Grinding and polishing method for small-aperture polycrystalline wire-drawing die

Abstract

The invention discloses a grinding and polishing method for a small-aperture polycrystalline wire-drawing die, which belongs to the technical field of metal processing die repair and comprises the following steps: fixing the small-aperture polycrystalline wire-drawing die to be repaired on a die seat; a diamond wire penetrates through the die hole; grinding liquid is dropwise added to the wire inlet position of the diamond wire; the diamond wire is used for driving the die base to rotate at a high speed and move up and down in a reciprocating mode, the diamond wire drives abrasive materials to grind and polish the inner wall of a die hole, the problems of agglomeration and uneven distribution of abrasive particles during repairing of the small-aperture die are solved, the diamond wire is used for replacing a common high-carbon steel wire to serve as a grinding wire, and the repairing effect of the small-aperture die is improved.

Description

Technical Field

[0001] This invention belongs to the field of metal processing mold repair technology, specifically a grinding and polishing method for small-diameter polycrystalline wire drawing molds. Background Technology

[0002] Polycrystalline die-casting molds, with their high hardness, high wear resistance, low coefficient of friction, and strong impact resistance, are widely used in the processing of ultra-fine wire diameters from various metals and alloys such as steel, copper, tungsten, and molybdenum. However, in practical applications, polycrystalline die-casting molds can still wear down under high-intensity use and become unusable. To extend the service life of the molds, companies often replace worn molds with those from the previous pass by grinding and repairing them, thus reducing production mold costs.

[0003] "Grinding wire + polishing fluid" is a common method for repairing polycrystalline molds. The grinding wire is usually high-strength steel wire, and the functional component of the polishing fluid is mainly diamond micron powder. The mold is fixed on the mold base, the grinding wire passes through the mold hole, and the polishing fluid is dripped into the inlet of the grinding wire. A motor drives the mold base to rotate at high speed via a belt, and a high-speed cylinder pushes the mold base to move up and down at high speed. The high-precision grinding and polishing of the inner surface of the polycrystalline mold is achieved by the squeezing and cutting action generated by the rolling of abrasive particles driven by the wire.

[0004] The methods described above are effective for repairing large-diameter molds, but perform poorly in repairing small-diameter molds. This is because the ultrafine abrasive wire used in repairing small-diameter molds has too low rigidity, making it prone to bending and vibration within the hole, resulting in uneven polishing pressure and ellipticity. Furthermore, diamond abrasive grains tend to agglomerate within the micropores due to surface tension, making it difficult for them to enter the channel evenly with the polishing fluid, leading to uneven polishing. Additionally, the large hole depth of small-diameter molds results in insufficient abrasive grain concentration in the center of the hole, severely impacting repair efficiency. Therefore, avoiding abrasive grain agglomeration and uneven distribution is crucial for improving the repair quality of small-diameter molds. Summary of the Invention

[0005] To address the above problems, this invention provides a grinding and polishing method for small-aperture polycrystalline wire drawing dies, which solves the problems of abrasive grain agglomeration and uneven distribution during die repair. This invention uses diamond wire instead of ordinary high-carbon steel wire as the grinding wire, thereby improving the repair effect of small-aperture dies.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for grinding and polishing a small-aperture polycrystalline wire drawing die includes the following steps: (1) Fix the small-diameter polycrystalline wire drawing die to be repaired onto the die holder; (2) Pass the diamond wire through the die hole; (3) Add polishing fluid to the inlet of the diamond wire; (4) Drive the mold base to rotate at high speed and move up and down repeatedly, and use diamond wire to drive the abrasive to grind and polish the inner wall of the mold hole.

[0007] In the above technical solution, after the mold is fixed, diamond wires with extremely high rigidity and abrasive particles attached to their surface pass through the mold hole, serving as the main force transmission and grinding medium. The grinding fluid (containing free diamond micropowder) added at the wire inlet is effectively carried deep into the mold hole by the high-speed moving and rough-surfaced diamond wires. The mold base rotates at high speed under the drive of a motor, and at the same time, it is pushed up and down by a cylinder, which makes the diamond wires form a complex composite motion trajectory within the mold hole. The solidified abrasive particles on its surface directly cut and compress the mold wall, while driving the free abrasive particles to roll, achieving high-precision and uniform grinding and polishing of the inner surface of the polycrystalline mold.

