A magnetic field-assisted shear thickening tool polishing device and polishing method

Abstract

This invention discloses a magnetic field-assisted shear thickening tool polishing device, comprising a polishing tank containing a magnetic thickening fluid, an excitation mechanism connected to the polishing tank, a polishing cylinder inside the polishing tank, and the excitation mechanism sleeved outside the polishing cylinder. The polishing tank and polishing cylinder are connected and used for the inflow and outflow of the magnetic thickening fluid. A tool immersed in the magnetic thickening fluid is placed inside the polishing cylinder, and the high-speed rotation of the tool causes the magnetic thickening fluid to circulate along the gap between the polishing cylinder and the tool surface under the action of the magnetic field of the excitation mechanism. This invention also discloses its polishing method. Through the high-speed rotation of the tool inside the polishing cylinder, the magnetic thickening fluid generates a certain shear rate at the gap between the tool and the polishing cylinder, allowing the magnetic thickening fluid to circulate. Under the action of the magnetic field, the viscosity of the magnetic thickening fluid increases, resulting in high shear force rubbing against the tool surface, thereby achieving the effect of flexible polishing and edge blunting of the tool through high-speed rotation in the magnetic thickening fluid.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology for cutting tools, and specifically to a tool polishing device and method for magnetic field-assisted shearing thickening. Background Technology

[0002] With the development of science and technology, people's requirements for the precision of manufacturing processes are gradually increasing, which also places higher demands on machining tools. Tools need to undergo surface polishing and cutting edge dressing to improve the surface quality of the tools, remove cracks and nicks on the cutting edge, enhance the cutting performance of the tools, and extend their service life. Carbide drilling tools are commonly used hole-making tools in mechanical manufacturing. Their surfaces and cutting edge shapes are relatively complex, making it difficult to perform integrated and efficient machining. Moreover, carbide has high hardness, and the surface grinding and polishing quality of the tools cannot meet the requirements, resulting in poor surface quality uniformity and low machining efficiency, making it difficult to meet the requirements of high-end tools.

[0003] Currently, the main methods for polishing and dulling cutting edges of cutting tools include: grinding wheel grinding, electrochemical polishing, abrasive flow polishing, and drag polishing. Among these, grinding wheel grinding is unsuitable for polishing complex curved surfaces, and the ground cutting edge is prone to defects; electrochemical polishing has difficulty guaranteeing processing stability, and stray corrosion may occur on the tool surface; abrasive flow polishing requires specialized fixtures, making tool installation and disassembly complex and resulting in low polishing efficiency. Currently, mechanical grinding methods are used for polishing curved tool surfaces in China. For large-sized tools, polishing is generally achieved by grinding and polishing along the spiral grooves of the tool using a polishing wheel with fluid abrasive. For small-sized tools, solid abrasive is directly inserted, and drag polishing of the curved surface is achieved through high-speed rotation of the tool. This method is more intense and efficient, but the quality of the cutting edge is difficult to guarantee. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a tool polishing device and method with magnetic field-assisted shearing thickening, which has good adaptability to tool shape and high chip material removal rate.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A magnetic field-assisted shear thickening tool polishing device includes a polishing tank containing a magnetic thickening fluid, an excitation mechanism and a polishing cylinder inside the polishing tank, the excitation mechanism being sleeved on the outside of the polishing cylinder, the polishing tank being connected to the polishing cylinder and used for the inflow and outflow of the magnetic thickening fluid, and a tool immersed in the magnetic thickening fluid inside the polishing cylinder, the high-speed rotation of the tool causing the magnetic thickening fluid to circulate along the gap between the polishing cylinder and the tool surface under the action of the magnetic field of the excitation mechanism.

[0007] Furthermore, the polishing cylinder is vertically positioned at the center of the polishing tank, and the cutting tool extends from the top of the inner hole of the polishing cylinder to the bottom of the inner hole of the polishing cylinder, with the bottom of the inner hole of the polishing cylinder communicating with the polishing tank.

