JP7564493B2 - End Mills - Google Patents

Description

The present invention relates to an unequally divided end mill having a notch (nick) on the peripheral cutting edge.
This application claims priority based on Japanese Patent Application No. 2021-091625 filed in Japan on May 31, 2021, and Japanese Patent Application No. 2021-107997 filed in Japan on June 29, 2021, the contents of which are incorporated herein by reference.

When performing highly efficient cutting, it is known that the occurrence of chatter vibrations can be suppressed by changing the circumferential spacing (partition angle) between the peripheral cutting edges. It is also known that providing a notch (nick) in the peripheral cutting edge can shorten the length of the cutting chips and suppress chipping of the peripheral cutting edge due to the cutting chips getting caught.

JP 2011-000696 A

However, with the demand for further improvements in machining efficiency, even if these technologies are applied, it is difficult to perform cutting for a sufficiently long time while suppressing chipping of the peripheral cutting edge.

The present invention has been made against this background, and aims to provide an end mill that can perform cutting with high efficiency and also has improved resistance to chipping.

An end mill according to one embodiment of the present invention is an end mill having an end mill body having a rotation axis that defines a front end and a rear end, a cutting edge portion formed on the front end side of the end mill body, a plurality of chip discharge grooves that extend while twisting along the rotation axis in the cutting edge portion, and a plurality of peripheral blades formed at the intersecting ridge portion on the forward side in the rotation direction between the chip discharge grooves and the peripheral flank, the cutting edge portion having a plurality of notches that make the peripheral blade discontinuous, a first notch that is located at the rearmost side of all the notches is provided on the first peripheral blade, and in a cross section perpendicular to the axis of the rear end of the cutting edge portion, the division angle of at least one of the peripheral blades is different from the division angles of the other peripheral blades, and the division angle of the first peripheral blade is the smallest.

In this specification, the "dividing angle θ of the peripheral blade" means the circumferential distance between a peripheral blade and the adjacent peripheral blade adjacent to that peripheral blade in front of the rotation direction. More specifically, it means the angle between a line connecting a peripheral blade to the rotation axis and a line connecting the adjacent peripheral blade of that peripheral blade to the rotation axis in a cross section perpendicular to the axis.

The closer the cutting edge is to the rear end, the closer it is to the part that is held by the machine tool, so the stress applied to the peripheral blade during cutting is less likely to be dispersed. Furthermore, since the notch is a cut-out portion of the peripheral blade, stress is likely to concentrate around the notch. On the other hand, in this embodiment, the notch (first notch) is located at the rear end side where stress is least likely to be dispersed, and is also shaped such that stress is likely to concentrate, and is provided on the peripheral blade (first peripheral blade) with the shortest cutting distance. This reduces the load acting on the peripheral blade around the first notch, effectively suppressing chipping at the axial rear end side, where chipping is particularly likely to occur among the peripheral blades. As a result, more efficient cutting is possible while suppressing chipping of the peripheral blade.

In one aspect of the present invention, each of the cutouts may have a non-cutting area on an extension of the peripheral cutting edge, and the circumferential positions of all of the non-cutting areas within the cutting edge portion may not overlap with each other.

As described above, by arranging the non-cutting areas so that the circumferential positions of all non-cutting areas in the cutting edge portion do not overlap each other, during cutting, the workpiece does not face multiple non-cutting areas at the same time, but either faces one non-cutting area or does not face any non-cutting area at all. Therefore, the amount of change in cutting resistance received by the cutting edge portion during cutting is small, and the timing at which the cutting resistance changes is also distributed over many times, so that the fluctuation in cutting resistance can be kept small. As a result, even if the feed rate and cutting speed are significantly increased, chatter vibration is unlikely to occur. Furthermore, even if the axial cutting depth is significantly increased and many notches are provided, regardless of the number of notches, the fluctuation in cutting resistance during cutting can be kept small, and chatter vibration is unlikely to occur. Due to these synergistic effects, by arranging the non-cutting areas so that the circumferential positions of all non-cutting areas in the cutting edge portion do not overlap each other, it is possible to perform cutting with even higher efficiency while suppressing chipping of the peripheral cutting edge.

In one aspect of the present invention, the circumferential positions of all of the notches within the cutting edge portion may be configured so as not to overlap with each other.

This configuration spreads out the timing at which the cutting resistance changes, making it possible to further suppress the occurrence of chatter vibrations. As a result, more efficient cutting is possible while suppressing chipping of the peripheral cutting edge.

In one aspect of the present invention, at least one of the circumferential intervals between the rotational front ends of two adjacent notches may be configured to be different from the other circumferential intervals. By configuring in this way, the periodicity of the timing at which the cutting resistance decreases can be alleviated. Chatter vibration is less likely to occur, and chipping of the peripheral cutting edge is suppressed, enabling more efficient machining.

In one aspect of the present invention, the axial length (blade length) of the peripheral cutting edge may be configured to be at least twice the blade diameter. Conventionally, the longer the blade length, the higher the machining efficiency, but the greater the stress acting on the end mill body. In addition, the stress is less likely to be dispersed in the cutting edge, particularly in the area closer to the grip of the machine tool (the area closer to the axial rear end), making chipping more likely to occur. Furthermore, stress is more likely to concentrate around the notch, making chipping more likely to occur.
On the other hand, in this embodiment, the cutting length of the peripheral cutting edge is set to be at least twice the cutting diameter, and the notch located at the rear end is provided on the peripheral cutting edge having the smallest division angle (cutting distance) in the cross section perpendicular to the axis of the rear end of the cutting edge portion. As a result, even if the cutting length is increased and the amount of cut in the axial direction is increased, chipping in the area where chipping is likely to occur can be effectively suppressed by reducing the cutting load near the notch located at the rear end, where stress is least likely to be dispersed and concentrated. As a result, it is possible to perform more efficient machining while suppressing the occurrence of chipping on the peripheral cutting edge.

