High-precision trapezoidal copper wire multi-pass progressive drawing equipment

Abstract

The invention discloses high-precision trapezoidal copper wire multi-pass progressive drawing equipment, and belongs to the technical field of drawing equipment. According to the scheme, a traditional single closed cavity is replaced by a plurality of discrete heat conduction limiting rings which are arranged at intervals in the axial direction, and open clearance spaces are formed between adjacent rings; after the copper wire slightly deforms each time, the lubricating film can be infiltrated by means of the cooling lubricating liquid to realize dynamic self-repairing; meanwhile, cooling and lubricating are integrated in the same closed loop, injection ports are formed in the short axis direction, directional collaborative supply of a high-pressure contact area is achieved through driving of the inter-ring gap pressure difference, and local temperature rise is effectively controlled; according to the section characteristics of different forming stages, an inflatable sealing air bag is adopted for the front section pass to be attached to a smooth oval section, profiling elastic sealing pieces are adopted for the middle section and the tail section to be matched with trapezoidal sections with edges and corners, and the two sealing modes both have the anti-rotation function. The copper wire surface quality, the section precision and the service life of the die are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of drawing equipment technology, and in particular to a high-precision trapezoidal copper wire multi-pass progressive drawing equipment. Background Technology

[0002] In the production of irregularly shaped cross-section copper wire for motor windings, the process of gradually deforming round cross-section copper wire into trapezoidal cross-section through multiple drawing or rolling passes is well-known in the art. In existing technologies, the basic idea of ​​multi-pass progressive forming has been widely applied in the production of flat-wire motor winding copper wire. For example, using a Turkshead mill with multiple stands in series for sequential rolling, or using multiple drawing dies in series to gradually reduce and change the cross-sectional shape. In classic die design systems, the sequence of passes from circle to ellipse to square, or from circle to ellipse to circle, is also well-known to those skilled in the art.

[0003] However, the die structure upon which existing multi-pass drawing processes rely has a fundamental limitation: whether it's a single die or a series of multi-die schemes, the forming area of ​​each die is a single closed cavity. The copper wire enters from the inlet cone, passes through the sizing zone, and exits from the outlet. The entire contact process is continuous and uninterrupted. Under these closed and continuous contact conditions, the lubricating film on the surface of the copper wire is gradually broken and consumed under high normal pressure, and no intermediate replenishment can be obtained before the copper wire has completely passed through the die. At the same time, cooling and lubrication in existing drawing systems are usually independent. Cooling water flows through the water jacket on the outer wall of the mold, and lubricating grease is applied at the inlet end. The two cannot work together in the high-pressure contact area inside the mold. For trapezoidal cross-section copper wire, the compression in the short axis direction is large and the contact stress is concentrated. This area is precisely where the lubricating film is first squeezed out, and the frictional heat generation is the most intense. It is also the place where the coolant has the least reach. The rupture of the lubricating film leads to increased friction, which in turn leads to local temperature rise. The local temperature rise further deteriorates the lubrication conditions, thus forming a vicious cycle of high-temperature lubrication failure. Ultimately, this causes defects such as scratches and roughening on the surface of the copper wire and accelerates mold wear.

[0004] In summary, while existing technologies have established a basic framework for the macroscopic process route of multi-pass incremental forming, there are still structural technical problems that urgently need to be solved in terms of the intermediate replenishment mechanism of the lubricating film inside the mold cavity and the synergistic supply method of cooling and lubrication. Summary of the Invention

[0005] This invention provides a high-precision trapezoidal copper wire multi-pass progressive drawing equipment, which can solve the problems in the prior art where the forming area of ​​the drawing die is a single closed cavity, the lubricating film of the copper wire is gradually squeezed and consumed during continuous contact and cannot be replenished in the middle, and the cooling and lubrication are independent and cannot work together in the high-pressure contact area inside the die, resulting in a vicious cycle of high-temperature lubrication failure in the short axis direction of the trapezoidal section.

[0006] A high-precision trapezoidal copper wire multi-pass progressive drawing device includes: a worktable with a winding machine mounted on one side; multiple progressive components mounted on the worktable, each containing copper wire and including a tension adjustment component and a drawing component, which are alternately arranged; and a drawing component mounted on the worktable, including a cooling lubrication block and a drawing block. The multiple progressive components are divided into three stages along the drawing direction: a preliminary pass, a middle pass, and a final pass. The preliminary pass gradually compresses the circular cross-section of the copper wire into an elliptical cross-section; the middle pass gradually transitions the elliptical cross-section into a near-trapezoidal cross-section; and the final pass refines the near-trapezoidal cross-section into the target trapezoidal cross-section.

[0007] Preferably, the tension adjustment assembly includes a pair of brackets mounted on a workbench, with a rotating roller rotatably connected inside each bracket, the rotating roller abutting against the copper wire, and a tension adjuster installed at one end of each bracket, the tension adjuster being connected to the rotating roller.

[0008] Preferably, the drawing block has a drawing cavity, and multiple heat-conducting limiting rings are installed in the drawing cavity, with the inner diameter of the multiple heat-conducting limiting rings decreasing sequentially along the drawing direction. Preferably, a sealing airbag is installed inside the drawing cavity and on both sides of the plurality of heat-conducting limiting rings. The sealing airbag is located at the outer perimeter of the copper wire and abuts against the inner wall of the drawing cavity.

[0009] Preferably, the cooling and lubricating block is installed on the outside of the drawing block, the cooling and lubricating block has a pair of lubrication grooves, the lubrication grooves are filled with lubricating fluid, and a drive pump is installed in the lubrication grooves.

[0010] Preferably, the drawing cavity is provided with an injection port and a merging groove, the injection port is connected to the lubrication groove, and a one-way valve is installed in the injection port. Preferably, the cooling and lubrication block has a cooling groove, a cooler is installed in the cooling groove, and the cooling groove is connected to the lubrication groove and the cooling groove is connected to the inlet groove.

[0011] Preferably, an air pump is installed inside the cooling and lubrication block, and a sealing pipe is installed at one end of the sealing airbag, the sealing pipe being connected to the air pump.

[0012] Preferably, the inner diameter profile of the heat-conducting limiting ring of the preceding pass is elliptical, and the ratio of the major axis to the minor axis of the ellipse gradually increases along the pass direction. The working cone angle of the heat-conducting limiting ring of the preceding pass along the minor axis of the ellipse is greater than the working cone angle along the major axis.

