Fastener surface high gloss method

Abstract

The application discloses a high-brightness normal line machining process for a fastener surface, relates to the technical field of fastener surface machining, and comprises the following steps: head forming: the rod part and the head part of the fastener are processed through a cold upsetting mode, and a reserved allowance is formed on the head part to form a fastener blank; tooth part forming: the rod part is extruded by a tooth plate to form threads on the surface of the rod part; heat treatment strengthening: the fastener after the tooth part forming is subjected to heat treatment, so that the fastener reaches a set hardness; high-brightness normal line machining: a feeding device is used to convey the fastener after the heat treatment to a numerical control lathe; by the above method, the process route of heat treatment strengthening first and then numerical control turning is adopted, so that the turning machining is performed in the state that the hardness of the fastener base body is improved; the cutting tool cutting can obtain a smooth cutting reflection surface; the surface smoothness of the formed normal line texture is extremely high; the visual appearance presents a mirror-level high-light effect; and the appearance quality and product grade of the fastener are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of fastener surface processing technology, and in particular to a high-gloss normal surface processing technology for fasteners. Background Technology

[0002] In high-end electronic devices, precision instruments, and consumer electronics, fasteners are not only structural connectors, but their appearance quality also becomes an important part of the overall product quality and brand positioning. At the same time, with the development of automated manufacturing and precision assembly technology, the control standards for the surface consistency and dimensional stability of fasteners are becoming increasingly stringent. Traditional processes have inherent limitations in maintaining texture accuracy and surface quality, making it difficult to meet the market's requirements for high-gloss mirror effect and texture clarity on fastener surfaces.

[0003] Existing fastener normal processing uses a pre-heat treatment turning process, which results in damage to the surface finish during high-temperature treatment. The normal lines become blurry, grayish-white, and lack luster, making it difficult to meet the stringent appearance and precision requirements of high-end electronic products. At the same time, traditional normal textures are prone to wear and scratches in actual use due to insufficient hardness, affecting product durability and high-end texture. Therefore, we now offer a high-gloss normal processing technology for fastener surfaces to achieve a mirror-like high-gloss effect on the normal surface, ensuring clear texture, dimensional stability, and improving surface hardness and wear resistance. Summary of the Invention

[0004] The main technical problem solved by this invention is to provide a high-gloss normal surface processing technology for fasteners, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is to provide a high-gloss normal surface processing technology for fasteners, comprising the following steps: Head forming: The shank and head of the fastener are machined by cold heading, and a allowance is reserved in the head to form a fastener blank. The reserved allowance provides complete cutting space for subsequent precision turning and ensures that the normal texture is continuous and uniform. Thread forming: The bar is extruded by a toothed plate to form a thread on the surface of the bar. The extrusion forming by the toothed plate ensures stable thread accuracy and provides a reliable clamping reference for subsequent automated turning. Heat treatment strengthening: The fasteners with completed tooth forming are heat treated to achieve the set hardness. After heat treatment, the hardness of the matrix is ​​increased, giving the machined surface high gloss reflectivity and deformation resistance. High-gloss normal line processing: The heat-treated fastener is transported to the CNC lathe by a feeding device. The CNC lathe turns the head surface to form normal line texture. Turning after heat treatment avoids high-temperature damage. The normal line texture is clear, bright and durable and wear-resistant. Passivation cleaning: Fasteners that have undergone normal machining are subjected to passivation cleaning treatment. Passivation cleaning removes trace residues on the surface, resulting in a pure and uniform normal gloss and improved corrosion resistance.

[0006] Preferably, the head forming step specifically includes: The metal wire is cut to a predetermined length, and the ends of the wire are upheaded by the main die and the punch of the cold heading machine to form the head of the fastener. Upheading makes the metal flow lines continuous and complete, and the head structure is dense and free of internal defects. After the head is formed, the supporting surface and top end face of the head are shaped to make the head centered relative to the rod. After shaping, the head and the rod are coaxially aligned, providing a uniform cutting reference surface for subsequent turning. A thickness allowance of 0.05mm is reserved on the end face of the head, and a diameter allowance of 0.05mm is reserved in the radial direction of the head to form a fastener blank to be processed. The reserved allowance ensures that the surface defects of cold heading are completely removed during turning, and there are no residual defects at the root of the normal texture.

