Accurate control clamp for shaft and machining control method thereof

Abstract

The application provides a shaft precision control clamp and a machining control method thereof. The shaft precision control clamp comprises a support module which is a cylindrical structure; a split shaft which is coaxially fixed at one end of the support module, has a first through hole penetrating in the axial direction, and is divided into multiple parts in the axial direction; a tapered expansion shaft which has a tapered surface on the outer surface and is installed in cooperation with the tapered hole, has a second through hole penetrating in the axial direction; and a pull rod which is arranged in the second through hole, is fixed at one end of the tapered expansion shaft, extends out of the other end of the tapered expansion shaft, and is connected with an electric push rod. The machining precision is continuously adjusted by the tapered surface, and the force is adjusted by the electric push rod, so that the technical problem of insufficient machining precision control force under the condition of compatibility of different sizes in the prior art is solved.

Description

Technical fields: This invention relates to the field of shaft machining fixture structure design technology, and in particular to a precision control fixture for shafts and its machining control method. Background technology: Currently, in the field of composite material shaft parts machining, expansion clamps, as the core tooling for precise clamping based on the inner diameter, have always focused their technological development on three core requirements: "force control accuracy, dimensional adaptation, and material compatibility." Existing technical solutions mainly draw on experience with metal shaft expansion clamps and make localized improvements based on the characteristics of composite materials, but a systematic solution has not yet been formed.

[0001] From the perspective of tubular or shaft expansion clamping technology, mainstream solutions include three categories: hydraulic drive, elastic deformation, and adaptive positioning. For example, hydraulic internal expansion clamping chucks use hydraulic oil to drive the expansion of a flexible inner cavity to clamp the profile, avoiding surface damage from hard friction. This is suitable for precision machining of metal shafts. However, composite materials have poor thermal conductivity, and the expansion process can easily cause local temperature rise, leading to thermal stress damage to the interlayer bonding strength. Elastic sleeve expansion clamping fixtures use the principle of conical expansion, controlling the expansion force by adjusting the position of the pressure block. This is suitable for thin-walled parts, but the fixed size of the expansion sleeve cannot meet the frequent shape change requirements in composite material processing. Axial attitude adaptive array composite tube clamping devices achieve angle adaptation through retractable jaws and spherical bearings, solving the problem of composite tube axis floating. However, they do not involve rapid shape change functionality, resulting in low shape change efficiency and making them unsuitable for machine tool processing.

[0002] The machining and clamping of composite material shafts places higher demands on expansion clamps, and their special characteristics are reflected in three aspects: Firstly, there is the rigid requirement for internal support and positioning. Composite material shafts (such as carbon fiber / epoxy resin shafts) are typically formed by winding or laying up mandrels. Their inner surface dimensional accuracy can reach the micrometer level, and the surface is smooth. During machining, positioning must be achieved using the inner surface as a reference. Traditional expansion clamps (such as external cylindrical jaws or hydraulic expansion sleeves for metal shafts) cannot adapt to the inner surface reference and must rely on external support structures. In addition, the inner surface of the composite material shaft is the only machining reference, requiring the expansion clamp to directly fit against the inner surface through an internal support structure to avoid external forces interfering with the accuracy of the reference surface. However, existing internal expansion clamps are mostly designed for metal shafts and tubes, and do not consider the easy scratching characteristics of the inner surface of composite materials. Uneven distribution of support force can easily lead to local crushing.

[0003] Secondly, there are stringent requirements for surface protection and force control accuracy. The surface of composite shafts (especially carbon fiber layups) has low compressive strength and significant anisotropy. Traditional tightening techniques (such as elastic sleeve conical expansion or hydraulic cylinder constant pressure drive) are prone to interlayer delamination or surface indentation due to uncontrollable force distribution. Therefore, it is necessary to introduce a closed-loop force control system (such as Hall effect sensors for real-time displacement monitoring) and an adaptive pressure compensation algorithm (such as clamping force optimization based on genetic algorithms) to achieve dynamic adjustment of the tightening force and effectively improve repeatability.

[0004] Thirdly, there is the need for rapid response in high-frequency size adaptation. Composite material shafts often require mixed-size production lines. Traditional expansion clamps require manual adjustment of the segment spacing or replacement of the entire segment expansion sleeve, resulting in long turnaround times and severely limiting production capacity. Some expansion sleeves support variable diameters through linkage mechanisms, but these have many parts and the connection points rely on bolts or cylindrical pins for fastening, and the positioning error cannot meet the machining accuracy requirements of composite material shafts. This patent aims to resolve the contradiction between multi-size compatibility and high-precision positioning, for example, by using magnetic quick-change expansion claws to achieve rapid turnaround for various shaft diameter specifications.

