End mill

Abstract

A kind of end mill, comprising: the end mill body that can rotate around axis, the chip flute that extends from the axial front end of the end mill body to the axial rear end side while being twisted around the axis, and the peripheral edge formed on the intersection ridge portion in the rotation direction front side of the chip flute and outer peripheral relief face. At least one the peripheral edge has multiple cutout portions that make the peripheral edge discontinuous. The circumferential direction positions of all the cutout portions in the end mill body do not overlap each other.

Description

TECHNICAL FIELD

[0001] The present application relates to an end mill provided with a notch portion (cutout) on an outer peripheral edge.

[0002] This application is based on patent application No. 2021-091625 filed in Japan on May 31, 2021, and the content thereof is incorporated herein by reference. BACKGROUND

[0003] Conventionally, it is known that when high-efficiency machining is performed, a structure is provided in which a notch portion (cutout) that cuts chips is provided in a part of an outer peripheral edge.

[0004] In such an end mill with a notch portion, since the length of chips can be cut short by the notch portion provided on the outer peripheral edge, it is advantageous in that the discharge property of chips becomes good.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-000696

[0006] In particular, in cases where the demand for improving machining efficiency is increasing, in cases where the cutting depth in the axial direction, the cutting speed, the feed speed, and the like are significantly large, and in cases where the proportion of the edge length with respect to the edge diameter is increased, the existing end mill with a notch portion (cutout) cannot sufficiently suppress chatter and chipping, and the end mill as a whole can be shortened in life. SUMMARY

[0007] The present application was completed in this background, and aims to provide an end mill that can perform cutting with high efficiency and stability.

[0008] An end mill of one embodiment according to the present application includes an end mill body that can rotate around an axis, a chip flute that extends from an axial front end side to an axial rear end side of the end mill body while being twisted around the axis, and an outer peripheral edge formed on a cross ridge portion of the chip flute and a rotation direction front side of an outer peripheral flank, characterized in that at least one of the outer peripheral edges has a plurality of notch portions that make the outer peripheral edge discontinuous, and the circumferential direction positions of all the notch portions in the end mill body do not overlap each other.

[0009] If a notch portion is provided on the outer peripheral edge, the length of chips can be reduced, and chipping due to the biting of chips can be suppressed. Therefore, if the number of notch portions is increased, machining with higher efficiency can be performed.

[0010] On the other hand, since the notch portion has a non-cutting region that does not come into contact with a workpiece on the extension line of the outer peripheral edge, it is a site that reduces the cutting resistance, in other words, a site that makes the cutting resistance fluctuate in cutting.

[0011] The present inventors found that the more the number of cutout portions in the end mill body increases, the more the positions of the cutout portions in the end mill body (for example, the positions of the cutout portions provided on different peripheral edges) are unintentionally aligned in the axial direction (the circumferential direction positions are repeated), and the portions where the variation in cutting resistance during cutting is locally large (the cutout portions are concentrated, and the portions where the cutting resistance is locally small) increase, promoting vibration.

[0012] In the above structure, at least one of the peripheral edges has a plurality of cutout portions, and all of the cutout portions in the end mill body are configured such that their circumferential direction positions do not overlap each other. Therefore, even if cutting is performed at a significantly high efficiency, sufficient chip breaking performance can be ensured, and chipping caused by chip biting can be suppressed. In addition, by dispersing a plurality of cutout portions in the circumferential direction, regardless of the number of cutout portions in the end mill body, the variation in cutting resistance during cutting can be suppressed to be small, and the timing at which the variation occurs can be dispersed, and the occurrence of chatter can also be suppressed.

[0013] Therefore, in the present application, by the synergistic effect of having at least one peripheral edge have a plurality of cutout portions, and all of the cutout portions in the end mill body have circumferential direction positions that do not overlap each other, chatter and chipping can be suppressed, and stable high-efficiency machining can be performed.

[0014] At least one of the intervals between the leading ends in the rotation direction of two cutout portions adjacent in the circumferential direction can also be different from the other intervals.

[0015] According to this structure, the timing at which the cutting resistance in the end mill body decreases can be made more irregular. Chatter and chipping of the peripheral edge can be suppressed, and more stable high-efficiency cutting can be performed.

[0016] In the past, the longer the axial length (edge length) of the peripheral edge, the more efficient the cutting can be performed, but chatter is easily generated. Therefore, it can also be configured such that at least one peripheral edge has a plurality of cutout portions, the edge length is twice or more the edge diameter, and all of the cutout portions in the end mill body have circumferential direction positions that do not overlap each other.

[0017] By adopting such a structure, even if cutting is performed under machining conditions where the cutting depth in the axial direction is large and the efficiency is significantly higher than in the past, the variation in cutting resistance during cutting is small, and the timing at which the variation occurs is dispersed. Therefore, chatter and chipping of the peripheral edge can be suppressed, and more stable high-efficiency machining can be performed.

[0018] It can also be a structure in which the peripheral edge is provided in five or more.

[0019] In the past, the more the number of edges increases, the more efficient the cutting can be performed, but chatter is easily generated.

[0020] On the other hand, in the present structure, at least one of the peripheral edges is configured to have a plurality of cutout portions, and five or more peripheral edges are provided, and the circumferential direction positions of all the cutout portions in the end mill body do not overlap each other. Thus, even if cutting is performed under high-efficiency machining conditions in which the feed speed is significantly high, it is difficult to cause the cutting resistance to fluctuate, and the timing at which the fluctuation occurs is dispersed. Therefore, it is possible to suppress chatter and collapse of the peripheral edges, and it is possible to perform more stable high-efficiency machining.

[0021] It can also be a structure in which the helix angle of all the peripheral edges is 35° or more.

[0022] By setting the helix angle to 35° or more, at least one of the peripheral edges has a plurality of cutout portions, and the circumferential direction positions of all the cutout portions in the end mill body do not overlap each other, so that even if cutting is performed under high-efficiency machining conditions in which the feed speed is significantly high, the cutting resistance fluctuates less during cutting, and the timing at which the fluctuation occurs is dispersed. Therefore, it is possible to perform more stable high-efficiency machining while suppressing chatter and collapse of the peripheral edges.

