface of the workpiece by five passes; Repeat the process of semi-finishing milling the fork, and semi-finish mill the special-shaped groove of the outer circumferential surface of the workpiece according to the set process parameters and machining path; At this point, the semi-finishing milling of the outer circumferential surface of the reciprocating central part pneumatic clamp and the fork and special-shaped groove distributed on the outer circumferential surface is completed.

7. The knife avoidance method for a reciprocating central piece pneumatic clamp as defined in claim 6, wherein, The specific process of semi-finishing milling the outer circumferential surface is as follows: Take the special-shaped groove opening as the starting point, and semi-finish mill the a arc segment according to the set process parameters and machining path; The first pass semi-finishing milling; when the cutter leaves the special-shaped groove, the PLC sends a start command to the cylinder, the linear cylinder (10) on the adjacent arc segment of the special-shaped groove on the a arc segment drives the press plate (2) to vertically rise to release the local clamping of the blank; at the same time, the cylinder (11) is driven to move 80 mm along the guide groove to the outer edge; in this process, the displacement sensor receives the cylinder movement signal, and when the press plate reaches the upper end surface of the blank 100 mm, the displacement sensor sends a feedback signal to the PLC, and the PLC receives the signal of the displacement sensor and sends a stop command to the cylinder, completing the first pass semi-finishing milling; In the first pass semi-finishing milling, although the press plate on the a arc segment releases the local clamping of the blank, the outer circumferential surface of the a arc segment can still be cut under the clamping of the remaining 5 press plates, and the semi-finishing milling has released the local clamping of the a arc segment. The milling cutter returns to the starting point along the a arc segment, and completes the semi-finishing milling of the remaining 4 passes of the a arc segment according to the set process parameters. The clamping mechanism is reset to restore the local clamping of the blank. The cutter continues to move along the outer circumferential surface of the blank and reaches the starting point of the b arc segment. Repeat the process of the first pass semi-finishing milling of the a arc segment to complete the first pass semi-finishing milling of the b arc segment. After completing the first pass semi-finishing milling of the b arc segment, the milling cutter returns to the starting point along the b arc segment, and completes the semi-finishing milling of the remaining 4 passes of the b arc segment according to the set process parameters. The clamping mechanism is reset to restore the local clamping of the blank. Repeat the process of the 5 pass semi-finishing milling of the a arc segment to complete the semi-finishing milling of the remaining arc segments of the outer circumferential surface of the blank in turn.

8. The knife avoidance method for a reciprocating central piece pneumatic clamp as defined in claim 6, wherein, The specific process of the fork of the semi-finishing milling of the outer circumferential surface of the workpiece is as follows: When the cutter leaves the starting point of the a arc segment, the PLC sends a start command to the cylinder, the linear cylinder (10) drives the press plate (2) to vertically rise to release the local clamping of the blank; at the same time, the cylinder (11) is driven to move along the guide groove to the outer edge; in this process, the displacement sensor receives the cylinder movement signal, and when the press plate reaches the upper end surface of the blank 100 mm, the displacement sensor sends a feedback signal to the PLC, and the PLC receives the signal of the displacement sensor and sends a stop command to the cylinder, completing the first pass semi-finishing milling of the a arc segment. When the milling cutter reaches the special-shaped groove of the b arc segment, the PLC sends a reset command to the cylinder to restore the local clamping of the blank to the clamping mechanism that has completed the avoidance of the cutter; repeat the process of the first pass semi-finishing milling of the fork to complete the semi-finishing milling of the remaining passes of the fork of the b arc segment in turn. Repeat the process of the 5 pass semi-finishing milling of the a arc segment to complete the semi-finishing milling of the fork of the remaining arc segments of the outer circumferential surface of the blank in turn.

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