A process and apparatus for internally threaded extrusion

Abstract

The application provides an inner thread extrusion forming process and device, which solves the problem of inner thread turning and the like, and comprises a clamp for clamping a workpiece, the clamp is provided with a tool bar opposite to the workpiece, the clamp and / or the tool bar is drivingly connected with a driving structure, and a planetary inner thread extrusion assembly is installed in the tool bar. The application has the advantages of high processing efficiency, low cost and the like.

Description

Technical Field

[0001] This invention belongs to the field of turning technology, specifically relating to an internal thread extrusion forming process and apparatus. Background Technology

[0002] Currently, large-diameter internal threads are mainly machined using turning or grinding. Turning suffers from low efficiency, high tool wear, and is prone to generating chatter marks, as well as cutting off the fibrous structure on the thread surface, resulting in poor thread strength and fatigue life. Grinding, while ensuring accuracy, is even less efficient and more expensive. When the internal thread diameter is large, the forming torque and wear of the forming tap increase dramatically. For large-diameter workpieces, traditional tapping is almost impossible. None of the above methods can simultaneously meet the manufacturing requirements of high efficiency, high quality, and low cost for large-diameter internal threads.

[0003] To address the shortcomings of existing technologies, people have conducted long-term explorations and proposed various solutions. For example, Chinese patent literature discloses a two-way turning tool spindle clamp [201220413692.9], which includes a spindle box, a main drive synchronous pulley at the rear end of the spindle box, and a cylinder at the front end of the spindle box; the main drive synchronous pulley and the rotating shaft rotate radially synchronously; the rotating shaft, the pusher, and the cylinder rotate radially synchronously synchronously; the cylinder and the double-cylinder connecting rod rotate radially synchronously synchronously; the double-cylinder connecting rod and the collet rotate radially synchronously synchronously; the collet is used to clamp the workpiece; the cylinder drives the right cylinder and the pusher to move left and right to achieve clamping or releasing the workpiece.

[0004] The above solution has solved the problem of workpiece clamping during turning to a certain extent, but it still has many shortcomings, such as low efficiency in machining large-diameter internal threads. Summary of the Invention

[0005] The purpose of this invention is to address the above-mentioned problems by providing a reasonably designed and highly efficient internal thread extrusion molding device.

[0006] The purpose of this invention is to address the above-mentioned problems by providing a high-quality internal thread extrusion molding process.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: an internal thread extrusion forming device, comprising a fixture for clamping a workpiece, the fixture being equipped with a tool bar opposite to the workpiece, the fixture and / or the tool bar being driven by a drive structure, and a planetary internal thread extrusion assembly being installed inside the tool bar.

[0008] In the aforementioned internal thread extrusion forming device, the planetary internal thread extrusion assembly includes a sun gear rotatably mounted inside a cutter bar and several planet gears meshing and driving with the sun gear. The central axis of the planet gears is parallel to the central axis of the sun gear and the cutter bar, and each planet gear has an extrusion blade extending axially.

[0009] In the aforementioned internal thread extrusion forming device, the extrusion blade is spiral-shaped, with a tapered cutting edge at the front end and a forming correction section at the rear end.

[0010] In the aforementioned internal thread extrusion molding apparatus, the sun gear and planetary gears are rotatably mounted in the extrusion chamber at the front end of the cutter bar. A front cover plate that seals the extrusion chamber is fixed at the front end of the cutter bar, and an opening is provided circumferentially at the front end of the cutter bar for the extrusion blade to extend outward.

[0011] In the aforementioned internal thread extrusion molding device, the fixture includes a double-cylinder spindle, inside which a movable cylinder is movably mounted via bearings, and clamping heads for extruding and fixing workpieces are respectively installed at both ends of the movable cylinder.

[0012] In the aforementioned internal thread extrusion molding apparatus, the drive structure includes a rotary drive group and a moving drive group; the rotary drive group drives the movable cylinder and / or the sun gear to rotate; the moving drive group drives the clamp and / or the tool holder to slide.

