A coreless mandrel tube bending die and a method of processing the same
By using the asymmetric cavity design and dynamic extrusion of the coreless bending die, the problem of wrinkling during copper tube bending is solved, achieving high yield and efficient automated production, and reducing production costs and time.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG HANGJI METAL PRODUCT INDUSTRIES CO LTD
- Filing Date
- 2026-04-24
- Publication Date
- 2026-06-09
AI Technical Summary
Traditional copper tube bending processes suffer from low production efficiency, high costs, and stringent operational skill requirements. In particular, the application of mandrels is limited in the processing of small-radius bends or complex pipe fittings. Furthermore, the empty bending process without mandrels results in severe wrinkling of copper tubes and a low yield rate, which cannot meet the needs of large-scale production.
By using a coreless pipe bending die, and designing U-shaped guide grooves, slots, and extrusion grooves on the bending die, combined with the dynamic extrusion of the clamping block and guide die, asymmetric cavity design and dynamic extrusion are achieved, which suppresses pipe wrinkling and forms longitudinal reinforcing ribs.
It improves the product yield rate to over 97%, simplifies the process flow, is suitable for automated production, reduces production costs by 20%-40%, and increases production efficiency by 30%.
Smart Images
Figure CN122164816A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of pipe bending molds, and more particularly to a mandrel-less pipe bending mold and its processing method. Background Technology
[0002] In traditional copper tube bending, auxiliary structures such as bending mandrels and anti-wrinkle dies are typically used to prevent wrinkling of the tubes. However, this method suffers from low production efficiency, high processing costs, and stringent skill requirements for operators; the application of mandrels is particularly limited in scenarios involving small-radius bending or complex tube processing. Existing mandrel-less air bending processes generally suffer from severe copper tube wrinkling, resulting in extremely low product yields and failing to meet the demands of large-scale, mass production. Summary of the Invention
[0003] In view of the above problems, the present invention is proposed to provide solutions that overcome or at least partially solve the above problems.
[0004] According to one aspect of the present invention, a mandrel-less pipe bending die is provided, comprising a bending die, wherein a U-shaped guide groove is provided on the side of the bending die, a retaining groove is provided at the bottom of the two vertical ends of the guide groove, and an extrusion groove is provided at the bottom of the bending section of the guide groove, wherein the retaining groove and the extrusion groove are both of a semi-circular structure, the diameter of the retaining groove is equal to the diameter of the mandrel-less pipe, and the diameter of the extrusion groove is the diameter of the mandrel-less pipe reduced by 0.6 to 1 mm.
[0005] Preferably, a clamping block is provided on a vertical section of the guide groove, and an additional clamping groove is provided on the end of the clamping block near the bending die. The additional clamping groove and the clamping groove are combined to form a circular limiting groove for fixing the coreless rod end.
[0006] Preferably, the guide groove is slidably fitted with a guide mold on the curved section, and the guide mold has an extrusion groove on the side near the curved mold. When the guide mold slides, the extrusion groove and the extrusion groove cooperate, and the diameter of the extrusion groove is adapted to the diameter of the extrusion groove. The two work together to form a movable extrusion cavity.
[0007] Preferably, the bending die is fixedly installed on the rotating worktable of the pipe bending machine, the clamping block is fixed to the fixed bracket of the pipe bending machine by a hydraulic cylinder, and the guide die is connected to the moving arm of the pipe bending machine by a servo drive.
[0008] Preferably, the sliding speed of the guide die is matched with the rotation speed of the bending die, and the two work together to achieve continuous dynamic constraint of the tube by the moving extrusion chamber.
[0009] On the other hand, a method for processing a coreless pipe bending die includes the following steps: Step 1. Mold preparation: Process bending dies, clamping blocks, and guide dies according to the design dimensions to ensure the dimensional accuracy and surface finish of the slots, extrusion grooves, and mating cavities; Step 2. Mold installation: Fix the bending die to the rotating worktable of the pipe bending machine, fix the clamping block to the fixed bracket, and connect the guide die to the moving arm; Step 3. Clamping and positioning: Place the pipe in the guide groove of the bending die and clamp the straight pipe section with the additional slot of the clamping block; Step 4. Linked pipe bending: Start the pipe bending machine. The bending die and clamping block are rotated by the servo motor rotating the worktable. The guide die slides along the bending section of the guide groove and cooperates with the extrusion groove of the bending die to apply dynamic extrusion force to the outer side of the pipe bend. Step 5. Forming constraint: The extrusion pressure counteracts the tangential compressive stress of the pipe, guiding the pipe material to gather on both sides to form longitudinal reinforcing ribs, thus completing the forming of a wrinkle-free pipe; Step 6. Demolding and part removal: After the pipe is in place, release the clamping block, exit the guide mold, take out the finished pipe fitting, and the equipment resets and restarts.
