Binder jet 3D printing forming method for porous diamond grinding wheel and obtained porous diamond grinding wheel

Abstract

The invention discloses a binder jet 3D printing forming method for a porous diamond grinding wheel and the obtained porous diamond grinding wheel. The binder jet 3D printing forming method comprises the steps that a frame structure of the diamond grinding wheel is designed; spraying the binder to form a frame structure green body: mixing the diamond abrasive and the filler to obtain mixed powder; the frame structure green body is filled with the mixed powder, and vibration compaction is conducted; the green body filled with the powder is put into an atmosphere furnace to be pre-sintered; the presintered brown part is put into a vacuum furnace for bronze infiltration treatment; impurities attached to the surface of the grinding wheel are removed, then the grinding wheel is dressed, and the diamond abrasive is exposed. According to the forming method, customization of the geometric shape and the internal pores of the grinding wheel can be achieved without consuming a large amount of computing power, the grinding wheel tissue, the pore diameter, the pore distribution and the like can be adjusted and controlled by adjusting and controlling technological parameters through a part formed by applying binder injection additive manufacturing to be matched with infiltration, and the prepared grinding wheel has higher pertinence.

Description

Technical Field

[0001] The present invention belongs to the technical field of grinding and 3D printing, and more specifically, relates to a binder jet 3D printing forming method for a porous diamond grinding wheel and the obtained porous diamond grinding wheel. Background Art

[0002] The existing grinding wheels on the market are usually made by mixing abrasive powder and binder powder in a certain proportion, putting them into a mold for pressing, and then undergoing high-temperature sintering and other treatments to obtain the final product. Metal bond diamond grinding wheels have the advantages of strong abrasive holding force, good bonding strength, good wear resistance, long service life and the ability to withstand large grinding forces. Therefore, they have broad application prospects and are one of the options for achieving high-speed precision grinding.

[0003] Traditional metal bond grinding wheels are limited by the molding process, and their internal porosity and pore size are very small, resulting in poor self-sharpening of the grinding wheel. In addition, their chip holding space is limited, and debris is easily accumulated on the surface, further reducing the cooling performance of the grinding wheel. This can easily cause burns on the workpiece surface, making it difficult to obtain excellent processing quality.

[0004] In recent years, with the development of additive manufacturing technology, technical solutions for additive manufacturing of porous grinding wheels have emerged, mainly based on laser selective melting technology. With the unique advantages of additive manufacturing, it is possible to prepare grinding wheels with internal porous structures, so the disadvantages of low porosity and small chip space can be overcome to a certain extent. However, there are still some urgent problems to be solved in laser selective melting of porous metal-bonded diamond grinding wheels. For example, all kinds of pores of different sizes inside the grinding wheel need to be generated through three-dimensional modeling, especially when the structure of the grinding wheel is complex, which will consume a lot of computing power; in addition, the use of laser selective melting molding also has special requirements for the selection of metal binders. For example, when the melting point of the metal binder is high, high-energy lasers will cause severe carbonization of diamonds, affecting their physical properties. When using some materials with high reflectivity, it will affect the laser energy absorption efficiency, thereby affecting the forming performance of the parts. Summary of the invention

[0005] In response to the need for improvement in the prior art, the present invention provides a method for forming a porous metal-based bond diamond grinding wheel segment based on binder jetting additive manufacturing and a porous diamond grinding wheel obtained. The present invention can simultaneously realize the random generation and on-demand generation of internal pores of the metal-based bond diamond grinding wheel without consuming a lot of computing power, improve the chip removal and heat dissipation problems of the grinding wheel during the processing, and at the same time expand the selection range of metal bonds to achieve customized forming of grinding wheels for processing targets.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a binder jet 3D printing method for a porous diamond grinding wheel, comprising:

[0008] Step 1, design the frame structure of the diamond grinding wheel;

[0009] Step 2, spraying a binder to form a green body of the frame structure;

[0010] Step 3, mixing the diamond abrasive and the filler to obtain a mixed powder;

[0011] Step 4: Fill the mixed powder into the frame structure green body, and then place the green body filled with powder on a vibration platform for compaction;

[0012] Step 5, placing the green body filled with powder into an atmosphere furnace for pre-sintering;

[0013] Step 6: Place the pre-sintered brown parts into a vacuum furnace for bronze infiltration treatment;

[0014] Step 7: Remove impurities attached to the surface of the grinding wheel, and then dress the grinding wheel to expose the diamond abrasive.

[0015] As a further technical solution, the frame structure in step 1 comprises a porous structure frame, a layer of skin is covered on the periphery of the porous structure frame, and a powder filling port is retained on the skin.