[0013] An internal thread extrusion molding process, employing the aforementioned internal thread extrusion molding apparatus, includes the following steps:

[0014] S1: The fixture holds the workpiece;

[0015] S2: The drive structure drives the fixture and / or tool holder to feed along the axis of the workpiece's inner hole;

[0016] S3: Planetary internal thread extrusion assembly performs internal thread extrusion forming on the inner hole of the workpiece.

[0017] S4: Forming complete, planetary internal thread extrusion assembly withdraws from workpiece inner hole, fixture and / or tool holder reset.

[0018] In one of the above-mentioned internal thread extrusion molding processes, in step S2, the fixture is fed toward the tool holder while the tool holder remains fixed; or, the tool holder is fed toward the fixture while the fixture remains fixed; or, the fixture and the tool holder are fed relative to each other.

[0019] In the above-mentioned internal thread extrusion molding process, step S3 includes the following steps:

[0020] S31: The drive structure rotates the workpiece and / or the tool holder;

[0021] S32: The extrusion cutter rotates under the action of friction and is synchronously driven by the sun gear and planet gear. Its cutting edge section first performs radial rolling on the inner hole of the workpiece to form the initial tooth profile and produce cold work hardening.

[0022] S33: The forming correction section finishes the thread.

[0023] In one of the above-mentioned internal thread extrusion molding processes, in step S31, the workpiece is circumferentially fixed and the tool holder rotates circumferentially; or, the workpiece rotates circumferentially and the tool holder is circumferentially fixed; or, the workpiece and the tool holder rotate in opposite directions.

[0024] Compared with existing technologies, the advantages of this invention are as follows: planetary multi-tooth synchronous rolling can complete the full thread processing in a single feed, resulting in high thread processing efficiency; extrusion molding makes the metal fibers continuous, generating compressive stress and work hardening on the surface, which greatly improves the thread strength, hardness and fatigue life; chipless processing saves materials, extends tool life and significantly reduces overall costs; the tapered design of the entry section provides good guidance and the correction section ensures accuracy, making it especially suitable for large-diameter deep hole thread processing. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention;

[0026] Figure 2 This is a structural cross-sectional view of the present invention;

[0027] Figure 3 This is a schematic diagram of the tool holder structure of the present invention;

[0028] Figure 4 This is a schematic diagram of the planetary internal thread extrusion assembly of the present invention;

[0029] Figure 5 This is a structural schematic diagram of the tool holder of the present invention from another perspective;

[0030] In the figure, the fixture is 1, the double-cylinder spindle is 11, the movable cylinder is 12, the clamping head is 13, the tool holder is 2, the workpiece is 3, the drive structure is 4, the planetary internal thread extrusion assembly is 5, the sun gear is 51, the planet gear is 52, the extrusion knife is 53, the cutting edge section is 54, the forming correction section is 55, the extrusion chamber is 56, the front cover plate is 57, and the opening is 58. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1-5 As shown, an internal thread extrusion forming apparatus includes a fixture 1 for clamping a workpiece 3, typically a lathe headstock, which clamps the workpiece 3 and provides rotational driving force. The fixture 1 is equipped with a tool holder 2 opposite to the workpiece 3, the central axis of which coincides with the central axis of the workpiece. When the tool holder 2 feeds along its axis, it turns the inner hole of the workpiece 3. The fixture 1 and / or the tool holder 2 are driven by a drive structure 4 that provides rotational and directional driving force. A planetary internal thread extrusion assembly 5 is installed inside the tool holder 2, which uses extrusion forming to process the thread, ensuring forming quality while being suitable for large-diameter deep hole threads.