[0013] Preferably, the inner diameter profile of the heat-conducting limiting ring in the middle section gradually transitions from an elliptical shape to a near-trapezoidal shape, and the four corners of the inner diameter profile of the heat-conducting limiting ring in the middle section are provided with transition fillets, the radius of which decreases sequentially within the middle section.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention replaces the traditional single closed cavity mold hole structure with multiple discrete heat-conducting limiting rings arranged at intervals along the axial direction. Each heat-conducting limiting ring undertakes only a small incremental cross-sectional deformation task. An open inter-ring gap space is formed between adjacent heat-conducting limiting rings. This structure allows the lubricating film on the surface of the copper wire to achieve dynamic self-repair by the wetting effect of the cooling lubricating fluid in the inter-ring gap space after each micro-deformation, instead of being continuously consumed and unable to be replenished before the entire deformation is completed, as is the case with the traditional closed cavity. As a result, the surface of the copper wire always maintains an effective lubricating film coverage, which significantly reduces the probability of surface roughening, scratches and other defects, and at the same time extends the service life of the mold.

[0015] (2) The present invention integrates cooling and lubrication in the same closed-loop fluid circuit, so that the cooling and lubricating fluid can simultaneously carry away frictional heat and maintain the lubricating film. The injection port of the cooling and lubricating fluid is specially arranged in the short axis direction of the drawing cavity, that is, the area with the largest deformation, the most concentrated frictional heat generation, and the most easily crushed lubricating film. This realizes the directional and coordinated supply of cooling and lubrication. The cooling and lubricating fluid automatically penetrates and replenishes the contact surface of each heat-conducting limiting ring through the gap between the rings under the pressure difference drive. This fundamentally breaks the situation in the traditional scheme where cooling and lubrication are independent and heat dissipation and lubrication failure occur in the high-pressure contact area. This effectively controls the local temperature rise in the short axis direction of the trapezoidal cross section and avoids the chain problems caused by high-temperature lubrication failure.

[0016] (3) Based on the differences in the cross-sectional shape characteristics of copper wire at different forming stages, the present invention configures two different sealing structures. In the first stage, the cross-section of copper wire is close to elliptical, with a smooth surface and no obvious sharp edges. An inflatable sealing airbag is used. The pressure inside the airbag makes the flexible sealing surface uniformly fit the smooth curved surface of the copper wire. At the same time, the friction between the airbag and the copper wire provides circumferential constraint and inhibits the copper wire from rotating around its own axis. In the middle and last stages, the cross-section of copper wire gradually shows trapezoidal features with sharp edges and a flat surface. A contoured elastic sealing element matching the cross-sectional profile is used. Its inner profile fits the straight and inclined sides of the trapezoidal cross-section. This achieves reliable sealing to maintain the pressure of the cooling lubricant in the cavity. It also provides a more definite anti-rotation effect through the surface contact constraint between the flat surface and the flat surface of the copper wire. The two sealing methods are connected in an orderly manner according to the forming stages, so that the sealing effect and anti-rotation capability remain effective throughout the entire process.

[0017] (4) The present invention implements a differentiated cone angle design on the working cone surface of the heat-conducting limiting ring. A larger working cone angle is set in the short axis direction to accelerate the material compression in the short axis direction, and a smaller working cone angle is set in the long axis direction to gently guide the material to expand moderately in the long axis direction. This directional cone angle difference is combined with the cooling and lubrication scheme of directional liquid injection in the short axis direction. While actively controlling the material flow direction, it ensures that the high deformation area receives sufficient cooling and lubrication support, thereby improving the filling fullness of the corner of the trapezoidal section, reducing the cross-sectional size deviation, and improving the geometric accuracy of the final product. Attached Figure Description

[0018] Figure 1 A schematic diagram of the three-dimensional structure of the workbench provided by the present invention; Figure 2 This is a schematic diagram of the three-dimensional structure of the progressive component provided by the present invention; Figure 3 A three-dimensional structural diagram of the tension adjustment component provided by the present invention; Figure 4 A three-dimensional structural diagram of the drawing assembly provided by the present invention; Figure 5 This is a schematic diagram of the pull block structure provided by the present invention; Figure 6 This is a schematic diagram of the cross-sectional structure of the drawing block provided by the present invention; Figure 7 A schematic diagram of the side structure of the drawing block provided by the present invention; Figure 8 This is a schematic diagram illustrating the change in the cross-sectional area of ​​the copper wire during the drawing process provided by the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Worktable; 2. Progressive assembly; 3. Tension adjustment assembly; 4. Pulling assembly; 5. Cooling and lubricating block; 6. Pulling block; 21. Copper wire; 31. Support; 32. Rotating roller; 33. Tension adjuster; 61. Pulling cavity; 62. Thermal limiting ring; 63. Sealing airbag; 64. Inlet; 65. Sealing pipe; 66. Merging groove. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0021] like Figures 1 to 4As shown in the embodiment of the present invention, the high-precision trapezoidal copper wire multi-pass progressive drawing equipment includes: a workbench 1, with a winding machine arranged on one side of the workbench 1; progressive components 2, multiple progressive components 2 are configured and installed on the workbench 1, each progressive component 2 contains a copper wire 21, and each progressive component 2 includes a tension adjustment component 3 and a drawing component 4, which are alternately arranged; and a drawing component 4, which is installed on the workbench 1 and includes a cooling lubrication block 5 and a drawing block 6. The multiple progressive components 2 are divided into three stages along the drawing direction: a first stage, a middle stage, and a final stage. The first stage is used to gradually compress the circular cross-section of the copper wire 21 into an elliptical cross-section, the middle stage is used to gradually transition the elliptical cross-section into a near-trapezoidal cross-section, and the final stage is used to refine the near-trapezoidal cross-section into the target trapezoidal cross-section.

[0022] like Figure 3 As shown, the tension adjustment assembly 3 includes a pair of brackets 31, which are mounted on the workbench 1. A rotating roller 32 is rotatably connected inside the bracket 31. The rotating roller 32 abuts against the copper wire 21. A tension adjuster 33 is installed at one end of the bracket 31 and is connected to the rotating roller 32.