[0016] As a further technical solution, in step 2, the metal powder material used for printing the frame structure is selected according to the required structural strength of the grinding wheel and the processing object, and the frame structure green body is formed using a binder jet additive manufacturing method.

[0017] As a further technical solution, in the step 3, the diamond abrasive and filler are weighed according to the required weight ratio and placed in a mixing container; stainless steel grinding balls of different sizes are added to the mixed powder in a weight ratio of 1:1, and mixed in a three-dimensional powder mixer until the mixture is uniform without obvious component segregation.

[0018] As a further technical solution, in step 4, the compaction of the mixed powder is controlled by controlling the vibration time and power.

[0019] As a further technical solution, in step 5, the pre-sintering temperature is much lower than the melting point of the metal.

[0020] As a further technical solution, in step 7, if there is a skin structure on the working surface of the grinding wheel, it is removed together when the grinding wheel is dressed.

[0021] As a further technical solution, according to GB / T6409.1-1994, the grinding wheel segment contains 0.88 grams of diamond abrasive grains per cubic centimeter of volume, which is defined as 100% of the grinding tool concentration. According to the structural design parameters of the grinding wheel segment and the grinding wheel grinding tool concentration design requirements, the calculation formula for the amount of diamond abrasive, filler and bronze is as follows:

[0022] M 金刚石 =C 砂轮 ×V 砂轮 / 1cm 3 ×0.88g

[0023] M 填料 =D1×ρ 填料 ×(V 砂轮 ×P 框架 -M 金刚石 / (D1×ρ 金刚石 ))

[0024] M 青铜 =ρ 青铜 ×(V 砂轮 ×P 框架 ×(1-D1)+V 砂轮 ×(1-P 框架 )×(1-D2))

[0025] Among them, M 金刚石 is the amount of diamond powder, M 填料 is the required amount of filler, M 青铜 is the amount of bronze required for infiltration, ρ 填料 is the density of the filler material, ρ 金刚石 is the density of diamond, ρ 青铜 is the density of bronze, C 砂轮 is the abrasive concentration of the set grinding wheel, V 砂轮 is the volume of the grinding wheel, P 框架 is the porosity of the frame structure formed by binder jetting, excluding the internal porosity of the printed part, D1 is the packing density of the mixed powder of diamond and filler, and D2 is the relative density of the frame part printed by binder jetting.

[0026] In a second aspect, the present invention discloses a porous diamond grinding wheel, which is obtained by the binder jet 3D printing forming method.

[0027] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0028] 1. The porous diamond grinding wheel forming method of the present invention is based on binder jet additive manufacturing, which is inherently suitable for forming porous materials. By controlling the sintering temperature and time, pores can be naturally formed in the parts. Therefore, this technology can be used to customize the geometric shape and internal pores of the grinding wheel without consuming a lot of computing power. When larger pores are required in the grinding wheel, pores designed on demand can be added to the grinding wheel by adjusting the design of the frame structure, so only the pores designed on demand need to consume part of the computer computing power. In addition, the parts formed by binder jet additive manufacturing in combination with melt infiltration can achieve the regulation of grinding wheel structure, pore diameter, pore distribution, etc. by adjusting process parameters, and the prepared grinding wheel has stronger pertinence.

[0029] 2. The porous diamond grinding wheel filler in the process method of the present invention can be selected as needed, and with the corresponding forming process parameters, the holding force of the abrasive can be controlled, and the functionality of special materials can be further provided. The mechanical strength of the grinding wheel can be adjusted by controlling the sintering process of the filler and the bronze infiltration process.

[0030] 3. The pre-sintering and infiltration temperatures in the process of the present invention are much lower than the molten pool temperature of laser additive manufacturing, so the thermal damage to diamond abrasives is smaller. The grinding wheel finally obtains mechanical strength by infiltration, and the selection of metal binders is much less restricted than laser additive manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention is further described below in conjunction with the accompanying drawings:

[0032] Figure 1 The present invention is a schematic diagram of the process of forming a porous diamond grinding wheel by binder injection.

[0033] Figure 2 It is a structural design diagram of the porous diamond grinding wheel formed by binder injection molding of the present invention.

[0034] Specifically, they are: 1. Skin, 2. Porous structure frame.