[0005] There is an urgent need for a precision control fixture for shafts and its machining control method, which would help solve the technical problem of insufficient machining accuracy control under different size compatibility conditions in the existing technology. Summary of the Invention: In one embodiment, the present invention provides a precision control fixture for shafts, which continuously adjusts the machining accuracy through a conical surface and adjusts the force through an electric push rod, thereby helping to solve the technical problem of insufficient machining accuracy control force under conditions of compatibility with different sizes in the prior art.

[0006] The precision control fixture for the shaft includes: One support module, which is a cylindrical structure; A split shaft, one end of which is coaxially fixed to one end of the support module, the split shaft has a first through hole that extends along the axial direction, one end of the first through hole has a tapered hole, and the split shaft is divided into multiple petals along the axial direction. An expansion tapered shaft has an outer surface that is tapered, and the tapered surface is fitted with a tapered hole. The expansion tapered shaft has a second through hole that extends axially. A pull rod is disposed in the second through hole. One end of the pull rod is fixed to one end of the expansion cone shaft, and the other end of the pull rod extends out of the expansion cone shaft and is connected to an electric push rod so that the multi-lobed segmented shaft can be expanded or contracted when the electric push rod moves axially.

[0007] In one embodiment, one end of the expansion cone shaft is fixed to one end of the pull rod by a pressure plate.

[0008] In one embodiment, the electric actuator is driven by a servo motor and has a built-in high-precision grating ruler with a displacement accuracy of 0.001mm and a displacement control error of ≤0.01mm.

[0009] In one embodiment, the conical hole of the split shaft is a 1:50 conical surface, the outer wall is a cylindrical surface adapted to the inner hole of the product to be processed, the diameter tolerance is h6, and the surface roughness is Ra0.8.

[0010] In one embodiment, the outer wall of the tapered surface of the expansion tapered shaft is a 1:50 conical surface, quenched with 42CrMo, and the tapered surface is ground to a surface roughness of Ra0.4. The outer circle is plated with hard chrome with a layer thickness of 0.02mm.

[0011] In one embodiment, a 3mm thick polyurethane cushioning pad with a Shore hardness of 90HA is attached to the inner side of the pressure plate, and the pressure plate has anti-slip texture.

[0012] In one embodiment, the split shaft is made of 7075-T6 aluminum alloy with a tensile strength of 570MPa and a density of 2.8g / cm³. The inner wall of the conical hole is nitrided to a depth of 0.1mm, with a surface hardness of HV900. The outer cylindrical surface is precision machined and ground, with a cylindricity ≤0.005mm.

[0013] In one embodiment, the piezoelectric force sensor has a range of 0-2000N and an accuracy of ±1N.

[0014] In one embodiment, the servo motor has a rated thrust of 1500-3000N and an axial travel of 5-10mm.

[0015] In one embodiment, the present invention also provides a machining control method for a precision control fixture for shafts, the precision control method for the precision control fixture for shafts comprising: The outer edge of the support module is coaxially aligned with the inner edge of the cylindrical product to be processed, thus achieving centering. The CNC system sends a command, and the electric push rod pushes the pull rod so that the expansion cone shaft moves axially, the segmented shaft expands radially, and finally the CNC center performs milling / grinding. Attached image description: Figure 1 This is a cross-sectional schematic diagram of a shaft precision control fixture in one embodiment of the present invention; Figure 2 This is a side view schematic diagram of the segmented structure in another embodiment of the present invention. Specific implementation examples: To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Various embodiments and features of this application are described herein with reference to the accompanying drawings.

[0018] These and other features of this application will become apparent from the following description of preferred forms of embodiments given as non-limiting examples, with reference to the accompanying drawings.

[0019] It should also be understood that although this application has been described with reference to some specific examples, those skilled in the art can certainly implement many other equivalent forms of this application, which have the features described in the claims and are therefore all within the scope of protection defined herein.

[0020] The above and other aspects, features and advantages of this application will become more apparent when taken in conjunction with the accompanying drawings and in view of the following detailed description.

