A tension-assisted self-centering device and self-centering method for cold-drawing dies

Abstract

The application relates to a wire cold drawing processing technology field, in particular to a tension auxiliary self-centering device and self-centering method for a cold drawing die. The device comprises an upper driving wheel set, a lower driving wheel set, a die frame, a floating die, a rolling support element, an upper support plate, a lower support plate, a cushion block and upper and lower retaining frames. V-shaped grooves of the upper and lower driving wheel sets form two wire constraint points, and the floating die is located between the two constraint points; an axial floating gap is arranged through the cushion block, so that the floating die can move along a support plane perpendicular to a die hole axis under the rolling support. When a die hole axis produces a transverse offset relative to a wire guide axis, a transverse resultant force of the wire segments on both sides of the die towards the wire guide axis is generated; when the transverse resultant force is greater than an equivalent rolling resistance, the floating die is pushed to move in a direction of reducing the offset. The application does not need to set a detection sensor and an independent deviation correction driving source, and is favorable for inhibiting die wear and improving drawing stability.

Description

Technical Field

[0001] This application relates to the field of cold drawing technology for metal wires, and in particular to a tension-assisted self-centering device and self-centering method for cold drawing dies. Background Technology

[0002] In the cold drawing process of metal wire, the alignment accuracy of the die directly determines the dimensional uniformity, surface quality, and service life of the wire. Traditional cold drawing equipment typically uses a rigid fixing method to install the die, that is, locking the die position through precision-machined die seats and fasteners. In actual operation, to ensure that the wire passes smoothly through the die hole, high-precision part machining dimensions and tedious manual assembly and adjustment are often relied upon to initially achieve axis alignment. Some existing technical solutions also introduce mechanical tension sensing mechanisms or sensor-based active adjustment systems, which detect the wire's running status and control the actuators to fine-tune the die position to maintain alignment. These solutions can, to a certain extent, meet the alignment requirements in the production process and constitute the main technical means in the industry today.

[0003] However, existing rigid dies are prone to slight deviations between the die hole axis and the wire guide axis due to equipment vibration, accumulated assembly errors, or fluctuations in the wire's trajectory. Once this deviation occurs, the load on one side of the die increases, potentially leading to further wear. While active correction using sensors and actuators can adjust the die position, it increases structural complexity, control delay, and maintenance costs. Therefore, a technical solution is needed that utilizes the existing tension during the drawing process to enable low-resistance movement of the die along the wire guide axis without adding an independent correction power source. Summary of the Invention

[0004] This application provides a tension-assisted self-centering device and self-centering method for cold drawing dies to solve the above-mentioned problems.

[0005] In a first aspect, this application provides a tension-assisted self-centering device for cold drawing dies, the device comprising:

[0006] Upper drive wheel assembly, lower drive wheel assembly, mold frame, floating mold, rolling support element, upper support plate, lower support plate, pad block, upper retainer and lower retainer;

[0007] The upper support plate and the lower support plate are mounted on the mold frame and are spaced apart by the pads; the rolling support elements are respectively limited by the upper retainer and the lower retainer, and are located on the upper and lower sides of the floating mold;

[0008] The floating mold is housed between rolling support elements on the upper and lower sides, and the floating mold has a mold hole for the wire to pass through; let the distance between the upper and lower support plates determined by the pad be H, the thickness of the floating mold along the mold hole axis be h, and the diameter of the rolling support element be D, then the axial floating gap δ=Hh-2D;

[0009] Both the upper drive wheel assembly and the lower drive wheel assembly are provided with V-grooves with small rounded corners at the bottom. The wire passes through the V-grooves of the upper drive wheel assembly, the die hole of the floating mold, and the V-grooves of the lower drive wheel assembly in sequence. The guide axis of the wire is determined by the two constraint points formed by the upper and lower V-grooves.

[0010] When the die hole axis shifts laterally relative to the wire guide axis, the tension wire segments on both sides of the floating die form a resultant lateral force toward the wire guide axis in the support plane;

[0011] When the lateral resultant force is greater than the equivalent rolling resistance generated by the rolling support element, the floating mold moves on the rolling support element in the direction of reducing lateral offset until the deviation is reduced to the allowable range.

[0012] With the above structure, the floating die is changed from a rigid fixed position to a low-resistance rolling support. When a deviation occurs, the drawing tension is converted into a lateral restoring effect, eliminating the need for a separate deviation detection sensor and correction actuator. The axial floating clearance prevents the floating die from rigid clamping between the upper and lower supports, while the support plane limits the floating die to primarily lateral movement. This helps reduce the starting resistance of the die to minor deviations, suppresses the continuous accumulation of unilateral loads, and improves the stability of the drawing process.

[0013] Optionally, the rolling support element is a ball, roller, or needle roller, and is made of bearing steel, hard alloy, or ceramic material; the equivalent rolling friction coefficient μr between the rolling support element and the floating mold is less than 0.01.

[0014] Employing a support structure with a low equivalent rolling friction coefficient reduces the restoring force required for the floating mold to begin lateral movement. Balls are suitable for multi-directional rolling, while rollers and needle rollers are suitable for applications with a primary direction of movement or limited installation space. The specific form can be determined based on the floating mold mass, support dimensions, and drawing tension.

