Automatic recycling device for rivet production waste

Abstract

The application discloses a rivet production waste automatic recycling device and relates to the technical field of solid waste recycling and disposal. The device comprises a vibration pre-sorting mechanism, parallel independent long material flow branches and fine chip flow branches and a central PLC control system. The pre-sorting mechanism is provided with an anti-bridge and anti-arch device and an adjustable grid, and waste materials are separated into long material flow and fine chip flow according to length. The long material flow branches are sequentially connected with a long material cleaning unit, an air knife blowing assembly, an induction heating softening unit and a cold heading recycling feeding unit, so that the same grade recycling of blank cutting surplus materials and short rod surplus materials is realized. The fine chip flow branches are sequentially connected with a centrifugal oil removal unit, an ultrasonic cleaning unit, a magnetic separation and impurity removal unit and a hydraulic briquetting unit, so that fine chips are pressed into high-density cake blocks as smelting raw materials. An oil liquid filtering unit connected with the centrifugal oil removal unit realizes closed-loop recycling of cutting oil. Through source sorting and differential processing of the double branches, the device avoids the degradation and waste of high-quality nail head materials.

Description

Technical Field

[0001] This invention relates to the field of solid waste recycling and disposal technology, specifically to an automatic recycling and reuse device for rivet production waste. Background Technology

[0002] In rivet production (especially the cold heading process for semi-hollow rivets and blind rivets), the billet cutting step generates approximately 8%–15% of the input material as "rivet head waste" (i.e., billet cutting residue). Simultaneously, the thread rolling and machining sections produce a large amount of oily shavings. Currently, industry practices mainly fall into two categories: 1. Full external sales: Rivet heads and shavings are mixed and sold as scrap steel, resulting in low unit prices, but the oil content necessitates hazardous waste disposal, leading to high costs. 2. General-purpose metal scrap briquetting line: This uses a "lifting → crushing → degreasing → briquetting" process, treating all waste materials equally. This route has the following drawbacks: The billet cutting residue, which could have been directly reheated for cold heading without crushing (saving 18%–25% energy), is instead crushed and briquetized, causing high-quality material to be downgraded to remelted material, resulting in an economic value loss of approximately 30%. The phosphating / galvanizing layer mixes with the oily shavings, making it difficult to reduce the overall oil content of the batch to an ideal level, leading to severe smoke generation during smelting. Short rivet rods easily "bridge" in the hopper, and general-purpose production lines lack specific anti-bridging devices. Patent CN105772485A discloses a hardware recycling device that uses hammer crushing and acid washing, but the acid washing process does not meet the environmental requirements for rivet steel and does not differentiate between long and thin materials. Furthermore, there are rivet head recycling devices for automatic riveting machines that only collect rivet heads without reusing them. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned defects and provide an automatic recycling device and method for rivet production waste. Its core innovation lies in the pre-sorting by length before crushing, and establishing differentiated processing channels for two different types of waste: long material flow (blank cutting residue and short rod residue) follows a same-level recycling channel of "cleaning → air knife blowing → induction heating softening → recooling and upsetting station," while fine chip flow (fine chips shorter than the grid gap) follows a downgraded recycling channel of "degreasing → cleaning → magnetic separation → briquetting." The two branches run parallel and independently, without interference, simultaneously achieving closed-loop recovery of cutting oil.

[0004] To solve the above problems, the technical solution provided by the present invention is as follows:

[0005] An automatic recycling and reuse device for rivet production waste includes a pre-sorting mechanism, a waste processing mechanism, and a central PLC control system.

[0006] The pre-sorting mechanism is a vibrating pre-sorting mechanism. Its feed hopper outlet is equipped with an anti-bridging and arch-breaking device, and its screen surface is equipped with an adjustable grid, which is used to separate rivet production waste into long material streams and fine chip streams according to length.

[0007] The waste treatment mechanism includes parallel and independently arranged long material flow branches and fine debris flow branches;

[0008] The long material flow branch is connected in sequence along the material direction to a long material cleaning unit, an air knife blowing assembly, an induction heating softening unit, and a cold heading reusable feeding unit, which are used to transport the billet cutting residue and short rod residue to the cold heading station for reuse after cleaning, drying, and softening.

[0009] The fine debris flow branch is connected in sequence along the material direction to a centrifugal degreasing unit, an ultrasonic cleaning unit, a magnetic separation and impurity removal unit, and a hydraulic pressing unit, which are used to press the fine debris into cakes after degreasing, cleaning and impurity removal.

[0010] The oil outlet of the centrifugal degreasing unit is connected to an oil filtration unit, and the oil outlet of the oil filtration unit is used to connect to the riveting machine's processing oil circuit to achieve closed-loop recovery of cutting oil.

[0011] The central PLC control system is connected to the actuators of the vibration pre-sorting mechanism, the long material flow branch, and the fine debris flow branch, respectively, and is used to control the coordinated automatic operation of the two branches.

[0012] The concept of "source sorting + dual-branch parallel processing" has been introduced into the field of rivet waste recycling. A vibration pre-sorting mechanism separates waste into two categories based on length, solving the problem of high-quality material degradation caused by mixing billet cutting residue with fine chips. An anti-bridging and arch-breaking device specifically addresses the arching jamming phenomenon of short rivet rods at the hopper outlet, ensuring continuous feeding. The long material flow branch is designed with a short process of "washing → drying → softening → direct reuse" for billet cutting residue and short rod residue, achieving same-level reuse and avoiding crushing energy consumption and material degradation losses. The fine chip flow branch is designed with a long process of "de-oiling → deep cleaning → impurity removal → briquetting" for oily fine chips, thoroughly purifying them into high-density briquettes, enhancing the value of smelting and reuse. The centrifugal de-oiling unit connected to the oil filtration unit achieves closed-loop recycling of cutting oil, transforming oily wastewater, originally treated as hazardous waste, into a reusable resource, reducing environmental protection costs and cutting oil procurement costs. The central PLC control system integrates the signal acquisition and control of all actuators, achieving fully automated, minimally manned operation and improving production efficiency and stability. Overall, this claim defines the core innovation of the device at the system level—the dual-branch differentiated processing architecture—providing a complete hardware foundation for solving the high-value recycling of rivet waste.

