JP6477015B2 - Radius end mill - Google Patents

Description

  The present invention relates to a radius end mill made of ceramic.

2. Description of the Related Art A radius end mill made of ceramic is known as disclosed in, for example, Patent Document 1 below. The radius end mill has an axial end mill main body, and the end mill main body is formed with a chip discharge groove, an outer peripheral blade, a bottom blade (tip blade) and a corner blade.
At the time of cutting, the radius end mill is fed in the direction intersecting the axis and cut into the work material while being rotated in the tool rotation direction among the circumferential directions around the axis of the end mill main body.

  More specifically, in the radius end mill, a plurality of chip discharge grooves extending from the tip end of the end mill body toward the base end side are formed circumferentially at intervals in the outer circumference of the end mill body. Further, an outer peripheral edge is formed on a cross ridge line between a wall surface of the chip discharge groove facing the tool rotation direction and an outer peripheral surface of the end mill main body. In addition, a bottom edge is formed at a cross ridge line between the wall surface of the chip discharge groove and the tip surface of the end mill body. In addition, on the tip outer peripheral portion (corner portion) of the wall surface of the chip discharge groove, there is formed a convexly curved corner blade connecting the outer end (radially outer end edge) of the bottom blade and the tip of the outer peripheral blade. It is done.

  Generally, in this type of radius end mill, in order to increase the processing speed of cutting, the radial rake angle (outer peripheral rake angle) of the outer peripheral blade is set to a positive (positive) angle. Specifically, as the radial rake angle of the outer peripheral blade is set to a large positive angle, the outer peripheral blade is sharply cut into the work material, and the sharpness is enhanced. Since the cutting resistance is reduced by enhancing the sharpness, the cutting speed can be increased to improve the processing efficiency.

  On the other hand, in the radius end mill of Patent Document 1, the radial rake angle of the outer peripheral blade is set to -4 ° to 0 °, and is set to a negative (negative) angle close to a positive angle. This is because the radius end mill of Patent Document 1 is made of ceramic, and by setting the radial rake angle of the outer peripheral blade to a negative angle, the blade angle is increased and the edge strength is secured.

U.S. Pat. No. 8,647,025

  However, in the radius end mill of Patent Document 1, the outer peripheral blade wears (wears off) early, and the tool life is short. In order to suppress such wear of the outer peripheral blade, it is preferable to reduce the cutting resistance at the time of processing. That is, as described above, it is conceivable to increase the sharpness by increasing the radial rake angle of the outer peripheral blade to the regular angle side.

However, since the radius end mill of Patent Document 1 is made of ceramic, if the radial rake angle of the outer peripheral blade is increased to the positive angle side, the blade angle is reduced and the edge strength can not be secured.
In addition, for this type of radius end mill, it has been required to further increase the cutting speed to improve the processing efficiency.

  The present invention has been made in view of such circumstances, and while the end mill main body is formed of ceramic, the cutting speed is increased while the cutting edge strength and the wear resistance of the outer peripheral blade are sufficiently ensured. It is an object of the present invention to provide a radius end mill which can improve the efficiency and extend the tool life.

In order to solve such problems and achieve the above object, the present invention proposes the following means.
That is, the radius end mill according to the present invention is formed on an end mill main body made of a shaft and made of ceramic, and the outer periphery of the end mill main body, and gradually rotates around the axis from the tip along the axial direction of the end mill main body An outer periphery formed at a cross ridge line of a chip discharge groove extending toward the opposite side to the tool rotation direction in the circumferential direction, a wall surface of the chip discharge groove facing the tool rotation direction, and an outer peripheral surface of the end mill body A blade, a bottom blade formed on a cross ridge line between the wall surface of the chip discharge groove and a tip surface of the end mill body, and an outer end of the bottom blade located on a tip outer peripheral portion of the end mill body And a corner blade having a convex curve shape that connects the tip of the outer peripheral blade and is convex toward the tip outer peripheral side of the end mill main body; the outer peripheral blade, the bottom blade, and Of over Na blades, radial rake angle of at least the outer peripheral blade, is set to a negative angle, the radial rake angle of the peripheral blade, Ri -20 ° ~-10 ° der, twisting of the peripheral cutting edge The corners are characterized by 30 ° to 40 ° .

