Cutting insert

Abstract

To provide a technique for suppressing damage in a cutting insert.SOLUTION: A cutting insert having a polygonal plate shape, a front face as at least one polygonal surface, and a lateral face arranged around the front face as a flank is such that: a cutting edge is formed in a crossing ridge line of the front face and the flank; a corner blade is formed in the corner part of the front face; a main cutting edge continuous from the corner blade to the crossing ridge line is formed; a sub-cutting edge continuous from the other end of the corner blade to the crossing ridge line is formed; a rake face connected to the main cutting edge and the sub-cutting edge, and going toward the rear face as being separated from the corner blade and the main cutting edge is formed; a breaker surface connected to the rake face and projecting so as to be away from the rear face as being separated from the main cutting edge is formed; and the breaker surface has a raised surface formed, having a curve surface shape, raised from the sub-cutting edge, and connected to the breaker surface and the flank, and is gradually increased as a rake angle viewed in a cross section perpendicular to the main cutting edge is separated from the corner blade.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a cutting insert. [Background technology]

[0002] Cutting inserts in which a cutting edge is formed on the intersecting ridge between the rake face and the flank face have been known for some time (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 6903858 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, even with prior art such as Patent Document 1, there was still room for improvement in techniques for suppressing damage to cutting inserts. For example, in the technology disclosed in Patent Document 1, the rake face is a cylindrical surface with a constant rake angle. However, when the rake angle is small, chips generated by cutting tend to weld to the rake face, and if the chips welded to the rake face fall off due to vibration or the like, there is a risk that the rake face to which the chips were welded may chip. Also, when the rake angle is large, chips are less likely to weld to the rake face, but the strength of the cutting edge decreases. Therefore, there is a risk that the cutting edge may be damaged.

[0005] The present invention aims to provide a technology for suppressing damage in cutting inserts. [Means for solving the problem]

[0006] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in the following forms.

[0007] (1) According to one embodiment of the present invention, a cutting insert is provided. The cutting insert is in the shape of a polygonal plate, with at least one polygonal surface as the surface and the sides arranged around the surface as relief surfaces, a cutting edge is formed on the intersecting ridge between the surface and the relief surface, a corner cutting edge is formed at the corner of the surface, a main cutting edge is formed extending from the corner cutting edge to the intersecting ridge, a secondary cutting edge is formed extending from the other end of the corner cutting edge to the intersecting ridge, and the main cutting edge and the secondary cutting edge are formed so as they move away from the corner cutting edge they face the back surface. The blade is connected to the main cutting edge and the sub-cutting edge, and a rake surface is formed that faces the back surface as it moves away from the corner cutting edge and the main cutting edge. A breaker surface is formed that is connected to the rake surface and protrudes away from the back surface as it moves away from the main cutting edge. The breaker surface is curved and rises from the sub-cutting edge, and a rising surface is formed that connects the breaker surface and the relief surface. The rake angle viewed in a cross section perpendicular to the main cutting edge gradually increases as it moves away from the corner cutting edge.

[0008] In this configuration, the rake angle of the rake face, viewed in a cross-section perpendicular to the main cutting edge, gradually increases as it moves away from the corner cutting edge. This results in a relatively thicker wall thickness near the corner cutting edge, thereby improving the strength of the main cutting edge. Therefore, even if chips become trapped between the cutting insert and the workpiece, damage to the cutting insert can be suppressed. Furthermore, the rake angle of the rake face, viewed in a cross-section perpendicular to the main cutting edge, gradually increases as it moves away from the corner cutting edge. Therefore, as the distance from the corner cutting edge increases, chips are less likely to weld to the rake face. This improves the resistance of the rake face to welding, thereby suppressing damage to the main cutting edge due to the detachment of welded chips. In addition, both the main and secondary cutting edges are formed to curve toward the back surface as they move away from the corner cutting edge. This reduces cutting resistance at the main cutting edge and reduces chip contact with the secondary cutting edge, thereby suppressing damage to the cutting edge. Furthermore, since the breaker surface is formed in a curved shape, chip flow can be controlled to suppress entanglement and reduce damage to the cutting insert. In addition, since a rising surface is formed that is continuous with the breaker surface and the relief surface, the contact area between the chip and the cutting insert increases, which alleviates stress concentration and suppresses damage to the cutting insert.

[0009] (2) In the cutting insert of the above form, the rake angle as viewed in a cross section perpendicular to the main cutting edge may change in a range from positive 5 degrees to positive 17 degrees as it moves away from the corner cutting edge. With this configuration, the rake angle of the rake face as viewed in a cross section perpendicular to the main cutting edge changes in a range from positive 5 degrees to positive 17 degrees as it moves away from the corner cutting edge. As a result, the main cutting edge has relatively high strength near the corner cutting edge, while chips are less likely to weld to the rake face as it moves away from the corner cutting edge. Therefore, damage to the main cutting edge can be further suppressed.