[0021] Specific embodiments of this application are described below with reference to the accompanying drawings; however, it should be understood that the claimed embodiments are merely examples of this application, which can be implemented in various ways. Well-known and / or repeated functions and structures are not described in detail to ascertain the true intent based on the user's historical operations, and to avoid unnecessary or redundant details that would obscure this application. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as the basis and representative basis for the claims to teach those skilled in the art to use this application in various ways with substantially any suitable detailed structure.

[0022] This specification may use the phrases “in one embodiment,” “in another embodiment,” “in yet another embodiment,” or “in other embodiments,” all of which may refer to one or more of the same or different embodiments according to this application.

[0023] To address the aforementioned issues, this invention provides a precision-controlled, interchangeable-size expansion clamping fixture for composite material shafts. The purpose of this invention is to overcome the path dependence of existing composite material shaft expansion clamping fixtures on metal processing experience, systematically resolving their core deficiencies in force control accuracy, dimensional adaptation, and material compatibility, thereby meeting the specific needs of composite material shaft processing. Specifically, it aims to address the positioning rigidity requirement of composite material shafts with the inner surface as the sole reference by optimizing the internal support structure design to achieve a damage-free fit with the inner surface, avoiding surface crushing or scratches caused by uneven support force. Addressing the low compressive strength and anisotropic characteristics of composite material surfaces, a dynamic force control mechanism and adaptive pressure adjustment are introduced to replace traditional constant pressure drives, preventing interlayer peeling or indentation and improving force control accuracy and repeatability. For the high-frequency changeover requirements of multi-specification mixed-line production, a flexible adaptation system is constructed to simplify the changeover process, shorten processing time, and resolve the contradiction between multi-size compatibility and high-precision positioning. Ultimately, a dedicated expansion and tightening system for composite material shaft machining was developed, achieving precise protection of the inner surface reference, intelligent control of the expansion and tightening force, and rapid response to multiple shaft diameter specifications, providing reliable tooling support for the efficient and precise machining of composite material shaft parts.

[0024] In one embodiment, Figure 1 This is a cross-sectional schematic diagram of a shaft precision control fixture in one embodiment of the present invention; Figure 2 This is a side view schematic diagram of the segmented structure in another embodiment of the present invention. Figures 1 to 2 As shown, in one embodiment, the present invention provides a precision control fixture for a shaft, the precision control fixture for a shaft comprising: One support module 5, which is a cylindrical structure; A split shaft 2, one end of which is coaxially fixed to one end of the support module 5, the split shaft 2 has a first through hole 21 extending along the axial direction, and one end of the first through hole 21 has a tapered hole 22. An expansion tapered shaft 4 has an outer surface that is a tapered surface 41, and the tapered surface 41 is fitted with the tapered hole 22. The expansion tapered shaft 4 has a second through hole 42 that extends axially. A pull rod 3 is disposed in the second through hole 42. One end of the pull rod 3 is fixed to one end of the expansion cone shaft 4, and the other end of the pull rod 3 extends out of the expansion cone shaft 4 and is connected to the electric push rod 1, so that the multi-lobed segmented shaft 2 can be expanded or contracted when the electric push rod 1 moves axially. The pull rod 3 axially connects the electric push rod 1 and the expansion cone shaft 4, transmitting axial driving force.

[0025] This embodiment provides a specific implementation of a replaceable size precision control expansion clamp for composite material shafts. Through the synergistic constraint structure of "inner hole expansion + outer circle support", modular quick-change design and electronically controlled precision drive, high-precision and flexible clamping of composite material shafts is achieved.

[0026] Expansion tapered shaft 4: The outer wall is a conical surface, which contacts and fits with the inner wall of the tapered hole of the split shaft 2. Through the force conversion of "axial displacement → radial expansion", the split shaft 2 is driven to expand / contract radially.

[0027] In one embodiment, one end of the expansion cone shaft 4 is fixed to one end of the pull rod 3 by a pressure plate 6.

[0028] In one embodiment, the electric push rod 1 is driven by a servo motor and has a built-in high-precision grating ruler with a displacement accuracy of 0.001mm and a displacement control error of ≤0.01mm.

[0029] In one embodiment, the conical hole 22 of the split shaft 2 is a 1:50 conical surface, and the outer wall is a cylindrical surface adapted to the inner hole of the product to be processed, with a diameter tolerance of h6 and a surface roughness of Ra0.8. The split shaft 2 has a "multi-lobed conical hole sleeve" structure, with a conical surface on the inner wall and a cylindrical surface on the outer wall adapted to the mounting surface of the support module 5, and is the actuating carrier for radial expansion.