[0015] Optionally, the rolling support element is a ceramic ball, and multiple ceramic balls are distributed at intervals along the circumference of the floating mold in a support plane perpendicular to the mold hole axis, and are respectively limited by an upper retainer and a lower retainer.

[0016] The ceramic balls have high hardness and low density, and the cage keeps each ceramic ball in a predetermined position while preserving its rotational freedom. The upper and lower sets of ceramic balls respectively constitute the support and axial limit, making it less likely for the floating mold to tilt significantly during lateral movement.

[0017] Optionally, the ceramic ball is a silicon nitride ceramic ball with a diameter of 2mm, and 6 silicon nitride ceramic balls are respectively arranged on the upper and lower sides of the floating mold.

[0018] The aforementioned dimensions and quantity can create multi-point rolling supports within a limited installation space and distribute the normal load of the floating mold. In practical applications, the size and quantity of ceramic balls can also be adjusted according to the mold's outer diameter, mass, and allowable contact stress.

[0019] Optionally, the axial floating clearance δ is 0.01 mm to 0.1 mm.

[0020] The axial floating clearance is used to compensate for manufacturing and assembly deviations in the diameter of the rolling support element, the thickness of the floating mold, and the thickness of the pad, and to prevent the upper and lower sets of rolling support elements from rigidly clamping the floating mold at the same time; the clearance is not the same as the lateral movement stroke of the floating mold in the support plane.

[0021] Optionally, the axial floating gap δ is 0.02 mm to 0.05 mm; in the case of ultrafine wire drawing, the axial floating gap δ is 0.03 mm.

[0022] By controlling the axial floating clearance within the aforementioned range, it is possible to prevent the floating mold from being axially clamped while limiting its movement along the mold hole axis. This clearance can be obtained by selecting the thickness of the shim or by precision grinding the shim.

[0023] Optionally, the wire drawing direction is parallel to the gravity direction, and the supporting plane of the floating mold is perpendicular to the gravity direction; the V-groove of the upper and lower drive wheel sets has the same external dimensions and axial position alignment, and the small fillet transition radius at the bottom of the V-groove is R0.1mm.

[0024] In the static installation state, the gravity of the floating mold does not form a lateral component force in the support plane, but only serves as a normal load for rolling contact. In the drawing state, the tension difference between the upper and lower wire segments can also change the normal force between the floating mold and the upper or lower rolling support element along the die hole axis. The small rounded corner at the bottom of the V-groove is used to reduce local stress concentration at the contact point between the wire and the bottom of the groove.

[0025] Secondly, this application provides a tension-assisted self-centering method for cold drawing dies, the method comprising:

[0026] The spacing between the upper and lower support plates is set by using pads to ensure that the axial floating clearance δ satisfies δ=Hh-2D, and the floating mold is set to be able to move in a support plane perpendicular to the mold hole axis.

[0027] The wire is made to pass through the V-groove of the upper drive wheel set, the die hole of the floating mold, and the V-groove of the lower drive wheel set in sequence under tension, so as to establish a wire guide path composed of the upper constraint point, the die hole and the lower constraint point.

[0028] When the die hole axis shifts laterally relative to the wire guide axis, the tension wire segments on both sides of the floating die generate a resultant lateral force toward the wire guide axis.

[0029] When the lateral resultant force is greater than the equivalent rolling resistance generated by the rolling support element, the floating mold is pushed to move in the direction that reduces lateral offset.

[0030] As the lateral offset decreases, the lateral resultant force decreases accordingly until the deviation between the die hole axis and the wire guide axis enters the allowable range determined by the rolling resistance.

[0031] The above method utilizes the geometric deflection of the tension wire segment to generate a restoring effect. The direction of movement of the floating mold is naturally determined by the positional relationship between the wire guide axis and the die hole axis, without the need to execute a preset correction direction control command.

[0032] Optionally, let the distance between the upper and lower constraint points be L, the floating mold be located between the two constraint points, the lateral offset be x, and the tensions of the upper and lower wire segments be T1 and T2 respectively. Then, the resultant lateral force Fh = (T1 + T2)x / √((L / 2)). 2 +x 2 ).

[0033] Under small offset conditions where x is much smaller than L, Fh can be approximated as Kx, where K = 2(T1 + T2) / L. If expressed as the pull-out resistance Fd = T1 - T2, then K = 2(2T1 - Fd) / L. This linear approximation is used to analyze the response of the self-centering device near the centering position, but not for limiting the force relationship under larger offset conditions.

[0034] Optionally, the equivalent rolling resistance Fr = μrN; when Fh is not greater than Fr, the floating mold maintains its current state; when Fh is greater than Fr, the floating mold begins to move in the direction of decreasing offset. The critical offset under small offset conditions is xcrit = μrN / K.

[0035] By establishing a correspondence between tension, constraint point spacing, normal load, and equivalent rolling friction coefficient, the centering sensitivity of the device can be determined according to the wire specifications and drawing tension, and descriptions such as "any non-zero offset will immediately reset" that do not conform to the actual rolling resistance conditions can be avoided. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments are briefly described below. The drawings are used to illustrate the structure and force relationship between the components and do not constitute a limitation on the actual proportions of the components.

