JP6965754B2 - Cutting inserts and cutting tools with replaceable cutting edges - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention is a cutting insert that is detachably attached to a cutting tool with a replaceable cutting edge such as an end mill with a replaceable cutting edge, and is particularly suitable for performing high cutting, and a cutting edge to which such a cutting insert is detachably attached. It relates to a replaceable cutting tool.

As a cutting insert and a cutting tool with a replaceable cutting edge for performing high feed machining, for example, in Patent Document 1, a triangular plate-shaped cutting having two triangular surfaces having two substantially triangular shapes having an insert body having three corners. The insert and one triangular surface of this cutting insert are directed in the tool rotation direction as a rake face, and the corner blades formed at one corner of this one triangular surface are directed toward the outer peripheral side of the tool body, and this one. The main cutting blade extending from one end of the corner blade is directed toward the tip side of the tool body, and the secondary cutting blade (wiper blade) extending from one end of the main cutting blade is substantially positioned on a plane perpendicular to the rotation axis of the tool body. Detachable cutting tools with replaceable cutting edges are listed.

In such a cutting insert, the main cutting edge is directed toward the tip end side of the tool body and toward the rear end side at a gentle angle with respect to the plane perpendicular to the rotation axis as it is directed toward the outer peripheral side of the tool body. Since thin chips are generated on the inner peripheral side of the tool body of this main cutting blade and the above-mentioned wiper blade, it is necessary to suppress an increase in cutting resistance even if the tool body is fed with a high feed amount. It is possible to perform efficient cutting in the processing of dies and the like. Further, in Patent Document 1, when the cutting amount in the Z-axis direction is set to be large in the inclined cutting process, the second secondary cutting edge connected to the first secondary cutting edge also acts as a cutting edge. It is stated that it will be.

Japanese Patent No. 5983901

By the way, in the high cutting process in which the cutting amount in the Z-axis direction is set large in this way, wide chips are easily generated and the chip discharging property is easily impaired, and it becomes difficult to stabilize the outflow direction of the chips. Chips may get caught and deteriorate the quality of the machined surface of the work material. To prevent such chip biting, set the rake angle of the cutting edge to a large angle on the conformal side to reduce the curl diameter of the chip, stabilize the outflow direction of the chip, and improve the discharge performance. Can be considered.

However, if the rake angle of the cutting edge is increased on the conformal side, the cutting edge angle of the cutting edge becomes smaller and the cutting edge strength is impaired, which causes the cutting edge to be chipped when a large cutting load or stress is applied. .. In particular, a corner blade that is directed from the outer peripheral portion of the main cutting blade that is directed to the tip side of the tool body to the outer peripheral side of the tool body, and a secondary cutting blade that is connected to the other end of the corner blade that acts as a cutting blade when the cutting amount is large. Such a large cutting load and stress are likely to act on the blade.

The present invention has been made under such a background, and the cutting edge strength is ensured while improving the machined surface quality of the work material by preventing the biting of chips in the high cutting process. It is an object of the present invention to provide a cutting insert capable of preventing a chipping or the like, and a cutting tool with a replaceable cutting edge to which such a cutting insert is detachably attached.

In order to solve the above-mentioned problems and achieve such an object, the cutting insert of the present invention has two polygonal shapes in which one is a rake face and the other is a seating surface. It is formed on a surface, a side surface on which a flank surface is formed which is arranged around these two polygonal planes and intersects with the rake face of the polygonal plane, and a crossing ridge portion between the rake face and the flank face. It is a cutting insert provided with a polygonal plate-shaped insert body having a cutting edge, and the insert body has a rotationally symmetric shape with respect to an insert center line passing through the centers of the two polygonal surfaces, and these 2 The two polygonal surfaces have an inverted symmetrical shape, and the cutting blades are a corner blade located at a corner of the polygonal surface, a main cutting blade extending from one end of the corner blade, and the other end of the corner blade. A first region provided with an extending secondary cutting edge and in which the rake angle in the cross section along the insert center line gradually increases from the end of the main cutting edge opposite to the corner cutting edge toward the corner cutting edge side. A second region in which the rake angle gradually decreases from the first region toward the corner blade side, and a portion including at least a part of the corner blade and the secondary cutting blade from the second region. and a third region to increase the rake angle GaSusumu next toward the cutting edge side, the third region has a small size of the region than the first region, the rake angle in the third region 15 It is characterized in that it is in the range of ° to 18 °.