[0023] It can also be a structure in which the cutout portions are configured so that, among the continuous cutting edge lengths that are continuous in the extension direction of the peripheral edge, the maximum continuous cutting edge length in the end mill body is three times or less the edge diameter.

[0024] In the past, in a case where the end mill body is provided with a large number of cutout portions so that the maximum continuous cutting edge length of the peripheral edge in the end mill body is three times or less the edge diameter, chatter and collapse are likely to occur.

[0025] Therefore, by being configured so that at least one of the peripheral edges has a plurality of cutout portions, and a sufficient number of cutout portions are provided so that the maximum continuous cutting edge length in the end mill body is three times or less the edge diameter, and the circumferential direction positions of all the cutout portions in the end mill body do not overlap each other, it is possible to sufficiently suppress the cutting resistance from fluctuating during cutting, and the timing at which the fluctuation occurs is dispersed. Therefore, it is possible to perform more stable high-efficiency machining while suppressing chatter and collapse of the peripheral edges.

[0026] It can also be a structure in which the cutout portions are configured so that, among the continuous cutting edge lengths that are continuous in the extension direction of the peripheral edge, the minimum continuous cutting edge length in the end mill body is 0.6 times or more the edge diameter. It is possible to suppress the number of cutout portions from being too large, and it is possible to prevent the number of fluctuation sites of the cutting resistance from being too large. Thus, it is possible to perform more stable high-efficiency machining.

[0027] It can also be a structure in which the helix angle of all the peripheral edges is equal to each other.

[0028] According to the structure, high-efficiency cutting can be performed while suppressing collapse of the peripheral edges, with a simpler structure.

[0029] In the past, when performing high-efficiency machining, in order to suppress generation of chatter, a complex peripheral edge has been formed, such as by changing the helix angle between the peripheral edges.

[0030] In the present structure, since at least one of the peripheral edges has a plurality of notch portions, the circumferential direction positions of all the notch portions do not overlap each other, so even if the helix angles of all the peripheral edges are equal, it is difficult to cause the cutting resistance to locally increase during cutting, and the timing at which the cutting resistance increases is dispersed. Therefore, it is possible to suppress chatter and collapse of the peripheral edges, and it is possible to perform stable high-efficiency cutting.

[0031] It can also be a structure in which the notch portions are respectively configured such that the notch portion closest in the axial direction is different from the notch portion closest in the circumferential direction.

[0032] According to this structure, it is possible to moderately increase the arrangement interval of the notch portions in the circumferential direction, and it is more difficult to cause a portion in which the cutting resistance locally increases during cutting to occur, and it is difficult to cause chatter to occur. It is possible to perform more stable high-efficiency cutting.

[0033] It can also be a structure in which the peripheral edges are right-handed, and all the notch portions are configured such that, among two notch portions adjacent in the axial direction, the notch portion on the axial rear end side is located forward in the rotation direction compared to the notch portion on the axial front end side.

[0034] According to this structure, in a right-handed tool, by arranging the notch portions in the end mill body in the direction opposite to the helix direction of the peripheral edges, it is possible to arrange the notch portions in the end mill body at a higher density. As a result, it is possible to increase the number of notch portions that can be arranged in the end mill body without the circumferential direction positions of all the notch portions in the end mill body overlapping each other. Therefore, according to this structure, it is possible to perform more stable high-efficiency machining. In particular, the larger the edge length relative to the edge diameter, the more advantageous it is.

[0035] According to one embodiment of the present application, it is possible to provide an end mill that can perform high-efficiency and stable cutting. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a view showing the structure of an end mill in a first embodiment.

[0037] Figure 2 is a perspective view showing the structure of an edge portion of an end mill in the first embodiment.

[0038] Figure 3is an expanded view of the entire outer peripheral surface of the cutting edge portion of the end mill in the first embodiment.

[0039] Figure 4 is a cross-sectional view at right angles to the shaft in the axial rear end of the cutting edge portion 3 of the end mill in the first embodiment.

[0040] Figure 5 is an expanded view of the entire outer peripheral surface of the cutting edge portion of the end mill in the second embodiment.

[0041] Figure 6 is a graph showing the results of frequency analysis of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0042] Hereinafter, the structure of the end mill of each embodiment of the present application will be described using the drawings.

[0043] [First Embodiment]

[0044] Figure 1 is a view showing the structure of the end mill in the first embodiment. Figure 2 is a perspective view showing the structure of the cutting edge portion of the end mill in the first embodiment. Figure 3 is an expanded view of the entire outer peripheral surface of the cutting edge portion of the end mill main body in the first embodiment. Figure 4 is a cross-sectional view at right angles to the shaft of the end mill in the first embodiment.

[0045] Figure 1 The end mill 10 of the present embodiment shown in the figure has an end mill main body 1. The end mill main body 1 is formed of a hard material such as cemented carbide in a substantially cylindrical shape with the axis O as the center. The rear end portion (upper side portion in the figure) of the end mill main body 1 is a shank portion 2 which is left as a cylindrical shape, and the front end portion (lower side portion in the figure) is a cutting edge portion 3. Figure 1 Figure 1 The shank portion 2 of such an end mill main body 1 is held by the spindle of a machine tool, and is rotated along the axis O in the end mill rotation direction T, whereby, for example, it is fed in a direction perpendicular to the axis O to perform cutting work on a workpiece.

[0046] The shank portion 2 of such an end mill main body 1 is held by the spindle of a machine tool, and is rotated along the axis O in the end mill rotation direction T, whereby, for example, it is fed in a direction perpendicular to the axis O to perform cutting work on a workpiece.