[0035] Figure 3 This is an electron microscope image of the polished surface of the porous diamond grinding wheel formed by binder injection of the present invention. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof;

[0038] As described in the background technology, the shortcomings of the prior art exist. In order to solve the above technical problems, the present invention proposes a binder jet 3D printing forming method of a porous diamond grinding wheel, comprising:

[0039] Step 1, design the framework structure: according to the required porosity, pore size, pore distribution, structural strength and geometric shape of the grinding wheel, design the internally connected porous structure framework 2. Cover the porous structure framework 2 with a very thin skin 1, and retain the powder filling port in one direction. The function of the skin 1 is to ensure that when the powder is filled into the framework structure, the powder can fully fill the porous structure without outflow. If there is a skin structure on the working surface of the grinding wheel, it can be removed when the grinding wheel is dressed.

[0040] Step 2: Binder jetting to form the green body of the frame structure: Select the metal powder material used to print the frame structure according to the required structural strength of the grinding wheel and the processing object, and use the binder jetting additive manufacturing method to form the green body of the frame structure. By taking advantage of the binder jetting additive manufacturing in forming porous materials, the porosity of the frame structure itself can be achieved, which is more conducive to the subsequent infiltration treatment.

[0041] Step 3: Mix the powder raw materials: The powder raw materials are divided into diamond abrasive and filler. Weigh the diamond abrasive and filler according to the required weight ratio and put them into a mixing container. Diamond abrasive is mainly used to remove materials; filler is used to hold diamond particles and provide overall mechanical properties of the grinding wheel.

[0042] Stainless steel grinding balls of different sizes are added to the mixed powder in a weight ratio of 1:1, and mixed in a three-dimensional powder mixer until the mixture is uniform without obvious component segregation.

[0043] Step 4: Fill the frame structure: Fill the mixed powder into the frame structure green body, and then place the green body filled with powder on the vibration platform for compaction. Control the vibration time and power to prevent powder component segregation.

[0044] Step 5, pre-sintering: The green body filled with powder is placed in an atmosphere furnace for two-stage pre-sintering, the purpose of which is to remove the binder in the green body and at the same time give the green body a certain mechanical strength to ensure that the printed structure will not be damaged during infiltration. The pre-sintering temperature can be much lower than the melting point of the metal, so the high-temperature carbonization of the diamond particles can be minimized, which is conducive to maintaining the mechanical properties of the diamond particles.

[0045] Step 6, Infiltration: Place the pre-sintered brown parts into a vacuum furnace for bronze infiltration. The temperature of bronze infiltration is relatively low, which can minimize the high-temperature carbonization of diamond particles. At the same time, bronze is the most commonly used metal binder for diamond tools, which can give the grinding wheel sufficient mechanical strength and stronger diamond holding force.

[0046] Step 7, post-processing: remove impurities attached to the surface of the grinding wheel, and then perform grinding wheel dressing to expose the diamond abrasive.

[0047] The above-mentioned porous diamond grinding wheel forming method can realize the customization of the grinding wheel geometry and internal pores without consuming a lot of computing power. The pores are divided into pores designed on demand and pores naturally generated during the forming process. Only the designed pores require computer computing power. In addition, the parts formed by binder jet additive manufacturing combined with melt infiltration can achieve the control of grinding wheel structure, pore diameter, pore distribution, etc. by adjusting process parameters, and the prepared grinding wheel has stronger pertinence.

[0048] Further, according to GB / T6409.1-1994, the grinding wheel segment contains 0.88 grams of diamond abrasive grains per cubic centimeter of volume, which is defined as 100% of the grinding tool concentration. According to the structural design parameters of the grinding wheel segment and the grinding wheel grinding tool concentration design requirements, the calculation formula for the amount of diamond, filler and bronze is as follows:

[0049] M 金刚石 =C 砂轮 ×V 砂轮 / 1cm 3 ×0.88g

[0050] M 填料 =D1×ρ 填料 ×(V 砂轮 ×P 框架 -M 金刚石 / (D1×ρ 金刚石 ))

[0051] M 青铜 =ρ 青铜 ×(V 砂轮 ×P 框架 ×(1-D1)+V 砂轮 ×(1-P 框架 )×(1-D2))

[0052] Among them, M 金刚石 is the amount of diamond powder, M 填料 is the required amount of filler, M 青铜 is the amount of bronze required for infiltration, ρ 填料 is the density of the filler material, ρ 金刚石 is the density of diamond, ρ 青铜 is the density of bronze, C 砂轮 is the abrasive concentration of the set grinding wheel, V 砂轮 is the volume of the grinding wheel, P 框架 is the porosity of the frame structure formed by binder jetting, excluding the internal porosity of the printed part, D1 is the packing density of the mixed powder of diamond and filler, and D2 is the relative density of the frame part printed by binder jetting.