[0037] Figure 1 This is a schematic diagram of the overall structure of a tension-assisted self-centering device provided in an embodiment of this application;

[0038] Figure 2 for Figure 1 A magnified view of a portion of point A in the middle;

[0039] Figure 3 This is a schematic diagram showing the relative positions of the upper drive wheel assembly, lower drive wheel assembly, floating mold, and wire.

[0040] Figure 4 for Figure 3 A partially enlarged schematic diagram of the contact structure between the V-groove of the upper drive wheel assembly and the wire at point B;

[0041] Figure 5 for Figure 3 A partially enlarged schematic diagram of the contact structure between the V-groove of the lower drive wheel assembly and the wire at point C;

[0042] Figure 6 for Figure 3 Cross-sectional view of the arrangement structure of the floating mold and rolling support elements at point D;

[0043] Figure 7 for Figure 3 Cross-sectional view of the contact positions between the upper and lower drive wheel sets and the wire in the E1-E2 direction;

[0044] Figure 8 A schematic diagram of the tension force geometry model when a floating mold undergoes lateral displacement.

[0045] Figure 9 This is a schematic diagram showing the dimensional relationship between the rolling support structure and the axial floating clearance.

[0046] Figure 10 This is a schematic diagram showing the relationship between the wire drawing direction, the direction of gravity, and the rolling support state of the floating die.

[0047] Figure 11 This is a flowchart illustrating the tension-assisted self-centering method.

[0048] Explanation of reference numerals in the attached drawings: 1. Lower drive wheel assembly; 2. Mold frame; 3. Upper drive wheel assembly; 4. Rolling support element; 5. Floating mold; 6. Upper support plate; 7. Upper retainer; 8. Pad block; 9. Lower support plate; 10. Lower retainer; 11. Wire; 12. V-groove of the upper drive wheel assembly; 13. Small rounded corner at the bottom of the V-groove of the upper drive wheel assembly; 14. Small rounded corner at the bottom of the V-groove of the lower drive wheel assembly; 15. V-groove of the lower drive wheel assembly; 16. Point of contact between the V-groove of the upper drive wheel assembly and the wire; 17. Point of contact between the V-groove of the lower drive wheel assembly and the wire. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0050] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0051] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0052] Example 1

[0053] During the cold drawing process of metal wire, the deviation between the die hole axis and the actual running axis of the wire will change the load distribution at the die hole entrance. For wires with small diameters, equipment vibration, guide wheel installation errors, and the wire's own fluctuations can all cause slight offsets. If the die is rigidly fixed, the unilateral contact load caused by the offset is difficult to eliminate on its own, easily leading to continuous uneven wear. This embodiment achieves position adjustment by placing the die in a low-resistance lateral floating state and utilizing the lateral resultant force generated by the tensioned wire segment in the offset state.

[0054] See Figure 1 , Figure 4 and Figure 5 The tension-assisted self-centering device provided in this application includes:

[0055] The components include: lower drive wheel assembly 1, mold frame 2, upper drive wheel assembly 3, rolling support element 4, floating mold 5, upper support plate 6, upper retainer 7, pad block 8, lower support plate 9, lower retainer 10, and wire material 11.

[0056] The upper support plate 6 and the lower support plate 9 are mounted on the mold frame 2 and are spaced apart by the pad block 8; the upper retainer 7 and the lower retainer 10 are respectively arranged on the opposite sides of the upper support plate 6 and the lower support plate 9. The floating mold 5 is housed between the upper and lower sets of rolling support elements 4, and its mold hole axis is parallel to the drawing direction of the wire 11.

[0057] The rolling support element 4 is limited by the upper retainer 7 and the lower retainer 10 respectively, and forms rolling contact with the upper or lower end face of the floating mold 5. The upper and lower sets of rolling support elements 4 are used to bear the load of the floating mold 5 along the mold hole axis, and at the same time enable the floating mold 5 to move laterally in the support plane perpendicular to the mold hole axis.

[0058] like Figure 4 As shown, let the distance between the upper support plate 6 and the lower support plate 9 determined by the pad block 8 be H, the thickness of the floating mold 5 along the mold hole axis be h, and the diameter of the rolling support element 4 be D. Then the axial floating clearance δ = Hh - 2D. This clearance is used to prevent the upper and lower rolling support elements 4 from simultaneously rigidly clamping the floating mold 5, and does not represent the lateral movement stroke of the floating mold 5 in the support plane.

[0059] See Figure 2 Both the upper drive wheel assembly 3 and the lower drive wheel assembly 1 have V-grooves on their outer circumferences. The upper and lower V-grooves have the same external dimensions and are aligned axially. The wire 11 passes through the V-groove of the upper drive wheel assembly 3, the die hole of the floating mold 5, and the V-groove of the lower drive wheel assembly 1 in sequence. The tangent points 16 and 17 formed by the upper and lower V-grooves and the wire 11 determine the guide axis of the wire.

[0060] When the die hole axis of the floating die 5 shifts laterally relative to the wire guide axis, the tensioning wire segments on both sides of the floating die 5 tilt accordingly, forming a resultant lateral force towards the wire guide axis within the support plane. When this resultant lateral force exceeds the equivalent rolling resistance generated by the rolling support element 4, the floating die 5 moves in the direction that reduces the shift.