[0023] In the multi-pass progressive drawing process, the copper wire 21 passes through multiple drawing components 4 in sequence. Each time it passes through a pass, its cross-sectional shape undergoes plastic deformation. Since the cross-section of the copper wire 21 gradually transitions from a circle to an ellipse and then to a near-trapezoidal shape in this scheme, the amount and direction of deformation between each pass are not consistent. Especially in the middle pass, the cross-sectional profile gradually transitions from a relatively uniform ellipse in all directions to a near-trapezoidal shape with varying widths in all directions. The amount of compression on the copper wire 21 in each direction begins to differ. Under these deformation conditions, if the copper wire 21 between two adjacent passes is in a free and relaxed state or the tension fluctuates greatly, the posture of the copper wire 21 when entering the next pass heat-conducting limiting ring 62 will be difficult to maintain stability, and the wire may be deviated. This can lead to deviations in cross-sectional dimensions or even scratches or breakage of the surface of the copper wire 21.

[0024] To address the above situation, this solution includes a tension adjustment assembly 3 between adjacent drawing assemblies 4. The tension adjustment assembly 3 includes a pair of brackets 31, which are fixedly mounted on the workbench 1. A rotating roller 32 is rotatably connected between the two brackets 31, and the copper wire 21 passes through and abuts against the surface of the rotating roller 32.

[0025] A tension regulator 33 is installed at one end of the bracket 31, and the tension regulator 33 is connected to the rotating roller 32. The tension regulator 33 is a servo drive device, which can drive the rotating roller 32 to move toward or away from the copper wire 21.

[0026] During the drawing process, the copper wire 21 abuts against the surface of the rotating roller 32 and forms a wrap-around contact section. When the tension regulator 33 drives the rotating roller 32 to move toward the copper wire 21 and further squeeze the copper wire 21, the clamping force on the copper wire 21 increases, and its tension in this section increases accordingly. When the tension regulator 33 drives the rotating roller 32 away from the copper wire 21 by a certain distance, the clamping force on the copper wire 21 decreases, and the tension decreases accordingly.

[0027] By controlling the degree of compression between the rotating roller 32 and the copper wire 21, the tension regulator 33 can continuously adjust the tension of the copper wire 21 between adjacent passes within a certain range. At the same time, a pressure sensor can be integrated into the rotating roller 32 to monitor its tension and is electrically connected to the tension regulator 33, thereby achieving the purpose of continuous monitoring and adjustment. This technology belongs to the prior art and will not be described in detail here.

[0028] The alternating arrangement of tension adjustment component 3 and drawing component 4 ensures that the inlet and outlet ends of each pass are under controlled tension. This is especially critical for the middle and final passes, as the copper wire 21 becomes more sensitive to the inlet posture after the cross-sectional shape has deviated from an ellipse.

[0029] Uneven tension may cause the copper wire 21 to deflect within the thermally conductive limiting ring 62, resulting in local dimensional deviations in the formed trapezoidal cross-section. The tension adjustment component 3 provides consistent wire feeding conditions for the copper wire 21 by maintaining a stable and adjustable tension level between passes, thereby ensuring the continuity of deformation in each pass and the dimensional accuracy of the final cross-section.

[0030] In actual production use, this device can be used in conjunction with a take-up drive unit and a winding machine to form a complete drawing production line. All of the above-mentioned supporting equipment adopts conventional structural forms in this field.

[0031] Each drawing assembly 4 is equipped with a lead-in drive unit at its lead-out end. The lead-in drive unit includes a servo motor and a lead-in wheel connected to it. The surface profile of the lead-in wheel is adapted to the cross-sectional shape of the lead-out copper wire 21 in the current pass, providing the copper wire 21 with the required drawing force to pass through each heat-conducting limiting ring 62 in that pass.

[0032] The linear speed of the take-up drive unit increases sequentially along the drawing direction, and the increase ratio matches the cross-sectional reduction rate of that pass. The servo motor of each take-up drive unit is linked with the pressure sensor signal in the tension adjustment component 3 to achieve coordinated control of the overall linear speed and tension.

[0033] Copper wire 21 undergoes work hardening during multiple consecutive drawing processes, and its elongation decreases with each pass as the cumulative deformation increases.

[0034] In this design, the interval between adjacent thermally conductive limiting rings 62 allows the copper wire 21 to experience brief stress release during continuous deformation. At the same time, the high thermal conductivity of the thermally conductive limiting rings 62, combined with the continuous cooling and lubricating fluid circulation, removes the deformation heat. The two work together to slow down the work hardening process, allowing the copper wire 21 to maintain a higher elongation margin under the same cumulative deformation, thus reducing the reliance on intermediate annealing.

[0035] When the total deformation is large and the elongation margin is close to the lower limit of the process, the copper wire 21 can be softened by the conventional online annealing process in the field between adjacent passes. The annealing equipment is arranged independently as a supporting equipment for the production line and belongs to the prior art, so it will not be described in detail here.

[0036] The winding machine is installed at the end of the workbench 1 on the wire exit side, including a winding reel and a winding motor that drives its rotation. The winding motor operates in a constant tension control mode to prevent secondary deformation or loosening of the trapezoidal cross section of the copper wire 21 on the reel. A wire guide is installed at the entrance of the winding reel to guide the copper wire 21 to be arranged evenly layer by layer. The winding speed is kept synchronized with the wire exit speed of the last pass drive unit through an encoder signal.

[0037] The aforementioned take-up drive unit and rewinder are both existing technologies in this field, and their specific structures and control methods are well known to those skilled in the art, so they will not be described in detail here.

[0038] like Figures 5 to 7 As shown, the inner diameter profile of the heat-conducting limiting ring 62 in the first pass is elliptical, and the ratio of the major axis to the minor axis of the ellipse gradually increases along the pass direction. The working cone angle of the heat-conducting limiting ring 62 in the first pass along the minor axis of the ellipse is greater than the working cone angle along the major axis.

[0039] The inner diameter profile of the heat-conducting limiting ring 62 in the middle section gradually transitions from an elliptical shape to a near-trapezoidal shape, and the four corners of the inner diameter profile of the heat-conducting limiting ring 62 in the middle section are provided with transition fillets, the radius of which decreases sequentially within the middle section.

