JP6972510B2 - Cutting insert - Google Patents

Description

The present invention relates to a cutting insert used for cutting, and particularly to a cutting insert attached to a cutting tool with a replaceable cutting edge used for rolling.

There is a demand to design a cutting edge with high strength that can process a work material with high hardness.

When the axial rake angle (axial rake) is set to a negative angle (negative), the rake angle is reduced at both the tip and the outer circumference of the milling tool, and the cutting edge strength can be increased. On the other hand, if the rake angle in the axial direction is set to a negative angle, chips are likely to be discharged downward (toward the tip side) of the milling tool, resulting in chip clogging and scraping of chips to the workpiece surface. It will be easier. On the other hand, if the rake face of the cutting insert is formed of a flat surface and the axial rake angle is set to a positive angle, the true rake angle increases as the distance from the tip of the rolling tool increases, and the cutting edge strength decreases.

An object of the present invention is to provide a cutting insert having excellent cutting edge strength and chip evacuation.

The cutting insert according to one aspect of the present invention is a cutting insert that is attached to a body that rotates about a rotation axis and constitutes a cutting tool with a replaceable cutting edge together with the body. The cutting insert comprises a lower surface mounted on the seating surface of the body, an upper surface opposite the lower surface, and a peripheral side surface connecting between the lower surface and the upper surface. A cutting edge is formed at the ridgeline portion where the upper surface and the peripheral side surface intersect. The cutting edge has an inner cutting edge and a corner blade. The corner blade is formed at a position farther from the rotation axis than the inner cutting blade and is connected to the inner cutting blade. The corner blade is formed in an arc shape in a plan view seen from a direction facing the upper surface. In the direction perpendicular to the axis of rotation, the width of the corner blade is 40% or more and 50% or less of the width of the cutting insert. The upper surface has a negative land formed along the cutting edge and having a negative angle, and a flat surface connected to the negative land and parallel to the lower surface. The angle of the negative land increases from one end of the end of the corner blade connected to the inner cutting edge toward the other end.

According to this aspect, the angle of the negative land formed adjacent to the corner blade becomes smaller toward the portion located at the tip of the milling tool. By providing a negative land in which the land angle gradually changes to the positive side as the distance from the tip of the milling tool increases, the chip evacuation property can be improved and the cutting edge strength can be improved.

In the above embodiment, the cutting edge of the cutting insert further has a linear laminating edge connected to the corner edge and parallel to the axis of rotation. At the ridgeline portion of the shaving blade, it is preferable that the upper surface intersects the shaving blade at an obtuse angle.

According to this aspect, the machined surface of the corner blade is rubbed by the shaving blade, so that the machined surface roughness is improved. In the linear ridge portion, since the upper surface and the shaving blade intersect at an obtuse angle, it is possible to prevent the linear ridge portion from coming into contact with the surface of the work and deteriorating the roughness of the machined surface.

In the above aspect, the cutting insert is further provided with a through hole penetrating from the upper surface to the lower surface, and when viewed from the upper surface, the ratio of the flat surface in the region excluding the through hole from the upper surface is preferably 90% or more.

If the upper surface is uneven, there are restrictions on how the grindstone moves when grinding the cutting insert. According to this aspect, since most of the upper surface is composed of a flat surface, it is easy to grind. It can be manufactured with higher accuracy than a cutting insert having a chip breaker or the like formed on the upper surface.

According to the present invention, it is possible to provide a cutting insert having both excellent cutting edge strength and chip evacuation.

FIG. 1 is a perspective view showing an example of a cutting insert according to an embodiment of the present invention. FIG. 2 is a perspective view of the cutting insert shown in FIG. 1 as viewed from the lower surface side. FIG. 3 is a top view of the cutting insert shown in FIG. 1 as viewed from above. FIG. 4 is a side view of the cutting insert shown in FIG. 1 as viewed from the peripheral side surface (second side surface portion). FIG. 5 is a side view of the cutting insert shown in FIG. 1 as viewed from the peripheral side surface (second front surface portion). FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. FIG. 8 is a perspective view showing an example of an end mill provided with the cutting insert of the present embodiment. FIG. 9 is a view of the tip end portion of the end mill shown in FIG. 8 as viewed from the upper surface side of the cutting insert. FIG. 10 is a view of the tip of the end mill shown in FIG. 8 as viewed from a direction parallel to the rotation axis of the body.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings. In each figure, those having the same reference numerals have the same or similar configurations. In the cutting insert 10 of the present invention, the cutting edge (10f, 10g, 10m) is arranged at a substantially constant height from the lower surface 10b in all the portions thereof (see FIGS. 4 and 5). The negative land 10q provided along the corner blade 10f is formed so that the angle increases from θ1 to θ2 from one end 12 connected to the inner cutting edge 10g to the other end 13 (FIGS. 6 and 6). (See FIG. 7). By providing a negative land in which the land angle gradually changes to the positive side as the distance from the tip of the milling tool increases, the chip evacuation property can be improved and the cutting edge strength can be improved. Hereinafter, each configuration will be described in detail with reference to FIGS. 1 to 10.