[0061] The upper drive wheel set 3 and the lower drive wheel set 1 are used to pull and tension the wire 11. The bottom of the V-groove is provided with a small rounded corner, so that the wire 11 enters the bottom of the groove in an arc contact manner, reducing the risk of local pressure damage to the wire surface caused by sharp corners. The tangent points 16 and 17 of the upper and lower V-grooves constitute two relatively fixed geometric constraint points, and the floating mold 5 is set between the two constraint points.

[0062] The floating mold 5 is used for reducing the diameter of the wire 11. Its material can be cemented carbide, ceramic, diamond, or polycrystalline diamond. The floating mold 5 is not rigidly locked to the mold frame 2, but moves within the support space defined by the upper and lower rolling support elements 4. An independent lateral limiting gap can also be provided between the outer periphery of the floating mold 5 and the mold frame 2 to limit the maximum lateral movement; the lateral limiting gap is independent of the axial floating gap δ.

[0063] The rolling support element 4 can be a ball, roller, or needle roller. The ball can accommodate multi-directional movement within the support plane, while the roller or needle roller can be arranged according to the main correction direction. The rolling support element 4 is limited by the upper cage 7 and the lower cage 10 respectively. The cage only restricts the rolling support element 4 from leaving the predetermined position and does not require the rolling support elements 4 to rotate synchronously.

[0064] The upper support plate 6 and the lower support plate 9 provide parallel support references. The pad 8 is disposed between the two support plates and the spacing H is defined. The pad 8 can be a precision pad, an annular pad, or several pads of equal thickness. The axial floating clearance δ is adjusted by selecting or grinding the thickness of the pad 8.

[0065] The upper cage 7 and the lower cage 10 can be plate-shaped or ring-shaped structures with receiving holes. The size of the receiving holes is larger than the local displacement required for the rolling support element 4 to roll in the support plane, and smaller than the size of the rolling support element 4 to disengage from the cage, so as to balance rotational freedom and positional limitation.

[0066] The axial floating clearance δ is preferably 0.01 mm to 0.1 mm, more preferably 0.02 mm to 0.05 mm. In a specific assembly, δ is 0.03 mm. After assembly, a small lateral thrust can be applied without threading to confirm that the floating mold 5 can move within the support plane without significant axial clamping.

[0067] See Figure 3 Let L be the distance between the upper and lower constraint points A and B, and let the floating mold 5 be located between A and B. Let x be the lateral offset of the floating mold 5 relative to the line connecting A and B, and let T1 and T2 be the tensions of the upper and lower wire segments, respectively. The resultant lateral force is Fh = (T1 + T2)x / √((L / 2)). 2 +x 2 When x is much smaller than L, Fh is approximately equal to Kx, where K = 2(T1 + T2) / L. Assume the equivalent rolling resistance Fr = μrN. When Fh > Fr, the floating mold 5 begins to move, with a critical offset xcrit = μrN / K.

[0068] The working mechanism of this application is as follows: the upper and lower V-grooves provide a guiding reference for the wire, the rolling support structure provides low-resistance lateral freedom for the floating mold 5, and the tensioned wire segment naturally generates a restoring force in the opposite direction when the mold deviates. This process is achieved by the structure and the force relationship, without the need for sensors to identify the direction of deviation before controlling the actuator.

[0069] After drawing begins, the wire 11 passes through the floating die 5 under the traction of the upper drive wheel set 3 and the lower drive wheel set 1. When the die hole axis is basically aligned with the wire guide axis, the lateral components of the upper and lower wire segments cancel each other out, and the floating die 5 maintains its current position. When the floating die 5 is affected by vibration or assembly errors and undergoes lateral displacement, the tensioned wire segments form a lateral resultant force. After the lateral resultant force overcomes the equivalent rolling resistance, the floating die 5 moves along the support plane until the lateral resultant force is reduced to no greater than the equivalent rolling resistance.

[0070] The following is a set of calculation examples used to illustrate force relationships.

[0071] The wire 11 is made of tungsten wire with a diameter of 0.026 mm and a tensile strength of 6500 MPa. The tension T1 of the upper wire segment is 1.73 N, the drawing resistance Fd is 0.50 N, and the tension T2 of the lower wire segment is T1 - Fd = 1.23 N. The distance L between the upper and lower constraint points is 0.40 m. The effective gravity Geff of the floating mold 5 in the lubricating medium is 0.265 N, and the equivalent rolling friction coefficient μr of the rolling support pair is 0.0003. When not immersed in the lubricating medium, Geff is taken as the actual weight of the floating mold 5 and its follower components.

[0072] Under the condition that the pulling resistance is opposite to the direction of the effective gravity, the normal force N = |Geff - Fd| = 0.235 N; the restoring stiffness under small offset conditions K = 2(T1 + T2) / L = 14.8 N / m; the equivalent rolling resistance Fr = μrN = 0.0000705 N; the critical offset xcrit = Fr / K = 4.76 × 10⁻⁶ -6 m, or 0.00476 mm. This example illustrates the correspondence between parameters; actual values ​​can be determined based on wire specifications, drawing tension, die quality, and rolling support structure.