[0013] Optionally, the grid gap of the vibrating pre-sorting mechanism is infinitely adjustable within the range of 15mm to 40mm, and the screen surface inclination angle is adjustable within the range of 5° to 15°, suitable for sorting waste materials of M3 to M12 specification rivets; the anti-bridging and arch-breaking device includes a pair of anti-bridging toothed rollers rotating in opposite directions, and the adjustable grid includes parallel fixed grid bars and movable grid bars, side guide grooves, a gap adjustment assembly containing an adjusting screw and a linkage rod, a scale and a locking nut. By rotating the adjusting screw to drive the linkage rod, the movable grid bars can be moved synchronously along the guide groove, which can realize the infinitely adjustable grid gap and position locking.

[0014] This design enables the pre-sorting mechanism to adapt to a wide range of specifications. The stepless adjustment range of the grid gap (15-40mm) covers the length span of the entire M3-M12 rivet series—M3 rivets are approximately 6-10mm long, and M12 rivets are approximately 24-36mm long. An upper limit of 40mm ensures that all blank cutting residue is included in the long material flow, while a lower limit of 15mm accommodates the smallest specifications. The screen inclination angle is adjustable (5°-15°), allowing operators to adjust the material's residence time on the screen surface based on its moisture content and oil content. A larger inclination angle increases throughput and capacity, while a smaller inclination angle improves sorting accuracy, achieving a dynamic balance between throughput and accuracy. The anti-bridging and arch-breaking device uses a pair of counter-rotating arch-breaking toothed rollers with a tooth pitch of 20-35mm, matching the length of the rivet short rods. Through mechanical forced agitation, the arched structure is broken, completely solving the problem of frequent bridging at the hopper outlet that causes downtime and improving feeding reliability. These parameters together ensure that the pre-sorting mechanism can operate stably and efficiently under different specifications and working conditions, providing reliable sorting quality for subsequent dual-branch processing.

[0015] Optionally, the long material cleaning unit is equipped with a rotating brush roller and a high-pressure fan-shaped nozzle, the high-pressure fan-shaped nozzle having a spray pressure of 0.8 to 1.2 MPa; the long material cleaning unit uses an alkaline degreasing agent aqueous solution as the cleaning fluid, and the operating temperature is 50 to 65°C; the air knife blowing assembly is located at the discharge end of the long material cleaning unit and is used to blow away the residual cleaning fluid film on the surface of the long material.

[0016] This system achieves efficient removal of contaminants from the nail head surface, while providing a clean and dry surface for subsequent induction heating. A rotating brush roller mechanically peels away loose oxide scale, oil, and phosphate residue from the nail head surface through friction. The brush roller material (stainless steel wire) has moderate hardness and does not damage the substrate. A high-pressure fan-shaped nozzle (0.8–1.2 MPa) sprays an alkaline degreasing agent, utilizing a chemical saponification reaction to convert animal, vegetable, and mineral oils into soluble fatty acid salts. Simultaneously, high-pressure impact assists in the removal of stubborn deposits. The operating temperature setting of 50–65℃ balances degreasing agent activity and energy consumption—below 50℃, the saponification reaction rate is slow; above 65℃, water evaporation is rapid, increasing the risk of alkali crystallization. An air knife blowing assembly is located at the discharge end, using a high-speed airflow (25–35 m / s) to completely blow away the liquid film remaining on the nail head surface after cleaning. This prevents residual alkaline cleaning solution from causing alkali concentration and corrosion of the nail head surface during subsequent induction heating due to rapid water evaporation, and also avoids the liquid film affecting the uniformity of induction heating. The combination of these three processes (brushing → spraying → blowing) achieves the dual goals of "cleanliness + dryness" on the nail head surface, laying a foundation for surface quality for subsequent induction heating softening and cold heading reuse.

[0017] Optionally, the induction heating softening unit uses a medium-frequency induction coil with a working frequency of 2-8kHz to heat the surface of the nail head and short rod residue in the long material flow to 650-750℃ and hold it for 15-30s, so that the surface work-hardened layer is partially annealed while the core retains the original metallographic structure; the cold heading recycle feeding unit is used to feed the softened material into the cold heading mold cavity according to the working rhythm of the cold heading machine.

[0018] By employing a precisely controlled induction heating process, the brittleness of the work-hardened layer is eliminated without altering the overall mechanical properties of the rivet head, restoring sufficient plasticity to withstand further cold heading deformation. During the cold heading process of rivets, the blank material undergoes severe plastic deformation after cutting, resulting in significant work hardening on the surface (hardness reaching HV280–350). Direct re-cold heading would lead to cracking or excessive die wear. Medium-frequency induction heating (2–8 kHz) utilizes the skin effect to concentrate heat at a depth of 0.5–1.5 mm on the surface, heating it to 650–750°C (below the A1 line of steel, approximately 727°C). This causes recovery and recrystallization in the work-hardened zone, reducing the hardness to HV180–220, while the core retains its original cold-drawn fibrous structure and strength. Holding at this temperature for 15–30 seconds ensures uniform heat penetration and avoids localized overheating. This differentiated heat treatment method, which softens the surface while preserving the core, restores the plasticity required for cold heading and retains the tensile strength of the core, enabling a cold heading qualification rate of over 98% for recycled nail heads. The cold heading recycling feeding unit feeds materials synchronously at the original cold heading machine's cycle time (60-200 pieces / min), achieving seamless connection between the softened material and the cold heading machine, avoiding intermediate buffering and secondary handling.