[0047] On the outer periphery of the cutting edge portion 3, a plurality of chip flutes 4 twisted around the axis are formed on the opposite side of the end mill rotation direction T as the axial front end of the end mill main body 1 is approached toward the rear end side (shank portion 2). In the present embodiment, five chip flutes 4 are formed at intervals in the end mill rotation direction T (around the axis).

[0048] ​An outer peripheral cutting edge 7 is formed on the intersection of the rake face 12, which serves as the chip removal groove 4 facing the front of the end mill's rotation direction T, and the outer peripheral relief face 11, which serves as the outer peripheral surface of the cutting edge portion 3 adjacent to the rake face 12, on the rotation direction front side. In this embodiment, five outer peripheral cutting edges 7 are formed at predetermined intervals in the end mill's rotation direction T. At least one of the five outer peripheral cutting edges 7 has multiple slits 8 that discontinuously extend the outer peripheral cutting edge 7 in its extension direction. In this embodiment, all outer peripheral cutting edges 7 have one or more slits 8 that discontinuously extend the outer peripheral cutting edge 7 and cut off the chip in its extension direction. In this embodiment, the case where all outer peripheral cutting edges 7 have one or more slits 8 is exemplified, but in embodiments of the present invention, as long as the cutting edge portion 3 has multiple slits 8, there may also be outer peripheral cutting edges 7 without slits 8. The outer peripheral cutting edges 7 extend in a spiral shape around the axis O.

[0049] like Figure 2 As shown, a recessed center groove 5 is formed on the front end of each chip removal groove 4 along the wall surface of the chip removal groove 4 facing the front side of the end mill's rotation direction T. The end mill body 1 has five center grooves 5. On the front edge of the wall surface of these center grooves 5 facing the end mill's rotation direction T, a bottom cutting edge 6 with the wall surface as the rake face is formed in such a way that it extends from the front end of each outer peripheral cutting edge 7 toward the inner peripheral side.

[0050] like Figure 1 and Figure 2 As shown, in the end mill body 1 of this embodiment, one or more slit portions 8 are formed on each of the five outer peripheral cutting edges 7. Specifically, among the five outer peripheral cutting edges 7, two slit portions 8 are formed on three outer peripheral cutting edges 7, and one slit portion 8 is formed on the remaining two outer peripheral cutting edges 7. Each slit portion 8 is a groove that extends circumferentially from one chip removal groove 4 to another chip removal groove 4 and is recessed radially inward. The shapes of each slit portion 8 on the rake face 12 are equal to each other. For example, the slit portion 8 has a partially arc-shaped cross-section at its deepest position on the rake face 12 in the direction orthogonal to the outer peripheral cutting edge 7 (hereinafter referred to as the deepest part P).

[0051] like Figure 2 As shown, each cut portion 8 extends from one chip removal groove 4 to another adjacent chip removal groove 4 in the circumferential direction, traversing the outer circumferential rake face 11 in the circumferential direction. In other words, the front side of the cut portion 8 in the rotational direction opens on the rake face 12 of one chip removal groove 4, and the rear side of the cut portion 8 in the rotational direction opens on another chip removal groove 4. Furthermore, each cut portion 8 extends in a direction perpendicular to the axis. The cut portion 8 extends in a circumferential direction around the axis.

[0052] Although the cutout portion 8 of the present embodiment extends from one flute 4 to another flute 4 adjacent in the circumferential direction so as to cross the peripheral relief surface 11 in the circumferential direction, it can have any shape or length in the circumferential direction as long as the cutout portion 8 discontinues the peripheral edge 7. For example, the cutout portion 8 can also not reach the other flute 4. The end portion of the cutout portion 8 on the rear side in the direction of rotation T of the end mill body 1 can also be located on the peripheral relief surface 11.

[0053] Figure 3 is an expanded view of the entire peripheral surface of the cutting edge portion 3 of the end mill body 1. That is, Figure 3 the right end of Figure 3 is connected to the left end of Figure 3 the upper end of Figure 3 indicates the axial rear end of the cutting edge portion 3, Figure 3 the lower end of indicates the axial front end of the cutting edge portion 3. As illustrated, all the cutout portions 8 within the end mill body 1 are configured so that their circumferential direction positions CR do not overlap each other. This is to prevent multiple cutout portions 8 from being simultaneously opposed to the workpiece during cutting. Therefore, the circumferential direction position CR of the cutout portion 8 in the present embodiment, as viewed from the direction of extension of the axis, refers to the position of the region occupied by each cutout portion 8 when the region (from the front end to the rear end in the direction of rotation) of each cutout portion 8 within the end mill body is projected onto the same plane at right angles to the axis.

[0054] The configuration in which the "circumferential direction positions do not overlap each other" refers to a configuration in which the positions of the regions occupied by the multiple cutout portions 8 do not overlap each other, and is a configuration in which the regions are spaced apart from each other or adjacent to each other. The circumferential direction position of the cutout portion can also be expressed in terms of the angular range when an arbitrary position on the peripheral surface is set to 0° with the axis as the center. For example, it can be expressed in terms of the angular range in such a manner that the circumferential direction position of a certain cutout portion is set to 0° to 5° and the circumferential direction position of the cutout portion adjacent to the cutout portion in the circumferential direction is set to 10° to 15°.

[0055] In addition, the cutout portion 8 has a non-cutting region 9 located on the extension line of the peripheral edge 7. The non-cutting region 9 is a portion in which the peripheral edge 7 is discontinuous in the direction of extension of the peripheral edge 7. The circumferential direction positions of all the non-cutting regions 9 within the end mill body 1 also do not overlap each other. Not only the circumferential direction positions of the non-cutting regions 9 but also the circumferential direction positions of the cutout portions 8 are configured so as not to overlap each other, and thus the occurrence of chatter can be suppressed even in a significantly high-efficiency machining.

