JP2024068002A - Cutting Insert - Google Patents

Abstract

[Problem] To provide a technology for suppressing damage to a cutting insert. [Solution] The cutting insert is in the form of a polygonal plate, with at least one polygonal surface as the surface and side surfaces arranged around the surface as flank surfaces, a cutting edge is formed on the intersecting ridge between the surface and the flank surface, a corner edge is formed at the corner of the surface, a main cutting edge is formed from the corner edge to the intersecting ridge, a minor cutting edge is formed from the other end of the corner edge to the intersecting ridge, a rake face is formed that is connected to the main cutting edge and the minor cutting edge and faces the back surface as it moves away from the corner edge and the main cutting edge, a breaker face is formed that is connected to the rake face and protrudes away from the back surface as it moves away from the main cutting edge, the breaker face is curved, and a rising face is formed that rises from the minor cutting edge and is connected to the breaker face and the flank surface, and the rake angle as viewed in a cross section perpendicular to the main cutting edge gradually increases as it moves away from the corner edge. [Selected Figure] Figure 1

Description

The present invention relates to a cutting insert.

Conventionally, cutting inserts have been known in which a cutting edge is formed at the intersection ridge between the rake face and the flank face (see, for example, Patent Document 1).

Japanese Patent No. 6903858

However, even with prior art such as that of Patent Document 1, there is still room for improvement in the technology 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 are easily welded 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 be chipped. Also, when the rake angle is large, chips are less likely to weld to the rake face, but the strength of the cutting edge is reduced. As a result, there is a risk of the cutting edge being damaged.

The present invention aims to provide a technology that suppresses damage to cutting inserts.

The present invention has been made to solve at least some of the above problems, and can be realized in the following forms:

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

According to this configuration, the rake angle of the rake face as viewed in a cross section perpendicular to the main cutting edge gradually increases as it moves away from the corner edge. As a result, the thickness of the main cutting edge near the corner edge becomes relatively thick, and the strength of the main cutting edge can be improved. Therefore, even if chips are caught between the cutting insert and the workpiece, damage to the cutting insert can be suppressed. In addition, the rake angle of the rake face as viewed in a cross section perpendicular to the main cutting edge gradually increases as it moves away from the corner edge, and therefore chips are less likely to adhere to the rake face as it moves away from the corner edge. As a result, the adhesion resistance of the rake face is improved, and damage to the main cutting edge due to the falling off of the welded chips can be suppressed. In addition, each of the main cutting edge and the minor cutting edge is formed so as to move toward the back surface as it moves away from the corner edge. As a result, the cutting resistance of the main cutting edge can be reduced, and the contact of chips with the minor cutting edge can be reduced, and therefore damage to the cutting edge can be suppressed. Furthermore, since the breaker face is formed in a curved shape, it is possible to control the flow of the chips and suppress the entrainment of the chips, thereby suppressing damage to the cutting insert. Also, since a rising surface that is continuous with the breaker face and the flank face is formed, the contact area between the chips and the cutting insert is increased, which alleviates stress concentration and suppresses damage to the cutting insert.

(2) In the cutting insert of the above embodiment, 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 edge. According to 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 edge. As a result, the main cutting edge has a relatively high strength near the corner edge, while chips are less likely to adhere to the rake face as it moves away from the corner edge. Therefore, damage to the main cutting edge can be further suppressed.

(3) In the cutting insert of the above embodiment, the distance from the main cutting edge to the end of the breaker surface in a cross section perpendicular to the main cutting edge may be 0.3 mm to 0.42 mm. With this configuration, the distance from the main cutting edge to the end of the breaker surface is a certain distance, so that chips can be properly processed. This can prevent chips from being caught and damage to the cutting insert.

(4) In the cutting insert of the above embodiment, the polygonal surface may be formed as a triangle or a rectangle. According to this configuration, the shape of the cutting insert is a triangle having three ends capable of forming cutting edges, or a rectangle having four ends capable of forming cutting edges. This allows one cutting insert to have multiple cutting edges, so that a relatively long machining can be performed with one cutting insert. Therefore, the cost required for cutting processing can be reduced.

(5) In the cutting insert of the above embodiment, cutting edges may be formed on both sides of the polygonal plate. According to this configuration, the cutting insert has cutting edges formed on both the front and back surfaces. This allows one cutting insert to have multiple cutting edges, so that one cutting insert can perform a relatively long machining process. Therefore, the cost required for cutting processing can be reduced.