  In the radius end mill of the present invention, the end mill body is formed of ceramic. And at least the radial rake angle (outer peripheral rake angle) of the outer peripheral blade among the outer peripheral blade, the base blade and the corner blade is set to a negative angle, specifically, the radial rake angle of the outer peripheral blade is -20. It is considered to be ° to -10 °.

  Here, the “radial rake angle of the outer peripheral blade” referred to in the present specification is orthogonal to the axis O in a cross sectional view of the end mill main body 2 shown in FIG. 4 (a cross sectional view perpendicular to the axis O of the end mill main body 2). Among the radial directions, a predetermined radial direction D (corresponding to a so-called "reference surface") passing through the outer peripheral blade 6 and a rake surface 4a of the outer peripheral blade 6 (tool rotation of the chip discharge groove 4 adjacent to the outer peripheral blade 6) Of the acute and obtuse angles formed with the wall surface portion facing in the direction T, the acute angle α is referred to.

Further, when the radial rake angle is "-(minus)", that is, a negative (negative) angle, the rake face 4a of the outer peripheral blade 6 in the radial direction in the cross-sectional view of the end mill body 2 shown in FIG. Is the angle α when extending obliquely to the opposite side to the tool rotation direction T as it goes outward. In this case, the rake surface 4 a of the outer peripheral blade 6 is disposed in the tool rotational direction T with respect to the predetermined radial direction D (reference surface).
Although not shown in particular, the rake face 4 a of the outer peripheral blade 6 in the cross-sectional view of the end mill body 2 indicates that the radial rake angle is “+ (plus)”, that is, a positive angle. It is an angle α when it extends obliquely toward the tool rotational direction T as it goes radially outward. In this case, the rake face 4 a of the outer peripheral blade 6 is disposed on the opposite side to the tool rotational direction T with respect to the predetermined radial direction D (reference plane).

  In the present invention, the radial rake angle (the above angle α) of the outer peripheral blade is a negative angle, and is set to a large negative angle side of −20 ° to −10 °. For this reason, at the time of cutting, the cutting resistance of the outer peripheral edge of the radius end mill to the work material is increased, and the cutting heat (heat generation due to plastic deformation in shear region, frictional heat, etc.) is also increased accordingly.

When the cutting heat becomes high, the cutting surface (the portion to be processed) of the material to be cut is softened as compared with the outer peripheral edge of the ceramic heat-resistant radius end mill. That is, the hardness of the processed portion is significantly reduced with respect to the outer peripheral blade.
As a result, the outer peripheral blade can be cut at high speed so as to scrape (scrub) the material to be cut. Further, since the hardness of the radius end mill is relatively increased as compared with the softened work material, the wear (abrasion) of the outer peripheral edge is remarkably suppressed, and the tool life is extended.

That is, the inventor of the present invention intentionally increases the cutting heat at the time of cutting by setting the radial rake angle of the outer peripheral blade to the above-mentioned numerical range as a result of repeated research on the radius end mill made of ceramic. As a result, the cutting speed can be dramatically increased by cutting the cutting material so that the material to be cut is softened while maintaining the hardness of the radius end mill and scraping off the material to be cut due to the difference in hardness. It came to gain knowledge.
That is, the cutting mode (processing form) by the radius end mill of the present invention is greatly different from the cutting mode of the conventional general radius end mill.

Specifically, according to the radius end mill of the present invention, when a heat-resistant alloy such as INCONEL (registered trademark) is cut as a material to be cut, it is compared to a radius end mill (conventional product) made of general cemented carbide. It has been confirmed that a processing efficiency of 10 times or more can be realized.
In addition, with the outer peripheral blade of the radius end mill of the present invention, the blade angle is sufficiently secured by setting the radial rake angle to the above-mentioned numerical range, and the edge strength is improved. Therefore, chipping or the like of the cutting edge is less likely to occur.

