Ball nose end mill

Abstract

The present application provides a ball nose end mill which is suitable for finish machining, can obtain a processed surface with excellent gloss in cutting machining of a plane perpendicular to the tool rotation axis of a die or the like at the front end of the tool, and can omit the polishing process or reduce the polishing machining time. A plurality of chip discharge grooves (2) which are open at the front end and extend from the front end side of the tool toward the base end side of the tool are formed on the outer periphery of a tool body (1), a ball nose edge (5) is provided at the intersection ridge line portion of a rake face (3) of the chip discharge groove (2) and a front end relief face (4) of the tool body (1), a plane (6) perpendicular to the tool rotation axis (a) of the tool body (1) is provided at the front end of the tool, and the intersection ridge line portion of the plane (6) and the rake face (3) is configured as a center side cutting edge (7) connected to the ball nose edge (5).

Description

Technical Field

[0001] This invention relates to ball end mills. Background Technology

[0002] Ball end mills are widely used in mold making and component manufacturing. They have a ball-shaped cutting edge with a hemispherical rotation trajectory at the front end of the tool. By using the ball-shaped cutting edge with properly designed rake and clearance angles, complex curved surfaces or draft surfaces (inclined planes) of molds can be cut to obtain a good machined surface.

[0003] However, the following problem exists: the front end portion of the ball end mill (the top and vicinity of the arc-shaped ball end mill) has poorer cutting performance compared to the outer peripheral portion of the ball end mill, making it difficult to obtain a good machined surface in machining planes perpendicular to the tool's rotation axis, such as the bottom surface of the die.

[0004] Therefore, to date, ball end mills for finishing have been proposed, as shown in Patent Document 1, which aim to obtain a glossy and well-finished surface even when machining planes perpendicular to the tool's rotation axis, such as the bottom surface of a mold.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-233311

[0006] In the ball end mill of the aforementioned Patent Document 1, the two-flute ball end mill is positioned at an upper eccentric position, and the chisel edge angle of the chisel edge formed by the flank face of the two-flute ball end mill is set to 155 degrees or more. Alternatively, the ratio of the interval between the inner edges of the rake faces of the two-flute ball end mill formed by the cut to the length of the chisel edge is set to 1 / 7 to 1 / 3. The bottom surface of the mold and other planes perpendicular to the tool rotation axis are machined by the cutting action based on the chisel edge.

[0007] However, ball end mills with chisel edges have been widely used in general. Since the chisel edge is the cross ridge where the back faces of the ball end mills intersect each other at a large obtuse angle, its rake angle forms a large negative rake angle, causing chipping on the machined surface. Therefore, even if the angle (chisel edge angle) and length of the chisel edge are adjusted to appropriate values ​​as disclosed in Patent Document 1 above, it is difficult to obtain a machined surface (plane) with excellent gloss to the extent that a grinding process (finishing process) can be omitted. Therefore, the current situation is that a grinding process (finishing process) must be performed after cutting. Summary of the Invention

[0008] The present invention was made in view of the current situation, and its object is to provide a ball end mill suitable for finishing, which can produce a finished surface with excellent gloss when cutting on a plane perpendicular to the tool rotation axis, such as the bottom surface of the mold at the front end of the tool, and can eliminate the grinding process or reduce the grinding time.

[0009] The main points of the invention will be described with reference to the accompanying drawings.

[0010] A ball end mill has a plurality of chip discharge grooves 2 formed on the outer periphery of a tool body 1, which are open at the front end and extend from the front end side of the tool towards the base end side. Ball end cutting edges 5 are respectively provided at the intersection of the rake face 3 of the chip discharge groove 2 and the front clearance face 4 of the tool body 1. The ball end mill is characterized in that a plane 6 perpendicular to the tool rotation axis a of the tool body 1 is provided at the front end of the tool. The intersection of the plane 6 and the rake face 3 forms a central side cutting edge 7 connected to the ball end cutting edge 5.

[0011] In addition, according to the ball end mill of technical solution 1, the plane 6 is characterized in that the front flank face 4 and the front face 3 of each of the pair of ball end mills 5 are symmetrically arranged at 180 degrees relative to the tool rotation axis a.

[0012] In addition, according to the ball end mill of technical solution 1, the central side cutting edge 7 is located near the tool rotation axis a.

[0013] In addition, according to the ball end mill of technical solution 2, the central side cutting edge 7 is located near the tool rotation axis a.

[0014] Furthermore, according to any one of technical solutions 1 to 4, the ball end mill is characterized in that the plane 6 is connected to the front flank face 4, and the plane 6 is configured in any way as follows: when viewed from the tool tip, if the ball end mill 5 connected to the central side cutting edge 7 is designated as the positive side and its opposite side as the negative side when viewed from the tool tip, and the perpendicular line 9 relative to the perpendicular line 9 of ... The interval distance X on the positive side is more than 0% and less than 10% of the outer diameter D of the tool. The intersection point P1 is the intersection of the center cutting edge 7 or the extension line 8 of the center cutting edge 7 when viewed from the front end of the tool and the perpendicular line of the center cutting edge 7 or the perpendicular line 9 of the extension line 8 of the center cutting edge 7 passing through the rotation axis a of the tool. The intersection point P2 is the intersection of the edge line 10 formed by the plane 6 and the front flank face 4, which is away from the ball end edge 5, and the edge of the front end of the chip discharge groove 2 having the ball end edge 5 and the center cutting edge 7 connected to the ball end edge 5 when viewed from the front end of the tool.

[0015] Furthermore, according to any one of technical solutions 1 to 4, the ball end mill is characterized in that, when viewed from the front end of the tool, the opposing interval of the two ridges 10 formed by the plane 6 and the respective front flank faces 4 of a pair of ball end mills 5 that are symmetrically arranged at 180 degrees relative to the tool rotation axis a is set as the width W of the plane 6, and the width W is set to 0.005mm≤W≤0.2D, where D is the outer diameter of the tool.