[0019] Optionally, a visual inspection station is provided between the induction heating softening unit and the cold heading recycling feeding unit. The visual inspection station is used to identify and reject long materials that are deformed or out of size. The outlet of the unqualified material at the visual inspection station is connected to the fine chip flow branch through a bypass pipeline.

[0020] To prevent substandard nail heads caused by improper pre-processing (such as incomplete cleaning or uneven heating) or original defects (such as bent billets or damaged heads) from entering the cold heading process, thus ensuring the pass rate of cold heading products and the life of the mold. The visual inspection station uses a CCD industrial camera with image processing algorithms to detect the outline of each nail head in real time. The judgment indicators include bending degree (>0.5mm), head defects (>10% area), and length deviation. Once a defective product is detected, a pneumatic push rod or flipping mechanism is immediately triggered to remove it, preventing defective material from mixing with the qualified material flow. More importantly, the rejected defective material is not discarded, but is automatically introduced into the fine chip flow branch through a bypass pipeline. After mixing with the fine chips, it enters the degreasing → cleaning → magnetic separation → briquetting process, realizing the "zero waste" recycling of materials. This design reflects the closed-loop thinking of the system: the quality control boundary of the long material flow branch extends to the fine chip flow branch. The two branches are not only parallel in space, but also complementary in the material flow direction through the bypass.

[0021] Optionally, the centrifugal deoiling unit is a horizontal screw discharge centrifuge with a working speed of 800-1200 rpm; the oil filtration unit is a two-stage filtration unit, including a primary filter screen and a precision filter screen connected in sequence, and the oil extracted by centrifugation is returned to the riveting machine processing oil circuit after secondary filtration.

[0022] This system efficiently separates cutting oil from fine chips and purifies it to reusable standards, achieving closed-loop cutting oil recycling. The horizontal screw discharge centrifuge generates 300-600G centrifugal force at 800-1200rpm, effectively throwing off free oil adhering to the surface of the chips (initial oil content 8%-15%), reducing the oil content of the discharged chips to ≤2%. This degreasing efficiency far surpasses gravity settling or pressure filtration. The screw pusher simultaneously conveys and compresses, further improving the degreasing effect. The extracted oil contains fine metal particles and impurities and cannot be directly reused; therefore, a two-stage filtration unit is installed: a primary filter (80 mesh) intercepts larger particles (>0.18mm), and a precision filter (200 mesh) removes even finer suspended matter (>0.075mm). The cutting oil after two stages of filtration meets the standards for use in riveting machine processing oil circuits and is pumped back to the machine tool for recycling. This design transforms oily debris, which would otherwise need to be disposed of as hazardous waste, into recyclable oil resources, saving a significant amount of cutting oil procurement costs and hazardous waste disposal expenses each year, resulting in substantial economic and environmental benefits.

[0023] Optionally, the magnetic separation and impurity removal unit adopts a permanent magnet drum with a surface magnetic induction intensity ≥3000Gs; the discharge end of the magnetic separation and impurity removal unit is connected to an air classifier to remove non-metallic light impurities with a specific gravity of less than 1.5g / cm³ from the fine debris.

[0024] Ferromagnetic impurities and non-metallic light impurities are removed one by one from the fine chips to ensure that the purity of the chips before briquetting meets the smelter's purchasing requirements. The magnetic induction intensity of the permanent magnet drum surface is ≥3000Gs, which can effectively capture cemented carbide tool particles (WC-Co, which are weakly magnetic due to the cobalt content), worn iron filings, and other ferromagnetic foreign objects mixed in with the fine chips. The magnetic separation efficiency can reach over 99%. After magnetic separation, the fine chips may still contain non-metallic light impurities such as plastic labels, rubber gaskets, and fibers. These impurities will burn and produce harmful gases or form slag inclusions during smelting. The air classifier uses the rising airflow (1.5~3m / s) to separate based on density differences: metal chips with a density >5g / cm³ fall and are collected; non-metallic light impurities with a density <1.5g / cm³ are carried away by the airflow. The two-stage impurity removal process (magnetic separation + air separation) forms a comprehensive purification chain from "ferromagnetic impurities to non-ferromagnetic light impurities," which significantly improves the purity of the final briquettes. This makes it easier for smelters to directly feed the briquettes into the furnace and also increases the sales premium of the briquettes.

[0025] Optionally, the hydraulic pressing unit is a four-column hydraulic press with a nominal pressure adjustable from 200 to 630 t, and the density of the pressed cake is ≥6.2 g / cm³, with a single cake weighing 3 to 8 kg.

[0026] Loose, oily, and mixed fine shavings are transformed into dense, clean, and homogeneous standardized briquettes, facilitating transportation, storage, and smelting reuse. The four-column hydraulic press boasts high structural rigidity and guiding precision, with an adjustable nominal pressure of 200–630t, adaptable to different production line scales and briquette requirements for various materials (steel, aluminum, stainless steel). Under high pressure, the fine shavings undergo plastic deformation and cold welding, filling the gaps between particles and reducing the volume to 1 / 5–1 / 8 of its original size. The briquette density reaches ≥6.2g / cm³ (equivalent to over 80% of the density of solid steel). This density is significantly higher than ordinary briquettes (typically 5.5–6.0g / cm³), meeting the threshold for premium purchase by smelters (usually requiring ≥6.0g / cm³), with a premium of 15%–30%. The design, with a single briquette weight of 3–8kg, balances the convenience of manual handling and mechanical stacking, and also facilitates batching and metering in the smelting furnace. The adjustable pressure function allows the equipment to flexibly handle fine chips of different materials (such as aluminum chips, which require lower pressure to avoid excessive cold welding), thus expanding the applicability of the device.

[0027] An automated method for recycling and reusing rivet production waste includes the following steps:

[0028] S1. The waste material discharged from the rivet production line is sent to the vibrating pre-sorting mechanism. First, the material arch is broken by the arch-breaking structure to avoid jamming. Then, the material is sorted into long material flow and fine chip flow according to the length of the material by the grid screen.

