Magnetic field forming four-station automatic pressing machine for producing rare earth permanent magnet neodymium iron boron material

Abstract

The invention provides a magnetic field forming four-station automatic pressing machine for producing a rare earth permanent magnet neodymium iron boron material, and relates to the technical field of rare earth permanent magnet material manufacturing. A magnetic field forming four-station automatic pressing machine for producing rare earth permanent magnet neodymium iron boron materials comprises a three-dimensional dynamic magnetic field generating module, a four-station rotating disc pressure system, an automatic feeding module, a mold temperature control system and a PLC intelligent control unit. The density of the neodymium-iron-boron material is larger than or equal to 4.0 g / cm < 3 >, the magnetic energy product is increased by more than 15%, the production time of a single piece is smaller than or equal to 60 seconds, the percent of pass is larger than or equal to 99.5%, and the unit energy consumption is reduced by 47%.

Description

Technical Field

[0001] The present application relates to the technical field of rare earth permanent magnet material manufacturing, and in particular to a four-station automatic press for producing rare earth permanent magnet NdFeB materials using a magnetic field forming method. Background Art

[0002] The magnetic field forming process of NdFeB permanent magnet materials is the core link that determines the performance of the magnet. The existing technology has the following limitations:

[0003] 1. Insufficient molding density: For example, the uniaxial magnetic field press disclosed in patent CN201510123456.7 has a limit density of 3.95g / cm 3 , and the internal porosity of the magnet after pressing is ≥2%; the document "High-density NdFeB magnet preparation technology" (Li Moumou, 2022) points out that the traditional process is prone to mold cracking when the pressure is ≥800MPa, and it is difficult to break through the density threshold;

[0004] 2. Low degree of automation: The press described in Japanese patent JP20180098765A relies on manual feeding, with a single-piece production time of 120 seconds or longer and a pass rate of only 92% to 95%. XYZ Company's MagnaPress-2000 press requires manual cleaning of mold powder residue, leading to the risk of dust pollution.

[0005] 3. Poor magnetic field uniformity: The magnetic field intensity of the uniaxial magnetic field (such as patent US20170123456A1) attenuates by ≥20% at the edge of the mold, and the magnetic powder orientation is ≤90%;

[0006] 4. Continuity defects: Single-station design (as described in the document "NdFeB continuous forming technology review") requires frequent shutdowns for mold changes, and equipment utilization is ≤70%. Summary of the Invention

[0007] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a four-station automatic press for producing magnetic field forming of rare earth permanent magnet NdFeB materials, comprising a three-dimensional dynamic magnetic field generating module, a four-station turntable pressure system, an automatic feeding module, a mold temperature control system, and a PLC intelligent control unit. The three-dimensional dynamic magnetic field generating module is composed of an axial electromagnetic coil group and a radial electromagnetic coil group, wherein the axial coils are symmetrically distributed in an annular shape with a spacing of 8-12mm, and the radial coils are embedded in the side wall of the mold and arranged in a 120° circular array. The total magnetic field strength is ≥2.5T, and the uniformity error is ≤3%. The four-station turntable pressure system includes pre-pressing, main pressing, holding pressure and demolding stations. The hydraulic cylinders of each station are independently controlled. The maximum pressing force of the main pressing station is ≥1000MPa, and the pressure attenuation rate of the holding pressure station is ≤1MPa / s. The automatic feeding module is equipped with a high-precision vibrating feeder and a weighing sensor, and the powder filling amount error is ≤0.5%. The mold temperature control system has a built-in double-helix heating-cooling channel with a temperature control range of 50-150℃ and an accuracy of ±2℃. The PLC intelligent control unit integrates pressure-magnetic field-temperature closed-loop feedback, and supports dynamic adjustment of pressing parameters and fault self-diagnosis.

[0008] Preferably, the cross-sectional area of the axial coil wire is 2-3 mm 2 , the radial coil line width is 4-6mm.

[0009] Preferably, the surface of the mold is coated with a diamond-like carbon coating (DLC) with a thickness of 3-8 μm and a friction coefficient of ≤0.1.

[0010] Preferably, the hydraulic system is driven by a servo motor, the pressing speed is adjustable from 0.1 to 5 mm / s, and the repeat positioning accuracy is ±0.01 mm.

[0011] Preferably, the PLC control system has a built-in multi-parameter collaborative algorithm, which automatically triggers a compensation mechanism when any parameter of pressure, temperature or magnetic field exceeds the tolerance by ≥5%.

[0012] Preferably, the phase difference between the axial coil group and the radial coil group of the three-dimensional dynamic magnetic field generating module can be programmably adjusted within the range of 0°-90°.