[0016] Furthermore, according to the ball end mill of technical solution 5, the characteristic is that, in the plane 6, when viewed from the front end of the tool, the opposing interval of the two ridge lines 10 formed by the plane 6 and the respective front flank faces 4 of a pair of ball end mills 5 that are symmetrically arranged at 180 degrees relative to the tool rotation axis a is set as the width W of the plane 6, and the width W is set to 0.005mm≤W≤0.2D, where D is the outer diameter of the tool.

[0017] Furthermore, according to the ball end mill of technical solution 6, the width W of the plane 6 is set to 0.01mm≤W≤0.3mm when the outer diameter of the tool is D>φ1.5mm, and the width W of the plane 6 is set to 0.01mm≤W≤0.2D when the outer diameter of the tool is D≤φ1.5mm.

[0018] Furthermore, according to the ball end mill of technical solution 7, the width W of the plane 6 is set to 0.01mm≤W≤0.3mm when the outer diameter of the tool is D>φ1.5mm, and the width W of the plane 6 is set to 0.01mm≤W≤0.2D when the outer diameter of the tool is D≤φ1.5mm.

[0019] As the present invention is configured as described above, it becomes a ball end mill suitable for finishing. When cutting on a plane perpendicular to the tool's rotation axis, such as the bottom surface of the mold at the tool's front end, the ball end mill can produce a finished surface with excellent gloss, thus eliminating the need for grinding or reducing grinding time. Attached Figure Description

[0020] Figure 1 This is an explanatory top view showing the main parts of this embodiment as seen from the front of the tool.

[0021] Figure 2 (a) is a illustrative left-side view showing the main parts of this embodiment. Figure 2 (b) is an illustrative front view showing the main parts of this embodiment.

[0022] Figure 3 This is an explanatory diagram showing the positive side, negative side, spacing distance X, and plane width W as viewed from the tool tip in this embodiment.

[0023] Figure 4 This is a schematic diagram viewed from the front end of the tool when the intersection point P2 exists on both the positive and negative sides in this embodiment.

[0024] Figure 5 These are photographs showing the evaluation results of the gloss of the 0° surface of this embodiment and the existing product in Experimental Example 3.

[0025] Figure 6 The graph shows the measurement results of the arithmetic mean roughness Ra of the 0° surface for processing times of 20 minutes and 60 minutes for this embodiment and the existing product in Experimental Example 3.

[0026] Figure 7 This is a graph showing the measurement results of the arithmetic mean roughness Ra of the 0° and 45° surfaces of the present embodiment and the existing product, respectively, with a processing time of 20 minutes in Experimental Example 3.

[0027] Figure 8 This is an illustrative top view showing the main part of another example 1 of this embodiment, viewed from the front of the tool.

[0028] Figure 9 (a) is a left-side illustrative view showing the main parts of another example 1 of this embodiment. Figure 9(b) is an illustrative front view showing the main part of another example 1 of this embodiment.

[0029] Figure 10 This is an illustrative top view showing the main parts of another example 2 of this embodiment, viewed from the front of the tool.

[0030] Figure 11 (a) is a left-hand illustrative view showing the main parts of another example 2 of this embodiment. Figure 11 (b) is an illustrative front view showing the main part of another example 2 of this embodiment.

[0031] Label Explanation

[0032] 1: Tool body; 2: Chip removal groove; 3: Rake face; 4: Front flank face; 5: Ball end edge; 6: Plane; 7: Center side cutting edge; 8: Extension line; 9: Perpendicular line; 10: Edge line; a: Tool rotation axis; X: Spacing distance. Detailed Implementation

[0033] The function of the invention is illustrated with reference to the accompanying drawings, and preferred embodiments of the invention are briefly described.

[0034] In this invention, since a plane 6 perpendicular to the tool rotation axis a of the tool body 1 is provided at the front end of the tool, there is no transverse cutting edge with a large negative angle, which can prevent biting as much as possible due to the influence of the transverse cutting edge.

[0035] Furthermore, in this invention, since the intersection of the plane 6 and the rake face 3 forms a central side cutting edge 7 connected to the ball end face 5, the central side cutting edge 7 has the same rake angle as the ball end face 5, and thus exhibits the same high cutting performance as the ball end face 5. In plane machining perpendicular to the tool rotation axis a, the high cutting performance of the central side cutting edge 7 and the polishing effect based on the sliding contact action of the plane 6 to the cutting surface can suppress the generation of cutting marks caused by the central side cutting edge 7, and a machined surface with the same or better gloss as when machining with the ball end face 5 can be obtained.

[0036]

Example

[0037] Specific embodiments of the present invention will be described with reference to the accompanying drawings.

[0038] This embodiment is a ball end mill. The ball end mill has multiple chip discharge grooves 2 formed on the outer periphery of the tool body 1, which are open at the front end and extend from the front end side of the tool towards the base end side of the tool. Ball end cutting edges 5 are respectively provided at the intersection of the rake face 3 of the chip discharge groove 2 and the front flank face 4 of the tool body 1. A plane 6 perpendicular to the tool rotation axis a of the tool body 1 is provided at the front end of the tool. The intersection of the plane 6 and the rake face 3 forms a central side cutting edge 7 connected to the ball end cutting edge 5.

[0039] Specifically, this embodiment describes the ball end mill of the present invention as a double-edged ball end mill as follows: Figure 1 and Figure 2 As shown, two spiral chip discharge grooves 2 are provided, and ball-end cutting edges 5 are respectively provided at the intersection of the two front cutting edges 3 formed at the front end of the chip discharge grooves 2 and the front rear cutting edge 4 of the tool body 1.