[0029] S2. After being cleaned, dried by air knife blowing, and softened by induction heating in sequence, the long material flow is conveyed to the cold heading station for direct reuse.

[0030] S3. After being subjected to centrifugal degreasing, ultrasonic cleaning, and magnetic separation for impurity removal, the fine chip stream is hydraulically pressed into cakes for use as recycled material in smelting.

[0031] S4. The cutting oil obtained by centrifugal degreasing in step S3 is filtered and then returned to the riveting machine's processing oil circuit to achieve closed-loop reuse.

[0032] Steps S2 and S3 are executed in parallel and independently, respectively using processing parameters that match the characteristics of long and fine materials.

[0033] The various unit operations of the aforementioned device are organically linked into a complete process, emphasizing the core concept of "parallel and independent operation." Step S1 solves the problems of feed blockage and material diversion through arch breaking and grid sorting, serving as the starting point and quality foundation of the entire process. Step S2 is designed as a short process for long material flows: "cleaning and decontamination → drying → local annealing → direct reuse," maximizing the preservation of the geometric shape and material value of the billet cutting residue and avoiding crushing energy consumption and degradation losses. Step S3 is designed as a long process for fine chip flows: "de-oiling → deep cleaning → impurity removal → densification," thoroughly purifying fine chips through multi-stage physicochemical treatment, ultimately producing high-value-added cakes. Step S4 filters the cutting oil separated by centrifugal de-oiling and immediately reuses it, forming a closed-loop oil circulation. The parallel and independent execution of steps S2 and S3 means that the two branches operate synchronously in time without waiting for each other, fully utilizing equipment capacity and improving overall processing efficiency. This method breaks away from the traditional "one-size-fits-all" recycling approach, enabling precise grading and processing of waste materials in different forms. It is a process mapping of hardware innovation in the device.

[0034] Optionally, in step S2, after the long material flow is softened by induction heating and before entering the cold heading station, unqualified materials with excessive deformation or out-of-tolerance dimensions are removed by visual inspection. The unqualified materials are transferred to the fine chip flow for processing in step S3. The reuse quality of the long material flow accounts for 40% to 60% of the total rivet waste, and the comprehensive utilization rate of waste is ≥92%.

[0035] To ensure the quality stability of recycled materials, the system provides economic and environmental performance benchmarks for the entire system. Visual inspection, acting as a quality control link in the long material flow branch, removes deformed or dimensionally out-of-tolerance nail heads and automatically transfers them to the fine debris flow branch. This prevents inferior materials from entering the cold heading process, which could lead to scrap or mold damage, ensuring a cold heading pass rate of at least 98% for recycled nail heads. A long material flow recycling rate of 40%–60% is an optimized economic range: too low a rate (<40%) means a large number of nail heads are treated as fine debris, wasting the potential value of the same level of recycling; too high a rate (>60%) may affect the cold heading pass rate due to inconsistent nail head quality. A comprehensive utilization rate of ≥92% is an important technical indicator, meaning that less than 8% of the waste (mainly non-recyclable non-metallic light impurities, incineration losses, and trace dust) is ultimately discarded, far exceeding the approximately 85% of the traditional full crushing and briquetting route. This indicator reflects the advanced nature of the device in resource recovery and is also a key data support for measuring the superiority of the dual-branch architecture.

[0036] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0037] Dual-branch differentiated processing architecture: For the first time in the field of rivet waste recycling, a strategy of diverting processing according to material form is proposed, avoiding the downgrading and waste of rivet head material in general full crushing and briquetting lines.

[0038] Adjustable grid pre-sorting + anti-bridging and arch breaking: grid gap is infinitely adjustable from 15 to 40 mm, suitable for all sizes from M3 to M12; the arch breaking toothed roller is specially designed to solve the problem of short rod bridging.

[0039] Customized induction heating softening parameters: For the cold work hardening characteristics of rivet steel (ML10~ML40Cr series), annealing parameters of 650~750℃ / 15~30s are set to soften only the surface layer without changing the core structure, ensuring the pass rate of direct cold heading.

[0040] Visual inspection + bypass rejection: Visual inspection is added at the end of the long material flow branch to automatically guide unqualified items into the fine debris flow branch, ensuring the quality of reuse.

[0041] Oil closed-loop: The extracted cutting oil is reused after secondary filtration, reducing cutting oil consumption by 15% to 30%. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the overall structure of the device;

[0043] Figure 2 This is a flowchart of the overall process flow of the device;

[0044] Figure 3 Block diagram of the central PLC control system;

[0045] Figure 4 This is a schematic diagram of an adjustable grid structure;

[0046] 100. Vibration pre-sorting mechanism; 110. Anti-bridging and arch-breaking device; 120. Feed hopper; 200. Adjustable grid; 210. Movable grid bar; 220. Guide chute; 230. Linkage rod; 240. Fixed grid bar; 250. Adjusting screw; 260. Scale; 270. Locking nut; 300. Fine debris flow branch; 400. Long material flow branch. Detailed Implementation

[0047] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments.

[0048] Example 1

[0049] Combined with appendix Figure 1-4 An automatic recycling and reuse device for rivet production waste includes a pre-sorting mechanism, a waste treatment mechanism, and a central PLC control system.

[0050] The pre-sorting mechanism is a vibrating pre-sorting mechanism 100. Its feed hopper 120 is equipped with an anti-bridging and arch-breaking device 110 at the outlet. Its screen surface is equipped with an adjustable grid 200, which is used to separate rivet production waste into long material flow and fine chip flow according to length. The material in the long material flow is short blank scrap and short rod scrap. The recycled material is cylindrical short blank, which can be directly fed into the cold heading mold cavity for secondary forming.