[0056] As Figure 3As shown, when five outer peripheral cutting edges 7 are arranged along the circumferential direction and facing the rear side of the end mill's rotation direction T, and designated as the first outer peripheral cutting edge 7A, the second outer peripheral cutting edge 7B, the third outer peripheral cutting edge 7C, the fourth outer peripheral cutting edge 7D, and the fifth outer peripheral cutting edge 7E, two cutting portions 8 are formed on the first outer peripheral cutting edge 7A, the second outer peripheral cutting edge 7B, and the fifth outer peripheral cutting edge 7E, and one cutting portion 8 is formed on the third outer peripheral cutting edge 7C and the fourth outer peripheral cutting edge 7D.

[0057] More specifically, a front-end side cut portion 8Aa and a rear-end side cut portion 8Ab are formed on the first peripheral blade 7A, a front-end side cut portion 8Ba and a rear-end side cut portion 8Bb are formed on the second peripheral blade 7B, a front-end side cut portion 8Ea and a rear-end side cut portion 8Eb are formed on the fifth peripheral blade 7E, a cut portion 8Ca is formed on the third peripheral blade 7C, and a cut portion 8Db is formed on the fourth peripheral blade 7D.

[0058] like Figure 3 As shown, in this embodiment, when the arrangement of all the cut portions 8Aa to 8Eb within the end mill body 1 is projected onto the same plane perpendicular to the axis, the circumferential positions CR of each cut portion 8Aa to 8Eb do not overlap. That is, the circumferential positions CR of all the cut portions 8Aa to 8Eb within the end mill body 1 are not only simply offset in the circumferential direction (e.g., the end mill rotation direction T), but also do not overlap in the circumferential direction.

[0059] Furthermore, a non-overlapping configuration means that it does not contain duplicate configurations, but rather includes both spaced and adjacent configurations. Additionally, the lengths of the circumferential positions CR of the cutouts 8Aa to 8Eb can be the same or different.

[0060] In this embodiment, the specific arrangement order of the circumferential positions CR (projected onto the same plane perpendicular to the axis) of the cut portions 8Aa to 8Eb from the cut portion 8Aa of the first outer peripheral blade 7A in the rotational direction is 8Eb, 8Ba, 8Ab, 8Ca, 8Bb, 8Ea, and 8Db. Furthermore, the circumferential positions CR of the cut portions 8Aa, 8Eb, 8Ba, 8Ab, 8Ca, 8Bb, 8Ea, and 8Db do not overlap.

[0061] In this way, by having multiple slits 8 on at least one outer peripheral cutting edge 7, chip cutting performance can be improved, and chipping caused by the chips caught in the outer peripheral cutting edge 7 can be prevented. Furthermore, by ensuring that the circumferential positions CR of all slits 8 within the end mill body 1 are different, regardless of the number of slits 8 within the end mill body 1—in other words, even with multiple slits 8—large fluctuations in cutting resistance caused by localized variations during the cutting process can be avoided. By reducing the amount of variation in cutting resistance and dispersing the timing of these fluctuations, chatter can be minimized.

[0062] Therefore, in this embodiment, by achieving the synergistic effect of having multiple slits 8 on at least one peripheral cutting edge 7 and ensuring that the circumferential positions of all slits 8 within the end mill body 1 do not overlap, even in extremely high-efficiency machining, not only can the chipping of the peripheral cutting edge 7 be suppressed, but also more stable and efficient machining with suppressed chatter can be performed. Examples of extremely high-efficiency machining include cutting conditions where the axial depth of cut (ap) is more than twice the cutting diameter D, or cutting speed (Vc) is more than 250 m / min, or chip removal rate (Q) is 250 cm³ when the cutting diameter is 10 mm. 3 Cutting conditions with a speed of 0.5 min or higher, or cutting conditions that combine two or more of these three conditions.

[0063] like Figure 3 As shown, at least one of the intervals CS between the front ends of two adjacent cut portions 8 (e.g., 8Aa and 8Eb) at a circumferential position CR differs from the other intervals CS. This mitigates the periodicity of the decreasing cutting resistance. As a result, even in extremely high-efficiency machining, stable, high-efficiency machining is possible, suppressing chatter and chipping.

[0064] Figure 1 The diameter (D: cutting edge diameter) of the cutting edge 3 of the end mill body 1 shown in this embodiment is approximately 10 mm, and the cutting edge length H is approximately 30 mm (3D). The greater the axial length H of the outer peripheral cutting edge 7 (the length when the outer peripheral cutting edge 7 is projected onto a straight line parallel to the axis), the greater the axial depth of cut can be, enabling more efficient cutting. On the other hand, the longer the axial length H (cutting edge length) of the outer peripheral cutting edge 7, the higher the machining efficiency, but the more prone it is to chatter. In particular, the larger the ratio (H / D) of the cutting edge length H to the cutting edge diameter D, for example, more than twice (H / D≥2), and especially more than three times (H / D≥3), the more often a kerf 8 is provided on the outer peripheral cutting edge 7 to shorten the chip length.

[0065] In the present embodiment, the at least one peripheral edge 7 is configured to have a plurality of cutout portions 8, the edge length H is twice or more the edge diameter D, and the circumferential direction positions CR of all the cutout portions 8 within the end mill body 1 do not overlap each other. With this configuration, more efficient cutting can be performed, and even if the edge length H is elongated, it is difficult to cause the peripheral edge 7 to bite into the chips. Furthermore, since the variation in cutting resistance during cutting is small, and the timing of the variation is dispersed, it is also difficult to cause chatter. Therefore, by the synergistic effect of these, stable machining can be performed with higher efficiency.

[0066] In the present embodiment, five peripheral edges 7 are provided, but the number of peripheral edges 7 is not limited to five, and six or more can be provided. In this way, by providing the number of peripheral edges 7 to be five or more, the feed speed can be increased, and more efficient cutting can be performed. On the other hand, since the feed speed is increased, it is easy to cause the chips to bite, and therefore, if the number of cutout portions is increased, it is easy to cause chatter.

