1 Introduction
The high hardness and other excellent properties of diamond tools make it very suitable for processing nonferrous metals such as silicon alloys, aluminum alloys, copper alloys, and non-metallic materials such as fiber reinforced composites, phenolic resins, and graphite. Natural diamond materials are limited in their popularization and application because of their small size, high price, and difficulty in processing. Although the use of artificial polycrystalline diamond (PCD) tools plays an important role in the semi-finishing and finishing processes, due to the single blade shape, the absence of chip breakers, and the limitations of geometrical parameters, it is difficult to give full play to its excellent performance. The diamond thick film cutter is a new type of tool made by welding a deposited diamond thick film on a cemented carbide insert, and has excellent processing performance and a high performance-cost ratio. The research, development and application of diamond thick-film end mills in China are still at the initial stage. In this paper, the microstructure, design and preparation of diamond thick-film end mills and their application in superfinishing are studied experimentally.
2 Microstructure analysis of diamond thick film
In order to study the processing performance of diamond thick film cutting tools, the microstructure of homemade diamond thick film and imported PCD composite sheet was compared and tested with JSOM35C scanning electron microscope. The microstructure of the two materials can be seen from the microstructure images of the PCD composite film. The microstructure is granular polycrystalline structure, there are many voids, contains many acicular graphite body; due to the addition of a small amount of binder in the preparation of high temperature and high pressure, its hardness is affected (HK5000 ~ 8000), low In the hardness of natural diamond, but its impact strength is high; the cutting edge made of PCD composite sheet shows a lot of uneven micro serration, so it is suitable for semi-finishing and finishing, but it is not suitable to achieve the mirror-level surface Super precision machining. As can be seen from Fig. 2, the microstructure of diamond thick film is complete and single, with few voids and subtle, similar to that of single crystal diamond. Since the material structure is composed entirely of diamond without binder inclusion, it has a higher hardness (HK8300) and is close to it. The average value of natural diamond hardness; If you choose the appropriate grinding process, diamond thick-film tool can obtain a straight blade without jagged, very suitable for super-finishing the surface precision of the mirror level.
Design and preparation of 3 end mills
For the comparative cutting test, an end mill with the same shape and geometric parameters was prepared using a diamond thick film and a PCD compact. The preferred end mill design parameters are: diameter Ø125mm, number of teeth is 6 teeth, depth of cut is 3° to 8°, radial angle of rake is 0° to -5°, angle of main deflection is 75°; carbide substrate YG3X square blade is adopted, and the cutter body adopts indexable front pressure type. The thickness, hole diameter and connection size of the cutter body are designed according to national standards.
The laser is used to cut the PCD compact and diamond thick film into triangular pieces, and the YG3X carbide blade is ground into a sipe with the same size as the triangular diaphragm in a special tooling to be used for brazing. The diamond thick film has high interfacial energy with common metals and their alloys, and is difficult to be infiltrated by the general low-melting alloy, and the diamond thick film has poor weldability. In order to improve the weldability between the diamond thick film and the cemented carbide substrate, a special high-strength silver-copper alloy solder is used, and a hard alloy low temperature brazing process is used to weld the diamond thick film blade and the PCD blade. The brazed inserts are respectively sharpened with the same level of surface precision, the high-strength, coarse-grained diamond grinding wheel is used for the semi-finish grinding, the fine-grained diamond grinding wheel is used for the fine grinding, and the tool tip arc is made of tooling Automatic sharpening. After the end mill is assembled and adjusted, its axial and radial runout is controlled within 0.002mm.
4 cutting test
Machine tools: BI-266 CNC milling machine; Measuring instrument: M4P surface roughness measuring instrument; Workpiece material: LY12 aluminum alloy; Cutting method: Dry cutting. Under the same cutting amount, the LY12 aluminum alloy was milled with a diamond thick film end mill and a PCD end mill respectively, and the surface roughness of the specimen was measured. The test results are shown in Table 1. After the milling process was completed, the six cutters of the diamond thick-film end mill and the PCD end mill were inspected with a microscope at 100 times. It was found that each of the teeth experienced more than 6000 cutting shock loads (6 teeth with a total of 36,000 teeth) After the secondary impact), no chipping occurred in the teeth. The test results show that the diamond thick film tool with reasonable cutter head geometry not only has the advantages of PCD end mills, but also can achieve super-finishing of large planes.
Table 1 Comparison test results of diamond thick film end mill and PCD end mill
Tool Workpiece cutting amount Workpiece surface roughness
Ra(μm) Cutting speed (m/min) Cutting depth (mm) Cutting amount (mm/r)
Diamond thick end mill LY12 aluminum alloy 157 0.02 0.02 0.10
PCD End Mill LY12 Aluminum Alloy 157 0.02 0.02 0.40
The 6 to 32-teeth diamond thick-film end mills designed and manufactured by our factory have been applied to the engine production site to achieve high-efficiency, high-quality super-finishing of “milling and grindingâ€.
5 Conclusion
The microstructure of diamond thick film material is similar to that of natural single crystal diamond. Diamond thick-film tools are suitable for super-finishing machining and can partially replace expensive natural single crystal diamond tools.
The diamond thick-film end mills with reasonable geometrical design and parameters can withstand the repeated impact of cutting loads, effectively solve the super-finishing problems of non-ferrous metals and alloy materials on large planes and large planes, and can be used to mill large-scale workpieces of non-ferrous metals. Get the mirror precision processing effect.
Diamond thick-film end mills can be used not only in precision machining machines, but also in ordinary milling machines, which can achieve better processing efficiency and have application value.