[0007] Preferably, in the head forming step, after the head roughening is completed, the following steps are also included: The ejection mechanism is used to eject the formed fastener blank from the cold heading machine mold cavity and transport it to the chamfering station. The ejection and transportation process is smooth and orderly, the blank is free from bumps and damage, and the surface quality is intact. At the chamfering station, the edges and corners of the head are chamfered to remove the burrs generated during the upsetting process. After chamfering, the edges of the head are smooth and burr-free, avoiding tool breakage during turning. The dimensions of the chamfered fastener blanks are inspected to confirm that the thickness and radial allowance of the head end face are both within the allowance range of 0.05mm. The qualified allowance inspection ensures that each blank has the same cutting conditions and the turning effect is consistent and stable.

[0008] Preferably, the tooth shaping step specifically includes: The fastener blank with the head formed is conveyed between the fixed and movable tooth plates of the thread rolling machine. It is precisely fed between the tooth plates to ensure that the starting position of the thread forming is consistent and the starting end of the thread is neat. The movable tooth plate is driven to reciprocate linearly relative to the fixed tooth plate, so that the rod is subjected to radial compression between the two sets of tooth plates. The radial compression makes the thread surface dense and smooth, and the tooth profile full and tear-free. The thread profile of the die plate is used to extrude a continuous helical thread profile on the surface of the rod, and the extrusion depth is controlled to make the major diameter of the thread reach the predetermined size. The major diameter of the thread is accurate and consistent, and the positioning is reliable when the lathe is clamped without damaging the thread.

[0009] Preferably, the fixed and movable tooth plates of the thread rolling machine are provided with corresponding thread profile structures on their opposing surfaces. The thread profile structures are precisely matched, and the extruded thread root is smooth and stress-free. The movable tooth plate is driven by a crank-connecting rod mechanism and performs reciprocating linear motion in the horizontal direction relative to the fixed tooth plate. The reciprocating motion is smooth and continuous, and there is no vibration or impact during the thread extrusion process, resulting in a smooth tooth surface.

[0010] Preferably, the heat treatment strengthening step specifically includes: Fasteners with completed tooth forming are loaded into the heat treatment furnace in batches, and the furnace temperature is raised to the quenching temperature according to the predetermined heating curve. The heating is carried out according to the curve to ensure that each part is heated evenly and that the internal structure transforms synchronously and consistently. The fasteners are heat-insulated at the quenching temperature to fully austenitize the internal structure of the fasteners. Full austenitization ensures that the structure is uniform after quenching and the overall hardness distribution is uniform. After heat preservation, the fasteners are quickly immersed in the quenching medium for cooling, and then tempered to control the overall hardness of the fasteners between 450HV and 550HV. After quenching and tempering, the matrix is ​​both strong and tough, and the surface reflects a bright luster when turning.

[0011] Preferably, the quenching medium is fast quenching oil, which has a moderate cooling rate, resulting in minimal workpiece deformation and a smooth, oxidation-free surface. Furthermore, the tempering temperature is controlled between 180℃ and 220℃, and the tempering holding time is 90 to 120 minutes. Tempering fully eliminates quenching stress, ensuring stable matrix dimensions and preventing texture chipping after machining.

[0012] Preferably, the high-brightness normal processing step specifically includes: The heat-treated fasteners are placed in a vibratory feeder. The vibration of the vibratory feeder causes the fasteners to be arranged sequentially and enter the feeding track. The vibration sorting ensures that the fasteners are fed out one by one in an orderly manner, and the feeding is continuous and does not jam. The feeding track transports the fastener to the clamping station of the lathe spindle, where the lathe spindle clamps and fixes the rod of the fastener. The rod is firmly clamped and accurately positioned, and the workpiece does not shift or wobble during turning. The pneumatic robotic arm material handling device moves the fastener located at the end of the unloading track into the chuck of the lathe spindle. After the chuck clamps the fastener, the lathe spindle drives the fastener to rotate. The robotic arm moves the fastener quickly and accurately, and after the chuck holds the fastener, the spindle drives the workpiece to rotate smoothly.

[0013] Preferably, in the high-gloss normal machining step, after the fastener is clamped and rotated by the lathe spindle, the process further includes: The lane device drives the cutting tool to move along the X-axis and Z-axis to the starting machining position close to the surface of the fastener head. The X-axis movement of the lane device is driven by the X-axis motor, and the Z-axis movement is driven by the Z-axis motor. The dual-axis linkage enables the cutting tool to be accurately positioned at the machining starting point, and the cutting position of each workpiece is consistent. The X-axis motor drives the lane device to move the cutting tool along the X-axis direction, so that the cutting tool cuts into the head end face to a predetermined depth. The quantitative cutting ensures that the cutting depth is consistent and the root of the normal texture is flat and without undulation. The Z-axis motor drives the lane device to move the cutting tool along the Z-axis direction, causing the cutting tool to continuously cut in the radial direction of the head end face, forming a circular spiral normal texture on the head end face. After the cutting is completed, the X-axis motor drives the lane device to move the cutting tool back along the X-axis direction, forming a uniform spiral texture with continuous radial cutting. The texture is coherent, clear, and has consistent spacing.