[0040] More specifically, in this embodiment, a cutout 11, which is part of the chip discharge groove 2, is formed at the front end of the rake face 3 (the wall surface facing the front side in the tool rotation direction), and a cutout surface 12 facing the front side in the tool rotation direction is provided. This cutout surface 12 serves as the rake face 3 at the front end of the tool. Furthermore, in addition to the structure described above, this embodiment may also have other structures, such as... Figure 8 and Figure 9 Another example 1 shown is a ball end mill with a so-called straight-edge shape: a straight chip discharge groove 2 is provided without a cut 11, that is, a cut 12 is not provided, and the wall surface of the chip discharge groove 2 facing the front side of the tool rotation direction is configured as the rake face 3 of the tool front end.

[0041] Furthermore, in this embodiment, the central side cutting edge 7 near the tool rotation axis a is configured in a so-called upper eccentric shape relative to the tool rotation axis a in front of the tool rotation direction when viewed from the tool tip.

[0042] Specifically, this embodiment is configured with an upper eccentric shape as follows: when viewed from the tool tip, the chip discharge groove 2 (cutout 11) open at the tip is provided separately from the tool rotation axis a, such that the core remains around the tool rotation axis a from the outer periphery of the tool. A central cutting edge 7 is provided near the tool rotation axis a at the edge of the tip of the chip discharge groove 2 (cutout 11). Furthermore, when viewed from the tool tip, the chip discharge groove 2 (cutout 11) constituting this upper eccentric shape can be provided either beyond the tool rotation axis a from the outer periphery of the tool or without crossing the tool rotation axis a.

[0043] Furthermore, this embodiment is not limited to the above structure, that is, it is not limited to... Figures 1-4 , Figure 8 , Figure 9 The structure shown, with its eccentric shape, can also be, for example, like... Figure 10 , Figure 11 As shown in Example 2, the cutting edge 7 on the center side near the tool rotation axis a is configured in a so-called lower eccentric shape relative to the tool rotation axis a, with the cutting edge 7 positioned on the rear side of the tool rotation direction when viewed from the tool tip.

[0044] The following is a detailed description of the structure of each part of this embodiment.

[0045] like Figure 1 and Figure 2 As shown, the front flank face 4 of this embodiment is composed of a first flank face 4a that is inclined at a predetermined angle relative to the tool rotation axis a, a second flank face 4b that is disposed on the tool rotation rear side of the first flank face 4a and is inclined at an angle different from that of the first flank face 4a, and a third flank face 4c that is disposed on the tool rotation rear side of the second flank face 4b and is inclined at an angle different from that of the second flank face 4b.

[0046] Additionally, two ball-end cutting edges 5 (a pair of ball-end cutting edges 5) are disposed at the intersection of the first rear cutting edge 4a of each front rear cutting edge 4 and the front cutting edge 3 (cutting surface 12) facing the direction of tool rotation, such as... Figure 1 As shown, the two ball end mills 5 are configured to be 180 degrees rotationally symmetrical with respect to the tool rotation axis a. Furthermore, this embodiment is not limited to the structure of the double-edged ball end mill described above; it can also be configured as a multi-edged ball end mill with three or more ball end mills by providing additional ball end mills in addition to the two (pair) ball end mills 5.

[0047] Furthermore, as mentioned above, plane 6 is perpendicular to the tool's rotation axis a at the tool's front end, and is positioned between the two front relief faces 4 as a plane connected to them. Additionally, in the figure, the arrow labeled T indicates the tool's rotation direction.

[0048] Specifically, the plane 6 is configured to connect with the first flank face 4a and the rake face 3 of each of the two (pair) ball-end cutting edges 5. Furthermore, the intersection of the plane 6 and the rake face 3 of each ball-end cutting edge 5 is connected to the ball-end cutting edge 5, forming a center side cutting edge 7 with the same rake angle as the ball-end cutting edge 5.

[0049] In addition, in this embodiment, the plane 6 is formed such that the central side cutting edge 7 is located near the tool rotation axis a, thereby enabling the production of a machined surface with less chipping and excellent gloss during plane machining perpendicular to the tool rotation axis a.

[0050] Specifically, in this embodiment, as Figure 3As shown, plane 6 is connected to the front flank face 4 (first flank face 4a). When viewed from the tool tip, if the side of the ball end edge 5 connected to the center side cutting edge 7 is designated as the positive side and the opposite side as the negative side, when viewed from the tool tip, the plane 6 is provided with a junction point P2 (when viewed from the tool tip, the side of the edge 10 formed by plane 6 and the front flank face 4 that is away from the ball end edge 5 is connected to the ball end edge 5). The intersection of the front edge of the chip discharge groove 2 of the center-side cutting edge 7 exists on the negative side, or exists on the positive side where the distance X along the direction of the center-side cutting edge 7 is more than 0% and less than 10% of the outer diameter D of the tool, when viewed from the front end of the tool. Thus, the plane 6 is configured such that the center-side cutting edge 7 is provided near the tool rotation axis a.

[0051] Here, in this embodiment, as Figure 3 and Figure 4 As shown, the central cutting edge 7 is formed as a straight line at the intersection of the plane 6 and the rake face 3 (cutting face 12) facing the direction of tool rotation. This central cutting edge 7 can be formed as a straight line over its entire area, or only partially. For example, it can be formed as a straight line from the intersection point Q of the central cutting edge 7 and the connected ball end face 5 (the intersection point between the ridge 10 formed by the plane 6 and the front flank face 4 (first flank face 4a) near the ball end face 5 and the edge of the front end of the chip discharge groove 2 having the ball end face 5 and the central cutting edge 7 connected to the ball end face 5) towards the inner side of the tool (opposite to the ball end face 5, i.e., the negative side). (The following will describe...) Figure 4 (b) is an example of a way in which a portion of the cutting edge is in a straight line. In this case, it is sufficient to capture the straight portion, determine the extension line 8 of the center side cutting edge 7 and the direction along the center side cutting edge 7, and confirm the interval distance X.