[0010] (3) In the cutting insert of the above form, the distance from the main cutting edge to the edge of the breaker surface, as viewed in a cross section perpendicular to the main cutting edge, may be 0.3 mm to 0.42 mm. With this configuration, since the distance from the main cutting edge to the edge of the breaker surface is a certain distance, chips can be processed properly. This suppresses chip entanglement and prevents damage to the cutting insert.

[0011] (4) In the cutting insert of the above form, the polygonal surface may be formed as a triangle or a quadrilateral. With this configuration, the shape of the cutting insert is a triangle with three ends capable of forming cutting edges, or a quadrilateral with four ends capable of forming cutting edges. As a result, one cutting insert can have multiple cutting edges, and thus a relatively long machining process can be performed with one cutting insert. Therefore, the cost required for machining can be reduced.

[0012] (5) In the above-described cutting insert, cutting edges may be formed on both sides of the polygonal plate shape. With this configuration, the cutting insert has cutting edges on both the front and back surfaces. As a result, one cutting insert can have multiple cutting edges, and thus a relatively long machining process can be performed with one cutting insert. Therefore, the cost required for machining can be reduced.

[0013] (6) The cutting insert of the above form may be used in a low-frequency vibration cutting machine. In a low-frequency vibration cutting machine, the amount of cut into the workpiece by the cutting insert changes, so the load acting on the cutting insert tends to change. With the above configuration, the strength of the main cutting edge near the corner edge is improved, so it becomes less susceptible to damage even when used in a low-frequency vibration cutting machine.

[0014] Furthermore, the present invention can be realized in various forms, for example, as an apparatus equipped with a cutting insert, a control method for an apparatus equipped with a cutting insert, a method for manufacturing a cutting insert, a method for using a cutting insert, and so on. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view of the cutting insert of the first embodiment. [Figure 2] This figure illustrates an example of using the cutting insert 1 of the first embodiment. [Figure 3] This is an enlarged view of section AA in Figure 1. [Figure 4]It is a plan view of a cutting insert of the first embodiment. [Figure 5] It is a first partial enlarged view of a cutting insert of the first embodiment. [Figure 6] It is a second partial enlarged view of a cutting insert of the first embodiment. [Figure 7] It is an enlarged view of the B-B portion in FIG. 3. [Figure 8] It is an end view of the cut portion along the C1-C1 line in FIG. 7. [Figure 9] It is an end view of the cut portion along the C2-C2 line in FIG. 7. [Figure 10] It is an end view of the cut portion along the C3-C3 line in FIG. 7. [Figure 11] It is an end view of the cut portion along the C4-C4 line in FIG. 7. [Figure 12] It is an end view of the cut portion along the C5-C5 line in FIG. 7. [Figure 13] It is a schematic diagram explaining a comparative test of a cutting insert. [Figure 14] It is a first figure explaining the result of the first comparative test. [Figure 15] It is a second figure explaining the result of the first comparative test. [Figure 16] It is a first figure explaining the result of the second comparative test. [Figure 17] It is a second figure explaining the result of the second comparative test. <​​​​​​​​​​​​​​​​​​​Figure 1 is a perspective view of the cutting insert 1 of the first embodiment. Figure 2 is a diagram illustrating an example of use of the cutting insert 1 of this embodiment. As shown in Figure 1, the cutting insert 1 has a rhomboid plate shape. The cutting insert 1 is mainly formed from hard materials such as cemented carbide, cermet, and ceramic. In the cutting insert 1, the surface of these hard materials is coated with an oxide, carbide, carbonitride, or nitride (TiN, TiCN, TiAlN, TiAlCrN, AlCrN, etc.) made from a composite material selected from titanium, chromium, aluminum, etc., to a thickness of 1 μm to 4 μm by PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition). The cutting insert 1 of this embodiment is mainly an insert for cutting metals, non-ferrous metals, resins, etc., and is used by being attached to a cutting tool body (holder) 100 as shown in Figure 2. The cutting insert 1 of this embodiment can also be used, for example, in a processing machine that has a low-frequency vibration cutting function. In Figure 1, the thickness direction of the cutting insert 1 is defined as the z-axis direction, the x-axis is defined as the direction perpendicular to the z-axis and passing through the tips of the two ends (nose R portions 6 and 7) with small interior angles in the rhombus shape, and the y-axis is defined as the direction perpendicular to both the z-axis and the x-axis.