[0067] In the present embodiment, by configuring all the cutout portions 8 within the end mill body 1 so that the circumferential direction positions CR do not overlap each other, even if the number of edges and the number of cutout portions are increased, since the variation in cutting resistance during cutting is small, and the timing of causing the variation is dispersed, it is also difficult to cause chatter. As a result, by the synergistic effect of this, more stable and efficient machining can be performed.

[0068] In the present embodiment, the helix angle of all the peripheral edges 7 is 40°. In the present embodiment, all the helix angles are set to 40°, but if all the helix angles are 35° or more, the helix angles can also be different between the peripheral edges 7.

[0069] In the present embodiment, by configuring the cutout portions 8 so that the circumferential direction positions of all the cutout portions 8 within the end mill body 1 do not overlap each other, even if the helix angle is increased, since the variation in cutting resistance during cutting is small, and the timing of causing the variation is dispersed, it is also difficult to cause chatter. As a result, by the synergistic effect of this, more stable and efficient machining can be performed.

[0070] In addition, as Figure 3As shown, within the outer peripheral cutting edge 7, the continuous cutting edge length L2 of the portion that is not cut by the slit portion 8 but continues in the extending direction of the outer peripheral cutting edge 7 is equivalent to the chip length. In other words, the continuous cutting edge length L2 is the length from the front end of the outer peripheral cutting edge 7 to the slit portion 8 located at the foremost side in the extending direction of the outer peripheral cutting edge, or the length between adjacent slit portions 8 within the same outer peripheral cutting edge, or the length from the rear end of the outer peripheral cutting edge 7 to the slit portion 8 located at the rearmost end side in the extending direction of the outer peripheral cutting edge. The chip length during cutting can be varied depending on the number and spacing of the slit portions 8 provided on each outer peripheral cutting edge 7. For example, chips cut in the front end portion of the first outer peripheral cutting edge 7A are cut in the front end side slit portion 8Aa, and chips cut in the central portion between the front end side slit portion 8Aa and the rear end side slit portion 8Ab are cut in the rear end side slit portion 8Ab.

[0071] In this embodiment, among the continuous cutting edge lengths L2 of the outer peripheral cutting edge 7 that are continuous in the extending direction of the outer peripheral cutting edge 7 without being cut by the slit portion 8, the longest continuous cutting edge length L2 within the end mill body 1 is... MAX (i.e., maximum chip length) such as Figure 3 As shown by the thick line, the distance from the slit portion 8Ca provided on the third outer peripheral cutting edge 7C to the rear end of the third outer peripheral cutting edge 7C is 24.8 mm (2.5D). Furthermore, among the continuous cutting edge lengths L2 of the outer peripheral cutting edges 7 that are not cut by the slit portion 8 and continue in the extending direction of the outer peripheral cutting edge 7, the smallest continuous cutting edge length L2 within the end mill body 1 is... MIN like Figure 3 As shown by the thick line, the distance from the front end of the fifth outer peripheral blade 7E to the front side cut 8Ea is 9.1 mm (0.9D).

[0072] Thus, with the maximum continuous cutting edge length L2 MAX The kerf 8 is arranged in a manner that is less than three times (3D or less) the cutting diameter D of the end mill body 1. This ensures that the circumferential arrangement of all kerf 8 within the end mill body does not overlap, and eliminates cutting edge portions that would result in excessively long chip lengths. This provides the advantage of minimizing chip ingress during cutting and suppressing chipping of the outer peripheral cutting edge 7. On the other hand, conventionally, if a large number of kerf 8 are provided within the end mill body 1, the maximum continuous cutting edge length L2 within the end mill becomes excessive. MAX If the diameter is less than three times the cutting diameter D, the cut portions 8 are easily aligned axially (circumferentially repeated) with each other (for example, between cut portions 8 located on different outer peripheral cutting edges 7). During the cutting process, there are areas where the variation in cutting resistance is relatively large (areas where the cut portions are concentrated), which may cause chatter.

[0073] In the present embodiment, the cutout portions 8 are arranged in such a manner that the circumferential direction positions CR of all the cutout portions 8 do not overlap each other, and the maximum continuous cutting edge length L2 MAX within the end mill body is 0.6 times or more the length of the blade diameter D, and the minimum continuous cutting edge length L2

[0074] In addition, by arranging the cutout portions 8 in such a manner that the minimum continuous cutting edge length L2 MIN within the end mill body is 0.6 times or more the length of the blade diameter D, the number of the cutout portions 8 can be suppressed from being excessive, and the variation in cutting resistance can be prevented from being excessive.

[0075] Therefore, by arranging the cutout portions 8 in such a manner that the circumferential direction positions CR of all the cutout portions 8 do not overlap each other, and the maximum continuous cutting edge length L2 MIN within the end mill body is 0.6 times or more the length of the blade diameter D, more stable and efficient machining can be performed.

[0076] Further, by arranging the cutout portions 8 in such a manner that the maximum continuous cutting edge length L2 MAX is 3 times or less the length of the blade diameter, and the minimum continuous cutting edge length L2 MIN is 0.6 times or more the length of the blade diameter, the continuous cutting edge length L2 within the end mill body can be in an appropriate deviation state, and thus the chatter can be further suppressed.

[0077] Therefore, by arranging the cutout portions 8 in such a manner that the circumferential direction positions CR of all the cutout portions 8 do not overlap each other, and the maximum continuous cutting edge length L2 MAX is 3 times or less the length of the blade diameter D, and the minimum continuous cutting edge length L2 MIN is 0.6 times or more the length of the blade diameter, more stable and efficient machining can be performed.

[0078] On the rake face 12 among the cutout portions 8, the deepest portion in the direction orthogonal to the extension direction of the peripheral edge 7 is named as the deepest portion P. As Figure 3 shown, the axial intervals Ll between the deepest portions P of the two cutout portions 8 adjacent (closest) in the axial direction within the end mill body 1 are arranged at equal intervals. In the present embodiment, the axial intervals Ll between the six deepest portions P adjacent in the axial direction within the end mill body 1 are 1.5 mm. By equalizing the arrangement intervals (distances) of the cutout portions 8 adjacent in the axial direction within the end mill body 1, the variation in cutting load between the peripheral edges 7 can be prevented from occurring when the end mill body 1 is rotated for cutting.