[0040] The drawing block 6 has a drawing cavity 61 inside, and multiple heat-conducting limiting rings 62 are installed inside the drawing cavity 61. The inner diameter of the multiple heat-conducting limiting rings 62 decreases sequentially along the drawing direction. A sealing airbag 63 is installed inside the drawing cavity 61 and on both sides of multiple heat-conducting limiting rings 62. The sealing airbag 63 is located at the outer perimeter of the copper wire 21 and abuts against the inner wall of the drawing cavity 61.

[0041] The cooling and lubricating block 5 is installed on the outside of the drawing block 6. The cooling and lubricating block 5 has a pair of lubrication grooves, and the lubrication grooves are filled with lubricating fluid. A drive pump is installed in the lubrication grooves.

[0042] The drawing cavity 61 is provided with an injection port 64 and a merging groove 66. The injection port 64 is connected to the lubrication groove and a one-way valve is installed in the injection port 64. The cooling and lubrication block 5 has a cooling groove, a cooler is installed in the cooling groove, and the cooling groove is connected to the lubrication groove. The cooling groove is connected to the inlet groove 66. An air pump is installed in the cooling and lubrication block 5. A sealing pipe 65 is installed at one end of the sealing airbag 63 and is connected to the air pump.

[0043] Among them, such as Figure 8 As shown, S1 is the initial circular cross section; S2 is the first elliptical cross section of the front section; S3 is the second elliptical cross section of the front section; and S4 is the third elliptical cross section of the front section. S5 is the first transition section in the middle section, and S6 is the second near-trapezoidal section in the middle section; S7 is the final finished trapezoidal cross section; 'a' represents the major axis dimension of the ellipse, and 'b' represents the minor axis dimension of the ellipse. Width of the upper base of the trapezoid The width of the lower base of a trapezoid, H is the height of the trapezoidal cross section.

[0044] The core technological contradiction that this solution aims to resolve lies in the fact that the trapezoidal cross-section copper wire 21 has a narrow upper base and a wide lower base, and its geometric characteristics are naturally asymmetrical, while the initial circular cross-section copper wire 21 is completely symmetrical, resulting in a significant difference in shape between the two.

[0045] If a circular cross-section is directly drawn into a trapezoidal cross-section, the amount of compression that the copper wire 21 needs to withstand in each direction is vastly different. While the short side is subjected to severe compression, the long side is almost undeformed. This extremely uneven strain distribution will accumulate severe residual stress inside the cross-section, and the copper wire 21 will warp, twist, or even crack immediately after being demolded.

[0046] The root of this problem lies not in the magnitude of the drawing force or the choice of die material, but in the lack of a geometrically connected intermediate transition state between the circle and the trapezoid. The elliptical cross section can just serve as this intermediate role. It maintains the smooth continuity of the cross section profile and has already established the dimensional difference between the major axis and the minor axis, providing a reasonable starting point for the subsequent transition from symmetrical geometry to asymmetrical geometry.

[0047] Using the above method, this scheme divides the entire forming path into three stages: the front stage, the middle stage, and the final stage. The front stage passes gradually flatten the circular cross-section into an elliptical cross-section. The middle stage passes gradually correct the symmetrical contour of the elliptical cross-section into a near-trapezoidal contour that is narrow at the top and wide at the bottom. The final stage passes use minimal deformation to refine and shape the cross-section.

[0048] Copper wire 21 is led out from the wire feeding end on one side of the workbench 1 and passes through multiple drawing assemblies 2 arranged along the drawing direction in sequence. It should be noted that in the initial stage, the end of copper wire 21 can be flattened so that it can pass through the entire drawing assembly 2, and then it can be bound to the winding machine to facilitate subsequent drawing processing.

[0049] Each drawing assembly 2 contains a drawing assembly 4 and a tension adjustment assembly 3. Each time the copper wire 21 passes through a drawing assembly 2, it first undergoes a cross-sectional plastic deformation in the drawing assembly 4, and then completes tension stabilization in the tension adjustment assembly 3. The two are arranged alternately until the copper wire 21 is drawn out from the last pass and then wound up by the winding machine.

[0050] In the previous pass, multiple heat-conducting limiting rings 62 are installed in the drawing cavity 61 of the drawing block 6 inside the drawing assembly 4. The inner diameter profile of each heat-conducting limiting ring 62 is elliptical, and the ratio of the major axis to the minor axis of the ellipse gradually increases along the pass direction. That is, the later the previous pass, the flatter the ellipse of the heat-conducting limiting ring 62 becomes, and the cross section of the copper wire 21 is stretched in each pass.

[0051] To achieve directional flattening of the circular cross-section rather than isotropic proportional reduction, an elliptical inner diameter profile alone is insufficient; directional differences must also be introduced on the working cone surface of the thermally conductive limiting ring 62.

[0052] Each thermally conductive limiting ring 62 has an inwardly tapered working surface on its inlet side. The function of this tapered surface is to guide the copper wire 21 to smoothly transition from the larger cross section of the previous stage to the smaller cross section defined by the inner diameter of the current thermally conductive limiting ring 62.

[0053] For traditional circular drawing dies, the working cone surface is rotationally symmetrical about the central axis, and its cone angle is completely consistent in any radial direction. However, in this scheme, the working cone surface of the elliptical heat-conducting limiting ring 62 is not a rotationally symmetrical body, but a three-dimensional curved surface with a cone angle that changes continuously along the circumference.

[0054] When the copper wire 21 is pulled into the thermally conductive limiting ring 62, it encounters the steepest conical wall in the short axis direction, where the radial compression rate is the greatest; the conical wall encountered in the long axis direction is the gentlest, where the radial compression rate is the smallest; as the copper material is rapidly compressed in the short axis direction, it is guided by the smaller resistance in the long axis direction and flows preferentially in that direction, so the circular cross-section is gradually flattened into an ellipse in multiple passes.

[0055] While solving the problem of directional flattening, this differentiated cone angle design inevitably leads to a tricky side effect: the contact pressure between the mold wall and the copper wire 21 in the short axis direction is significantly higher than that in the long axis direction.

[0056] High contact pressure brings two simultaneous and coupled problems: First, frictional heat is concentrated, with the temperature rise in the short axis direction being much greater than that in the long axis direction. Local high temperature accelerates mold wear and affects the surface quality of copper wire 21. Second, the lubricating film is more likely to be squeezed thin or even broken under high pressure, causing the lubrication state in the short axis direction to degenerate from fluid lubrication to boundary lubrication or even dry friction.