1 and 2 are perspective views showing an example of a cutting insert 10 according to an embodiment of the present invention. As shown in FIGS. 1 and 2, the cutting insert 10 has peripheral side surfaces (10d, 10d', 10e) connecting the upper surface 10a, the lower surface 10b on the opposite side of the upper surface 10a, and the upper surface 10a and the lower surface 10b. , 10e'), and.

The peripheral side surface includes a pair of substantially flat side surface portions (10d, 10d') and a pair of front surface portions (10e, 10e') connecting between the pair of side surface portions. In the following description, one of the pair of side surface portions may be referred to as a first side surface portion 10d, and the other may be referred to as a second side surface portion 10d'. Similarly, of the pair of frontal portions, one may be referred to as a first frontal portion 10e and the other may be referred to as a second frontal portion 10e'.

FIG. 3 is a top view of the cutting insert 10 as viewed from the top surface 10a. As shown in FIG. 3, the ridgeline portion where the upper surface portion 10a and the first side surface portion 10d intersect is formed in a straight line. Similarly, the ridge line portion where the upper surface portion 10a and the second side surface portion 10d' intersect is formed in a straight line parallel to the ridge line portion in the first side surface portion 10d. As shown in FIG. 3, the distance between the linearly formed ridges on the first and second side surface portions 10d and 10d'is defined as the width W of the cutting insert 10. The width W of the cutting insert 10 is, for example, 4 to 4.5 mm.

In the illustrated example, the lower surface 10b of the cutting insert 10 is formed in a planar shape. A through hole H penetrating the upper surface 10a and the lower surface 10b is formed in the central portion of the cutting insert 10. The cutting insert 10 is fixed to the body B by screwing the clamp screw penetrating the through hole H with the female screw provided on the seat surface of the body B of the cutting tool with replaceable cutting edge. At this time, the cutting insert 10 is fixed to the body B so that the side surface portion 10d side is close to the rotation axis AX of the body B and the side surface portion 10d'side is far from the rotation axis AX of the body B (see FIG. 9). Body B will be described in detail later with reference to FIGS. 8 to 10.

FIG. 4 is a side view of the cutting insert 10 as viewed from the second side surface portion 10d'of the peripheral side surface. FIG. 5 is a side view of the cutting insert 10 as viewed from the second front surface portion 10e of the peripheral side surface. As shown in FIGS. 4 and 5, the peripheral side surfaces (10d, 10d', 10e, 10e') of the cutting insert 10 are connected to the lower surface 10b, and the vertical portion 10h perpendicular to the lower surface 10b and the vertical portion 10h. A connecting portion 10j that is connected to and spreads so that the cross-sectional area cut in parallel to the lower surface 10b increases as the distance from the lower surface 10b increases, and a cross-sectional area cut in parallel to the lower surface 10b as the distance from the lower surface 10b increases. It is provided with an inclined portion 10k, which spreads so as to increase.

In the following description, the angle at which the peripheral side surface is inclined with respect to the central axis of the through hole H is referred to as an inclination angle. The angle formed by the central axis of the through hole H and the peripheral side surface is obtained as a margin angle formed by the direction vector of the central axis and the normal vector of the peripheral side surface. As shown in FIG. 5, the peripheral side surface (10d, 10d', 10e, 10e') of the connecting portion 10j has a larger inclination angle (first inclination angle α) than the peripheral side surface of the vertical portion 10h. .. Therefore, the rate of increase in cross-sectional area is large. On the other hand, the peripheral side surface of the inclined portion 10k has an inclination angle (second inclination angle β) smaller than that of the peripheral side surface of the vertical portion 10h. Therefore, the rate of increase in cross-sectional area is small.

Further, the height in the direction perpendicular to the lower surface 10b increases in the order of the vertical portion 10h, the connecting portion 10j, and the inclined portion 10k. The height h3 of the inclined portion 10k is larger than the sum h1 + h2 of the height h1 of the vertical portion 10h and the height h2 of the connecting portion 10j.

