A diamond-coated ball-end cutter for machining a gradient wedge-angle high-precision graphite mold

Abstract

The application discloses a diamond-coated ball-end cutter for machining high-precision graphite molds with gradient wedge angles, which comprises a cutter handle and a ball head, and the spherical surface of the ball head is provided with a ball head negative reverse chamfer; the spherical surface of the ball head is divided into four fan-shaped areas, which respectively comprise a first fan-shaped area, a second fan-shaped area, a third fan-shaped area and a fourth fan-shaped area; the first fan-shaped area is used for cutting force with axial force as the main force; the second fan-shaped area is used for cutting force with radial force as the auxiliary force and axial force as the main force; the third fan-shaped area is used for cutting force with radial force as the main force and axial force as the auxiliary force; the fourth fan-shaped area is used for cutting force with radial force as the main force; and the wedge angles of the four fan-shaped areas are different from each other. The application solves the problem of high-precision graphite machining, and realizes the improvement of the service life of the cutter through the change of the cutter structure.

Description

Technical Field

[0001] This invention relates to cutting tools, specifically a diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles. Background Technology

[0002] With the development of manufacturing technologies in fields such as aerospace and 5G, the requirements for cutting tools are gradually increasing. Especially in the 3C field, with the development of 5G technology, mobile phones have special requirements for their materials. Before 5G, metal materials were used, which are beautiful and durable. However, metal has electromagnetic shielding properties, so 5G minimizes the use of metal. Plastic is perceived as a low-end product, so 3D glass has been widely used. Graphite is one of the best materials for 3D curved glass molds. Graphite has the following characteristics: easy to process, high thermal conductivity, high temperature resistance, low coefficient of linear expansion, good thermal stability, and good chemical stability. Therefore, graphite molds have become an ideal material for 3D glass hot bending forming molds, which can maximize the accuracy of 3D glass. The surface accuracy of the graphite mold after cutting affects the surface quality of 3D glass. Therefore, improving the surface accuracy of the graphite mold after cutting can effectively improve the quality of 3D glass and reduce its cost.

[0003] Diamond-coated tools are considered ideal for machining graphite due to their high hardness, high elastic modulus, high wear resistance, and low coefficient of friction. In terms of grain size, they mainly include micron-sized diamond coatings, nano-sized diamond coatings, and micro-nano-sized diamond coatings; the bonding strength between the diamond coating and the tungsten carbide substrate affects the tool life.

[0004] 3D curved glass is increasingly used in protective screens and back covers of electronic products such as computers, mobile phones, and tablets due to its innovative appearance and high touch sensitivity. Graphite, as the preferred material for hot bending dies, directly affects the quality of the glass through its processing. Therefore, research on graphite processing quality is of great significance. Cutting tools are constrained by two factors when cutting graphite. On the one hand, graphite crystals have high hardness and high corrosion resistance, which easily leads to severe abrasive wear during high-speed cutting, causing rapid wear of the diamond coating and tool failure. On the other hand, cutting experiments have shown that graphite chips form a series of brittle fractures, and the design of the tool geometry affects the shape of the graphite cut, thus affecting the surface quality of the processed graphite. Summary of the Invention

[0005] To address the shortcomings of the prior art, this invention provides a diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles. This invention solves the problem of high-precision graphite machining by improving tool life through changes in tool structure.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: a diamond-coated ball end mill for high-precision graphite mold processing with gradient wedge angle, comprising a shank and a ball end, wherein the spherical surface of the ball end is provided with a negative chamfer; The spherical surface of the ball head is divided into four sector-shaped regions, namely the first sector-shaped region, the second sector-shaped region, the third sector-shaped region, and the fourth sector-shaped region. The first sector-shaped region is for cutting forces where the tool is subjected to axial force as the main force, and the first sector-shaped region has a first sector-shaped rake angle α12=0° and a first sector-shaped clearance angle γ5=13°. The second sector-shaped region is for cutting forces where the tool is subjected to radial force as the secondary force and axial force as the main force, and the second sector-shaped region has a second sector-shaped rake angle α9=0° and a second sector-shaped clearance angle γ2=18°. The third sector-shaped region is for cutting forces where the tool is subjected to radial force as the main force and axial force as the secondary force, and the third sector-shaped region has a third sector-shaped rake angle α10=-1° and a third sector-shaped clearance angle γ3=16°. The fourth sector-shaped region is for cutting forces where the tool is subjected to radial force as the main force, and the fourth sector-shaped rake angle α11=-1° and a fourth sector-shaped clearance angle γ4=14°. The wedge angles of the four sector-shaped regions are different.