Further, in the blade tip exchange type tool of the present invention, such a cutting insert is placed on one of the above two polygonal surfaces on an insert mounting seat formed on the outer periphery of the tip portion of the tool body that is rotated around the axis. The polygonal surface is used as a rake face in the tool rotation direction, one of the corner blades of one of the polygonal surfaces is directed to the outer peripheral side of the tool body, and one main of the corner blades extending from one end of the corner blade. The cutting edge is directed toward the tip end side of the tool body, and the end portion of this one main cutting edge opposite to the corner blade is projected to the tip of the tool body so as to be detachably attached. It is a feature.

In the cutting insert configured as described above, which is attached to the tool body of the cutting tool with replaceable cutting edge in this way, in high cutting, the corner blade of the one main cutting edge directed toward the tip side of the tool body. The corner blade directed from the end on the opposite side to the outer peripheral side of the tool body, and the corner blade side portion of the secondary cutting blade extending from the other end of the corner blade are exclusively used for cutting.

Here, in the portion on the inner peripheral side of the tool body from the end of the main cutting blade on the opposite side of the corner blade to the corner blade side, chips having a relatively thin thickness are generated, whereas the cutting having the above configuration is performed. In the insert, this part is regarded as the first region where the rake angle in the cross section along the insert center line gradually increases, and gives a sharp sharpness to the main cutting edge while ensuring the cutting edge strength against thin chips. The outflow direction can be controlled so as to guide the entire widely generated chips to the inner peripheral side (axis side) of the tool body, and the chip discharge property can be improved.

Further, the portion from this first region toward the corner blade side of the main cutting blade is defined as the second region where the rake angle gradually decreases, and the chip thickness gradually increases toward the outer peripheral side of the tool body. Therefore, while the cutting load and stress increase, it is possible to secure the cutting edge strength and prevent defects and the like.

Further, the portion including at least a part of the corner blade and the secondary cutting edge from this second region is defined as a third region in which the rake angle gradually increases in a range smaller than the first region toward the secondary cutting edge side. ing. Therefore, in this third region, which is located on the outermost circumference of the tool body, the cutting edge strength is maintained by the rake angle reduced through the second region, and the rake angle is gradually increased toward the secondary cutting edge side. By increasing the amount, chips can be caught in the inner peripheral side of the tool body with a small curl diameter, and in combination with the improvement of chip discharge performance by the first region, the biting of chips is prevented and the machined surface quality is good. Can be obtained. Since the rake angle of the cutting edge in this third region is in the range of 15 ° to 18 °, chips can be bitten while ensuring the cutting edge strength as demonstrated in Examples described later. Can be prevented.

Here, the rake angle of the cutting edge is larger than that of the first to third regions as the cutting blade moves from the third region toward the end of the auxiliary cutting blade on the side opposite to the corner blade. It may have a fourth region that gradually decreases. Such a fourth region is used exclusively in the above-mentioned inclined cutting process, and while the thickness of the generated chips remains thick, the above-mentioned rake angle increased in the third region is used as the fourth region. By reducing the rate of change from the first region to the third region at a larger rate, it is possible to secure the cutting edge strength again and prevent the occurrence of defects and the like.

Further, it is desirable that the rake angle in the second region is in the range of 15 ° to 25 °. When the rake angle in the second region is less than 15 °, the rake angle in the third region cannot be in the range of 15 ° to 18 °, while when the rake angle in the second region exceeds 25 °. , The cutting edge angle of the cutting edge in the second region may become small, and it may be difficult to secure the cutting edge strength.

Further, when the insert body has a triangular plate shape in which the two polygonal surfaces each have three corners as in the cutting insert described in Patent Document 1, the first region and the second region The position where the rake angle is maximized at the boundary with and is the end of the main cutting edge on the opposite side of the corner blade and the above when viewed from the direction facing the polygonal surface along the insert center line. It is desirable that the angle range is from 15 ° to 45 ° from the straight line passing through the insert center line toward the corner blade side with the insert center line as the center.