In other words, the cutting insert 10 has a constricted shape from the upper surface 10a to the lower surface 10b, and is connected after contracting at the inclined portion 10k so that the cross-sectional area gradually decreases from the upper surface 10a to the lower surface 10b. The portion 10j has a structure that contracts so as to greatly decrease the cross-sectional area toward the lower surface 10b, and the vertical portion 10h is connected to the lower surface 10b while maintaining a constant cross-sectional area. It should be noted that the inclination angles of the connecting portion 10j and the inclined portion 10k do not have to be constant. However, the average value of the inclination angle of the connecting portion 10j and the average value or the representative value of the inclination angle of the inclined portion 10k have a magnitude relationship.

As shown in FIGS. 1 and 2, a cutting edge is formed in at least a part of the ridgeline portion where the upper surface portion 10a and the first front surface portion 10e intersect. The cutting edge includes a corner blade 10f and an inner cutting edge 10g. Similarly, a corner blade 10f and an inner cutting edge 10g are formed as cutting edges on the ridgeline portion where the upper surface 10a and the second front surface portion 10e'intersect. The cutting insert 10 has a structure that is 180 ° axisymmetric with respect to the central axis of the through hole H. That is, the first front surface portion 10e and the second front surface portion 10e'have substantially the same shape and function. Therefore, the first front portion 10e will be described in detail as a representative, and the duplicate description of the second front portion 10e'will be omitted.

The corner blade 10f is provided at the corner portion of the cutting insert 10 and is formed so as to have a predetermined curvature when viewed from the direction facing the upper surface 10a. In other words, the corner blade 10f is formed in an arc shape. The curvature of the corner blade 10f can be selected according to the specifications of the angle R to be machined. For example, when the specification of the angle R is 2 mm, a cutting insert in which the corner blade 10f has a predetermined radius of curvature (for example, a little less than 2 mm) so that the angle R after machining in consideration of the rotation locus of the corner blade is 2 mm. 10 may be selected.

In the present embodiment, as shown in FIG. 3, a corner blade 10f having a larger curvature than usual and a huge corner blade is formed. In the illustrated example, the width Wf of the corner blade 10f is 40% or more and 50% or less of the width W of the cutting insert 10 in the direction perpendicular to the rotation axis AX of the body B. More specifically, when viewed from the direction facing the upper surface 10a, 40 to 50 in the direction of the width W (the direction connecting the first side surface portion 10d and the second side surface portion 10d') from the side surface portion 10d'. The corner blade 10f is formed up to the position of%, and the radius of curvature thereof is formed to be, for example, 50% or less of the width W.

Further, in the examples shown in FIGS. 3 and 5, the inner cutting edge 10g is continuously formed on the corner blade 10f. The inner cutting edge 10g is connected to the other end portion 12 connected to the corner blade 10f and the first side surface portions 10d, 10d'formed substantially linearly when viewed from the direction facing the upper surface 10a. One end 11 and the like.

As shown in FIGS. 4 and 5, the upper surface 10a is formed to be parallel to the lower surface 10b and flat. In other words, the ridgeline portion of the upper surface 10a including the corner blade 10f and the inner cutting edge 10g is located at substantially the same height from the lower surface 10b on the entire circumference thereof. More specifically, the upper surface 10a has a flat surface 10p having a constant height (distance) from the lower surface 10b, and a negative land 10q surrounding the flat surface 10p.

The height from the lower surface 10b of the ridgeline where the negative land 10q and the peripheral side surface (10d, 10d', 10e, 10e') intersect is substantially the same as the flat surface 10p, and is slightly higher than the flat surface 10p. Low. That is, the cutting edge (10f, 10g, 10m) formed on the ridge line portion has a substantially constant distance from the lower surface 10b in the upper surface 10a and all the portions thereof. The difference in height between the cutting edge at the position where the height from the lower surface 10b is the highest and the cutting edge at the position where the height from the lower surface 10b is the lowest is, for example, within 1 mm.

In the example shown in FIG. 4, the shaving blade 10m is formed on the side opposite to the inner cutting blade 10g with the corner blade 10f interposed therebetween. The shaving blade 10m is formed to be much shorter than the corner blade 10f and the inner cutting blade 10g. The other end of the shaving blade 10m is connected to the linear ridge of the upper surface 10a. The ridgeline portion and the shaving blade 10 m intersect at an obtuse angle with an internal angle of almost 180 °.

