Axial end face clamping device for thin-walled rotary parts and clamping method

Abstract

This invention provides an axial end-face clamping device and clamping method for thin-walled rotating parts. The device includes a base assembly, an upper clamping assembly, and a force actuator. The base assembly has a bottom positioning surface for supporting the lower end face of the workpiece, and the upper clamping assembly has an upper clamping surface for pressing against the upper end face of the workpiece. The force actuator drives the upper clamping surface to move towards the bottom positioning surface, thereby axially clamping the workpiece between the upper clamping surface and the bottom positioning surface. This device applies clamping force axially to the end face of the workpiece, avoiding deformation of the thin-walled structure caused by radial clamping, while fully exposing the radial side of the thin-walled structure, facilitating interference-free machining by five-axis tools. The replaceable bottom mounting base and upper pressure cap are adaptable to workpieces of various specifications, and the quick-change base supports offline pre-assembly and rapid production changeover. This method utilizes this device to achieve axial clamping and interference-free machining of the workpiece.

Description

Technical Field

[0001] This invention relates to the field of CNC machine tool tooling technology, specifically to an axial end face clamping device for clamping workpieces on a CNC machine tool for cutting operations, and a method for clamping workpieces using the device. Background Technology

[0002] Impellers are core components of turbomachinery, pumps, and aero engines. Their blades are typically thin-walled curved surfaces, and the profile accuracy and surface quality of the blades directly affect the overall efficiency and reliability of the machine. When machining impellers on CNC machine tools, the first step is to reliably clamp the impeller workpiece onto the machine tool's worktable. The clamping method directly affects the machining accuracy, efficiency, and finished product yield.

[0003] Currently, a common clamping method for machining impellers is to use a three-jaw chuck to hold the impeller journal or outer edge, with a tailstock center clamping it from the other end. In this clamping method, the clamping force of the three-jaw chuck is applied radially along the workpiece. For thin-walled impellers, this radial clamping force can easily cause elastic or even plastic deformation of the workpiece. When the chuck is released after machining, the workpiece springs back, resulting in out-of-tolerance blade profile accuracy and inner hole roundness. In addition, the chuck jaws occupy part of the space on the outer diameter of the workpiece when clamped, which can easily interfere with the tool movement path. This makes it difficult to complete the finishing of all blades in a single clamping, often requiring multiple clamping and changes in clamping position, thus introducing additional positioning errors and reducing machining efficiency.

[0004] Another common clamping method is to use a hydraulic expansion sleeve to radially tighten the impeller workpiece from its inner bore. While hydraulic expansion sleeves can provide a relatively uniform radial clamping force, they also carry the risk of deformation of the thin-walled inner bore due to radial force. The expansion sleeve has a limited range of tightening diameters; a single type of expansion sleeve typically only fits workpieces with one type of inner bore diameter. When the impeller specification changes, the entire expansion sleeve assembly needs to be replaced, resulting in poor versatility and high production changeover costs.

[0005] Existing technologies also include a clamping scheme that uses a tailstock center to axially clamp against the bottom positioning surface. In this scheme, the center contacts the center hole or center area on the upper end face of the workpiece in a point-contact manner, applying clamping force axially. This cannot achieve surface contact clamping, and the clamping force is concentrated in a very small area on the workpiece end face, easily causing indentations or localized deformation. For impellers with low end face hardness or precision-machined end faces, such damage is often unacceptable. Furthermore, the center itself is usually a slender conical structure, which may restrict the tool's movement space near the upper end of the workpiece during machining, making interference-free machining of the entire blade impossible.

[0006] In multi-variety, small-batch impeller machining scenarios, changing machining specifications requires replacing the entire fixture or recalibrating the fixture. Traditional calibration methods use dial indicators or tool setters to check the fixture's positional accuracy on the machine tool item by item. A complete calibration operation typically takes tens of minutes and depends heavily on the operator's experience; calibration results may vary between different operators, affecting the consistency of batch machining accuracy. While fixture installation using a combination of locating pins and bolts can improve repeatability to some extent, a clearance exists between the locating pin and the pin hole. This clearance may increase further after repeated disassembly and assembly, still failing to meet the repeatability requirements of high-precision impeller machining. Summary of the Invention

[0007] The technical problem solved by this invention is to provide an axial end face clamping device and clamping method for thin-walled rotating parts, so as to reduce the deformation of the workpiece during clamping, avoid the interference of the clamping parts with the tool machining path, and improve the versatility of the tooling and production changeover efficiency.