When the position where the rake angle is maximized is in the angle range of less than 15 °, the first region becomes small and the outflow direction can be controlled so as to sufficiently guide the chips to the inner peripheral side of the tool body. On the other hand, if the position where the rake angle is maximized is in the above angle range exceeding 45 °, the cutting edge angle of the main cutting edge becomes small at the part where thick chips are generated, and the cutting edge is chipped. Etc. may not be reliably prevented. The angle range in which the rake angle is maximized is preferably in the range of 17 ° to 40 °, and more preferably in the range of 19 ° to 35 °.

As described above, according to the present invention, in high-cutting machining, the outflow direction of chips is controlled to be guided to the inner peripheral side of the tool body, and the machined surface of the work material is prevented from being bitten by chips. The quality can be improved, and the cutting edge strength can be sufficiently secured according to the thickness of the generated chips to prevent the cutting edge from being chipped.

It is a perspective view which shows one Embodiment of the cutting insert of this invention. It is a top view which looked at the embodiment shown in FIG. 1 from the direction of the insert center line. It is a side view of the arrow line X direction view in FIG. It is a side view of the arrow line Y direction view in FIG. FIG. 2 is a cross-sectional view taken along the line AL in FIG. FIG. 2 is a cross-sectional view taken along the line BL in FIG. FIG. 2 is a cross-sectional view taken along the line CL in FIG. FIG. 2 is a cross-sectional view taken along the line DL in FIG. FIG. 5 is a perspective view of a tool body of a cutting tool with a replaceable cutting edge to which the cutting insert of the embodiment shown in FIG. 1 is detachably attached. FIG. 5 is a perspective view of a cutting tool with a replaceable cutting edge, in which the cutting insert of the embodiment shown in FIG. 1 is detachably attached to the tool body shown in FIG. It is a figure which shows the rake angle of the cutting edge in the cross section along the insert center line in the cutting insert of the Example of this invention and the cutting insert of Comparative Examples 1 and 2. (A) It is a figure which shows the outflow state of the chip in the cutting insert of the Example of this invention, (b), (c) is the figure which shows the outflow state of the chip in the cutting insert of the comparative example. (A) It is a figure which shows the stress concentration state in the cutting insert of the Example of this invention, (b), (c) is the figure which shows the stress concentration state in the cutting insert of the comparative example.

1 to 8 show an embodiment of the cutting insert of the present invention, and FIG. 9 shows a tool body of a cutting tool with a replaceable cutting edge to which the cutting insert of this embodiment can be detachably attached. FIG. 10 shows an embodiment of the cutting tool with a replaceable cutting edge of the present invention in which the cutting insert of the above embodiment is detachably attached to the tool body. The cutting insert of the present embodiment includes a polygonal plate-shaped insert body 11 formed of a hard material such as a super hard alloy, and the insert body 11 has two polygonal surfaces 12 each having three corners. It has a triangular plate shape, and has a rotationally symmetric shape with respect to the insert center line L passing through the centers of these two polygonal surfaces 12, and a front-back inverted symmetric shape with respect to the two polygonal surfaces 12.

When these two polygonal surfaces 12 are attached to the tool body 21 of a cutting tool with a replaceable cutting edge as shown in FIG. 10, one polygonal surface 12 is used as a rake face and the other polygonal surface 12 is used as a rake face. Reference numeral 12 denotes a seating surface on the insert mounting seat 22 formed on the tool body 21. A flank surface 14 that intersects the rake face of the two polygonal faces 12 is formed on the side surface 13 of the insert body 11 arranged around the two polygonal faces 12, and these rake faces (polygonal faces 12) are formed. ) And the flank surface 14, the cutting edge 15 is formed at the intersecting ridgeline portion. At the center of the two polygonal surfaces 12, a mounting hole 16 having a circular cross section centered on the insert center line L for mounting the insert body 11 on the insert mounting seat 22 is provided, and the insert body 11 is attached to the insert center line. It penetrates in the L direction and opens.

The cutting edge 15 has a corner blade 15a having a convex curved shape such as an arc arranged at three corners of the polygonal surface 12 when viewed from the insert center line L direction, and one end of the corner blade 15a (in FIG. 2). A linear main cutting edge 15b extending in contact with the corner blade 15a from the end on the clockwise side with the insert center line L as the center) or a convex curved main cutting edge 15b having a radius of curvature larger than the convex curve formed by the corner blade 15a. At one end of the main cutting edge 15b, a linear or convex curved wiper blade 15c having a radius of curvature larger than the convex curve formed by the main cutting edge 15b is provided. Further, the cutting blade 15 further includes a secondary cutting blade 15d that is linear when viewed from the insert center line L direction extending in contact with the corner blade 15a from the other end of the corner blade 15a, and the secondary cutting blade 15d is one. It extends in a direction that intersects the wiper blade 15c of another cutting blade 15 adjacent to the other end side (counterclockwise direction side in FIG. 2) of the cutting blade 15 at an obtuse angle.

