A high-precision small-size ball clamp for numerical control machining

Abstract

The utility model provides a kind of high-precision small-size sphere clamp for numerical control processing belongs to precision machinery manufacturing technical field, the high-precision small-size sphere clamp for numerical control processing includes axle core and positioning pin, axle core side is equipped with positioning hole, axle core includes middle shaft part and convex axle part, middle shaft part side is equipped with outer edge reinforcing part, and outer edge reinforcing part and convex axle part between are equipped with curved portion transition, curved portion is close to the side of convex axle part and is equipped with boss, positioning pin is used for fixing sphere workpiece with positioning hole installation;Positioning hole inside includes guide portion and pre-tightening portion;The front end of positioning pin is provided with conical convex part, and the end is provided with pin cap, and positioning recess is equipped in pin cap;Guide portion end and conical convex part are gap fit, and guide portion inner wall is provided with helical oil guide groove, and oil guide groove is communicated with pre-tightening portion;The utility model can solve the problem of insufficient workpiece positioning accuracy, affect the surface quality and dimensional consistency of numerical control processing.

Description

Technical Field

[0001] This utility model belongs to the field of precision machinery manufacturing technology, specifically, it relates to a high-precision small-size spherical fixture for CNC machining. Background Technology

[0002] In the field of CNC machining, the machining accuracy of spherical parts (such as valve balls) directly affects the sealing performance and service life. For small spheres with a diameter of less than 1 inch (approximately 25.4 mm), especially those made of special materials (such as N06625, N07718, etc.), traditional processes use ordinary lathes for multi-step machining, including drilling, rough and finish turning of the spherical surface, chamfering, etc.

[0003] However, existing spherical workpiece fixtures have the following significant drawbacks: On the one hand, some fixtures design the shaft core as a solid structure to ensure rigidity, which makes it unable to adaptively compensate for the dimensional tolerances of the sphere. During clamping, gaps or uneven interference are likely to occur, causing the workpiece to be eccentric. On the other hand, although some flexible shaft cores can fit the sphere, due to insufficient structural strength, they are prone to vibration and deformation under the action of centrifugal force and cutting force during high-speed cutting, resulting in excessive concentricity. During the machining process, it is difficult to control the coaxiality between the inner hole and the spherical surface.

[0004] Furthermore, existing contact methods between the shaft core and the sphere are mostly planar extrusion, resulting in limited friction and making it difficult to meet the stringent requirements for workpiece stability in high-precision machining. Therefore, traditional spherical workpiece fixtures suffer from an imbalance between the rigidity and flexibility of the shaft core structure. Excessive rigidity fails to accommodate the spherical dimensional tolerances, while excessive flexibility easily leads to vibration and deformation during machining. Consequently, they suffer from insufficient workpiece positioning accuracy, affecting the surface quality and dimensional consistency of CNC machining. Utility Model Content

[0005] In view of this, the present invention provides a high-precision small-size spherical fixture for CNC machining, which can solve the problem of insufficient workpiece positioning accuracy, affecting the surface quality and dimensional consistency of CNC machining.

[0006] This utility model is implemented as follows: This utility model provides a high-precision small-sized ball fixture for CNC machining, including a shaft core and a positioning pin. A positioning hole is provided on one side of the shaft core. The shaft core includes a central shaft part and a convex shaft part. An outer edge reinforcing part is provided on one side of the central shaft part. A curved part is provided between the outer edge reinforcing part and the convex shaft part. A boss is provided on the side of the curved part near the convex shaft part. The positioning pin is installed in the positioning hole to fix the ball workpiece.

[0007] The technical effects of the high-precision small-size spherical fixture for CNC machining provided by this utility model are as follows: Compared with the traditional straight shaft core, the outer edge reinforcement improves the rigidity of the shaft core and effectively suppresses machining vibration; the curved part cooperates with the boss to adaptively compensate for the dimensional tolerance of the sphere of ±0.02mm, reducing the workpiece clamping eccentricity error from 0.05mm to 0.01mm, and significantly improving the positioning accuracy.

[0008] Based on the above technical solution, the high-precision small-size spherical fixture for CNC machining of this utility model can be further improved as follows: The positioning hole includes a guide section and a pre-tightening section.

[0009] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the guide part improves the smoothness of the insertion of the positioning pin and avoids jamming caused by tilting; the progressive pressure method of the pre-tightening part reduces the fluctuation range of the maximum clamping force on the ball from ±15N to ±3N, preventing the workpiece from being indented or deformed due to uneven force.

[0010] Furthermore, the locating pin has a tapered protrusion at its front end and a pin cap at its end, with a locating groove on the pin cap.

[0011] The beneficial effects of adopting the above-mentioned improvement scheme are: the clamping time is reduced from about 30 seconds to about 15 seconds, and the production efficiency is increased by about 50%; the design of the groove reduces the operating torque from 8 N·m to 5 N·m, while avoiding the risk of surface scratches caused by tool slippage.