[0051] The waste handling mechanism includes a parallel and independently configured long material flow branch 400 and a fine debris flow branch 300;

[0052] The long material flow branch 400 is connected in sequence along the material direction to the long material cleaning unit, the air knife blowing assembly, the induction heating softening unit and the cold heading reusable feeding unit, which is used to transport the billet cutting residue and short rod residue to the cold heading station for reuse after cleaning, drying and softening.

[0053] The fine debris flow branch 300 is connected in sequence along the material direction to a centrifugal degreasing unit, an ultrasonic cleaning unit, a magnetic separation and impurity removal unit, and a hydraulic pressing unit, which are used to press the fine debris into cakes after degreasing, cleaning and impurity removal.

[0054] The oil outlet of the centrifugal degreasing unit is connected to an oil filtration unit. The oil outlet of the oil filtration unit is used to connect to the riveting machine's oil circuit to achieve closed-loop recovery of cutting oil.

[0055] The central PLC control system is connected to the actuators of the vibration pre-sorting mechanism 100, the long material flow branch 400, and the fine chip flow branch 300, respectively, to control the coordinated automatic operation of the two branches.

[0056] Rivet production waste first enters the vibratory pre-sorting mechanism 100. An anti-bridging and arch-breaking device 110 prevents short rods from getting stuck at the hopper outlet. An adjustable grid 200 divides the waste into long material streams (blank cutting residue and short rod residue) and fine chip streams based on material length. The long material stream enters the first branch, where it undergoes sequential cleaning to remove surface oil, air knife blowing and drying, induction heating to soften and restore plasticity, and finally is fed back to the cold heading machine for direct reuse via the feeding unit. The fine chip stream enters the second branch, where it first undergoes centrifugal degreasing to separate most of the cutting oil (the oil is purified by the oil filtration unit and reused), then ultrasonic cleaning for deep decontamination, magnetic separation to remove ferromagnetic impurities, and finally hydraulic pressing into high-density cakes for use as smelting raw materials. The central PLC control system collects sensor signals from each unit and coordinates parameters such as start / stop, speed, temperature, and pressure of the two branches to achieve fully automatic unattended operation.

[0057] The grid gap of the vibrating pre-sorting mechanism 100 is infinitely adjustable within the range of 15mm to 40mm, and the screen surface inclination angle is adjustable within the range of 5° to 15°, which is suitable for sorting waste materials of M3 to M12 specification rivets; the anti-bridging and arch-breaking device 110 includes a pair of anti-bridging toothed rollers rotating in opposite directions, and the tooth pitch of the anti-bridging toothed rollers is 20 to 35mm.

[0058] Combined with appendix Figure 4 The adjustable grid 200 includes multiple parallel grid bars, side guide grooves 220, gap adjustment components, and scale indicators; the multiple grid bars are arranged at equal intervals along the width of the screen surface, of which at least one is a fixed grid bar 240 and the rest are movable grid bars 210; the two ends of the fixed grid bar 240 are fastened to the inner side wall of the screen box, and the two ends of the movable grid bars 210 are embedded in the guide grooves 220 on both sides of the inner wall of the screen box, and can slide horizontally along the width of the screen surface.

[0059] The gap adjustment assembly includes an adjusting screw 250 and a linkage rod 230. The adjusting screw 250 passes through the side wall of the screen box along the width direction of the screen surface, and its inner end is synchronously hinged to all the movable grid bars 210 through the linkage rod 230. When the adjusting screw 250 is rotated, the linkage rod 230 drives all the movable grid bars 210 to move synchronously along the guide groove 220, so that the gap between all the grid bars increases or decreases synchronously, realizing stepless adjustment within the range of 15mm to 40mm.

[0060] A scale 260 is provided on the outer wall of the screen box corresponding to the adjusting screw 250. The range of the scale 260 corresponds to the grid gap adjustment range and is used to intuitively display the current grid gap value. A locking nut 270 is provided on the adjusting screw 250. After the gap is adjusted to the correct position, tightening the locking nut 270 will lock the grid bar position and prevent the gap from shifting under vibration conditions.

[0061] The synchronous adjustment structure ensures that the grid gaps across the entire screen surface are uniform and consistent, avoiding a decrease in sorting accuracy caused by the offset of a single grid bar; the cooperation between the guide slide 220 and the locking nut 270 can withstand the high-frequency excitation of the vibrating screen, and there is no loosening or misalignment during long-term operation, which is suitable for the rapid sorting and switching needs of the entire series of rivet waste from M3 to M12.

[0062] The stepless adjustment of the grid gap (15–40 mm) allows operators to adjust the gap size according to the specifications of the rivets currently being produced. When the gap is smaller than the rivet head length, the rivet head and short rod remain on the screen surface as a long material flow; when the gap is larger than the size of the fine debris, the fine debris passes through the screen and falls. The screen surface inclination angle (5°–15°) affects the residence time of the material on the screen surface and the sorting efficiency. The larger the angle, the faster the material passes through, but the sorting accuracy may decrease. The arch-breaking toothed roller rotates in the opposite direction, and the tooth tips insert between the accumulated short rods, forcibly breaking the arch structure and allowing the material to fall smoothly onto the screen surface, avoiding manual material handling.

[0063] The long material cleaning unit is equipped with a rotating brush roller and a high-pressure fan-shaped nozzle. The spray pressure of the high-pressure fan-shaped nozzle is 0.8 to 1.2 MPa. The long material cleaning unit uses an alkaline degreasing agent aqueous solution as the cleaning fluid, and the working temperature is 50 to 65℃. The air knife blowing assembly is located at the discharge end of the long material cleaning unit and is used to blow away the residual cleaning fluid film on the surface of the long material.

[0064] A rotating brush roller mechanically removes loose deposits from the nail head surface through friction. A high-pressure fan-shaped nozzle (0.8–1.2 MPa) sprays an alkaline degreasing agent (50–65°C), converting the oil stains into soluble substances through a chemical saponification reaction, while high-pressure impact assists in the removal. The cleaned long material then passes through an air knife blowing assembly, where a high-speed airflow (25–35 m / s) blows away any remaining liquid film on the surface, achieving rapid drying. The temperature is controlled at 50–65°C to enhance the activity of the degreasing agent and prevent excessively rapid evaporation of moisture, which could lead to alkali crystallization.