The flank 14 is formed at the edge of the side surface 13 of the insert body 11 on the side of the two polygonal faces 12, and the flank 14 is inserted between the flanks 14 in a cross section along the insert center line L. A plurality of insert restraint surfaces 17 extending in the center line L direction are formed in a direction intersecting each other when viewed from the insert center line L direction. In the present embodiment, these insert restraint surfaces 17 are planar parallel to the insert center line L, and are formed inside the main cutting edge 15b and the sub cutting edge 15d in the insert center line L direction and are adjacent to each other. The portions of the corner blades 15a located inside the insert center line L direction between the insert restraint surfaces 17 are connected by a convex curved surface.

Further, a flat surface portion 12a perpendicular to the insert center line L is formed around the opening of the mounting hole 16 on the polygonal surface 12 to be a rake face, and this flat surface is formed on the corner blade 15a side. An inclined portion 12b is formed which is inclined so as to protrude in the insert center line L direction from the portion 12a toward the cutting edge 15 side. In the present embodiment, the total length of the corner blade 15a and the main cutting blade 15b, a part of the wiper blade 15c on the side intersecting the main cutting blade 15b, and the corner blade 15a of the secondary cutting blade 15d are in contact with each other. A part of the side is formed at the intersecting ridgeline portion between the inclined portion 12b and the flank surface 14, and the remaining portion of the wiper blade 15c and the auxiliary cutting blade 15d is formed at the crossing ridgeline portion between the flat surface portion 12a and the flank surface 14. ing. The difference in height in the insert center line L direction between the most protruding position of the cutting edge 15 in the insert center line L direction and the flat surface portion 12a is, for example, 0.6 mm.

Then, the cutting edge 15 has a rake angle θ with respect to the flat surface portion 12a in the cross section along the insert center line L from the end portion 15e of the main cutting edge 15b opposite to the corner blade 15a toward the corner blade 15a side. The first region 15A gradually increases, the second region 15B in which the rake angle θ gradually decreases toward the corner blade 15a side from the first region 15A, and the corner blade 15a and the secondary cutting blade 15d from the second region 15B. It has a third region 15C in which the rake angle θ gradually increases in a range smaller than the first region 15A as the rake angle θ is gradually increased toward the secondary cutting edge 15d side in a portion including at least a part of the above. Further, the rake angle θ in the third region 15C is in the range of 15 ° to 18 °. In the present specification, as described above, the inclination angle of the rake face of the inclined portion 12b with respect to the flat surface portion 12a of the cutting insert alone is referred to as a rake angle θ for convenience.

Further, the cutting edge 15 further moves from the third region 15C toward the end portion 15f of the auxiliary cutting edge 15d on the side opposite to the corner blade 15a, and has a larger rate of change than the first region 15A to the third region 15C. It has a fourth region 15D in which the rake angle θ gradually decreases. The rake angle θ of the portion of the cutting edge 15 formed at the intersecting ridgeline portion between the flat surface portion 12a and the flank surface 14 is 0 °.

Here, reference numeral A in FIG. 11 indicates that in the cutting insert of the present embodiment having the triangular plate-shaped insert main body 11, the main cutting blade 15b on the side opposite to the corner blade 15a along the insert center line L. The cross section passing through the end portion 15e is set to the reference 0 ° position, and the corner blade 15a of the other cutting edge 15 located at a position 120 ° counterclockwise with respect to the insert center line L in FIG. 2 from this reference cross section. The rake angle θ in the cross section along the insert center line L up to the end portion 15e of the main cutting edge 15b on the opposite side is calculated by 5 °, and according to this, the cross-sectional position is expressed in the present embodiment. The angle range of 0 ° to 25 ° is the first region 15A.

