JP2008110411A - Cbn end mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CBN end mill in which the strength of the cutter tip is increased while a prescribed sharpness in cutting is secured, capable of enhancing processing conditions including cut in depth, feeding speed, etc. <P>SOLUTION: The CBN end mill is structured so that its peripheral cutting edge 18 is inclined at a twist angle λ (=-3° to -18°) from the axis O in such a manner as twisting in the direction opposite the rotating direction in machining viewed from the shank 12s side, so that the rake angle in the axial direction in the corner part 24 at the tip of the peripheral cutting edge 18 in the axial direction becomes negative (the same as the twist angle λ), which allows enhancing the strength of the cutter tip owing to increase of the cutter tip angle and suppressing chipping of the cutting edge. If chipping is suppressed as described, there is no need to round the cutter tip by a chamfering process such as lapping, honing, etc., it is possible to stabilize the machining performance, secure the prescribed sharpness in cutting, enhance the strength of the cutter tip, and also enhance the processing efficiency by heightening the processing conditions including cut in depth, feeding speed, etc. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a CBN end mill in which an outer peripheral blade and a bottom blade are composed of an ultra-high pressure CBN sintered body, and more particularly, to a CBN end mill capable of improving machining efficiency by increasing a cutting size and a feed rate. It is.

A CBN end mill has been proposed in which the outer peripheral edge and the bottom edge are made of an ultra-high pressure CBN (cubic boron nitride) sintered body. In Patent Document 1, a rectangular parallelepiped ultra-high-pressure CBN sintered body is integrally fixed to a tool body made of cemented carbide by brazing or the like, and then subjected to cylindrical grinding to obtain an outer peripheral blade. Techniques for forming are described. In Patent Document 2, a cylindrical ultra-high pressure CBN sintered body is integrally fixed by brazing or the like at the tip portion in the axial direction, and then grooves are formed in the ultra-high pressure CBN sintered body by grinding. For example, a technique for forming an outer peripheral blade or a bottom blade (ball blade) is described.
JP 2002-178211 A JP 2002-144132 A

  By the way, the outer peripheral blade of such a conventional CBN end mill is a twisted blade twisted in the same direction as the cutting rotation direction seen from the shank side, or a straight blade parallel to the shaft center. Since the rake angle in the axial direction is 0 ° or positive at the corner, that is, the corner connected to the bottom blade, sufficient blade edge strength is not always obtained, and chipping and other chipping are likely to occur, and the cutting size and feed There was a problem that processing conditions such as speed were restricted. On the other hand, the cutting edge is rounded by chamfering such as lapping and honing. However, it is difficult to raise the processing conditions because the cutting performance tends to vary and the sharpness deteriorates.

  The present invention has been made in the background of the above circumstances, and the object of the present invention is to increase the cutting edge strength and the machining conditions such as the cutting size and feed speed while ensuring a predetermined sharpness in the CBN end mill. Is to be able to.

  In order to achieve such an object, according to a first aspect of the present invention, there is provided a CBN end mill in which an outer peripheral blade and a bottom blade are formed of an ultra-high pressure CBN sintered body, wherein the outer peripheral blade is in a cutting rotation direction viewed from the shank side. And tilted with respect to the axis O so as to be twisted in the opposite direction.

  In the second invention, at least the tip portion in the axial direction is made of an ultra-high pressure CBN sintered body, and the outer peripheral blade is formed along the groove by providing a groove on the outer peripheral surface of the tip portion. At the same time, in the CBN end mill in which a bottom blade is provided continuously to the outer peripheral blade, the groove is inclined with respect to the axis O so as to be twisted in the opposite direction to the cutting rotation direction viewed from the shank side. Thus, the outer peripheral blade is inclined with respect to the axis O so as to be twisted in the opposite direction to the cutting rotation direction seen from the shank side.

  According to a third aspect of the present invention, in the CBN end mill of the second aspect, the groove is a twisted groove twisted around the axis O or a linear groove inclined with respect to the axis O.

