A soft and brittle material micro-grinding device based on magnetic plasticization-vibration suppression energy assignment

Abstract

The application provides a soft and brittle material micro-grinding device based on magnetic plasticization and vibration suppression energy, which comprises a grinding machine, a clamp, a magnetic field generating device, a motor spindle, a grinding head and a workpiece, the magnetic field generating device is composed of an iron core, a coil, a support, a power supply and a wire, is placed near the workpiece, the magnetically conductive iron core is fixed on the support, a plurality of coils are connected in series on the iron core and connected with the power supply to form a loop, the power supply is an alternating power supply, the magnetic field generating device can generate adjustable and uniform alternating magnetic field; the workpiece is a soft and brittle material, is fixed by the clamp and placed below the grinding head, and a complex curved surface needs to be processed on the surface of the workpiece; the slender grinding head is composed of a magnetically conductive base body, an electroplated layer and superhard abrasive, is installed on the motor spindle, the motor spindle is installed on the grinding machine and can drive the grinding head to rotate at high speed; the magnetic plasticization effect of the surface layer material of the workpiece is utilized to improve the processing plasticity of the workpiece and the magnetic vibration suppression effect of the grinding head is utilized to reduce the vibration amplitude of the workpiece.

Description

Technical Field

[0001] This invention relates to the field of micro-grinding, and in particular to a micro-grinding device for soft and brittle materials based on magnetostrictive-vibration-suppression energy. Technical Background

[0002] Soft and brittle materials play an irreplaceable and crucial role in modern high-end technology and industry, especially in the field of optics. Typical soft and brittle materials include semiconductor crystals, optical crystals, and some polymers such as plexiglass. They have important characteristics such as low hardness, high brittleness, and strong anisotropy. Soft and brittle materials are mainly used to manufacture infrared focal plane array detectors, room temperature nuclear radiation detectors, and deep ultraviolet lithography objectives. These parts are widely used in ultraviolet lithography systems and precision infrared optical systems.

[0003] When machining small parts made of soft and brittle materials using existing methods, it is often difficult to achieve both machining efficiency and machining accuracy simultaneously. Grinding is the most important step in the machining process of soft and brittle material workpieces, as it is the key step to achieve nanoscale roughness and extremely high surface accuracy. In existing machining technologies, chemical mechanical grinding can achieve a near-damage-free surface, but the material softening rate is slow, the machining time is long, and the efficiency is low. Traditional mechanical grinding is a mature process with relatively high efficiency, but due to the characteristics of soft and brittle materials, the solidified hard abrasive is prone to producing scratches, microcracks, and residual stress layers on the surface of the machined workpiece, affecting the machining accuracy and service performance of the workpiece. Moreover, when using a slender grinding head in traditional mechanical grinding, the poor rigidity of the grinding head will cause vibration under the action of multiple factors such as grinding force, centrifugal force, and cutting heat during high-speed rotation and feeding, which accelerates the wear of the grinding head. In addition, the vibration of the high-speed rotating grinding head will also reduce the machining dimensional accuracy and shape accuracy of the workpiece.

[0004] The patent CN114589563A, entitled "An Ultra-Precision Grinding Method with Controllable Ductility Domain Machining Dimensions," modifies the surface of workpieces such as silicon carbide and calcium fluoride using plasma to form a modified layer. A magnetron homogenization device is then used to uniformly apply the plasma flow, followed by ultra-precision grinding with a diamond wheel. The grinding depth is controlled within the sum of the modified layer thickness and the removal depth of the ductile domain. However, this technical solution still has the following problems: the modification effect of the plasma jet is greatly affected by the curvature of the workpiece surface; for complex curved surfaces of soft and brittle materials, the actual incident angle and action distance of the jet will continuously change with the surface morphology, making it difficult to maintain a consistent degree of modification in different areas of the workpiece surface. This makes it difficult to achieve the expected effect of the modification process, and the consistency of the entire processing cannot be guaranteed.