If the radial rake angle of the outer peripheral blade is smaller than -20 °, that is, if it is larger on the negative angle side, the sharpness of the outer peripheral blade is too low, and the cutting material is softened by the cutting heat. Even, it becomes difficult to increase the cutting speed.
In addition, when the radial rake angle of the outer peripheral blade exceeds -10 °, the radial rake angle becomes too close to the regular angle side, and a desired cutting heat can not be obtained. That is, since the cutting heat can not be sufficiently increased, the work material is not softened, and the above-described effects of the present invention can not be obtained. In addition, the outer peripheral blade may wear prematurely to reach the tool life.
Therefore, in the present invention, the radial rake angle of the outer peripheral blade is -20 ° to -10 °.

As described above, according to the present invention, although the end mill body is formed of ceramic, the cutting speed can be increased to improve the processing efficiency while sufficiently securing the edge strength and wear resistance of the outer peripheral blade, and also the tool life It can be extended.
According to the present invention, the twist angle of the outer peripheral blade is set to 30 ° to 40 °.
Here, the “twist angle” in the present specification means the axis O (or the side view in which the end mill body 2 is seen from the radial direction orthogonal to the axis O) of the end mill body 2 shown in FIG. The acute angle and the obtuse angle formed between the straight line parallel to the axis O) and the outer peripheral blade 6 (twist helical wire) point to the acute angle β.
In general, for example, in a radius end mill (conventional product) made of cemented carbide, the twist angle of the outer peripheral edge is set to be larger than 40 °. Thus, by setting the twist angle to a large positive angle, the outer peripheral blade is sharply cut into the work material, and the sharpness can be enhanced.
On the other hand, in the above configuration of the present invention, the twist angle of the outer peripheral blade is set as small as 30 ° to 40 ° to intentionally increase the cutting resistance of the outer peripheral blade with respect to the work material. As a result, at the time of cutting, the cutting resistance of the outer peripheral edge of the radius end mill to the work material is increased, and the cutting heat (heat generation due to plastic deformation in the shear region, frictional heat, etc.) is also increased.
When the cutting heat becomes high, the cutting surface (the portion to be processed) of the material to be cut is softened as compared with the outer peripheral edge of the ceramic heat-resistant radius end mill. That is, the hardness of the processed portion is significantly reduced with respect to the outer peripheral blade.
As a result, the outer peripheral blade can be cut at high speed so as to scrape (scrub) the material to be cut. Further, since the hardness of the radius end mill is relatively increased as compared with the softened work material, the wear (abrasion) of the outer peripheral edge is remarkably suppressed, and the tool life is extended.
That is, according to the above configuration, the above-described effects of the present invention can be made particularly remarkable.
Specifically, by setting the twist angle of the outer peripheral blade to be larger than 30 °, it is possible to secure a sufficient sharpness for scraping off the work material softened by the cutting heat at the outer peripheral blade.
Further, by making the twist angle of the outer peripheral blade smaller than 40 °, the cutting resistance of the outer peripheral blade can be increased to such an extent that cutting heat sufficient to soften the work material can be obtained. it can.

  Moreover, in the radius end mill of this invention, it is preferable that the radial rake angle of the said outer periphery blade is -17.5 degree--12.5 degree.

In this case, the above-described effects according to the present invention can be obtained more reliably and stably. When the radial rake angle of the outer peripheral blade is set to -15 °, the most remarkable effect is obtained.
Further, in the radius end mill of the present invention, the twist angle of the outer peripheral blade is preferably 30 ° to 35 °.

  In the radius end mill of the present invention, preferably, the end mill body is made of sialon.

  In this case, since the end mill main body is made of sialon (SiAlON) of a ceramic material, the end mill main body is excellent in heat resistance, thermal shock resistance, mechanical strength in a high temperature environment, abrasion resistance and the like. Therefore, the above-mentioned effects of the present invention become much more remarkable and stably achieved.

  According to the radius end mill of the present invention, although the end mill body is formed of ceramic, the cutting speed can be increased to improve the processing efficiency while sufficiently securing the edge strength and wear resistance of the outer peripheral blade, and also the tool life It can be extended.