[0017] The cutting insert 1 comprises a cutting edge 10, a rake face 20 and a relief face 30 forming the cutting edge 10, a breaker face 40, and a mounting portion 50. For convenience, in the diamond-shaped cutting insert 1, the end of the cutting insert 1 in the x-axis direction that is located on the positive side is designated as the nose radius portion 6, and the end located on the negative side is designated as the nose radius portion 7. Also, the end of the cutting insert 1 in the y-axis direction that is located on the positive side is designated as the intermediate end portion 8, and the end located on the negative side is designated as the intermediate end portion 9.

[0018] The cutting edge 10 is formed on the intersecting ridge line between the surface 1a, which is the positive z-axis side of the cutting insert 1, and the side surface 1b. Specifically, the cutting edge 10 is formed on the intersecting ridge line between the rake face 20 formed on the surface 1a and the relief face 30, which is the side surface 1b adjacent to the rake face 20. In the cutting insert 1 of this embodiment, the cutting edge 10 is located on the central axis of the cutting insert 1. They are formed at diagonal positions across C1. In other words, the cutting insert 1 of this embodiment has two cutting edges 10.

[0019] Figure 3 is an enlarged view of section AA of Figure 1. Figure 4 is a plan view of the cutting insert 1 of this embodiment. The cutting edge 10 includes a corner cutting edge 11, a main cutting edge 12, and a secondary cutting edge 13. The corner cutting edge 11 is formed at the corner of the surface 1a in the nose radius 6 and nose radius 7 of the cutting insert 1, respectively.

[0020] The main cutting edge 12 is formed to extend from one end of the corner cutting edge 11, along the intersecting ridge line between the surface 1a and the side surface 1b, toward either the intermediate end 8 or 9 in the y-axis direction of the cutting insert 1. Specifically, as shown in Figure 4, the main cutting edge 12 formed on the nose R portion 6 of the cutting insert 1 is formed to extend from one end of the corner cutting edge 11 formed on the nose R portion 6 toward the intermediate end 8 on the positive side in the y-axis direction (see Figure 4). The main cutting edge 12 formed on the nose R portion 7 of the cutting insert 1 is formed to extend from one end of the corner cutting edge 11 formed on the nose R portion 7 toward the intermediate end 9 on the negative side in the y-axis direction (see Figure 4).

[0021] Figure 5 is a partially enlarged view of the cutting insert 1 of this embodiment. The diagram in Figure 5 is a partially enlarged view of the portion including the nose R portion 6 when the cutting insert 1 is viewed from the direction opposite to the main cutting edge 12. As shown in Figure 5, the main cutting edge 12 is formed to cut downwards relative to the surface 1a. That is, the main cutting edge 12 is formed to move toward the back surface 1c of the cutting insert 1 as it moves away from the corner cutting edge 11. This reduces the cutting resistance at the main cutting edge 12, and thus suppresses damage to the main cutting edge 12.

[0022] The secondary cutting edge 13 is formed to extend from the other end of the corner cutting edge 11, along the intersecting ridge line between the surface 1a and the side surface 1b, toward either the intermediate end 8 or 9 in the y-axis direction of the cutting insert 1. Specifically, as shown in Figure 4, the secondary cutting edge 13 formed on the nose R portion 6 of the cutting insert 1 is formed to extend from one end of the corner cutting edge 11 formed on the nose R portion 6 toward the intermediate end 9 on the negative side in the y-axis direction. The secondary cutting edge 13 formed on the nose R portion 7 of the cutting insert 1 is formed to extend from one end of the corner cutting edge 11 formed on the nose R portion 7 toward the intermediate end 8 on the positive side in the y-axis direction.

[0023] Figure 6 is a partially enlarged view of the cutting insert 1 of this embodiment. The diagram in Figure 6 is a partially enlarged view of the portion of the cutting insert 1 including the nose radius 6 when viewed from a direction perpendicular to the main cutting edge 12. As shown in Figure 6, the secondary cutting edge 13 is formed to cut downwards relative to the surface 1a. That is, the secondary cutting edge 13 is formed to move toward the back surface 1c of the cutting insert 1 as it moves away from the corner cutting edge 11. As a result, intermittent contact of chips with the nose radius 6 is suppressed in the cutting insert 1, and damage to the nose radius 6 including the secondary cutting edge 13 can be prevented.

[0024] The rake face 20 is formed on the surface 1a side of the cutting insert 1. In this embodiment, two rake faces are formed, aligned with the main cutting edges 12 located diagonally across the central axis C1 of the cutting insert 1. The rake face 20 is the surface over which chips generated by cutting scrape when the cutting insert 1 cuts the workpiece, and is the surface that scoops up the workpiece. In the cutting insert 1 of this embodiment, the rake face 20 is connected to the main cutting edges 12 and the secondary cutting edges 13, and is formed to move towards the back surface 1c of the cutting insert 1 as it moves away from the corner edge 11 and the main cutting edges 12. The rake face 20 has a twisted shape. Details of the shape of the rake face 20 will be described later.