In one aspect of the present invention, the number of the peripheral cutting edges may be five or more. Conventionally, the more the number of cutting edges is increased and the feed rate is increased, the more the machining efficiency improves, but the contact distance with the workpiece per unit time increases, and the stress acting on the end mill body also increases. In particular, the closer to the grip of the machine tool (the closer to the axial rear end) in the cutting edge portion, the less the stress is dispersed, and chipping is more likely to occur. Furthermore, since there is no peripheral cutting edge in the notch portion, stress is likely to concentrate around the notch portion, and chipping is more likely to occur.
On the other hand, in this embodiment, five or more peripheral blades are provided, and the notch located at the rear end is provided on the peripheral blade with the smallest division angle (cutting distance) in the cross section perpendicular to the axis of the rear end of the cutting blade. As a result, even if the number of blades is increased and the feed speed is increased, chipping in the area where chipping is likely to occur can be effectively suppressed by reducing the cutting load near the notch located at the rear end, where stress is least likely to be dispersed and concentrated. As a result, more efficient machining is possible while suppressing chipping of the peripheral blade.

In one aspect of the present invention, the helix angles of all of the peripheral cutting edges may be 35° or greater.
Conventionally, the larger the helix angle, the higher the feed rate and the higher the machining efficiency, but the greater the contact distance with the workpiece, which increases the stress acting on the end mill body. In particular, the closer to the grip of the machine tool (the rear end in the axial direction) in the cutting edge, the less the stress is dispersed, making chipping more likely to occur. Furthermore, since there is no peripheral cutting edge in the notch, stress tends to concentrate around the notch, making chipping more likely to occur.
On the other hand, in this embodiment, the notch located at the rear end side is provided on the peripheral cutting edge having the smallest division angle (cutting distance) in the cross section perpendicular to the axis of the rear end of the cutting edge part, so that even if the helix angle is increased and the feed rate and cutting speed are increased, the cutting load near the notch located at the rear end side, where stress is least likely to be dispersed and most likely to be concentrated, can be reduced. This makes it possible to effectively suppress chipping in areas where chipping is likely to occur. As a result, more efficient machining is possible while suppressing the occurrence of chipping on the peripheral cutting edge.

In one aspect of the present invention, the helix angles of all of the peripheral cutting edges may be equal to each other.
This configuration makes it easier to manufacture and also reduces chatter vibration, making it possible to achieve more efficient machining while suppressing chipping of the peripheral cutting edge.
Conventionally, it has been known that a complex configuration in which the twist angles between the peripheral cutting edges are made different can suppress the occurrence of chatter vibrations and make chipping less likely, even when highly efficient cutting is performed.
On the other hand, in this embodiment, the notch located at the rear end side is provided on the peripheral cutting edge having the smallest division angle in the cross section perpendicular to the axis of the rear end of the cutting edge portion, so that even if all the twist angles are made equal, the cutting load near the notch located at the rear end side, where stress is least likely to be dispersed and most likely to concentrate, can be reduced. This makes it possible to effectively suppress chipping in areas where chipping is likely to occur. As a result, with a simpler configuration, it is possible to suppress chipping of the peripheral cutting edge and perform more efficient machining.

In one aspect of the present invention, the cutout portion may be arranged so that the maximum cutting edge length continuing in the extension direction of the peripheral cutting edge is 2.7 times or less the cutting diameter D.
Conventionally, when so many notches were provided that the maximum cutting edge length of the peripheral blade was 2.7 times or less the blade diameter D, notches were also provided toward the rear end of the cutting edge, which could make chipping more likely to occur at the rear end of the cutting edge.
On the other hand, in this embodiment, the notch located at the rear end side is provided on the peripheral blade having the smallest division angle in the cross section perpendicular to the axis of the rear end of the cutting edge portion, so even if the notch is located further rearward so that the maximum cutting edge length of the peripheral blade is 2.7 times or less than the blade diameter D, the cutting load near the notch located at the rear end side, where stress is least likely to be dispersed and most likely to concentrate, can be reduced. This makes it possible to effectively suppress chipping in areas where chipping is likely to occur. As a result, more efficient cutting is possible while suppressing chipping of the peripheral blade.

The cutouts may be arranged so that the minimum cutting edge length continuing in the direction of extension of the peripheral cutting edge is 0.6 times or more the blade diameter.
According to this configuration, an excessive number of notches can be prevented and the occurrence of chatter vibration can be further suppressed, thereby further suppressing chipping of the peripheral cutting edge.

In one aspect of the present invention, the cutouts may be arranged such that the cutouts closest to each other in an axial direction are different from the cutouts closest to each other in a circumferential direction.
According to this configuration, the cutouts can be arranged at appropriate intervals in the circumferential direction, which reduces the likelihood of there being locations where the fluctuation in cutting resistance is locally large during cutting, and reduces the likelihood of chatter vibrations.

In one aspect of the present invention, the outer blade is right-handed, and all of the notches are configured so that, of two notches adjacent to each other in the axial direction, the notch located at the rear end is located forward in the direction of rotation than the notch located at the tip end.
In a right-handed end mill, when the notches are arranged in such a right-downward direction in the opposite direction to the twist direction of the peripheral cutting edge, the circumferential interval between adjacent notches 8 can be made smaller, and the notches can be arranged at a higher density. As a result, in such a right-downward arrangement, the circumferential positions of all the notches (and non-cutting regions) in the cutting edge portion do not overlap with each other, and more notches can be arranged. The longer the axial length of the cutting edge portion, the more the number of notches must be increased so as not to increase the chip length, and the larger the cutting diameter, the larger the dimensions of the notches must be. Therefore, in such cases, the right-downward arrangement is particularly preferable.

According to one aspect of the present invention, an end mill can be provided that can perform cutting with high efficiency and improve chipping resistance.