[0030] In one embodiment, the outer wall of the tapered surface of the expansion tapered shaft 4 is a 1:50 conical surface, quenched with 42CrMo, and the tapered surface is ground to a surface roughness of Ra0.4. The outer circle is plated with hard chrome with a layer thickness of 0.02mm.

[0031] In one embodiment, a 3mm thick polyurethane buffer pad with a Shore hardness of 90HA is attached to the inner side of the pressure plate 6, and the pressure plate 6 has anti-slip texture. Pressure plate 6: used for axial pre-compression of the product 7 to be processed, forming a "radial + axial" double constraint with the expansion tapered shaft 4.

[0032] In one embodiment, the split shaft 2 is made of 7075-T6 aluminum alloy with a tensile strength of 570MPa and a density of 2.8g / cm³. The inner wall of the conical hole is nitrided to a depth of 0.1mm and has a surface hardness of HV900. The outer cylindrical surface is precision turned and ground, with a cylindricity ≤0.005mm.

[0033] In one embodiment, the piezoelectric force sensor has a range of 0-2000N and an accuracy of ±1N.

[0034] In one embodiment, the servo motor has a rated thrust of 1500-3000N and an axial travel of 5-10mm.

[0035] In one embodiment, the present invention also provides a machining control method for a precision control fixture for shafts, the precision control method for the precision control fixture for shafts comprising: The outer edge of the support module 5 is coaxially aligned with the inner edge of the cylindrical product to be processed. The CNC system sends a command, and the electric push rod 1 pushes the pull rod 3 so that the expansion cone shaft 4 moves axially, and the split shaft 2 expands radially. Finally, the CNC center performs milling / grinding.

[0036] Support module 5: Equipped with a support surface adapted to the outer diameter of the product 7 to be processed, providing radial support and serving as a reference surface for CNC machining, achieving axial positioning. It can be replaced according to different product dimensions. The connection point with the split shaft 2 can also be magnetically attached, improving fixture change efficiency. When this fixture is not used for machining positioning and only needs to support the product, the outer diameter support surface can be replaced with multiple rotatable rods for flexible support of the product to be processed.

[0037] Product 7 to be processed: the composite material shaft to be clamped, with its inner wall fitting against the support surface of support module 5 to achieve positioning.

[0038] Key technological innovations and collaborative principles; Precise tension control technology: The electric push rod 1 receives instructions from the CNC system and pushes / pulls the tensioning cone shaft 4 to move axially. When the tensioning cone shaft 4 moves towards the segmented shaft 2, the "cone surface transmission ratio" is used to convert the small axial displacement into a large radial expansion of the segmented shaft 2. Due to the constraint of the conical surface, the multiple segments of the segmented shaft 2 expand outward synchronously, and through "multi-point uniform contact", they hold the inner wall of the product to be processed 7, achieving "stress-free and uniform tensioning". When moving in the opposite direction, the segmented shaft 2 elastically contracts, completing the unloading.

[0039] Modular quick-change adaptation technology: The support module 5 and the split shaft 2 adopt a standardized quick-change interface, such as a positioning pin + bolt connection or a magnetic connection. For composite material shafts with different inner diameters and lengths, only the following need to be replaced: ① the split shaft 2 that matches the inner hole of the product to be processed; ② the support module 5 that matches the outer circle of the product to be processed and the processing datum.

[0040] Two-way constrained low deformation technology: The positioning of the product 7 to be processed relies on the dual reference of "inner hole-outer circle": the inner hole is radially constrained by the outer cylindrical surface of the split shaft 2, and the outer circle is radially and axially constrained by the support surface of the support module 5; the pressure plate 6 further applies axial preload, which forms "symmetrical mechanical balance" with the radial expansion force of the expansion tapered shaft 4, completely eliminating the deformation risk caused by the traditional "single-sided rigid clamping".

[0041] The core structure and working logic are as follows: Overall structural composition This fixture moves sequentially along the axial direction of the composite material to be processed and includes the following core functional components: Electric linear actuator 1: As a power source, it outputs controllable axial displacement (displacement accuracy ≤0.01mm), enabling digital control of the tension force. Electric linear actuator 1 incorporates a displacement sensor and force feedback module, which can collect axial displacement and tension force data in real time. It can then be linked with CNC machining centers, industrial robots, and other equipment to achieve fully automated operation of the entire process: "pre-setting clamping parameters (such as tension force threshold and displacement) → precise closed-loop control of tension force → automatic unloading after machining." The tension force adjustment accuracy reaches ±1N, and the repeatability is ≤0.01mm, meeting the precision machining requirements of aerospace-grade composite material components.