[0025] The flank surface 30 is part of the side surface 1b of the cutting insert 1 and is formed to be in contact with the rake face 20. As a result, the intersecting ridge line of the rake face 20 and the flank surface 30 becomes the cutting edge 10. The flank surface 30 is a surface that allows the cutting insert 1 to move away from the workpiece when cutting the workpiece to avoid interference with it.

[0026] The breaker surface 40 is formed on the opposite side of the cutting edge 10 from the rake face 20. The breaker surface 40 controls the flow of chips removed by the cutting edge 10. The breaker surface 40 of the cutting insert 1 in this embodiment is connected to the rake face 20 and protrudes away from the back surface 1c as it moves away from the main cutting edge 12. The breaker surface 40 in this embodiment has a curved shape. As a result, the flow of chips on the surface 1a of the cutting insert 1 is controlled, so that chip entanglement is suppressed and damage to the cutting insert 1 can be suppressed.

[0027] As shown in Figure 3, the rising surface 41 rises from the secondary cutting edge 13 and is formed to connect to the breaker surface 40 and the relief surface 30. The rising surface 41 has a relatively large contact area between the chips generated during cutting and the cutting insert 1, which can alleviate stress concentration caused by colliding chips. This can suppress damage to the cutting insert 1.

[0028] The mounting portion 50 is positioned approximately in the center of the surface 1a of the cutting insert 1. The mounting portion 50 is formed to protrude from the surface 1a in the positive z-axis direction. A mounting hole 51 is formed in the center of the mounting portion 50 into which a part of the cutting tool body 100 into which the cutting insert 1 is mounted is inserted. The outer circumferential surface 52 of the mounting hole 51 in the mounting portion 50 functions as a seating surface that contacts the bottom surface of the tip seat provided on the tool body when the cutting insert 1 is mounted on the tip seat provided on the tool body.

[0029] Figure 7 is an enlarged view of the BB portion of Figure 4. The enlarged view of the cutting insert 1 shown in Figure 7 is an enlarged view of the nose R portion 6 in the plan view of the cutting insert 1. Now, the features of the cutting insert 1 of this embodiment will be described. In the cutting insert 1, the rake angle of the rake face 20 viewed in a cross section perpendicular to the main cutting edge 12 gradually increases as it moves away from the corner cutting edge 11.

[0030] In this embodiment, when measuring the rake angle of the rake face 20, the position of the rake face 20 is defined as follows. In the plan view shown in Figure 7, a virtual line VL6 is defined that is perpendicular to the virtual line VL12 on the main cutting edge 12 and tangent to the nose R portion 6, and the distance from the virtual line VL6 is defined as the "position of the rake face 20". For example, in the end view of the C3-C3 line cutting section described later, the "position of the rake face 20" corresponds to the value of distance L3. In this embodiment, the rake angle is defined as the angle between the virtual line L1, which is drawn parallel to the back surface 1c in a cross section perpendicular to the main cutting edge 12, and the rake face 20, and tangent to the main cutting edge 12.

[0031] Figure 8 is an end view of the section cut along the C1-C1 line in Figure 7. The end view of the section cut along the C1-C1 line shown in Figure 8 shows the rake angle θ of the rake face 20 at 0.2 mm, which is the position of the rake face 20 at the boundary between the corner blade 11 and the main cutting blade 12. C1 This is shown in Figure 8, where the rake angle θ is shown. C1 This is a positive fifth.

[0032] Figure 9 is an end view of the cutting section along line C2-C2 in Figure 7. The end view of the cutting section along line C2-C2 shown in Figure 9 shows the scraping angle θ of the scraping surface 20 at a position of 0.5 mm of the scraping surface 20 C2 is shown. The scraping angle θ shown in Figure 9 C2 is larger than the scraping angle θ shown in Figure 8 C1 . In the present embodiment, in the end view shown in Figure 9, the distance W2 between the boundary 40a (the end of the breaker surface 40) between the breaker surface 40 and the scraping surface 20 and the main cutting edge 12, that is, the width of the scraping surface 20, is 0.3 mm to 0.42 mm.

[0033] Figure 10 is an end view of the cutting section along line C3-C3 in Figure 7. The end view of the cutting section along line C3-C3 shown in Figure 10 shows the scraping angle θ of the scraping surface 20 at a position of 1.0 mm of the scraping surface 20 C3 is shown. The scraping angle θ shown in Figure 10 C3 is larger than the scraping angle θ shown in Figure 9 C2 and is 17 degrees positive. In the present embodiment, in the end view shown in Figure 10, the distance W3 (the width of the scraping surface 20) between the boundary 40a between the breaker surface 40 and the scraping surface 20 and the main cutting edge 12 is 0.3 mm to 0.42 mm.