[0052] in addition, Figure 4 This is a schematic diagram showing the intersection point P2 on the positive side and the negative side when viewed from the tool tip of this embodiment, where the cutting edge 7 is formed into a straight line from the center side. Figure 4 (a) and (b) are schematic diagrams showing the case where the intersection point P2 exists on the positive side. Figure 4 (c) and (d) are schematic diagrams showing the case where the intersection point P2 exists on the negative side.

[0053] Specifically, Figure 4 (a) and (b) are examples where the intersection P2 exists at the edge of the front end of the chip discharge groove 2 with the center side cutting edge 7 and at the edge of the front end of the wall (rake face 3) facing the front side of the tool rotation direction. Figure 4 (b) is an example in which the center-side cutting edge 7 is formed by a straight portion from the intersection point Q of the center-side cutting edge 7 and the ball-end cutting edge 5 that is connected to it, toward the inside of the tool (in the opposite direction to the ball-end cutting edge 5, i.e., the negative side), and a curved portion that is connected to the edge of the wall surface toward the rear side of the tool rotation direction, and the intersection point P2 exists in the curved portion.

[0054] in addition, Figure 4 (c) is an example where the intersection point P2 exists at the edge of the front end of the chip discharge groove 2 with the center side cutting edge 7 and exists on the negative side edge of the front end of the same surface as the wall (rake face 3) facing the front side of the tool rotation direction. Figure 4 (d) is an example where the intersection point P2 exists at the edge of the front end of the chip discharge groove 2 with the central side cutting edge 7 and at the edge of the front end of the wall facing the rear side of the tool rotation direction on the negative side.

[0055] As described above, the interval distance X in this embodiment is one of the inventive elements (indicators) used when the intersection point P2 exists on the positive side. To aid in understanding the content of Experimental Examples 1 and 2 described later, in Figure 4 In (c) and (d), parentheses are used to indicate the portion corresponding to the interval distance X. In this case, X takes a negative value.

[0056] Furthermore, the central side cutting edge 7 is not limited to a straight line; it can also be curved. For example, as shown... Figure 3 and Figure 4 As shown in (a), when the intersection point P2 exists on the positive side, these figures show a center-side cutting edge 7 formed as a straight line with endpoints at intersection points Q and P2. However, the center-side cutting edge 7 can also be formed as a curve curving towards the front or rear of the tool rotation direction, or as a wavy line. In this case, it is sufficient to consider the imaginary straight line connecting intersection points Q and P2 as the center-side cutting edge 7, determine the extension line 8 of the center-side cutting edge 7 and the direction along the center-side cutting edge 7, and confirm the interval distance X.

[0057] Furthermore, in plane 6 of this embodiment, as Figure 3As shown, when viewed from the front end of the tool, the opposing interval of the two ridge lines 10 formed by the plane 6 and the front rear cutting surfaces 4 (first rear cutting surfaces 4a) of a pair of ball-end cutting edges 5 that are symmetrically arranged at 180 degrees relative to the tool's rotation axis a is defined as the width W of the plane 6. In this embodiment, the plane 6 is formed such that its width W is 0.005mm ≤ W ≤ 0.2D (D is the outer diameter of the tool).

[0058] Specifically, as a more preferred specification, as described below, when the outer diameter D of the tool is greater than φ1.5mm, the width W of the plane 6 in this embodiment is formed as 0.01mm≤W≤0.3mm, and when the outer diameter D of the tool is less than or equal to φ1.5mm, the width W of the plane 6 in this embodiment is formed as 0.01mm≤W≤0.2D.

[0059] The effects of this embodiment, configured as described above, will be explained below.

[0060] In this embodiment, a plane 6 perpendicular to the tool rotation axis a of the tool body 1 is provided at the front end of the tool. The intersection of the plane 6 and the rake face 3 forms a central side cutting edge 7 connected to the ball end cutter 5. Therefore, the central side cutting edge 7 has the same rake angle as the ball end cutter 5 and performs high cutting performance in the same way. Through the good cutting action based on the central side cutting edge 7 and the polishing effect based on the sliding contact action of the plane 6 to the cutting surface after cutting by the central side cutting edge 7, the generation of cutting marks during cutting based on the central side cutting edge 7 can be suppressed. Even in plane machining perpendicular to the tool rotation axis a, a machined surface with excellent gloss can be obtained.

[0061] In addition, in this embodiment, the plane 6 is connected to the front flank face 4 (first flank face 4a), and when viewed from the tool tip, if the side of the ball-end edge 5 connected to the center-side cutting edge 7 is designated as the positive side and the opposite side as the negative side relative to the perpendicular line 9 of ... The intersection of the front edge of the chip discharge groove 2 is located on the negative side, or on the positive side where the distance X between the intersection P1 (when viewed from the front end of the tool, the intersection of the center cutting edge 7 or the extension line 8 of the center cutting edge 7 and the perpendicular line 9 of the center cutting edge 7 or the perpendicular line 9 of the extension line 8 of the center cutting edge 7 passing through the tool rotation axis a) and the intersection P2 is more than 0% and less than 10% of the tool outer diameter D. Therefore, the center cutting edge 7 is set near the tool rotation axis a, thereby enabling the machining surface with less chipping to be obtained in the machining of a plane perpendicular to the tool rotation axis a.

[0062] Furthermore, in this embodiment, the width W of the plane 6 is formed as 0.005mm≤W≤0.2D. Moreover, as a more preferred specification, when the tool outer diameter D is greater than φ1.5mm, the width W is formed as 0.01mm≤W≤0.3mm; when the tool outer diameter D is less than φ1.5mm, the width W is formed as 0.01mm≤W≤0.2D. Therefore, it is possible to suppress the generation of chipping and chip welding caused by increased cutting resistance, and to suppress the development of wear on the plane 6, resulting in a machined surface with gloss as good as or better than that obtained after finishing with the ball end mill 5.