[0057] The two problems mentioned above create a vicious cycle in the short axis direction: the increase in temperature leads to a decrease in the viscosity of the lubricant, the decrease in viscosity weakens the load-bearing capacity of the lubricating film, the lubrication failure exacerbates friction and heat generation, the temperature rises further, and the final result is rapid wear in the short axis area of ​​the thermally conductive limiting ring 62 and oxidation and discoloration of the surface of the copper wire 21.

[0058] If cooling and lubrication are two separate systems, such as cooling water flowing through the outer wall of the mold and grease being applied at the mold inlet, the cooling path is long and the thermal resistance is high. The cooling water cannot directly contact the short shaft contact surface where the heat is most severe, and the statically applied grease cannot be continuously replenished in the high-pressure area. The two systems work independently and neither can effectively intervene in the short shaft area where the problem is most severe.

[0059] This solution integrates cooling and lubrication functions into the same fluid circuit. Each drawing assembly 4 consists of a drawing block 6 and a cooling and lubrication block 5 installed on its outer side.

[0060] A pair of lubrication grooves are provided on the cooling and lubrication block 5. The grooves store liquid medium that has both cooling and lubrication functions. A drive pump is installed in the lubrication groove. An injection port 64 is provided on the drawing cavity 61 in the drawing block 6. The injection port 64 is arranged on both sides along the minor axis of the elliptical cross section of the heat-conducting limiting ring 62 and is connected to the lubrication groove. A one-way valve is installed in the injection port 64.

[0061] If a single closed cavity is used as the forming die hole in the drawing cavity 61, although the structure is simple, the contact between the copper wire 21 and the inner wall of the closed cavity is continuous and closed. Cooling lubricant cannot continuously enter the contact surface from the outside. Especially in the short axis direction, the continuous high contact pressure will gradually break the lubricating film initially attached to the surface of the copper wire 21. The closed cavity structure does not provide any space for intermediate replenishment of lubricating film. Once the lubricating film fails at a certain point, that point will enter a dry friction state and cannot recover on its own.

[0062] To address this, this solution replaces a single closed cavity with multiple discrete thermally conductive limiting rings 62 arranged inside the drawing cavity 61 along the direction of copper wire 21 travel. The axial length of the drawing cavity 61 is much greater than the thickness of a single thermally conductive limiting ring 62. Each thermally conductive limiting ring 62 is installed inside the cavity at a certain interval, with its inner diameter decreasing sequentially along the drawing direction. Each time the copper wire 21 passes through a thermally conductive limiting ring 62, it only completes a small cross-sectional reduction once. The cascading effect of multiple thermally conductive limiting rings 62 decomposes the total deformation of a single pass into several small increments.

[0063] The design of using multiple discrete thermally conductive limiting rings 62 instead of a single continuous channel has the core advantage of not only the gradual distribution of deformation, but also the fundamental improvement of heat dissipation and lubrication conditions. In a single continuous channel, the contact surface between the copper wire 21 and the mold wall is a continuous strip-shaped area, and frictional heat accumulates continuously along the entire contact length. Meanwhile, the cooling lubricant can only seep in from both ends of the channel, making it difficult to reach the middle section, which is the area most in need of cooling.

[0064] In the discrete layout of this scheme, the axial thickness of each thermally conductive limiting ring 62 is limited, the contact stroke of the copper wire 21 through a single thermally conductive limiting ring 62 is extremely short, and the contact time is correspondingly extremely short. The frictional heat generated by a single contact is limited and will not form a serious temperature accumulation in a local area.

[0065] More importantly, the gap between adjacent thermally conductive limiting rings 62 forms a natural storage cavity for cooling and lubricating fluid. After the copper wire 21 passes through a thermally conductive limiting ring 62, it immediately enters the gap space filled with cooling and lubricating fluid. Its entire outer surface is encased and immersed in the liquid. The heat brought by the previous thermally conductive limiting ring 62 is quickly absorbed and carried away by the liquid. At the same time, a new lubricating film is re-established on the surface of the copper wire 21, preparing it for entering the next thermally conductive limiting ring 62.

[0066] This alternating rhythm of short contact, sufficient cooling, and then short contact keeps the temperature of the copper wire 21 at a low level throughout the drawing chamber 61, avoiding the problem of temperature gradually rising in the continuous contact mode.

[0067] The thermally conductive limiting ring 62 itself is made of a material with high thermal conductivity. This material selection is not only for the wear resistance of the ring body, but also to make the thermally conductive limiting ring 62 itself a component of the heat dissipation path.

[0068] The frictional and deformation heat generated when the copper wire 21 contacts the inner surface of the thermally conductive limiting ring 62 is rapidly conducted to the outer surface through the high thermal conductivity path of the ring. The outer surface is directly exposed to the cooling lubricant filled in the drawing cavity 61. The heat is thus transferred through the extremely short path of the inner surface of the thermally conductive limiting ring 62, the ring wall thickness, the outer surface, and the liquid. The thermal resistance is extremely low, which allows the working surface temperature of the thermally conductive limiting ring 62 to be rapidly reduced.

[0069] Furthermore, in order to enhance the heat dissipation capacity of the thermally conductive limiting ring 62 and improve the flow conditions of the cooling lubricant between the gaps, auxiliary flow channels can be opened on the ring body of the thermally conductive limiting ring 62.

[0070] These flow channels extend axially through the thickness of the ring body and are located in the outer peripheral region of the ring body, near the inner wall of the drawing cavity 61, connecting the gap space on the inlet side of the heat-conducting limiting ring 62 with the gap space on the outlet side.

[0071] The flow channel allows the coolant to flow between adjacent gaps without having to completely circulate around the outer periphery of the copper wire 21, eliminating potential local liquid stagnation areas and improving the overall circulation efficiency of the liquid. At the same time, since the liquid comes into direct contact with the ring material as it passes through the inside of the ring, it can absorb the heat conducted by the ring more efficiently.