[0008] A first aspect of the present invention provides an axial end-face clamping device for a thin-walled rotating part, used for clamping a workpiece on a CNC machine tool. The workpiece has an upper end face, a lower end face, and a thin-walled structural portion located between the upper and lower end faces. The device includes a base assembly, an upper clamping assembly, and a force actuator. The base assembly is fixedly mounted on the CNC machine tool and has a bottom positioning surface for supporting the lower end face of the workpiece. The upper clamping assembly has an upper clamping surface for pressing against the upper end face of the workpiece. The force actuator is drivenly connected to the upper clamping assembly and is configured to drive the upper clamping surface to move in the direction of the bottom positioning surface, so that the workpiece is axially clamped between the upper clamping surface and the bottom positioning surface. Thus, the clamping force is applied axially to the upper and lower end faces of the workpiece, rather than acting on the radial side of the workpiece, fundamentally avoiding the deformation problem of the thin-walled structural portion caused by radial clamping. Meanwhile, since the clamping force acts on the axial end face, the thin-walled structure of the workpiece remains fully exposed on the radial side and is not obstructed by the clamping parts. This allows the five-axis tool of the CNC machine tool to approach and machine its surface from any angle, which is beneficial to complete the finishing of the entire surface in one clamping and reduce the number of clamping times and the accumulation of positioning errors.

[0009] Furthermore, the force actuator is a fluid pressure-driven cylinder mechanism, which has a cylinder body and an output end that can move axially relative to the cylinder body. The output end is connected to the upper clamping assembly. Even further, this fluid pressure-driven cylinder mechanism can be a hydraulic cylinder or a pneumatic cylinder. Hydraulic cylinders have high force density and are suitable for heavy cutting processes; pneumatic cylinders have fast response speed and a simple system, making them suitable for light cutting or finishing applications. The operator can adjust the fluid pressure according to the workpiece material and machining parameters to control the clamping force, avoiding deformation of thin-walled end faces due to excessive clamping force or cutting vibration caused by insufficient clamping force.

[0010] In another implementation, the force actuator includes an electric linear actuator, which is driven by a motor to rotate a lead screw. The lead screw nut converts the rotational motion into linear motion, driving the upper clamping assembly to move. The electric linear actuator features high position control accuracy and programmable control, making it easy to integrate with CNC systems and suitable for digital machining scenarios requiring precise control of the clamping stroke.

[0011] Furthermore, the base assembly includes a bottom mounting base with a bottom positioning surface formed on the top surface of the bottom mounting base; the upper clamping assembly includes an upper end cap with an upper clamping surface formed on the bottom end surface of the upper end cap. The bottom mounting base and the upper end cap are both independent components and can be precision machined separately to ensure the flatness and parallelism of the positioning and clamping surfaces. The disc-shaped structure of the upper end cap allows the clamping force to be evenly transmitted to the upper end surface of the workpiece along the circumferential direction.

[0012] Furthermore, at least one of the bottom mounting base and the upper end cap is configured to be detachable and replaceable from the device to accommodate workpieces with at least one variation in upper end face size and lower end face size. When processing workpieces of different specifications, only the adapter matching the end face size of the workpiece needs to be replaced, without replacing the entire device, which helps to reduce tooling investment costs and changeover time in multi-variety, small-batch production.

[0013] Furthermore, the device also includes an upper positioning component, which is positioned above the upper pressure cap and used to guide the upper pressure cap to align relative to the bottom mounting base. During the clamping process, the upper positioning component guides the pressure cap to center, which helps to ensure the parallelism between the clamping surface and the positioning surface, avoids uneven force on the workpiece or positioning deviation due to the pressure cap being misaligned, and improves the consistency of clamping accuracy in batch processing.

[0014] Furthermore, the base assembly also includes a quick-change base, which is fixedly installed on the machining table of the CNC machine tool. The bottom mounting base is installed on the quick-change base in a repeatable positioning manner. Repeatable positioning means that when the bottom mounting base is removed from the quick-change base and reinstalled, its spatial position can be restored to its state before removal, without the need for re-alignment using a dial indicator. The quick-change base supports offline pre-installation and online rapid replacement, significantly reducing machine tool downtime.

[0015] Furthermore, the device also includes a rigid positioning assembly, which comprises a positioning fixing post and a slot. One of the positioning fixing post and the slot is disposed in the moving part linked to the force actuator, and the other is disposed in the base assembly. The positioning fixing post is engaged in the slot as the force actuator drives the upper clamping assembly to axially clamp the workpiece, thereby achieving rigid positioning of the upper clamping assembly relative to the base assembly in the clamped state. After the clamping state is established, the rigid positioning assembly provides mechanical rigid constraint, maintaining positioning without relying on the continuous driving force of the force actuator, which is beneficial for suppressing vibration and maintaining machining accuracy under heavy cutting or intermittent cutting conditions.

[0016] A second aspect of the present invention provides a clamping method using the above-described axial end-face clamping device for thin-walled rotating parts. The method includes: placing the lower end face of the workpiece on a bottom positioning surface; driving an upper clamping assembly towards the bottom positioning surface using a force actuator, so that the upper clamping surface presses against the upper end face of the workpiece, thereby axially clamping the workpiece between the upper clamping surface and the bottom positioning surface; in the axially clamped state, the radial side of the thin-walled structural portion of the workpiece is not obstructed by clamping components. This method transforms the structural advantages of the device into technological advantages, achieving a chain of technical benefits including axial clamping, structural exposure, and five-axis single-processing.