[0063] Thus, this embodiment becomes a ball end mill suitable for finishing. When cutting on a plane perpendicular to the tool's rotation axis a, such as the bottom surface of the mold at the tool's front end, the ball end mill can produce a finished surface with excellent gloss, eliminating the need for grinding or reducing grinding time.

[0064] Next, experimental examples demonstrating the effectiveness of this embodiment will be described.

[0065] <Experimental Example 1>

[0066] Experimental Example 1 is an example of determining the appropriate forming range of plane 6 based on the position of the central side cutting edge 7 formed by setting plane 6, such as... Figure 3As shown, when viewed from the front end of the tool, samples with altered positions of the central side cutting edge 7 were produced by changing the distance X between intersection points P1 and P2 along the direction of the central side cutting edge 7. Each sample was used to evaluate the gloss of the machined surface when the workpiece was machined under the following machining conditions. Here, intersection point P1 is the intersection of the central side cutting edge 7 or the extension line 8 of the central side cutting edge 7 and the perpendicular line 9 of the central side cutting edge 7 or the perpendicular line 9 of the extension line 8 of the central side cutting edge 7 passing through the tool rotation axis a. Intersection point P2 is the intersection of the edge 10 formed by the plane 6 and the front flank face 4 (first flank face 4a) on the side away from the ball end edge 5 and the edge of the front end of the chip discharge groove 2 having the ball end edge 5 and the central side cutting edge 7 connected to the ball end edge 5.

[0067] Specifically, with tool specifications set to outer diameter D: φ6mm, shank diameter: φ6mm, and effective length: 30mm, and with outer diameter D: φ3mm, shank diameter: φ6mm, and effective length: 12mm, machining times were set to 20 minutes and 60 minutes respectively. The gloss of the machined surface was evaluated visually when machining a plane perpendicular to the tool's rotation axis a using the tool's tip. Furthermore, regarding the tool specifications in Experimental Example 1, with the outer diameter D set to φ6mm, the width W of plane 6 (in...) Figure 3 The opposing interval of the two ridge lines 10 formed by the plane 6 and the front flank faces 4 (first flank face 4a) of each of the pair of ball-end cutting edges 5 is set to 0.02 mm. When the outer diameter D of the tool is set to φ3 mm, the width W of the plane 6 is set to 0.01 mm. In tool manufacturing, when the diameter ratio X / D (hereinafter referred to as "diameter ratio X / D") of the interval distance X relative to the outer diameter D of the tool is 0, that is, when the interval distance X = 0.00, W = 0.1 mm when the outer diameter D of the tool is set to φ6 mm, and W = 0.05 mm when the outer diameter D of the tool is set to φ3 mm. In addition, when the diameter ratio X / D = -0.01, W = 0.2 mm when the outer diameter D of the tool is set to φ6 mm, and W = 0.1 mm when the outer diameter D of the tool is set to φ3 mm.

[0068] [Machining conditions when tool outer diameter D is set to φ6mm]

[0069] Workpiece to be machined: Pre-hardened steel (30HRC)

[0070] Rotation speed: 13,000 min -1

[0071] Feed rate: 1,500 mm / min

[0072] Axial cut-in depth: 0.05mm

[0073] Radial cut-in depth: 0.1mm

[0074] Coolant: Water-soluble cutting fluid

[0075] [Machining conditions when tool outer diameter D is set to φ3mm]

[0076] Workpiece to be machined: Pre-hardened steel (30HRC)

[0077] Rotation speed: 19,000 min -1

[0078] Feed rate: 950 mm / min

[0079] Axial cut-in depth: 0.05mm

[0080] Radial cut-in depth: 0.05mm

[0081] Coolant: Water-soluble cutting fluid

[0082] [result]

[0083] Table 1 shows the specifications (interval distance X, diameter ratio X / D) and gloss evaluation results for each sample when the tool's outer diameter D is set to φ6mm. Table 2 shows the specifications (interval distance X, diameter ratio X / D) and gloss evaluation results for each sample when the tool's outer diameter D is set to φ3mm. Regarding the interval distance X in Tables 1 and 2, a negative number indicates that the perpendicular line 9 of the intersection point P2 relative to the center-side cutting edge 7 passing through the tool's rotation axis a exists on the negative side. Furthermore, 0.00 indicates the interval distance X when the intersection point P2 coincides with the intersection point P1. Regarding the gloss evaluation results, ◎ indicates excellent gloss equal to or better than the surface finished using the ball-end cutting edge 5, ○ indicates better gloss than the surface finished using the chisel edge of an existing product, and × indicates gloss equal to the surface finished using the chisel edge of an existing product.

[0084] In addition, in this experimental example 1, the machined surface after finishing with the ball end mill 5 is a plane inclined at 45° relative to the tool rotation axis a.

[0085] Table 1

[0086]

[0087] Table 2

[0088]

[0089] As shown in Tables 1 and 2, in both cases where the tool outer diameter D is set to φ6mm and φ3mm, it was confirmed that in specifications where the diameter ratio X / D is greater than 0.1, i.e., the interval distance X is greater than 10% of the tool outer diameter D, the gloss is equivalent to that achieved when finishing with the chisel edge of an existing product, regardless of whether the machining time is 20 minutes or 60 minutes. This can be attributed to the fact that, since the interval distance X is greater than 10% of the tool outer diameter D, the center-side cutting edge 7, which has higher machinability, exists at a position far from the tool rotation axis a. In contrast, in the region on the tool rotation axis a side, the edge 10 of the plane 6 and the front flank face 4 (first flank face 4a) acts as a cutting edge forming a larger negative rake angle, causing chipping on the machined surface. Even with subsequent sliding contact between the plane 6 and the cutting surface, a sufficient polishing effect cannot be obtained.