[0072] Furthermore, shallow microgrooves can be circumferentially arranged at the inlet edge of the inner surface of the heat-conducting limiting ring 62. The dragging effect generated by the movement of the copper wire 21 introduces the cooling lubricant from the gap space into the conical contact area, further improving the lubrication conditions at the working conical surface. It is important to note that the dimensions and number of the auxiliary flow channels and shallow microgrooves should be rationally designed. The location of the flow channels should be far from the inner diameter sizing area, and the depth of the shallow microgrooves should be controlled within a range that does not affect the surface forming accuracy of the copper wire 21, ensuring that the structural strength and forming function of the ring are not significantly affected by the opening of the channels.

[0073] The reason why the injection inlet 64 is specifically set in the short axis direction rather than being evenly distributed along the circumference is because the short axis direction is the area with the highest contact pressure, the most severe temperature rise, and the most easily broken lubricating film. Injecting the coolant and lubricating fluid from this direction can directly act on the location with the most severe problem with the shortest flow path.

[0074] The gap space between adjacent thermally conductive limiting rings 62 provides volume for the flow and accumulation of cooling lubricant. The cooling lubricant fully soaks the outer surface of the copper wire 21 in the gap. When the local contact pressure of a certain thermally conductive limiting ring 62 squeezes the lubricating film thin, the liquid in the adjacent gap space automatically replenishes the area under the pressure difference, forming a dynamic self-healing lubricating film.

[0075] This self-compensating capability in the structure is something that a single closed mold hole does not possess, making the lubrication reliability of the 62-group thermally conductive limiting rings far superior to that of traditional molds.

[0076] After the cooling lubricant is injected into the drawing cavity 61, it faces an unavoidable problem: the liquid is fluid, and if left unrestrained, it will leak out from the inlet and outlet ends of the drawing cavity 61 along the axial direction of the copper wire 21.

[0077] Leakage at the inlet end contaminates the upstream copper wire 21, and leakage at the outlet end affects the downstream environment. More importantly, leakage will cause the liquid pressure in the working area of ​​the heat-conducting limiting ring 62 to drop, and the lubricating film cannot be maintained. However, the copper wire 21 is a continuously moving wire, and a rigid seal cannot be set on its outer periphery. Otherwise, the edge of the seal will carve grooves on the surface of the copper wire 21, which will damage the cross-sectional accuracy.

[0078] In the previous stage, the cross-section of the copper wire 21 is circular or elliptical, with a smooth and continuous outline and no sharp edges. Therefore, in this solution, a sealing airbag 63 is installed in the drawing cavity 61 of the previous stage and at both ends of multiple heat-conducting limiting rings 62. The sealing airbag 63 surrounds the outer periphery of the copper wire 21, and its outer surface abuts against the inner wall of the drawing cavity 61.

[0079] A sealing pipe 65 is installed at one end of the sealing airbag 63. The sealing pipe 65 is connected to the air pump inside the cooling and lubrication block 5. The air pump fills the sealing airbag 63 with compressed gas through the sealing pipe 65. After the sealing airbag 63 expands, its inner surface flexibly adheres to the outer surface of the copper wire 21 with uniformly distributed surface pressure, and its outer surface is tightly attached to the inner wall of the cavity. This forms a closed barrier at both ends of the heat-conducting limiting ring 62 group, locking the cooling and lubricating fluid within the effective working range of the heat-conducting limiting ring 62.

[0080] Because the airbag applies force by air pressure, the contact pressure is uniform and adjustable. It will not leave indentations on the surface of the copper wire 21, and it can adapt to the difference in cross-sectional size of the copper wire 21 in different front-end passes. There is no need to make special seals for the cross-sectional specifications of each pass.

[0081] The sealing airbag 63, while fulfilling its sealing function, also constrains the rotational attitude of the copper wire 21. In the previous pass, the cross-section of the copper wire 21 is already a non-circular ellipse. The inner cavity of the sealing airbag 63 is correspondingly designed to match the current cross-sectional shape of the copper wire 21 with an elliptical contour. After the airbag is inflated and fits against the copper wire 21, it naturally forms an inner cavity that matches the elliptical cross-section. If the copper wire 21 attempts to rotate around its axis, its non-circular cross-section will geometrically interfere with the inner cavity of the airbag and be prevented. Thus, the sealing airbag 63 simultaneously performs the functions of sealing and anti-rotation in the previous pass, eliminating the need for a separate anti-torsion device between passes.

[0082] However, as the forming path progresses from the initial passes to the middle and final passes, the cross-sectional profile of the copper wire 21 gradually transitions from a smooth ellipse to a near-trapezoidal shape with distinct edges, and finally to a trapezoid. The working conditions faced by the sealing airbag 63 have undergone fundamental changes. In the later stages of the middle and final stages of the track, the cross-section of the copper wire 21 has become quite sharp. If the inflatable airbag is still used to seal the outer periphery of the copper wire 21, the flexible membrane material of the airbag will be subjected to highly concentrated stress in the corner area. The sharp corners of the cross-section are very likely to puncture the inner membrane of the airbag or accelerate fatigue wear, leading to the failure of the airbag seal.

[0083] Even if the airbag can remain intact in the short term, it is difficult to ensure uniform adhesion between the airbag membrane and the surface of the copper wire 21 at the corner, which can easily create tiny gaps at the root of the corner, thus creating a leakage channel.

[0084] Therefore, the sealing airbag 63 is only applicable to the stage in the early track where the cross-section of the copper wire 21 is circular or elliptical and the outline is smooth without sharp edges, and is not applicable to the later stage in the middle track and the stage in the final track where the cross-section of the copper wire 21 has obvious sharp edges.

[0085] To address the sealing requirements of the middle and final passes, this solution replaces the sealing airbag 63 with a contoured elastic seal that matches the cross-sectional shape of the copper wire 21 in the current pass. The inner bore contour of the contoured elastic seal is pre-processed according to the cross-sectional shape of the copper wire 21 in the corresponding pass, including the transition fillets at the corners, which are all geometrically consistent with the cross-section of the copper wire 21. The sealing material is a wear-resistant elastomer with a certain degree of elasticity but a hardness higher than that of the airbag membrane material.