[0073] Example 2

[0074] In another embodiment, the rolling support element 4 is a ball, roller or needle roller, and is made of a high-hardness wear-resistant material. The equivalent rolling friction coefficient μr between the rolling support element 4 and the floating mold 5 is less than 0.01.

[0075] The sphere forms point contact with the floating mold 5, suitable for minute movements with uncertain direction within the support plane; the roller forms line contact, suitable for applications with larger loads and a primary direction of movement; the needle roller can provide rolling support at a smaller installation height. The axial direction and arrangement of the rolling support elements 4 should be adapted to the expected direction of movement of the floating mold 5.

[0076] High-hardness wear-resistant materials can be hardened bearing steel, cemented carbide, zirconia ceramics, or silicon nitride ceramics. The equivalent rolling friction coefficient μr is used to characterize the resistance formed by the deformation of the rolling element, the cage resistance, and the contact surface condition, and is not equivalent to the sliding friction coefficient of the material surface.

[0077] During the drawing process, the floating die 5 maintains contact with the upper or lower rolling support element 4 under the combined action of gravity and the axial force of the upper and lower wire segments. When the die hole axis shifts laterally, the lateral force acts on the floating die 5; when this lateral force is greater than μrN, the floating die 5 begins to move laterally.

[0078] For example, silicon nitride ceramic balls are used as rolling support elements 4, and the position and rotational clearance of the ceramic balls are controlled by a cage. After assembly, the equivalent rolling friction coefficient is determined by measuring the starting lateral thrust and normal load to ensure that it meets the design critical offset requirements, rather than using the unmeasured reset time as the performance criterion for the device.

[0079] Example 3

[0080] In another embodiment, the rolling support element 4 is a ceramic ball, which is respectively disposed on the upper and lower sides of the floating mold 5 and limited by the upper retainer 7 and the lower retainer 10.

[0081] The ceramic balls can be made of zirconium oxide, alumina, or silicon nitride. The surface of the ceramic balls can be precision ground to reduce the impact of surface roughness on starting resistance. The material, diameter, and precision grade of the ceramic balls can be selected based on the mass of the floating mold 5, contact stress, and working environment.

[0082] Multiple ceramic balls are distributed circumferentially along the floating mold in a support plane perpendicular to the mold hole axis. The circumferential spacing is used to form multi-point support and avoid the normal load being concentrated on a single rolling element; the positions of the upper and lower ceramic balls can correspond to each other, or they can be staggered according to the cage structure.

[0083] The upper cage 7 and the lower cage 10 are each provided with receiving holes corresponding to the ceramic balls. These receiving holes allow the ceramic balls to rotate and undergo limited positional adjustment, while preventing them from dislodging from the support area. The cages can be made of engineering plastics, copper alloys, or surface-hardened steel.

[0084] When the floating mold 5 moves laterally, the ceramic balls on the contact side roll relative to the floating mold 5 and the support plate, while the ceramic balls on the other side are used for axial restraint. The cage does not apply synchronous rotation constraints to the ceramic balls; the actual rotation state of the ceramic balls is determined by the contact load and the direction of movement.

[0085] During assembly, first install the upper and lower ceramic balls into the upper retainer 7 and lower retainer 10 respectively, then install the floating mold 5, pad 8, and upper and lower support plates. Determine δ by measuring H, h, and D, and check whether the movement of the floating mold 5 within the support plane is continuous.

[0086] Example 4

[0087] In one specific embodiment, the rolling support element 4 is made of silicon nitride ceramic balls with a diameter of 2 mm, and 6 silicon nitride ceramic balls are respectively arranged on the upper and lower sides of the floating mold 5.

[0088] Silicon nitride ceramic balls possess high hardness, low density, and good dimensional stability, making them suitable for bearing the normal loads of the floating mold 5. The surface of the ceramic balls undergoes bearing-grade grinding to minimize the impact of surface defects on rolling resistance.

[0089] The 2mm diameter is used to balance installation height and contact load capacity. In actual design, other diameters can be selected based on the Hertzian contact stress check results; the 2mm dimension in this embodiment is a specific structural parameter and does not mean that other dimensions cannot achieve rolling bearings.

[0090] Six ceramic balls are spaced apart on the upper and lower sides within the support plane, and are limited by the upper cage 7 and the lower cage 10 respectively. The number of ceramic balls can be adjusted according to the end face size of the floating mold 5 and the strength of the cages, and the floating mold 5 should still be able to obtain stable multi-point support after adjustment.

[0091] Under axial load, the floating mold 5 maintains rolling contact with one of the ceramic balls, while the other ceramic ball maintains a gap or slight contact with the floating mold 5 formed by the δ distribution. The floating mold 5 does not rely on the simultaneous rigid clamping of the upper and lower ceramic balls.

[0092] In this embodiment, the ceramic ball diameter D is 2mm, and the axial floating clearance δ is 0.03mm. During assembly, the thickness H of the pad 8 is selected according to the thickness h of the floating mold 5, so that H = h + 2D + δ. After assembly, the axial movement and lateral starting thrust of the floating mold 5 are checked.

[0093] Example 5

[0094] In an alternative embodiment, the axial floating clearance δ is 0.01 mm to 0.1 mm.