[0090] Furthermore, it was confirmed that for specifications with a diameter ratio X / D of 0.1 or less, i.e., a spacing distance X of 10% or less of the tool's outer diameter D, the surface finish was better than that achieved by finishing with the chisel edge of existing products, regardless of the machining time, whether it was 20 minutes or 60 minutes. In particular, it was confirmed that for specifications with a diameter ratio X / D of 0.08 or less, i.e., a spacing distance X of 8% or less of the tool's outer diameter D, the surface finish was equal to or better than that achieved by finishing with the ball-end cutting edge 5.

[0091] Through Experiment 1, it was confirmed that by setting the plane 6 in a manner that forms the center-side cutting edge 7 near the tool rotation axis a, a machined surface with excellent gloss can be obtained. Specifically, when viewed from the tool tip, if the ball end edge 5 connected to the center-side cutting edge 7 is designated as the positive side and its opposite side as the negative side relative to the perpendicular line 9 passing through the tool rotation axis a and the perpendicular line 9 of the extension line 8 of the center-side cutting edge 7, a machined surface with excellent gloss can be obtained by setting the plane 6 in any manner such that the intersection point P2 exists on the negative side, or the distance X between the intersection point P1 and the intersection point P2 in the direction along the center-side cutting edge 7 exists on the positive side, which is 0% or more and 10% or less (0.1D or less) of the tool outer diameter D, preferably 0% or more and 8% or less (0.08D or less).

[0092] <Experimental Example 2>

[0093] Experimental Example 2 is an example of determining the appropriate forming range of plane 6 based on the width W of plane 6, such as... Figure 3As shown, when viewed from the front end of the tool, the opposing interval of the two ridges 10 formed by the plane 6 and the front flank faces 4 (first flank face 4a) of each of the pair of ball-end cutting edges 5 is set as the width W of the plane 6. Samples with the width W of the plane 6 changed are made, and each sample is used to evaluate the gloss of the machined surface when the workpiece is cut under the following machining conditions.

[0094] Specifically, with tool specifications set as follows: outer diameter D: φ6mm, shank diameter: φ6mm, effective length: 30mm; outer diameter D: φ3mm, shank diameter: φ6mm, effective length: 12mm; and outer diameter D: φ1.5mm, shank diameter: φ4mm, effective length: 6mm, the processing time was set to 20 minutes and 60 minutes respectively. The gloss of the machined surface when machining a plane perpendicular to the tool's rotation axis a using the tool tip was evaluated visually. Furthermore, regarding the tool specifications in Experimental Example 2, the interval distance X was set to an appropriate value for each sample as shown in Tables 3-5 below.

[0095] [Machining conditions when tool outer diameter D is set to φ6mm]

[0096] Workpiece to be machined: Pre-hardened steel (30HRC)

[0097] Rotation speed: 13,000 min -1

[0098] Feed rate: 1,500 mm / min

[0099] Axial cut-in depth: 0.05mm

[0100] Radial cut-in depth: 0.1mm

[0101] Coolant: Water-soluble cutting fluid

[0102] [Machining conditions when tool outer diameter D is set to φ3mm]

[0103] Workpiece to be machined: Pre-hardened steel (30HRC)

[0104] Rotation speed: 19,000 min -1

[0105] Feed rate: 950 mm / min

[0106] Axial cut-in depth: 0.05mm

[0107] Radial cut-in depth: 0.05mm

[0108] Coolant: Water-soluble cutting fluid

[0109] [Machining conditions when tool outer diameter D is set to φ1.5mm]

[0110] Workpiece to be machined: Pre-hardened steel (30HRC)

[0111] Rotation speed: 20,000 min -1

[0112] Feed rate: 400 mm / min

[0113] Axial cut-in depth: 0.015mm

[0114] Radial cut-in depth: 0.03mm

[0115] Coolant: Water-soluble cutting fluid

[0116] [result]

[0117] Table 3 shows the specifications (width W of plane 6, the ratio of the width W of plane 6 to the diameter of the tool's outer diameter D, W / D (hereinafter referred to as "diameter ratio W / D"), and the interval distance X) and the evaluation results of gloss for each sample when the tool's outer diameter D is set to φ6mm. Table 4 shows the specifications (width W of plane 6, diameter ratio W / D, and interval distance X) and the evaluation results of gloss for each sample when the tool's outer diameter D is set to φ3mm. Table 5 shows the specifications (width W of plane 6, diameter ratio W / D, and interval distance X) and the evaluation results of gloss for each sample when the tool's outer diameter D is set to φ1.5mm. Regarding the interval distance X in Tables 3-5, a negative number indicates that the perpendicular line 9 of the intersection point P2 relative to the central side cutting edge 7 passing through the tool's rotation axis a exists on the negative side. Furthermore, regarding the evaluation results of gloss, ◎ indicates gloss that is equal to or better than that of the machined surface after finishing with the ball-end blade 5, ○ indicates gloss that is better than that of the machined surface after finishing with the cross-edge of the existing product, and × indicates gloss that is equal to that of the machined surface after finishing with the cross-edge of the existing product.

[0118] In addition, in this experimental example 2, the machined surface after finishing with the ball end mill 5 is a plane inclined at 45° relative to the tool rotation axis a.

[0119] Table 3

[0120]

[0121] Table 4

[0122]

[0123] Table 5

[0124]

[0125] As shown in Tables 3-5, in any of the cases where the tool outer diameter D is set to φ6mm, φ3mm, or φ1.5mm, it was confirmed that in the specification where the width W of plane 6 is 0.002mm, regardless of whether the processing time is 20 minutes or 60 minutes, chipping occurs, resulting in a gloss level equivalent to that achieved by finishing with the cross-edge of an existing product. Furthermore, it was confirmed that in the specification where the width W of plane 6 is 0.005mm, the gloss level is better than that achieved by finishing with the cross-edge of an existing product. This can be attributed to the fact that when the width W of plane 6 is less than 0.005mm, the polishing effect resulting from the sliding contact of plane 6 is reduced.