(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 load acting on the cutting insert is likely to change because the size of the cut made by the cutting insert into the workpiece changes. With the above-mentioned configuration, the strength of the main cutting edge near the corner edge is improved, making it less susceptible to damage even when used in a low-frequency vibration cutting machine.

The present invention can be realized in various forms, such as a device equipped with a cutting insert, a control method for a device equipped with a cutting insert, a manufacturing method for a cutting insert, a method for using a cutting insert, etc.

FIG. 2 is a perspective view of the cutting insert of the first embodiment. 1A to 1C are diagrams illustrating an example of use of the cutting insert 1 according to the first embodiment. FIG. 2 is an enlarged view of a portion AA of FIG. FIG. 2 is a plan view of the cutting insert of the first embodiment. FIG. 2 is a first partially enlarged view of the cutting insert of the first embodiment. FIG. 4 is a second partially enlarged view of the cutting insert of the first embodiment. FIG. 4 is an enlarged view of the BB portion of FIG. 8 is an end view of the cross section taken along line C1-C1 in FIG. 7. 8 is an end view of the cross section taken along line C2-C2 in FIG. 7. 8 is an end view of the cross section taken along line C3-C3 in FIG. 7. 8 is an end view of the cross section taken along line C4-C4 in FIG. 7. 8 is an end view of the cross section taken along line C5-C5 in FIG. 7. FIG. 1 is a schematic diagram illustrating a comparative test of cutting inserts. FIG. 11 is a first diagram illustrating the results of a first comparison test. FIG. 11 is a second diagram illustrating the results of the first comparative test. FIG. 11 is a first diagram illustrating the results of a second comparative test. FIG. 13 is a second diagram illustrating the results of the second comparative test. FIG. 13 is a diagram illustrating the results of a third comparative test. FIG. 11 is a perspective view of a cutting insert according to a second embodiment. FIG. 11 is a plan view of a cutting insert according to a second embodiment. FIG. 11 is a bottom view of the cutting insert of the second embodiment.

First Embodiment
FIG. 1 is a perspective view of a cutting insert 1 of a first embodiment. FIG. 2 is a diagram for explaining an example of use of the cutting insert 1 of this embodiment. As shown in FIG. 1, the cutting insert 1 has a rhombic plate shape. The cutting insert 1 is mainly formed of hard materials such as cemented carbide, cermet, and ceramic. In the cutting insert 1, the surface of these hard materials is coated with oxides, carbides, carbonitrides, and nitrides (TiN, TiCN, TiAlN, TiAlCrN, AlCrN, etc.) made of composite materials selected from titanium, chromium, aluminum, etc., with a film thickness (single layer or multiple layers) of 1 μm to 4 μm by PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition). The cutting insert 1 of this embodiment is an insert for cutting mainly metals, non-ferrous metals, resins, etc., and is attached to a cutting tool body (holder) 100 for use as shown in FIG. 2. The cutting insert 1 of this embodiment can also be used in a processing machine having a low-frequency vibration cutting function, for example. In Fig. 1, the thickness direction of the cutting insert 1 is the z-axis direction, the direction perpendicular to the z-axis and passing through the tip portions of the two ends (nose R portions 6, 7) with small interior angles in the diamond shape is the x-axis, and the direction perpendicular to the z-axis and perpendicular to the x-axis is the y-axis.

The cutting insert 1 includes a cutting edge 10, a rake face 20 and a clearance face 30 that form the cutting edge 10, a breaker face 40, and an attachment portion 50. For convenience, in the diamond-shaped cutting insert 1, the end located on the positive side of the x-axis direction of the cutting insert 1 is referred to as the nose R portion 6, and the end located on the negative side is referred to as the nose R portion 7. In addition, the end located on the positive side of the y-axis direction of the cutting insert 1 is referred to as the middle end 8, and the end located on the negative side is referred to as the middle end 9.

The cutting edge 10 is formed on the intersection ridge between the front surface 1a, which is the surface on the positive side of the z-axis, and the side surface 1b of the cutting insert 1. Specifically, the cutting edge 10 is formed on the intersection ridge between the rake face 20 formed on the front surface 1a and the flank face 30, which is the side surface 1b adjacent to the rake face 20. In the cutting insert 1 of this embodiment, the cutting edges 10 are formed at diagonal positions across the central axis C1 of the cutting insert 1. That is, the cutting insert 1 of this embodiment has two cutting edges 10.