[0034] Figure 11 is an end view of the cutting section along line C4-C4 in Figure 7. The end view of the cutting section along line C4-C4 shown in Figure 11 shows the scraping angle θ of the scraping surface 20 at a position of 1.5 mm of the scraping surface 20 C4 is shown. The scraping angle θ shown in Figure 11 C4 is the same size as the scraping angle θ shown in Figure 10 C3 . In the present embodiment, in the end view shown in Figure 11, the distance W4 (the width of the scraping surface 20) between the boundary 40a between the breaker surface 40 and the scraping surface 20 and the main cutting edge 12 is 0.3 mm to 0.42 mm.

[0035] Figure 12 is an end view of the cutting section along line C5-C5 in Figure 6. The end view of the cutting section along line C5-C5 shown in Figure 12 shows the scraping angle θ of the scraping surface 20 at a position of 2.0 mm of the scraping surface 20 C5 is shown. The scraping angle θ shown in Figure 12 C5 is the scraping angle θ shown in Figure 11C4 It is the same size as [another item].

[0036] Thus, the cutting insert 1 of this embodiment is characterized in that, in a cross section perpendicular to the main cutting edge 12, the rake angle θ of the rake face 20 gradually increases as it moves away from the corner cutting edge 11. Specifically, the rake angle as seen in a cross section perpendicular to the main cutting edge 12 is positive 5 degrees when the rake face 20 is at a position of 0.2 mm, and the rake angle gradually increases as the position of the rake face 20 increases, reaching positive 17 degrees when the position of the rake face 20 is at 1.0 mm. Furthermore, in the range of the rake face 20 position from 0.5 mm to 1.5 mm, the cutting insert 1 of this embodiment is characterized in that, in a cross section perpendicular to the main cutting edge 12, the distance between the boundary 40a between the breaker surface 40 and the rake face 20 and the main cutting edge 12 is 0.3 mm to 0.42 mm.

[0037] Figure 13 is a schematic diagram illustrating a comparative test of cutting inserts. Next, the effects of the cutting insert 1 of this embodiment will be explained. Figure 13 shows a schematic diagram of the test apparatus 90 used in the comparative test. In the comparative test of cutting inserts, several samples of cutting inserts with different rake angles are prepared. As shown in Figure 13, the prepared samples S1 are attached to the cutting tool body 100, and actual cutting is performed on the workpiece 91 attached to the test apparatus 90. The experimental conditions in the comparative test are shown below. Workpiece material: SUS316L (material diameter 20mm) Test equipment (machine used): L20-LFV Cutting speed: Vc=80m / min Cut: 1mm Feed rate: 0.05 mm / rev (amplitude ratio Q=0.5, vibration frequency D=0.5) Cutting oil: WET

[0038] As the first comparative test, we will explain the results of comparing the performance differences due to different rake angles. In the first comparative test, under the experimental conditions described above, we compared the fracture resistance and welding resistance of the samples after processing 8 km.

[0039] Figure 14 illustrates the results of the first comparative test. Figure 14 shows photographs of the nose radius, main cutting edge, and secondary cutting edge of two samples with different rake angles after 8 km of machining. In the first comparative test, a sample with a constant rake angle of 7 degrees (hereinafter referred to as "Sample A") and a sample with a constant rake angle of 15 degrees Sample B (hereinafter referred to as "Sample B") was used. The photographs shown in Figure 14 show a photograph of the area around the main cutting edge taken from "side 1" and a photograph of the area around the secondary cutting edge taken from "side 2". In Figure 14, "side 1" refers to approximately the same direction as "the direction from the positive side in the y-axis direction" in the three axes (see Figure 1) of the cutting insert 1 of this embodiment, and "side 2" refers to approximately the same direction as "the direction from the negative side in the y-axis direction". As shown in Figure 14, it was confirmed that chipping occurred around the nose R portion in Sample B, which has a relatively large rake angle. In other words, it was confirmed that a smaller rake angle results in better fracture resistance.

[0040] Figure 15 is the second figure illustrating the results of the first comparative test. Figure 15 shows photographs comparing the chip adhesion, mainly at the main cutting edge, for sample A and sample B. Figure 15 shows photographs of the state "before acid treatment" and photographs of the state "after acid treatment," which better show the degree of chip welding. As shown in Figure 15, it was confirmed that chips welded around the main cutting edge in sample A, which has a relatively small rake angle. In other words, it was confirmed that a larger rake angle resulted in superior resistance to welding.