[0033] Specifically, unlike conventional turning or tapping methods, the planetary internal thread extrusion assembly 5 includes a sun gear 51 rotatably mounted inside the tool holder 2 and several planet gears 52 meshing with the sun gear 51. The planet gears 52 are fixed in circumferential position relative to the sun gear 51, and their meshing transmission ensures that each planet gear 52 rotates synchronously. The central axis of the planet gear 52 is parallel to the central axis of the sun gear 51 and the tool holder 2. Each planet gear 52 has an axially extending extrusion cutter 53, which contacts the workpiece 3 and its cutting edge cuts into the workpiece radially for rolling.

[0034] Specifically, the extrusion cutter 53 is helical, with a tapered cutting edge section 54 at its tip. During feeding, the cutting edge section 54 first radially rolls the inner hole of the workpiece, forming the initial tooth profile and producing work hardening. The rear end of the extrusion cutter 53 is a forming correction section 55, which finishes the thread, ultimately obtaining a dimensionally accurate and surface-strengthened internal thread. After completion, the relative reversal causes the extrusion cutter 53 to exit the inner hole of the workpiece 3. The extrusion cutter 53 is typically surface-treated, such as nitriding or coating, to enhance hardness and lubricity.

[0035] In addition, the sun gear 51 and planet gears 52 are rotatably mounted in the extrusion chamber 56 at the front end of the tool holder 2. Bearings or bushings are typically installed inside to support the sun gear 51 and planet gears 52, ensuring smooth rotation. A front cover plate 57 is fixed to the front end of the tool holder 2, enclosing the extrusion chamber 56. The front cover plate 57 is secured by bolts or clips for easy disassembly and maintenance. An opening 58 is provided circumferentially at the front end of the tool holder 2 for the extrusion blade 53 to extend outwards. The size and position of the opening 58 are precisely calculated to allow the extrusion blade 53 to extend radially and contact the workpiece 3 during rotation, but to limit excessive displacement and ensure consistent extrusion depth.

[0036] Furthermore, the fixture 1 adopts a conventional spindle structure, specifically including a hollow double-cylinder spindle 11. Inside the double-cylinder spindle 11, a movable cylinder 12 is movably mounted via bearings. Clamping heads 13 for pressing and fixing workpieces 3 are respectively installed at both ends of the movable cylinder 12. A hydraulic structure is provided between the movable cylinder 12 and the double-cylinder spindle 11 to provide clamping force to the clamping heads 13. The clamping heads 13 are usually equipped with replaceable jaws or bushings to accommodate workpieces 3 of different diameters and have a self-centering function to ensure the alignment of workpiece 3 and tool holder 2 and reduce machining errors.

[0037] Furthermore, the drive structure 4 includes a rotary drive group and a moving drive group; the rotary drive group drives the movable cylinder 12 and / or the sun gear 51 to rotate, and uses a gearbox, coupling and other structures to achieve drive transmission; the moving drive group drives the clamp 1 and / or the tool holder 2 to slide, and includes, but is not limited to, screw drive, hydraulic drive and other drive methods to guide it to move along a fixed track.

[0038] Example 1

[0039] This embodiment performs internal thread machining on the inner hole of a cylindrical workpiece 3, and the specific steps are as follows:

[0040] S1: Fixture 1 clamps workpiece 3 to ensure that its position is stable during processing and that it does not move or vibrate.

[0041] S2: Drive structure 4 drives tool holder 2 to feed along the axis of the inner hole of workpiece 3;

[0042] S3: Planetary internal thread extrusion assembly 5 performs internal thread extrusion forming on the inner hole of workpiece 3.

[0043] S31: Drive structure 4 drives workpiece 3 to rotate;

[0044] S32: The extrusion cutter 53 rotates under the action of friction and is synchronously driven by the sun gear 51 and planet gear 52. This is a passive rotation, which helps to reduce friction and wear and makes the extrusion process smoother. Its cutting edge section 54 first performs radial rolling on the inner hole of the workpiece 3. Instead of removing the material, it uses huge pressure to cause the surface metal of the workpiece to produce plastic flow, form the initial tooth shape and produce cold work hardening, so that the machined thread has higher strength and fatigue life than the cutting thread.