[0008] In a preferred embodiment, the diamond wire is made by electroplating synthetic diamond microparticles onto a metal wire, which may be a high-carbon steel wire or a tungsten wire. The electroplating process involves depositing a metal coating (typically nickel or a nickel-cobalt alloy) onto the metal wire substrate (high-carbon steel or tungsten wire). During this process, the synthetic diamond microparticles are uniformly embedded and fixed within the metal coating. This forms a robust composite structure with uniformly distributed abrasive particles. During operation, these firmly held diamond microparticles act as fixed micro-cutting edges, directly participating in the removal of material from the inner wall of the polycrystalline mold.

[0009] In a preferred embodiment, the diamond wire diameter is 0.05mm-0.10mm. This technical solution selects a diamond wire of this specific diameter to create an optimal gap between it and the micro-drill holes. A gap that is too small (wire diameter too large) will increase frictional resistance and prevent the polishing slurry from effectively entering; a gap that is too large (wire diameter too small) will reduce the wire's rigidity and cause vibration. The selected wire diameter, within this optimized range, can stably transmit the polishing force from rotational and reciprocating motion, while also forming a fluid channel to carry the polishing slurry into the hole using capillary action and wire movement.

[0010] In a preferred embodiment, the average particle size of the diamond microparticles on the surface of the diamond wire is 1μm-10μm. In this technical solution, the size of the diamond microparticles on the electroplated wire directly determines the cutting depth of a single abrasive grain and the depth of the wear mark left behind. Within this particle size range, the abrasive grains can effectively perform micro-cutting on the polycrystalline diamond material. During the repair process, a series of wires, progressing from coarse to fine (e.g., gradually changing from 10μm to 1μm), are typically used for multiple polishing operations to gradually reduce surface roughness and ultimately achieve a mirror-like polishing effect.

[0011] In a preferred embodiment, the density of diamond particles on the surface of the diamond wire is 200-800 particles / mm². During the electroplating preparation of the diamond wire, precise control of the number of abrasive particles bonded per unit area can be achieved by controlling the suspension concentration of the micropowder and the electroplating parameters. At this density, there is sufficient spacing between the abrasive particles to accommodate chips and allow the polishing fluid to flow, while also forming a continuous and uniform polishing surface. This avoids "missed polishing" caused by the absence of abrasive particles in certain areas, thereby achieving comprehensive and consistent material removal from the inner wall of the mold.

[0012] In a preferred embodiment, the polishing slurry is a suspension containing diamond microparticles with a mass concentration of 5%-20%. At this concentration, the polishing slurry exhibits good dispersibility and stability, and the diamond microparticles are not prone to rapid sedimentation or agglomeration. When the polishing slurry is dripped onto the inlet of a high-speed moving diamond wire, the liquid with suitable viscosity can effectively adhere to the wire surface and be carried into the die cavity. The movement of the wire generates shear force on the polishing slurry, which helps to disperse the abrasive particles and ensure that they participate uniformly in the polishing process throughout the entire cavity.

[0013] In a preferred embodiment, the rotational speed of the mold holder is 1000-3000 rpm. The high-speed rotation of the mold holder drives the wire drawing die on it to rotate as well, resulting in extremely high relative velocity between the diamond wire passing through the die hole and the inner wall of the die hole. This velocity is directly converted into the cutting speed of the abrasive grains against the inner wall of the mold. The appropriate rotational speed ensures that the abrasive grains can effectively cut polycrystalline materials, while the centrifugal force generated by the rotation also helps to discharge the polishing fluid and abrasive debris, keeping the polishing interface clean.

[0014] In a preferred embodiment, the reciprocating motion frequency of the mold base is 5-20Hz.