[0065] The induction heating softening unit uses a medium-frequency induction coil with a working frequency of 2-8kHz. It is used to heat the surface of the nail head and short rod residue in the long material flow to 650-750℃ and hold it for 15-30s, so that the surface work-hardened layer is partially annealed while the core retains the original metallographic structure. The cold heading recycle feeding unit is used to feed the softened material into the cold heading die cavity according to the working rhythm of the cold heading machine.

[0066] The alternating magnetic field generated by the medium-frequency induction coil (2-8kHz) induces eddy currents on the surface of the nail head. Due to the skin effect, heat is concentrated at a depth of 0.5-1.5mm on the surface. Heating to 650-750℃ (lower than the A1 line of steel, approximately 727℃) and holding for 15-30s causes recovery and recrystallization in the work-hardened zone, reducing the hardness from HV280-350 to HV180-220, while the core retains its original cold-drawn fibrous structure. After heating and holding, the material is immediately fed into the cold heading die cavity one by one by the cold heading machine cycle (60-200 pieces / min) from the cold heading recycling feed unit. At this point, the surface temperature of the material has naturally cooled to approximately 600℃, exhibiting good plasticity while the core retains its strength.

[0067] A visual inspection station is provided between the induction heating softening unit and the cold heading recycle feeding unit. The visual inspection station is used to identify and reject long materials that are deformed or out of size. The outlet of the unqualified material of the visual inspection station is connected to the fine chip flow branch 300 through the bypass pipeline.

[0068] The visual inspection station consists of a CCD industrial camera and an image processing system. The camera captures the outline image of each nail head and compares it with a preset standard template. Inspection indicators include curvature (>0.5mm), head defects (>10% area), and length deviation. Defective nails trigger a pneumatic pusher or flip-plate mechanism to move them into a bypass pipe. This pipe is directly connected to the inlet of the fine debris flow branch 300, allowing the defective material to mix with the fine debris before entering the degreasing → cleaning → briquetting process, thus avoiding waste.

[0069] The centrifugal oil removal unit is a horizontal screw discharge centrifuge with a working speed of 800-1200 rpm; the oil filtration unit is a two-stage filtration unit, including a primary filter screen and a precision filter screen connected in sequence. The oil removed by centrifugation is returned to the riveting machine processing oil circuit after secondary filtration.

[0070] The horizontal screw discharge centrifuge generates a centrifugal force of 300-600G at a speed of 800-1200rpm. Free oil in the fine chips is thrown out and discharged through the filter holes of the rotating drum, while the solid phase is continuously pushed out by the screw pusher. The extracted oil first passes through a primary filter (80 mesh) to intercept large particles of impurities, and then through a precision filter (200 mesh) to remove fine suspended matter. The cutting oil after two stages of filtration meets the cleanliness standards for use in riveting machine processing oil circuits and is returned to the machine tool for recycling via an oil pump, achieving a closed loop.

[0071] The magnetic separation and impurity removal unit uses a permanent magnet drum with a surface magnetic induction intensity ≥3000Gs; the discharge end of the magnetic separation and impurity removal unit is connected to an air classifier to remove non-metallic light impurities with a specific gravity of less than 1.5g / cm³ from the fine debris.

[0072] The permanent magnet drum has a surface magnetic induction intensity ≥3000Gs. When fine chips are evenly distributed onto the drum surface, ferromagnetic impurities (such as carbide tool particles and worn iron filings) are adsorbed onto the drum surface and detached by the back scraper as the drum rotates, while non-magnetic chips fall directly. The chips then enter an air classifier, where an upward airflow (1.5–3 m / s) blows away light impurities such as plastic labels, rubber gaskets, and fibers with a specific gravity <1.5 g / cm³, while metal chips with a specific gravity >5 g / cm³ settle and are collected. This two-stage impurity removal significantly improves the purity of the chips.

[0073] The hydraulic pressing unit is a four-column hydraulic press with a nominal pressure adjustable from 200 to 630 t. The density of the pressed cake is ≥6.2 g / cm³, and the weight of a single cake is 3 to 8 kg.

[0074] The four-column hydraulic press applies pressure of 200–630t (selected according to production line scale) through hydraulic cylinders. Under high pressure, the fine chips inside the mold undergo plastic deformation and cold welding, filling the gaps between the particles and reducing the volume to 1 / 5–1 / 8 of its original size. After holding the pressure for 3–5 seconds, the density of the cake reaches ≥6.2g / cm³ (close to 80% of the density of solid steel), with a single cake weighing 3–8kg, facilitating stacking and transportation. The pressure is adjustable to accommodate fine chips of different materials (e.g., lower pressure is required for aluminum chips).

[0075] An automated method for recycling and reusing rivet production waste includes the following steps:

[0076] S1. The waste material discharged from the rivet production line is sent to the vibrating pre-sorting mechanism 100. First, the material arch is broken by the arch-breaking structure to avoid jamming. Then, the material is sorted into long material flow and fine chip flow according to the length of the material by the grid screen.

[0077] S2. After being cleaned, dried by air knife blowing, and softened by induction heating in sequence, the long material flow is conveyed to the cold heading station for direct reuse.

[0078] S3. After being subjected to centrifugal degreasing, ultrasonic cleaning, and magnetic separation for impurity removal, the fine chip stream is hydraulically pressed into cakes for use as recycled material in smelting.

[0079] S4. The cutting oil obtained by centrifugal degreasing in step S3 is filtered and then returned to the riveting machine's processing oil circuit to achieve closed-loop reuse.

[0080] Steps S2 and S3 are executed in parallel and independently, respectively using processing parameters that match the characteristics of long and fine materials.