Figure 3 is an enlarged view of the A-A portion of Figure 1. Figure 4 is a plan view of the cutting insert 1 of this embodiment. The cutting edge 10 includes a corner edge 11, a major cutting edge 12, and a minor cutting edge 13. The corner edge 11 is formed at the corner of the surface 1a in each of the nose R portion 6 and the nose R portion 7 of the cutting insert 1.

The main cutting edge 12 is formed so as to extend from one end of the corner edge 11 to the intersection ridge between the surface 1a and the side surface 1b and toward one of the intermediate ends 8, 9 in the y-axis direction of the cutting insert 1. Specifically, as shown in FIG. 4, the main cutting edge 12 formed in the nose R portion 6 of the cutting insert 1 is formed so as to extend from one end of the corner edge 11 formed in the nose R portion 6 toward the intermediate end 8 on the positive side in the y-axis direction (see FIG. 4). The main cutting edge 12 formed in the nose R portion 7 of the cutting insert 1 is formed so as to extend from one end of the corner edge 11 formed in the nose R portion 7 toward the intermediate end 9 on the negative side in the y-axis direction (see FIG. 4).

Figure 5 is a partially enlarged view of the cutting insert 1 of this embodiment. The view shown in Figure 5 is a partially enlarged view of a portion including the nose R portion 6 when the cutting insert 1 is viewed from a direction facing the main cutting edge 12. As shown in Figure 5, the main cutting edge 12 is formed so as to cut down relative to the front surface 1a. In other words, the main cutting edge 12 is formed so as to move toward the back surface 1c of the cutting insert 1 as it moves away from the corner edge 11. This reduces the cutting resistance of the main cutting edge 12, thereby suppressing damage to the main cutting edge 12.

The minor cutting edge 13 is formed so as to connect from the other end of the corner edge 11 to the intersecting ridge between the surface 1a and the side surface 1b, and extend toward one of the intermediate ends 8, 9 in the y-axis direction of the cutting insert 1. Specifically, as shown in FIG. 4, the minor cutting edge 13 formed in the nose R portion 6 of the cutting insert 1 is formed so as to extend from one end of the corner edge 11 formed in the nose R portion 6 toward the intermediate end 9 on the negative side in the y-axis direction. The minor cutting edge 13 formed in the nose R portion 7 of the cutting insert 1 is formed so as to extend from one end of the corner edge 11 formed in the nose R portion 7 toward the intermediate end 8 on the positive side in the y-axis direction.

Figure 6 is a partially enlarged view of the cutting insert 1 of this embodiment. The view shown in Figure 6 is a partially enlarged view of a portion including the nose R portion 6 when the cutting insert 1 is viewed from a direction perpendicular to the main cutting edge 12. As shown in Figure 6, the minor cutting edge 13 is formed so as to cut down relative to the front surface 1a. In other words, the minor cutting edge 13 is formed so as to move toward the back surface 1c of the cutting insert 1 as it moves away from the corner edge 11. As a result, in the cutting insert 1, intermittent contact of chips with the nose R portion 6 is suppressed, and damage to the nose R portion 6 including the minor cutting edge 13 can be suppressed.

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

The flank 30 is a part of the side surface 1b of the cutting insert 1 and is formed so as to contact the rake face 20. As a result, the intersection ridge between the rake face 20 and the flank 30 forms the cutting edge 10. The flank 30 is a surface that allows the cutting insert 1 to escape so as not to interfere with the workpiece when cutting the workpiece.

The breaker surface 40 is formed on the side of the rake face 20 opposite the cutting edge 10. The breaker surface 40 controls the flow of chips cut off by the cutting edge 10. The breaker surface 40 of the cutting insert 1 of 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 of this embodiment has a curved shape. This controls the flow of chips on the front surface 1a of the cutting insert 1, thereby suppressing chip entrainment and preventing damage to the cutting insert 1.

As shown in FIG. 3, the rising surface 41 rises from the minor cutting edge 13 and is formed to connect to the breaker surface 40 and the flank surface 30. The rising surface 41 provides a relatively large contact area between the cutting insert 1 and the chips generated during cutting, and can therefore reduce stress concentration caused by colliding chips. This can suppress damage to the cutting insert 1.