  According to a fourth invention, in the CBN end mill according to any one of the first to third inventions, an inclination angle λ with respect to the axis O of the outer peripheral blade is −3 ° to −18 with a positive inclination toward the cutting rotation direction. It is within the range of °.

According to a fifth invention, in the CBN end mill according to any one of the first to fourth inventions, a rake angle γ _{1 of the} outer peripheral blade is in a range of −5 ° to −35 °.

  According to a sixth aspect of the present invention, in the CBN end mill according to any one of the first to fifth aspects of the present invention, when a straight bottom blade is provided, the corner portion where the bottom blade and the outer peripheral blade are connected is around the axis O. The rotation trajectory shape is configured to have an arc shape in a cross section including the axis O.

  In such a CBN end mill, the outer peripheral blade is inclined with respect to the axial center O so as to be twisted in the opposite direction to the cutting rotation direction viewed from the shank side. The rake angle in the axial direction at the part is negative, the blade edge angle is increased, the blade edge strength is improved, and the chipping is suppressed. When the chipping is suppressed in this way, it is not necessary to round the cutting edge by chamfering such as lapping or honing, so that the cutting performance can be stabilized and a predetermined sharpness can be secured. Combined with the improvement of the strength, the machining efficiency can be improved by increasing the machining conditions such as the cutting size and feed rate.

  The second invention is a case where a groove is provided in an ultra-high pressure CBN sintered body to form an outer peripheral blade or a bottom blade, which substantially corresponds to one embodiment of the first invention, and is the same as the first invention. The effect is obtained.

  The third invention is a case where a torsion groove twisted around the axis O or a linear groove inclined with respect to the axis O is provided in the ultra-high pressure CBN sintered body. Since the groove can be ground without rotating the body around the axis O, the groove can be easily and quickly processed with simple equipment.

  In the fourth invention, since the inclination angle λ with respect to the axis O of the outer peripheral blade is within a range of −3 ° to −18 °, the strength of the blade edge is improved while ensuring a predetermined sharpness, and the processing conditions are increased. Efficiency can be improved.

In the fifth invention, since the rake angle γ _{1 of the} outer peripheral blade is in the range of −5 ° to −35 °, it is sufficient to ensure a predetermined sharpness not only in the corner portion at the tip in the axial direction but also in the entire outer peripheral blade. Cutting edge strength can be obtained, and it can cope with improvement in machining efficiency.

  6th invention is a case where it has a linear bottom blade, The corner part to which the bottom blade and an outer periphery blade are connected comprises circular arc shape in the cross section containing the shaft center O in the rotation locus shape around the shaft center O. Therefore, the chipping at the corner portion is further effectively suppressed.

  The present invention is preferably applied to a square end mill having a square corner, but can also be applied to a radius end mill or a ball end mill having a round corner. In the ball end mill, the chipping at the corner where the outer peripheral blade and the ball blade (bottom blade) are connected is effectively suppressed, and the processing efficiency such as the cutting depth and feed rate can be increased to improve the processing efficiency. It can be done.

  As described in Patent Document 1, a CBN end mill is formed by fixing an ultra-high pressure CBN sintered body having a rectangular parallelepiped shape or the like integrally to a tool body made of cemented carbide by brazing or the like. An outer peripheral blade or a bottom blade may be formed by grinding or the like, and as described in Patent Document 2, a cylindrical ultra-high pressure CBN sintered body is integrally formed by brazing or the like at the tip portion in the axial direction. After the fixing, the outer peripheral blade and the bottom blade may be formed by forming grooves in the ultra-high pressure CBN sintered body by grinding or the like, and various modes are possible. The number of peripheral blades and bottom blades is suitably 2 blades to 4 blades, but may be 1 blade or 5 blades or more, and is appropriately set according to the diameter and the like.

  The outer peripheral blade is inclined with respect to the axis O so as to be twisted in the opposite direction to the cutting rotation direction as viewed from the shank side. Specifically, when the cutting rotation direction is right rotation, When the cutting rotation direction is counterclockwise, it becomes a right twist.