[0045] S33: The forming correction section finishes the thread. The shape of this part is consistent with the complete thread profile. It is used to calibrate and burnish the formed thread, eliminate dimensional errors and improve surface finish.

[0046] S4: Forming complete, planetary internal thread extrusion assembly 5 exits from the inner hole of workpiece 3, and tool holder 2 resets.

[0047] Example 2

[0048] The structure, principle, and specific steps of this embodiment are similar to those of Embodiment 1. The difference lies in that when the workpiece is large or irregularly shaped, making it inconvenient to move the tool holder 2, a solution of moving the workpiece 3 can be adopted. In this embodiment, the fixture 1 feeds towards the tool holder 2, the tool holder 2 remains fixed, and the drive structure 4 provides rotational driving force for the workpiece 3, thereby completing the internal thread extrusion forming. The processing essence of this embodiment is similar to that of Embodiment 1, both achieving forming through rotation of 3 and axial relative feeding.

[0049] Example 3

[0050] The structure, principle, and specific steps of this embodiment are similar to those of Embodiment 1. The difference is that this embodiment adopts a compound feeding method, in which the fixture 1 and the tool holder 2 feed relative to each other or move back and forth, and the planetary internal thread extrusion assembly 5 extrudes the internal thread of the workpiece 3 into shape. This feeding method further improves the processing efficiency.

[0051] Example 4

[0052] The structure, principle and specific steps of this embodiment are similar to those of Embodiment 1. The difference is that in this embodiment, the main rotational motion is transferred from the workpiece 3 to the tool holder 2. The driving structure 4 drives the tool holder 2 to rotate circumferentially, while the workpiece 3 is fixed circumferentially. This motion method is very advantageous for situations where the workpiece 3 is not easy to rotate, such as when the workpiece 3 is asymmetrical, too bulky, or difficult to rotate after being connected to the fixture 1.

[0053] Example 5

[0054] The structure, principle, and specific steps of this embodiment are similar to those of Embodiment 1. The difference is that, in order to obtain the highest processing efficiency, the drive structure 4 drives the tool holder 2 and the workpiece 3 to rotate synchronously in this embodiment. However, the workpiece 3 and the tool holder 2 rotate in opposite directions, which greatly increases the relative speed between them. However, the processing method also requires higher synchronous control accuracy.

[0055] Example 6

[0056] The structure, principle and specific steps of this embodiment are similar to those of Embodiment 1. The difference is that in this embodiment, the tool holder 2 and the workpiece 3 rotate in opposite directions either simultaneously or in parallel, and their axial directions are fed relative to each other. The sun gear 51 in the tool holder 2 is driven to rotate by the drive structure 4, thereby driving the planetary gear 52 and the extrusion knife 53 to rotate.

[0057] In summary, the principle of this embodiment is as follows: through a planetary internal thread extrusion assembly 5 installed inside the tool holder 2, the main rotational motion between the workpiece 3 and the tool holder 2 is converted into the synchronous revolution and friction-driven rotation of multiple extrusion blades 53 evenly distributed around the axis. As these extrusion blades 53 feed along the inner hole axis of the workpiece 3, their front cutting edge segments 54 perform continuous and uniform radial cold extrusion on the hole wall metal, forcing the metal to produce plastic flow rather than cutting to form the initial thread profile and induce work hardening. Then, the rear forming correction section 55 finishes and calibrates the formed thread. Finally, in one continuous feed motion, an internal thread with high strength, high precision and high surface quality is efficiently processed.