[0010] The mandrel-less bending die provided by this invention, through the asymmetrical cavity design of the die and the cooperation of the dynamic extrusion cavity, transforms the process from "suppressing instability" to "guiding molding," fundamentally solving the problem of wrinkling when bending copper tubes without a mandrel, improving product yield, eliminating the need for a mandrel and anti-wrinkle mold, simplifying the process flow, and enabling quick die replacement through modular design, is suitable for automated production, improving production efficiency, and saving the manufacturing and maintenance costs of mandrels and anti-wrinkle molds, reducing scrap loss, and lowering production costs. In addition, by adjusting the reduction amount of the extrusion groove, it can be adapted to copper tubes of different diameters and wall thicknesses and other easily wrinkled metal tubes, making it highly versatile.
[0011] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description
[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0013] Figure 1 This is a schematic diagram of the overall structure of the pipe bending mold provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the bending die structure provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the clamping block structure provided in an embodiment of the present invention; Figure 4This is a schematic diagram of the guide mold structure provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the pipe bending mold installation structure provided in an embodiment of the present invention; Figure 6 A cross-sectional view of the working state provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the axial flow of metal pipe material during the pipe bending process provided in an embodiment of the present invention. Figure 8 This is a partially enlarged schematic diagram provided for an embodiment of the present invention; Figure 9 This is a schematic diagram of the processed product provided in an embodiment of the present invention; In the figure: 1. Bending die; 11. Guide groove; 12. Slot; 13. Extrusion groove; 2. Clamping block; 21. Additional slot; 3. Guide die; 31. Extrusion slot. Detailed Implementation
[0014] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
[0015] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.
[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.
[0017] A type of mandrel-less pipe bending die, such as Figure 1-4 As shown, the device includes a bending die 1, a U-shaped guide groove 11 on the side of the bending die 1, a retaining groove 12 at the bottom of the two vertical ends of the guide groove 11, and an extrusion groove 13 at the bottom of the bent section of the guide groove 11. Both the retaining groove 12 and the extrusion groove 13 adopt a semi-circular structure. The diameter of the retaining groove 12 is equal to the diameter of the coreless rod, and the diameter of the extrusion groove 13 is the diameter of the coreless rod reduced by 0.6 to 1 mm.
[0018] In one possible implementation, a clamping block 2 is clamped in a vertical section of the guide groove 11, and an additional clamping groove 21 is correspondingly opened at the end of the clamping block 2 near the bending die 1. The additional clamping groove 21 and the clamping groove 12 are combined to form a circular limiting groove for fixing the end without a core rod.
[0019] In one possible implementation, the guide mold 3 is slidably engaged in the curved section of the guide groove 11. The guide mold 3 has an extrusion groove 31 on the side near the curved mold 1. When the guide mold 3 slides, the extrusion groove 13 and the extrusion groove 31 cooperate. The diameter of the extrusion groove 31 is adapted to the diameter of the extrusion groove 13, and the two work together to form a movable extrusion cavity.
[0020] Furthermore, the card slot 12 and the auxiliary card slot 21 are tightly fitted during machining, and the extrusion groove 13 and the extrusion card slot 31 are tightly fitted during machining.
[0021] In one possible implementation, such as Figure 5 As shown, the bending die 1 is fixedly installed on the rotating worktable of the pipe bending machine, the clamping block 2 is fixed on the fixed bracket of the pipe bending machine by hydraulic cylinder, and the guide die 3 is connected to the moving arm of the pipe bending machine by servo drive.
[0022] In one possible implementation, the sliding speed of the guide die 3 is matched with the rotation speed of the bending die 1, and the two work together to achieve continuous dynamic constraint of the tube by the moving extrusion chamber.
[0023] In one possible implementation, the diameter reduction of the extrusion groove 13 is adjusted according to the diameter and wall thickness of the pipe to be processed, applicable to all specifications of copper pipes and other easily wrinkled metal pipes.
[0024] In one possible implementation, such as Figure 8 As shown, when the pipe to be processed is a Φ12.7mm pipe, the diameter of the bending die extrusion groove 13 and the guide die extrusion groove 31 is set to Φ12mm, and the reduction amount is 0.7mm.
[0025] In one possible implementation, the pipe bending mold is integrated into an automated production line, and the timing of the actions of the bending mold 1 rotating, the clamping block 2 holding, and the guide mold 3 sliding is coordinated by a PLC control system to achieve mass production.
[0026] Furthermore, a method for processing a mandrel-less pipe bending die includes the following steps: Step 1. Mold preparation: Process bending die 1, clamping block 2, and guide die 3 according to the design dimensions, and ensure the dimensional accuracy and surface finish of the slot 12, extrusion groove 13, and mating cavity; Step 2. Mold installation: Fix the bending mold (1) to the rotating worktable of the pipe bending machine, fix the clamping block 2 to the fixed bracket, and connect the guide mold (3) to the moving arm; Step 3. Clamping and positioning: Place the pipe in the guide groove 11 of the bending die 1, and clamp the straight pipe section with the additional slot 21 of the clamping block 2; Step 4. Linked pipe bending: Start the pipe bending machine. The bending die 1 and the clamping block 2 are rotated by the servo motor rotating worktable. The guide die 3 slides along the bending section of the guide groove 11 and cooperates with the extrusion groove 13 of the bending die 1 to apply dynamic extrusion force to the outer side of the pipe bending. Step 5. Forming constraint: The extrusion pressure counteracts the tangential compressive stress of the pipe, guiding the pipe material to gather on both sides to form longitudinal reinforcing ribs, thus completing the forming of a wrinkle-free pipe; Step 6. Demolding and part removal: After the pipe is bent into place, release the clamping block 2, exit the guide mold 3, take out the finished pipe fitting, and the equipment resets and restarts.