[0079] In the present embodiment, all the peripheral edges 7 extend from the front end to the rear end side of the end mill body 1 at a prescribed helix angle, and the helix angles of all the peripheral edges 7 are equal to each other.

[0080] In the past, in order to suppress the occurrence of chatter, a complex structure in which the helix angles are made different between the peripheral edges 7 is known. In the present embodiment, at least one peripheral edge 7 has a plurality of notch portions 8, and the circumferential direction positions of all the notch portions 8 do not overlap each other. Therefore, in the present embodiment, even if the helix angles of all the peripheral edges 7 are made equal, it is difficult to cause the chip to bite. Also, in the present embodiment, since the variation in cutting resistance during cutting is small, and the timing at which the variation occurs is dispersed, it is difficult to generate chatter. Therefore, according to the present embodiment, it is possible to perform cutting with high efficiency while suppressing the chipping of the peripheral edges 7 with a simpler structure.

[0081] As shown in Figure 3 , all the notch portions 8 are configured such that the notch portion 8 closest in the axial direction and the notch portion 8 closest in the circumferential direction are different notch portions 8 for each notch portion 8. For example, for the notch portion 8Ba, the notch portions closest in the axial direction are 8Aa and 8Ca, and the notch portions closest in the circumferential direction are 8Eb and 8Ab, which are different notch portions. According to this structure, it is possible to moderately spread the arrangement intervals of the notch portions 8 in the circumferential direction, and it is difficult for a portion in which the variation in cutting resistance during cutting is locally large to occur, and it is difficult to cause chatter.

[0082] Preferably, the notch portion 8 located at the most forward end side in the axial direction within the end mill body 1 (the notch portion 8 provided on the fifth peripheral edge 7E in Figure 3 ) is formed at a position separated by a certain distance from the front end edge of the end mill body 1 to the inside in the axial direction. As a reason for this, it can be cited that even if the notch portion 8 is provided at a position close to the front end edge of the end mill body 1, only the short chips at the start of cutting can be cut, and the effect of shortening the long chips becomes small. Also, preferably, the notch portion 8 located at the most rear end side in the axial direction is formed at a position separated by a certain distance from the rear end edge of the end mill body 1 to the inside in the axial direction.

[0083] Therefore, by forming the plurality of notch portions 8 formed on each peripheral edge 7 in the vicinity of the more central portion of the cutting edge portion 3, it is possible to efficiently shorten the chips with fewer notch portions 8.

[0084] The end mill body 1 of the present embodiment is a non-uniform end mill in which all the circumferential direction intervals between the peripheral edges 7 adjacent in the circumferential direction (end mill rotation direction T) in a cross section orthogonal to the shaft are different from each other. That is, as shown in Figure 4 , in a cross-sectional view orthogonal to the axis O, the five peripheral edges 7 are not arranged in equal division around the shaft, but are arranged at different division angles. In this way, by making the circumferential direction intervals between the peripheral edges 7 in the cross section orthogonal to the shaft different, it is possible to further suppress chatter.

[0085] In the present embodiment, asFigure 4 As shown, in a cross-section perpendicular to the axis, among the angles (dividing angles θ) formed by the straight line connecting a certain outer peripheral cutting edge 7 to the axis O and the straight line connecting the outer peripheral cutting edge 7 adjacent to that outer peripheral cutting edge 7 in the circumferential direction to the axis O, θ1 is the smallest, and increases in the order θ1 < θ2 < θ3 < θ4 < θ5. That is, in a plane perpendicular to the axis, the interval between the first outer peripheral cutting edge 7A and the second outer peripheral cutting edge 7B, which is located on the opposite side of the end mill's rotation direction T, is the smallest. Furthermore, in a cross-section perpendicular to the axis, the interval between the first outer peripheral cutting edge 7A and the fifth outer peripheral cutting edge 7E, which is located in front of the first outer peripheral cutting edge 7A in the end mill's rotation direction T, is the largest.

[0086] In this embodiment, although the circumferential spacing, i.e. the dividing angle θ (θ1 to θ5), of the five outer peripheral blades 7 are all different, some of them may have the same dividing angle θ.

[0087] like Figure 3 , Figure 4 As shown, in this embodiment, among the cut portions 8 within the end mill body 1, the cut portion 8Bb located axially at the rearmost end is positioned on the outer peripheral cutting edge 7B, which has the smallest circumferential spacing (splitting angle) among the five outer peripheral cutting edges 7, in a plane perpendicular to the axis at the rearmost end of the cutting edge 3, up to the adjacent outer peripheral cutting edge 7 in the direction of rotation. In other words, by positioning the cut portion 8Bb located axially at the rearmost end among the cut portions 8 within the end mill body 1 on the outer peripheral cutting edge 7B, which has the smallest workload, chipping near the rear end of the outer peripheral cutting edge can be effectively suppressed.

[0088] Since the slit portion 8 is a discontinuous part on the outer peripheral cutting edge 7, stress tends to concentrate there, making it prone to chipping. Moreover, stress is difficult to release near the grip portion (i.e., the handle portion 2). Therefore, by placing the slit portion 8, located on the rearmost side in the axial direction, on the outer peripheral cutting edge 7 where the workload is minimal (small cutting angle), stress concentration can be mitigated, further suppressing chipping of the outer peripheral cutting edge 7.

[0089] [Second Implementation]

[0090] Next, the structure of the end mill in the second embodiment will be described. Figure 5 This is a fully developed view of the outer peripheral surface of the cutting edge portion 3 of the end mill body 21 according to the second embodiment. In the second embodiment, similarly to the first embodiment, the circumferential positions CR of all the cut portions 8 within the end mill body 21 are... Figure 3 The edges do not overlap. Furthermore, the helix angle and the spacing (dividing angle) between the outer peripheral cutting edges 7 are equal to those in the first embodiment. The cutting diameter D of the end mill body 21 in this embodiment is... Figure 1 The blade is approximately 20mm long and the blade length H is approximately 60mm long.