[0008] Furthermore, the polishing tank is provided with a plurality of connecting pipes that communicate with the polishing cylinder, and the plurality of connecting pipes are evenly distributed radially along the radial direction of the polishing cylinder.

[0009] Furthermore, the bottom of the polishing tank is provided with multiple threaded holes that run vertically through it, and the annular groove is fixedly connected to each threaded hole by fixing bolts.

[0010] Furthermore, the polishing tank, polishing cylinder, and cutting tool are all made of non-magnetic materials.

[0011] Furthermore, the excitation mechanism generates a magnetic field along the radial direction of the polishing cylinder.

[0012] Furthermore, the polishing groove is connected to an annular groove, and an installation cylinder is provided at the center of the annular groove. The excitation mechanism is located in the annular groove and sleeved on the outside of the installation cylinder. The polishing cylinder is connected to the installation cylinder. A pressure cover is provided on the annular groove to seal and wrap the excitation mechanism.

[0013] Furthermore, the polishing cylinder and the mounting cylinder are detachably fitted with a clearance.

[0014] Furthermore, the pressure cap is provided with a concave groove, and the annular inner wall of the concave groove is fitted with the annular outer wall of the annular groove in an interference fit manner.

[0015] A method for polishing a tool with magnetic field-assisted shear thickening includes the following steps:

[0016] Step 1: Preparation of magnetic thickening fluid: Starch and deionized water are stirred and mixed, then carbonyl iron powder, diamond abrasive particles and dispersant are added, stirred and mixed and ultrasonically dispersed, and then placed in a vacuum drying oven for h to obtain magnetic thickening fluid;

[0017] Step 2, Pre-treatment of tool surface corrosion: Immerse the tool part in hydrogen peroxide solution to corrode and soften its surface, then take it out, rinse and dry it;

[0018] Step 3: Polish the surface of the tool: Install the tool treated in step 3 on the drive device and insert the tool into the polishing cylinder. Then pour the magnetic thickening fluid prepared in step 3 into the polishing tank and start the drive device to make the tool rotate at high speed so that the surface of the tool is polished.

[0019] Step 4: Perform surface roughness testing on the cutting tool.

[0020] Furthermore, in step 1, the mass fraction of starch and deionized water is 51:49, and the mass fraction of carbonyl iron powder, diamond abrasive particles and dispersant is 5:10:0.2.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] The polishing device of this invention utilizes the high-speed rotation of the cutting tool within the polishing cylinder. A magnetically thickened fluid generates a certain shear rate at the gap between the cutting tool and the polishing cylinder, causing the fluid to flow along the gap across the surface of the cutting tool. Since the polishing cylinder is connected to the polishing tank, the magnetically thickened fluid can enter the polishing cylinder from the polishing tank and flow back into the polishing tank, thus achieving cyclic flow. Furthermore, the magnetic field exerted by the excitation mechanism on the magnetically thickened fluid within the polishing cylinder induces magnetorheological and shear-thickening rheological properties in the fluid, increasing its viscosity. This causes the fluid to slide against the cutting tool surface with high shear force. Through the characteristics of the cutting tool's spiral groove structure, the pumping effect generated by its rotation achieves the cyclic flow of the magnetically thickened fluid, thereby renewing the abrasive grains on the cutting tool surface and removing chips and cutting heat. Combining the controllability of magnetorheology with the adaptability of shear thickening, the device achieves the effect of flexible polishing and edge passivation through high-speed rotation of the cutting tool within the magnetically thickened fluid. Simultaneously, it can also trim and passivate the cutting edge, improving the cutting performance and service life of the cutting tool. Furthermore, due to the self-adaptability of the magnetic shear thickening fluid, the positioning accuracy requirements during the polishing process are not high, and the tool clamping and disassembly are convenient.