[0017] Furthermore, before placing the lower end face of the workpiece on the bottom positioning surface, the method further includes: installing at least one of a bottom mounting base and an upper end cap corresponding to the specifications of the workpiece to be processed onto the device. This preliminary step embodies a rapid changeover process in multi-specification production, which helps reduce auxiliary time in batch production.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: First, by applying clamping force axially to the upper and lower end faces of the workpiece, axial clamping is achieved, avoiding deformation of thin-walled structures caused by radial force application. This improves machining accuracy and product yield. This solution changes the force application location from radial to axial end faces, distributing the force along the axial direction of the thickest part of the workpiece, thus eliminating the source of deformation at the mechanical level. After machining, the workpiece will not spring back when the clamping force is released, reliably ensuring surface accuracy and inner hole roundness.

[0019] Secondly, the clamping element only contacts the axial end face of the workpiece, while the radial side of the thin-walled structure remains fully exposed, allowing the tool to perform interference-free machining. This facilitates completing the finishing of the entire profile in a single clamping operation. Completing the finishing of the entire profile in a single clamping operation not only improves efficiency but also eliminates the accumulation of datum conversion errors and positioning errors caused by multiple clamping operations.

[0020] Third, the replaceable bottom mounting base and upper pressure cap allow the device to adapt to workpieces of various specifications, improving the versatility of the tooling and reducing tooling costs for multi-variety production. Only two end face parts need to be replaced to handle all specification variations; the end face parts have simple geometry and their manufacturing cost is far lower than that of the entire fixture set.

[0021] Fourth, the quick-change base's repeatable positioning installation method supports offline pre-installation and online rapid replacement, significantly shortening changeover time and improving equipment utilization. The synergy between the quick-change base and the axial end-face clamping scheme makes offline pre-installation truly feasible and further reduces machine tool downtime.

[0022] Fifth, the rigid positioning component provides mechanical rigidity after clamping is established, maintaining positioning without relying on the continuous driving force of the force actuator. This is beneficial for suppressing vibration and maintaining machining accuracy under heavy cutting or intermittent cutting conditions. The decoupling of the fluid-driven force application function and the mechanical locking position holding function gives the device the dual advantages of flexible clamping and rigid holding. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a three-dimensional structural diagram of an axial end face clamping device for a thin-walled rotating component according to an embodiment of the present invention.

[0025] Figure 2 This is a three-dimensional structural diagram of an axial end face clamping device for a thin-walled rotating part according to an embodiment of the present invention, from another perspective.

[0026] Figure 3 This is a three-dimensional structural diagram from the third perspective of an embodiment of the present invention for an axial end face clamping device for a thin-walled rotating component.

[0027] The correspondence between the numbers and component names in the diagram is as follows: 1 Fixture fixing bracket, 2 Rotary hydraulic cylinder, 3 Connecting bracket, 4 Oil and gas lubrication assembly, 5 Upper positioning assembly, 6 Upper pressure cap, 7 Positioning fixing column, 8 Fixing bracket positioning block, 9 Zero point positioning fixing seat, 10 Bottom mounting seat, 11 Product workpiece, 12 Single arm five-axis assembly. Detailed Implementation

[0028] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0029] This embodiment provides an axial end face clamping device for thin-walled rotating parts, used for clamping impeller workpieces on a CNC machine tool for five-axis machining. The impeller workpiece has an upper end face, a lower end face, and a blade portion located between the upper and lower end faces. The blade portion includes multiple thin-walled blades distributed along the circumferential direction. This device achieves the dual purpose of reducing clamping deformation and avoiding machining interference by applying clamping force to the axial end face of the workpiece rather than the radial side face. The impeller workpiece is hereinafter referred to as product workpiece 11.

[0030] In terms of structural composition, the axial end face clamping device for thin-walled rotating parts in this embodiment mainly includes three parts: a base assembly, an upper clamping assembly, and a force actuator. The three parts work together to achieve axial clamping of the impeller workpiece.

[0031] The base assembly is fixedly mounted on the machining table of the CNC machine tool, providing bottom support and positioning reference for the workpiece. The fixture fixing bracket 1 is the bottom foundation component of the device, in the form of a disc or flange-shaped base, and is bolted to the single-arm five-axis assembly 12 of the CNC machine tool. The single-arm five-axis assembly 12 has an arc-shaped opening, providing clearance for the tool's movement under and to the side of the workpiece. The fixture fixing bracket 1 is used to withstand the cutting forces generated during machining and to fix the entire device to the machine tool. The fixing bracket positioning block 8 is located on the side of the fixture fixing bracket 1, in the form of a rectangular block, and provides auxiliary positioning and anti-rotation constraints when the fixture fixing bracket 1 is installed on the single-arm five-axis assembly 12, ensuring the relative positional accuracy of the entire device and the machine tool.