Further, the angle range in which the angle of the cross-sectional position on the corner blade 15a side from the first region 15A is 25 ° to 60 ° is the second region 15B in the present embodiment, and therefore the rake angle θ is the second region 15B. The cross-sectional position, which is the boundary between the first region 15A and the first region 15A, reaches the maximum value near 25 ° as shown in FIG. In the present embodiment, the maximum value of the rake angle θ is 23.526 °. Further, in the present embodiment, the main cutting edge 15b is formed so that the angle of the cross-sectional position is in an angle range of 0 ° to 60 °, and the whole is formed in the first and second regions 15A and 15B. Here, it is desirable that the rake angle θ in the second region 15B is in the range of 15 ° to 25 °, and the rake angle θ at the position where the cross-sectional position angle shown in FIG. 6 is 45 ° is 20.456 °. be.

Furthermore, in the present embodiment, the third region 15C has the angle of the cross-sectional position in the angle range of 60 ° to 75 °, and the corner blade 15a has the angle of the cross-sectional position in the angle range of 60 ° to 70 °. Therefore, one end of the corner blade 15a is located at the boundary between the second region 15B and the third region 15C, and the rake angle θ at this boundary shown in FIG. 7 is, for example, 16.572 °. .. That is, the entire corner blade 15a is formed in the third region, and a part of the auxiliary cutting blade 15d on the corner blade 15a side is also formed in the third region 15C.

Further, in the present embodiment, the angle range in which the angle of the cross-sectional position is 75 ° to 95 ° is defined as the fourth region 15D. Therefore, the position where the angle of the cross-sectional position is 75 ° is the boundary between the third region 15C and the fourth region 15D, and the rake angle θ at the position of this boundary shown in FIG. 8 is 17.147 °, which is from 15 ° to 15 °. It is said to be within the range of 18 °.

Further, as shown in FIG. 11, in the fourth region 15D, the rake angle θ gradually decreases at a larger rate of change than in the first to third regions 15A to 15C. Here, assuming that [change amount of rake angle θ (°)] / [angle change amount of cross-sectional position (°)] is the angle change rate of the rake angle θ, the angle change rate of the first region 15A is 30% or more. It is in the range of 45%, 40% in the present embodiment, and the angle change rate of the second region 15B is in the range of -15% to -25%, and is -20% in the present embodiment. The angle change rate of the three regions 15C is in the range of 0.3% to 8%, which is 5% in the present embodiment, whereas the angle change rate of the fourth region 15D is -97% to -77%. It is a range, which is -87% in this embodiment.

Such a cutting insert of the present embodiment is detachably attached to the insert mounting seat 22 formed on the outer periphery of the tip end portion of the tool body 21 of the cutting tool with a replaceable cutting edge as shown in FIG. 9, and is shown in FIG. Such a cutting tool with a replaceable cutting edge according to an embodiment of the present invention is configured. The tool body 21 has a substantially cylindrical shape centered on the axis O, and at the time of cutting, the rear end portion is gripped by the spindle of the machine tool and rotated around the axis O in the tool rotation direction T, and the cutting insert Cut the work material.

A plurality of (five in this embodiment) tip pockets 23 are formed on the outer periphery of the tip portion of the tool body 21, and the insert mounting seat 22 is the tip portion of the wall surface of these tip pockets 23 facing the tool rotation direction T. A flat bottom surface 22a formed on the outer periphery and facing the tool rotation direction T side and a flat bottom surface 22a arranged at a distance from the bottom surface 22a to the tool rotation direction T side and abutting against the insert restraint surface 17 of the insert body 11. It is provided with a plurality of possible planar wall surfaces 22b. The bottom surface 22a is formed with a screw hole 22c into which the clamp screw 24 inserted into the mounting hole 16 is screwed.

In such an insert mounting seat 22, the cutting insert of the present embodiment faces the tool rotation direction T side with one polygonal surface 12 of the insert body 11 as a rake face, and the flat surface portion 12a of the other polygonal surface 12 Is brought into close contact with the bottom surface 22a of the insert mounting seat 22 and seated. Further, in the cutting insert, the corner blade 15a located at one corner of one of the polygonal surfaces 12 is projected toward the outer peripheral side of the tool body 21, and the main cutting blade 15b extending from one end of the corner blade 15a is used as a tool. The end portion 15e of the main cutting blade 15b, which is opposite to the corner blade 15a, is projected toward the tip end side of the main body 21 toward the outer edge of the tool main body 21, and is projected to the leading edge of the tool main body 21 to form the mounting hole 16. The clamp screw 24 inserted into the screw hole 22c is screwed into the screw hole 22c to be fixed.

