JP2014083642A - Ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball end mill capable of obtaining sufficiently-excellent cut surface roughness after cutting.SOLUTION: At least one slit 18 is formed on a partial spherical part 16a radially from the tip, and the edge 18a of the slit 18 functions as a ball blade in a cutting work, and therefor basically, by applying the specification of contact of the entire part of the partial spherical part 16a, a cutting work emphasizing finishing can be achieved, and even when an uncut portion still remains, not only finish cutting but also processing similar to grinding can be performed by the slit 18 functioning as a cutting blade. Namely, a ball end mill 10 capable of obtaining sufficiently-excellent cut surface roughness after cutting can be provided.

Description

  The present invention relates to a ball end mill, and more particularly, to an improvement for making the surface roughness after cutting by the ball end mill sufficiently satisfactory.

  2. Description of the Related Art A ball end mill is known in which a partial spherical portion is provided at the tip of a tool body and cutting is performed by a ball blade formed in the partial spherical portion. For example, it is a spherical blade end mill described in Patent Document 1. Such a ball end mill is used, for example, by being attached to a well-known machining center to enable cutting of a three-dimensional free-form surface. Widely used for cutting materials.

Japanese Patent Laid-Open No. 11-156622

  By the way, in the machining of the mold using the ball end mill, the machined surface after cutting is usually polished. In particular, since a mirror surface is required for a mold for a design surface or the like, the necessity for such a polishing process is high. However, in the conventional technique, the cost required for the polishing process has been a problem. In other words, since sufficient cutting surface roughness cannot be obtained by cutting with a conventional ball end mill, it is necessary to perform finish polishing manually, but this has the adverse effect of requiring human or time costs for the polishing technique and processing time. was there. In order to eliminate such an adverse effect, it is conceivable to perform the same processing using a diamond or a CBN tool, but this causes a new adverse effect that the tool cost is increased. For this reason, there has been a demand for the development of a ball end mill that has a sufficiently good surface roughness after cutting, but such a ball end mill has not been developed yet.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a ball end mill that has a sufficiently good surface roughness after cutting.

  In order to achieve such an object, the gist of the first invention is a ball end mill in which a partial spherical portion is provided at the tip of a tool body and cutting is performed by a ball blade formed in the partial spherical portion. Then, at least one slit is formed radially from the tip of the partial spherical portion, and the edge of the slit functions as the ball blade.

  Thus, according to the first aspect of the present invention, there is provided a ball end mill in which a partial spherical portion is provided at the tip of the tool body, and the cutting is performed by the ball blade formed in the partial spherical portion, Since one slit is formed radially from the tip, and the edge of the slit functions as the ball blade, the cutting process with an emphasis on finishing is basically performed by using the partial round portion specification. This can be realized, and even when uncut portions are generated, the slit functioning as a cutting edge can be used to perform finish cutting and thus processing close to grinding. That is, it is possible to provide a ball end mill that makes the surface roughness after cutting sufficiently satisfactory.

  The gist of the second invention subordinate to the first invention is that the rake angle of the edge of the slit is a cross-sectional shape having a central angle of 45 ° of the partial spherical portion with respect to the axial center of the partial spherical portion. It is in the range of 5 ° or more and 15 ° or less. In this way, necessary and sufficient cutting performance can be imparted to the edge of the slit, and the slit can be used to perform finish cutting and thus close to grinding.

  The gist of the third invention subordinate to the first to second inventions is that the tool diameter is set to D in a cross-sectional shape having a central angle of 45 ° with respect to the axial center of the partial spherical portion. As for the width dimension of the said slit, it exists in the range of 0.05D or more and 0.15D or less. If it does in this way, in addition to being able to provide necessary and sufficient cutting performance to the edge of the slit, cutting which attaches importance to finishing can be realized by the surplus partial spherical part.

It is the front view which looked at the ball end mill which is a suitable example of the present invention from the direction perpendicular to an axis. It is a front view explaining in detail the structure of the blade part with which the ball end mill shown in FIG. 1 was equipped. It is a photograph explaining in detail the configuration of the slit formed in the blade portion shown in FIG. FIG. 4 is a partial cross-sectional view showing the blade portion shown in FIG. 2 cut along a dashed line IV. It is a figure explaining the test which the present inventors etc. performed in order to verify the effect of the present invention, and shows the roughness curve of the pick feed direction of the cut surface after cutting by the conventional product. It is a figure explaining the test which the present inventors performed in order to verify the effect of the present invention, and shows the roughness curve of the feed direction of the work surface after cutting by the conventional product. It is a figure explaining the test which the present inventors etc. performed in order to verify the effect of the present invention, and shows the roughness curve of the pick feed direction of the work surface after cutting by the ball end mill of this example. It is a figure explaining the test which the present inventors etc. performed in order to verify the effect of the present invention, and shows the roughness curve of the feed direction of the cut surface after cutting by the ball end mill of this example.