[0032] The base assembly includes a bottom mounting base 10 and a zero-point positioning fixing base 9. The bottom mounting base 10 is a disc-shaped component, and its upper end surface is precision-machined to form a bottom positioning surface for supporting the lower end surface of the impeller workpiece. The flatness of the bottom positioning surface directly affects the positioning accuracy of the workpiece. In this embodiment, the bottom positioning surface is precision-machined to ensure that the workpiece will not be skewed due to the shape error of the positioning surface itself after clamping. The lower end of the bottom mounting base 10 is mounted on the zero-point positioning fixing base 9 through a repeatable positioning interface. The zero-point positioning fixing base 9 is fixedly mounted on the disc surface of the single-arm five-axis assembly 12 by bolts, forming the quick-change base in the above-mentioned base assembly. The specific structure of the repeatable positioning interface is as follows: multiple positioning modules are provided on the upper surface of the zero-point positioning fixing base 9, and each positioning module has a clamping mechanism inside. A pull stud is fixed at the corresponding position of the lower end of the bottom mounting base 10; when the pull stud is inserted into the positioning module, the clamping mechanism is pneumatically or hydraulically driven to lock the pull stud, thus achieving positioning and clamping at the same time. The zero-point positioning system has high repeatability. When the bottom mounting base 10 is removed from the zero-point positioning fixing base 9 and reinstalled, its spatial position can be restored to the state before disassembly, without the need to perform the dial indicator alignment operation again.

[0033] As another implementation of the quick-change base 9, the repeatable positioning interface adopts a combination structure of positioning pins and bolts. The upper surface of the quick-change base has at least two positioning pin holes, and the lower end of the bottom mounting base 10 has positioning pins corresponding to the positions of the positioning pin holes. During installation, the positioning pins are first inserted into the pin holes to achieve radial and circumferential positioning, and then the bottom mounting base 10 is fastened to the quick-change base with bolts. During disassembly, the bottom mounting base 10 can be removed by loosening the bolts. This method is simple in structure and low in cost, suitable for working conditions with slightly lower positioning accuracy requirements. As yet another implementation, the upper surface of the quick-change base has a T-slot or dovetail groove, and the lower end of the bottom mounting base 10 has a corresponding slider or key. After the slider slides into place along the groove, it is fixed with locking screws. Regardless of the specific structure used, the repeatable positioning interface achieves the same core function: the spatial position of the bottom mounting base 10 can be repeated after disassembly and reinstallation.

[0034] The upper clamping assembly is positioned above the base assembly and is used to apply axial clamping force to the impeller workpiece from its upper end face. The upper clamping assembly includes an upper end cap 6 and an upper end positioning assembly 5. The upper end cap 6 is a disc-shaped component, with its lower end face forming an upper clamping surface for pressing against the upper end face of the impeller workpiece. The upper clamping surface is also precision-machined and maintains a high degree of parallelism with the bottom positioning surface. The disc-shaped shape of the upper end cap 6 allows the clamping force to be uniformly transmitted to the upper end face of the workpiece along the circumferential direction. This circumferential uniformity of the clamping force originates from the geometric symmetry of the disc-shaped component itself—when the force actuator applies axial thrust in the central region of the upper end cap 6, the rigid disc evenly distributes the thrust to various positions on its lower surface, eliminating the need for an additional force-equalizing mechanism. The thickness of the upper end cap 6 is sufficient to ensure that no significant flexural deformation occurs under maximum clamping force.

[0035] The upper positioning component 5 is positioned above the upper pressure cap 6 and is used to guide the upper pressure cap 6 to align with the bottom mounting base 10 during the pressing process, ensuring that the movement direction of the upper pressing surface is always perpendicular to the bottom positioning surface. In one embodiment, the upper positioning component 5 includes a guide sleeve and a guide rod. The guide sleeve is fixed to the fixed part of the device, and the upper end of the guide rod slidably passes through the guide sleeve. The lower end of the guide rod is fixedly connected to the center of the upper end face of the upper pressure cap 6. A precision sliding fit is formed between the inner hole of the guide sleeve and the outer circle of the guide rod. The guide rod slides freely axially within the guide sleeve while being constrained radially and circumferentially, thereby ensuring that the upper pressure cap 6 remains coaxial with the bottom mounting base 10 and that the upper pressing surface is parallel to the bottom positioning surface during movement. As another implementation, the upper positioning component 5 can be a conical centering structure: the lower end of the upper positioning component 5 has an outer conical surface, and the upper end of the upper pressure cap 6 has a corresponding inner conical hole. When the upper pressure cap 6 is pushed downward, the conical surface and the conical hole cooperate to produce an automatic centering effect, guiding the upper pressure cap 6 to a position coaxial with the bottom mounting base 10. This conical centering structure has fewer parts and a self-centering function, completing alignment synchronously during the clamping process.