[0014] Preferably, the passivation cleaning step specifically includes: The fasteners that have undergone high-gloss normal machining are immersed in an acidic passivation solution for soaking treatment, so that a passivation film is formed on the surface of the fastener. The passivation film completely covers the machined surface, and the normal gloss is uniformly sealed and does not decay. After soaking, the fasteners are removed from the passivation solution and transferred to the cleaning tank. The surface of the fasteners is then rinsed with deionized water. The deionized water rinse thoroughly removes residual acid, leaving the surface clean and free of residual stains. After rinsing, the fasteners are placed in a centrifugal dryer for dehydration and drying, which completes the passivation cleaning of the fastener surface. Centrifugal drying quickly removes water, leaving the normal surface dry, bright, and free of water stains.

[0015] The beneficial effects of this invention are: 1. This invention provides a high-gloss normal surface machining process for fasteners. It adopts a process route of heat treatment for strengthening followed by CNC turning, so that the turning process is carried out in a state of increased hardness of the fastener matrix. The cutting tool can obtain a flat and smooth cutting reflection surface. The surface finish of the formed normal texture is extremely high, and it presents a mirror-level high-gloss effect, which significantly improves the appearance quality and product grade of the fastener.

[0016] 2. This invention provides a high-gloss normal texture processing technology for fastener surfaces. The normal texture is directly formed by turning after heat treatment hardening. The formed textured surface has a high hardness consistent with the fastener substrate, rather than the insufficient surface hardness caused by processing the texture first and then heat treatment in the traditional process. This makes the normal texture have extremely strong scratch resistance and wear resistance in actual use. It can still maintain a clear and sharp texture effect after long-term use, which greatly extends the aesthetic life and durability of the fastener. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the appearance of the equipment for repairing high-gloss normal lines of the vehicle according to the present invention; The components in the attached diagram are labeled as follows: 1. Vibratory feeder; 2. Feeding track; 3. Lathe spindle; 4. Pneumatic robotic arm for material handling; 5. Lane device; 6. X-axis motor; 7. Z-axis motor. Detailed Implementation

[0018] The preferred embodiments of the present invention will now be described in detail so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0019] Example 1 This embodiment provides a high-gloss normal surface processing technology for fasteners, specifically for the mass production of M2.5 specification mobile phone motherboard fasteners, including the following steps: Head Forming: 304 stainless steel wire with a diameter of 2.5mm is cut to a predetermined length. The end of the wire is upset using the main die and punch of a cold heading machine to form a countersunk head structure with an outer diameter of 4.8mm. After forming, the supporting surface and top end face of the head are shaped to center the head relative to the rod. A thickness allowance of 0.05mm is reserved on the end face of the head, and a diameter allowance of 0.05mm is reserved in the radial direction of the head. Then, the blank is ejected by an ejection mechanism and conveyed to the chamfering station to chamfer the edges of the head to remove the flash generated by upsetting. The dimensional inspection confirms that the allowances are all within the 0.05mm reserved range. Thread forming: The blank is conveyed to the fixed and movable tooth plates of the thread rolling machine. The movable tooth plate is driven by the crank connecting rod mechanism and moves in a horizontal reciprocating linear motion relative to the fixed tooth plate, so that the rod is subjected to radial extrusion between the two sets of tooth plates. The thread profile of the tooth plate is used to extrude a continuous helical thread of M2.5×0.45 on the surface of the rod. Heat treatment strengthening: Fasteners with completed tooth forming are batched into a vacuum heat treatment furnace and heated to 1040℃ according to a predetermined heating curve. The temperature is held for 60 minutes to fully austenitize the internal structure. Then, they are quickly immersed in rapid quenching oil for cooling and tempered at 200℃ for 100 minutes to control the overall hardness of the fasteners between 480HV and 520HV. High-gloss normal processing: Refer to Figure 1As shown, the heat-treated fasteners are placed in the vibratory feeder 1, and the vibration causes the fasteners to be arranged sequentially into the unloading track 2. The unloading track transports the fasteners to the clamping position of the lathe spindle 3. The pneumatic manipulator 4 moves the fasteners into the chuck of the lathe spindle 3 and clamps them. The spindle drives the fasteners to rotate at a speed of 3000 r / min. The track device 5, driven by the X-axis motor 6 and the Z-axis motor 7, drives the diamond cutting tool to approach the head end face. The X-axis feeds 0.05 mm into the end face, and the Z-axis feeds 0.02 mm / r continuously along the radial direction, forming a ring-shaped spiral normal texture on the head end face. After the tool passes through, the tool retracts. Passivation cleaning: Immerse the fasteners that have completed the normal machining in a 20% nitric acid passivation solution at room temperature for 10 minutes to form a passivation film; after removal, transfer them to a cleaning tank and rinse them with deionized water for 3 minutes; finally, place them in a centrifugal dryer and dehydrate them at 800 r / min for 5 minutes to complete the processing; The surface roughness Ra of the fastener head normal obtained in this embodiment is ≤0.05μm, exhibiting a mirror-like high-gloss effect. After 100 hours of neutral salt spray testing, the surface showed no rust.