[0053] The porous diamond grinding wheel filler of the present invention can be selected as needed, and with the corresponding forming process parameters, the holding force of the abrasive can be controlled, and the functionality of special materials can be further provided. The mechanical strength of the grinding wheel can be adjusted by controlling the sintering process of the filler and the bronze infiltration process.

[0054] The following is explained in conjunction with specific embodiments:

[0055] Example 1

[0056] The present embodiment discloses a binder jet 3D printing method for a porous diamond grinding wheel, as follows:

[0057] Step 1: Figure 2 As shown, a frame structure is designed; the porous diamond grinding wheel designed in this embodiment is a cylindrical frame structure, wherein the interior of the cylindrical frame structure is a connected lattice structure with a porosity of 90%, and a layer of skin is arranged on the outside, and openings are provided on the upper surface of the skin for filling diamond and filler powder, and the thickness of the skin is 0.5 mm.

[0058] Step 2: Binder jetting to form a green body of the framework structure. Spherical 316L stainless steel powder prepared by gas atomization technology is selected as the material for printing the framework structure. The powder size is 20 μm. The green body of the framework structure is formed by using a binder jetting additive manufacturing method. By utilizing the advantages of binder jetting additive manufacturing in forming porous materials, the framework structure itself can be made porous, which is more conducive to the subsequent infiltration treatment.

[0059] Step 3, mixing powder raw materials. In this embodiment, the powder raw materials are divided into diamond powder, stainless steel powder and stainless steel balls; wherein the diamond powder size is 30 μm, and the filler is 316L stainless steel powder with a size of 20-50 μm, which are mixed at a weight ratio of 4:9, and then 304 stainless steel balls with the same weight as the mixed powder are added, and the diameters of the stainless steel balls are 4 mm and 8 mm. The three-dimensional powder mixer is set to 50 RPM, and runs for one hour in both the forward and reverse directions.

[0060] Step 4: Fill the frame structure: Fill the mixed powder into the printed cylindrical frame structure, place the cylindrical part on the homemade ultrasonic vibration table, and vibrate for 5 seconds. The parameters of the ultrasonic generator are 40kHz and the power is 50w.

[0061] Step 5: Place the part in a tubular furnace and heat it to 500°C at a heating rate of 2°C / min in an argon atmosphere, hold it for 1 hour to remove the binder in the part; then heat it to 900°C at a heating rate of 2°C / min, hold it for 1 hour to complete pre-sintering.

[0062] Step 6: Spread bronze powder on the bottom of the crucible and place the pre-sintered parts on top of the bronze powder. Place the crucible in a tube furnace and heat to 1100°C at a heating rate of 5°C / min under vacuum for one hour to complete the infiltration. Figure 3 This is a SEM image of the polished surface of the formed part. The light-colored part is the sintered matrix, and the black irregular particles are diamond particles. The diamond particles still exist after the part is polished with silicon carbide sandpaper, indicating that the grinding wheel has a high grip on the diamond abrasive particles.

[0063] Step 7: After the infiltration is completed, take out the parts, remove the impurities attached to the surface, and use the general grinding wheel dressing equipment to dress the grinding wheel working surface.

[0064] Example 2

[0065] The present embodiment discloses a binder jet 3D printing method for a porous diamond grinding wheel, as follows:

[0066] Step 1: Figure 2 As shown, the frame structure is designed. The porous diamond grinding wheel designed in this embodiment is a cylindrical frame structure, wherein the interior of the cylindrical frame structure is a connected lattice structure with a porosity of 90%. A layer of skin is arranged outside, and an opening is opened on the upper surface of the skin for filling diamond and filler powder, and the thickness of the skin is 0.5 mm.

[0067] Step 2: Binder spraying to form a green body of the frame structure. Spherical 316L stainless steel powder prepared by gas atomization technology is selected as the material for printing the frame structure. The powder size is 20 μm.

[0068] Step 3, mix the powder raw materials. The powder raw materials in this embodiment are diamond powder, stainless steel powder and pure nickel powder. The diamond powder size is 30μm, and the filler is 316L stainless steel powder with a size of 20-50μm and pure nickel powder with a size of 10-20μm. The diamond and filler are mixed at a weight ratio of 4:9, and then 304 stainless steel balls with the same weight as the mixed powder are added. The diameters of the stainless steel balls are 4mm and 8mm. The three-dimensional powder mixer is set to 50RPM and runs for one hour in both the forward and reverse directions.

[0069] Step 4: Fill the mixed powder into the printed cylindrical frame structure, place the cylindrical part on a homemade ultrasonic vibration table, and vibrate for 5 seconds. The ultrasonic generator parameters are 40kHz and the power is 50w.