[0023] The polishing method of this invention addresses the characteristics of high hardness and difficult machining of cemented carbide cutting tools. During the polishing process, hydrogen peroxide solution is used to pre-treat the tool surface for corrosion. Then, a magnetic field is used to enhance the shear thickening effect. The magnetic thickening fluid in the polishing area has a high viscosity, and the abrasive particles in the magnetic thickening fluid are trapped by carbonyl iron powder and polyhydroxy polymer, sliding against the tool surface with high shear force to remove the cutting material from the tool surface. This method has good adaptability to tool shape and a high cutting material removal rate. Attached Figure Description

[0024] Figure 1 A cross-sectional schematic diagram of a tool polishing device for magnetic field-assisted shear thickening.

[0025] Figure 2 A top view of the tool polishing device for magnetic field-assisted shear thickening.

[0026] Legend:

[0027] 1. Polishing tank; 11. Magnetic thickening fluid; 12. Fixing bolt; 2. Excitation mechanism; 3. Polishing cylinder; 31. Connecting pipe; 4. Cutting tool; 5. Annular groove; 51. Mounting cylinder; 52. Pressure cap; 521. Concave groove. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 and Figure 2 As shown, the magnetic field-assisted shear thickening tool polishing device of this embodiment includes a polishing tank 1 containing a magnetic thickening fluid 11. The polishing tank 1 is provided with an excitation mechanism 2 and a polishing cylinder 3. The excitation mechanism 2 is sleeved on the outside of the polishing cylinder 3. The polishing tank 1 is connected to the polishing cylinder 3 and is used for the inflow and outflow of the magnetic thickening fluid 11. The polishing cylinder 3 is provided with a tool 4 immersed in the magnetic thickening fluid 11. The high-speed rotation of the tool 4 causes the magnetic thickening fluid 11 to circulate along the gap between the polishing cylinder 3 and the tool 4 under the action of the magnetic field of the excitation mechanism 2, passing over the surface of the tool 4. The high-speed rotation of the cutter 4 within the polishing cylinder 3 generates a certain shear rate in the gap between the cutter 4 and the polishing cylinder 3, causing the magnetic thickening fluid 11 to flow along the gap across the surface of the cutter 4. Since the polishing cylinder 3 is connected to the polishing tank 1, the magnetic thickening fluid 11 can enter the polishing cylinder 3 from the polishing tank 1 and flow back into the polishing tank 1, thus achieving cyclic flow. Furthermore, the magnetic field exerted by the excitation mechanism 2 on the magnetic thickening fluid 11 located in the polishing cylinder 3 induces magnetorheological and shear thickening in the magnetic thickening fluid 11. Due to its rheological properties, the viscosity of the magnetic thickening fluid 11 increases, causing it to slide against the surface of the tool 4 with high shear force. Utilizing the characteristics of the spiral groove structure of the tool 4, the pumping effect generated by its rotation achieves the circulation of the magnetic thickening fluid 11, thereby renewing the abrasive grains on the surface of the tool 4 and carrying away chips and cutting heat. Combining the controllability of magnetorheology with the adaptability of shear thickening, the tool 4 achieves flexible polishing and edge passivation through high-speed rotation in the magnetic thickening fluid 11. Simultaneously, it can also trim and passivate the tool edge, improving the cutting performance and service life of the tool 4. Furthermore, due to the adaptability of the magnetic shear thickening fluid, the positioning accuracy requirements during the polishing process are not high, and the tool 4 is easy to clamp and disassemble.

[0030] In this embodiment, the polishing cylinder 3 is vertically positioned at the center of the polishing tank 1, and the cutting tool 4 extends from the top of the inner hole of the polishing cylinder 3 to the bottom of the inner hole of the polishing cylinder 3. The bottom of the inner hole of the polishing cylinder 3 is connected to the polishing tank 1. The inner diameter of the polishing cylinder 3 is 0.5-1 mm larger than the outer diameter of the cutting tool 4, and its length is 10-15 mm shorter than that of the mounting cylinder 51, leaving space for the cutting tool 4. The polishing cylinder 3 has a length of 30 mm, an inner diameter of 11 mm, and an outer diameter of 18 mm. Within this polishing gap range, when the shear rate of the magnetic thickening fluid 11 reaches the shear thickening range, the rapid dissipation of shear force can be avoided.