[0020] Example 2 This embodiment provides a high-gloss normal surface machining process for fasteners, specifically for the mass production of M3.0 carbon steel fasteners for laptop hinges, including the following steps: Head Forming: SWCH35K carbon steel wire with a diameter of 3.0mm is cut to a predetermined length. The end of the wire is upset using the main die and punch of a cold heading machine to form a hexagonal flange structure with an outer diameter of 6.0mm. After forming, the supporting surface and top end face of the head are shaped to center the head relative to the rod. A thickness allowance of 0.05mm is reserved on the end face of the head, and a diameter allowance of 0.05mm is reserved in the radial direction of the head. Then, the blank is ejected by an ejection mechanism and transported to the chamfering station to chamfer the edges of the head to remove the flash generated by upseting. The dimensional inspection confirms that the allowances are all within the 0.05mm reserved range. Thread forming: The blank is fed between the fixed and movable tooth plates of the thread rolling machine. The movable tooth plate is driven by the crank connecting rod mechanism and moves in a horizontal reciprocating linear motion relative to the fixed tooth plate, so that the rod is subjected to radial extrusion between the two sets of tooth plates. The thread profile of the tooth plate is used to extrude a continuous helical thread of M3.0×0.5 on the surface of the rod. Heat treatment strengthening: Fasteners with completed tooth forming are loaded into a mesh belt heat treatment furnace in batches and heated to 880℃ according to the predetermined heating curve. The temperature is held for 45 minutes to fully austenitize the internal structure. Then, they are quickly immersed in rapid quenching oil for cooling and tempered at 210℃ for 90 minutes to control the overall hardness of the fasteners between 500HV and 550HV. High-gloss normal line machining: The heat-treated fasteners are placed in the vibratory plate 1, and the vibration causes the fasteners to be arranged sequentially into the unloading track 2; the unloading track transports the fasteners to the clamping position of the lathe spindle 3, and the pneumatic manipulator 4 moves the fasteners into the chuck of the lathe spindle 3 for clamping, and the spindle drives the fasteners to rotate at a speed of 2500 r / min; the track device 5, driven by the X-axis motor 6 and the Z-axis motor 7, drives the cubic boron nitride cutting tool close to the head end face, the X-axis feed is 0.05 mm into the end face, and the Z-axis feed is 0.025 mm / r to continuously feed radially, forming a ring-shaped spiral normal line texture on the head end face, and the tool is retracted after the feed is completed; Passivation cleaning: Immerse the fasteners that have completed the normal machining in a 15% citric acid passivation solution at 50°C for 8 minutes to form a passivation film; after removal, transfer them to a cleaning tank and rinse them with deionized water for 5 minutes; finally, place them in a centrifugal dryer and dehydrate them at 1000 r / min for 3 minutes to complete the processing; The fastener head obtained in this embodiment has clear and uniform normal texture and spacing. After 500 friction and wear tests, there are no obvious wear marks on the normal texture and the surface gloss retention rate is ≥95%.

