A ball end mill with a variable rake angle helical surface

Abstract

This invention provides a ball end mill with a variable rake angle helical surface, comprising a shank and a cutting section disposed at the front end of the shank. The cutting section includes a straight cutting edge and a ball-shaped curved cutting edge. The ball-shaped curved cutting edge has a helical rake face and a ball-shaped groove. The helical rake face extends outward from the center point of the ball end mill and has a gradually changing rake angle. The helical rake face smoothly transitions to the straight cutting edge. The ball-shaped groove is a smooth curved surface. The ball end mill with a variable rake angle helical surface provided by this application can improve the strength of the ball-shaped cutting edge and reduce cutting resistance; at the same time, it can improve the abrupt change in cutting force, improve the quality of the cutting surface, and effectively reduce the risk of failure such as chipping.

Description

Technical Field

[0001] This invention relates to the field of cutting tool technology, and in particular to machining tools used for cutting high-strength and high-toughness materials. More specifically, it relates to a ball end mill with a variable rake angle helical surface. Background Technology

[0002] End mills are the most commonly used milling cutters on CNC machine tools. They have cutting edges on both the cylindrical surface and the end face, which can cut simultaneously or individually. They are mainly used for planar milling, groove milling, stepped surface milling, and profile milling. Ball end mills are one type, and they are commonly used cutting tools in mechanical manufacturing. Currently, in the field of metal cutting, ball end mills are commonly used for machining curved metal surfaces and grooves. High-efficiency machining is the development and trend of cutting processes. Improving tool machining efficiency usually involves increasing the depth of cut, increasing the cutting tool rotation speed, and increasing the number of cutting edges. However, in the machining of curved surfaces using existing technology, increasing the depth of cut and feed rate easily leads to high cutting resistance and tool vibration, causing the tool to easily chip and accelerate tool failure. Increasing the number of teeth on the tool, on the other hand, easily leads to poor chip removal.

[0003] Under high-speed and high-efficiency machining conditions, the impact on the cutting tool will also increase, which will place higher demands on the strength of the cutting tool. In the existing technology, the rake angle of the ball end face of this type of cutting tool is usually fixed, and the bottom of the rake face is an inclined straight line connected to the circumferential cutting edge. Such cutting tools are very prone to cutting edge chipping under high impact conditions, which will affect the performance of the cutting tool, reduce its life, increase the machining cost, and also reduce the quality of the machined workpiece. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a ball end mill with a variable rake angle helical surface.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0006] A ball end mill with a variable rake angle helical surface includes a shank and a cutting section disposed at the front end of the shank. The cutting section includes a straight cutting edge and a ball cutting edge. The ball cutting edge extends from the center point of the ball end to the outer periphery of the straight cutting edge. The ball cutting edge has a helical rake face and a ball chip groove. The rake angle of the helical rake face is a gradually changing rake angle from the center point of the ball end to the straight cutting edge.

[0007] Furthermore, the rake angle of the helical rake face is from the center point of the ball outwards by ∠γ a Gradual transition to ∠γ0; where γ0 is the rake angle of the straight cutting edge, γ a The rake angle of the center helical rake face of the ball head, γ a <γ0.

[0008] Furthermore, the rake angle of the helical rake face gradually changes from ∠γ / 2 to ∠γ from the center point of the ball head to the straight cutting edge; where ∠γ is the circumferential rake angle of the straight cutting edge.

[0009] Furthermore, the ball-shaped chip groove is a smooth curved surface, one side of which is connected to the bottom of the helical rake face, and the ball-shaped chip groove is inclined from the side near the helical rake face to the side away from the helical rake face.

[0010] Furthermore, the side projection of the junction between the ball chip groove and the helical rake face is a curve that smoothly unfolds outward from the center point of the ball head.

[0011] Furthermore, the curve of the side projection at the junction of the ball chip groove and the helical rake face is a circular arc or a helical line.

[0012] Furthermore, the curve of the side projection at the junction of the ball chip groove and the helical rake face is between the arcs of 0.6R and 1.5R, where R is the radius of the ball forming the ball cutting edge.

[0013] Furthermore, the radius of curvature R0 of the side projection curve at the junction of the ball chip groove and the helical rake face is 0.75R≤R0≤1.2R, where R is the radius of the ball forming the ball cutting edge.

[0014] Furthermore, the ball end mill with a variable rake angle helical surface has a cutting edge consisting of 2, 3, 4, or 5 flutes. The tool holder and the cutting part are integrally connected.