[0126] Furthermore, as shown in Tables 3 and 4, when the tool outer diameter D is set to φ6mm and when it is set to φ3mm, it was confirmed that in the case where the width W of the plane 6 is 0.01mm or more and the diameter ratio W / D is 0.2 or less (i.e., the width W of the plane 6 is 20% or less of the tool outer diameter D), the surface finish is better than that of the finished surface after finishing with the cross-blade of the existing product. In particular, it was confirmed that in the case of the above-mentioned width W in the initial processing stage (processing time of 20 minutes) and in the case of processing time of 60 minutes and the width W of the plane 6 is 0.01mm or more and 0.3mm or less, the surface finish is as good as or better than that of the finished surface after finishing with the ball-end blade 5.

[0127] Furthermore, as shown in Table 5, when the tool outer diameter D is set to φ1.5mm, it was confirmed that in the specification where the width W of the plane 6 is 0.01mm or more and the diameter ratio W / D is 0.2 or less (i.e., the width W of the plane 6 is 20% or less of the tool outer diameter D, and therefore the width W of the plane 6 is 0.3mm or less), regardless of whether the processing time is 20 minutes or 60 minutes, the surface finish is equal to or better than that of the surface finished by using the ball-end cutting edge 5.

[0128] Furthermore, in any of the cases where the tool outer diameter D is set to φ6mm, φ3mm, or φ1.5mm, it was confirmed that in specifications where the diameter ratio W / D is greater than 0.2 (i.e., the width W of the plane 6 is greater than 20% of the tool outer diameter D), the surface finish was better than that after finishing with the chisel edge of the existing product in the initial stage of machining (machining time of 20 minutes). It was also confirmed that at a machining time of 60 minutes, the gloss decreased, becoming the same as that after finishing with the chisel edge of the existing product. This can be attributed to the fact that because the width W of the plane 6 is greater than 20% of the tool outer diameter D, the cutting resistance increases, causing chipping or inducing chip welding from the initial stage of machining. Even with subsequent sliding contact between the plane 6 and the cutting surface, a sufficient polishing effect cannot be achieved.

[0129] In the above, through Experiment 2, it was confirmed that by forming a plane with a width W of plane 6 of 0.005mm≤W≤0.2D, a processed surface with excellent gloss can be obtained.

[0130] Furthermore, it is preferable that when the outer diameter D of the tool is greater than φ1.5mm, the plane 6 is formed with a width W of 0.01mm≤W≤0.3mm, and when the outer diameter D of the tool is less than φ1.5mm, the plane 6 is formed with a width W of 0.01mm≤W≤0.2D, thereby obtaining a machined surface with better gloss.

[0131] Furthermore, although not shown in Tables 3-5, it was confirmed during the implementation of Experimental Example 2 described above that even if the width W of the plane 6 is confirmed to be of the same or better gloss as the surface finished by using the ball-end cutting edge 5 (evaluated as ◎), when viewed from the front end of the tool, by making the diameter of the circle that forms the rotation trajectory of the plane 6 a value larger than 35% of the outer diameter D of the tool, it is not necessarily that it will have the same or better gloss as the surface finished by using the ball-end cutting edge 5 (evaluated as ◎), and there are cases where it will have a better gloss than the surface finished by using the cross-edge of the existing product (evaluated as ○).

[0132] This can be attributed to the fact that by making the diameter of the circle that forms the rotation trajectory of plane 6 larger than 35% of the tool's outer diameter D, the cutting resistance increases and a good cutting surface cannot be obtained. Therefore, even with the subsequent sliding contact action of plane 6 towards the cutting surface, a sufficient polishing effect to the extent that a machined surface with excellent gloss cannot be obtained.

[0133] Based on the above, it is preferable that, when viewed from the front end of the tool, the plane 6 is formed in such a way that the diameter of the circle that forms the rotation trajectory of the plane 6 is less than 35% of the outer diameter D of the tool, that is, the longest distance between the tool rotation axis a, which is the largest circle that forms the rotation trajectory of the plane 6, and the outer edge of the plane 6 is less than 17.5% of the outer diameter D of the tool.

[0134] <Experimental Example 3>

[0135] Experimental Example 3 compares and evaluates this embodiment with a conventional product (a ball end mill with a chisel edge at the tool tip). In this embodiment, the width W of the plane 6 is set to 0.025 mm, and the spacing X is set to 0.005 mm. The only difference between this embodiment and the conventional product is whether the tool tip has a plane 6 or a chisel edge; that is, the ball end mill 5 and other parts are the same specifications. Using this embodiment and the conventional product with the same specifications, the gloss and surface roughness of the machined surface are evaluated when cutting a workpiece under the following machining conditions.

[0136] Specifically, the tool specifications of this embodiment and existing products are: tool outer diameter D: φ3mm, shank diameter: φ6mm, and effective length: 12mm. The gloss of the machined surface is evaluated by visual inspection (appearance of the reflected image) when machining a plane perpendicular to the tool rotation axis a (hereinafter referred to as the "0° plane") for 20 minutes and 60 minutes using the tool tip, and when machining a plane inclined at 45° relative to the tool rotation axis a (hereinafter referred to as the "45° plane") for 20 minutes and 60 minutes using the ball end mill 5. Furthermore, the surface roughness is evaluated by measuring the arithmetic mean roughness Ra.