  In the third invention, for example, as described in Patent Document 2, a cylindrical ultra-high pressure CBN sintered body is integrally fixed to a tip portion in the axial direction by brazing or the like, and then the ultra-high pressure CBN sintered body is attached to the ultra-high pressure CBN sintered body. When a groove is formed by grinding or the like to provide an outer peripheral edge or a bottom edge, when forming a torsion groove, the grinding wheel is relatively close to the ultra-high pressure CBN sintered body and cut to a predetermined depth. Thereafter, grinding may be performed by rotating the ultra-high pressure CBN sintered body around the axis O while moving it relatively in the axial direction according to the twist angle. When forming the straight groove, it is only necessary to make the grinding wheel approach or approach and move linearly in a predetermined inclination direction without rotating the ultra-high pressure CBN sintered body around the axis O.

  Even when a super-high pressure CBN sintered body having a rectangular parallelepiped shape or the like is integrally fixed to a tool body by brazing or the like, as in Patent Document 1, and then subjected to cylindrical grinding or the like to form an outer peripheral blade or a bottom blade. It is possible to provide an outer peripheral blade similar to the outer peripheral blade formed along the twisted groove or the straight groove.

  When the inclination angle λ with respect to the axis O of the outer peripheral blade is larger than −3 ° with the positive inclination in the cutting rotation direction side, sufficient blade edge strength cannot be obtained, whereas when it is smaller than −18 °, the sharpness becomes worse. As in the fourth invention, the range of -3 ° to -18 ° is appropriate. This inclination angle λ corresponds to a twist angle when the outer peripheral blade is a twist blade. In the case of the outer peripheral blade provided along the straight groove, the inclination angle λ changes successively in a strict sense, but it is desirable that it is within the above angle range over the entire length of the outer peripheral blade.

When the rake angle γ ₁ of the outer peripheral blade is larger than −5 °, sufficient blade edge strength cannot be obtained. On the other hand, when it is smaller than −35 °, the sharpness is deteriorated. Therefore, as in the fifth invention, −5 ° to −35. Within the range of ° is appropriate.

  In the sixth aspect of the invention, the corner portion where the straight bottom blade and the outer peripheral blade are connected is configured to form an arc shape in the shape of the rotation trajectory. The radius of the arc shape prevents the chipping of the blade. It is desirable that the thickness is 0.1 mm or more, and it varies depending on the diameter, but for example, within a range of about 0.1 mm to 0.5 mm, or within a range of 0.05 D to 0.25 D with respect to the tool diameter D is appropriate. is there. When implementing other inventions, it is not always necessary to have an arc shape, and a corner portion of a square shape such as a right angle may be used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1A and 1B are diagrams for explaining a two-blade CBN square end mill 10 according to an embodiment of the present invention. FIG. 1A is a front view as viewed from a direction perpendicular to the axis O, and FIG. (C) is a bottom view seen from the right side of (b), that is, from the tip side. (D) is a view seen from the lower side of (c). The phase around the axis O is 90 ° relative to (b). It is a different front view. The CBN square end mill 10 is a tool body 12 in which a blade portion 14 made of an ultra-high pressure CBN sintered body is concentrically fixed to a tip end of a cemented carbide alloy tool body 12 by brazing. Is integrally provided with a cylindrical shank 12s, and cutting is performed by being rotated clockwise around the axis O as viewed from the shank 12s side (left side in FIG. 1 (a)).

  The diameter dimension of the blade portion 14, that is, the tool diameter D is 2 mm, and the axial dimension is about 1.5 mm. The blade portion 14 is provided with a pair of outer peripheral blades 18 along the twist groove 16 by grinding the pair of twist grooves 16 on the outer peripheral surface of the cylindrical super high pressure CBN sintered body. The straight bottom blade 22 is provided continuously to the outer peripheral blade 18 by grinding the gasche 20 at the axial tip portion of the torsion groove 16. The twist groove 16 is provided in a direction opposite to the cutting rotation direction as viewed from the shank 12s side, that is, left-handed twist, and the twist angle λ is −3 ° to −18 ° with a positive inclination toward the rotational cutting direction. It is set within the range, more preferably within the range of −5 ° to −15 °.