[0041] As a second comparative test, the damage status of four samples with different rake face shapes after 8 km of machining (the state of damage to the nose radius and the main cutting edge) was compared. The information regarding the rake face shape of each of the four samples used in the second comparative test is as follows. Sample 1: The rake angle is 7 degrees at a position 0.2 mm from the corner cutting edge. The angle increases up to 15 degrees as you move away from the corner cutting edge. Sample 2: Rake angle is constant at 18 degrees Sample 3: Rake angle is constant at 7 degrees Sample 4: Rake angle is constant at 15 degrees

[0042] Figure 16 is the first figure illustrating the results of the second comparative test. Figure 16 shows photographs of the cutting edge for each of the four samples 1 to 4. Similar to Figure 14, the photographs of the cutting edge in Figure 16 are "taken from the side 1" around the main cutting edge and "taken from the side 2" around the secondary cutting edge. From the photographs of the cutting edge in Figure 16, it was confirmed that in sample 2, where the rake angle is constant at 18 degrees, damage occurred across the entire cutting edge. In addition, in sample 4, where the rake angle of the nose radius is 15 degrees, chipping occurred on the corner cutting edge, while in samples 1 and 3, where the rake angle of the nose radius is 7 degrees, damage was suppressed. On the other hand, in sample 3, where the rake angle is constant at 7 degrees, chipping occurred on the main cutting edge. In sample 1, where the rake angle gradually increases from 7 degrees at the corner cutting edge to 15 degrees at the main cutting edge, it was confirmed that chipping and chipping were suppressed across the entire cutting edge.

[0043] Figure 17 is a second figure illustrating the results of the second comparative test. Figure 17 shows the chipping resistance at the corner and main cutting edges for each of the four samples 1 to 4. As shown in Figure 17, sample 2, with a constant rake angle of 18 degrees, exhibits low chipping resistance because chipping occurs at both the corner and main cutting edges. On the other hand, sample 1, where the rake angle increases as the distance from the corner increases, combines the characteristics of both sample 3, which has chipping resistance at the corner, and sample 4, which has chipping resistance at the main cutting edge.

[0044] Figure 18 shows the condition of the cutting edge of three samples with different rake face widths after 8 km of machining, as part of the third comparative test. The information regarding the rake face width of each of the three samples used in the third comparative test is as follows: Sample α: Rake face width 0.3 mm Sample β: Rake face width 0.42 mm Sample γ: Rake face width 0.43 mm Figure 18 shows photographs of the cutting edge of each sample. For each sample, Figure 18 shows photographs taken from the same two directions as the photographs shown in Figure 16. As shown in Figure 18, chipping was observed in sample γ, which has a rake face width of 0.43 mm, while no damage to the cutting edge was observed in sample α, which has a rake face width of 0.3 mm, and sample β, which has a rake face width of 0.42 mm.

[0045] As described above, with the cutting insert 1 of this embodiment, the rake angle of the rake face 20, viewed in a cross-section perpendicular to the main cutting edge 12, gradually increases as it moves away from the corner cutting edge 11. As a result, the wall thickness of the main cutting edge 12 near the corner cutting edge 11 becomes relatively thicker, thereby improving the strength of the main cutting edge 12. Therefore, even if chips get caught between the cutting insert 1 and the workpiece, damage to the cutting insert 1 can be suppressed. Furthermore, since the rake angle of the rake face 20, viewed in a cross-section perpendicular to the main cutting edge 12, gradually increases as it moves away from the corner cutting edge 11, chips become less likely to weld to the rake face 20 as it moves away from the corner cutting edge 11. As a result, the resistance of the rake face 20 to welding is improved, and damage to the main cutting edge 12 due to the detachment of welded chips can be suppressed.

[0046] Furthermore, according to the cutting insert 1 of this embodiment, the main cutting edge 12 and the secondary cutting edge 13 are formed to move toward the back surface 1c of the cutting insert 1 as they move away from the corner cutting edge 11, as shown in Figures 5 and 6. This reduces the cutting resistance at the main cutting edge 12 and reduces contact of chips with the secondary cutting edge 13, thereby suppressing damage to the cutting edge 10.

[0047] Furthermore, according to the cutting insert 1 of this embodiment, the breaker surface 40 is formed in a curved shape. This controls the flow of chips on the surface 1a of the cutting insert 1, thereby suppressing chip entanglement and preventing damage to the cutting insert 1.

[0048] Furthermore, according to the cutting insert 1 of this embodiment, a rising surface 41 is formed that is connected to the breaker surface 40 and the relief surface 30 (see Figure 3). The rising surface 41 has a relatively large contact area between the chips generated during cutting and the cutting insert 1, so stress concentration caused by colliding chips can be mitigated. This makes it possible to suppress damage to the cutting insert 1.