[0031] In this embodiment, the polishing tank 1 is provided with multiple connecting pipes 31 that communicate with the polishing cylinder 3. The multiple connecting pipes 31 are evenly distributed radially along the radial direction of the polishing cylinder 3. The polishing tank 1 is provided with four mutually perpendicular rectangular through grooves in a cross shape. The grooves are 10mm deep and 20mm wide, allowing the magnetic thickening fluid 11 to flow from the polishing tank 1 into the polishing cylinder 3 and then flow back from the top of the polishing cylinder 3 into the polishing tank 1. This not only realizes the flow of the magnetic thickening fluid 11 in the polishing cylinder 3, carrying away the chips and heat generated by collision and friction in the polishing area, but also realizes the circulation of the magnetic thickening fluid 11, thereby reducing the amount of magnetic thickening fluid 11 used and miniaturizing the polishing device.

[0032] In this embodiment, the bottom of the polishing tank 1 is provided with multiple threaded holes that extend vertically. The annular groove 5 is fixedly connected to each threaded hole by fixing bolts 12. The fixing bolts 12 facilitate the fixing of the annular groove 5. The bottom plate of the polishing tank 1 has four M12 threaded holes in the center. When discharging polishing liquid and cleaning device, it is not necessary to tilt the tank. Simply remove the support fixing bolts and the support to allow the magnetic thickening fluid 11 to drain from the bottom threaded holes. This facilitates the replacement of the magnetic thickening fluid 11 and the cleaning of the polishing tank 1.

[0033] In this embodiment, the polishing tank 1, polishing cylinder 3, and cutting tool 4 are all made of non-magnetic materials. The cutting tool 4 can be a YT8 twist drill with a diameter of φ10mm. The cutting tool 4 is made of non-magnetic materials such as cemented carbide or weakly magnetic materials, so that the cutting tool 4 will not be magnetized by the magnetic field, and the surface of the cutting tool 4 will not be coated with carbonyl iron powder in the magnetic thickening fluid 11, resulting in poor polishing effect. The clamps in the polishing tank 1, polishing cylinder 3, annular groove 5, pressure cap 52, and excitation mechanism 2 are made of non-magnetic materials such as stainless steel, so as to avoid the main components affecting the magnitude and uniformity of the magnetic field in the polishing area, and ensure that the components in the magnetic thickening fluid 11 are evenly distributed and the rheological properties are stable.

[0034] In this embodiment, the excitation mechanism 2 forms a magnetic field along the radial direction of the polishing cylinder 3. The excitation mechanism 2 includes a clamp and magnets, which can be electromagnets or permanent magnets. The magnetic induction intensity on the surface area of ​​the tool 4 is in the range of 30-40 mT, while the magnetic field intensity around the excitation mechanism 2 is less than 10 mT. The clamp is 3D printed and is a ring-shaped cylinder with an inner diameter of 30 mm and an outer diameter of 80 mm. Square through holes are opened at 45° intervals along the radial direction of the tool on the clamp, and the magnets are bonded and fixed in the square through holes with industrial AB glue to avoid jumping between the magnets due to large attraction / repulsion forces. Ten permanent magnets are used, arranged along the spiral direction of the tool 4. The blades NN are arranged in parallel and symmetrically. Due to the magnetic field, the carbonyl iron powder in the magnetic thickening fluid 11 is polarized into chains, and the direction is perpendicular to the rotation direction of the blade 4. This increases the shear thickening of the magnetic thickening fluid 11 and increases the viscosity of the magnetic thickening fluid 11. This allows the clusters to carry abrasive particles and remove the surface material of the blade 4 with greater shear force. Meanwhile, the magnetic thickening fluid 11 outside the periphery of the excitation mechanism 2 is not affected by the magnetic field and maintains good fluidity with low shear rate and low viscosity to achieve repeated polishing effect.

[0035] In this embodiment, an annular groove 5 is connected inside the polishing tank 1. A mounting cylinder 51 is provided at the center of the annular groove 5. The excitation mechanism 2 is located inside the annular groove 5 and sleeved on the outside of the mounting cylinder 51. The polishing cylinder 3 is connected inside the mounting cylinder 51. A pressure cap 52 is provided on the annular groove 5 to seal and enclose the excitation mechanism 2. The annular groove 5 is used to install the excitation mechanism 2 and can effectively position the polishing cylinder 3.