Such a twisted groove 16 is formed by rotating the grinding wheel and rotating the grinding wheel relatively close to the blade portion 14 and cutting it to a predetermined depth. Then, the blade portion 14 is integrated with the tool body 12 according to the twist angle λ. Grinding may be performed by rotating around the axis O and relatively moving in the axial direction. Further, the rake angle of the rake face of the outer peripheral edge 18 constituted by the twist groove 16 is set within a range of −5 ° to −35 °, more preferably within a range of −10 ° to −30 °. The clearance angle α ₁ of the second surface of the outer peripheral blade 18 is about 20 °. The twist angle λ corresponds to an inclination angle at which the outer peripheral edge 18 is inclined with respect to the axis O.

The clearance angle α ₂ of the second face of the bottom blade 22 is about 20 °, and the rake angle γ ₂ of the rake face of the bottom blade 22 constituted by the gash 20 is about −20 °. Further, the corner portion 24 to which the bottom blade 22 and the outer peripheral blade 18 are connected is configured so as to form an arc shape in a cross section including the axis O in the shape of the rotation locus around the axis O. In the example, the radius R of the arc shape is about 0.2 mm (= 0.1D). The bottom blade 22 is inclined so as to be recessed from the corner portion 24 toward the axial center O side, and its center concave angle φ is about 2 °.

  In such a CBN square end mill 10 of this embodiment, the torsion angle λ (= −3 ° to −18 °) so that the outer peripheral edge 18 is twisted in the opposite direction to the cutting rotation direction seen from the shank 12s side. ) Is inclined with respect to the axis O, the rake angle in the axial direction at the corner 24 at the tip in the axial direction of the outer peripheral blade 18 becomes negative (same as the torsion angle λ), and the cutting edge angle increases and the cutting edge increases. Strength is improved and chipping of the blade is suppressed. When the chipping is suppressed in this way, it is not necessary to round the cutting edge by chamfering such as lapping or honing, so that the cutting performance can be stabilized and a predetermined sharpness can be secured. Combined with the improvement of the strength, the machining efficiency can be improved by increasing the machining conditions such as the cutting size and feed rate.

  In particular, in the present embodiment, the corner portion 24 to which the linear bottom blade 22 and the outer peripheral blade 18 are connected is configured to form an arc shape in a cross section including the axis O in the shape of the rotation locus around the axis O. Therefore, the chipping of the corner portion 24 is further effectively suppressed.

  Further, in this embodiment, the inclination angle of the outer peripheral blade 18 with respect to the axis O, that is, the twist angle λ is in the range of −3 ° to −18 °, so that the blade edge strength is improved while ensuring a predetermined sharpness, The processing efficiency can be improved by increasing the processing conditions.

In the present embodiment, since the rake angle γ ₁ of the outer peripheral blade 18 is in the range of −5 ° to −35 °, a predetermined sharpness is provided not only in the corner portion 24 at the tip in the axial direction but also in the entire region of the outer peripheral blade 18. A sufficient cutting edge strength can be obtained while ensuring, and it is possible to cope with an improvement in processing efficiency.

Incidentally, 10 types (No1 to No10) of test products having different twist angles λ and rake angles γ ₁ of the outer peripheral edge 18 are prepared, side cutting is performed under the test conditions shown in FIG. Further, when the possibility of processing was examined based on the presence or absence of chipping of the bottom blade 22, the result shown in FIG. 2 (b) was obtained. Note that test products No. 4 to No. 10 having a negative twist angle λ are the present invention products, and test products No. 1 to No. 3 having a twist angle λ of 0 ° or more are comparative products.

As is clear from the results of FIG. 2 (b), the present invention product specimens No4～No10, feed 0.01 mm / blade, cut a _r is if 0.01 D (0.02 mm), the outer periphery Cutting could be performed without chipping of the blade 18 and the bottom blade 22. In particular, in the case of test products No. 4 to No. 9 in which the twist angle λ is in the range of −3 ° to −18 ° and the rake angle γ ₁ is in the range of −5 ° to −35 ° as in the above example, Even if the feed is increased to 0.03 mm / blade and the cut a _r is increased to 0.05 D (0.1 mm), the outer peripheral blade 18 and the bottom blade 22 can be cut without causing chipping.