[0049] Furthermore, according to the cutting insert 1 of this embodiment, the rake angle of the rake face 20, as viewed in a cross-section perpendicular to the main cutting edge 12, changes within a range of positive 5 degrees to positive 17 degrees as it moves away from the corner cutting edge 11. As a result, the main cutting edge 12 has relatively high strength near the corner cutting edge 11, while chips are less likely to weld to the rake face 20 as it moves away from the corner cutting edge 11. Therefore, damage to the main cutting edge 12 can be further suppressed.

[0050] Furthermore, according to the cutting insert 1 of this embodiment, the distance from the main cutting edge 12 to the end 40a of the breaker surface 40, as viewed in a cross-section perpendicular to the main cutting edge 12, is 0.3 mm to 0.42 mm. As a result, the rake face 20 has a certain width, allowing for proper chip processing. This suppresses chip entanglement and prevents damage to the cutting insert 1.

[0051] Furthermore, according to the cutting insert 1 of this embodiment, the cutting insert 1 has a rhomboid shape, and cutting edges 10 are formed at diagonal positions across the central axis C1. As a result, one cutting insert 1 can have multiple cutting edges, and thus a relatively long machining process can be performed with one cutting insert 1. Therefore, the cost required for machining is reduced. This can be reduced.

[0052] Furthermore, the cutting insert 1 of this embodiment can be used in a low-frequency vibration cutting machine. In a low-frequency vibration cutting machine, the amount of cut into the workpiece by the cutting insert changes, so the load acting on the cutting insert tends to change. With the cutting insert 1 of this embodiment, the strength of the main cutting edge 12 near the corner edge 11 is improved, so it becomes less susceptible to damage even when used in a low-frequency vibration cutting machine.

[0053] <Second Embodiment> Figure 19 is a perspective view of the cutting insert of the second embodiment. The cutting insert 2 of the second embodiment differs from the cutting insert 1 of the first embodiment (Figure 1) in that it also has cutting edges formed on the back surface.

[0054] Figure 20 is a plan view of the cutting insert 2 of the second embodiment. Figure 21 is a bottom view of the cutting insert 2 of the second embodiment. The cutting insert 2 of the second embodiment comprises a cutting edge 10, a rake face 20 and a relief face 30 forming the cutting edge 10, a breaker face 40, a mounting portion 50, and a mounting portion 60. As shown in the plan view of Figure 20, the cutting insert 2 has two cutting edges 10 on the surface 1a side, and as shown in the bottom view of Figure 21, on the back surface 1c side, there are cutting edges 10 on each of the nose R portions 6 and 7. In other words, the cutting insert 2 has four cutting edges 10.

[0055] The mounting portion 60 is positioned approximately in the center of the back surface 1c of the cutting insert 2 (see Figure 21). The mounting portion 60 is formed to protrude from the back surface 1c in the negative direction of the z-axis. A mounting hole 51 is formed in the center of the mounting portion 60. The outer circumferential surface 62 of the mounting hole 51 in the mounting portion 60 functions as a seating surface that contacts the bottom surface of the chip seat provided on the tool body when the insert is mounted on the chip seat provided on the tool body.

[0056] As described above, the cutting insert 2 of this embodiment has two cutting edges 10 formed on both the surface 1a and the back surface 1c. This allows a single cutting insert 2 to have multiple cutting edges 10, enabling relatively long machining operations with a single cutting insert 2. Therefore, the cost of machining can be reduced.

[0057] <Modified form of this embodiment> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit, for example, the following modifications are also possible.

[0058] [Example 1] In the embodiments described above, the cutting inserts 1 and 2 were assumed to have a rhomboid shape. However, the shape of the cutting inserts is not limited to this. They may also be triangular or have a quadrilateral shape other than a rhomboid.

[0059] [Differentiation 2] In the above embodiment, the rake angle of the rake face 20 is assumed to gradually increase from positive 5 degrees to positive 17 degrees. The change in the rake angle is not limited to this. The rake angle should gradually increase as it moves away from the corner cutting edge along the main cutting edge. The size of the rake angle may be, for example, in the range of 8 degrees to 12 degrees, but is preferably in the range of 6 degrees to 16 degrees, and more preferably in the range of 7 degrees to 15 degrees. This makes it possible to improve the welding resistance of the rake face while improving the strength of the main cutting edge near the corner cutting edge.

[0060] [Difference 3] In the above embodiment, the distance between the boundary 40a between the breaker surface 40 and the rake face 20 and the main cutting edge 12, i.e., the width of the rake face 20, was set to 0.3 mm to 0.42 mm. However, the width of the rake face 20 is not limited to this. By setting the width of the rake face 20 to 0.3 mm to 0.42 mm, chip entanglement can be suppressed, and damage to the cutting insert can be suppressed. Preferably, the width of the rake face 20 is 0.33 mm to 0.42 mm, and more preferably 0.35 mm to 0.40 mm. By setting the width of the rake face 20 within these numerical ranges, damage to the cutting insert can be further suppressed.