[0042] Beneficial effects: Compared to existing technologies, this invention achieves four core breakthroughs through structural innovation and optimized control strategies: Composite material friendly clamping: The symmetrical constraint of "inner hole expansion + outer circle support" and uniform expansion force distribution reduce the clamping deformation of composite material shafts to within 0.02mm, completely solving processing defects such as delamination and cracking (the deformation of traditional clamps is usually ≥0.1mm). Multi-size flexible adaptation: The modular quick-change structure allows one set of fixtures to cover ≥3 specifications of composite material shafts, reducing equipment investment costs by 70% and reducing production line changeover time to within 10 minutes; Precision controllability and automation: Electric control drive + displacement / force feedback closed-loop control, tension force adjustment accuracy reaches ±1N, and with the CNC system, unmanned clamping is realized, and the processing efficiency is increased by more than 3 times; Versatility and economy: Standardized design of core components, quick replacement of vulnerable parts such as support modules and split shafts (maintenance time ≤ 30 minutes), reducing overall operation and maintenance costs by 60%.

[0043] In summary, this invention solves the industry pain points of "difficult deformation control, difficult size matching, and difficult automation compatibility" in the field of composite material shaft clamping, and provides an efficient and flexible clamping solution for the precision machining of high-end composite material components, which has significant industrial promotion value.

[0044] (a) Electric linear actuator (power source) Selection and performance: It adopts a servo electric actuator, with built-in high-precision grating ruler (displacement accuracy 0.001mm) and piezoelectric force sensor (range 0 - 2000N, accuracy ±1N); rated thrust 1500 - 3000N (adapted to shaft diameter), axial travel 5 - 10mm, displacement control error ≤0.01mm.

[0045] Installation and protection: Secured by the flange of the base, the exposed section of the push rod is fitted with a nylon protective sleeve and a silicone sealing ring to prevent chips and coolant from entering.

[0046] Control logic: Receives pulse commands from the CNC system to achieve "displacement / force dual closed loop" - priority force closed loop (to avoid overload damage to composite materials), and displacement closed loop to compensate for mechanical backlash.

[0047] (ii) Split shaft (radial expansion actuator) Structural design: A 4-lobed tapered bushing is adopted (3 lobes for small diameter shafts, 6 lobes for large diameter shafts, and 4 lobes in this case). The inner wall is a 1:50 conical surface, and the outer wall is a cylindrical surface that matches the inner hole of the product to be processed (diameter tolerance h6, surface roughness Ra0.8).

[0048] Materials and processes: The main body is made of 7075-T6 aluminum alloy (tensile strength 570MPa, density 2.8g / cm³), the inner wall of the conical hole is nitrided (layer depth 0.1mm, surface hardness HV900), and the outer cylindrical surface is precision turned and ground (cylindricity ≤0.005mm).

[0049] (iii) Tie rod (axial force transmission) Structure and materials: 45 steel quenched and tempered stepped shaft, one end is provided with external thread (connected to the threaded hole of the electric push rod), and the other end is provided with a positioning step (fitting with the expansion tapered shaft).

[0050] (iv) Tightening conical shaft (core of force conversion) Structural design: The outer wall is a 1:50 conical surface (matching the cone hole of the split shaft), and a limiting step is provided at the large end (to prevent axial movement during expansion).

[0051] Materials and processes: The main body is made of 42CrMo quenched material, the conical surface is ground (surface roughness Ra0.4), and the outer circle is plated with hard chrome (layer thickness 0.02mm, wear-resistant and corrosion-resistant).

[0052] (v) Support module (axial support and positioning) Quick-change interface: cylindrical pin + bolt double positioning; bottom positioning boss (fits with the base positioning groove, coaxiality ≤0.01mm).

[0053] Support surface: Surface polished (surface roughness Ra0.4, contact rate ≥80%).

[0054] Modular grouping: Grouped by the inner diameter of the product.

[0055] (vi) Pressure plate (axial preload) Structure and materials: 45 steel tempered steel plate, with a 3mm thick polyurethane cushioning pad (Shore hardness 90HA, anti-slip texture) on the inside, pre-tightened by bolts and torque wrench.