The mounting portion 50 is disposed approximately in the center of the surface 1a of the cutting insert 1. The mounting portion 50 is formed so as to protrude from the surface 1a in the positive direction of the z-axis. A mounting hole 51 is formed in the center of the mounting portion 50, into which a part of the cutting tool body 100 on which the cutting insert 1 is attached is inserted. The outer peripheral surface 52 of the mounting hole 51 in the mounting portion 50 functions as a seating surface that abuts against the bottom surface of the tip seat when the mounting portion 50 is attached to the tip seat provided on the tool body.

Figure 7 is an enlarged view of the B-B portion of Figure 4. The enlarged view of the cutting insert 1 shown in Figure 7 is a partial enlarged view of the nose R portion 6 in a plan view of the cutting insert 1. Here, 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 as viewed in a cross section perpendicular to the main cutting edge 12 gradually increases as it moves away from the corner edge 11.

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 FIG. 7, a virtual line VL6 is defined as a line 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, the "position of the rake face 20" in the end view of the cut portion taken along line C3-C3, which will be described later, corresponds to the numerical value of the distance L3. In this embodiment, the rake angle is defined as the angle between the virtual line L1 and the rake face 20 when a virtual line parallel to the back surface 1c is drawn tangent to the main cutting edge 12 in a cross section perpendicular to the main cutting edge 12.

Figure 8 is a cross-sectional end view taken along line C1-C1 in Figure 7. The cross-sectional end view taken along line C1-C1 in Figure 8 shows the rake angle θ _{C1 of the rake face 20 when the position of the rake face 20 is 0.2 mm, which is the boundary between the corner edge 11 and the main cutting edge 12. The rake angle θ C1 shown} in Figure 8 is positive 5 degrees.

Fig. 9 is a cross-sectional end view taken along line C2-C2 in Fig. 7. The cross-sectional end view taken along line C2-C2 in Fig. 9 shows the rake angle θ _C2 of the rake face 20 when the position of the rake face 20 is 0.5 mm. The rake angle θ _C2 shown in Fig. 9 is larger than the rake angle θ _C1 shown in Fig. 8. In this embodiment, in the end view shown in Fig. 9, the distance W2 between the boundary 40a (the end of the breaker face 40) between the breaker face 40 and the rake face 20 and the main cutting edge 12, i.e., the width of the rake face 20, is 0.3 mm to 0.42 mm.

Fig. 10 is a cross-sectional end view taken along line C3-C3 in Fig. 7. The cross-sectional end view taken along line C3-C3 in Fig. 10 shows the rake angle θ _C3 of the rake face 20 when the position of the rake face 20 is 1.0 mm. The rake angle θ _C3 shown in Fig. 10 is larger than the rake angle θ _C2 shown in Fig. 9, and is a positive 17 degrees. In this embodiment, in the end view shown in Fig. 10, the distance W3 (width of the rake face 20) between the boundary 40a between the breaker face 40 and the rake face 20 and the main cutting edge 12 is 0.3 mm to 0.42 mm.

Fig. 11 is a cross-sectional end view taken along line C4-C4 in Fig. 7. The cross-sectional end view taken along line C4-C4 in Fig. 11 shows the rake angle θ _C4 of the rake face 20 when the position of the rake face 20 is 1.5 mm. The rake angle θ _C4 shown in Fig. 11 is the same as the rake angle θ _C3 shown in Fig. 10. In this embodiment, in the end view shown in Fig. 11, the distance W4 (width of the rake face 20) between the boundary 40a between the breaker face 40 and the rake face 20 and the main cutting edge 12 is 0.3 mm to 0.42 mm.

Fig. 12 is a cross-sectional end view taken along line C5-C5 in Fig. 6. The cross-sectional end view taken along line C5-C5 in Fig. 12 shows the rake angle θ _C5 of the rake face 20 when the position of the rake face 20 is 2.0 mm. The rake angle θ _C5 shown in Fig. 12 is the same as the rake angle θ _C4 shown in Fig. 11.

In this way, the cutting insert 1 of this embodiment has a feature that the rake angle θ of the rake face 20 in a cross section perpendicular to the main cutting edge 12 gradually increases as it moves away from the corner edge 11. Specifically, the rake angle in a cross section perpendicular to the main cutting edge 12 is positive 5 degrees when the rake face 20 is 0.2 mm away, and gradually increases as the rake face 20 position increases, becoming positive 17 degrees when the rake face 20 is 1.0 mm away. In addition, the cutting insert 1 of this embodiment has a feature that when the rake face 20 position is in the range of 0.5 mm to 1.5 mm, the distance between the boundary 40a between the breaker face 40 and the rake face 20 and the main cutting edge 12 in a cross section perpendicular to the main cutting edge 12 is 0.3 mm to 0.42 mm.