FIG. 1 is a diagram showing a configuration of an end mill according to the first embodiment. FIG. 2 is a perspective view showing the configuration of the end mill in the first embodiment. FIG. 3 is a cross-sectional view perpendicular to the axis of the cutting edge portion 3 of the end mill in the first embodiment at the axial rear end thereof. FIG. 4 is an enlarged view of the periphery of the cutout portion of the first embodiment. FIG. 5 is a development view showing the entire outer circumferential surface of the cutting edge portion of the end mill in the first embodiment. FIG. 6 is a development view showing the entire outer circumferential surface of the cutting edge portion of the end mill in the second embodiment.

Below, the configuration of the end mill of each embodiment of the present invention is explained with reference to the drawings.

[First embodiment]
Fig. 1 is a diagram showing the configuration of an end mill 10 according to a first embodiment. Fig. 2 is a perspective view showing the configuration of the end mill 10 according to the first embodiment.

The end mill 10 of this embodiment shown in FIG. 1 has an end mill body 1 having a rotation axis (axis O) that defines the tip and rear end. The end mill body 1 is formed of a hard material such as cemented carbide into a generally cylindrical shape with an outer diameter centered on axis O. The rear end portion of the end mill body 1 (the shank portion 2, which is the upper portion in FIG. 1) remains cylindrical. The tip portion of the end mill body 1 (the cutting blade portion 3, which is the lower portion in FIG. 1) has a chip discharge groove 4 and an outer peripheral flank 11 formed by grinding the end mill body 1, and an outer peripheral blade 7 is formed at the intersection ridge portion between the chip discharge groove 4 and the outer peripheral flank 11 on the forward side in the direction of rotation.

Such an end mill body 1 is gripped by the spindle of a machine tool at the shank portion 2 and rotated around the axis O in the end mill rotation direction T, so that it is sent out, for example, in a direction perpendicular to the axis O to perform cutting on the workpiece.

The chip discharge grooves 4 extend around the outer periphery of the cutting edge portion 3, twisting around the axis in the opposite direction to the end mill rotation direction T, from the axial tip to the rear end of the cutting edge portion 3. In this embodiment, five chip discharge grooves 4 are formed at intervals in the circumferential direction.

The peripheral blade 7 is formed on the intersection ridge on the forward side in the rotation direction between the rake face 12, which is a wall surface facing forward in the end mill rotation direction T of the chip discharge groove 4, and the peripheral relief surface 11, which is the outer peripheral surface of the cutting blade portion 3 adjacent to the rake face 12. In this embodiment, the cutting blade portion 3 has five peripheral blades 7. In addition, the cutting blade portion 3 has multiple notches 8 that make the peripheral blade 7 discontinuous in the extension direction of the peripheral blade 7. In this embodiment, a case where all peripheral blades 7 have one or more notches 8 is exemplified, but in the embodiment of the present invention, it is sufficient that the cutting blade portion 3 has multiple notches 8, and there may be a peripheral blade 7 that does not have a notch 8. The peripheral blade 7 extends in a straight line.

As shown in Figure 2, at the tip of each chip discharge groove 4, a concave-groove-shaped gash 5 is formed along the wall surface of the chip discharge groove 4 facing forward in the end mill rotation direction T. The end mill body 1 has five gashes 5. At the tip edges of the wall surfaces of these gashes 5 facing the end mill rotation direction T, bottom cutting edges 6 are formed with the wall surfaces as cutting surfaces, extending inward from the tips of each peripheral cutting edge 7.

In this embodiment, each peripheral blade 7 has a constant twist angle along the extension direction of the peripheral blade 7 (in other words, from the axial tip to the rear end). In addition, the twist angles of all peripheral blades 7 in the cutting edge portion 3 are equal to each other.

3 is a cross-sectional view perpendicular to the axis at the axial rear end of the cutting edge portion 3 of the end mill in the first embodiment. In this specification, the division angle (cutting distance) of a certain peripheral blade 7 means the angle between the line connecting the peripheral blade 7 and the axis O and the line connecting the peripheral blade 7 and the adjacent peripheral blade 7 forward in the rotational direction and the axis O.

In Figure 3, the five peripheral blades 7 arranged in the circumferential direction are named, in the direction of end mill rotation T, as the first peripheral blade 7A, the second peripheral blade 7B, the third peripheral blade 7C, the fourth peripheral blade 7D, and the fifth peripheral blade 7E. In addition, the straight lines connecting the first peripheral blade 7A to the fifth peripheral blade 7E with the axis O are named the first straight line R1, the second straight line R2, the third straight line R3, the fourth straight line R4, and the fifth straight line R5, respectively. In addition, the angle formed by the first line R1 and the second line R2 is called the division angle θ1 of the first peripheral blade 7A, the angle formed by the second line R2 and the third line R3 is called the division angle θ2 of the second peripheral blade 7B, the angle formed by the third line R3 and the fourth line R4 is called the division angle θ3 of the third peripheral blade 7C, the angle formed by the fourth line R4 and the fifth line R5 is called the division angle θ4 of the fourth peripheral blade 7D, and the angle formed by the fifth line R5 and the first line R1 is called the division angle θ5 of the fifth peripheral blade 7E.

As shown in Figure 3, in this embodiment, the division angles θ of all peripheral blades 7 are different from each other in the cross section perpendicular to the axis at the rear end of the cutting portion 3. In other words, the end mill 10 is an unequal division end mill. By making the division angle θ of at least one peripheral blade 7 different from the division angles θ of the other peripheral blades 7, the occurrence of chatter vibration can be suppressed.