As shown in FIG. 3, a negative land 10q having a negative angle (θ1 to θ2) is formed on the upper surface 10a adjacent to the cutting edge. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. As shown in FIGS. 6 and 7, the angle of the negative land 10q adjacent to the corner blade 10f is positive from one end 12 connected to the inner cutting edge 10g toward the other end 13 connected to the shaving blade 10m. It gradually increases as it approaches the value of.

In the illustrated example, the angle θ1 of the negative land 10q at the end portion 12 on the inner cutting edge 10 g side shown in FIG. 6 is −20 °. The angle of the negative land 10q gradually increases from θ1 toward the end 13 connected to the shaving blade 10m. The angle θ2 of the negative land 10q at the end portion 13 on the side of the shaving blade 10 m shown in FIG. 7 is −8 °.

Further, the upper surface 10a is composed of a flat surface 10p on which a chip breaker or the like is not formed in most of the portion excluding the through hole H and the negative land 10q. The ratio of the flat surface 10p to the upper surface 10a is 90% or more.

FIG. 8 is a perspective view showing an example of an end mill E to which two cutting inserts 10 are mounted, and FIG. 9 shows a direction in which the tip portion including the tip of the end mill E and a portion in the vicinity thereof is perpendicular to the rotation axis AX. FIG. 10 is a view of the tip end portion of the end mill E as viewed from the rotation axis AX direction. The end mill E is an example of a cutting tool with a replaceable cutting edge. The end mill E shown in FIGS. 8 to 10 is a small end mill E having a tool diameter of 8 mm to 20 mm, and can be used, for example, for machining a mold.

As shown in FIGS. 8 to 10, at the tip of the end mill E, the cylindrical body B is formed with two bearing surfaces F and F'for mounting the cutting insert 10. Female threads are formed on the seat surfaces F and F', respectively. When the clamp screw CS penetrating the through hole H of the cutting insert 10 is screwed with this female screw, the lower surface 10b of the cutting insert 10 is pressed against the bearing surfaces F and F', and each cutting insert 10 is fixed to the body B. Will be done. The base end portion of the end mill E on the side opposite to the tip portion is fixed to a machine tool (not shown).

At this time, the front portion 10e faces the same direction as the rotation axis AX. As described above, the cutting insert 10 is mounted on the body B so that the side surface portion 10d is close to the rotation axis AX and the side surface portion 10d'is far from the rotation axis AX. Therefore, the corner blade 10f and the inner cutting blade 10g exist from the outer peripheral side of the end mill E toward the center.

Hereinafter, the structure for increasing the rigidity of the body B will be described. The cutting insert 10 according to the present embodiment contributes to increasing the rigidity of the body B. Since the width W of the cutting insert 10 is as thin as 4 to 4.5 mm, the body B on which such a cutting insert 10 is mounted is also thin. As the volume of the body B decreases, the rigidity of the body B also decreases.

In addition, when mounting the cutting insert on the body, the corners connecting the insert surface and the wall surface of the chip seat are scooped out to ensure that the side surface of the cutting insert and the wall surface of the tip seat of the body are in contact with each other. A recess) is formed. The inventors of the present application noted that removing the corners of the tip seat to form a dullness affects the rigidity of the body.

Since the cutting insert 10 according to the present embodiment is provided with the inclined portion 10k and the connecting portion 10j, the edge of the lower surface 10b is the lower surface 10b as compared with the normal cutting insert not provided with the inclined portion 10k and the connecting portion 10j. Move to the center side of. Therefore, as shown in FIG. 10, it is possible to reduce the slime formed in the corners C and C'of the tip seat of the body B to which the cutting insert 10 is mounted, that is, to increase the cross-sectional area of the body B. become. Therefore, it becomes possible to increase the rigidity of the body B.

Further, since the width W of the cutting insert 10 is as narrow as 4 to 4.5 mm, the contact area between the seat surface F and the seat surface F'of the insert seat is also limited. If the contact area is too small, the cutting insert cannot be stably attached to the body B. Since the cutting insert 10 is provided with the vertical portion 10h following the inclined portion 10k, it is possible to increase the area of the lower surface 10b as compared with the case where the vertical portion 10h is not provided. Therefore, a large contact area between the seat surface F and the seat surface F'of the tip seat can be secured.

Further, since the peripheral side surface of the inclined portion 10k having a relatively small inclination angle can be brought into contact with the wall surface of the tip seat, it is more stable than the case where the peripheral side surface having a large inclination angle is brought into contact with the wall surface of the tip seat. It becomes possible to support the cutting insert 10. Therefore, the cutting insert 10 according to the present embodiment can achieve both an increase in the rigidity of the body B and a stable mounting.