[0086] During installation, the outer surface of the contoured elastic seal is fixed to the inner wall of the pull-out cavity 61, and the inner hole is slightly interference-fitted to the outer surface of the copper wire 21, relying on the elastic deformation of the material itself to provide sealing surface pressure. Because the inner hole profile matches the cross-sectional geometry of the copper wire 21, the contact at the corners is surface contact rather than point or line contact, avoiding stress concentration and bidirectional damage to both the seal and the surface of the copper wire 21. Although the contoured elastic seal needs to be manufactured separately for different cross-sectional specifications, the variation range of the cross-sectional shape in the middle and final passes is significantly narrower than that in the earlier passes, the required number of specifications is limited, and the manufacturing and spare parts costs are controllable.

[0087] It should be further pointed out that the deformation of a single pass in the middle and final passes is significantly reduced compared to the previous passes, especially the deformation of the final pass, which is minimal and only involves finishing and shaping. Therefore, the amount of frictional heat and deformation heat generated in these passes is much lower than that in the previous passes, and the requirements for the flow rate and pressure of the cooling and lubricating fluid are correspondingly reduced.

[0088] Even though the dynamic sealing capability of the contoured elastic seal is slightly inferior to that of the self-adaptive fit of the inflatable bladder, it can still meet the leakage prevention requirements under lower liquid pressure conditions.

[0089] Meanwhile, the pre-formed inner hole profile of the contoured elastic seal naturally has an anti-rotation function. In the middle and final passes, there is a clear geometric constraint relationship between the near trapezoidal or trapezoidal cross section of the copper wire 21 and the matching inner hole of the seal. The asymmetrical profile, which is narrow at the top and wide at the bottom, prevents the copper wire 21 from rotating freely within the seal. The attitude control requirements are also met without adding any additional anti-torsion devices.

[0090] After the cooling lubricant flows through the contact area between the thermally conductive limiting ring 62 and the copper wire 21 in the drawing cavity 61, it absorbs the deformation heat and frictional heat, and the temperature rises.

[0091] The heat-carrying liquid flows out from the inlet groove 66 inside the drawing chamber 61 and enters the cooling groove on the cooling lubrication block 5. The cooler installed in the cooling groove cools the liquid to the set temperature. The cooled liquid flows back to the lubrication groove, is repressurized by the drive pump, and is injected back into the drawing chamber 61 through the injection port 64, forming a closed loop circulation from the lubrication groove, injection port 64, drawing chamber 61, inlet groove 66, cooling groove to lubrication groove.

[0092] The circulation allows the cooling lubricant to continuously carry away heat during its continuous flow, maintaining a stable temperature in the area of ​​the thermally conductive limiting ring 62. At the same time, the liquid is filtered during circulation to remove copper shavings particles generated by plastic deformation, preventing copper shavings from causing secondary scratches on the surface of the copper wire 21. This technology is existing technology and will not be described in detail here.

[0093] In the middle section, the inner diameter profile of each heat-conducting limiting ring 62 gradually transitions from an elliptical shape to a near-trapezoidal shape. Based on the differentiated dimensions of the major and minor axes established in the previous section, the middle section begins to break the vertical symmetry of the cross-section. The upper arc of the inner diameter profile of the heat-conducting limiting ring 62 gradually becomes straight and narrows, while the lower arc remains or slightly widens, and the cross-sectional profile gradually shows a trend of being narrower at the top and wider at the bottom.

[0094] During this transition process, transition fillets are provided at the four corners of the inner diameter contour of the heat-conducting limiting ring 62. The radius of the transition fillets decreases sequentially in the middle section. The reason why a sharp trapezoidal right angle is not set directly at the beginning of the middle section is that when the corner material of the copper wire 21 suddenly flows from the smooth elliptical arc into the sharp corner, it will generate a severe local strain concentration, which is very easy to cause corner cracking.

[0095] By gradually reducing the fillet radius in multiple passes, the corner material is only compacted and shaped in each pass, and the strain increment is always within a controllable range until the final finishing pass brings the fillet to the final target value. The copper wire 21 obtains a clear trapezoidal edge, and the corner material does not experience local deformation beyond its plastic limit.

[0096] The inner diameter profile of the heat-conducting limiting ring 62 in the final pass is the final target trapezoidal size, with minimal deformation. Only the cross-section is finalized and the surface is smoothed. After the copper wire 21 exits the mold, the cross-sectional shape is stable and almost no springback occurs.

[0097] The following is one set of process parameters for this scheme, which is used to illustrate the implementation process of this scheme. The starting wire is selected as electrical oxygen-free copper round wire with a diameter of 3.5mm and an elongation of not less than 35%. The target cross-section is a trapezoid with a top width of 1.8mm, a bottom width of 3.2mm, and a height of 2.0mm, and the four corner radii are 0.15mm.

[0098] Seven drawing components 4 are arranged sequentially along the workbench 1 throughout the entire process, divided into three passes in the front section, two passes in the middle section, and two passes in the final section.

[0099] In the first stage of the drawing process, the inner diameter of each heat-conducting limiting ring 62 in the drawing cavity 61 is elliptical, gradually flattening the circular cross-section. The reduction rate of the cross-section in a single stage is controlled between 6.5% and 7.2%, and the cumulative reduction rate in the first stage is about 19.2%. Each drawing cavity 61 is equipped with 5 heat-conducting limiting rings 62, so that the reduction increment borne by a single ring is about 1.4%.

[0100] When the cumulative deformation of the current stage is large and the elongation margin of copper wire 21 is close to the lower limit of the process, the copper wire 21 can be softened by the conventional online annealing process in the field between the previous stage and the middle stage to restore its plasticity reserve. The annealing equipment is arranged independently as a supporting production line.

[0101] In the intermediate passes, the inner diameter profile of the heat-conducting limiting ring 62 transitions to a near-trapezoidal shape, with a single pass reduction rate of 5.9% to 8.0%, and the corner radius gradually decreases from 0.6 mm to 0.3 mm.

[0102] The last two passes are mainly for finishing and shaping. Each drawing cavity 61 is equipped with 3 heat-conducting limiting rings 62. The single-pass reduction rate is only 2.9% to 3.2%, the single-ring reduction increment does not exceed 1.0%, the fillet radius is reduced to the target value of 0.15mm, and the total cross-sectional reduction rate of the whole process is about 48.0%.