The division angles of each peripheral blade 7A to 7E increase in the order θ1 < θ3 < θ4 < θ5 < θ2. In other words, the division angle θ1 of the first peripheral blade 7A is the smallest of the division angles θ of all the peripheral blades 7. The cutting distance of each peripheral blade 7A to 7E is proportional to the peripheral blade spacing (division angle θ) of each peripheral blade. Therefore, the cutting distance of the first peripheral blade 7A is the shortest of all the peripheral blades 7A to 7E.

FIG. 4 is an enlarged view of the periphery of the cutout portion 8 in the first embodiment.
As shown in FIG. 4, the notch 8 is a portion that makes the peripheral blade 7 discontinuous in the extension direction of the peripheral blade 7, and has a non-cutting region 9 that is a portion (line) corresponding to the extension line of the peripheral blade 7. Each notch 8 extends from one chip discharge groove 4 to the other chip discharge groove 4 adjacent in the circumferential direction so as to cross the outer flank 11 in the circumferential direction, and is a concave groove recessed radially inward. The notch 8 connects one chip discharge groove 4 to the other chip discharge groove 4 adjacent in the circumferential direction. The notch 8 opens at the rake face 12 of the peripheral blade 7 that constitutes the wall surface of one chip discharge groove 4, and also opens at the wall surface 13 that constitutes the other chip discharge groove 4 adjacent in the circumferential direction to the one chip discharge groove 4, and also opens at the flank 11. Each notch 8 extends parallel to the end mill rotation direction T. Each notch 8 has the same shape on the rake face 12 of the peripheral cutting edge 7 .

In this embodiment, the notch 8 is configured as described above, but the notch 8 may have any shape and circumferential length as long as it makes the peripheral cutting edge 7 discontinuous. For example, the notch 8 does not need to cross the entire peripheral flank 11, and does not need to reach the other chip discharge groove 4 (wall surface 13). The end of the notch 8 on the rear side in the end mill rotation direction T may be located on the peripheral flank 11.

Fig. 5 is a schematic development of the entire outer circumferential surface of the cutting edge portion 3 of the first embodiment. The right end of Fig. 5 is continuous with the left end of Fig. 5. The lower side of Fig. 5 is the tip side of the cutting edge portion 3, and the upper side of Fig. 5 is the rear end side of the cutting edge portion 3.
In this embodiment, the cutting portion 3 has five outer peripheral blades 7A to 7E, and each of the outer peripheral blades 7A to 7E is provided with at least one notch 8.

In this embodiment, the cutting blade portion 3 has eight notches 8, the three outer peripheral blades 7 each have two notches 8, and the two outer peripheral blades 7 each have one notch 8. More specifically, the first outer peripheral blade 7A has a notch 8Aa located at the tip side and a notch 8Ab located at the rear end side. The second outer peripheral blade 7B has a notch 8Ba located at the tip side and a notch 8Bb located at the rear end side. The third outer peripheral blade 7C has a notch 8Ca located at the tip side and a notch 8Cb located at the rear end side. The fourth outer peripheral blade 7D has only a notch 8D. The fifth outer peripheral blade 7E has only a notch 8E.

In this embodiment, the notch 8Ab located furthest from the axial rear end of all the notches 8 in the cutting blade portion 3 is provided on the first peripheral blade 7A having the smallest division angle θ1 in the cross section perpendicular to the axial rear end of the cutting blade portion 3. In other words, the notch 8Ab located furthest from the axial rear end of all the notches 8 in the cutting blade portion 3 is provided on the peripheral blade 7A with the smallest cutting distance at the axial rear end of the cutting blade portion 3.

The end mill 10 is closer to the area held by the machine tool toward the rear end in the axial direction, so stress is less likely to be dispersed. Also, since the notch 8 is an area where the peripheral cutting edge 7 does not exist, stress is likely to be concentrated on the peripheral cutting edge near the notch 8.
However, as in this embodiment, by providing the notch 8Ab located at the rear end side of all the notches 8 on the peripheral cutting edge 7A having the smallest division angle θ1 in the cross section perpendicular to the axis at the rear end of the axial direction of the cutting edge portion 3, the cutting load near the notch 8Ab located at the rear end side, where stress is least likely to be dispersed and most likely to be concentrated, can be reduced. This makes it possible to effectively suppress chipping in areas where chipping is likely to occur. As a result, it is possible to suppress the occurrence of chipping of the peripheral cutting edge 7 even in extremely efficient machining. Examples of extremely efficient machining include cutting conditions in which the axial cutting depth (ap) is twice or more the cutting diameter (D), cutting conditions in which the cutting speed (Vc) is 250 m/min or more, cutting conditions in which the chip removal rate (Q) is 250 cm ³ /min or more, or cutting conditions in which two or more of these three conditions are combined.

In this embodiment, the division angles θ1 to θ5 of the five peripheral blades 7A to 7E are different from each other, but in the embodiment of the present invention, it is sufficient that the division angle θ of at least one peripheral blade 7 is different from the division angle θ of the other peripheral blades 7, and there may be multiple peripheral blades 7 with the smallest division angle θ. If there are multiple peripheral blades 7 with the smallest division angle θ, the notch 8 located at the rear end side may be provided on one of the peripheral blades 7 with the smallest division angle θ.

In this embodiment, each peripheral blade 7 has a constant twist angle along the extension direction of the peripheral blade 7, and the twist angles of all peripheral blades 7 are equal to each other. Therefore, not only in the axis-perpendicular cross section at the axial rear end shown in FIG. 3, but also in the axis-perpendicular cross section at any axial position, the division angles θ1 to θ5 of the peripheral blades 7A to 7E increase in the order of θ1 < θ3 < θ4 < θ5 < θ2. In this embodiment, it is sufficient that the division angle of at least one peripheral blade 7 is different in the axis-perpendicular cross section at the axial rear end of the cutting edge portion 3, and the twist angle does not have to be constant in the extension direction of the peripheral blade 7, and the twist angles may differ between the peripheral blades 7.