[0036] In this embodiment, the polishing cylinder 3 and the mounting cylinder 51 are detachably fitted with a clearance. The polishing cylinder 3 is fixedly installed in the mounting hole on the inner wall of the mounting cylinder 51 by screws, allowing for easy replacement of polishing cylinders 3 with different inner diameters, thereby adjusting the polishing clearance.

[0037] In this embodiment, the pressure cap 52 is provided with a concave groove 521, and the annular inner wall of the concave groove 521 is fitted with the annular outer wall of the annular groove 5 in an interference fit manner. The interference fit makes it less likely to fall off, making the sealing of the cavity in the annular groove 5 more reliable, and preventing polishing fluid from entering the cavity of the annular groove 5 and contaminating the cavity of the excitation mechanism 2, making the excitation mechanism 2 difficult to clean and remove.

[0038] A method for polishing a tool with magnetic field-assisted shear thickening includes the following steps:

[0039] Step 1: Preparation of magnetic thickening fluid 11: Starch and deionized water are stirred and mixed, then carbonyl iron powder, diamond abrasive particles and dispersant are added, stirred and mixed and ultrasonically dispersed, and then placed in a vacuum drying oven for 1 hour to obtain magnetic thickening fluid 11.

[0040] Step 2, corrosion pretreatment of tool 4 surface: Immerse tool 4 in hydrogen peroxide solution to corrode and soften its surface, then remove, rinse and dry; avoid residual hydrogen peroxide solution from chemically reacting with the components in the magnetic shear thickening fluid, affecting the rheological properties of the polishing fluid;

[0041] Step 3: Polish the surface of the tool 4: Install the tool 4 treated in step 2 on the drive device and insert the tool 4 into the polishing cylinder 3. Then pour the magnetic thickening fluid 11 prepared in step 1 into the polishing tank 1 and start the drive device to make the tool 4 rotate at high speed so that the surface of the tool 4 is polished.

[0042] Step 4: Surface roughness inspection of tool 4. Tool 4 rotates at 3000-5000 rpm. The shear rate of the magnetic thickening fluid 11 is in the thickening high viscosity range, forming a flexible yet high shear force on tool 4 within the polishing gap. Considering the high hardness and difficult machining characteristics of the cemented carbide tool 4, during polishing, hydrogen peroxide solution is used for corrosion pretreatment of the tool 4 surface. Then, a magnetic field is used to enhance the shear thickening effect. The magnetic thickening fluid 11 in the polishing area has high viscosity. The abrasive particles in the magnetic thickening fluid 11 are held by carbonyl iron powder and polyhydroxy polymer, sliding against the surface of tool 4 with high shear force, thus removing the cutting material from the surface of tool 4. This method has good adaptability to the shape of tool 4 and a high cutting material removal rate.

[0043] In this embodiment, the mass fraction of starch and deionized water in step 1 is 51:49, and the mass fraction of carbonyl iron powder, diamond abrasive particles, and dispersant is 5:10:0.2. The stirring and mixing time is 30 min, the dispersant is sodium polyacrylate or polyethylene glycol, the ultrasonic dispersion time is 30 min, and the standing time is 1 h.

[0044] In this embodiment, the concentration of hydrogen peroxide solution in step 2 is 30%, and the soaking time is 2 hours. This effectively corrodes and softens the surface of the tool 4 without causing excessive corrosion.

[0045] In this embodiment, in step 4, a surface profilometer is used to detect the roughness of the outer circular surface and the cutting edge surface of the tool 4. The surface roughness of the outer circular surface of the tool 4 should be reduced from about 370nm to about 25nm, and the roughness of the cutting edge surface should be reduced from about 500nm to about 190nm. In addition, a laser focusing microscope is used to scan the cutting edge shape of the tool 4. Its cutting edge passivation radius should reach 12μm, and its cutting edge defects should be basically removed.