[0103] All thermally conductive limiting rings 62 are made of tungsten-cobalt cemented carbide with a thermal conductivity of not less than 80 W / (m·K). The axial thickness of the ring body is 5 mm, and the gap between adjacent rings is 10 mm. The working cone angle half-angle in the short axis direction of the first pass is 12° and in the long axis direction is 6°. The working cone angle in the height direction of the middle pass is 10° and in the width direction is 5°. The working cone angle in the last pass is uniformly 4° to 5°. The inner wall of the drawing cavity 61 is machined with stepped positioning steps along the axial direction. Each step is bored in the same clamping. The coaxiality deviation between the steps does not exceed 0.005 mm. The outer circle of each thermally conductive limiting ring 62 is fitted into the step with a transition fit. The non-circular cross-section ring body is locked in the angular position by the positioning keyway on the outer circle to ensure the consistency of the axis and angular direction of each ring in the same cavity.

[0104] Cooling lubricant is injected through the injection port 64 on each drawing chamber 61, with a supply pressure of 0.3–0.6 MPa, a single chamber circulation flow rate of 2–5 L / min, and a reflux temperature controlled at 25°C ± 2°C. After passing through each thermally conductive limiting ring 62, the copper wire 21 enters a 10 mm interval, which is filled with pressurized lubricant. Based on the previous pass linear velocity of 30–60 m / min, the time for the copper wire 21 to pass through this interval is approximately 0.01–0.02 s. Under the aforementioned supply pressure, this is sufficient to reform a liquid film layer on the surface of the copper wire 21 that meets the lubrication requirements of the next ring inlet.

[0105] The first section uses a sealing airbag 63 to block the inlet and outlet of the wires, with an inflation pressure of 0.08 to 0.20 MPa; the middle and last sections use a contoured elastic seal to achieve sealing because the cross-section of the copper wire 21 is no longer circular.

[0106] The drawing speed of the drive unit for each pass increases sequentially along the line: 30-60 m / min in the first section, 50-90 m / min in the middle section, and 80-120 m / min in the last section. The tension is maintained at 8%-15% of the yield load of the current section of the copper wire 21 by the tension adjustment component 3 between passes.

[0107] Under the above parameters, the average service life of the thermally conductive limiting ring 62 is enhanced, which is significantly improved compared with the traditional single closed die hole solution.

[0108] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A high-precision trapezoidal copper wire multi-pass progressive drawing equipment, characterized in that, include: A workbench (1) is provided with a winding machine on one side of the workbench (1); A progressive component (2) is provided, and multiple progressive components (2) are installed on a workbench (1). A copper wire (21) is provided inside the progressive component (2). The progressive component (2) includes a tension adjustment component (3) and a pulling component (4). The tension adjustment component (3) and the pulling component (4) are arranged alternately. A drawing assembly (4) is mounted on a workbench (1) and includes a cooling lubrication block (5) and a drawing block (6). Among them, the multiple progressive components (2) are divided into three stages along the drawing direction: the first stage, the middle stage, and the last stage. The first stage is used to gradually compress the circular cross-section of the copper wire (21) into an elliptical cross-section. The middle stage is used to gradually transition the elliptical cross-section into a near-trapezoidal cross-section. The last stage is used to refine the near-trapezoidal cross-section into the target trapezoidal cross-section.

2. The high-precision trapezoidal copper wire multi-pass progressive drawing equipment as described in claim 1, characterized in that, The tension adjustment assembly (3) includes a pair of brackets (31), which are mounted on the workbench (1). A rotating roller (32) is rotatably connected inside the bracket (31). The rotating roller (32) abuts against the copper wire (21). A tension adjuster (33) is installed at one end of the bracket (31), and the tension adjuster (33) is connected to the rotating roller (32).

3. The high-precision trapezoidal copper wire multi-pass progressive drawing equipment as described in claim 1, characterized in that, The drawing block (6) has a drawing cavity (61) inside, and multiple heat-conducting limiting rings (62) are installed inside the drawing cavity (61). The inner diameter of the multiple heat-conducting limiting rings (62) decreases sequentially along the drawing direction.

4. The high-precision trapezoidal copper wire multi-pass progressive drawing equipment as described in claim 3, characterized in that, A sealing airbag (63) is installed inside the drawing cavity (61) and on both sides of the multiple heat-conducting limiting rings (62). The sealing airbag (63) is located at the outer perimeter of the copper wire (21) and abuts against the inner wall of the drawing cavity (61).

5. The high-precision trapezoidal copper wire multi-pass progressive drawing equipment as described in claim 3, characterized in that, The cooling and lubricating block (5) is installed on the outside of the drawing block (6). The cooling and lubricating block (5) has a pair of lubrication grooves, and the lubrication grooves are filled with lubricating liquid. A drive pump is installed in the lubrication grooves.

6. The high-precision trapezoidal copper wire multi-pass progressive drawing equipment as described in claim 5, characterized in that, The drawing cavity (61) is provided with an injection port (64) and a merging groove (66). The injection port (64) is connected to the lubrication groove, and a one-way valve is installed in the injection port (64).

7. The high-precision trapezoidal copper wire multi-pass progressive drawing equipment as described in claim 5, characterized in that, The cooling and lubrication block (5) has a cooling groove, a cooler is installed in the cooling groove, and the cooling groove is connected to the lubrication groove and the cooling groove is connected to the inlet groove (66).

8. The high-precision trapezoidal copper wire multi-pass progressive drawing equipment as described in claim 4, characterized in that, An air pump is installed inside the cooling and lubrication block (5), and a sealing pipe (65) is installed at one end of the sealing airbag (63), and the sealing pipe (65) is connected to the air pump.

9. The high-precision trapezoidal copper wire multi-pass progressive drawing equipment as described in claim 3, characterized in that, The inner diameter profile of the heat-conducting limiting ring (62) of the preceding pass is elliptical, and the ratio of the major axis to the minor axis of the ellipse gradually increases along the pass direction. The working cone angle of the heat-conducting limiting ring (62) of the preceding pass along the minor axis of the ellipse is greater than the working cone angle along the major axis.

10. The high-precision trapezoidal copper wire multi-pass progressive drawing equipment as described in claim 3, characterized in that, The inner diameter profile of the heat-conducting limiting ring (62) in the middle section gradually transitions from an elliptical shape to a near-trapezoidal shape, and the four corners of the inner diameter profile of the heat-conducting limiting ring (62) in the middle section are provided with transition rounded corners, the radius of which decreases sequentially within the middle section.

Images