[0005] The patent CN121928411A, entitled "A Stepped Grinding and Polishing Method for Removing Scale in the Plastic Domain by Magnetic Field Control," describes a process where a magnetic field perpendicular to the workpiece surface is applied to enhance the workpiece's plasticity. This is followed by plastic domain grinding, then a magnetic rheological polishing fluid is supplied to the grinding area while maintaining a constant magnetic field strength for a combined grinding-polishing process. Finally, polishing is performed by adjusting the grinding wheel parameters. All these steps are completed sequentially on the same machine tool to achieve full plastic domain processing. However, this technical solution still has the following problems: the magnetic particles in the magnetic rheological polishing fluid are easily embedded in the surface of soft and brittle workpieces, and the chemical components can corrode the crystal surfaces of soft and brittle materials such as calcium fluoride, causing difficult-to-remove damage to the workpiece surface and reducing its processing accuracy. Furthermore, it does not consider the high-frequency vibration of the grinding wheel caused by unstable force during grinding and the processing damage it causes to the workpiece material, resulting in compromised processing stability. Therefore, there is an urgent need to develop a new processing device to achieve high-precision, high-efficiency, and low-cost processing of small parts made of soft and brittle materials. Summary of the Invention

[0006] To overcome the shortcomings of existing micro-grinding devices for soft and brittle materials, this invention provides a micro-grinding device for soft and brittle materials based on magnetostrictive plasticization and vibration damping. The device comprises a grinding machine, a fixture, a magnetic field generator, a motor spindle, a slender grinding head, and a workpiece. The magnetic field generator consists of an iron core, a coil, a support, a power supply, and wires. The iron core is fixed to the support, and the coils and iron cores are paired and multiple sets are provided. The support is fixed to the grinding machine, and the power supply is connected to the coils via wires to form a circuit. The grinding head consists of a magnetically conductive substrate, an electroplated layer, and superhard abrasive, and is mounted on the motor spindle. The workpiece is a soft and brittle material, fixed by the fixture, and requires grinding a complex curved surface. The grinding head contacts the workpiece surface material within 10 minutes. -9 seconds ~10 -7 Within seconds, dislocations occur in the surface material of the workpiece. Crystal ions containing spin-left and spin-right electrons on the dislocation lines approach the free ions in the surface material and undergo electron transfer, i.e., spin-left electrons transfer to the free ions. Subsequently, the crystal ions become de-charged ions, and the free ions become charged ions. The charged ions combine with the de-charged ions to form high-binding-energy singlet free radicals. The magnetic field generated after the magnetic field generator is energized can make the spin-right and spin-left electrons rotate in the same direction, i.e., the high-binding-energy singlet free radicals are transformed into low-binding-energy triplet free radicals. The reduction in the binding energy of the free radicals helps to improve the processing plasticity of the workpiece surface material, i.e., the magnetostrictive plasticizing effect of the workpiece. In addition, the magnetic field can also generate eddy currents in the high-speed rotating grinding head during the feeding process. The eddy currents are further subjected to Ampere forces opposite to the direction of the grinding head's movement in the applied magnetic field, i.e., the grinding head is subjected to electromagnetic damping forces opposite to its vibration force, thus reducing the amplitude of the grinding head, i.e., the magnetostrictive vibration damping effect of the grinding head.

[0007] The coils are wound on corresponding iron cores, and multiple coils are connected in series. The first end of the first coil and the last end of the last coil are connected to the positive and negative terminals of the power supply, respectively. The winding directions of adjacent coils are opposite, so that the polarities of adjacent iron cores are opposite, thereby forming a closed magnetic circuit passing through the workpiece and the grinding head. The iron core is made of a soft magnetic material with a relative permeability ≥500. The power supply for the magnetic field generating device is an AC power supply, with the current adjustable from 0 to 10 A and the voltage adjustable from 0 to 60 V, which can control the magnetic field generating device to produce a uniform alternating magnetic field with an adjustable magnetic field strength from 0 to 200 mT.

[0008] The working part of the grinding head is needle-shaped, spherical, disc-shaped, or columnar, with a radial dimension ranging from 0.02 to 1 mm and an aspect ratio ≥ 5. The substrate is made of a ferromagnetic material with a relative permeability ≥ 200. The electroplating layer and superhard abrasive grains cover all or part of the working surface of the grinding head. The superhard abrasive grains are diamond or CBN, with a particle size ranging from 1 to 50 μm.

[0009] The workpiece material is a soft and brittle material such as calcium fluoride, zinc selenide, zinc cadmium telluride, and potassium dihydrogen phosphate.

[0010] The following beneficial effects can be obtained by using the micro-grinding device for soft and brittle materials based on magnetostrictive plasticity and vibration damping as described in this invention.