It is a perspective view showing a radius end mill concerning one embodiment of the present invention. It is a side view which shows the radius end mill of FIG. It is a front view which shows the radius end mill of FIG. It is a figure which shows the XX cross section of FIG. It is a graph which contrasts the Example of this invention, and the conventional comparative example, and represents the relationship between the radial rake angle of a peripheral blade, and cutting length.

  Hereinafter, a radius end mill 1 according to an embodiment of the present invention will be described with reference to the drawings.

[Schematic configuration of radius end mill and end mill main body]
As shown in FIGS. 1 to 3, the radius end mill 1 of the present embodiment has a shaft-shaped end mill main body 2 made of ceramic. Specifically, the end mill body 2 is made of sialon (SiAlON) of a ceramic material.
The end mill main body 2 has a substantially cylindrical shape, and a blade 3a is formed at least at the tip of the end mill main body 2 along the direction of the axis O, and the portion other than the blade 3a is a shank 3b.

The radius end mill 1 is a work material made of a metal material or the like by having a cylindrical shank portion 3b of the end mill main body 2 gripped by a main shaft or the like of a machine tool and rotating around an axis O in a tool rotation direction T. Used in the cutting process (milling process) of Further, along with the above-mentioned rotation, the sheet is fed in a direction intersecting the axis O, and shoulder cutting, grooving, rounding, copying, and the like are performed on the work material by the blade 3a.
The radius end mill 1 of the present embodiment is particularly suitable for cutting a heat-resistant alloy (hard-to-cut material) such as INCONEL (registered trademark) as a material to be cut.

  Further, when cutting the work material by the radius end mill 1, the coolant is jetted toward the blade portion 3a of the radius end mill 1 and the cutting surface (the portion to be processed) of the work material. It is preferable to use dry ice powder as this coolant.

[Definition of direction (direction) used in the present specification]
In the present specification, among the directions of the axis O of the end mill body 2, the direction from the shank 3b to the blade 3a is referred to as the tip end, and the direction from the blade 3a to the shank 3b is referred to as the proximal side.
Further, a direction orthogonal to the axis O is called a radial direction, among the radial directions, a direction approaching the axis O is called an inner side in the radial direction, and a direction separating from the axis O is called an outer side in the radial direction.
In addition, the direction around the axis O is called circumferential direction, and among the circumferential directions, the direction in which the end mill body 2 can be rotated during cutting is called the tool rotation direction T, and the direction opposite to this is the tool rotation direction It is called the opposite side to T.

[Chip discharge groove]
A plurality of chips discharge grooves 4 are formed on the outer periphery of the blade portion 3a at intervals in the circumferential direction. The chip discharge groove 4 is opened in the tip surface of the end mill body 2 and gradually twists and extends in the direction opposite to the tool rotational direction T as it goes from the tip surface to the proximal side. The chip discharge groove 4 is cut up to the outer periphery of the end mill main body 2 at the end on the proximal end side of the blade portion 3 a.

In the radius end mill 1 of the present embodiment, the four chip discharge grooves 4 are formed circumferentially at regular intervals (equal intervals or unequal intervals).
Each of the chip discharge grooves 4 has a wall surface facing the tool rotational direction T, and of the wall surface, a portion adjacent to the cutting edge is a rake surface. Specifically, among the rake surfaces of the cutting edge, portions of the cutting edge adjacent to the later-described outer peripheral blade 6, the bottom blade 9 and the corner blade 10 are respectively the rake surface 4a of the outer peripheral blade 6 and the bottom blade 9 The rake face 4 b and the rake face 4 c of the corner blade 10 are used.

A gash 7 is formed at the tip of the chip discharge groove 4 so that the tip is notched in the shape of a groove in the radial direction. Specifically, the gash 7 of the present embodiment is formed in the shape of a groove having a trapezoidal cross section extending along the radial direction at the tip of the chip discharge groove 4, and the radial inner end has the axis O Has reached.
In the present embodiment, four rows of gashes 7 are formed corresponding to the four rows of chip discharge grooves 4, and these gashes 7 are at the radially inner end (radial direction at the tip surface of the end mill body 2 Communicate with each other at the center of the axis, that is, on the axis O).