As shown in Figure 5, the circumferential positions CQ of each of the non-cutting regions 9Aa to 9E in the cutting edge portion 3 are arranged in the following order toward the rear in the rotational direction: non-cutting regions 9Aa, 9Bb, 9E, 9Ab, 9Ca, 9D, 9Ba, 9Cb. The circumferential positions CQ of all of the non-cutting regions 9 in the cutting edge portion 3 do not overlap with each other.

In this specification, "the circumferential positions CR of all the non-cutting regions 9 in the cutting blade portion 3 do not overlap" means that when all the non-cutting regions 9 in the cutting blade portion 3 are projected onto a plane perpendicular to the same axis, the areas occupied by the non-cutting regions 9 do not overlap with each other. In addition, in this specification, the "non-overlapping" arrangement does not include overlapping arrangements, but includes separated arrangements and adjacent arrangements. In other words, during cutting, the workpiece does not face multiple non-cutting regions 9 at the same time, but either faces one non-cutting region 9 or does not face any non-cutting region 9 at all. The circumferential position of the notch can also be expressed as an angle range with the axis as the center and any location on the outer circumferential surface as 0°. For example, the circumferential position of a certain notch can be expressed as an angle range of 0° to 5°, and the circumferential position of the notch adjacent to that notch in the circumferential direction can be expressed as 10° to 15°. This allows the circumferential position to be expressed regardless of the presence or absence of a back taper.

The non-cutting regions 9 are regions where the peripheral cutting edge 7 does not exist, and therefore reduce the cutting resistance. Therefore, the greater the number of non-cutting regions 9 that face the workpiece at the same time, the smaller the cutting resistance that the cutting edge portion 3 experiences. In other words, when the number of notches 8 provided in the cutting edge portion 3 is the same, the greater the number of non-cutting regions 9 that face the workpiece at the same time, the greater the change in cutting resistance that the end mill 10 experiences during cutting.

In this embodiment, since the circumferential positions CQ of all non-cutting regions 9 in the cutting blade portion 3 do not overlap with each other, during cutting, the workpiece does not face multiple non-cutting regions 9 at the same time, but either faces one non-cutting region 9 or does not face any non-cutting region 9 at all. Therefore, the amount of change in cutting resistance during cutting received by the end mill 10 is small, and the timing at which the cutting resistance changes is also finely distributed, so that the fluctuation in cutting resistance can be kept small. As a result, even if the feed rate and cutting speed are significantly increased, chatter vibration is unlikely to occur. Furthermore, even if the axial cutting depth is significantly increased and many notches 8 are provided, regardless of the number of notches 8, the fluctuation in cutting resistance during cutting can be kept small, and chatter vibration is unlikely to occur. Due to these synergistic effects, by arranging the non-cutting regions 9 so that the circumferential positions CQ of all non-cutting regions 9 in the cutting blade portion 3 do not overlap with each other, it is possible to perform cutting with even higher efficiency while suppressing chipping of the peripheral cutting edge 7.

Furthermore, in this embodiment, the circumferential positions CR of all notches 8 within the cutting edge portion 3 do not overlap.

In this specification, "the circumferential positions CR of all the notches 8 in the cutting edge portion 3 do not overlap" means that when all the notches 8 in the cutting edge portion 3 are projected onto a plane perpendicular to the same axis, the areas occupied by each notch 8 do not overlap with each other. The "non-overlapping" arrangement does not include overlapping arrangements, but includes arrangements that are spaced apart and adjacent arrangements. In other words, during cutting, the workpiece does not face multiple notches 8 at the same time, but either faces one notch 8 or does not face any notch 8 at all. The circumferential position of the notch can also be expressed as an angle range with the axis as the center and any location on the outer circumferential surface as 0°. For example, the circumferential position of a certain notch can be expressed as an angle range of 0° to 5°, and the circumferential position of the notch adjacent to that notch in the circumferential direction can be expressed as 10° to 15°. This allows the circumferential position to be expressed regardless of the presence or absence of a back taper.

This configuration spreads out the timing at which the cutting resistance changes, making it possible to further suppress the occurrence of chatter vibrations. As a result, more efficient cutting is possible while suppressing chipping of the peripheral cutting edge 7.

In addition, at least one of the circumferential intervals CS between the rotational front ends of two notches 8 that are adjacent in circumferential position is different from the other circumferential intervals CS. In other words, at least one of the circumferential intervals CS between the rotational front ends of two non-cutting regions 9 that are adjacent in circumferential position is different from the other circumferential intervals CS. For example, if the cutting edge portion 3 has eight notches 8, there are eight circumferential intervals CS, and at least one of the eight circumferential intervals CS is different from the other circumferential intervals CS. For example, the circumferential interval CS between the rotational front end of the notch 8Aa and the rotational front end of the notch 8Bb is different from the circumferential interval CS between the rotational front end of the notch 8Bb and the rotational front end of the notch 8E. By configuring at least one circumferential spacing CS to be different from the other circumferential spacings CS in this manner, the timing at which the cutting resistance decreases can be made more irregular, making it less likely for chatter vibration to occur and enabling more efficient machining while suppressing chipping of the peripheral cutting edge 7.

In this embodiment, the end mill body 1 has a diameter (D: blade diameter) at the tip of the cutting edge portion 3 of approximately 10 mm, and an axial length of the peripheral blade 7 (length when the peripheral blade 7 is projected onto a straight line parallel to the axis O) (H: blade length) of approximately 30 mm. The blade diameter D may be, for example, 6 mm or more. In this embodiment, the case where the blade length H = 3D is exemplified, but the blade length H may be 2.5D or more.