[0137] [Processing Conditions]

[0138] Workpiece to be machined: Pre-hardened steel (30HRC)

[0139] Rotation speed: 19,000 min -1

[0140] Feed rate: 950 mm / min

[0141] Axial cut-in depth: 0.05mm

[0142] Radial cut-in depth: 0.05mm

[0143] Coolant: Water-soluble cutting fluid

[0144] [result]

[0145] Figure 5The evaluation results of the gloss of the 0° surface of this embodiment and existing products are shown. Specifically, multiple clear ○ marks are repeatedly arranged along the length of the scale (metal ruler) on the back of the scale (metal ruler) at the top of the figure. The surface with the repeated ○ marks is placed on each processed surface (0° surface), and the appearance of the ○ marks (reflected image) projected onto the processed surface (0° surface) is compared and evaluated. Figure 5 As shown, regarding the 0° surface, in this embodiment, regardless of whether the processing time is 20 minutes or 60 minutes, a surface with excellent gloss, to the extent that a clear reflective image (○ mark) can be visually confirmed, can be obtained. In contrast, in existing products, a surface without gloss cannot be confirmed by a reflective image (○ mark). Furthermore, regarding the 45° surface (the surface processed using the ball-end blade 5), with the processing time set to 20 minutes and a comparison between this embodiment and existing products, it was confirmed that since the ball-end blade 5 is of the same specification, no difference was found between the two. Although not illustrated, both can produce a surface with excellent gloss, to the extent that a clear reflective image can be visually confirmed.

[0146] in addition, Figure 6 This is a graph showing the measurement results of the arithmetic mean roughness Ra of the 0° surface for processing times of 20 minutes and 60 minutes for this embodiment and existing products, respectively. Figure 7 This is a graph showing the measurement results of the arithmetic mean roughness Ra of the 0° and 45° surfaces for a processing time of 20 minutes for this embodiment and existing products.

[0147] like Figure 6 As shown, it is confirmed that the arithmetic mean roughness Ra of the machined surface is smaller in this embodiment compared to existing products.

[0148] In addition, such as Figure 7 As shown, generally, as with existing products, the surface roughness of a 0° surface machined using the transverse cutting edge at the tool tip is greater than the surface roughness of a 45° surface machined using the ball-end cutting edge. However, in this embodiment, as... Figure 7 As shown, both the 45° surface and the 0° surface were confirmed to be good surface roughness. Furthermore, the 0° surface machined using the tool tip with the plane 6 had a better surface roughness than the 45° surface machined using the ball end cutter 5.

[0149] Based on Experimental Example 3, in this embodiment, by setting the plane 6 at the front end of the tool in a structure where the central side cutting edge 7 is set near the tool rotation axis a, even when machining a plane perpendicular to the tool rotation axis a using the front end of the tool, a machining surface with the same or better gloss as the machining surface using the ball end cutting edge 5 can be obtained.

[0150] Furthermore, the present invention is not limited to this embodiment, and the specific configuration of each component can be appropriately designed.

Claims

1. A ball end mill, comprising a plurality of chip discharge grooves formed on the outer periphery of the tool body, opening at the front end and extending from the front end side towards the base end side, wherein ball-end cutting edges are respectively provided at the intersection of the rake face of the chip discharge groove and the front clearance face of the tool body, characterized in that, The ball end mill has a plane at the front end of the tool that is perpendicular to the tool rotation axis of the tool body. The intersection of this plane and the rake face forms a central side cutting edge that is connected to the ball end cutting edge. The plane is configured to slide in contact with the cutting surface after being cut by the central side cutting edge.

2. The ball end mill according to claim 1, characterized in that, The plane is connected to the front flank face and the front face of each of the pair of ball-end cutting edges that are symmetrically arranged 180 degrees relative to the tool's rotation axis.

3. The ball end mill according to claim 1, characterized in that, The central side cutting edge is positioned near the tool's rotation axis.

4. The ball end mill according to claim 2, characterized in that, The central side cutting edge is positioned near the tool's rotation axis.

5. The ball end mill according to any one of claims 1 to 4, characterized in that, The plane is connected to the front end flank face. Furthermore, this plane can be configured in any way as follows: when viewed from the tool tip, if the ball-end cutting edge connected to the center-side cutting edge is designated as the positive side and its opposite side as the negative side, with the perpendicular line from the perpendicular line to the center-side cutting edge passing through the tool's rotation axis or the perpendicular line from the extension of the center-side cutting edge, then the intersection point P2 exists on the negative side, or on the positive side where the distance between the intersection point P1 and the intersection point P2 along the direction of the center-side cutting edge is 0% to 10% of the tool's outer diameter D. Wherein, the intersection point P1 is the intersection of the center-side cutting edge or the extension line of the center-side cutting edge when viewed from the front end of the tool, and the perpendicular line of the center-side cutting edge or the perpendicular line of the extension line of the center-side cutting edge passing through the rotation axis of the tool; the intersection point P2 is the intersection of the edge line formed by the plane and the front flank face when viewed from the front end of the tool, on the side away from the ball end edge, and the edge of the front end of the chip discharge groove having the ball end edge and the center-side cutting edge connected to the ball end edge.

6. The ball end mill according to any one of claims 1 to 4, characterized in that, In the plane, when viewed from the front end of the tool, the symmetrical interval between the two edges formed by the plane and the respective front flank faces of a pair of ball-end cutting edges that are symmetrically arranged 180 degrees relative to the tool's rotation axis is defined as the width W of the plane. The width W is set to 0.005mm ≤ W ≤ 0.2D, where D is the outer diameter of the tool.

7. The ball end mill according to claim 5, characterized in that, In the plane, when viewed from the front end of the tool, the symmetrical interval between the two edges formed by the plane and the respective front flank faces of a pair of ball-end cutting edges that are symmetrically arranged 180 degrees relative to the tool's rotation axis is defined as the width W of the plane. The width W is set to 0.005mm ≤ W ≤ 0.2D, where D is the outer diameter of the tool.

8. The ball end mill according to claim 6, characterized in that, When the outer diameter of the tool D > Φ1.5mm, the width W of the plane is set to 0.01mm ≤ W ≤ 0.3mm. When the outer diameter of the tool is D≤Φ1.5mm, the width W of the plane is set to 0.01mm≤W≤0.2D.

9. The ball end mill according to claim 7, characterized in that, When the outer diameter of the tool D > Φ1.5mm, the width W of the plane is set to 0.01mm ≤ W ≤ 0.3mm. When the outer diameter of the tool is D≤Φ1.5mm, the width W of the plane is set to 0.01mm≤W≤0.2D.

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