[0091] The difference from the first embodiment is that two cutout portions 8 are provided on the first peripheral edge 7A, the fourth peripheral edge 7D, and the fifth peripheral edge 7E, and three cutout portions 8 are provided on the second peripheral edge 7B and the third peripheral edge 7C. In addition, the maximum continuous cutting edge length L2 MAX is 1.5D, and the minimum continuous cutting edge length L2 MIN is 0.8D.

[0092] In the above-described first embodiment, as shown in Figure 3 , all the cutout portions 8 in the end mill body 1 are configured such that, among the two cutout portions 8 that are axially adjacent, the cutout portion 8 on the rear end side is positioned in the circumferential direction on the rear side in the rotation direction (right-up configuration) compared to the cutout portion 8 on the front end side. In contrast, in the present embodiment, as shown in Figure 5 , all the cutout portions 8 in the end mill body 21 are configured such that, among the two cutout portions 8 that are axially adjacent, the cutout portion 8 on the rear end side is positioned in the circumferential direction on the front side in the rotation direction (right-down configuration) compared to the cutout portion 8 on the front end side. That is, as shown by the arrow F in Figure 5 , all the cutout portions 8 are configured in the direction opposite to the direction of inclination of the peripheral edge 7 (right-down). In this way, by arranging the cutout portions 8 in the direction opposite to the helical direction of the peripheral edge, the circumferential direction (end mill rotation direction T) interval of the cutout portions 8 that are adjacent in the circumferential direction can be further reduced, and thus the cutout portions 8 can be arranged at a higher density, and more cutout portions 8 can be arranged.

[0093] In particular, when the edge diameter D Figure 1 of the end mill body 21 is large, in order to form the required number of cutout portions 8, it is preferable to arrange all the cutout portions 8 in the end mill body in the direction opposite to the helical direction of the peripheral edge (as shown in the right-down configuration in the case where the peripheral edge is right-handed as shown in Figure 5 . In particular, in the case where the edge diameter D is 12 mm or more, it is preferable to arrange all the cutout portions 8 in the direction opposite to the helical direction of the peripheral edge. Furthermore, the larger the proportion of the edge length H with respect to the edge diameter D, the larger the number of cutout portions 8 required in order to ensure sufficient chip breaking performance, and thus it is preferable to arrange all the cutout portions 8 in the direction opposite to the helical direction of the peripheral edge. By arranging the cutout portions 8 in this way, it is possible to arrange more cutout portions 8 while the circumferential direction positions of the cutout portions 8 in the end mill rotation direction T do not overlap with the circumferential direction positions of other cutout portions 8 throughout the entire axial direction (edge length) of the cutting edge portion 3. As a result, it is possible to perform more efficient cutting while suppressing the collapse of the peripheral edge 7.

[0094] Because the cutting edge 8 is a discontinuous part on the outer peripheral blade 7, stress tends to concentrate, which can easily cause chipping. Moreover, the closer to the grip (i.e., the handle 2), the more difficult it is to release stress.

[0095] In this embodiment, such as Figure 5 As shown, on the outer peripheral cutting edge 7B with the smallest circumferential spacing (division angle) up to the adjacent outer peripheral cutting edge 7 in the direction of rotation, a cutting edge 8 located on the axial rearmost end side is provided among all the cutting edges 8 in the end mill body 21. In this way, by arranging the cutting edge 8 located on the axial rearmost end side among all the cutting edges 8 in the end mill body 21 on the outer peripheral cutting edge 7B with the least cutting amount, chipping of the outer peripheral cutting edge 7 on the axial rear end side can be suppressed.

[0096] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it is self-evident that the present invention is not limited to these examples. Those skilled in the art will obviously be able to conceive of various modifications or alterations within the scope of the technical concept described in the claims, and understand that these modifications or alterations also fall within the technical scope of the present invention. The structures of the various embodiments can also be appropriately combined.

[0097] For example, the number of peripheral cutting edges 7 on the end mill body 1 and 21 and the number of cutting edges 8 provided on each peripheral cutting edge 7 are preferably set appropriately according to cutting conditions such as cutting diameter D, cutting length H, workpiece hardness and cutting speed.

[0098] In the above embodiments, all peripheral cutting edges 7 of the end mill body 1 and 21 have a cutting portion 8, but there may also be peripheral cutting edges 7 that do not have a cutting portion 8.

[0099] Example

[0100] For the 10mm diameter arc-head end mills of Embodiment 1 (first embodiment), Comparative Example 1, and Comparative Example 2 of the present invention, each was held by the spindle of a machine tool and rotated in the direction of rotation T around axis O of the end mill under the following cutting conditions. A workpiece with a cutting radius of 30 HRC was then machined for 120 minutes using a (HSK-A63) machine tool manufactured by DMG Mori Seiki Co., Ltd., via cycloidal machining. Then, the vibration frequency during cutting was analyzed to verify the presence or absence of chatter and chipping of the outer peripheral cutting edge.

[0101] (Cutting conditions)

[0102] • Cutting speed (Vc): 300 m / min

[0103] Rotational speed (n): 9549 min -1

[0104] • Feed rate (vf): 9549 mm / min

[0105] • Single blade feed (fz): 0.2 mm / t

[0106] • Axial cutting depth (ap): 29 mm

[0107] • Radial cutting depth (ae): 1 mm

[0108] • Chip volume (Q): 277 cm 3 / min

[0109] The end mill of Example 1 is an end mill of the first embodiment, and is a five-blade unequal division end mill as described above, in which two cutout portions 8 are provided on each of three outer peripheral blades 7, and one cutout portion 8 is provided on each of the remaining two outer peripheral blades 7. In addition, the circumferential direction positions CR of all the cutout portions 8 in the end mill body 1 do not overlap each other. Comparative Example 1 is also a five-blade unequal division end mill, and the division angles are the same as those of the first embodiment. However, in Comparative Example 1, all the outer peripheral blades 7 have two cutout portions 8, and the circumferential direction positions CR of the plurality of cutout portions 8 overlap each other as shown in the schematic view. Figure 6

[0110] From experiments conducted in the past, the higher the machining sound during machining, and in addition, the greater the waviness visually observed on the machined surface, the greater the non-periodic vibration intensity is exhibited in the frequency range of 4000 to 5000 Hz. In addition, even in the case where the difference between the machining sound and the state of the machined surface visually is small, the slight chatter is exhibited as non-periodic vibration intensity, and therefore, in order to evaluate the machining stability in high-efficiency machining, frequency analysis is used to evaluate the chatter.