The wiper blade 15c extending from the end portion 15e projecting from the tip of the tool body 21 is arranged so that the shear angle is 2 ° or less with respect to the plane perpendicular to the axis O, that is, this The wiper blade 15c is arranged along a plane perpendicular to the axis O, or is inclined toward the rear end side toward the inner peripheral side of the tool body 21 at an angle of 2 ° or less with respect to this plane. Be placed. At this time, the insert restraint surface 17 of the side surface 13 connected to the cutting edge 15 not used for cutting is brought into contact with the wall surface 22b of the insert mounting seat 22, and the rotation of the insert main body 11 around the insert center line L is restrained.

The blade tip exchange type cutting tool to which the cutting insert is attached in this way is sent out in the direction perpendicular to the axis O while being rotated around the axis O, and protrudes to the tip of the tool body 21 in the case of high cutting. The work material is cut by the corner blade 15a protruding from the end portion 15e of the main cutting blade 15b to the outer peripheral side and the corner blade 15a side portion of the auxiliary cutting blade 15d connected to the other end of the corner blade 15a, and the end portion is cut. The bottom surface of the machined surface is finished by the wiper blade 15c connected to 15e.

Since the main cutting edge 15b has a linear shape or a convex curved shape having a radius of curvature larger than that of the corner blade 15a, the thickness of chips generated by the inner peripheral side portion of the tool body 21 is relatively thin. On the other hand, in the cutting insert having the above configuration, this portion is defined as the first region 15A in which the rake angle θ in the cross section along the insert center line L gradually increases, and the cutting is made for such a thin chip. While ensuring the blade strength, the main cutting edge 15b can be given a sharp sharpness, and the outflow direction is controlled so as to guide the entire widely generated chips to the inner peripheral side (axis line side) of the tool body 21. It is possible to improve the chip evacuation property.

The thickness of the chips gradually increases from the portion of the main cutting edge 15b on the inner peripheral side of the tool body 21 toward the corner blade 15a on the outer peripheral side of the tool body 21, and the cutting load and stress acting on the cutting edge 15 increase. It gets bigger and bigger. On the other hand, in the cutting insert having the above configuration, this portion is defined as the second region 15B in which the rake angle θ gradually decreases even on the conformal side toward the corner blade 15a side, and thus the chip becomes thicker. It is possible to secure the cutting edge strength against the cutting load and stress due to the above and prevent the occurrence of defects and the like.

Further, the portion including at least a part of the corner blade 15a and the auxiliary cutting blade 15d from the second region 15B (in the present embodiment, the entire corner blade 15a and the portion of the auxiliary cutting blade 15d on the corner blade 15a side) is The rake angle θ is set to be the third region 15C in which the rake angle θ gradually increases in a range smaller than that of the first region 15A toward the secondary cutting edge 15d side. Therefore, in the third region 15C located on the outermost circumference of the tool body 21, the cutting edge strength is maintained by the rake angle θ reduced in the second region 15B, and chips are formed in the tool body 21 with a small curl diameter. It can be entangled on the peripheral side, and the first region 15A improves the chip evacuation property, and together with the fact that the biting of chips can be prevented, good machined surface quality can be obtained.

Further, since the rake angle θ of the cutting edge 15 in the third region 15C is in the range of 15 ° to 18 °, it is possible to surely secure the cutting edge strength and prevent chip biting. That is, as will be demonstrated in the examples described later, if the rake angle θ in the third region 15C is less than 15 ° or more than 18 °, it becomes difficult to curl the chips with a small curl diameter and bite. May occur. Further, if the rake angle θ exceeds 18 °, the blade angle becomes small, the cutting edge strength is impaired, and a defect may easily occur.

Further, in the present embodiment, the cutting edge 15 is larger than the first to third regions 15A to 15C as it goes from the third region 15C toward the end portion 15f of the auxiliary cutting blade 15d on the side opposite to the corner blade 15a. It has a fourth region 15D in which the rake angle θ gradually decreases at the rate of change (rate of change in angle). Such a fourth region 15D is exclusively used in the inclined cutting process in which the tool body 21 is sent diagonally to the tip side with respect to the axis O to perform cutting, and the thickness of chips generated in the fourth region 15D is used. Is still thick, while the rake angle θ increased in the third region 15C is reduced in the fourth region 15D at a larger angle change rate than in the first region 15A to the third region 15C, thereby cutting the cutting edge. It is possible to secure the strength again and prevent the occurrence of defects and the like.