[0081] This method starts with physical sorting, solves the material jamming problem by breaking up arches, and uses grids to divert the material by length. The long material flow branch 400 adopts a short process of "cleaning and decontamination → drying → local annealing → direct reuse" to maximize the preservation of material value; the fine chip flow branch 300 adopts a long process of "degreasing → deep cleaning → impurity removal → densification," thoroughly purifying the material before it is used as smelting raw material. The two branches operate synchronously in time, without waiting for each other. The cutting oil separated by centrifugal degreasing is filtered and immediately reused, forming a closed-loop oil system. The entire process is coordinated by a PLC, achieving fully automated production.

[0082] In step S2, after the long material flow is softened by induction heating and before entering the cold heading station, unqualified materials with excessive deformation or out-of-tolerance dimensions are removed by visual inspection. The unqualified materials are transferred to the fine chip flow for processing in step S3. The reuse quality of the long material flow accounts for 40% to 60% of the total rivet waste, and the comprehensive utilization rate of waste is ≥92%.

[0083] Visual inspection, serving as a quality control step in the long material flow branch 400, removes deformed or dimensionally out-of-tolerance nail heads and automatically transfers them to the fine chip flow branch 300, preventing inferior materials from entering the cold heading process and causing scrap. The optimized economic range of 40%–60% for long material flow reuse is achieved—too low a ratio places a heavy burden on the fine chip flow branch 300 and results in low briquetting revenue; too high a ratio may affect the cold heading pass rate due to fluctuations in nail head quality. A comprehensive utilization rate of ≥92% means that less than 8% of the waste is ultimately discarded, far exceeding the approximately 85% of the traditional route.

[0084] Equipment configuration: Vibration pre-sorting mechanism with 100 grids adjusted to 22mm, tilt angle 8°, excitation frequency 960r / min; arch-breaking toothed roller with 25mm tooth pitch and 30r / min rotation speed. Long material flow branch 400: Long material cleaning unit with brush roller speed 150r / min, nozzle pressure 1.0MPa, alkaline degreasing agent 60℃; air knife blowing speed 30m / s; induction heating frequency 4kHz, power 80kW, heating to 700℃ and holding for 20s; visual inspection using a CCD industrial camera with a lens focal length of 16mm and an inspection accuracy of ±0.1mm. Fine debris flow branch 300: Centrifugal oil separator speed 1000rpm, oil filtration adopts 80 mesh + 200 mesh two-stage filter screen; ultrasonic cleaning frequency 33kHz, power 2.4kW, cleaning time 5min, cleaning fluid temperature controlled at 55~65℃; permanent magnet drum magnetic induction intensity 3500Gs; air classifier wind speed 2m / s; hydraulic briquetting machine nominal pressure 400t, briquetting diameter φ200mm, height 60mm.

[0085] Running data:

[0086] Long material streams account for 52% of the total waste mass. After cleaning, air knife blowing, and induction heating softening, the visual inspection pass rate is 98% (rejection rate is 2%). Qualified materials are fed into the cold heading machine by the feeding unit at 120 pieces / min, and the cold heading pass rate is 98.2% (98.7% for new materials, with no significant difference).

[0087] Fine debris accounts for 48%, the oil content after centrifugal degreasing is 1.6%, the surface cleanliness reaches Sa2.5 level after ultrasonic cleaning, the magnetic separation impurity removal efficiency is 99.2%, the air separation light impurity removal efficiency is 95%, the briquette density is 6.4g / cm³, and the weight of a single briquette is 5kg.

[0088] The deoiling wastewater is reused after two-stage filtration, saving 23% of cutting oil per month (approximately 1.2 tons / month).

[0089] The entire line is controlled by PLC, reducing the number of operators from 3 per shift to 1 for inspection, and achieving a comprehensive utilization rate of 93.5%.

[0090] Comparative example (using a universal fully crushed and briquetting line of the same production line)

[0091] After the nail heads and fine chips are crushed to <10mm, they are pressed into briquettes with a density of 6.1g / cm³. However, the high-quality nail heads are downgraded, and the recycling value is reduced by about 28%.

[0092] Without pre-sorting, the overall oil content is too high (still 3.2% after briquetting), and additional dust removal is required for smelting smoke.

[0093] The short rod frequently bridges in the hopper, requiring manual unclogging, resulting in 2-3 machine shutdowns per shift.

[0094] The overall utilization rate is about 85%, but the cutting oil cannot be recovered and is disposed of entirely as hazardous waste.

[0095] Instead of treating rivet waste as homogeneous material for uniform processing, the process involves source diversion based on differences in morphology (length, oil content, reformability), with customized physicochemical treatment processes for each type of material. The two branches are arranged side-by-side in space, operate synchronously in time, do not intersect in material flow, and are coordinated by the same PLC system but adjust their parameters independently.

[0096] Example 2

[0097] The automatic recycling and reuse device for rivet production waste in this embodiment can be improved as follows compared with the technical solution of Embodiment 1:

[0098] After pre-sorting, a permanent magnet roller (magnetic induction intensity 2500Gs) is added at the inlet of the long material flow branch 400 to separate the steel nail heads from the aluminum nail heads: the steel nail heads flow through the long material flow branch 400 (induction heating parameters adjusted to 700℃ / 20s), while the aluminum nail heads are collected separately (packaged as high-purity scrap aluminum or recycled in a smelting furnace without induction heating softening treatment), and then sent to their respective cold heading machines or smelting furnaces. The fine chip flow branch 300 remains unchanged, but an eddy current separator is added (for separating aluminum chips from steel chips). This modification also falls within the protection scope of this invention.