[0021] Example 3 This embodiment provides a high-gloss normal surface machining process for fasteners, specifically for the mass production of M1.6 micro fasteners for smartwatches, including the following steps: Head Forming: 316L stainless steel wire with a diameter of 1.6mm is cut to a predetermined length. The end of the wire is upset using the main die and punch of a cold heading machine to form a flat head structure with an outer diameter of 3.2mm. After forming, the supporting surface and top end face of the head are shaped to center the head relative to the rod. A thickness allowance of 0.05mm is reserved on the end face of the head, and a diameter allowance of 0.05mm is reserved in the radial direction of the head. Then, the blank is ejected by an ejection mechanism and conveyed to the chamfering station to chamfer the edges of the head to remove the flash generated by upseting. The dimensional inspection confirms that the allowances are all within the 0.05mm reserved range. Thread forming: The blank is conveyed to the fixed and movable tooth plates of the thread rolling machine. The movable tooth plate is driven by the crank connecting rod mechanism and moves in a horizontal reciprocating linear motion relative to the fixed tooth plate, so that the rod is subjected to radial extrusion between the two sets of tooth plates. The thread profile of the tooth plate is used to extrude a continuous helical thread of M1.6×0.35 on the surface of the rod. Heat treatment strengthening: Fasteners with completed tooth forming are batched into a vacuum heat treatment furnace and heated to 1060℃ according to a predetermined heating curve. The temperature is held for 40 minutes to fully austenitize the internal structure. Then, they are quickly immersed in rapid quenching oil for cooling and tempered at 190℃ for 120 minutes to control the overall hardness of the fasteners between 450HV and 490HV. High-gloss normal line machining: The heat-treated fasteners are placed in the vibratory plate 1, and the vibration causes the fasteners to be arranged sequentially into the unloading track 2; the unloading track transports the fasteners to the clamping position of the lathe spindle 3, and the pneumatic manipulator 4 moves the fasteners into the chuck of the lathe spindle 3 for clamping, and the spindle drives the fasteners to rotate at a speed of 4000 r / min; the track device 5, driven by the X-axis motor 6 and the Z-axis motor 7, drives the polycrystalline diamond cutting tool close to the head end face, and the X-axis feeds 0.05 mm into the end face, and the Z-axis feeds continuously radially at a feed rate of 0.015 mm / r, forming a ring-shaped spiral normal line texture on the head end face, and the tool is retracted after the feed is completed; Passivation cleaning: Immerse the fasteners that have completed the normal machining in a 25% nitric acid passivation solution at room temperature for 8 minutes to form a passivation film; after removal, transfer them to a cleaning tank and rinse them with deionized water for 4 minutes; finally, place them in a centrifugal dryer and dehydrate them at 1200 r / min for 2 minutes to complete the processing; The surface roughness Ra of the head normal of the miniature fastener obtained in this embodiment is ≤0.04μm. Under a 50x optical microscope, the normal texture is clear and sharp with no burrs, and the yield rate reaches 98.5%, which meets the strict quality requirements of smartwatch appearance parts.

[0022] Comparative Example 1 The difference between this comparative example and Example 1 is that this comparative example does not adopt the high-gloss normal line processing sequence of "heat treatment first, then CNC turning". Instead, it adopts the traditional process method, that is, after the head forming and tooth forming are completed, the head end face of the fastener is first turned to form normal line texture, and then the fastener is heat treated to strengthen it. Specifically, in the high-gloss normal line machining step of this comparative example, the head end face of the cold-headed fastener blank (hardness approximately HV150~HV200) is directly machined using a CNC lathe to form normal line texture; after the normal line machining is completed, the fastener is placed in a heat treatment furnace for quenching and tempering treatment to achieve an overall hardness of 450HV~550HV; finally, passivation cleaning is performed. Since the normal texture is processed before heat treatment, the surface of the normal will undergo oxidation, decarburization and thermal deformation during the subsequent high-temperature heating and rapid cooling process. This causes the originally clear texture obtained by turning to become blurred, the surface to turn grayish-white and lose its luster. At the same time, the oxide scale generated by heat treatment adheres to the micro-grooves of the normal texture and is difficult to completely remove through subsequent passivation and cleaning. As a result, the surface of the normal of the final product cannot present a mirror-like high-gloss effect and appears grayish-white.

[0023] Comparative Example 2 The difference between this comparative example and Example 1 is that this comparative example does not use a CNC lathe to precisely machine the end face of the fastener head to form a normal texture, but instead uses a milling process. Specifically, in this comparative example, after heat treatment strengthening, fasteners with a hardness of 450HV to 550HV were clamped on a CNC milling machine, and the head end face was milled using a milling cutter to form a normal texture. During the milling process, the milling cutter is a multi-edged rotary tool, and each cutting edge generates periodic impacts and vibrations when cutting into and out of the workpiece surface, resulting in tiny serrated chipping and burrs on the edge of the normal texture. At the same time, the feed motion trajectory of the milling process is a straight line or circular interpolation, which cannot achieve single-edged continuous helical cutting. The normal texture produced is inferior to that of turning in terms of texture continuity and surface finish. The roughness Ra of the normal texture of the obtained product is greater than 0.2μm, the surface gloss is obviously insufficient, and there are micro-defects at the texture edge, which cannot meet the quality requirements of high-end electronic products for mirror high gloss.