On the other hand, the test sample No. 2 which is a comparative product has a twist angle λ of + 15 °, but the rake angle γ ₁ is −30 ° and the blade edge angle is large, so that the feed is 0.01 mm / blade and the cut a _r is With the processing conditions of 0.01D (0.02 mm), cutting could be performed without chipping. However, if the processing conditions are higher than that, chipping occurs as in the case of other comparative products (test products No. 1 and No. 3) and the processing becomes impossible.

  In the above-described embodiment, the twisted groove 16 twisted around the axis O is provided by grinding on the blade portion 14 made of an ultra-high pressure CBN sintered body, and the outer peripheral blade 18 is formed along the twisted groove 16. However, since the axial length of the blade portion 14 is as short as about 1.5 mm and the torsion angle λ is small within the range of −5 ° to −18 °, the inclination with respect to the axis O is small. An inclined linear groove may be provided. In that case, without rotating the blade portion 14 about the axis O, the grinding wheel is driven to rotate and relatively close to the blade portion 14 up to a predetermined cutting depth or close to the predetermined depth. Since the groove can be ground by simply moving linearly in the tilt direction, the groove can be easily and quickly processed with simple equipment.

  As mentioned above, although the Example of this invention was described in detail based on drawing, these are one embodiment to the last, and this invention is implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the CBN square end mill which is one Example of this invention, (a) is a front view, (b) is an enlarged view of a front-end | tip part, (c) is a bottom view seen from the front end side, (d) is ( FIG. 3C is a front view in which the phase around the axis O is 90 ° different from that in FIG. Side cutting was performed using 10 types (No1 to No10) of test pieces having different torsion angles λ and rake angles γ _{1 in} FIG. 1, and the feasibility of processing was examined based on the presence or absence of chipping of the outer peripheral edge and the bottom edge. It is a figure explaining a result, (a) is a test condition, (b) is a figure which shows the determination result of processing availability.

Explanation of symbols

10: CBN square end mill (CBN end mill) 14: Blade portion (super high pressure CBN sintered body) 16: Twist groove (groove) 18: Outer peripheral blade 22: Bottom blade 24: Corner portion O: Shaft center γ ₁ : Rake angle λ: Twist angle (tilt angle)

Claims (6)

In the CBN end mill in which the outer peripheral blade and the bottom blade are composed of an ultra-high pressure CBN sintered body,
The CBN end mill, wherein the outer peripheral blade is inclined with respect to the axis O so as to be twisted in a direction opposite to a cutting rotation direction viewed from the shank side. At least the tip in the axial direction is made of an ultra-high pressure CBN sintered body, and the outer peripheral blade is formed along the groove by providing a groove on the outer peripheral surface of the tip. In the CBN end mill in which the bottom blade is provided continuously,
The groove is inclined with respect to the axis O so as to twist in the opposite direction to the cutting rotation direction seen from the shank side, so that the outer peripheral blade is opposite to the cutting rotation direction seen from the shank side. The CBN end mill is inclined with respect to the axis O so as to be twisted in the direction. The CBN end mill according to claim 2, wherein the groove is a twisted groove twisted around the axis O or a linear groove inclined with respect to the axis O. The inclination angle λ with respect to the axis O of the outer peripheral blade is within a range of −3 ° to −18 ° with a positive inclination in the cutting rotation direction side. The CBN end mill according to Item. The rake angle γ _{1 of the} outer peripheral blade is within a range of -5 ° to -35 °. The CBN end mill according to any one of claims 1 to 4. In the case of having a straight bottom blade, the corner portion where the bottom blade and the outer peripheral blade are connected is configured to form an arc shape in a cross section including the axis O in the shape of the rotation locus around the axis O. The CBN end mill according to any one of claims 1 to 5, wherein the CBN end mill is provided.

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