Conventionally, the longer the cutting edge length H, the higher the machining efficiency, but the greater the stress acting on the end mill body 1, and the more difficult it is to disperse the stress in the cutting edge portion 3, particularly in the area closer to the grip of the machine tool (toward the rear end in the axial direction), making chipping more likely to occur. Furthermore, since the peripheral cutting edge 7 does not exist in the notch portion 8, stress tends to concentrate around the notch portion 8, making chipping more likely to occur.
On the other hand, in this embodiment, the cutting length H of the peripheral cutting edge 7 is set to 2.5 times or more the cutting diameter D, and the notch 8Ab located at the rear end side is provided on the peripheral cutting edge 7A having the smallest division angle θ1 (cutting distance) in the axial cross section at the rear end of the cutting edge portion 3. As a result, even if the cutting length H is lengthened to increase the amount of cut in the axial direction, the cutting load near the notch 8Ab located at the rear end side, where stress is least likely to be dispersed and most likely to concentrate, can be reduced, and chipping in the area where chipping is likely to occur can be effectively suppressed. As a result, more efficient machining is possible while suppressing the occurrence of chipping of the peripheral cutting edge 7.

In this embodiment, five peripheral blades 7 are provided, but the number of peripheral blades 7 is not limited to five and may be six or more.
Conventionally, the more the number of teeth is increased and the faster the feed rate is, the more the machining efficiency improves, but the more the stress acting on the end mill body 1 increases. Moreover, the closer the cutting edge portion 3 is to the gripping portion of the machine tool (the closer to the axial rear end), the less the stress is dispersed, and chipping is more likely to occur. Furthermore, since the peripheral cutting edge 7 is not present in the notch portion 8, stress is likely to concentrate around the notch portion 8, and chipping is more likely to occur.
On the other hand, in this embodiment, five or more peripheral blades 7 are provided, and the notch 8Ab located at the rear end side is provided on the peripheral blade 7A having the smallest division angle θ1 (cutting distance) in the axis-perpendicular cross section at the rear end of the cutting blade portion 3. As a result, even if the number of blades is increased and the feed speed is increased, the cutting load near the notch 8Ab located at the rear end side, where stress is least likely to be dispersed and concentrated, can be reduced, and chipping in areas where chipping is likely to occur can be effectively suppressed. As a result, more efficient machining is possible while suppressing the occurrence of chipping of the peripheral blade 7.

In this embodiment, all the peripheral blades 7 have a constant twist angle of 40° along the extension direction of the peripheral blade 7. The twist angle is preferably 35° or more.
Conventionally, the larger the helix angle, the higher the machining efficiency, but the greater the contact distance with the workpiece, which increases the stress acting on the end mill body 1. Furthermore, the closer the cutting edge 3 is to the grip of the machine tool (the closer to the axial rear end), the harder it is to disperse stress, making chipping more likely to occur. Furthermore, since the peripheral cutting edge 7 does not exist in the notch 8, stress tends to concentrate around the notch 8, making chipping more likely to occur.
On the other hand, in this embodiment, the helix angle is set to 35° or more, and the notch 8Ab located at the rear end side is provided on the peripheral cutting edge 7A having the smallest division angle θ1 (cutting distance). As a result, even if the helix angle is increased and the feed rate and cutting speed are increased, the cutting load near the notch 8Ab located at the rear end side, where stress is least likely to be dispersed and concentrated, can be reduced, and chipping in the area where chipping is likely to occur can be effectively suppressed. As a result, more efficient machining is possible while suppressing the occurrence of chipping of the peripheral cutting edge 7.

In this embodiment, the helix angles of all the peripheral cutting edges 7 are equal to one another. With this configuration, the manufacturing process can be simplified.
Conventionally, it has been known that a complex configuration in which the twist angles between the peripheral cutting edges 7 are made different can suppress the occurrence of chatter vibrations and make chipping less likely, even when highly efficient cutting is performed.
In this embodiment, the notch 8Ab located at the rear end side is provided on the peripheral cutting edge 7A having the smallest division angle θ1 in the cross section perpendicular to the axis at the rear end of the cutting edge portion 3, so that even if all the twist angles are made equal, the cutting load itself near the notch 8Ab located at the rear end side, where stress is least likely to be dispersed and most likely to concentrate, can be reduced, and chipping in the area where chipping is likely to occur can be effectively suppressed. As a result, with a simpler configuration, it is possible to perform more efficient machining while suppressing the occurrence of chipping of the peripheral cutting edge 7.

Also, as shown in FIG. 5, the cutting edge length L2 of the peripheral blade 7 continuing in the extension direction of the peripheral blade 7 corresponds to the chip length. The chip length can be changed by the arrangement of the notches 8 provided on each peripheral blade 7. In this embodiment, the maximum cutting edge length L2 MAX (i.e., the maximum chip length) in the end mill body 1 of the cutting edge length L2 of the peripheral blade 7 continuing in the extension direction of the peripheral blade 7 without being divided by the notches 8 is 24.8 _mm (2.5D), which is the distance from the rear end of the non-cutting area 9E provided on the fifth peripheral blade 7E to the rear end of the fifth peripheral blade 7E, as shown in FIG. 5. In addition, the minimum cutting edge length L2 MIN in the end mill body 1 of the cutting edge length L2 of the peripheral blade 7 continuing in the extension direction of the peripheral blade 7 without being divided by the notches 8 is 9.1 _mm (0.9D), which is the distance from the tip of the third peripheral blade 7C to the tip of the non-cutting area 9Ca.

In this manner, the notch 8 is disposed so that the maximum cutting edge length of the peripheral cutting edge is 2.7 times or less (2.7D or less) the cutting edge diameter D. With such a configuration, chips are less likely to get caught.
Conventionally, when so many notches 8 are provided that the maximum cutting edge length _L2MAX of the peripheral cutting edge 7 is 2.7 times or less than the cutting edge diameter D, the notches 8 are provided further toward the rear end, which may increase the risk of chipping.
In this embodiment, the notch 8Ab located at the rear end side is provided on the peripheral cutting edge 7A having the smallest division angle θ1 in the cross section perpendicular to the axis at the rear end of the cutting edge portion 3, so that even if the notch 8 is located further rearward so that the maximum cutting edge length _L2MAX of the peripheral cutting edge 7 is 2.7 times or less (2.7D or less) the cutting diameter D, the cutting load near the notch 8Ab located at the rear end side, where stress is least likely to be dispersed and most likely to concentrate, can be reduced, and chipping in the area where chipping is likely to occur can be effectively suppressed. As a result, more efficient cutting is possible while suppressing chipping of the peripheral cutting edge 7.