[0007] Furthermore, the negative chamfer of the ball head is centrally symmetrical, the width of the negative chamfer of the ball head is W1=0.03-0.05mm, and the angle of the negative chamfer of the ball head is α13=-11°.

[0008] Furthermore, the width of the first rear corner of the ball head W2 is 0.2mm, and the width of the second rear corner of the ball head W3 is 0.5mm.

[0009] Furthermore, the angle of the first sector region is α5=15°, the angle of the second sector region is α6=30°, the angle of the third sector region is α7=30°, and the angle of the fourth sector region is α8=15°.

[0010] Furthermore, the ball head is also provided with a circumferential blade, the front angle of the circumferential blade α2=8°, the first rear angle of the circumferential blade α3=13°, the width of the first rear angle of the circumferential blade W4=0.2mm, the second rear angle of the circumferential blade α4=26°, and the width of the second rear angle of the circumferential blade W5=0.4mm.

[0011] Furthermore, the helix angle β of the ball head is 30°, D1 is the tool diameter, D2 is the tool cutting diameter, L1 is the total tool length, L2 is the tool step length, L3 is the tool cutting length, and C0.5 represents a chamfer of 0.5mm × 45°.

[0012] Furthermore, the ball head is also provided with a ball head chip groove.

[0013] Furthermore, the surface of the cutting tool is coated with a nano-multilayer diamond coating, including a top fine-grained layer, a bottom coarse-grained layer, and a composite diamond-coated cemented carbide substrate.

[0014] Furthermore, the thickness of the top fine-grained layer is 6-8 μm, and the thickness of the bottom coarse-grained layer is 4-6 μm.

[0015] Furthermore, the composite diamond-coated cemented carbide substrate is made of tungsten carbide / titanium carbide / chromium carbide.

[0016] In summary, the present invention has achieved the following technical effects: Because graphite is a typical layered brittle material with poor mechanical strength, it is prone to breakage during machining. The end mill of this invention adopts a ball-end negative chamfer design, combined with a small rake angle. This design can effectively reduce the probability of tool breakage. When cutting graphite, the tool produces micro-cutting, and the tool forms a scraping effect on the graphite surface, which significantly improves the surface condition of the workpiece. The entire ball end is divided into four variable-angle sector areas, using different rake and clearance angles. The resulting tool wedge angle will be different in different sector areas, thus the cutting edge strength of the tool is different and adaptable to different ball end cutting speeds, thereby extending the tool life. The tool surface is also coated with a nano-multilayer diamond coating. The diamond bottom layer adopts a coarse-grained structure to ensure the bonding strength between the coating and the substrate, and the top layer adopts a nano-diamond coating to ensure the surface roughness and wear resistance of the tool, significantly improving the tool life and surface quality when cutting graphite. Attached Figure Description

[0017] Figure 1 This invention provides a diamond-coated ball end mill for high-precision graphite mold processing with gradient wedge angles. Figure 2 yes Figure 1 Annotated diagram; Figure 3 yes Figure 1 The left view; Figure 4 This is a 3D simulation diagram of the beveled edge of the ball head; Figure 5 This is a partial sectional view of the ball head section; Figure 6 yes Figure 5 A magnified view of a portion of the image; Figure 7 This is a sectional view of the circumferential blade; Figure 8 This is a schematic diagram of the front and rear angles of the ball head gradient. Figure 9 This is a schematic diagram of the composite diamond coating structure. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings.