  The ball end mill of the present invention is preferably used for cutting for processing a three-dimensional curved surface including a processing surface and a cavity of a mold. Preferably, it is suitable for machining a die by a contouring method in which cutting is performed along a curved surface to be processed, or a contouring method in which cutting is performed while gradually changing the height of a portion to be processed. Although it is used, it is widely used for various other work materials.

  As the material for the ball end mill of the present invention, cemented carbide or high-speed tool steel is preferably used, but other materials may be used. It is desirable to coat the surface of the blade portion or the like with a hard coating such as TiAlN, TiN, or TiCN as necessary.

  The ball end mill of the present invention is preferably a three-blade ball end mill in which three slits are radially formed in the partial spherical portion, but one or two slits are formed in the partial spherical portion. The present invention is also suitably applied to a multi-blade ball end mill in which four or more slits are formed.

  The slit provided in the ball end mill of the present invention is preferably formed without being twisted from the axial end of the partial spherical portion toward the outer peripheral side, in other words, the axial center of the partial spherical portion. Is formed in a spiral shape that is twisted in the direction opposite to the cutting direction as it goes from the end on the axial center side toward the outer peripheral side, in other words, away from the tip of the tool. It may be.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings used for the following description, the dimensional ratios and the like of each part are not necessarily drawn accurately.

  FIG. 1 is a front view of a ball end mill 10 according to a preferred embodiment of the present invention as viewed from a direction perpendicular to the axis. As shown in FIG. 1, the ball end mill 10 of the present embodiment includes a cylindrical shank portion 12, a neck portion 14, and a blade portion 16 that is provided at the tip of a tool body and that is involved in cutting work. In preparation. The ball end mill 10 is preferably such that the shank portion 12, the neck portion 14 and the blade portion 16 are integrally formed by polishing a material such as cemented carbide or high-speed tool steel.

  FIG. 2 is a front view for explaining in detail the configuration of the blade portion 16 provided in the ball end mill 10. As shown in FIG. 2, the blade portion 16 provided in the ball end mill 10 includes a partial spherical portion 16a corresponding to a spherical surface having a specified diameter at least partially, and a shank side of the partial spherical portion 16a. For example, the outer peripheral part 16b which comprises the cylindrical shape of the same diameter as the partial spherical part 16a is provided. Preferably, an outer peripheral portion 16b corresponding to a cylinder having a diameter equal to that of the partial spherical portion 16a is integrally provided on the shank side of the partial spherical portion 16a corresponding to a hemisphere having a predetermined diameter. Preferably, the surface of the blade portion 16 is coated with a hard coating such as TiAlN, TiN, or TiCN as necessary.

  FIG. 3 is a photograph for explaining in detail the configuration of the slit 18 formed in the blade portion 16, and FIG. 4 shows the central angle (corresponding to the axial center C of the partial spherical portion 16a). 2 is a diagram illustrating a cross-sectional shape (R45 ° cross-section) of 45 °, that is, the center angle when the center of the spherical surface is O and the axis C is one radius, that is, the blade portion 16 shown in FIG. It is a fragmentary sectional view cut and shown. As shown in FIGS. 2 to 4, at least one slit 18 is formed radially from the tip of the partial spherical portion 16 a in the ball end mill 10 of the present embodiment. Preferably, as shown in FIGS. 2 and 3, three slits 18 are radially formed in the partial spherical portion 16a at equal angular intervals (120 ° intervals when viewed from the top of the partial spherical portion 16a). However, it may be one in which one or two slits are formed in the partial spherical portion 16a, or one in which four or more slits are formed. Even in such a configuration, it is desirable that the slits 18 are formed at equal angular intervals when viewed from the top of the partial spherical portion 16a. As shown in FIG. 2, the slit 18 is preferably formed without being twisted from the end portion on the side of the axis C of the partial spherical portion 16a toward the outer peripheral portion 16b. It is formed along a plane including the axis C of the spherical portion 16a, but as it goes from the end on the axis C side toward the outer periphery, in other words, away from the tool tip, the direction opposite to the cutting direction It may be formed in a spiral shape. In the photograph of FIG. 3, the slit 18 is not provided to extend to the tool tip (the top of the spherical surface corresponding to the partial spherical portion 16a), but at least one slit 18 is provided to extend to the tool tip. It may be.