[0024] Comparative Example 3 The difference between this comparative example and Example 1 is that this comparative example does not reserve a thickness allowance of 0.05mm and a radial allowance in the head forming step, but instead adopts a cold heading process to directly form the head to the final size. Specifically, in this comparative example, the head end face thickness and outer diameter are directly machined to the final dimensions required by the finished product during the cold heading head forming process, without leaving any cutting allowance. After the tooth forming and heat treatment strengthening are completed, in the high-gloss normal line machining step, the CNC lathe tool needs to cut the head end face to form normal line texture. However, since there is no allowance for the head end face thickness, the tool cannot form a complete continuous cutting path when cutting in, and the cutting depth is limited and unstable, resulting in uneven normal line texture depth and some areas that cannot be completely cut and covered. Surface defects left by the original cold heading forming (such as slight folds, pits, etc.) remain on the surface of the final product. The resulting product had uneven normal texture and discontinuous patterns, with a yield of only 72%, far lower than the yield level of Example 1.

[0025] Comparative Example 4 The difference between this comparative example and Example 1 is that in the heat treatment strengthening step, the overall hardness of the fastener is controlled between 350HV and 400HV, which does not reach the hardness range of 450HV to 550HV. Specifically, in this comparative example, the tempering temperature was raised to 320℃ and the tempering holding time was 120 minutes, reducing the overall hardness of the fastener to 350HV~400HV. Under this hardness condition, when performing high-gloss normal texture machining, due to the insufficient hardness of the fastener head end face, the CNC lathe tool could not obtain a good cutting reflection surface during the cutting process. The surface after cutting showed slight plastic deformation and extrusion cracks, rather than the ideal mirror-reflective surface formed by brittle cutting. At the same time, the lower hardness of the normal texture significantly reduced its scratch resistance in actual use. After 100 friction tests, obvious scratches and wear appeared on the normal surface, which could not meet the requirements of high-end electronic products for the wear resistance of the normal texture. The surface gloss of the resulting product was only 60% of that of Example 1. After 200 hours of salt spray testing, corrosion spots appeared on the edges of the normal texture. The product's durability and appearance quality did not meet the standards.

[0026] The fasteners prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were subjected to performance tests. The test items and test methods are as follows: The surface roughness (Ra) test method is as follows: a white light interferometric profilometer (such as Zygo NewView9000) is used to perform non-contact measurement on the normal surface of the fastener head. For each sample, three different positions (central area, middle ring, and outer edge area) on the normal surface are measured, and the arithmetic mean is taken as the final Ra value in μm. Before measurement, the sample surface is ultrasonically cleaned with anhydrous ethanol for 5 minutes to remove oil and impurities. The surface gloss (GU) test is conducted as follows: A micro gloss meter (such as BYK micro-TRI-gloss, measuring angle 60°) is used to measure the gloss of the normal surface of the fastener head. Five evenly distributed points are taken on the normal surface of each sample for measurement, and the arithmetic mean is taken as the final gloss value in GU. Before measurement, ensure that the sample surface is clean and dry, and calibrate the instrument with a standard black glass plate. The test method for the clarity of normal texture (visual rating) is as follows: Under a standard light source color matching box (D65 light source, 1000 lux), the sample is placed on a white background board and visually observed by 5 trained testers at a distance of 30cm. The clarity, continuity, and brightness of the normal texture are comprehensively rated. The rating standards are: Grade A - clear and sharp texture, bright as a mirror, without any blurring; Grade B - relatively clear texture, slightly glossy but not bright enough; Grade C - blurry texture, grayish or whitish, without gloss. The majority of the 5 ratings is used as the final rating. The wear resistance performance (gloss retention rate after friction) test is conducted using a linear reciprocating friction tester (such as Taber 5750), with a CS-10 standard grinding wheel as the friction head, a load of 500g, a friction stroke of 25mm, a reciprocating frequency of 60 times / min, and a total of 500 friction cycles. After the friction test, the gloss value of the sample friction area is measured again according to the test item (surface gloss (GU)), and the gloss retention rate is calculated: retention rate (%) = (gloss value after friction / initial gloss value) × 100%. The average value of three measurements is taken for each sample.