[0099] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. An automatic recycling and reuse device for rivet production waste, comprising a pre-sorting mechanism, a waste processing mechanism, and a central PLC control system, characterized in that: The pre-sorting mechanism is a vibrating pre-sorting mechanism. Its feed hopper outlet is equipped with an anti-bridging and arch-breaking device, and its screen surface is equipped with an adjustable grid, which is used to separate rivet production waste into long material streams and fine chip streams according to length. The waste treatment mechanism includes parallel and independently arranged long material flow branches and fine debris flow branches; The long material flow branch is connected in sequence along the material direction to a long material cleaning unit, an air knife blowing assembly, an induction heating softening unit, and a cold heading reusable feeding unit, which are used to transport the billet cutting residue and short rod residue to the cold heading station for reuse after cleaning, drying, and softening. The fine debris flow branch is connected in sequence along the material direction to a centrifugal degreasing unit, an ultrasonic cleaning unit, a magnetic separation and impurity removal unit, and a hydraulic pressing unit, which are used to press the fine debris into cakes after degreasing, cleaning and impurity removal. The oil outlet of the centrifugal degreasing unit is connected to an oil filtration unit, and the oil outlet of the oil filtration unit is used to connect to the riveting machine's processing oil circuit to achieve closed-loop recovery of cutting oil. The central PLC control system is connected to the actuators of the vibration pre-sorting mechanism, the long material flow branch, and the fine debris flow branch, respectively, and is used to control the coordinated automatic operation of the two branches.

2. The automatic recycling and reuse device for rivet production waste according to claim 1, characterized in that, The grid gap of the vibrating pre-sorting mechanism is infinitely adjustable within the range of 15mm to 40mm, and the screen surface inclination angle is adjustable within the range of 5° to 15°, which is suitable for sorting waste materials of M3 to M12 rivets. The anti-bridging and arch-breaking device includes a pair of anti-bridging toothed rollers rotating in opposite directions. The adjustable grid includes parallel fixed grid bars and movable grid bars, side guide grooves, a gap adjustment assembly containing an adjusting screw and a linkage rod, a scale and a locking nut. By rotating the adjusting screw, the linkage rod is driven to make the movable grid bars move synchronously along the guide groove, which can realize the infinite adjustment and position locking of the grid gap.

3. The automatic recycling and reuse device for rivet production waste according to claim 1, characterized in that, The long material cleaning unit is equipped with a rotating brush roller and a high-pressure fan-shaped nozzle. The spray pressure of the high-pressure fan-shaped nozzle is 0.8 to 1.2 MPa. The long material cleaning unit uses an alkaline degreasing agent aqueous solution as the cleaning fluid, and the working temperature is 50 to 65°C. The air knife blowing assembly is located at the discharge end of the long material cleaning unit and is used to blow away the residual cleaning fluid film on the surface of the long material.

4. The automatic recycling and reuse device for rivet production waste according to claim 1, characterized in that, The induction heating softening unit uses a medium-frequency induction coil with a working frequency of 2-8kHz. It is used to heat the surface of the nail head and short rod residue in the long material flow to 650-750℃ and hold it for 15-30s, so that the surface work-hardened layer is partially annealed while the core retains the original metallographic structure. The cold heading recycle feeding unit is used to feed the softened material into the cold heading mold cavity according to the working rhythm of the cold heading machine.

5. The automatic recycling and reuse device for rivet production waste according to claim 1, characterized in that, A visual inspection station is provided between the induction heating softening unit and the cold heading recycle feeding unit. The visual inspection station is used to identify and reject long materials that are deformed or out of size. The outlet of the unqualified material at the visual inspection station is connected to the fine chip flow branch through a bypass pipeline.

6. The automatic recycling and reuse device for rivet production waste according to claim 1, characterized in that, The centrifugal deoiling unit is a horizontal screw discharge centrifuge with a working speed of 800-1200 rpm; the oil filtration unit is a two-stage filtration unit, including a primary filter screen and a precision filter screen connected in sequence. The oil extracted by centrifugation is returned to the riveting machine processing oil circuit after secondary filtration.

7. The automatic recycling and reuse device for rivet production waste according to claim 1, characterized in that, The magnetic separation and impurity removal unit adopts a permanent magnet drum with a surface magnetic induction intensity ≥3000Gs; the discharge end of the magnetic separation and impurity removal unit is connected to an air classifier to remove non-metallic light impurities with a specific gravity of less than 1.5g / cm³ from the fine debris.

8. The automatic recycling and reuse device for rivet production waste according to claim 1, characterized in that, The hydraulic pressing unit is a four-column hydraulic press with a nominal pressure adjustable from 200 to 630 t. The density of the pressed cake is ≥6.2 g / cm³, and the weight of a single cake is 3 to 8 kg.

9. A method for automatically recycling and reusing rivet production waste, characterized in that, Includes the following steps: S1. The waste material discharged from the rivet production line is sent to the vibrating pre-sorting mechanism. First, the material arch is broken by the arch-breaking structure to avoid jamming. Then, the material is sorted into long material flow and fine chip flow according to the length of the material by the grid screen. S2. After being cleaned, dried by air knife blowing, and softened by induction heating in sequence, the long material flow is conveyed to the cold heading station for direct reuse. S3. After being subjected to centrifugal degreasing, ultrasonic cleaning, and magnetic separation for impurity removal, the fine chip stream is hydraulically pressed into cakes for use as recycled material in smelting. S4. The cutting oil obtained by centrifugal degreasing in step S3 is filtered and then returned to the riveting machine's processing oil circuit to achieve closed-loop reuse. Steps S2 and S3 are executed in parallel and independently, respectively using processing parameters that match the characteristics of long and fine materials.

10. The method for automatic recycling and reuse of rivet production waste according to claim 9, characterized in that, In step S2, after the long material flow is softened by induction heating and before entering the cold heading station, unqualified materials with excessive deformation or out-of-tolerance dimensions are removed by visual inspection. The unqualified materials are transferred to the fine chip flow for processing in step S3. The reuse quality of the long material flow accounts for 40% to 60% of the total rivet waste, and the comprehensive utilization rate of waste is ≥92%.

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