[Cutting edge]
The blade portion 3a has a plurality of cutting edges spaced in the circumferential direction. The cutting edges each have an outer peripheral edge 6, a corner edge 10 and a bottom edge 9, which form one L-shaped edge and are smoothly continuous.
The radius end mill 1 of the present embodiment has a blade portion 3 a of four blades (four cutting edges). However, the number of cutting edges of the radius end mill 1 (the number of sets of the L-shaped continuous outer peripheral blade 6, the corner blade 10 and the bottom blade 9) is not limited to the four-blades described in this embodiment. For example, three or less blades may be sufficient, or five or more blades may be sufficient. The number of cutting edges corresponds to the number of chip discharge grooves 4.

[Outer peripheral blade]
An outer peripheral blade 6 is formed on a cross ridge line between a wall surface of the chip discharge groove 4 facing the tool rotation direction T and the outer peripheral surface of the end mill body 2. The outer peripheral blade 6 extends in the form of a spiral (helical) along the outer peripheral edge of the wall surface of the chip discharge groove 4.

Specifically, among the wall surfaces of the chip discharge groove 4 facing the tool rotation direction T, the outer peripheral blade 6 discharges the chips among the outer surface of the rake surface 4a located at the radial outer end and the outer peripheral surface of the blade 3a. The groove 4 is formed at a crossing ridge line with the outer peripheral flank 5 adjacent to the side opposite to the tool rotation direction T.
On the outer peripheral surface of the blade portion 3a, an outer peripheral flank 5 is formed between the chip discharge grooves 4 adjacent to each other in the circumferential direction. The width (length in the direction orthogonal to the outer peripheral blade 6) of the outer peripheral flank 5 is substantially constant along the extending direction of the outer peripheral blade 6.

More specifically, the outer peripheral blades 6 of a number (4 lines) corresponding to the number (4 lines) of the chip discharge grooves 4 are formed in the blade portion 3a at intervals in the circumferential direction. The outer peripheral blade 6 has a lead equal to the chip discharge groove 4 and twists and extends gradually in the direction opposite to the tool rotational direction T as it goes from the tip of the end mill body 2 to the proximal end.
The rotation locus formed by rotating the outer peripheral blade 6 around the axis O is one cylindrical surface centered on the axis O.

  The radial rake angle (angle α) of the outer peripheral blade 6 is set to a negative angle in a cross-sectional view (a cross-sectional view perpendicular to the axis O of the end mill body 2) of the end mill body 2 shown in FIG. . Specifically, the radial rake angle of the outer peripheral blade 6 is -20 ° to -10 °. Preferably, the radial rake angle of the outer peripheral blade 6 is −17.5 ° to −12.5 °.

  Here, the “radial rake angle of the outer peripheral blade 6” referred to in the present specification means a predetermined radial direction perpendicular to the axis O passing through the outer peripheral blade 6 in the cross sectional view of the end mill main body 2 shown in FIG. Between the radial direction D (corresponding to the so-called “reference surface”) and the rake face 4 a of the outer peripheral blade 6 (the wall surface portion of the chips discharge groove 4 adjacent to the outer peripheral blade 6 facing the tool rotation direction T) Of the acute angles and the obtuse angles, the acute angle α is referred to.

Further, when the radial rake angle is "-(minus)", that is, a negative (negative) angle, the rake face 4a of the outer peripheral blade 6 in the radial direction in the cross-sectional view of the end mill body 2 shown in FIG. Is the angle α when extending obliquely to the opposite side to the tool rotation direction T as it goes outward. In this case, the rake surface 4 a of the outer peripheral blade 6 is disposed in the tool rotational direction T with respect to the predetermined radial direction D (reference surface).
Although not shown in particular, the rake face 4 a of the outer peripheral blade 6 in the cross-sectional view of the end mill body 2 indicates that the radial rake angle is “+ (plus)”, that is, a positive angle. It is an angle α when it extends obliquely toward the tool rotational direction T as it goes radially outward. In this case, the rake face 4 a of the outer peripheral blade 6 is disposed on the opposite side to the tool rotational direction T with respect to the predetermined radial direction D (reference plane).