[0015] In a preferred embodiment, the method is applicable to polycrystalline wire drawing dies with an aperture no greater than 0.1 mm. When the die aperture is less than or equal to 0.1 mm, the problems of insufficient rigidity and difficulty in abrasive delivery in traditional steel wire grinding wires become extremely prominent, leading to repair failure. This invention overcomes the technical obstacles in small spaces by using diamond wire with superior rigidity and both abrasive delivery and cutting functions, along with optimized process parameters, making efficient and high-quality repair of dies below this critical size possible.

[0016] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention is the first to apply diamond wire to the repair of small-diameter polycrystalline wire drawing dies, which fundamentally solves the problems of easy bending and uneven polishing pressure and ellipticity caused by insufficient rigidity of traditional flexible steel wire in micropores; at the same time, the diamond wire itself is bound with diamond abrasive grains and can effectively carry free abrasives, which significantly improves the conveying efficiency of polishing fluid in micropores and the uniformity of abrasive distribution, thereby greatly improving the repair accuracy, surface finish and overall repair efficiency of small-diameter dies; This invention clarifies the specific structure and material of the diamond wire. The high-carbon steel wire or tungsten wire matrix provides excellent tensile strength and rigidity, ensuring that the wire remains stable and does not bend when moving in the micro-hole. The diamond micro powder is solidified by electroplating, which has strong bonding force and excellent wear resistance, ensuring that it can continuously provide effective grinding during the repair process, extending the service life of the grinding wire itself and avoiding frequent replacement of the wire. This invention explicitly limits the application of this method to small-sized polycrystalline wire drawing dies with an aperture of no more than 0.1 mm, highlighting the technical contribution of this invention to addressing the most difficult problem to solve in the prior art: repairing "small aperture" dies. Furthermore, it clarifies the advantageous application areas of this method, clearly distinguishing it from traditional methods for large aperture dies, and emphasizing its creativity and uniqueness. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below with reference to embodiments. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way. Example

[0018] A method for grinding and polishing a small-aperture polycrystalline wire drawing die includes the following steps: (1) Securely fix a worn-out polycrystalline diamond wire drawing die with a hole diameter of 0.06 mm onto the die holder; (2) Select an electroplated diamond wire with a diameter of 0.05 mm as the grinding wire. The metal wire matrix is ​​high carbon steel wire, the average particle size of the diamond particles on the surface is 5 μm, and the particle density is about 400 particles / mm². Pass the diamond wire smoothly through the die hole. (3) A diamond micro powder suspension with a mass concentration of 10% was continuously added at the inlet of the diamond wire as a polishing slurry; (4) Start the equipment, set the rotation speed of the mold base to 2000 rpm, the frequency of the up-and-down reciprocating motion to 10 Hz, and the processing time to 45 min to complete the grinding and polishing of the mold. Example

[0019] A method for grinding and polishing a small-aperture polycrystalline wire drawing die includes the following steps: (1) Securely fix a worn-out polycrystalline diamond wire drawing die with a hole diameter of 0.08 mm onto the die holder; (2) Select an electroplated diamond wire with a diameter of 0.06 mm as the grinding wire. The metal wire matrix is ​​high carbon steel wire, the average particle size of the diamond particles on the surface is 8 μm, and the particle density is about 600 particles / mm². Pass the diamond wire smoothly through the die hole. (3) A diamond micro powder suspension with a mass concentration of 15% was continuously added at the inlet of the diamond wire as a polishing slurry; (4) Start the equipment, set the rotation speed of the mold base to 2500 rpm, the frequency of the up-and-down reciprocating motion to 15 Hz, and the processing time to 35 min to complete the grinding and polishing of the mold. Example

[0020] A method for grinding and polishing a small-aperture polycrystalline wire drawing die includes the following steps: (1) Securely fix a worn-out polycrystalline diamond wire drawing die with a hole diameter of 0.10 mm onto the die holder; (2) Select an electroplated diamond wire with a diameter of 0.07 mm as the grinding wire. The metal wire matrix is ​​high carbon steel wire, the average particle size of the diamond particles on the surface is 10 μm, and the particle density is about 300 particles / mm². Pass the diamond wire smoothly through the die hole. (3) A diamond micro powder suspension with a mass concentration of 8% was continuously added at the inlet of the diamond wire as a polishing slurry; (4) Start the equipment, set the rotation speed of the mold base to 1500 rpm, the frequency of the up-and-down reciprocating motion to 8 Hz, and the processing time to 60 min to complete the grinding and polishing of the mold. Example