[0061] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0062] (Application Example 1) A cutting insert having a polygonal plate shape, with at least one polygonal surface as its front surface, and side surfaces arranged around the front surface as relief surfaces, and a cutting edge formed on the intersecting ridge between the front surface and the relief surface, Corner cutting edges are formed at the corners of the surface, a main cutting edge is formed extending from the corner cutting edge to the intersecting ridge, and a secondary cutting edge is formed extending from the other end of the corner cutting edge to the intersecting ridge. The main cutting edge and the secondary cutting edge are formed to move toward the back surface as they move away from the corner cutting edge. The main cutting edge and the secondary cutting edge are connected, and as the corner cutting edge moves away from the main cutting edge, a rake surface is formed toward the back surface. A breaker surface is formed that is connected to the rake surface and protrudes away from the back surface as it moves away from the main cutting edge, and the breaker surface is curved. A rising surface is formed that extends from the secondary cutting edge and connects to the breaker surface and the relief surface. A cutting insert in which the rake angle, viewed in a cross-section perpendicular to the main cutting edge, gradually increases as it moves away from the corner cutting edge. (Application Example 2) The cutting insert according to Application Example 1, wherein the rake angle viewed in a cross-section perpendicular to the main cutting edge changes in a range from positive 5 degrees to positive 17 degrees as it moves away from the corner cutting edge. (Application Example 3) A cutting insert according to Application Example 1 or Application Example 2, wherein the distance from the main cutting edge to the edge of the breaker surface, as viewed in a cross-section perpendicular to the main cutting edge, is 0.3 mm to 0.42 mm. (Application Example 4) The aforementioned polygonal surface is formed as a triangle or a quadrilateral, as described in any one of Application Examples 1 to 3, for the cutting insert. (Application Example 5) A cutting insert according to any one of Application Examples 1 to 4, having cutting edges formed on both sides of a polygonal plate shape. (Application Example 6) A cutting insert described in any one of Application Examples 1 to 5, which can be used in a low-frequency vibration cutting machine. [Explanation of symbols]

[0063] 1, 2… Cutting inserts 1a…Surface 1b…side 1c…Back side 6, 7... corners 10…Cutting edge 11...Corner blade 12…Main cutting edge 13…Sub-cutting edge 20... Scoop surface 30...Fleeing face 40... Breaker side 41…Rising surface

Claims

1. A cutting insert having a polygonal plate shape, with at least one polygonal surface as the surface, and the sides arranged around the surface as relief surfaces, and a cutting edge formed on the intersecting ridge between the surface and the relief surface, Corner cutting edges are formed at the corners of the surface, a main cutting edge is formed extending from the corner cutting edge to the intersecting ridge, and a secondary cutting edge is formed extending from the other end of the corner cutting edge to the intersecting ridge. The main cutting edge and the secondary cutting edge are formed such that, as they move away from the corner cutting edge, they face toward the back surface, which is located opposite to the front surface relative to the side surface. The main cutting edge and the secondary cutting edge are connected, and as the corner cutting edge moves away from the main cutting edge, a rake surface is formed toward the back surface. A breaker surface is formed that is connected to the rake surface and protrudes away from the back surface as it moves away from the main cutting edge, and the breaker surface has a concave curved shape in the direction away from the main cutting edge. A rising surface is formed that extends from the secondary cutting edge and connects to the breaker surface and the relief surface. A cutting insert in which the rake angle, viewed in a cross-section perpendicular to the main cutting edge, gradually increases as it moves away from the corner cutting edge, and then becomes constant.

2. A second virtual line (VL6) is defined which is perpendicular to a first virtual line (VL12) on the main cutting edge and is tangent to the nose R portion of the cutting insert, and the distance from the second virtual line to a point on the main cutting edge is defined as the position of the rake face at that point, The rake angle, as viewed in a cross-section perpendicular to the main cutting edge, changes from positive 5 degrees to positive 17 degrees as the rake face is separated from the corner cutting edge, within a range of 0.2 mm to 1.0 mm. The cutting insert according to claim 1, wherein the distance from the main cutting edge to the end of the breaker surface, as viewed in a cross section perpendicular to the main cutting edge, is 0.3 mm to 0.42 mm when the position of the rake face is in the range of 0.5 mm to 1.5 mm.

3. The cutting insert according to claim 1 or claim 2, wherein the polygonal surface is formed in the shape of a triangle or a quadrilateral.

4. A cutting insert according to claim 3, wherein cutting edges are formed on both sides of a polygonal plate shape.

5. A cutting insert according to claim 1 or claim 2, which can be used in a low-frequency vibration cutting machine.

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