[0015] The technical solution provided by this invention has the following beneficial effects:

[0016] The ball end mill with variable rake angle helical surface provided in this application can improve the strength of the ball end cutting edge and reduce cutting resistance; at the same time, it can improve the sudden change of cutting force, improve the quality of the cutting surface, and effectively reduce the risk of failure such as chipping. Attached Figure Description

[0017] Figure 1 The image shown is a side view of the ball end mill with a variable rake angle helical surface in the embodiment. Figure 1 ;

[0018] Figure 2 The image shown is a side view of the ball end mill with a variable rake angle helical surface in the embodiment. Figure 2 ;

[0019] Figure 3 The image shown is a side view of the ball end mill with a variable rake angle helical surface in the embodiment. Figure 3 ;

[0020] Figure 4 Shown Figure 3Schematic diagram of the rake angle of the ball end cutting edge at the N-N section.

[0021] Figure 5 The image shown is a front view of the ball end mill with a variable rake angle helical surface in the embodiment.

[0022] Figure 6 The figure shown is a three-dimensional structural diagram of the ball end mill with a variable rake angle helical surface in the embodiment.

[0023] Figure 7 The following is an example. Figure 5 Schematic diagram of the rake angle of the ball end cutting edge at point A.

[0024] Figure 8 The following is an example. Figure 5 Schematic diagram of the rake angle of the ball end cutting edge at point B.

[0025] Figure 9 The following is an example. Figure 5 Schematic diagram of the rake angle of the ball end cutting edge at point C. Detailed Implementation

[0026] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, primarily used to illustrate the embodiments and to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0027] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0028] Reference Figures 1 to 5 As shown, this embodiment provides a ball end mill with a variable rake angle helical surface, including a shank 2 and a cutting part 1 disposed at the front end of the shank 2. Specifically, the shank 2 and the cutting part 1 are integrally connected, that is, directly machined on a bar stock; more specifically, the bar stock is made of one or more materials selected from high-speed steel, cemented carbide, CBN and PCD.

[0029] Please refer to Figure 1 , 23.5. The cutting part 2 of the milling cutter of the present invention includes a straight cutting edge 6 and a ball-end cutting edge 3. The ball-end cutting edge 3 has a helical rake face 4 and a ball-end chip groove 5. The helical rake face 4 extends from the center point of the ball end to the straight cutting edge and is set with a gradually changing rake angle. The helical rake face 4 and the straight cutting edge 6 are smoothly connected. The ball-end chip groove 5 is a smooth curved surface. The straight cutting edge 6 in the present invention is also called a circumferential cutting edge. The ball-end cutting edge 3 includes a helical rake face 4 and a first flank face 7, a second flank face 8 and a third flank face 9 on the rear side. One function of the third flank face is to avoid obstacles. In use, the gradually changing rake angle of the helical rake face participates in cutting. Since the cutting operation is a rotational operation, after the phasor superposition of the helical rake face with the gradually changing rake angle, the actual cutting angle is always kept within the expected range, effectively changing the point of application of the cutting force, thereby improving the cutting performance of the tool.

[0030] In one embodiment of the present invention, the rake angle of the helical rake face of the ball end mill's ball end mill is ∠γ from the center point of the ball end mill outwards. a Gradual transition to ∠γ0; where γ0 is the rake angle of the straight cutting edge, γ a The rake angle of the center helical rake face of the ball head, γ a <γ0, such as Figure 3 and Figure 4 The rake angle of the helical rake face at point N is γ. N .

[0031] The milling cutter of this invention employs a helical rake face (i.e., helical rake face 4) on the ball end cutting edge 3. This helical rake face extends outward from the center point of the ball end and features a gradually changing rake angle. The rake angle can be designed according to the cutting material, optimizing the gradually changing rake angle to ensure the helical surface participates in the cutting speed. This effectively alters the distribution and magnitude of the cutting force, strengthens the cutting edge, and improves the tool's cutting performance. For example, the rake angle of the helical rake face 4 gradually changes from ∠γ / 2 to ∠γ from the center point of the ball end to the straight cutting edge; where ∠γ is the circumferential rake angle of the straight cutting edge.

[0032] In one embodiment of the present invention, as Figure 5 , Figure 7 , Figure 8 and Figure 9 In one embodiment of the present invention, from the center point of the ball head to the straight cutting edge, the rake angles of the helical rake face 4 of the ball head cutting edge at points A, B, and C are γ1, γ2, and γ3, respectively, and γ1 < γ2 < γ3.

[0033] In one embodiment of the present invention, as Figure 1 and Figure 2 The ball-shaped chip groove 5 of the milling cutter of the present invention is a smooth curved surface. One side of the ball-shaped chip groove 5 is connected to the bottom of the helical rake face 4. The ball-shaped chip groove 5 is inclined from the side close to the helical rake face to the side away from the helical rake face, that is, the side of the helical rake face towards the third flank face.