  As shown in FIG. 4, the slit 18 is preferably configured to have an arc shape in a cross-sectional shape including the center O of the partial spherical portion 16a. Preferably, the edge 18a of the slit 18, that is, the boundary (edge) between the slit 18 and the surface of the partial spherical portion 16a has a hook shape, and the rake angle θ of the edge 16a is positive. It is a value. The slit 18 preferably has a rake angle θ of 5 ° or more of the edge 18a in a cross-sectional shape with a central angle φ = 45 ° of the partial spherical portion 16a with respect to the axis C of the partial spherical portion 16a. It was formed to be within the range of °° or less. The slit 18 preferably has a width dimension w, that is, a width (perpendicular to the longitudinal direction of the partial spherical portion 16a) in the width dimension w, that is, the boundary portion with the partial spherical portion 16a in the cross-sectional shape of the central angle φ = 45 °. The length dimension in the direction) is formed such that the tool diameter is D and is in the range of 0.05D to 0.15D. The slit 18 preferably has a depth dimension d, that is, a radial depth (depth dimension in the normal direction) with respect to the surface of the partial spherical portion 16a of about 0 to 0.2D (tool tip). In the vicinity, the slit 18 is not formed and the depth may be 0), and the depth is about 0.2D. The slit 18 only needs to be provided at least in the partial spherical portion 16a (the portion corresponding to the spherical surface corresponding to the center O), and does not necessarily extend to the outer peripheral portion 16b. Good.

  As specific dimensions of the ball end mill 10 of the present embodiment, the shank portion 12 has a cylindrical shape with a diameter of about 6 mmφ and a length of about 40 mm, for example. The neck portion 14 has a cylindrical shape with a diameter dimension of about 3.85 mmφ and a length dimension of about 4 mm, for example, and the diameter dimension gradually decreases from the shank portion 12 toward the neck portion 14 as shown in FIG. A tapered portion is provided. The blade portion 16 has, for example, an axial length dimension (blade length) of about 4 mm and a diameter size of about 4 mmφ, and the spherical surface in the partial spherical portion 16a corresponds to, for example, a radius of about 2 mm. The rake angle θ of the edge 18a of the slit 18 is, for example, about 10 ° in the cross-sectional shape of the central angle φ = 45 °. The width dimension w of the slit 18 is, for example, about 0.1D (when D = 4 mm, w = 0.4 mm) in the cross-sectional shape with the central angle φ = 45 °. The depth dimension d of the slit 18 is, for example, about 0.2D at the deepest portion (w = 0.8 mm when D = 4 mm).

  In the cutting of the work material by the ball end mill 10 of the present embodiment configured as described above, the shank portion 12 is attached to a cutting device such as a machining center (not shown) and is driven to rotate around the axis by the cutting device. As a result, the workpiece 18 is cut by the edge 18 a of the slit 18. That is, the edge 18 a of the slit 18 functions as a ball blade (cutting edge) in the cutting process by the ball end mill 10. The ball end mill 10 of this embodiment is preferably used for cutting for processing a three-dimensional curved surface including a cavity of a mold. For example, it is suitable for machining of dies by the contour processing method that performs cutting while changing the height of the part to be processed stepwise, etc. Used. Here, in the blade portion 16 of the ball end mill 10 of the present embodiment, the surface of the partial spherical portion 16a is configured to come into contact (sliding contact) with the work surface of the work material during the cutting process. Due to the burnishing effect (burnishing), the surface roughness of the machined surface after cutting can be made close to a polished surface of 1.2 μm or less at the maximum height Rz (JIS B 0601: 2001). Furthermore, the slit 18 in which the edge 18a functions as a ball blade is formed in the partial spherical portion 16a, so that even when there is an uncut residue, the finish cutting process is preferably extended to a process close to a grinding process. It can be carried out.

  Subsequently, a test conducted by the present inventors in order to verify the effect of the present invention will be described. The present inventors have formed a second surface (flank) corresponding to a second angle of 17 ° along the ball blade, the width of the second surface is 0.1 mm, and the rake angle of the ball blade In the R2 ball end mill conventional product (standard product) with 5 °, no coating, and the three slits 18 are radially formed in the partial spherical portion 16a, and the cross section of the central angle φ = 45 ° A book in which the rake angle θ of the edge 18a is 10 °, the slit width w is 0.4 mm (= 0.1D), and the slit depth d at the boundary with the outer peripheral portion 16b is 0.8 mm (= 0.2D). A ball end mill 10 of the example was prepared, and a cutting test was performed using the respective ball end mills under the following cutting conditions.