[0019] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0024] Example: Figure 1It is a diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles. Figure 2 yes Figure 1 The diagram with annotations includes the tool holder 3 and the ball head 1. Figure 3 yes Figure 1 Left view, Figure 4 This is a 3D simulation diagram of the chamfering of the ball head. The spherical surface of the ball head 1 is provided with a negative chamfer 5, which is symmetrical about the center. Figure 5 This is a partial sectional view of the ball head section. Figure 6 yes Figure 5 A partially enlarged schematic diagram shows that the width of the negative chamfer of the ball head is W1 = 0.03-0.05 mm, the angle of the negative chamfer of the ball head is α13 = -11°, the width of the first rear angle of the ball head is W2 = 0.2 mm, and the width of the second rear angle of the ball head is W3 = 0.5 mm.

[0025] The ball head is also provided with a peripheral blade 4. Figure 7 This is a sectional view of the circumferential cutting edge. The front angle of the circumferential cutting edge is α2=8°, the first rear angle of the circumferential cutting edge is α3=13°, the width of the first rear angle of the circumferential cutting edge is W4=0.2mm, the second rear angle of the circumferential cutting edge is α4=26°, the width of the second rear angle of the circumferential cutting edge is W5=0.4mm, and the core thickness diameter is D3=1.76mm.

[0026] The ball head has a helix angle β = 30° and is also provided with a ball head chip groove 2. D1 is the tool diameter, D2 is the tool cutting diameter, L1 is the total tool length, L2 is the tool step length, L3 is the tool cutting length, and C0.5 represents a chamfer of 0.5mm × 45°.

[0027] The spherical surface of the ball head 1 is divided into four sector-shaped regions, namely the first sector-shaped region, the second sector-shaped region, the third sector-shaped region, and the fourth sector-shaped region; Figure 8 This is a schematic diagram of the front and rear angles of the ball head gradient. The angle of the first sector region is α5=15°, the angle of the second sector region is α6=30°, the angle of the third sector region is α7=30°, and the angle of the fourth sector region is α8=15°.

[0028] The first sector region is for cutting forces where the tool is primarily subjected to axial force, with a first sector rake angle α12 = 0° and a first sector clearance angle γ5 = 13°. The second sector region is for cutting forces where the tool is primarily subjected to radial force, with a second sector rake angle α9 = 0° and a second sector clearance angle γ2 = 18°. The third sector region is for cutting forces where the tool is primarily subjected to radial force, with a second sector clearance angle γ3 = 16°. The fourth sector region is for cutting forces where the tool is primarily subjected to radial force, with a fourth sector rake angle α11 = -1° and a fourth sector clearance angle γ4 = 14°. The wedge angles of the four sector regions are all different.

[0029] The ball end features a negative chamfer, which effectively prevents chipping. Since graphite machining produces mainly fragmented chips, the negative chamfer creates compression, improving surface finish. Because the linear velocity and cutting force vary across different areas of the ball end, this invention employs a zone-based tool wedge angle adjustment for different machining zones. In the first sector of the ball end, where axial force dominates, a 0° rake angle and a 13° clearance angle are used. The linear velocity is highest here, and 0° is used to prevent chipping and reduce cutting resistance. In the second zone, while radial and axial forces gradually change, axial force remains dominant; therefore, a 0° rake angle and a 18° clearance angle are used in this zone. The rake angle is reduced to decrease the tool wedge angle. In this region, the cutting allowance gradually increases. The gradual rake angle can reduce cutting vibration. In the third region, the radial and axial forces gradually change, with the radial force being dominant. Therefore, a -1° rake angle and a 16° clearance angle are used in this region, further increasing the tool wedge angle. The cutting allowance is at its maximum at this point, improving the strength of the cutting edge and the surface quality of the machined part. In the fourth region, the radial force is dominant. Near the bottom of the ball end, the linear velocity of the tool is almost zero, and the tool resistance is at its maximum. Therefore, a -1° rake angle and a 14° clearance angle are used in this region, further increasing the tool wedge angle and improving the strength of the cutting edge. Reducing the clearance angle can increase the contact area between the flank face and the workpiece, helping to improve the surface quality of the workpiece.