[0027] The specific fastener performance test results are shown in Table 1 below.

[0028] Table 1. Comparison of performance test results of fasteners prepared in each embodiment and the comparative example. Based on the above test results, the following conclusions can be drawn: As can be seen from the test data of Examples 1 to 3, the high-gloss normal line processing technology for fasteners provided by the present invention has excellent and stable processing effect. The surface roughness Ra value of the three examples is ≤0.052μm, the surface gloss is ≥856GU, the normal line texture clarity reaches Grade A, and the gloss retention rate of wear resistance is ≥93.8%. Among them, Example 3 (M1.6 smartwatch micro fastener) achieved the best surface quality (Ra=0.039μm, gloss=923GU, retention rate=96.1%) due to the higher rotation speed (4000r / min), smaller feed rate (0.015mm / r) and the use of polycrystalline diamond tools. This shows that the process of the present invention has more prominent advantages in the processing of micro precision fasteners. The above data shows that the core technical solution of heat treatment followed by CNC turning can stably achieve a mirror high-gloss effect, while giving the normal line texture excellent hardness and wear resistance.

[0029] Comparative Example 1 adopted the traditional "turning first, then heat treatment" process sequence. Its surface roughness deteriorated sharply to Ra=0.386μm, gloss was only 215GU, normal texture clarity dropped to C grade, and wear resistance retention rate was only 68.2%. All indicators were significantly worse than the three examples. This fully demonstrates that heat treatment has a serious destructive effect on unprotected turned surfaces, confirming the keyness and necessity of the "heat treatment hardening first, then CNC turning" process route of the present invention.

[0030] Comparative Example 2 uses milling instead of turning for normal machining. Although its process sequence is the same as that of the present invention (cutting after heat treatment), its surface roughness (Ra=0.235μm) and gloss (378GU) are still far inferior to the three embodiments due to the multi-blade rotary cutting characteristics of milling. This shows that in high-gloss normal machining, the single-blade continuous spiral feed method of CNC turning has irreplaceable advantages and is a key technical means to achieve mirror high-gloss effect.

[0031] Comparative Example 3 did not leave a machining allowance of 0.05mm, and its normal texture clarity was only grade B. Its gloss (412GU) and roughness (Ra=0.218μm) were significantly worse than the three examples. This shows that the 0.05mm allowance provided the necessary cutting space for subsequent turning, which could effectively remove the surface defect layer generated by cold heading and ensure the integrity and uniformity of the normal texture.

[0032] The hardness of Comparative Example 4 was controlled at 350HV to 400HV (lower than the 450HV to 550HV required by this invention). Its gloss (538GU) and wear resistance retention rate (72.3%) were significantly insufficient. In particular, the wear resistance was only 76.5% of that of Example 1. This shows that the hardness of the fastener matrix is ​​an important factor in determining the optical effect and wear life of the normal surface after turning. Insufficient hardness not only affects the formation quality of the cutting reflection surface, but also directly reduces the scratch resistance of the normal texture in actual use.

[0033] In summary, the complete technical solution of this invention, which involves "heat treatment to harden to 450HV~550HV, leaving a 0.05mm allowance, CNC turning after heat treatment, and automatic unloading with a vibratory feeder and robotic arm feeding," has significantly better performance indicators than the comparative examples. It can stably achieve a mirror-like high-gloss effect on the normal surface of the fastener head, while giving the normal texture excellent wear resistance and dimensional stability, fully meeting the requirements of high-end electronic products for the appearance quality and durability of fasteners.

[0034] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A high-gloss normal surface machining process for fasteners, characterized in that, Includes the following steps: Head forming: The shank and head of the fastener are processed by cold heading, and a allowance is reserved in the head to form a fastener blank; Thread forming: The rod is pressed by a toothed plate to form threads on the surface of the rod. Heat treatment strengthening: Heat treatment is performed on the fasteners after the tooth part has been formed so that the fasteners reach the set hardness. High-gloss normal line machining: The heat-treated fastener is fed to a CNC lathe by a feeding device, and the CNC lathe turns the head surface to form a normal line texture. Passivation cleaning: Passivation cleaning is performed on fasteners that have undergone normal machining.

2. The high-gloss normal surface machining process for fasteners according to claim 1, characterized in that, The head forming step specifically includes: The metal wire is cut to a predetermined length, and the ends of the wire are upheaded by the main die and punch of the cold heading machine to form the head of the fastener. After the head is formed, the supporting surface and top end face of the head are shaped to center the head relative to the rod. A thickness allowance of 0.05 mm is reserved on the end face of the head, and a diameter allowance of 0.05 mm is reserved in the radial direction of the head to form a fastener blank to be processed.