[0034] In one embodiment of the present invention, the side projection of the junction of the ball-shaped chip groove 5 and the helical rake face 4 of the milling cutter is curve M1, which smoothly unfolds outward from the center point of the ball head. Specifically, curve M1 of the side projection of the junction of the ball-shaped chip groove and the helical rake face can be an arc, a helix, or other curves.

[0035] In one embodiment of the present invention, the curve of the side projection of the junction of the ball chip groove and the helical rake face is between an arc of 0.6R and 1.5R, where R is the radius of the ball forming the ball cutting edge.

[0036] In one embodiment of the present invention, the radius of curvature R0 of the side projection curve at the junction of the ball chip groove and the helical rake face is 0.75R≤R0≤1.2R, where R is the radius of the ball forming the ball cutting edge.

[0037] The ball end mill of this invention features a variable rake angle helical surface. The curve M1, projected from the side of the junction between the ball-shaped chip groove 5 and the helical rake face 4, is smooth and located at the bottom of the helical rake face, ensuring a smooth and uniform transition between the helical rake face 4 and the bottom of the ball-shaped chip groove 5. This structure of the invention increases both the chip space of the ball-shaped cutting edge 3 and the strength of the ball-shaped cutting edge; it also reduces the risk of chipping of the ball-shaped cutting edge, preventing machining damage.

[0038] The ball end mill with variable rake angle helical surface provided in this application can improve the strength of the ball end cutting edge 3 and reduce the cutting resistance; at the same time, it can improve the sudden change of cutting force, improve the cutting surface quality, and effectively reduce the risk of failure such as chipping.

[0039] Specifically, in this embodiment, the ball-shaped chip groove 5 extends smoothly outward from the center point of the ball head in a spiral curve, i.e., towards the straight cutting edge 6.

[0040] Specifically, in this embodiment, the curve of the side projection of the ball chip groove 5 is between an arc of 0.75R and 1.5R, where R is the radius of the ball forming the ball end mill of the present invention; this setting achieves good results.

[0041] In this specific embodiment, taking the R5 ball end mill, i.e. the ball radius of the ball end mill of the present invention is 5mm, the circumferential rake angle of the straight cutting edge 6 is 6°, and the rake angle of the helical rake face 4 of the ball cutting edge 3 gradually changes from 3° at the center of the ball, i.e., from 3° to 6°, so as to connect with the straight cutting edge; the side projection curve of the junction of the ball chip groove 5 and the helical rake face 4 is a smooth curve between R3 and R7.

[0042] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A ball end mill with a variable rake angle helical surface, comprising a tool holder and a cutting section disposed at the front end of the tool holder, characterized in that: The cutting part includes a straight cutting edge and a ball-end cutting edge. The ball-end cutting edge extends from the center point of the ball end to the outer periphery of the straight cutting edge. The ball-end cutting edge has a helical rake face and a ball-end chip groove. The rake angle of the helical rake face is a gradually changing rake angle from the center point of the ball end to the straight cutting edge. The ball-end chip groove is a smooth curved surface and is inclined from the side near the helical rake face to the side away from the helical rake face. The side projection of the junction of the ball-end chip groove and the helical rake face is a curve that smoothly unfolds outward from the center point of the ball end.

2. The ball end mill with a variable rake angle helical surface according to claim 1, characterized in that: The rake angle of the helical rake face gradually changes from ∠γa to ∠γ0 from the center point of the ball head outwards; where γ0 is the circumferential rake angle of the straight cutting edge, γa is the rake angle of the helical rake face at the center of the ball head, and γa < γ0.

3. The ball end mill with a variable rake angle helical surface according to claim 1, characterized in that: The rake angle of the helical rake face gradually changes from ∠γ / 2 to ∠γ from the center point of the ball head to the straight cutting edge; where ∠γ is the circumferential rake angle of the straight cutting edge.

4. The ball end mill with a variable rake angle helical surface according to claim 1, characterized in that: The curve of the side projection at the junction of the ball chip groove and the helical rake face is a circular arc or a helical line.

5. The ball end mill with a variable rake angle helical surface according to claim 1, characterized in that: The curve of the side projection at the junction of the ball chip groove and the helical rake face is between the arcs of 0.6R and 1.5R, where R is the radius of the ball forming the ball cutting edge.

6. The ball end mill with a variable rake angle helical surface according to claim 5, characterized in that: The radius of curvature R0 of the side projection curve at the junction of the ball chip groove and the helical rake face is 0.75R≤R0≤1.2R, where R is the radius of the ball forming the ball cutting edge.

7. The ball end mill with a variable rake angle helical surface according to claim 1, characterized in that: The tool holder and the cutting part are an integrally connected structure.

8. The ball end mill with a variable rake angle helical surface according to any one of claims 1 to 7, characterized in that: The ball end mill has a cutting edge configuration of 2, 3, 4, or 5 flutes.

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