[0036] As a variant of this embodiment, the guiding function of the upper positioning component 5 can be achieved through a parallel four-bar linkage. This parallel four-bar linkage guiding mechanism includes two sets of vertically parallel connecting rods. One end of each connecting rod is hinged to the fixed part of the device, and the other end is hinged to the upper end of the upper pressure cap 6. The projections of the two sets of connecting rods on the horizontal plane are arranged at a 90° angle, or the four connecting rods are arranged symmetrically in a rectangle. When the force actuator drives the upper pressure cap 6 to move up and down, the parallel four-bar linkage constrains the movement trajectory of the upper pressure cap 6 to a planar movement parallel to the bottom positioning surface. That is, the upper pressing surface remains parallel to the bottom positioning surface throughout the entire movement, and the upper pressure cap 6 does not deflect or tilt. The positioning accuracy of this mechanism depends on the clearance of the connecting rod hinge pairs and the manufacturing accuracy of the connecting rod length. Compared with the guide sleeve and guide rod scheme, the parallel four-bar linkage guiding mechanism is designed without sliding friction pairs, and its guiding accuracy is less likely to decrease due to wear of the sliding surface during long-term use, making it suitable for production lines with high-frequency clamping. Compared to conical centering schemes, the parallel four-bar linkage provides guiding constraints throughout the entire clamping motion, rather than only centering when approaching the clamping position. This helps prevent the upper cap from colliding with the workpiece during descent. As a spatial linkage structure, the parallel four-bar linkage does not occupy the central area of ​​the upper cap, providing greater clearance for tool movement above the workpiece's upper surface and further reducing potential obstruction of the tool's machining path by the clamping components.

[0037] The force actuator is the drive source in this embodiment, used to drive the upper clamping assembly to move towards the bottom positioning surface. The force actuator is a rotary hydraulic cylinder 2, including a cylinder body and a piston rod that can move axially relative to the cylinder body. The cylinder body of the rotary hydraulic cylinder 2 is bolted to the fixture fixing bracket 1. The piston rod extends upward as the output end and is connected to the upper positioning assembly 5 through a connecting bracket 3. The lower end of the connecting bracket 3 is fixedly connected to the upper end of the piston rod of the rotary hydraulic cylinder 2, the upper end of the connecting bracket 3 is fixedly connected to the housing of the oil-air lubrication assembly 4, and the lower end of the housing of the oil-air lubrication assembly 4 is fixedly connected to the guide sleeve of the upper positioning assembly 5. Thus, when oil is introduced into the rotary hydraulic cylinder 2, the piston rod moves downward, and the force is transmitted sequentially through the connecting bracket 3, the housing of the oil-air lubrication assembly 4, the guide sleeve of the upper positioning assembly 5, and the guide rod to the upper end cap 6 at the lower end, causing the upper end cap 6 to move downward. When oil is introduced into the rotary hydraulic cylinder 2 in the reverse direction, the piston rod retracts upward, causing the upper end cap 6 to lift upward and separate from the workpiece.

[0038] As another implementation of the force actuator, a pneumatic cylinder can be used instead of the aforementioned rotary hydraulic cylinder 2. The structure of the pneumatic cylinder is similar to that of the hydraulic cylinder, including a cylinder body and a piston rod, but it uses compressed air as the working medium. The pneumatic cylinder has a fast response speed, simple system configuration, and is clean and pollution-free, making it suitable for light cutting conditions such as impeller finishing. The working pressure of the pneumatic cylinder can be set according to the working conditions. As yet another implementation, the force actuator can be an electric actuator. The electric actuator includes a servo motor, a lead screw pair, and a push rod. The servo motor is fixed to the fixture mounting bracket 1, the lead screw's screw is connected to the motor output shaft via a coupling, the lead screw's nut is fixedly connected to the push rod, and the upper end of the push rod is connected to the connecting bracket 3. The servo motor drives the lead screw to rotate, and the lead screw nut converts the rotational motion into the linear motion of the push rod, pushing the upper clamping assembly to move. The electric actuator has high position control accuracy and can programmably set multiple clamping force levels and stroke positions, facilitating integration with the control system of CNC machine tools and making it suitable for rapid changeover of impellers of different specifications in automated production lines.