[0046] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the inventive concept should also be considered within the scope of protection of the present invention.

Claims

1. A magnetic field assisted shear thickening tool polishing apparatus, characterized by, The application relates to a polishing tank (1) containing magnetic thickening fluid (11), wherein the polishing tank (1) is internally provided with an excitation mechanism (2) and a polishing cylinder (3), the excitation mechanism (2) is sleeved outside the polishing cylinder (3), the polishing tank (1) is communicated with the polishing cylinder (3) and is used for the inflow and outflow of the magnetic thickening fluid (11), the polishing cylinder (3) is internally provided with a cutter (4) immersed in the magnetic thickening fluid (11) and the cutter (4) is rotated at high speed to make the magnetic thickening fluid (11) circulate along the gap between the polishing cylinder (3) and the cutter (4) and flow through the surface of the cutter (4) under the action of the magnetic field of the excitation mechanism (2), the polishing cylinder (3) is vertically arranged at the center of the polishing tank (1), the cutter (4) extends from the top of the inner hole of the polishing cylinder (3) to the bottom of the inner hole of the polishing cylinder (3), the bottom of the inner hole of the polishing cylinder (3) is communicated with the polishing tank (1), the polishing tank (1) is internally provided with a plurality of communication pipes (31) communicated with the polishing cylinder (3), the plurality of communication pipes (31) are uniformly distributed along the radial direction of the polishing cylinder (3) in a radial manner, the bottom of the polishing tank (1) is provided with a plurality of threaded holes penetrating up and down, the polishing tank (1) is internally connected with an annular groove (5), the annular groove (5) is fixedly connected with each threaded hole through fixing bolts (12), the center of the annular groove (5) is provided with a mounting cylinder (51), the excitation mechanism (2) is arranged in the annular groove (5) and is sleeved outside the mounting cylinder (51), the polishing cylinder (3) is connected in the mounting cylinder (51), the annular groove (5) is provided with a gland (52) sealingly wrapping the excitation mechanism (2), the polishing cylinder (3) and the mounting cylinder (51) are gap-connected in a detachable manner, the gland (52) is provided with a concave groove (521), and the annular inner wall of the concave groove (521) is sleeved with the annular outer wall of the annular groove (5) in an interference fit manner.

2. The magnetic field-assisted shear thickening tool polishing apparatus of claim 1, wherein, The polishing tank (1), the polishing cylinder (3) and the cutter (4) are all made of non-magnetic conductive material.

3. The magnetic field-assisted shear thickening tool polishing apparatus of claim 1, wherein, The excitation mechanism (2) forms a magnetic field along the radial direction of the polishing cylinder (3).

4. A magnetic field assisted shear thickening tool polishing method as claimed in any one of claims 1-3, characterized in that, The application further discloses a preparation method of the polishing tank (1), the polishing cylinder (3) and the cutter (4). Step 1: preparing the magnetic thickening fluid (11): stirring and mixing starch and deionized water, then adding carbonyl iron powder, diamond abrasive particles and a dispersing agent, stirring and mixing and ultrasonic dispersion, and then standing in a vacuum drying box for 1h to obtain the magnetic thickening fluid (11); Step 2: corrosion pretreatment of the surface of the cutter (4): partially immersing the cutter (4) in a hydrogen peroxide solution to corrode and soften the surface of the cutter (4), then taking out, rinsing and drying; Step 3: polishing treatment of the surface of the cutter (4): installing the cutter (4) treated in step 2 on a driving device, inserting the cutter (4) into the polishing cylinder (3), then pouring the magnetic thickening fluid (11) prepared in step 1 into the polishing tank (1), and starting the driving device to rotate the cutter (4) at high speed to polish the surface of the cutter (4); Step 4: detecting the roughness of the surface of the cutter (4).

5. The magnetic field-assisted shear thickening tool polishing method according to claim 4, characterized in that, The mass fraction of starch and deionized water in step 1 is 51:49, and the mass fraction of carbonyl iron powder, diamond abrasive particles and dispersant is 5:10:0.2.

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