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

As the first comparative test, we will explain the results of comparing the differences in performance due to different rake angles. In the first comparative test, we compared the chipping resistance and adhesion resistance of samples after machining 8 km under the above experimental conditions.

FIG. 14 is a diagram illustrating the results of the first comparative test. In FIG. 14, photographs of the nose R portion, the main cutting edge, and the minor cutting edge at the time of machining 8 km for two samples having different rake angles are shown. 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 (hereinafter referred to as "sample B") were used. The photographs shown in FIG. 14 show a photograph of the periphery of the main cutting edge "taken from side 1" and a photograph of the periphery of the minor cutting edge "taken from side 2". In addition, "side 1" in FIG. 14 refers to the direction approximately the same as the "direction from the positive side of the y-axis direction" in the three axes of the cutting insert 1 of this embodiment (see FIG. 1), and "side 2" refers to the direction approximately the same as the "direction from the negative side of the y-axis direction". As shown in FIG. 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 the smaller the rake angle, the better the chipping resistance.

Figure 15 is the second figure explaining the results of the first comparison test. Figure 15 shows photographs comparing the state of chip adhesion mainly on the main cutting edge for each of sample A and sample B. Figure 15 shows a photograph showing the state "before acid treatment" and a photograph showing the state "after acid treatment" in which the degree of chip adhesion can be more clearly seen. As shown in Figure 15, it was confirmed that chips were welded around the main cutting edge in sample A, which has a relatively small rake angle. In other words, it was confirmed that the larger the rake angle, the better the resistance to adhesion.

In the second comparative test, the damage state of the samples (the state of chipping of the nose R portion and the main cutting edge) at the time of machining 8 km was compared for four samples with different shapes of the rake face. The information on the shape of the rake face for 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 edge.
As it moves away from the corner edge, it increases up to 15 degrees.
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.

Figure 16 is the first diagram explaining the results of the second comparative test. In Figure 16, photographs of the cutting edges are shown for each of the four samples 1 to 4. The photographs of the cutting edges shown in Figure 16 are, like those in Figure 14, photographs of the periphery of the main cutting edge taken from "side 1" and photographs of the periphery of the minor cutting edge taken from "side 2". From the photographs of the cutting edges shown in Figure 16, it was confirmed that in sample 2, which has a constant rake angle of 18 degrees, damage occurs to the entire cutting edge. In addition, in sample 4, which has a rake angle of 15 degrees at the nose R portion, damage occurs to the corner edge, while in samples 1 and 3, which have rake angles of 7 degrees at the nose R portion, damage is suppressed. On the other hand, in sample 3, which has a constant rake angle of 7 degrees, chipping occurs in the main cutting edge. It was confirmed that in sample 1, where the rake angle gradually increases from 7 degrees at the corner edge to 15 degrees at the main cutting edge, chipping and chipping are suppressed throughout the entire cutting edge.

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

In the third comparative test, three samples with different cutting face widths were compared in terms of the cutting edge state after 8 km of machining. The information on the cutting face width for each of the three samples used in the third comparative test is as follows:
Sample α: width of rake face 0.3 mm
Sample β: width of rake face 0.42 mm
Sample γ: width of rake face 0.43 mm
Fig. 18 shows photographs of the cutting edge of each sample. For each sample, Fig. 18 shows photographs taken from the same two directions as the photographs shown in Fig. 16. As shown in Fig. 18, chipping was observed in sample γ with a rake face width of 0.43 mm, while no damage to the cutting edge was observed in sample α with a rake face width of 0.3 mm and sample β with a rake face width of 0.42 mm.

According to the cutting insert 1 of this embodiment described above, the rake angle of the rake face 20 in a cross section perpendicular to the main cutting edge 12 gradually increases as it moves away from the corner edge 11. As a result, the thickness of the main cutting edge 12 near the corner edge 11 becomes relatively thick, and the strength of the main cutting edge 12 can be improved. Therefore, even if chips are caught between the cutting insert 1 and the workpiece, damage to the cutting insert 1 can be suppressed. In addition, the rake angle of the rake face 20 in a cross section perpendicular to the main cutting edge 12 gradually increases as it moves away from the corner edge 11, so that chips are less likely to adhere to the rake face 20 as it moves away from the corner edge 11. As a result, the adhesion resistance of the rake face 20 is improved, and damage to the main cutting edge 12 due to the falling off of welded chips can be suppressed.