[0039] In another embodiment, the position of the force actuator is changed from above the device to below the device. The force actuator is mounted inside the base assembly, with its output end extending upward and drivingly connected to the lower end of the bottom mounting base 10. The bottom mounting base 10 can reciprocate axially under the drive of the force actuator. The upper clamping assembly is fixedly mounted on a fixed bracket above the device, and the position of the upper clamping surface remains unchanged. When clamping the workpiece, the upper end face of the impeller workpiece is abutted against the fixed upper clamping surface, and the force actuator is activated to drive the bottom mounting base 10 and the workpiece on it to move upward until the lower end face of the workpiece is axially clamped by the bottom positioning surface and the upper end face is axially clamped by the upper clamping surface. When releasing, the force actuator drives the bottom mounting base to retract downward, releasing the workpiece. The force transmission path of this variant is the opposite of the original embodiment, but the two are completely equivalent in mechanical principle—the workpiece is axially clamped between the upper clamping surface and the bottom positioning surface in both cases. The force actuator of this variant is located at the bottom of the device, which lowers the overall center of gravity of the device and helps to reduce the vibration of the device caused by the movement of the machine tool turntable in five-axis machining. At the same time, the upper clamping assembly is a fixed structure with no moving pipes passing through it, making the upper part of the device simpler and providing more space for the tool to move in the area above the workpiece.

[0040] The hydraulic system is equipped with an oil-air lubrication assembly 4. The oil-air lubrication assembly 4 includes a metering distributor and a mixing unit. Compressed air and pressurized oil enter the mixing unit and mix to form an oil-air mixture. This mixture is then delivered through pipelines to the sliding surface of the piston rod of the rotary hydraulic cylinder 2 and the mating surface of the guide sleeve and guide rod of the upper positioning assembly 5. An oil film is formed on the sliding surface to lubricate and reduce friction. At the same time, a small amount of oil-air escapes from the gaps in the sliding surface to form a positive pressure air curtain, preventing cutting fluid and chips from entering the moving parts and achieving a dustproof seal.

[0041] The force transmission path between the force actuator, the upper clamping assembly, and the base assembly is as follows: The force actuator generates axial thrust, which is transmitted to the upper end cap 6 via the connecting bracket 3, the housing of the oil-air lubrication assembly 4, and the upper positioning assembly 5. The upper clamping surface of the upper end cap 6 applies the force to the upper end face of the workpiece 11. The lower end face of the workpiece 11 is supported by the reaction force provided by the bottom positioning surface of the bottom mounting base 10. Thus, the workpiece 11 is axially clamped between the upper clamping surface and the bottom positioning surface. Since the clamping force is applied to the axial end face of the workpiece rather than the radial side, the blade portion of the workpiece remains fully exposed in the clamped state, allowing the five-axis tool to approach the blade surface from any angle in the radial direction for machining.

[0042] To further improve the structural rigidity under clamping conditions, the device in this embodiment also includes a rigid positioning component. The rigid positioning component includes a positioning fixing post 7 and a slot. The positioning fixing post 7 is vertically fixed to the side of the connecting bracket 3, and its lower end has a conical or spherical head. A corresponding slot is formed on the upper surface of the zero-point positioning fixing seat 9, and a guide slope is provided at the entrance of the slot. When the force actuator drives the upper clamping component downwards to the clamping position, the lower end of the positioning fixing post 7 is precisely engaged in the slot, forming a mechanical rigid constraint. This rigid constraint provides additional support after the clamping state is established. Even if the hydraulic system pressure drops slightly during machining, the mechanical cooperation between the positioning fixing post 7 and the slot can still maintain the relative positional accuracy between the upper clamping component and the base component, which is beneficial for suppressing vibration under heavy cutting or intermittent cutting conditions. After machining is completed, the force actuator moves in the opposite direction, causing the upper clamping component to lift upwards, and the positioning fixing post 7 moves upwards and disengages from the slot, releasing the rigid constraint.

[0043] As another arrangement of the rigid positioning component, the positioning post can be set on the base assembly, and the slot is formed in the moving part. When the upper clamping component moves downward to the clamping position, the slot on the moving part engages with the positioning post on the base assembly, thus achieving rigid mechanical constraint. In another embodiment, the rigid positioning component does not use a positioning post and slot mating structure, but instead uses a wedge locking mechanism. This wedge locking mechanism includes a wedge-shaped locking block, a wedge-shaped groove, and a release spring. The wedge-shaped locking block is set in the moving part that is linked to the force actuator. The outer surface of the wedge-shaped locking block is inclined, which has a self-locking characteristic. The wedge-shaped groove is formed in the base assembly, and the inner surface of the groove has an inclined surface that matches the wedge-shaped locking block. When the force actuator drives the upper clamping component to move downward to the clamping position, the wedge-shaped locking block wedges into the wedge-shaped groove. The frictional self-locking effect between the inclined surfaces forms a mechanical lock between the moving part and the base assembly that prevents relative displacement in the axial and circumferential directions. When the force actuator moves in the opposite direction to release the clamping, the wedge-shaped locking block moves upward with the moving part and disengages from the wedge groove. The release spring assists in pushing the wedge-shaped locking block out of the wedge groove to prevent jamming. Compared with the positioning pin slot solution, the wedge block locking mechanism utilizes the inclined plane friction self-locking principle, which can achieve a larger locking contact area and higher locking rigidity under the same external dimensions, making it particularly suitable for large depth of cut milling operations.