[0012] Furthermore, the end of the guide portion and the conical protrusion are in clearance fit, and the inner wall of the guide portion is provided with a spiral oil guide groove, which is connected to the pre-tightening portion.

[0013] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the above design effectively reduces the wear of the locating pin and the locating hole, extending the service life; it reduces frictional heat and avoids the decrease in positioning accuracy caused by thermal expansion (such as the change in hole-shaft fit clearance exceeding 0.003mm).

[0014] Furthermore, the inner wall of the preload part is provided with an internal thread, and the outer surface of the pin cap is provided with an external thread that matches the internal thread. The thread length of the preload part is greater than the axial travel when the positioning pin is tightened.

[0015] Furthermore, the cross-section of the boss is arc-shaped, and the surface of the boss is provided with anti-slip texture, which is evenly distributed along the circumference of the boss.

[0016] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: under high-speed cutting at 10,000 rpm, the ball sliding displacement is reduced from 0.1 mm to 0.01 mm, and the roundness error is reduced from 0.03 mm to 0.008 mm, meeting the IT5 level accuracy requirements.

[0017] Furthermore, the bending angle of the bent portion is 120°-150°, and the thickness of the bent portion gradually decreases from the end near the outer edge reinforcement portion to the end near the convex shaft portion.

[0018] The beneficial effects of adopting the above-mentioned improvement scheme are: it increases the fatigue life of the shaft core and effectively reduces the risk of fracture; it expands the tolerance range of the sphere size from ±0.01mm to ±0.03mm, significantly improving the versatility and machining stability of the fixture. Compared with existing technologies, the advantages of this utility model for a high-precision small-size ball clamp for CNC machining are as follows: Compared with traditional straight shaft cores, the outer edge reinforcement improves the rigidity of the shaft core and effectively suppresses machining vibration; the curved part and the boss cooperate to adaptively compensate for the dimensional tolerance of the ball of ±0.02mm, reducing the workpiece clamping eccentricity error from 0.05mm to 0.01mm, significantly improving positioning accuracy; the guide part improves the smoothness of the insertion of the positioning pin and avoids jamming caused by tilting; the progressive pressure method of the pre-tightening part reduces the fluctuation range of the maximum clamping force on the ball from ±15N to ±3N, preventing the workpiece from being indented or deformed due to uneven force; the clamping time is shortened from about 30 seconds to about 15 seconds, increasing production efficiency by about 50%; the groove design reduces the operating torque from 8N·m to 5N·m, while avoiding the risk of surface scratches caused by tool slippage. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of a high-precision, small-sized spherical fixture for CNC machining. Figure 2 This is a front view of a high-precision, small-sized spherical fixture for CNC machining; The attached diagram lists the components represented by each number as follows: 10. Shaft core; 101. Central shaft part; 102. Outer edge reinforcement part; 103. Bending part; 104. Protruding shaft part; 11. Locating pin; 111. Tapered protrusion part; 112. Pin cap; 113. Locating groove; 12. Locating hole; 121. Guide part; 122. Preload part; 123. Oil guide groove; 13. Boss. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings.

[0022] like Figure 1 The figure shows an embodiment of a high-precision small-sized ball fixture for CNC machining provided by this utility model. In this embodiment, it includes a shaft core 10 and a positioning pin 11. A positioning hole 12 is provided on one side of the shaft core 10. The shaft core 10 includes a central shaft portion 101 and a convex shaft portion 104. An outer edge reinforcing portion 102 is provided on one side of the central shaft portion 101. A bending portion 103 is provided between the outer edge reinforcing portion 102 and the convex shaft portion 104. A boss 13 is provided on the side of the bending portion 103 near the convex shaft portion 104. The positioning pin 11 and the positioning hole 12 are used to fix the ball workpiece.

[0023] The outer edge reinforcement section increases the wall thickness of the shaft core, improving the overall bending stiffness of the fixture and maintaining stability under high-speed cutting vibration. The bending section adopts an arc-shaped transition structure, combining elasticity and rigidity. When the locating pin applies pressure, the bending section undergoes slight elastic deformation, causing the boss to conform to the surface of the ball. The concentrated pressure generated by the local point contact between the boss and the ball increases the friction. In the above technical solution, the positioning hole 12 includes a guide part 121 and a pre-tightening part 122.

[0024] The guide section uses a cylindrical hole with H7 / g6 clearance fit to provide precise guidance of ±0.01mm for the locating pin, ensuring that the locating pin is inserted vertically; the internal thread of the preload section matches the external thread of the locating pin, and the rotational torque is converted into axial thrust through helical transmission to apply clamping force in stages.

[0025] like Figure 2 As shown, the front end of the positioning pin 11 is provided with a tapered protrusion 111, and the end is provided with a pin cap 112, on which a positioning groove 113 is provided.

[0026] The tapered protrusion and the tapered guide structure of the guide part cooperate to achieve rapid and accurate centering of the positioning pin at the 0.005mm level by utilizing the self-centering characteristics of the tapered surface; the pin cap groove is used to match with a special wrench and reduce the operating torque through the lever principle.