[Cutting conditions]
Work material: STAVAX (registered trademark) 50HRC
・ Work material shape: R11mm core shape ・ Scanning line processing ・ Tool shape: R2 ball end mill ・ Spindle speed: 20000rpm
・ Feeding speed: 1000mm / min
・ Pick feed: 0.1mm
・ Cut amount: 0.05mm
・ Cutting oil: Center-through oil mist

  5 to 8 exemplify a roughness curve indicating the surface roughness of the cut surface after cutting by each sample as a result of the cutting test, and the cutting surface of the cut surface after cutting by the conventional product is illustrated. FIG. 5 shows a roughness curve in the pick feed direction, FIG. 6 shows a roughness curve in the feed direction (circumferential direction of the work material circumferential surface), and picks the work surface after cutting by the ball end mill 10 of this embodiment. The roughness curve in the feed direction is shown in FIG. 7, and the roughness curve in the feed direction is shown in FIG. On the work surface corresponding to the roughness curves shown in FIGS. 5 and 6, that is, the work surface after cutting with a conventional product, the ten-point average roughness Ra (JIS B 0601: 2001) in the pick feed direction is 0.309 μm, the maximum The height Rz (JIS B 0601: 2001) was 1.725 μm. The ten-point average roughness Ra in the feed direction was 0.214 μm, and the maximum height Rz was 1.379 μm. On the other hand, on the work surface corresponding to the roughness curve shown in FIGS. 7 and 8, that is, the work surface after cutting by the ball end mill 10 of this embodiment, the ten-point average roughness Ra in the pick feed direction is 0.08 μm, the maximum. The height Rz was 1.12 μm. The ten-point average roughness Ra in the feed direction was 0.07 μm, and the maximum height Rz was 0.98 μm. As is clear from these results, the surface roughness of the work surface after cutting by the ball end mill 10 of this embodiment is higher than the work surface after cutting by the conventional product in both the pick feed direction and the feed direction. It is greatly improved and it can be seen that a finish close to the machined surface after polishing is obtained.

  As described above, according to this embodiment, at least one slit 18 is formed radially from the tip of the partial spherical portion 16a, and the edge 18a of the slit 18 functions as a ball blade in cutting. From the above, it is possible to realize cutting with an emphasis on finishing by using the specifications of the partial spherical portion 16a, and even if there is any uncut material, the slit 18 functioning as a cutting edge can be used to extend the finish cutting work. Therefore, processing close to grinding can be performed. In other words, it is possible to provide the ball end mill 10 that has a sufficiently good surface roughness after cutting.

  In the cross-sectional shape with the central angle φ = 45 ° of the partial spherical portion 16a with respect to the axial center C of the partial spherical portion 16a, the rake angle θ of the edge 18a of the slit 18 is within a range of 5 ° to 15 °. Therefore, necessary and sufficient cutting performance can be imparted to the edge 18a of the slit 18, and the slit 18 can perform a finish cutting process and a process close to a grinding process.

  With respect to the axial center C of the partial spherical portion 16a, the width d of the slit 18 is in the range of 0.05D or more and 0.15D or less in the cross-sectional shape of the partial spherical portion 16a with the central angle φ = 45 °. Therefore, in addition to being able to impart the necessary and sufficient cutting performance to the edge 18a of the slit 18, the remaining partial spherical portion 16a can realize cutting with an emphasis on finishing.

  The preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and may be implemented in other modes.

  For example, the ball end mill of the present invention realizes a surface roughness close to the polished surface with respect to the cut surface after cutting, but after the cutting of the work material by the ball end mill of the present invention, the work surface is polished. May be applied. Even in such an aspect, since the processing can be performed in a shorter time than the polishing of the work material cut by the conventional ball end mill, the effect of the present invention can be achieved. Further, the ball end mill of the present invention may be used exclusively for finishing after cutting by another ball end mill for cutting. Even in such an aspect, it is possible to significantly reduce the human or time cost of manual polishing.

  In the above-described embodiment, the rake angle θ of the edge 18a of the slit 18 is 5 ° or more in the sectional shape of the central angle φ = 45 ° of the partial spherical portion 16a with respect to the axis C of the partial spherical portion 16a. The ball end mill 10 in which the width dimension d of the slit 18 is within a range of 0.05D or more and 0.15D or less is exemplified within a range of 15 ° or less, but these numerical ranges show the best embodiment. Even in a configuration that deviates from such a numerical range, the effect of the present invention is achieved.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

  10: Ball end mill, 16a: Partial spherical portion, 18: Slit, 18a: Edge

Claims (3)

A ball end mill that is provided with a partial spherical portion at the tip of the tool body and performs cutting with a ball blade formed in the partial spherical portion,
A ball end mill characterized in that at least one slit is formed radially from the tip of the partial spherical portion, and an edge of the slit functions as the ball blade.   2. The ball according to claim 1, wherein a rake angle of the edge of the slit is in a range of 5 ° to 15 ° in a cross-sectional shape having a central angle of 45 ° of the partial spherical portion with respect to the axial center of the partial spherical portion. End mill.   3. The width dimension of the slit is in a range of 0.05 D or more and 0.15 D or less in a cross-sectional shape having a central angle of 45 ° of the partial spherical portion with respect to the axial center of the partial spherical portion. Ball end mill.