[0044] In terms of adapting to workpieces of various specifications, both the bottom mounting base 10 and the upper pressure cover 6 in this embodiment are configured to be detachable and replaceable from the device. The bottom mounting base 10 is detached and replaced as follows: unlock the positioning module of the zero-point positioning fixing base 9, remove the current bottom mounting base 10, replace it with another bottom mounting base 10 corresponding to the specifications of the impeller to be processed, insert the pull pin at its lower end into the positioning module, and lock it. The upper pressure cover 6 is detached and replaced as follows: loosen the connecting bolt between the upper pressure cover 6 and the lower guide rod of the upper positioning component 5, remove the current upper pressure cover 6, replace it with an upper pressure cover 6 corresponding to the specifications of the impeller to be processed, and lock the bolt. The replacement operation can be completed in a significantly shorter time than traditional alignment methods.

[0045] In another embodiment, to reduce manufacturing costs and structural complexity, the independent upper positioning component 5 is omitted, and the upper clamping component consists only of the upper pressure cap 6. The output end of the force actuator is directly and fixedly connected to the upper pressure cap 6 via a connecting bracket, and the alignment accuracy of the upper pressure cap 6 is entirely guaranteed by the guiding accuracy of the force actuator itself. During installation, through a one-time assembly and adjustment, the upper clamping surface of the upper pressure cap 6 is aligned with the bottom positioning surface of the bottom mounting base 10, and the central axis of the upper pressure cap is coaxial with the central axis of the bottom mounting base. After adjustment, all connecting parts are locked. This variant is suitable for scenarios with moderate machining accuracy requirements and limited budgets.

[0046] For batch processing scenarios with lower precision requirements but high cost sensitivity, the flatness and parallelism of the bottom positioning surface and the upper clamping surface, as well as the repeatability of positioning between the quick-change base and the bottom mounting base, can be appropriately relaxed. This reduction in precision level allows the bottom mounting base and the upper pressure cap to be machined using conventional precision grinding, and the positioning module of the zero-point positioning fixture can use a standard precision level, significantly reducing manufacturing costs. The hydraulic system's working pressure can be set in stages according to the processing conditions to adapt to clamping requirements under different cutting loads, while further reducing the risk of deformation of thin-walled end faces with low clamping force.

[0047] The working process of this embodiment is described in detail below.

[0048] Before clamping begins, the corresponding bottom mounting base 10 and upper end cap 6 are selected according to the specifications of the impeller to be processed, and installed on the device. The bottom mounting base 10 is inserted into the positioning module of the zero-point positioning fixing base 9 by means of a pull pin and pneumatically locked; the upper end cap 6 is fixed to the guide rod at the lower end of the upper positioning assembly 5 by bolts. These operations can be completed offline on the worktable outside the machine tool. In mass production, while the operator is processing the current workpiece on the machine tool, the bottom mounting base 10 and upper end cap 6 required for the next workpiece are prepared in advance outside the machine tool, and the next blank can even be pre-placed on the bottom positioning surface of the bottom mounting base 10.

[0049] When clamping the workpiece, first ensure the force actuator is in the released state. Place the lower end face of the impeller workpiece on the bottom positioning surface of the bottom mounting base 10, ensuring full contact between the lower end face of the workpiece and the bottom positioning surface. The lower end face of the workpiece and the bottom positioning surface are in surface contact, and the workpiece is held in place by gravity or operator assistance. Then, start the rotary hydraulic cylinder 2 to supply oil, causing the piston rod to move downwards, driving the upper end cap 6 downwards via the connecting bracket 3, the oil-air lubrication assembly 4, and the upper end positioning assembly 5. During this movement, the upper end positioning assembly 5 guides the upper end cap 6 to move in a direction perpendicular to the bottom positioning surface, maintaining the upper clamping surface parallel to the bottom positioning surface. The upper clamping surface continues to move downwards until it contacts the upper end face of the impeller workpiece, and under the continuous driving force of the rotary hydraulic cylinder 2, axially clamps the workpiece between the upper clamping surface and the bottom positioning surface. At this time, the disc-shaped lower end face of the upper end cap 6 evenly transmits the clamping force circumferentially to the upper end face of the workpiece, and the bottom positioning surface of the bottom mounting base 10 evenly bears the reaction force from the lower end face of the workpiece. At the same time, the positioning and fixing post 7 of the rigid positioning component moves downward with the moving part, and its lower conical head is inserted into the slot of the zero-point positioning and fixing seat 9 to complete the auxiliary rigid positioning in the clamping state.

[0050] After clamping, the CNC machine tool drives the cutting tool to machine the impeller blades according to the preset machining program. Since the clamping force is applied axially to the upper and lower surfaces of the workpiece, and there are no clamping components obstructing the radial side of the blades, the cutting tool can cut from any angle. Five-axis simultaneous machining can complete the finishing of all blades in one operation, including the suction surface, pressure surface, leading edge, and trailing edge contours, without requiring changes in clamping position or re-clamping. During machining, cutting fluid and chips may splash onto the moving parts of the device; the oil-air lubrication assembly 4 continuously supplies an oil-air mixture that forms a positive pressure air curtain at the moving mating surfaces, preventing contaminants from entering.