[0095] The axial floating clearance δ is determined by Hh-2D, where H is the distance between the upper and lower support plates determined by the pad block 8, h is the thickness of the floating mold 5 along the mold hole axis, and D is the diameter of the rolling support element 4. δ represents the axial assembly allowance and does not represent the lateral limiting clearance between the outer periphery of the floating mold 5 and the mold frame 2.

[0096] If δ is too small, the upper and lower rolling support elements 4 may clamp the floating mold 5 simultaneously, increasing the lateral starting resistance; if δ is too large, it may increase the movement of the floating mold 5 along the mold hole axis. By controlling the dimensional tolerances of the pad block 8 thickness, the floating mold 5 thickness, and the diameter of the rolling support element 4, δ can be kept within the design range.

[0097] Example 6

[0098] In another alternative embodiment, the axial floating clearance δ is 0.02 mm to 0.05 mm, and 0.03 mm in a specific assembly.

[0099] The above range applies to ultrafine wire drawing devices that have high requirements for both axial movement and lateral starting resistance. This range is not derived directly from unpublished "best experimental results," but is determined comprehensively based on assembly tolerances, rolling element dimensional errors, lubrication media, and the required amount of axial movement.

[0100] δ is not directly equivalent to the lateral movement of the floating mold 5 within the support plane. The maximum lateral movement can be determined by the lateral limiting clearance between the outer periphery of the floating mold 5 and the mold base 2 or the independent limiting structure, and should be greater than the expected assembly deviation correction amount.

[0101] When δ is 0.03mm, it can be achieved by precisely measuring H, h, and D and selecting pad 8. After assembly, the floating mold 5 should not be clamped in a "zero clearance" manner, but measurable axial movement should be retained or the absence of axial clamping should be confirmed by starting a thrust test.

[0102] During the drawing process, the floating die 5 contacts the rolling support element 4 on one side under the action of normal load. After lateral displacement occurs, the lateral resultant force formed by the tension wire segment drives the floating die 5 to move; the axial floating clearance δ is used to prevent the rolling support element 4 on the other side from forming additional clamping on this movement.

[0103] During assembly, first measure the thickness h of the floating mold 5 and the diameter D of the rolling support element 4, then select the pad 8 according to H=h+2D+δ. After assembly, check the rotation state of the rolling support element 4 in the cage, the axial movement of the floating mold 5, and the starting thrust in the support plane.

[0104] Example 7

[0105] In another optional embodiment, the drawing direction of the wire 11 is parallel to the direction of gravity, and the supporting plane of the floating mold 5 is perpendicular to the direction of gravity; the small rounded corner transition radius at the bottom of the V-groove of the upper and lower drive wheel sets is R0.1mm.

[0106] See Figure 5 In the static installation state, the gravity direction of the floating mold 5 is perpendicular to the support plane. Therefore, gravity does not generate a lateral component force in the support plane, but only provides a normal load to the rolling support element 4. In the drawing state, the tension difference between the upper and lower wire segments can change the normal force between the floating mold 5 and the upper or lower rolling support element 4.

[0107] See Figure 2 The V-grooves of the upper and lower drive wheel sets have the same external dimensions and are aligned along the direction of the filament. The bottom of the V-groove uses a small radius of 0.1mm. This radius is used to form a stable tangent point and reduce local indentation on the surface of the ultrafine filament 11 caused by the sharp groove bottom. For different filament diameters, the radius of the radius can also be adjusted according to the contact stress check.

[0108] During the drawing process, the wire 11 is kept taut between the tangent points 16 and 17 of the upper and lower V-grooves, and the floating die 5 is located between the two tangent points. When the floating die 5 shifts laterally, the upper and lower wire segments tilt relative to the tangent points 16 and 17 and form a restoring effect; after the floating die 5 moves on the rolling support element 4, the deflection angle decreases.

[0109] During assembly, first adjust the axial positions of the upper drive wheel set 3 and the lower drive wheel set 1 so that the line connecting the tangent points 16 and 17 is parallel to the direction of gravity, and then install the mold frame 2 and the floating mold 5. After threading, check the contact position of the wire 11 in the two V-grooves to avoid introducing a fixed lateral force due to misalignment of the grooves or wheel sets.

[0110] Example 8

[0111] See Figure 6 This application also provides a tension-assisted self-centering method for cold drawing dies, which is implemented using the aforementioned tension-assisted self-centering device.

[0112] Step 1: Arrange the floating mold 5 so that the axis of the mold hole is parallel to the drawing direction of the wire 11, and the floating mold 5 can move in a support plane perpendicular to the axis of the mold hole.

[0113] This step involves a low-resistance support structure consisting of an upper support plate 6, a lower support plate 9, a rolling support element 4, and a retaining frame. The initial die hole axis of the floating mold 5 can be substantially coincident with the wire guide axis determined by the upper and lower V-grooves, but the floating mold 5 is not locked in a lateral position by rigid fasteners.

[0114] Step 2: Set the distance H between the upper support plate 6 and the lower support plate 9 using the pad block 8, so that the axial floating clearance δ satisfies δ=Hh-2D.