[0111] Figure 6 is a graph showing the results of frequency analysis of Example 1 and Comparative Example 1. In the horizontal axis of Figure 6 , the vibration frequency (rotation frequency) of the end mill body 1 generated when machining a workpiece is shown, and in the vertical axis, the intensity is shown. In addition, Figure 6 , the expanded view of Example 1 corresponds to the expanded view of the cutting edge portion 3 of the above-described first embodiment Figure 3 , and is a view schematically showing the expanded view of Figure 3 . In Figure 6 , the portions indicated by black dots indicate the cutout portions 8, and Example 1 indicates that the circumferential direction positions of all the cutout portions 8 in the end mill do not overlap each other, and Comparative Example 1 indicates that the circumferential direction positions of the plurality of cutout portions 8 overlap each other.

[0112] As shown in Figure 6 ​In the first embodiment shown in which one or two cutout portions 8 are formed on the peripheral edge and are arranged so that the circumferential direction positions CR of all the cutout portions 8 do not overlap, the intensity of the vibration was hardly confirmed in the frequency range of about 4000 to 5000 Hz. On the other hand, in Comparative Example 1 in which two cutout portions 8 are provided on each of the peripheral edges and the circumferential direction positions of the plurality of cutout portions 8 coincide, vibration of a certain degree of intensity without periodicity was generated in the frequency range of about 4000 to 5000 Hz. In addition, in Comparative Example 2, although the intensity was smaller than that of Comparative Example 1, vibration was confirmed.

[0113] In addition, in Embodiment 1 and Comparative Example 1, even if high-efficiency machining in which the axial cutting depth is large and the cutting speed is large as described above is performed for 120 minutes, the peripheral edge does not generate a chipped edge, but Comparative Example 2 generates a chipped edge on the peripheral edge after 30 minutes from the start of cutting.

[0114] From the above, it is understood that Embodiment 1 can stably perform cutting for a long time even if extremely high-efficiency flank cutting is performed.

[0115] Explanation of Reference Numerals

[0116] 1 …… end mill body

[0117] 4 …… chip flute

[0118] 7 (7A, 7B, 7C, 7D, 7E) …… peripheral edge

[0119] 8 (8Ab, 8Ba, 8Bb, 8Ca, 8Db, 8Ea, 8Eb) …… cutout portion

[0120] 9 …… non-cutting region

[0121] 10 …… end mill

[0122] 11 …… peripheral relief surface

[0123] 12 …… rake surface

[0124] CR …… circumferential direction position of cutout portion 8

[0125] CS …… interval between the rotation direction leading ends of two cutout portions 8 adjacent in the circumferential direction

[0126] D …… edge diameter

[0127] H …… edge length

[0128] L1 …… axial interval between the deepest portions on the rake surfaces adjacent in the axial direction

[0129] L2 …… continuous cutting edge length of the peripheral edges continuous in the extension direction of the peripheral edges

[0130] P …… deepest part

[0131] O …… axis

[0132] T …… direction of rotation of end mill

[0133] θ …… division angle.

Claims

1. An end mill, comprising: A rotatable end mill body, a chip evacuation groove extending from the axial front end to the axial rear end of the end mill body while twisting about the axis, and an outer peripheral cutting edge formed on the intersection of the chip evacuation groove and the outer peripheral flank face in the direction of rotation, characterized in that: At least one of the peripheral cutting edges has a plurality of slits that make the peripheral cutting edge discontinuous. The cut portion has a non-cutting area located on the extension line of the outer peripheral cutting edge. When viewed from the extension direction of the axis, the circumferential positions of all the cut portions within the end mill body, from their respective front to rear ends in the direction of rotation, do not overlap.

2. The end mill according to claim 1, characterized in that, At least one of the intervals between the front ends of two adjacent cut portions in the circumferential direction is different from the other intervals.

3. The end mill according to claim 1 or 2, characterized in that, The blade length is more than twice the blade diameter.

4. The end mill according to claim 1 or 2, characterized in that, The peripheral blades are set to five or more.

5. The end mill according to claim 1 or 2, characterized in that, The helix angle of all the aforementioned peripheral cutting edges is 35° or greater.

6. The end mill according to claim 1 or 2, characterized in that, The cut portion is configured such that, among the continuous cutting edge lengths in the extension direction of the outer peripheral cutting edge, the maximum continuous cutting edge length within the end mill body is less than three times the tool diameter.

7. The end mill according to claim 1 or 2, characterized in that, The cut portion is configured such that, among the continuous cutting edge lengths in the extension direction of the outer peripheral cutting edge, the minimum continuous cutting edge length within the end mill body is more than 0.6 times the cutting edge diameter.

8. The end mill according to claim 1 or 2, characterized in that, The helix angles of all the described peripheral cutting edges are equal to each other.

9. The end mill according to claim 1 or 2, characterized in that, The cut portions are configured such that the cut portion closest in the axial direction is different from the cut portion closest in the circumferential direction.

10. The end mill according to claim 1 or 2, characterized in that, The outer peripheral blade is a right-hand helix, and all the cut portions are configured such that, among two axially adjacent cut portions, the cut portion located on the rear end side is located in front of the cut portion located on the front end side in the direction of rotation.

Images