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

In addition, according to the cutting insert 1 of this embodiment, the breaker surface 40 is formed in a curved shape. This makes it possible to control the flow of chips on the surface 1a of the cutting insert 1, thereby suppressing chip entrapment and preventing damage to the cutting insert 1.

In addition, according to the cutting insert 1 of this embodiment, a rising surface 41 is formed that is continuous with the breaker surface 40 and the flank surface 30 (see FIG. 3). The rising surface 41 provides a relatively large contact area between the cutting insert 1 and the chips generated during cutting, and therefore can reduce stress concentration caused by the colliding chips. This can suppress damage to the cutting insert 1.

In addition, 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 in the range from positive 5 degrees to positive 17 degrees as it moves away from the corner edge 11. As a result, the main cutting edge 12 has a relatively high strength near the corner edge 11, while chips are less likely to adhere to the rake face 20 as it moves away from the corner edge 11. Therefore, damage to the main cutting edge 12 can be further suppressed.

In addition, with the cutting insert 1 of this embodiment, the distance from the main cutting edge 12 to the end 40a of the breaker face 40 in a cross section perpendicular to the main cutting edge 12 is 0.3 mm to 0.42 mm. This allows the rake face 20 to have a certain width, allowing chips to be processed normally. This prevents chips from being caught and damage to the cutting insert 1.

Moreover, according to the cutting insert 1 of this embodiment, the cutting insert 1 has a rhombus shape, and cutting edges 10 are formed at diagonal positions across the central axis C1. As a result, one cutting insert 1 can have a plurality of cutting edges, so that a relatively long machining can be performed with one cutting insert 1. Therefore, the cost required for cutting processing can be reduced.

The cutting insert 1 of this embodiment can also be used in a low-frequency vibration cutting machine. In a low-frequency vibration cutting machine, the load acting on the cutting insert is likely to change because the size of the cut into the workpiece by the cutting insert changes. With the cutting insert 1 of this embodiment, the strength of the main cutting edge 12 near the corner edge 11 is improved, making it less susceptible to damage even when used in a low-frequency vibration cutting machine.

Second Embodiment
19 is a perspective view of a cutting insert according to a second embodiment. A cutting insert 2 according to the second embodiment is different from the cutting insert 1 according to the first embodiment (FIG. 1) in that a cutting edge is also formed on the back surface.

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 includes a cutting edge 10, a rake face 20 and a flank face 30 that form the cutting edge 10, a breaker face 40, an attachment portion 50, and an attachment portion 60. As shown in the plan view of Figure 20, the cutting insert 2 includes two cutting edges 10 on the front surface 1a side, and as shown in the bottom view of Figure 21, the cutting insert 2 includes cutting edges 10 on each of the nose R portions 6 and 7 on the back surface 1c side. That is, the cutting insert 2 includes four cutting edges 10.

The mounting portion 60 is disposed approximately in the center of the back surface 1c of the cutting insert 2 (see FIG. 21). The mounting portion 60 is formed so as 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 peripheral surface 62 of the mounting hole 51 in the mounting portion 60 functions as a seating surface that abuts against the bottom surface of the tip seat when the mounting portion 60 is attached to the tip seat provided on the tool body.

As described above, according to the cutting insert 2 of this embodiment, two cutting edges 10 are formed on each of the front surface 1a and the back surface 1c. This allows one cutting insert 2 to have multiple cutting edges 10, so that one cutting insert 2 can perform machining for a relatively long period of time. This reduces the cost required for cutting processing.

<Modifications of this embodiment>
The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit and scope of the invention. For example, the following modifications are also possible.

[Modification 1]
In the above-described embodiment, the cutting inserts 1 and 2 have a rhombus shape. However, the shape of the cutting insert is not limited to this. The cutting insert may have a triangular shape or a rectangular shape other than a rhombus shape.

[Modification 2]
In the above embodiment, the rake angle of the rake face 20 gradually increases from positive 5 degrees to positive 17 degrees. The change in the rake angle is not limited to this. The rake angle may gradually increase along the main cutting edge as it moves away from the corner edge. The magnitude 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 improves the strength of the main cutting edge near the corner edge while improving the adhesion resistance of the rake face.