[0027] By adopting the above technical solution: 1. Fundamentally solves the wrinkling problem: The diameter of the bend transition section is intentionally designed to be smaller than the outer diameter of the pipe. This design breaks with conventional thinking. This asymmetrical cavity forces the pipe to be radially constrained when entering the bending area. Through the asymmetrical cavity design of the mold and the combination of dynamic extrusion cavity, the process changes from "suppressing instability" to "guiding molding", fundamentally solving the problem of wrinkling when bending copper pipes without a core rod. According to production data statistics, the yield rate has increased to over 97%.
[0028] 2. Simplified process and improved efficiency: Completely eliminates the core rod and anti-wrinkle mold, simplifies the process flow, and enables quick mold replacement through modular design, making it suitable for automated production. According to production data statistics, production efficiency has been improved by more than 30%.
[0029] 3. Cost reduction: Saves on the manufacturing and maintenance costs of core rods and anti-wrinkle molds, reduces scrap losses, and according to production data statistics, the overall production cost is reduced by 20%-40%.
[0030] 4. Wide range of applications: By adjusting the reduction amount of the extrusion groove, it can be adapted to copper pipes of different diameters and wall thicknesses and other easily wrinkled metal pipes, making it highly versatile.
[0031] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A mandrel-less pipe bending mold, characterized in that: The device includes a bending die (1), which has a U-shaped guide groove (11) on its side. The bottom of the guide groove (11) at its two vertical ends has a slot (12), and the bottom of the bending section of the guide groove (11) has an extrusion groove (13). Both the slot (12) and the extrusion groove (13) have a semi-circular structure. The diameter of the slot (12) is equal to the diameter of the coreless rod, and the diameter of the extrusion groove (13) is the diameter of the coreless rod reduced by 0.6 to 1 mm.
2. The mandrel-less pipe bending mold as described in claim 1, characterized in that: A clamping block (2) is installed in a vertical section of the guide groove (11). An additional clamping groove (21) is provided at one end of the clamping block (2) near the bending die (1). The additional clamping groove (21) and the clamping groove (12) are combined to form a circular limiting groove for fixing the end without a core rod.
3. The mandrel-less pipe bending mold as described in claim 1, characterized in that: The guide groove (11) is slidably fitted with a guide mold (3). The guide mold (3) is provided with an extrusion groove (31) on the side near the bending mold (1). When the guide mold (3) slides, the extrusion groove (13) and the extrusion groove (31) cooperate. The diameter of the extrusion groove (31) is adapted to the diameter of the extrusion groove (13), and the two work together to form a moving extrusion cavity.
4. The mandrel-less pipe bending mold as described in claim 1, characterized in that: The bending die (1) is fixedly installed on the rotating worktable of the pipe bending machine, the clamping block (2) is fixed on the fixed bracket of the pipe bending machine by a hydraulic cylinder, and the guide die (3) is connected to the moving arm of the pipe bending machine by a servo drive.
5. The mandrel-less pipe bending mold as described in claim 1, characterized in that: The sliding speed of the guide die (3) is matched with the rotation speed of the bending die (1), and the two work together to achieve continuous dynamic constraint of the moving extrusion chamber on the pipe.
6. A method for processing a mandrel-less pipe bending die, characterized in that, Includes the following steps: Step 1. Mold preparation: Process the bending die (1), clamping block (2), and guide die (3) according to the design dimensions, and ensure the dimensional accuracy and surface finish of the slot (12), extrusion groove (13) and mating cavity; Step 2. Mold installation: Fix the bending mold (1) to the rotating worktable of the pipe bending machine, fix the clamping block (2) to the fixed bracket, and connect the guide mold (3) to the moving arm; Step 3. Clamping and positioning: Place the pipe in the guide groove (11) of the bending die (1) and clamp the straight pipe section with the additional slot (21) of the clamping block (2); Step 4. Linkage pipe bending: Start the pipe bending machine. The bending die (1) and the clamping block (2) are rotated and processed by the servo motor rotating worktable. The guide die (3) slides along the bending section of the guide groove (11) and cooperates with the extrusion groove (13) of the bending die (1) to apply dynamic extrusion force to the outer side of the pipe bending. Step 5. Forming constraint: The extrusion pressure counteracts the tangential compressive stress of the pipe, guiding the pipe material to gather on both sides to form longitudinal reinforcing ribs, thus completing the forming of a wrinkle-free pipe; Step 6. Demolding and removing parts: After the pipe is in place, release the clamp (2), exit the guide mold (3), remove the finished pipe fitting, and the equipment resets and restarts.