[0030] The surface of the cutting tool is coated with a nano-multilayer diamond coating. Figure 9 This is a schematic diagram of the composite diamond coating structure, including a top fine-grained layer 11, a bottom coarse-grained layer 12, and a composite diamond coating cemented carbide substrate 13.

[0031] The thickness of the top fine-grained layer 11 is 6-8 μm, and the thickness of the bottom coarse-grained layer 12 is 4-6 μm.

[0032] The composite diamond-coated cemented carbide substrate 13 is made of tungsten carbide cemented carbide / titanium carbide cemented carbide / chromium carbide cemented carbide, preferably tungsten carbide cemented carbide.

[0033] The top nano-fine crystalline layer of the diamond coating provides higher machining accuracy and surface quality; the bottom micron coarse crystalline layer ensures the bonding strength between the coating and the substrate. The diamond coating can guarantee the hardness and wear resistance of the tool, and ensure the tool's life.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles, characterized in that: It includes a handle and a ball head, wherein the spherical surface of the ball head is provided with a negative chamfer; The spherical surface of the ball head is divided into four sector-shaped regions, namely the first sector-shaped region, the second sector-shaped region, the third sector-shaped region, and the fourth sector-shaped region. The first sector-shaped region is for cutting forces where the tool is subjected to a predominantly axial force, with a first sector rake angle α12 = 0° and a first sector clearance angle γ5 = 13°. The second sector-shaped region is for cutting forces where the tool is subjected to a predominantly axial force and a secondary radial force, with a second sector rake angle α9 = 0° and a second sector clearance angle γ2 = 18°. The third sector-shaped region is for cutting forces where the tool is subjected to a secondary radial force and a predominantly axial force, with a second sector rake angle α9 = 0° and a second sector clearance angle γ2 = 18°. The cutting force is mainly axial and secondarily radial. The third sector has a rake angle α10 = -1° and a clearance angle γ3 = 16°. The fourth sector is for cutting forces where the tool is mainly subjected to radial force. The fourth sector has a rake angle α11 = -1° and a clearance angle γ4 = 14°. The wedge angles of the four sector sectors are different. The angles of the first sector sector are α5 = 15°, the second sector sector is α6 = 30°, the third sector sector is α7 = 30°, and the fourth sector sector is α8 = 15°.

2. The diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles as described in claim 1, characterized in that: The negative chamfer of the ball head is centrally symmetrical, the width of the negative chamfer of the ball head is W1=0.03-0.05mm, and the angle of the negative chamfer of the ball head is α13=-11°.

3. The diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles as described in claim 1, characterized in that: The width of the first rear corner of the ball head is W2 = 0.2 mm, and the width of the second rear corner of the ball head is W3 = 0.5 mm.

4. The diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles as described in claim 1, characterized in that: The ball head is also provided with a circumferential blade, with a front angle α2=8°, a first rear angle α3=13°, a first rear angle width W4=0.2mm, a second rear angle α4=26°, and a second rear angle width W5=0.4mm.

5. The diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles according to claim 1, characterized in that: The helix angle β of the ball head is 30°.

6. The diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles according to claim 1, characterized in that: The ball head is also provided with a ball head chip groove.

7. The diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles according to claim 1, characterized in that: The tool surface is coated with a nano-multilayer diamond coating, including a top fine-grained layer (11), a bottom coarse-grained layer (12), and a composite diamond-coated cemented carbide substrate (13).

8. The diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles according to claim 7, characterized in that: The thickness of the top fine-grained layer (11) is 6-8 μm, and the thickness of the bottom coarse-grained layer (12) is 4-6 μm.

9. The diamond-coated ball end mill for high-precision graphite mold machining with gradient wedge angles according to claim 7, characterized in that: The composite diamond-coated cemented carbide substrate (13) is made of tungsten carbide cemented carbide / titanium carbide cemented carbide / chromium carbide cemented carbide.

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