In addition, it is preferable to arrange the notches 8 so that the minimum continuous cutting edge length _L2MIN is 0.6 times or more the cutting edge diameter D of the end mill body 1. This configuration prevents the number of notches from becoming excessive and further suppresses the occurrence of chatter vibration, thereby further suppressing chipping of the peripheral cutting edge.

Furthermore, by arranging the notch 8 so that the maximum continuous cutting edge length L2 _MAX is 2.7 times or less the blade diameter and the minimum continuous cutting edge length L2 _MIN is 0.6 times or more the blade diameter, it is possible to provide an appropriate degree of variation in the continuous cutting edge length L2 within the end mill body, and to further suppress chipping of the peripheral cutting edge 7.

The notch 8 has an arc-shaped cross section at the deepest position (hereinafter, deepest part P) on the rake face 12 in the direction perpendicular to the peripheral cutting edge 7. As shown in FIG. 5, most of the axial spacing L1 between the deepest parts P of two notches 8 adjacent to each other in the axial direction is equally spaced. In this embodiment, the axial spacing L1 between the two deepest parts P adjacent to each other in the axial direction is 1.5 mm. By making the spacing (pitch) of the two notches 8 adjacent to each other in the axial direction equal, it is possible to prevent the occurrence of uneven cutting loads between the peripheral cutting edges 7 during the cutting rotation of the end mill body 1.

The notch 8 closest to each cutout 8 in the axial direction and the notch 8 closest to each cutout 8 in the circumferential direction are arranged so that they are different from each other. For example, for cutout 8Ba, the notches 8Aa and 8Ca are closest in the axial direction, but the notches 8Eb and 8Ab are closest in the circumferential direction, and the two are different from each other. With this configuration, the cutouts 8 can be arranged at an appropriate interval in the circumferential direction, and during cutting, there are less likely to be places where the cutting resistance fluctuates locally, making it less likely that chatter vibrations will occur.

[Second embodiment]
Next, the configuration of the end mill of the second embodiment will be described.
FIG. 6 is a development view of the entire cutting blade portion 3 of the end mill body 21 of the second embodiment.
The end mill body 21 of the second embodiment differs from the first embodiment in the blade diameter D, blade length H, number of notches 8, and arrangement of the notches 8. Note that, in the second embodiment, the number of blades, the twist angle, and the division angle θ of each peripheral blade 7 are the same as those in the first embodiment. Also, as in the first embodiment, the notch 8Ab located at the rearmost side of all the notches 8 is provided on the first peripheral blade 7A having the smallest division angle θ1 in the axis-perpendicular cross section at the rear end of the cutting portion 3.
Also, in the second embodiment, as in the first embodiment, the circumferential positions CQ of all non-cutting regions 9 within the cutting edge portion 3 do not overlap with each other, and the circumferential positions CR of all notches 8 within the cutting edge portion 3 also do not overlap with each other.

First, the blade diameter D and blade length H in this embodiment are larger than those in the first embodiment, with the blade diameter D being approximately 20 mm and the blade length H being approximately 60 mm. In addition, the number of notches 8 provided in the cutting blade portion 3 in this embodiment is greater than that in the first embodiment, with 12 notches 8 provided. The first peripheral blade 7A and the fifth peripheral blade 7E each have three notches 8, while the second peripheral blade 7B, the third peripheral blade 7C and the fourth peripheral blade 7D each have two notches 8.

In addition, in the above first embodiment, as shown in Figure 5, all of the notches 8 in the cutting edge portion 3 of the end mill body 1 are arranged such that, of two notches 8 adjacent to each other in the axial direction, the notch 8 located at the rear end is located further rearward in the rotational direction than the notch 8 located at the tip end (right-upward arrangement).
On the other hand, in this embodiment, as shown in Fig. 6, all the notches 8 in the cutting blade portion 3 of the end mill body 21 are arranged so that, of two notches 8 adjacent in the axial direction, the notch 8 located at the rear end side is located forward in the rotation direction than the notch 8 located at the tip side (right-downward arrangement). In other words, all the notches 8 are arranged in a direction approaching the blade tip as they move toward the opposite side of the end mill rotation direction T (a tilt direction opposite to the tilt direction of the peripheral cutting edge 7) as shown by the arrow F in Fig. 6. In a right-handed twist end mill, such a right-downward arrangement can reduce the circumferential interval between the notches 8 adjacent in the circumferential position, and the notches 8 can be arranged at a higher density. As a result, such a right-downward arrangement can arrange more notches 8 without the circumferential positions of all the notches 8 (and the non-cutting region 9) in the cutting blade portion 3 overlapping with each other.

In addition, the longer the blade length H, the more the number of notches 8 must be increased so that the chip length L2 does not become too long. Even in such a case, the right-downward arrangement allows the notches 8 to be arranged more densely in the circumferential direction. Therefore, even if the number of notches 8 is increased, it is easy to form the required number of notches 8 without overlapping the circumferential positions of all the notches 8 (and the non-cutting areas 9) in the cutting blade portion 3. As a result, chatter vibration is less likely to occur, and more efficient cutting is possible while suppressing chipping of the peripheral blade 7. The right-downward arrangement is particularly preferable for end mills whose blade length H is twice or more, especially three times or more, the blade diameter D.