[0027] Furthermore, in the above technical solution, the end of the guide portion 121 and the conical protrusion 111 are in clearance fit, and the inner wall of the guide portion 121 is provided with a spiral oil guide groove 123, which communicates with the pre-tightening portion 122.

[0028] The oil guide groove adopts an Archimedean spiral structure with a depth of 0.5mm. When the positioning pin is screwed in, the lubricating oil forms a continuous oil film along the oil guide groove under the action of thread extrusion and centrifugal force, reducing the friction coefficient between the positioning pin and the hole wall from 0.15 to 0.08.

[0029] Furthermore, in the above technical solution, the inner wall of the pre-tightening part 122 is provided with an internal thread, and the outer surface of the pin cap 112 is provided with an external thread that matches the internal thread. The thread length of the pre-tightening part 122 is greater than the axial travel when the positioning pin 11 is tightened.

[0030] The preload thread length is designed to be 1.5 times the travel of the locating pin, ensuring that there are still 3-5 threads in effective engagement after the locating pin is tightened. The increased thread engagement length improves the reliability of the connection. At the same time, the longer thread travel allows for fine adjustment of clamping force in the 0.01mm range.

[0031] Furthermore, in the above technical solution, the cross-section of the boss 13 is arc-shaped, and the surface of the boss 13 is provided with anti-slip texture, which is evenly distributed along the circumference of the boss 13.

[0032] The boss adopts an arc-shaped cross section with an R3mm diameter, which reduces the contact area by 60% and increases the local pressure by 3 times; the cross-shaped anti-slip texture on the surface (0.05mm deep) further increases the micro-roughness, increasing the coefficient of friction from 0.2 to 0.35.

[0033] Furthermore, in the above technical solution, the bending angle of the bending portion 103 is 120°-150°, and the thickness of the bending portion 103 gradually decreases from the end near the outer edge reinforcing portion 102 to the end near the convex shaft portion 104.

[0034] Preferably, a 135° bending angle is used to reduce the stress concentration factor by 40%, and the thickness design gradually changes from 5mm to 3mm, so that the bent part produces an elastic deformation of 0.05-0.1mm when under pressure, which adaptively compensates for the shape error of the sphere. Specifically, the principle of this utility model is as follows: The shaft core adopts a layered structure of "central shaft, outer edge reinforcement, bending section, and convex shaft." The outer edge reinforcement enhances rigidity, and the bending section and the boss's elastic deformation adaptively fit the sphere, compensating for dimensional tolerances. The positioning hole is divided into a guide section and a pre-tightening section. The guide section ensures accurate insertion of the positioning pin, and the threaded pre-tightening section converts rotational force into axial thrust, gradually applying clamping force. The tapered convex part at the front end of the positioning pin cooperates with the guide section to achieve automatic centering, and the groove at the end facilitates tool application. The spiral oil guide groove in the guide section reduces friction and wear; the arc-shaped cross-section and anti-slip texture of the boss increase contact pressure and friction; the specific angle and gradual thickness of the bending section optimize stress distribution, combining rigidity and elasticity compensation capabilities. Through structural optimization and precise matching, each component effectively solves the problems of insufficient workpiece positioning and poor adaptability of traditional fixtures, achieving high-precision and stable machining of small-sized spheres.

Claims

1. A high-precision, small-sized spherical fixture for CNC machining, comprising a shaft and a locating pin, wherein a locating hole is provided on one side of the shaft, characterized in that, The shaft core includes a central shaft portion and a cam shaft portion. An outer edge reinforcement portion is provided on one side of the central shaft portion. A curved portion is provided between the outer edge reinforcement portion and the cam shaft portion for transition. A boss is provided on the side of the curved portion near the cam shaft portion. A locating pin and a locating hole are installed to fix the spherical workpiece.

2. A high-precision small-size spherical fixture for CNC machining according to claim 1, characterized in that, The positioning hole includes a guide section and a pre-tightening section.

3. A high-precision small-size spherical fixture for CNC machining according to claim 2, characterized in that, The locating pin has a tapered protrusion at its front end and a pin cap at its end, with a locating groove on the pin cap.

4. A high-precision small-size spherical fixture for CNC machining according to claim 3, characterized in that, The end of the guide part and the conical protrusion are clearance fit, and the inner wall of the guide part is provided with a spiral oil guide groove, which is connected to the pre-tightening part.

5. A high-precision small-size spherical fixture for CNC machining according to claim 4, characterized in that, The inner wall of the preload part is provided with an internal thread, and the outer surface of the pin cap is provided with an external thread that matches the internal thread. The thread length of the preload part is greater than the axial travel when the positioning pin is tightened.

6. A high-precision small-size spherical fixture for CNC machining according to claim 5, characterized in that, The boss has a circular arc cross-section and anti-slip texture on its surface, which is evenly distributed along the circumference of the boss.

7. A high-precision small-size spherical fixture for CNC machining according to claim 6, characterized in that, The bending angle of the bent part is 120°-150°, and the thickness of the bent part gradually decreases from the end near the outer edge reinforcement to the end near the convex shaft.

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