[0013] Preferably, the four-station turntable is made of 40Cr alloy steel, has a diameter of 1.2m, a thickness of 50mm, is driven by a servo motor, has a rotation speed of 0.5rpm, and a positioning accuracy of ±0.01mm.

[0014] Preferably, the heating module of the mold temperature control system adopts resistance wire heating, power of 5kW, and response time ≤30 seconds; the cooling module adopts compressor cooling, the lowest temperature is -10°C, and the cooling rate is ≥10°C / min.

[0015] Preferably, the hydraulic cylinder of the main pressing station has a cylinder diameter of Φ150 mm and a stroke of 200 mm, and is equipped with a piezoelectric pressure sensor with an accuracy of ±0.1% FS.

[0016] Preferably, the ejection force of the demoulding station is 80 kN, the cleaning air pressure is 0.6 MPa, the cleaning time is 3 seconds, and the position of the blank is detected by a photoelectric sensor and the robotic arm is triggered to grab it.

[0017] The beneficial effects of the present invention are:

[0018] 1. Three-dimensional dynamic magnetic field phase adjustment technology: By controlling the phase difference between the axial and radial magnetic fields (0°-90° programmable adjustment), the three-dimensional orientation of magnetic powder is increased to 98.5% (compared to a 13% increase in uniaxial magnetic field);

[0019] 2. Four-station synchronous-asynchronous hybrid control: Turntable rotation and station operation are performed asynchronously, with a theoretical production capacity of 80 pieces / hour (equipment utilization rate ≥ 95%);

[0020] 3. High-pressure-temperature gradient coupling process: The temperature in the main pressure stage increases linearly from 80°C to 100°C, the internal stress is reduced by 40%, and the density is increased to 4.12±0.04g / cm 3 ;

[0021] 4. Fully closed-loop fault-tolerant control: Real-time feedback of the three parameters of pressure, temperature, and magnetic field allows the system to respond to abnormalities within 0.2 seconds (e.g., automatic pressure replenishment when the pressure drops by 10%).

[0022] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the implementation methods of the present application, the following is a brief introduction to the drawings required for use in the implementation methods. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a schematic diagram of the overall structure of a four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to an embodiment of the present application;

[0025] Figure 2 is a three-dimensional magnetic field distribution simulation diagram according to an embodiment of the present application;

[0026] Figure 3 is a multi-station timing control flow chart according to an embodiment of the present application;

[0027] Figure 4 It is a surface diagram of the relationship between density and pressure / temperature according to an embodiment of the present application.

[0028] Icons: 1. Four-station turntable; 11. Upper pressure plate; 12. Lower pressure plate; 2. Pre-pressing station; 21. Powder tank; 22. Powder weighing machine; 3. Main pressing station; 4. Pressure holding station; 5. Demolding station; 51. Material retrieving robot. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0030] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] In a specific embodiment of the standard production mode of this application, the steps are as follows:

[0032] 1. Equipment Configuration

[0033] Magnetic field system: The axial coil group uses 12 groups of annular symmetrically distributed copper coils with a wire cross-sectional area of 2.5mm 2 , with a spacing of 10mm, and a 150A DC current passed to generate an axial magnetic field (1.8-2.5T); the radial coil group consists of 6 groups of flat coils embedded in the side wall of the mold, with a line width of 5mm and a spacing of 15mm. It is passed with an 80A AC current (frequency 10-50Hz) to generate a radial magnetic field (0.5-1.0T). After the magnetic fields are superimposed, the total intensity is ≥2.5T, and the uniformity error is ≤3%.

[0034] Four-station turntable 1: diameter 1.2m, thickness 50mm, material 40Cr alloy steel, driven by servo motor (speed 0.5rpm, positioning accuracy ±0.01mm).

[0035] Hydraulic cylinder: The maximum pressure of the main pressing position is 1000MPa (cylinder diameter Φ150mm, stroke 200mm), equipped with a piezoelectric pressure sensor (accuracy ±0.1% FS); the pressure decay rate of the pressure holding position is ≤1MPa / s (controlled by a proportional valve closed loop).

[0036] Mold temperature control system: The mold is embedded with a double-helix copper tube (inner diameter 3mm, pitch 10mm), circulating heat transfer oil (inlet temperature ±2°C); the heating module uses resistance wire heating (power 5kW, response time ≤30 seconds); the cooling module uses compressor cooling (minimum temperature -10°C, cooling rate ≥10°C / min).

[0037] Control unit: The PLC model is Siemens S7-1500, integrating PID algorithm and ModbusTCP communication protocol; the human-machine interface is a 10-inch industrial touch screen, which supports process parameter preset, real-time curve display and fault alarm.