[0011] ① Wide adaptability to processing soft and brittle materials: Through the synergistic effect of the magnetic field and the grinding head, this device significantly expands the applicable range of processing soft and brittle materials. Under the action of an external magnetic field, the surface material of the soft and brittle workpiece can produce a magnetostrictive plasticizing effect, which makes the originally brittle surface material exhibit enhanced plastic flow ability at the microscale. Then, it is ground away by the grinding head after being suppressed by the magnetostrictive vibration suppression effect. The resulting processing mechanism of "plasticizing first, suppressing vibration and then removing" enables the device to be stably applied to the processing of a variety of low hardness and high brittleness optical materials, including but not limited to calcium fluoride, zinc selenide single crystals, and typical soft and brittle materials such as zinc cadmium telluride and potassium dihydrogen phosphate.

[0012] ② Effectively achieves high-precision and high-efficiency machining of soft and brittle materials: Under the assistance of a magnetic field, the removal behavior of soft and brittle materials on the surface of the workpiece is transformed from traditional brittle removal to plastic removal; this reduces the number of microcracks on the surface of the workpiece after machining; and the electromagnetic damping force generated by the high-speed rotating feed slender grinding head under the action of the magnetic field also significantly suppresses the high-frequency vibration generated during the machining feed, thus improving the surface shape accuracy of the workpiece after machining; under the coupled effect of the above two mechanisms, the grinding machine can use a faster feed speed to process with little or no damage to the workpiece surface, directly improving the material removal rate per unit time, reducing the processing time required, and improving processing efficiency.

[0013] ③ Significantly reduces high-frequency vibration of the grinding head: Due to its poor rigidity, the slender grinding head is prone to high-frequency vibration during high-speed rotation and feeding, due to the coupling effect of multiple dynamic loads such as grinding force and centrifugal force. With the help of an external magnetic field, the magnetically conductive grinding head generates an electromagnetic damping force in the opposite direction of vibration during the movement, forming an effective magnetostrictive vibration suppression effect, which significantly suppresses the high-frequency vibration of the grinding head. The reduction in vibration amplitude directly weakens the abnormal contact and impact effect between the grinding head and the workpiece, effectively improving the dynamic stability and shape retention capability of the grinding head, thereby ensuring the smoothness of the processing and surface consistency.

[0014] ④ Significantly improves the service performance and reliability of micro parts: In traditional grinding, soft and brittle materials are prone to micro-defects such as microcracks, residual stress layers and surface pits due to brittle removal. This device guides the workpiece material to be removed in a plastic flow manner during the processing through the magnetostrictive plasticizing effect of the workpiece, which inhibits brittle removal from the source. This makes the material removal process more stable and continuous, significantly reduces the density of surface defects, and greatly thins or even eliminates the surface damage layer. It enhances the structural reliability of the processed parts under extreme service environments and provides key manufacturing technology support for fields such as deep ultraviolet lithography, high-power laser systems and precision infrared optics. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a micro-grinding device for soft and brittle materials based on magnetostrictive plasticity and vibration damping.

[0016] Figure 2 for Figure 1 A schematic diagram of the grinding head.

[0017] Figure 3 for Figure 1 A schematic diagram of the magnetic field generating device.

[0018] Figure 4 This is a schematic diagram of the workpiece to be processed according to the present invention.

[0019] Figure 5 This is a schematic diagram of the magnetoplasticization of the present invention.

[0020] Figure 6 This is a schematic diagram of the magnetostrictive vibration suppression of the present invention.

[0021] Figure reference numerals: 1. Grinding machine; 2. Fixture; 3. Magnetic field generating device; 3-1. Iron core; 3-2. Coil; 3-3. Support; 3-4. Power supply; 3-5. Wire; 4. Motor spindle; 5. Grinding head; 5-1. Substrate; 5-2. Electroplating layer; 5-3. Superhard abrasive; 5-4. Eddy current; 6. Workpiece; 6-1. Complex curved surface; 6-2. Free ion; 6-3. Crystal ion; 6-4. Spin-left electron; 6-5. Spin-right electron; 6-6. Dislocation line; 6-7. De-charged ion; 6-8. Charged ion; 6-9. Singlet free radical; 6-10. Triplet free radical. Detailed Implementation

[0022] The apparatus of the present invention will be further described below with reference to the accompanying drawings and specific examples.