3. The high-gloss normal surface machining process for fasteners according to claim 2, characterized in that, The head forming step, after the head roughening is completed, also includes: An ejection mechanism is used to eject the formed fastener blank from the cold heading machine mold cavity and transport it to the chamfering station; At the chamfering station, the edges and corners of the head are chamfered to remove the burrs generated during the upsetting process; The dimensions of the chamfered fastener blank are inspected to confirm that the thickness and radial allowance of the head end face are both within the allowance range of 0.05mm.

4. The high-gloss normal surface machining process for fasteners according to claim 1, characterized in that, The tooth shaping steps specifically include: The fastener blank with the head formed is conveyed between the fixed and movable jaw plates of the thread rolling machine; The movable jaw plate is driven to reciprocate linearly relative to the fixed jaw plate, so that the rod is subjected to radial compression between the two sets of jaw plates; The thread profile of the die plate is used to extrude a continuous helical thread profile onto the surface of the rod, and the extrusion depth is controlled to make the major diameter of the thread reach the predetermined size.

5. The high-gloss normal surface machining process for fasteners according to claim 4, characterized in that, The fixed and movable jaw plates of the thread rolling machine are provided with corresponding thread profile structures on their opposing surfaces; The movable jaw plate is driven by a crank-connecting rod mechanism and performs reciprocating linear motion in the horizontal direction relative to the fixed jaw plate.

6. The high-gloss normal surface machining process for fasteners according to claim 1, characterized in that, The heat treatment strengthening step specifically includes: The fasteners with the teeth formed are loaded into the heat treatment furnace in batches, and the furnace temperature is raised to the quenching temperature according to the predetermined heating curve. The fasteners are heat-insulated at the quenching temperature to ensure that the internal structure of the fasteners is fully austenitized. After heat preservation, the fasteners are quickly immersed in quenching medium for cooling, and then tempered to control the overall hardness of the fasteners between 450HV and 550HV.

7. The high-gloss normal surface machining process for fasteners according to claim 6, characterized in that, The quenching medium is selected as rapid quenching oil; Furthermore, the tempering temperature is controlled between 180°C and 220°C, and the tempering holding time is 90 to 120 minutes.

8. The high-gloss normal surface machining process for fasteners according to claim 1, characterized in that, The high-gloss normal processing steps specifically include: The heat-treated fasteners are placed in the vibrating plate (1), and the vibration of the vibrating plate (1) causes the fasteners to be arranged sequentially and enter the feeding track (2). The feeding track (2) transports the fastener to the clamping position of the lathe spindle (3), and the lathe spindle (3) clamps and fixes the rod of the fastener. The pneumatic manipulator (4) moves the fastener located at the end of the unloading track (2) into the chuck of the lathe spindle (3). After the chuck is clamped, the fastener is rotated by the lathe spindle (3).

9. The high-gloss normal surface machining process for fasteners according to claim 8, characterized in that, In the high-gloss normal machining step, after the fastener is clamped and rotated by the lathe spindle (3), the process also includes: The lane device (5) drives the cutting tool to move along the X-axis and Z-axis to the starting machining position close to the surface of the fastener head. The X-axis movement of the lane device (5) is driven by the X-axis motor (6), and the Z-axis movement is driven by the Z-axis motor (7). The X-axis motor (6) drives the lane device (5) to move the cutting tool along the X-axis direction, so that the cutting tool cuts into the head end face to a predetermined depth. The Z-axis motor (7) drives the lane device (5) to move the cutting tool along the Z-axis direction, so that the cutting tool continuously cuts along the radial direction of the head end face, forming a circular spiral normal texture on the head end face. After the cutting is completed, the X-axis motor (6) drives the lane device (5) to move the cutting tool back along the X-axis direction.

10. The high-gloss normal surface machining process for fasteners according to claim 1, characterized in that, The passivation cleaning step specifically includes: The fasteners that have undergone high-gloss normal processing are immersed in an acidic passivation solution for soaking treatment, so that a passivation film is formed on the surface of the fasteners. Remove the soaked fasteners from the passivation solution and transfer them to a cleaning tank. Rinse the surface of the fasteners with deionized water. After rinsing, the fasteners are placed in a centrifugal dryer for dehydration and drying to complete the passivation cleaning of the fastener surface.

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