The high hardness and other excellent properties of diamond tools make it very suitable for processing nonferrous metals such as silicon alloys, aluminum alloys, copper alloys, and non-metallic materials such as fiber reinforced composites, phenolic resins, and graphite. Natural diamond materials are limited in their popularization and application because of their small size, high price, and difficulty in processing. Although the use of artificial polycrystalline diamond (PCD) tools plays an important role in the semi-finishing and finishing processes, due to the single blade shape, the absence of chip breakers, and the limitations of geometrical parameters, it is difficult to give full play to its excellent performance. The diamond thick film cutter is a new type of tool made by welding a deposited diamond thick film on a cemented carbide insert, and has excellent processing performance and a high performance-cost ratio. The research, development and application of diamond thick-film end mills in China are still at the initial stage. In this paper, the microstructure, design and preparation of diamond thick-film end mills and their application in superfinishing are studied experimentally.
2 Microstructure analysis of diamond thick film
In order to study the processing performance of diamond thick film cutting tools, the microstructure of homemade diamond thick film and imported PCD composite sheet was compared and tested with JSOM35C scanning electron microscope. The microstructure of the two materials can be seen from the microstructure images of the PCD composite film. The microstructure is granular polycrystalline structure, there are many voids, contains many acicular graphite body; due to the addition of a small amount of binder in the preparation of high temperature and high pressure, its hardness is affected (HK5000 ~ 8000), low In the hardness of natural diamond, but its impact strength is high; the cutting edge made of PCD composite sheet shows a lot of uneven micro serration, so it is suitable for semi-finishing and finishing, but it is not suitable to achieve the mirror-level surface Super precision machining. As can be seen from Fig. 2, the microstructure of diamond thick film is complete and single, with few voids and subtle, similar to that of single crystal diamond. Since the material structure is composed entirely of diamond without binder inclusion, it has a higher hardness (HK8300) and is close to it. The average value of natural diamond hardness; If you choose the appropriate grinding process, diamond thick-film tool can obtain a straight blade without jagged, very suitable for super-finishing the surface precision of the mirror level.
Design and preparation of 3 end mills
For the comparative cutting test, an end mill with the same shape and geometric parameters was prepared using a diamond thick film and a PCD compact. The preferred end mill design parameters are: diameter Ø125mm, number of teeth is 6 teeth, depth of cut is 3° to 8°, radial angle of rake is 0° to -5°, angle of main deflection is 75°; carbide substrate YG3X square blade is adopted, and the cutter body adopts indexable front pressure type. The thickness, hole diameter and connection size of the cutter body are designed according to national standards.
The laser is used to cut the PCD compact and diamond thick film into triangular pieces, and the YG3X carbide blade is ground into a sipe with the same size as the triangular diaphragm in a special tooling to be used for brazing. The diamond thick film has high interfacial energy with common metals and their alloys, and is difficult to be infiltrated by the general low-melting alloy, and the diamond thick film has poor weldability. In order to improve the weldability between the diamond thick film and the cemented carbide substrate, a special high-strength silver-copper alloy solder is used, and a hard alloy low temperature brazing process is used to weld the diamond thick film blade and the PCD blade. The brazed inserts are respectively sharpened with the same level of surface precision, the high-strength, coarse-grained diamond grinding wheel is used for the semi-finish grinding, the fine-grained diamond grinding wheel is used for the fine grinding, and the tool tip arc is made of tooling Automatic sharpening. After the end mill is assembled and adjusted, its axial and radial runout is controlled within 0.002mm.
4 cutting test
Machine tools: BI-266 CNC milling machine; Measuring instrument: M4P surface roughness measuring instrument; Workpiece material: LY12 aluminum alloy; Cutting method: Dry cutting. Under the same cutting amount, the LY12 aluminum alloy was milled with a diamond thick film end mill and a PCD end mill respectively, and the surface roughness of the specimen was measured. The test results are shown in Table 1. After the milling process was completed, the six cutters of the diamond thick-film end mill and the PCD end mill were inspected with a microscope at 100 times. It was found that each of the teeth experienced more than 6000 cutting shock loads (6 teeth with a total of 36,000 teeth) After the secondary impact), no chipping occurred in the teeth. The test results show that the diamond thick film tool with reasonable cutter head geometry not only has the advantages of PCD end mills, but also can achieve super-finishing of large planes.
Table 1 Comparison test results of diamond thick film end mill and PCD end mill
Tool Workpiece cutting amount Workpiece surface roughness
Ra(μm) Cutting speed (m/min) Cutting depth (mm) Cutting amount (mm/r)
Diamond thick end mill LY12 aluminum alloy 157 0.02 0.02 0.10
PCD End Mill LY12 Aluminum Alloy 157 0.02 0.02 0.40
The 6 to 32-teeth diamond thick-film end mills designed and manufactured by our factory have been applied to the engine production site to achieve high-efficiency, high-quality super-finishing of “milling and grindingâ€.
5 Conclusion
The microstructure of diamond thick film material is similar to that of natural single crystal diamond. Diamond thick-film tools are suitable for super-finishing machining and can partially replace expensive natural single crystal diamond tools.
The diamond thick-film end mills with reasonable geometrical design and parameters can withstand the repeated impact of cutting loads, effectively solve the super-finishing problems of non-ferrous metals and alloy materials on large planes and large planes, and can be used to mill large-scale workpieces of non-ferrous metals. Get the mirror precision processing effect.
Diamond thick-film end mills can be used not only in precision machining machines, but also in ordinary milling machines, which can achieve better processing efficiency and have application value.