[0115] The axial floating clearance δ is used to prevent the floating mold 5 from being clamped by the upper and lower rolling support elements 4 at the same time. After setting δ, the floating mold 5 maintains rolling contact with one side of the rolling support element 4 under the action of gravity or the axial resultant force of the upper and lower wire segments, while the other side of the rolling support element 4 provides axial limit.

[0116] Step 3: Under tension, the wire 11 passes sequentially through the V-groove of the upper drive wheel group 3, the die hole of the floating mold 5, and the V-groove of the lower drive wheel group 1 to establish a wire guide path composed of the upper constraint point, the die hole, and the lower constraint point.

[0117] The upper and lower V-grooves are used to limit the lateral coordinates of the wire 11 at two fixed positions, and the floating mold 5 is set between the two constraint points. The so-called "three points in a line" means that in the centering state, the upper constraint point, the center of the mold hole, and the lower constraint point are located on the same wire guide axis, rather than requiring the geometric center of the drive wheel to be directly collinear with the center of the mold hole.

[0118] Step 4: When the die hole axis shifts laterally relative to the wire guide axis, the tension wire segments located on both sides of the floating die 5 form a resultant lateral force toward the wire guide axis.

[0119] Let the distance between the upper and lower constraint points be L, the lateral offset be x, and the tensions of the upper and lower wire segments be T1 and T2, respectively. Then the resultant lateral force Fh = (T1 + T2)x / √((L / 2)). 2 +x 2 When x is much smaller than L, Fh is approximately Kx, where K = 2(T1 + T2) / L. This lateral resultant force is generated by the inclination of the wire segment, and no offset detection sensor is required.

[0120] Step 5: When the lateral resultant force Fh is greater than the equivalent rolling resistance Fr, move the floating mold 5 in the direction of reducing the lateral offset, and maintain the current position when Fh decreases to no greater than Fr.

[0121] The equivalent rolling resistance Fr = μrN, where μr is the equivalent rolling friction coefficient of the rolling support pair, and N is the normal force between the floating mold 5 and the rolling support element 4. This condition indicates that the device has a static dead zone determined by the rolling resistance, and the self-centering process cannot be described as any non-zero offset being immediately and completely eliminated.

[0122] Example 9

[0123] In an alternative method, the drawing direction of the wire 11 is set to be parallel to the direction of gravity, and the support plane of the floating mold 5 is perpendicular to the direction of gravity.

[0124] Step 1: Adjust the installation direction of the upper drive wheel set 3, the lower drive wheel set 1, and the mold frame 2 so that the wire guide axis is parallel to the direction of gravity.

[0125] In this arrangement, the gravity of the floating mold 5 acts along the axis of the mold hole, and does not form a fixed lateral component force within the supporting plane. The wire 11 can be pulled from top to bottom or from bottom to top, and the specific direction does not change the perpendicular relationship between the supporting plane and the direction of gravity.

[0126] Step 2: Utilize the effective gravity of the floating mold 5 and the axial force of the upper and lower wire segments to keep the floating mold 5 in rolling contact with the upper or lower rolling support element 4.

[0127] Let the effective weight of the floating mold 5 be Geff, and the axial pulling resistance formed by the tension difference between the upper and lower wire segments be Fd; in the example working condition where the two are in opposite directions, the normal force N = |Geff - Fd|. When Fd is greater than Geff, the main contact side of the floating mold 5 can be transferred from the lower side to the upper side. Therefore, setting up two sets of upper and lower rolling support elements 4 can adapt to changes in the normal load direction.

[0128] Example 10

[0129] In another alternative method, the conditions for the floating mold 5 to begin self-centering movement are determined based on tension, the spacing between constraint points, and the equivalent rolling resistance.

[0130] Step 1: Determine the distance L between the upper and lower constraint points, the tension T1 of the upper wire segment, the tension T2 of the lower wire segment, the equivalent rolling friction coefficient μr, and the normal force N.

[0131] When the lateral offset of the floating mold 5 is x, the resultant lateral force Fh = (T1 + T2)x / √((L / 2)) 2 +x 2 Under small offset conditions, Fh is approximately Kx, K=2(T1+T2) / L.

[0132] Step 2: Calculate the equivalent rolling resistance Fr=μrN; when Fh>Fr, the floating mold 5 moves in the direction of decreasing offset, and when Fh≤Fr, the floating mold 5 maintains its current position.

[0133] Under small offset conditions, the critical offset xcrit = μrN / K. Taking T1 = 1.73N, T2 = 1.23N, L = 0.40m, μr = 0.0003, and N = 0.235N as an example, K = 14.8N / m, Fr = 0.0000705N, and xcrit = 0.00476mm. This critical value is used to represent the starting dead zone corresponding to rolling resistance, rather than a fixed limit on the alignment accuracy under all operating conditions.

[0134] The above description is an exemplary embodiment of this application and is not intended to limit the scope of protection of this application. Those skilled in the art can make adjustments to the shape, material, size and arrangement of the components without departing from the technical concept of this application; as long as the lateral resultant force generated by the tension wire segment in the offset state is still used to push the low-resistance floating mold to move in the direction of reducing the offset, such adjustments can be considered equivalent embodiments of the technical solution of this application.