[0056] Pre-compression logic: After the product is loaded, the pressure plate first restricts axial movement, and then the expansion cone shaft applies radial force to form "double constraint".

[0057] (vii) Working principle that can be promoted The fixture is linked with the CNC machining center to achieve full automation of "clamping → machining → unloading": Feeding: The robotic arm inserts the product into the split shaft, with the outer circle fitting against the support surface of the support module and the inner hole aligning with the outer cylindrical surface of the split shaft.

[0058] Tightening: The CNC system sends a command (e.g., tightening force 1000N), the electric push rod pushes the pull rod → the tightening cone shaft moves axially → the split shaft tightens radially (force sensor closed loop, error ≤ ±1N); the displacement sensor monitors the tightening amount (e.g., target 0.1mm, corresponding to inner hole fit rate ≥95%).

[0059] Machining: CNC center performs milling / grinding, support module suppresses vibration, split shaft with "multi-point contact" ensures uniform cutting force, and product ellipticity ≤0.02mm.

[0060] Unloading: Electric push rod resets → split shaft retracts → robotic arm picks up material, completing the process.

[0061] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A precision control fixture for a shaft, characterized by, The precision control fixture for the shaft includes: A support module (5) is a cylindrical structure; A split shaft (2) has one end coaxially fixed to one end of the support module (5). The split shaft (2) has a first through hole (21) that extends along the axial direction. One end of the first through hole (21) has a tapered hole (22). The split shaft (2) is divided into multiple petals along the axial direction. An expansion tapered shaft (4) has an outer surface that is a tapered surface (41), and the tapered surface (41) is fitted with the tapered hole (22). The expansion tapered shaft (4) has a second through hole (42) that extends axially. A pull rod (3) is disposed in the second through hole (42). One end of the pull rod (3) is fixed to one end of the expansion cone shaft (4). The pull rod (3) extends out of the other end of the expansion cone shaft (4) and is connected to the electric push rod (1) so that the multi-lobed split shaft (2) can be expanded or contracted when the electric push rod (1) moves axially.

2. The precision control fixture for shafts according to claim 1, characterized in that, One end of the expansion cone shaft (4) is fixed to one end of the pull rod (3) via a pressure plate (6).

3. The precision control fixture for shafts according to claim 2, characterized in that, The electric push rod (1) is driven by a servo motor and has a built-in high-precision grating ruler with a displacement accuracy of 0.001mm and a displacement control error of ≤0.01mm.

4. The precision control fixture for shafts according to claim 3, characterized in that, The conical hole (22) of the split shaft (2) is a 1:50 conical surface, the outer wall is a cylindrical surface that matches the inner hole of the product to be processed, the diameter tolerance is h6, and the surface roughness is Ra0.

8.

5. The precision control fixture for shafts according to claim 4, characterized in that, The outer wall of the expansion cone shaft (4) is a 1:50 conical surface, quenched with 42CrMo, and the conical surface is ground with a surface roughness of Ra0.

4. The outer circle is plated with hard chrome with a layer thickness of 0.02mm.

6. The precision control fixture for shafts according to claim 5, characterized in that, The inner side of the pressure plate (6) is covered with a 3mm thick polyurethane buffer pad with a Shore hardness of 90HA, and the pressure plate has anti-slip texture.

7. The precision control fixture for shafts according to claim 6, characterized in that, The split shaft (2) is made of 7075-T6 aluminum alloy with a tensile strength of 570MPa and a density of 2.8g / cm³. The inner wall of the conical hole is nitrided to a depth of 0.1mm and has a surface hardness of HV900. The outer cylindrical surface is precision machined and ground, with a cylindricity ≤0.005mm.

8. The precision control fixture for shafts according to claim 7, characterized in that, The piezoelectric force sensor has a range of 0-2000N and an accuracy of ±1N.

9. The precision control fixture for shafts according to claim 8, characterized in that, The servo motor has a rated thrust of 1500-3000N and an axial travel of 5-10mm.

10. A machining control method for a precision control fixture for shafts, characterized in that, The precision control method for the shaft precision control fixture includes: The outer edge of the support module (5) is coaxially aligned with the inner edge of the cylindrical product to be processed. The CNC system sends a command, the electric push rod (1) pushes the pull rod (3) so that the expansion cone shaft (4) moves axially and the split shaft (2) expands radially. Finally, the CNC center performs milling / grinding.

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