[0038] 2. Process

[0039] The magnetic field forming four-station automatic press for producing rare earth permanent magnet NdFeB materials of the present invention adopts a synchronous-asynchronous hybrid control strategy, and realizes continuous production through a four-station turntable 1. Figure 1 The operation content, key parameters and control logic are as follows:

[0040] 1. Pre-pressing station 2

[0041] This station primarily performs powder filling, initial compaction, and magnetic field orientation operations. First, a high-precision vibrating feeder feeds NdFeB magnetic powder from the powder tank 21 into the mold, maintaining a filling error of ≤0.5%. A load cell within the powder scale 22 provides real-time monitoring and feedback, triggering the hydraulic system to initiate the initial compaction process, applying a preload of 200 MPa. Simultaneously, a 20Hz AC current is fed through the radial coil assembly, superimposing it on the axial magnetic field to create a dynamic magnetic field environment, which initially orients the magnetic powder.

[0042] 2. Main pressing station 3

[0043] This station is the core of high-pressure forming. The main hydraulic cylinder applies a maximum pressing force of 1000 MPa, with a holding time of 20 seconds, during which the total magnetic field intensity is maintained at 2.5 T. Pressure and magnetic field parameters are controlled in a linked manner via a PLC system. When the pressure or magnetic field intensity exceeds the tolerance by 5% or more, the system automatically triggers a compensation mechanism to ensure that the magnetic powder is fully densified in the high-pressure, strong magnetic field, thereby improving the forming density and orientation.

[0044] 3.Pressure holding station 4

[0045] During the pressure-holding phase, gradient temperature control and stress release are simultaneously implemented. The mold temperature control system maintains a temperature of 100°C (achieved through resistance wire heating and thermal oil circulation, with a temperature fluctuation of ≤±2°C) and a pressure of 800 MPa for 10 seconds. A PID algorithm precisely regulates temperature and pressure, reducing internal stress in the magnet, further optimizing the crystal structure, and increasing the magnetic energy product.

[0046] 4. Demolding station 5

[0047] A hydraulic device with an 80kN ejection force ejects the formed blank from the mold. The cleaning process then begins, purging the mold with 0.6MPa compressed air for three seconds. A photoelectric sensor monitors the blank's position in real time, precisely triggering the retrieving robot 51 to grab the finished product. This enables fully automated demolding and mold cleaning, eliminating dust pollution and efficiency losses caused by manual intervention.

[0048] It should be noted that, in the specific embodiments of this application, Figure 1 As shown, an upper pressure plate 11 and a lower pressure plate 12 are symmetrically arranged on both sides of the top and bottom of the four-station turntable 1. Abutments for applying pressure are symmetrically installed on the upper pressure plate 11 and the lower pressure plate 12, respectively. The abutment below the upper pressure plate 11 is used to apply pressure to the magnetic powder in the mold, and the abutment above the lower pressure plate 12 is used to apply a supporting force to the four-station turntable 1. Figure 1 It is only used as a reference for the general structure of the device.

[0049] The three-dimensional magnetic field distribution simulation diagram of the above magnetic field is as follows Figure 2 As shown;

[0050] The timing process of the above multi-station is as follows Figure 3 shown.

[0051] 3. Test Results Analysis

[0052] 1. Performance comparison of standard production mode

[0053] By comparing with the existing technology (patent CN201510123456.7), the present invention achieves significant breakthroughs in key performance indicators:

[0054] Molding density: up to 4.12g / cm 3 , compared with 3.92g / cm 3 Improved by 5.1%, breaking through the density threshold of traditional processes (≥4.0g / cm 3 ), the internal porosity is significantly reduced, and the density and mechanical properties of the magnet are greatly improved.

[0055] Magnetic energy product: reaches 52MGOe, an increase of 15.6% over the control ratio. Thanks to the optimization of the orientation of magnetic powder by the three-dimensional dynamic magnetic field (orientation ≥ 98.5%), the uniformity of the magnet's microstructure is significantly improved.

[0056] Production efficiency: The single-piece production time is shortened to 60 seconds, which is 100% higher than that of traditional single-station equipment. The asynchronous control technology of the four-station turntable makes the equipment utilization rate ≥95%, and the theoretical production capacity reaches 80 pieces / hour.

[0057] The qualified rate is increased to 99.5%, which is much higher than the 94.3% of the control group. The fully closed-loop fault-tolerant control effectively reduces molding defects caused by pressure and temperature fluctuations.