Claims

1. A tension-assisted self-centering device for cold drawing dies, characterized in that, include: Upper drive wheel assembly, lower drive wheel assembly, mold frame, floating mold, rolling support element, upper support plate, lower support plate, pad block, upper retainer and lower retainer; The upper support plate and the lower support plate are mounted on the mold frame and are spaced apart by the pads; the upper retainer and the lower retainer are respectively disposed on opposite sides of the upper support plate and the lower support plate, and the rolling support elements are respectively confined within the upper retainer and the lower retainer; The floating mold is housed between the upper and lower rolling support elements, and the floating mold has a die hole for the wire to pass through; let H be the distance between the upper support plate and the lower support plate determined by the pad, let h be the thickness of the floating mold along the die hole axis, and let D be the diameter of the rolling support element, then the axial floating clearance δ satisfies δ=Hh-2D; the floating mold maintains rolling contact with the upper or lower rolling support element and is able to move in a support plane perpendicular to the die hole axis; The outer circumference of both the upper drive wheel assembly and the lower drive wheel assembly is provided with a V-groove, and the bottom of the V-groove is provided with a small rounded corner transition; the wire passes sequentially through the V-groove of the upper drive wheel assembly, the die hole of the floating mold and the V-groove of the lower drive wheel assembly, and the V-groove of the upper drive wheel assembly and the lower drive wheel assembly respectively form an upper constraint point and a lower constraint point, and the die hole is located between the upper constraint point and the lower constraint point; When the die hole axis shifts laterally relative to the wire guide axis determined by the upper constraint point and the lower constraint point, the tension wire segments located on both sides of the floating die form a resultant lateral force toward the wire guide axis in the support plane. When the lateral resultant force is greater than the equivalent rolling resistance generated by the rolling support element, the lateral resultant force pushes the floating mold to move in the direction of reducing the lateral offset until the deviation between the die hole axis and the wire guide axis is reduced to the allowable range.

2. The apparatus according to claim 1, characterized in that, The rolling support element is a ball, roller, or needle roller, and is made of bearing steel, hard alloy, or ceramic material; the equivalent rolling friction coefficient μr between the rolling support element and the floating mold is less than 0.

01.

3. The apparatus according to claim 1, characterized in that, The rolling support element is a ceramic ball, and a plurality of the ceramic balls are distributed at intervals along the circumference of the floating mold in a support plane perpendicular to the axis of the mold hole, and are respectively limited by the upper retainer and the lower retainer.

4. The apparatus according to claim 3, characterized in that, The ceramic ball is a silicon nitride ceramic ball with a diameter of 2mm, and 6 of the silicon nitride ceramic balls are respectively arranged on the upper and lower sides of the floating mold.

5. The apparatus according to claim 1, characterized in that, The axial floating clearance δ is 0.01 mm to 0.1 mm.

6. The apparatus according to claim 5, characterized in that, The axial floating gap δ is 0.02 mm to 0.05 mm; under the condition of drawing ultrafine wire, the axial floating gap δ is 0.03 mm.

7. The apparatus according to claim 1, characterized in that, The drawing direction of the filament is parallel to the direction of gravity, and the supporting plane is perpendicular to the direction of gravity, so that the gravity of the floating mold does not form a lateral component within the supporting plane, and provides a normal load to the rolling support element.

8. The apparatus according to claim 1, characterized in that, The V-grooves of the upper drive wheel assembly and the lower drive wheel assembly have the same external dimensions and are aligned axially. The small rounded corner transition radius at the bottom of the V-groove is R0.1mm. The line connecting the two tangent points formed by the wire at the upper drive wheel assembly and the lower drive wheel assembly is parallel to the direction of gravity.

9. A tension-assisted self-centering method for cold drawing dies, characterized in that, The tension-assisted self-centering device according to any one of claims 1 to 8 includes the following steps: The floating mold is placed between the upper drive wheel set and the lower drive wheel set, and the distance between the upper support plate and the lower support plate is set by the pad block, so that the axial floating clearance δ satisfies δ=Hh-2D. The wire is made to pass through the V-groove of the upper drive wheel set, the die hole of the floating mold, and the V-groove of the lower drive wheel set in sequence under tension, so as to establish a wire guide path composed of the upper constraint point, the die hole and the lower constraint point. When the die hole axis shifts laterally relative to the wire guide axis, the tension wire segments located on both sides of the floating die generate a lateral resultant force toward the wire guide axis. When the lateral resultant force is greater than the equivalent rolling resistance generated by the rolling support element, the floating mold is moved on the rolling support element in a direction that reduces lateral offset until the deviation between the die hole axis and the wire guide axis is reduced to an allowable range.

10. The method according to claim 9, characterized in that, Let L be the distance between the upper and lower constraint points, x be the lateral offset of the floating mold relative to the wire guide axis, and T1 and T2 be the tensions of the upper and lower wire segments of the floating mold, respectively. Then, the resultant lateral force Fh = (T1 + T2)x / √((L / 2)) 2 +x 2 When x is much smaller than L, Fh is approximately Kx, where K = 2(T1 + T2) / L. Let the equivalent rolling resistance of the rolling support element be Fr = μrN, where N is the normal force between the floating mold and the rolling support element; when Fh is greater than Fr, the floating mold starts to move, and the critical offset under small offset conditions is xcrit = μrN / K.

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