[0021] A method for grinding and polishing a small-aperture polycrystalline wire drawing die includes the following steps: (1) Securely fix a worn-out polycrystalline diamond wire drawing die with a hole diameter of 0.06 mm onto the die holder; (2) First step rough polishing: Select electroplated diamond wire with a diameter of 0.05mm as the polishing wire. The metal wire matrix is ​​high carbon steel wire, the average particle size of the diamond particles on the surface is 8μm, and the particle density is about 400 particles / mm². Pass the diamond wire smoothly through the die hole. Continuously add diamond micro powder suspension with a mass concentration of 10% as polishing fluid at the inlet of the diamond wire. Start the equipment, set the rotation speed of the die seat to 2000rpm, the frequency of the up and down reciprocating motion to 10Hz, and the processing time to 30min.

[0022] (3) Second step of fine polishing: Replace with electroplated diamond wire with the same wire diameter (0.05mm) but with an average particle size of 2μm and a particle density of about 600 particles / mm². At the same time, replace the polishing fluid with a diamond micro powder suspension with a mass concentration of 10% and an average particle size of 2μm. Keep other process parameters unchanged and continue processing for 15 minutes to complete the final grinding and polishing of the mold.

[0023] Comparative Example 1: This comparative example uses the same wear mold (0.06 mm aperture) as Example 1; the mold fixing method is the same, but in step (2), ordinary high carbon steel wire with the same wire diameter (0.05 mm) is selected as the grinding wire; the diamond polishing fluid with the same concentration of 10% as Example 1 is used, and other process parameters are also the same.

[0024] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the diamond wire used has an average particle size of 20 μm for the surface diamond microparticles, while other parameters are the same as in Example 1.

[0025] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that no polishing fluid is added in step (3), and dry polishing is carried out solely by the bonded abrasive grains of the diamond wire itself. The rest of the contents are the same as in Example 1.

[0026] The repair effects of the small-aperture polycrystalline wire drawing dies repaired in Examples 1-3 and Comparative Examples 1-3 were tested, and the ellipticity was measured using a high-precision electronic roundness meter. The instrument's measurement accuracy reached 0.1 μm. A surface roughness measuring instrument was used, with a sufficiently small radius of the probe (stylus) to accommodate the measurement of the surface roughness (Ra) of the micropore inner wall. The test results are shown in the table below.

[0027]

[0028] It should be noted that, in this document, the terms "comprising," "including," and any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be pointed out that, due to the limitations of written expression and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the concept and technical solution of the present invention to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A method for grinding and polishing a small-aperture polycrystalline wire drawing die, characterized in that, Includes the following steps: (1) Fix the small-diameter polycrystalline wire drawing die to be repaired onto the die holder; (2) Pass the diamond wire through the die hole; (3) Add polishing fluid to the inlet of the diamond wire; (4) Drive the mold base to rotate at high speed and move up and down repeatedly, and use diamond wire to drive the abrasive to grind and polish the inner wall of the mold hole.

2. The method according to claim 1, characterized in that, The diamond wire is made by electroplating synthetic diamond micropowder onto a metal wire, which is either high-carbon steel wire or tungsten wire.

3. The method according to claim 1, characterized in that, The diameter of the diamond wire is 0.05mm-0.10mm.

4. The method according to claim 2, characterized in that, The average particle size of the diamond microparticles on the surface of the diamond wire is 1μm-10μm.

5. The method according to claim 2, characterized in that, The density of diamond particles on the surface of the diamond wire is 200-800 particles / mm².

6. The method according to claim 1, characterized in that, The grinding fluid is a suspension containing diamond micron powder, with a mass concentration of 5%-20%.

7. The method according to claim 1, characterized in that, The rotation speed of the mold base is 1000-3000 rpm.

8. The method according to claim 1, characterized in that, The reciprocating motion frequency of the mold base is 5-20Hz.

9. The method according to claim 1, characterized in that, The method is applicable to polycrystalline wire drawing dies with an aperture of no more than 0.1 mm.

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