[0023] like Figure 1 As shown, a micro-grinding device for soft and brittle materials based on magnetostrictive plasticization and vibration damping is characterized in that: the device includes a grinding machine (1), a fixture (2), a magnetic field generating device (3), a motor spindle (4), a slender grinding head (5), and a workpiece (6); the magnetic field generating device (3) is composed of an iron core (3-1), a coil (3-2), a support (3-3), a power supply (3-4), and a wire (3-5); the iron core (3-1) is fixed on the support (3-3), the coil (3-2) and the iron core (3-1) are paired and there are multiple sets, the support (3-3) is fixed on the grinding machine (1), and the power supply (3-4) is connected to the coil (3-2) through the wire (3-5) to form a circuit; the grinding head (5) is composed of a magnetically conductive substrate (5-1), an electroplated layer (5-2), and a superhard abrasive (5-3), and is mounted on the motor spindle (4); the workpiece (6) is a single crystal calcium fluoride (CaF2) material. The micro-blocks of mm×5 mm×3 mm have the characteristics of low hardness and high brittleness. Complex curved surfaces (6-1) need to be machined on the surface of the workpiece (6). The CaF2 workpiece (6) is placed under the grinding head (5). The grinding head (5) is composed of a magnetic substrate (5-1), an electroplated layer (5-2), and superhard abrasive (5-3).

[0024] The CaF2 workpiece (6) is fixed on the fixture (2). The grinding head (5) is aligned with the area to be processed on the CaF2 workpiece (6) by the grinding machine (1). The magnetic field generator (3) is activated, and the coil (3-2) is energized, generating a magnetic field on the surface of the CaF2 workpiece (6) and around the grinding head (5). The grinding head (5) is rotated at high speed by the grinding machine (1) and brought into contact with the surface material of the CaF2 workpiece (6). Figure 5 As shown, at the point where the grinding head (5) just contacts the surface material of the CaF2 workpiece (6), 10 -9 seconds ~10 -7Within seconds, dislocations will occur on the surface material of the CaF2 workpiece (6). The CaF2 ion crystal dislocation line (6-6) contains crystal F with spin-right electrons (6-5) and spin-left electrons (6-4). - (6-3) will be directed towards free Ca 2+ (6-2) When they approach each other, electron transfer occurs, i.e., spin-left electrons (6-4) will transfer to free Ca. 2+ (6-2) At this time, crystal F - (6-3) Transforms into de-energized F - (6-7) Free Ca 2+ (6-2) is converted into electrolytic Ca 2+ (6-8), and the two combine to form a high binding energy singlet free radical (6-9); under the action of a magnetic field, the spin-left electron (6-4) and the spin-right electron (6-5) evolve from opposite directions to the same direction, and the high binding energy singlet free radical (6-9) transforms into a low binding energy triplet free radical (6-10); the free radical binding energy decreases, thereby enhancing the movement of crystal dislocations, and the material removal process of the CaF2 workpiece (6) changes from brittle removal to plastic removal, that is, the magnetostrictive plasticizing effect of the CaF2 workpiece (6). This effect inhibits brittle removal from the root, making the material removal process more stable and continuous, significantly reducing the density of surface defects, and greatly thinning or even eliminating the surface damage layer; in addition, such as Figure 6 As shown, a slender grinding head (5) rotating at high speed feeds outward in a magnetic field and cuts 10 of the magnetic field lines. -3 Within seconds, an upward-directed eddy current (5-4) will be generated inside. This eddy current (5-4) will be subjected to an inward Ampere force in the external magnetic field. That is, the grinding head (5) is subjected to an electromagnetic damping force opposite to its direction of movement. This electromagnetic damping force can partially offset the vibration force of the grinding head (5) during the feeding process, thereby suppressing the vibration of the grinding head (5), i.e., the magnetostrictive vibration suppression effect of the grinding head (5). This effect directly weakens the abnormal contact and impact effect between the grinding head (5) and the CaF2 workpiece (6), effectively improving the dynamic stability and shape retention capability of the grinding head (5), thereby ensuring the smoothness and surface consistency of the processing process. The grinding head (5) that effectively suppresses high-frequency vibration through the magnetostrictive vibration suppression effect, combined with the movement of the grinding machine (1) on the preset processing path, finally produces a complex curved surface (6-1) on the surface of the CaF2 workpiece (6) that has effectively increased the plasticity of the surface material through the magnetostrictive plasticizing effect.

[0025] The specific descriptions of the above examples are only for the purpose of more clearly illustrating the present invention and are not intended to limit the scope of the present invention. Any equivalent substitutions or modifications made within the scope of the disclosure of the present invention are included within the protection scope of the present invention.