Here, it is desirable that the rake angle θ in the second region 15B is in the range of 15 ° to 25 ° as described above. If the rake angle θ in the second region 15B is less than 15 °, the rake angle θ in the third region 15C cannot be set in the range of 15 ° to 18 °, and the chip repersibility may be impaired. On the other hand, if the rake angle θ in the second region 15B exceeds 25 °, the blade angle of the cutting edge 15 in the second and third regions 15B and 15C becomes too small, which may lead to chipping and the like.

In the cutting insert of the present embodiment in which the insert body 11 has a triangular plate shape having three corners on each of the two polygonal surfaces 12, the rake is formed at the boundary between the first region 15A and the second region 15B. The position where the angle θ is maximized is the end portion 15e of the main cutting edge 15b on the opposite side of the corner blade 15a and the insert center line L when viewed from the direction facing the polygonal surface 12 along the insert center line L. It is desirable that the angle range is from 15 ° to 45 ° from the straight line passing through the insert center line L toward the corner blade 15a side, and in the present embodiment, the cross-sectional position is around 25 ° as described above.

When the position where the rake angle θ is maximized is in the angle range of less than 15 °, the first region 15A becomes small and the outflow direction is controlled so as to sufficiently guide the chips to the inner peripheral side of the tool body. Can be difficult. On the other hand, when the position where the rake angle θ is maximized is in the above angle range exceeding 45 °, the cutting edge angle of the cutting edge 15 becomes small at the portion where the chips are thickly generated, and the cutting edge 15 is damaged. There is a risk that it cannot be reliably prevented. The angle range in which the rake angle θ is maximized is preferably in the range of 17 ° to 40 °, and more preferably in the range of 19 ° to 35 °.

Further, in the cutting insert of the present embodiment, a plurality of cutting inserts extending in the insert center line L direction in a cross section along the insert center line L between the flanks 14 on the side of two polygonal surfaces 12 on the side surface 13 of the insert body 11. The insert restraint surfaces 17 of the above are formed in a direction intersecting each other when viewed from the insert center line L direction. Therefore, by bringing these insert restraint surfaces 17 into contact with the wall surface 22b of the insert mounting seat 22 as described above, the rotation of the insert body 11 around the insert center line L can be restrained, and more stable cutting can be performed. Can be done.

Next, an example will be given to demonstrate the effect of the rake angle θ in the third region 15C of the present invention. In this embodiment, as shown by reference numeral A in FIG. 11, a cutting insert in which the rake angle θ in the third region 15C is in the range of 15 ° to 18 ° is used, and the spindle rotation speed is 808.0 rpm per blade. A case was analyzed in which a work material made of S50C was subjected to high cutting under the cutting conditions of a feed amount of 0.7 mm, a cutting depth of 45.0 mm in the radial direction, and a cutting depth of 3.0 mm in the axial direction. Further, as Comparative Example 1 with respect to this Example, the rake angle θ in the third region 15C shown by reference numeral B in FIG. 11 is less than 15 °, and as Comparative Example 2, the third region shown by reference numeral C in FIG. 11 It was also analyzed when the rake angle θ in the region 15C exceeded 18 ° and high cutting was performed under the same cutting conditions as in the examples.

12 (a) to 12 (c) show the outflow state of chips according to these Examples and Comparative Examples 1 and 2. FIG. 12 (a) shows Examples and FIG. 12 (b) shows Comparative Examples 1 and 2. FIG. 12 (c) shows the result of Comparative Example 2. According to FIGS. 12 (a) to 12 (c), in the examples, the chips are curled with a small curl diameter, whereas in the comparative examples 1 and 2, the chips tend to extend without curling, which may cause biting. It turns out that there is.

13 (a) to 13 (c) are analysis of the stress concentration of Examples and Comparative Examples 1 and 2, FIG. 13 (a) shows Examples, and FIG. 12 (b) shows Comparative Examples 1 and 2. FIG. 12C shows the result of Comparative Example 2, and the dark-colored portion on the cutting edge side is the portion on which high stress is applied. From the results of FIGS. 12A to 12C, it can be seen that stress is concentrated on the cutting edge 15 used for cutting in both Examples and Comparative Examples 1 and 2, but the rake angle θ is particularly large. In Comparative Example 2 in which the temperature exceeds 18 °, a high stress is applied, and it can be seen that the cutting edge may be chipped due to the small blade angle.