In addition, the larger the blade diameter D, the larger the dimensions of the notches 8 must be. Even in such a case, the right-downward arrangement allows the notches 8 to be arranged more densely in the circumferential direction. Therefore, even if the dimensions of the notches 8 are increased, it is easy to form the required number of notches 8 without overlapping the circumferential positions of all the notches 8 (and non-cutting areas 9) within the cutting blade portion 3. As a result, chatter vibration is less likely to occur, and more efficient cutting is possible while suppressing chipping of the peripheral cutting edge 7. The right-downward arrangement is particularly preferable for end mills with a blade diameter D of 12 mm or more.

Although the preferred embodiments of the present invention have been described above with reference to the attached drawings, it goes without saying that the present invention is not limited to the examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. The configurations of each embodiment may be combined as appropriate.

For example, it is preferable that the number of peripheral blades 7 of the end mill body 1, 21 and the number of notches 8 provided in each peripheral blade 7 are appropriately set depending on cutting conditions such as the blade diameter D, blade length H, hardness of the workpiece, and cutting speed.

In each of the above-described embodiments, all of the peripheral blades 7 in the end mill body 1, 21 have a notch portion 8, but there may be peripheral blades 7 that do not have a notch portion 8.

Using the radius end mill with a blade diameter of 10 mm according to the first embodiment, a cutting test was carried out on a DMG Mori Seiki (HSK-A63) machine tool to machine a 30HRC workpiece by trochoid machining under the following cutting conditions for 120 minutes to machine a pocket shape. The cutting conditions are as follows:
(Cutting conditions)
・Cutting speed (Vc): 300m/min
・ Rotation speed (n): 9549 min-1
Feed speed (vf): 9549 mm/min
・ Feed rate per blade (fz): 0.2 mm/t
Axial depth of cut (ap): 29 mm
Radial cutting depth (ae): 1 mm
・Chip discharge amount Q: ^277cm3 /min

The end mill used is the end mill 10 of the first embodiment, which is an unequal division end mill with five blades as described above. More specifically, two notches 8 are provided on each of the three peripheral blades 7, and one notch 8 is provided on each of the remaining two peripheral blades 7. The notch 8 located closest to the axial rear end of all the notches 8 is provided on the first peripheral blade 7A, which has the smallest division angle θ1 in the axially perpendicular cross section of the rear end of the cutting blade portion 3. In addition, the circumferential positions CR of all the notches 8 do not overlap with each other. In addition, the circumferential positions CQ of all the non-cutting regions 9 do not overlap with each other.

Even when the end mill 10 of the first embodiment was used for 120 minutes under the extremely efficient cutting conditions described above, no chipping occurred on the peripheral cutting edge. In addition, the machined surface after machining was uniform and no waviness was observed, and chatter vibration was sufficiently suppressed.

1... End mill body 4... Chip discharge groove 7 (7A, 7B, 7C, 7D, 7E)... Peripheral cutting edge 8 (8Ab, 8Ba, 8Bb, 8Ca, 8Db, 8Ea, 8Eb)... Notch 9... Non-cutting area 10... End mill 11... Peripheral flank 12... Rake face CR... Circumferential position of notch 8 CS... Distance between the front ends of two circumferentially adjacent notches 8 in the rotational direction D... Blade diameter H... Blade length L2... Cutting edge length of the peripheral cutting edge continuing in the extension direction of the peripheral cutting edge P... Deepest part O... Axis T... End mill rotation direction θ... Division angle

Claims (12)

An end mill having an end mill body having a rotation axis that defines a front end and a rear end, a cutting edge portion formed on the front end side of the end mill body, a plurality of chip discharge grooves extending while twisting along the rotation axis in the cutting edge portion, and a plurality of peripheral cutting edges formed on an intersecting ridge portion on the front side in the rotation direction between the chip discharge grooves and a peripheral flank,
The cutting edge portion has a plurality of notches that make the peripheral cutting edge discontinuous,
The first notch portion, which is located at the rear end side of all the notches, is provided in the first peripheral cutting edge,
An end mill characterized in that, in a cross section perpendicular to the axis of the rear end of the cutting edge portion, the division angles of all of the peripheral cutting edges are different from each other , and the division angle of the first peripheral cutting edge is the smallest. Each of the notches has a non-cutting area on an extension line of the peripheral cutting edge, and the circumferential positions of all the non-cutting areas within the cutting edge portion do not overlap with each other.
The end mill according to claim 1 . The circumferential positions of all the notches in the cutting edge portion do not overlap with each other.
The end mill according to claim 1 or 2. At least one of the circumferential intervals between rotational front ends of the two cutout portions that are adjacent to each other in the circumferential position is different from the other circumferential interval.
The end mill according to claim 1 or 2. The axial length of the peripheral cutting edge is at least twice the cutting edge diameter.
The end mill according to claim 1 or 2. The number of the peripheral blades is five or more.
The end mill according to claim 1 or 2. The helix angle of all the peripheral cutting edges is 35° or more.
The end mill according to claim 1 or 2. The helix angles of all the peripheral cutting edges are equal to each other.
The end mill according to claim 1 or 2. The notch is arranged so that the maximum cutting edge length continuing in the extending direction of the peripheral cutting edge is 2.7 times or less of the cutting edge diameter.
The end mill according to claim 1 or 2. The notch is arranged so that the minimum cutting edge length continuing in the extending direction of the peripheral cutting edge is 0.6 times or more the cutting edge diameter.
The end mill according to claim 1 or 2. The notches are arranged such that the notch located closest to the axial position is different from the notch located closest to the circumferential position.
The end mill according to claim 1 or 2. The peripheral cutting edge is right-handed, and all of the notches are arranged such that, of two notches adjacent to each other in the axial direction, the notch located at the rear end side is located forward in the rotational direction of the notch located at the front end side.
The end mill according to claim 1 or 2.

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