Claims

1. A micro-grinding device for soft and brittle materials based on magnetostrictive-vibration-damping energy, characterized in that: The device includes a grinding machine (1), a fixture (2), a magnetic field generator (3), a motor spindle (4), a slender grinding head (5), and a workpiece (6). The magnetic field generator (3) consists of an iron core (3-1), a coil (3-2), a support (3-3), a power supply (3-4), and wires (3-5). The iron core (3-1) is fixed on the support (3-3), and the coils (3-2) and iron core (3-1) are paired and there are multiple sets. The support (3-3) is fixed. On the grinding machine (1), the power supply (3-4) is connected to the coil (3-2) through the wire (3-5) to form a circuit; the grinding head (5) is composed of a magnetically conductive substrate (5-1), an electroplated layer (5-2), and superhard abrasive (5-3), and is mounted on the motor spindle (4); the workpiece (6) is a soft and brittle material, fixed by the fixture (2), and a complex curved surface (6-1) needs to be ground on its surface; at the point where the grinding head (5) and the surface material of the workpiece (6) just come into contact, the grinding head (5) is connected to the coil (3-2) to form a circuit. -9 seconds ~10 -7 Within seconds, dislocations will occur on the surface material of the workpiece (6). Crystal ions (6-3) containing spin-left electrons (6-4) and spin-right electrons (6-5) on the dislocation line (6-6) will approach the free ions (6-2) in the surface material and undergo electron transfer, that is, spin-left electrons (6-4) will transfer to the free ions (6-2). After that, crystal ions (6-3) will become de-energized ions (6-7), and free ions (6-2) will become energized ions (6-8). The energized ions (6-8) will combine with the de-energized ions (6-7) to form a singlet free radical (6-9) with high binding energy. The magnetic field generated by the magnetic field generating device (3) after being energized can cause the spin-right electrons (6-5) to... The rotation direction of the electrons with spin to the left (6-4) becomes consistent, that is, the high binding energy singlet free radical (6-9) is transformed into a low binding energy triplet free radical (6-10); the reduction of the free radical binding energy helps to improve the processing plasticity of the surface material of the workpiece (6), that is, the magnetostrictive plasticizing effect of the workpiece (6); in addition, the magnetic field can also cause the high-speed rotating grinding head (5) to generate eddy currents (5-4) during the feeding process, and the eddy currents (5-4) are further subjected to the Ampere force opposite to the direction of the movement of the grinding head (5) in the external magnetic field, that is, the grinding head (5) is subjected to electromagnetic damping force opposite to the direction of its vibration force, thus reducing the amplitude of the grinding head (5), that is, the magnetostrictive vibration suppression effect of the grinding head (5).

2. The magnetostrictive-vibration-damping micro-grinding device for soft and brittle materials according to claim 1, characterized in that: The iron core (3-1) is made of soft magnetic material with a relative permeability ≥500; the coil (3-2) is wound on the corresponding iron core (3-1), and there are a total of 6 sets of coils (3-2) connected in series. The first end of the first coil (3-2) and the last end of the last coil (3-2) are respectively connected to the positive and negative poles of the power supply (3-4); the winding directions of adjacent coils (3-2) are opposite, so that the polarities of adjacent iron cores (3-1) are opposite, so as to form a closed magnetic circuit passing through the workpiece (6) and the grinding head (5); the power supply (3-4) that supplies power to the magnetic field generating device (3) is an AC power supply, the current is adjustable from 0 to 10 A, the voltage is adjustable from 0 to 60 V, and the magnetic field generating device (3) can be controlled to generate a uniform alternating magnetic field with an adjustable magnetic field strength from 0 to 200 mT.

3. The magnetostrictive-vibration-damping micro-grinding device for soft and brittle materials according to claim 1, characterized in that: The working part of the grinding head (5) is needle-shaped, spherical, disc-shaped, or columnar, with a radial dimension ranging from 0.02 to 1 mm and an aspect ratio ≥ 5. The substrate (5-1) is made of a ferromagnetic material with a relative permeability ≥ 200. The electroplated layer (5-2) and the superhard abrasive (5-3) cover all or part of the working surface of the grinding head (5). The superhard abrasive (5-3) is diamond or CBN, with a particle size ranging from 1 to 50 μm.

4. The magnetostrictive-vibration-damping micro-grinding device for soft and brittle materials according to claim 1, characterized in that: The workpiece (6) is made of soft and brittle materials such as calcium fluoride, zinc selenide, zinc cadmium telluride, and potassium dihydrogen phosphate.

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