[Modification 3]
In the above embodiment, the distance between the boundary 40a between the breaker face 40 and the rake face 20 and the main cutting edge 12, i.e., the width of the rake face 20, is 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, it is possible to suppress the inclusion of chips and to suppress damage to the cutting insert. The width of the rake face 20 is preferably 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 to these numerical ranges, it is possible to further suppress damage to the cutting insert.

Although this aspect has been described above based on the embodiment and modified examples, the embodiment of the above-mentioned aspect is intended to facilitate understanding of this aspect and does not limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and this aspect includes equivalents. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

(Application Example 1)
A cutting insert having a polygonal plate shape, at least one polygonal face being a surface, a side face arranged around the surface being a relief surface, and a cutting edge being formed on an intersection ridge between the surface and the relief surface,
a corner edge is formed at a corner of the surface, a main cutting edge is formed from the corner edge to the intersecting ridge line, and a minor cutting edge is formed from the other end of the corner edge to the intersecting ridge line,
The main cutting edge and the sub cutting edge are formed so as to move toward the back surface as they move away from the corner edge,
a cutting face is formed which is connected to the main cutting edge and the minor cutting edge and which faces the back surface as it moves away from the corner edge and the main cutting edge;
a breaker surface is formed which 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 which rises from the minor cutting edge and is connected to the breaker face and the flank face,
A cutting insert, wherein a rake angle as viewed in a cross section perpendicular to the main cutting edge gradually increases with increasing distance from the corner edge.
(Application Example 2)
The cutting insert according to Application Example 1, wherein a rake angle as viewed in a cross section perpendicular to the main cutting edge varies in a range from positive 5 degrees to positive 17 degrees as the rake angle increases away from the corner edge.
(Application Example 3)
The cutting insert according to Application Example 1 or 2, wherein a distance from the main cutting edge to an end of the breaker face as viewed in a cross section perpendicular to the main cutting edge is 0.3 mm to 0.42 mm.
(Application Example 4)
The cutting insert according to any one of Application Examples 1 to 3, wherein the polygonal surface is formed as a triangle or a rectangle.
(Application Example 5)
The cutting insert according to any one of Application Examples 1 to 4, wherein cutting edges are formed on both sides of the polygonal plate.
(Application Example 6)
The cutting insert according to any one of Application Examples 1 to 5, which can be used in a low-frequency vibration cutting machine.

1, 2... Cutting insert 1a... Surface 1b... Side surface 1c... Back surface 6, 7... Corner portion 10... Cutting edge 11... Corner edge 12... Main cutting edge 13... Minor cutting edge 20... Rake face 30... Flank face 40... Breaker face 41... Rising surface

Claims (6)

A cutting insert having a polygonal plate shape, at least one polygonal face being a surface, a side face arranged around the surface being a relief surface, and a cutting edge being formed on an intersection ridge between the surface and the relief surface,
a corner edge is formed at a corner portion of the surface, a main cutting edge is formed from the corner edge to the intersecting ridge line, and a minor cutting edge is formed from the other end of the corner edge to the intersecting ridge line,
The main cutting edge and the sub cutting edge are formed so as to move toward the back surface as they move away from the corner edge,
a cutting face is formed which is connected to the main cutting edge and the minor cutting edge and which faces the back surface as it moves away from the corner edge and the main cutting edge;
a breaker surface is formed which 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 which rises from the minor cutting edge and is connected to the breaker face and the flank face,
A cutting insert, wherein a rake angle as viewed in a cross section perpendicular to the main cutting edge gradually increases with increasing distance from the corner edge. The cutting insert according to claim 1, wherein the rake angle in a cross section perpendicular to the main cutting edge varies in a range from positive 5 degrees to positive 17 degrees as it moves away from the corner edge. The cutting insert according to claim 1, wherein the distance from the main cutting edge to the end of the breaker face in a cross section perpendicular to the main cutting edge is 0.3 mm to 0.42 mm. The cutting insert according to any one of claims 1 to 3, wherein the polygonal surface is formed as a triangle or a rectangle. The cutting insert according to claim 4, in which cutting edges are formed on both sides of the polygonal plate. A cutting insert according to any one of claims 1 to 3 that can be used in a low-frequency vibration cutting machine.

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