[0070] Step 5: Place the part in a tubular furnace and heat it to 500°C at a heating rate of 2°C / min in an argon atmosphere, hold it for 1 hour to remove the binder in the part; then heat it to 900°C at a heating rate of 2°C / min, hold it for 1 hour to complete pre-sintering.

[0071] Step 6: Spread bronze powder on the bottom of the crucible and place the pre-sintered parts on top of the bronze powder. Place the crucible in a tube furnace and heat it to 1100°C at a heating rate of 5°C / min in a vacuum environment. Keep it for one hour to complete the infiltration. The Fe-based filler combined with Ni and Cu can further reduce the sintering temperature, reduce the thermal erosion of the bonding metal on the diamond, and improve the holding force on the diamond.

[0072] Step 7: After the infiltration is completed, take out the parts, remove the impurities attached to the surface, and use the general grinding wheel dressing equipment to dress the grinding wheel working surface.

[0073] Finally, it should be noted that relational terms such as first and second are merely used to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any actual relationship or order between these entities or operations.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A binder jet 3D printing method for a porous diamond grinding wheel, characterized in that: include: Step 1, design the frame structure of the diamond grinding wheel; Step 2, spraying a binder to form a green body of the frame structure; Step 3, mixing the diamond abrasive and the filler to obtain a mixed powder; Step 4: Fill the mixed powder into the frame structure green body, and then place the green body filled with powder on a vibration platform for compaction; Step 5, placing the green body filled with powder into an atmosphere furnace for pre-sintering; Step 6: Place the pre-sintered brown parts into a vacuum furnace for bronze infiltration treatment; Step 7: Remove impurities attached to the surface of the grinding wheel, and then dress the grinding wheel to expose the diamond abrasive.

2. The binder jet 3D printing forming method of the porous diamond grinding wheel according to claim 1, characterized in that: The frame structure in step 1 comprises a porous structure frame, and a layer of skin is covered on the periphery of the porous structure frame, and a powder filling port is retained on the skin.

3. The binder jet 3D printing forming method of the porous diamond grinding wheel according to claim 1, characterized in that: In the step 2, the metal powder material used for printing the frame structure is selected according to the required structural strength of the grinding wheel and the processing object, and the frame structure green body is formed by a binder jetting additive manufacturing method.

4. The binder jet 3D printing forming method of the porous diamond grinding wheel according to claim 1, characterized in that: In the step 3, the diamond abrasive and the filler are weighed according to the required weight ratio and placed in a mixing container; stainless steel grinding balls of different sizes are added to the mixed powder in a weight ratio of 1:1, and mixed in a three-dimensional powder mixer until the mixture is uniform without obvious component segregation.

5. The binder jet 3D printing forming method of the porous diamond grinding wheel according to claim 1, characterized in that: The calculation formula for the amount of diamond, filler and bronze in this method is as follows: M 金刚石 =C 砂轮 ×V 砂轮 / 1cm 3 ×0.88g M 填料 =D1×ρ 填料 ×(V 砂轮 ×P 框架 -M 金刚石 / (D1×ρ 金刚石 )) M 青铜 =ρ 青铜 ×(V 砂轮 ×P 框架 ×(1-D1)+V 砂轮 ×(1-P 框架 )×(1-D2)) Among them, M 金刚石 is the amount of diamond powder, M 填料 is the required amount of filler, M 青铜 is the amount of bronze required for infiltration, ρ 填料 is the density of the filler material, ρ 金刚石 is the density of diamond, ρ 青铜 is the density of bronze, C 砂轮 is the abrasive concentration of the set grinding wheel, V 砂轮 is the volume of the grinding wheel, P 框架 is the porosity of the frame structure formed by binder jetting, excluding the internal porosity of the printed part, D1 is the packing density of the mixed powder of diamond and filler, and D2 is the relative density of the frame part printed by binder jetting.

6. The binder jet 3D printing forming method of the porous diamond grinding wheel according to claim 1, characterized in that: In step 4, the compaction of the mixed powder is controlled by controlling the vibration time and power.

7. The binder jet 3D printing forming method of the porous diamond grinding wheel according to claim 1, characterized in that: In the step 5, the pre-sintering temperature is much lower than the melting point of the metal.

8. The binder jet 3D printing forming method of the porous diamond grinding wheel according to claim 1, characterized in that: In the step 7, if there is a skin structure on the working surface of the grinding wheel, it is removed together when the grinding wheel is dressed.

9. A porous diamond grinding wheel, characterized in that: It is obtained by the binder jet 3D printing forming method described in any one of claims 1-8.

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