Next, the effect of this embodiment will be described. The angle (θ1 to θ2) of the negative land 10q formed adjacent to the corner blade 10f is smaller (for example, θ1) as the portion located at the tip of the milling tool. By providing a negative land in which the land angle gradually changes to the positive side as the distance from the tip of the milling tool increases, the chip evacuation property can be improved and the cutting edge strength can be improved.

As a second (secondary) effect of this embodiment, the cutting insert 10 is arranged on the tool body B so as to form a positive axial rake angle, so that a work material that is not a high hardness material can be used. In the case of cutting, if the cutting insert 10 is replaced so that the rake angle becomes a positive angle, the tool body B can be shared with the cutting of a high hardness material and the cutting of another work material.

Further, since the shaving blade 10m is connected to the corner blade 10f, the roughness of the machined surface on the standing wall becomes good. Since the linear ridge line portion connected to the shaving blade 10m and the shaving blade 10m intersect at an obtuse angle, it is possible to prevent the linear ridge line portion from coming into contact with the work. Therefore, it is possible to prevent the linear ridge line portion from coming into contact with the surface of the work and deteriorating the machined surface roughness.

Further, since grooves and irregularities such as a chip breaker are not formed on the upper surface 10a and most of them are composed of a flat surface 10p, the degree of freedom in how to move the grindstone is increased when the negative land 10q is formed by grinding. , Manufacturing cost is reduced. That is, the cutting insert 10 can be manufactured with higher accuracy than the cutting insert having a complicated shape in which a chip breaker or the like is formed.

The present invention can be modified in various ways as long as it does not deviate from the gist thereof. For example, some components in one embodiment may be combined with other embodiments within the normal creative abilities of those skilled in the art.

10 ... Cutting insert, 10a ... Top surface, 10b ... Bottom surface, 10d ... Side part, 10e ... Front part, 10f ... Corner blade, 10g ... Inner cutting blade, 10m ... Smooth blade, 10h ... Vertical part, 10j ... Connection part, 10k ... Inclined portion, 10p ... Flat surface, 10q ... Negative land, 11 ... One end of the inner cutting edge, 12 ... One end of the corner blade (the other end of the inner cutting edge), 13 ... The other of the corner blades End, AX ... Rotating shaft, B ... Body, C ... Corner, E ... End mill (example of milling tool), F ... Seat surface, H ... Through hole, h1, h2, h3 ... Height from the bottom surface , W ... width of cutting insert, Wf ... width of corner blade, α ... first tilt angle, β ... second tilt angle, θ1, θ2 ... negative land angle.

Claims (3)

A cutting insert that is attached to a body that rotates around a rotating shaft and that together with the body constitute a cutting tool with a replaceable cutting edge.
It is provided with a lower surface mounted on the seat surface of the body, an upper surface opposite to the lower surface, a peripheral side surface connecting between the lower surface and the upper surface, and a through hole penetrating from the upper surface to the lower surface .
The cutting edge formed at the ridge line portion where the upper surface and the peripheral side surface intersect has a linearly formed inner cutting edge and an arc-shaped cornering edge.
The corner cutting edge is connected is formed at a position farther from the rotation axis as compared to the inner cutting edge in said cutting edge, in a plan view as viewed from a direction opposite to said upper surface, perpendicular to the front Symbol rotation axis Has a width of 40% or more and 50% or less of the width of the cutting insert in the above.
The upper surface has a negative land formed along the cutting edge and having a negative angle, and a flat surface connected to the negative land and parallel to the lower surface .
When viewed from above, the ratio of the flat surface in the region excluding the through hole from the top surface is 90% or more.
Angle of the negative land is larger so as to approach the positive value I follow the direction from one end portion connected to said cutting edge out of both ends of the corner edge to the other end,
Cutting insert. The cutting edge further has a linear shaving blade connected to the corner blade and parallel to the axis of rotation.
At the ridgeline portion of the shaving blade, the upper surface intersects the shaving blade at an obtuse angle.
The cutting insert according to claim 1. The negative land is formed so as to surround the flat surface.
The ridgeline portion is a portion where the negative land and the peripheral side surface intersect, and is located at substantially the same height from the lower surface on the entire circumference thereof.
In the cutting edge formed on the ridgeline portion, the difference in height between the cutting edge at the position where the height from the lower surface is the highest and the cutting edge at the position where the height from the lower surface is the lowest is Within 1 mm,
The cutting insert according to claim 1 or 2.

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