An example of a method for measuring the inclination angle of the rake face of the cutting insert (the rake angle θ described above in the present specification) will be described below. First, as a first step, the three-dimensional shape of the insert body 1 is measured using a non-contact three-dimensional measuring device, and these measurement results are stored as electronic data. Next, as a second step, using the three-dimensional measurement data and the shape measurement software, the insert is inserted at the ridgeline portion of the cutting edge 15 of the insert body 1 at each interval width of a predetermined radiation angle from the insert center line L. Create a plurality of cross-sectional views along the center line L. Finally, as a third step, by obtaining a cross-sectional view of the ridgeline portion of the cutting edge 15 of the insert body 1 as shown in FIGS. The inclination angle of the rake face of the inclined portion 12b, that is, the rake angle θ can be obtained.

11 Insert body 12 Polygonal surface 12a Flat surface 12b Inclined part 13 Side surface 14 Escape surface 15 Cutting blade 15a Corner blade 15b Main cutting blade 15c Wiper blade 15d Secondary cutting blade 15A 1st area 15B 2nd area 15C 3rd area 15D 4th Area 16 Mounting hole 17 Insert restraint surface 21 Tool body 22 Insert mounting seat 23 Chip pocket 24 Clamp screw L Insert center line θ Drake angle of cutting edge 15 in cross section along the insert center line O Axis line of tool body 21 T Tool rotation direction

Claims (5)

Two polygonal surfaces that form a polygon and one of which is a rake face and the other is a seating surface, and are arranged around these two polygonal surfaces and intersect with the rake surface of the polygonal surface. A cutting insert having a polygonal plate-shaped insert body having a side surface on which a flank surface is formed and a cutting edge formed at a crossing ridge between the rake face and the flank surface.
The insert body has a rotationally symmetric shape with respect to the insert center line passing through the centers of the two polygonal planes, and has a front-back inverted symmetric shape with respect to these two polygonal planes.
The cutting blade includes a corner blade located at a corner of the polygonal surface, a main cutting blade extending from one end of the corner blade, and a secondary cutting blade extending from the other end of the corner blade.
A first region in which the rake angle in the cross section along the insert center line gradually increases from the end of the main cutting blade on the side opposite to the corner blade toward the corner blade side, and the corner from this first region. A second region in which the rake angle gradually decreases toward the blade side, and a portion including at least a part of the corner blade and the sub-cutting blade from this second region, and the rake angle toward the sub-cutting blade side. and a third region GaSusumu increased following,
The size of the third region is smaller than that of the first region.
The cutting insert, characterized in that said rake angle in the third region is in the range of 15 ° ~ 18 °. The rake angle of the cutting edge gradually decreases from the third region toward the end of the secondary cutting edge opposite to the corner blade at a rate of change larger than that of the first region to the third region. The cutting insert according to claim 1, wherein the cutting insert has a fourth region. The cutting insert according to claim 1 or 2, wherein the rake angle in the second region is in the range of 15 ° to 25 °. The insert body has a triangular plate shape in which the two polygonal surfaces each have three corners.
The position where the rake angle is maximized at the boundary between the first region and the second region is the position opposite to the corner blade when viewed from the direction facing the polygonal surface along the insert center line. From claim 1, the straight line passing through the end of the main cutting edge and the insert center line is within an angle range of 15 ° to 45 ° from the straight line passing through the insert center line toward the corner blade side with the insert center line as the center. The cutting insert according to any one of claims 3. The cutting insert according to any one of claims 1 to 4 is attached to an insert mounting seat formed on the outer periphery of the tip of a tool body that is rotated around an axis.
One of the above two polygonal surfaces is used as a rake face and oriented in the tool rotation direction.
One of the corner blades on one of the polygonal surfaces is directed toward the outer peripheral side of the tool body, and
One of the main cutting blades extending from one end of the one corner blade is directed toward the tip end side of the tool body, and the end of the one main cutting blade opposite to the corner blade is the most of the tool body. A cutting tool with a replaceable cutting edge that is attached to the tip so that it can be attached and detached.

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