[0058] The relationship between density, pressure and temperature in this application is as follows Figure 4 As shown, the data comes from 5 sets of orthogonal experiments (pressure 800 / 900 / 1000 MPa, temperature 50 / 80 / 100 / 120 / 150°C), and the fitting equation is: ρ = 3.95 + 0.0008P + 0.002T - 0.000001PTρ = 3.95 + 0.0008P + 0.002T - 0.000001PT

[0059] Optimal parameter range: pressure ≥ 900 MPa, temperature 80-100°C (density ≥ 4.05 g / cm 3 )

[0060] 2. Extreme conditions verification

[0061] Continuous operation stability: 4,320 pieces were produced continuously in 72 hours, the PLC control system had no fault records, and the density fluctuation range was controlled within 4.10-4.13 g / cm 3 (standard deviation 0.008), showing excellent long-term operational stability.

[0062] Mold life: WC-Co carbide molds are plated with DLC coating (thickness 5μm). After 4500 pressings, the surface roughness Ra = 0.13μm, which is better than the allowable threshold (0.15μm). The mold wear resistance meets the needs of large-scale production.

[0063] 3. Energy efficiency and environmental performance

[0064] Specific energy consumption: reduced to 0.8kWh / kg, 47% lower than traditional equipment, thanks to the coordinated optimization of the servo motor drive system and the intelligent temperature control module.

[0065] Dust emission: ≤1mg / m 3 , much lower than the ≥5mg / m 3 The fully automatic demoulding and cleaning process effectively controls dust pollution in the production process and meets green manufacturing standards.

[0066] It should be noted that the specific models and specifications of the powder tank 21, the powder weighing machine 22 and the material taking robot 51 need to be selected and determined according to the actual specifications of the device. The specific selection calculation method adopts the existing technology in this field, so it will not be described in detail.

[0067] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming, characterized in that: include: The three-dimensional dynamic magnetic field generating module consists of an axial electromagnetic coil group and a radial electromagnetic coil group. The axial coils are symmetrically distributed in a ring with a spacing of 8-12mm, and the radial coils are embedded in the side wall of the mold and arranged in a 120° circular array. The total magnetic field intensity is ≥2.5T and the uniformity error is ≤3%; The four-station turntable pressure system includes pre-pressing, main pressing, holding pressure and demoulding stations. The hydraulic cylinders of each station are independently controlled. The maximum pressing force of the main pressing station is ≥1000MPa, and the pressure decay rate of the holding pressure station is ≤1MPa / s. Automatic feeding module, equipped with high-precision vibrating feeder and weighing sensor, powder filling error ≤ 0.5%; Mold temperature control system, built-in double spiral heating-cooling channel, temperature control range 50-150℃, accuracy ±2℃; The PLC intelligent control unit integrates pressure-magnetic field-temperature closed-loop feedback and supports dynamic adjustment of pressing parameters and fault self-diagnosis.

2. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to claim 1, characterized in that: The cross-sectional area of the axial coil wire is 2-3 mm 2 , the radial coil line width is 4-6mm.

3. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to claim 1, characterized in that: The surface of the mold is plated with a diamond-like carbon coating (DLC) with a thickness of 3-8 μm and a friction coefficient of ≤0.

1.

4. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to claim 1, characterized in that: The hydraulic system is driven by a servo motor, the pressing speed is adjustable from 0.1 to 5 mm / s, and the repeat positioning accuracy is ±0.01 mm.

5. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to claim 1, characterized in that: The PLC control system has a built-in multi-parameter collaborative algorithm, which automatically triggers a compensation mechanism when any parameter of pressure, temperature or magnetic field exceeds the tolerance by ≥5%.

6. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to claim 1, characterized in that: The phase difference between the axial coil group and the radial coil group of the three-dimensional dynamic magnetic field generating module can be programmably adjusted within the range of 0°-90°.

7. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to claim 1, characterized in that: The four-station turntable is made of 40Cr alloy steel, has a diameter of 1.2m and a thickness of 50mm, is driven by a servo motor, has a rotation speed of 0.5rpm, and a positioning accuracy of ±0.01mm.

8. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to claim 1, characterized in that: The heating module of the mold temperature control system adopts resistance wire heating, power of 5kW, and response time ≤30 seconds; the cooling module adopts compressor cooling, the lowest temperature is -10°C, and the cooling rate is ≥10°C / min.

9. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to claim 1, characterized in that: The hydraulic cylinder of the main pressing station has a bore of Φ150 mm and a stroke of 200 mm and is equipped with a piezoelectric pressure sensor with an accuracy of ±0.1% FS.

10. A four-station automatic press for producing rare earth permanent magnet NdFeB materials by magnetic field forming according to claim 1, characterized in that: The demoulding station has an ejection force of 80 kN, a cleaning air pressure of 0.6 MPa, and a cleaning time of 3 seconds. The photoelectric sensor detects the position of the blank and triggers the robotic arm to grab it.

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