[0051] After processing, the rotary hydraulic cylinder 2 reverses oil flow, causing the piston rod to retract upwards. This sequentially drives the connecting bracket 3, the oil-air lubrication assembly 4, the upper positioning assembly 5, and the upper pressure cap 6 to move upwards. The upper clamping surface separates from the upper surface of the workpiece, and the positioning and fixing post 7 disengages from the slot. The device enters the release state, allowing the operator to remove the processed workpiece.

[0052] If you need to continue processing workpieces of the same specifications, you can directly place the next blank and repeat the above clamping and processing steps. If you need to change the processing specifications, first take out the current workpiece, unlock the zero-point positioning fixing seat 9, remove the current bottom mounting seat 10, and install the pre-assembled component with the new specification bottom mounting seat 10 and the upper pressure cover 6. You can then quickly start processing the new specification workpiece.

[0053] This device is not only suitable for impeller workpieces, but also for machining other components with an upper end face, a lower end face, and a radial thin-walled structure located between the upper and lower end faces, such as turbine disks, integral impellers, guide vanes, etc.

[0054] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An axial end face clamping device for thin-walled rotating parts, used for clamping workpieces on a CNC machine tool, the workpiece having an upper end face, a lower end face, and a thin-walled structural portion located between the upper end face and the lower end face, characterized in that, include: A base assembly is fixedly installed on the CNC machine tool, and the base assembly has a bottom positioning surface for supporting the lower end face of the workpiece; The upper clamping assembly has an upper clamping surface for pressing against the upper end face of the workpiece; A force actuator is driven and connected to the upper clamping assembly. The force actuator is configured to drive the upper clamping surface to move in the direction of the bottom positioning surface, so that the workpiece is axially clamped between the upper clamping surface and the bottom positioning surface.

2. The axial end face clamping device for thin-walled rotating parts according to claim 1, characterized in that, The force actuator is a fluid pressure driven cylinder mechanism, which has a cylinder and an output end that can move axially relative to the cylinder, and the output end is connected to the upper clamping assembly.

3. The axial end face clamping device for thin-walled rotating parts according to claim 2, characterized in that, The fluid pressure driven cylinder mechanism is a hydraulic cylinder or a pneumatic cylinder.

4. The axial end face clamping device for thin-walled rotating parts according to claim 1, characterized in that, The force actuator includes an electric push rod, which is driven by a motor to convert rotational motion into linear motion to drive the upper clamping assembly.

5. The axial end face clamping device for a thin-walled rotating part according to any one of claims 1-4, characterized in that, The base assembly includes a bottom mounting base (10), the bottom positioning surface being formed on the top surface of the bottom mounting base (10); the upper pressing assembly includes an upper end cap (6), the upper pressing surface being formed on the bottom end surface of the upper end cap (6).

6. The axial end face clamping device for thin-walled rotating parts according to claim 5, characterized in that, The bottom mounting base (10) and / or the upper end cap (6) are configured to be detachable and replaceable from the device to accommodate workpieces with different upper and / or lower end dimensions.

7. The axial end face clamping device for thin-walled rotating parts according to claim 5, characterized in that, It also includes an upper positioning component (5), which is disposed above the upper cover (6) and is used to guide the upper cover (6) to be aligned relative to the bottom mounting base (10).

8. The axial end face clamping device for thin-walled rotating parts according to claim 5, characterized in that, The base assembly also includes a quick-change base (9), which is fixedly installed on the machining table of the CNC machine tool, and the bottom mounting base (10) is installed on the quick-change base (9) in a repeatable positioning manner.

9. The axial end face clamping device for thin-walled rotating parts according to claim 5, characterized in that, It also includes a rigid positioning component, which includes a positioning fixing post (7) and a slot. One of the positioning fixing post (7) and the slot is disposed in the moving part that is linked with the force actuator, and the other is disposed in the base assembly. The positioning fixing post (7) is inserted into the slot as the force actuator drives the upper clamping component to axially clamp the workpiece, so as to achieve rigid positioning of the upper clamping component relative to the base assembly in the clamping state.

10. A clamping method using the axial end face clamping device for thin-walled rotating parts according to any one of claims 1-9, characterized in that, include: Place the lower end face of the workpiece on the bottom positioning surface; The force actuator drives the upper clamping assembly to move toward the bottom positioning surface, so that the upper clamping surface presses against the upper end surface of the workpiece, thereby axially clamping the workpiece between the upper clamping surface and the bottom positioning surface; When the workpiece is axially clamped, the radial side of the thin-walled structure of the workpiece is not obstructed by clamping elements.

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