[0058] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0059] Although this document frequently uses terms such as clamp 1, double-cylinder spindle 11, movable cylinder 12, clamping head 13, tool holder 2, workpiece 3, drive structure 4, planetary internal thread extrusion assembly 5, sun gear 51, planetary gear 52, extrusion blade 53, cutting edge section 54, forming correction section 55, extrusion chamber 56, front cover plate 57, and opening 58, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A process for extruding internal threads, characterized in that, Includes the following steps: S1: The fixture (1) clamps the workpiece (3); S2: The drive structure (4) drives the fixture (1) and / or the tool holder (2) to feed along the axis of the inner hole of the workpiece (3); S3: Planetary internal thread extrusion assembly (5) performs internal thread extrusion forming on the inner hole of workpiece (3); S31: The drive structure (4) drives the workpiece (3) and / or the tool holder (2) to rotate; S32: The extrusion knife (53) rotates under the action of friction and is synchronously driven with the sun gear (51) and planet gear (52). Its cutting edge segment (54) first performs radial rolling on the inner hole of the workpiece (3) to form the initial tooth profile and produce cold work hardening. S33: The forming correction section finishes the thread; S4: Forming is complete, the planetary internal thread extrusion assembly (5) exits from the inner hole of the workpiece (3), and the fixture (1) and / or the tool holder (2) are reset.

2. The internal thread extrusion forming process according to claim 1, characterized in that, In step S2, the fixture (1) feeds toward the tool bar (2) while the tool bar (2) remains fixed; or, the tool bar (2) feeds toward the fixture (1) while the fixture (1) remains fixed; or, the fixture (1) and the tool bar (2) feed relative to each other.

3. The internal thread extrusion molding process according to claim 1, characterized in that, In step S31, the workpiece (3) is fixed circumferentially and the tool holder (2) rotates circumferentially; or, the workpiece (3) rotates circumferentially and the tool holder (2) is fixed circumferentially; or, the workpiece (3) and the tool holder (2) rotate in opposite directions.

4. An internal thread extrusion forming apparatus for implementing an internal thread extrusion forming process as described in any one of claims 1-3, comprising a clamp (1) for holding a workpiece (3), said clamp (1) being equipped with a tool holder (2) opposite to the workpiece (3), characterized in that, The clamp (1) and / or the tool holder (2) are connected to a drive structure (4), and a planetary internal thread extrusion assembly (5) is installed inside the tool holder (2).

5. The internal thread extrusion forming apparatus according to claim 4, characterized in that, The planetary internal thread extrusion assembly (5) includes a sun gear (51) rotatably mounted in the cutter bar (2) and a plurality of planet gears (52) meshing with the sun gear (51). The central axis of the planet gears (52) is parallel to the central axis of the sun gear (51) and the cutter bar (2). Each planet gear (52) has an extrusion blade (53) extending axially.

6. The internal thread extrusion forming apparatus according to claim 5, characterized in that, The extrusion blade (53) is spiral-shaped, with a tapered cutting edge section (54) at the front end and a forming correction section (55) at the rear end.

7. The internal thread extrusion forming apparatus according to claim 5, characterized in that, The sun gear (51) and planet gear (52) are rotatably mounted in the extrusion chamber (56) at the front end of the cutter bar (2). The front end of the cutter bar (2) is fixed with a front cover plate (57) that closes the extrusion chamber (56). The front end of the cutter bar (2) is provided with an opening (58) along the circumferential direction for the extrusion blade (53) to extend outward.

8. The internal thread extrusion forming apparatus according to claim 5, characterized in that, The fixture (1) includes a double-cylinder spindle (11), and a movable cylinder (12) is movably installed inside the double-cylinder spindle (11) via bearings. Clamping heads (13) for pressing and fixing workpieces (3) are respectively installed at both ends of the movable cylinder (12).

9. The internal thread extrusion forming apparatus according to claim 8, characterized in that, The drive structure (4) includes a rotation drive group and a movement drive group; the rotation drive group drives the movable cylinder (12) and / or the sun gear (51) to rotate; the movement drive group drives the clamp (1) and / or the tool holder (2) to slide.

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