In the present embodiment, at least the radial rake angle of the outer peripheral blade 6 among the outer peripheral blade 6, the bottom blade 9 and the corner blade 10 constituting the cutting edge is set to a negative angle, and the radial of the outer peripheral blade 6 The rake angle is taken as the above-mentioned numerical range.
In addition to the outer peripheral blade 6, any one or more radial rake angles of the bottom blade 9 and the corner blade 10 may be set to a negative angle.

  Further, in a side view of the end mill body 2 shown in FIG. 2 (a side view when the end mill body 2 is viewed from the radial direction orthogonal to the axis O), the twist angle (angle β) of the outer peripheral blade 6 is 30 ° to 40 °. It is. Preferably, the twist angle of the outer peripheral blade 6 is less than 39 °. More preferably, the twist angle of the outer peripheral blade 6 is 30 ° to 35 °.

  Here, the “twist angle” in the present specification means the axis O (or a straight line parallel to the axis O) and the outer peripheral blade 6 (a helical wire of a twist) in the side view of the end mill body 2 shown in FIG. Among the acute angles and obtuse angles formed between the two), the acute angle is referred to.

[Bottom blade (tip blade)]
As shown in FIGS. 1 to 3, a bottom blade (tip blade) 9 is formed at a crossing ridge line between the wall surface of the chip discharge groove 4 facing the tool rotation direction T and the tip surface of the end mill body 2. . The bottom blade 9 extends linearly along the leading edge of the wall surface of the chip discharge groove 4.

Specifically, of the wall surfaces of the chip discharge groove 4 (gash 7) facing the tool rotational direction T, the bottom blade 9 is a rake surface 4b located at the end on the tip side and the tip surface of the blade 3a It is formed in the cross ridge of the tip flank 8 adjacent to the side opposite to the tool rotation direction T of the chip discharge groove 4.
On the tip end face of the blade portion 3a, a tip end flank 8 is formed between the chip discharge grooves 4 adjacent to each other in the circumferential direction. The width (length in the direction orthogonal to the bottom blade 9) of the end flank 8 is substantially constant along the extending direction of the bottom blade 9.

More specifically, the number of bottom blades 9 (four rows) corresponding to the number (four rows) of the chip discharge grooves 4 is formed in the blade portion 3a at intervals in the circumferential direction.
In the present embodiment, in the front view of the end mill body 2 shown in FIG. 3 (when the tip surface of the end mill body 2 is viewed from the direction of the axis O in front), the bottom blade 9 extends along the radial direction, The inner end (radially inner end edge) of the bottom blade 9 is disposed radially outward of the axis O.

Further, in the side view of the end mill body 2 shown in FIG. 2, the bottom blade 9 extends gradually and slightly proximally in the radially inward direction from the outer end (radially outer end edge) thereof. . Therefore, the rotational trajectory formed by the rotation of the bottom blade 9 about the axis O is a conical surface (tapered surface) that gradually inclines toward the base end as it goes radially inward from the outer end of the bottom blade 9 Become.
The bottom blade 9 may extend to be included in a plane perpendicular to the axis O. In this case, the rotation trajectory of the bottom blade 9 is a plane perpendicular to the axis O.

As shown in FIG. 2, the rake angle of the bottom blade 9 (corresponding to approximately an axial rake angle) is set to a negative angle close to 0 ° or 0 °. That is, the rake surface 4b of the bottom blade 9 is gradually inclined toward the tool rotational direction T as it goes from the tip (bottom blade 9) to the proximal end side, or is formed parallel to the axis O There is.
The rake angle of the bottom blade 9 may be set to a positive angle. In this case, the rake surface 4b of the bottom blade 9 gradually inclines in the direction opposite to the tool rotational direction T as it goes from the tip to the proximal side.

[Corner blade]
As shown in FIGS. 1 to 3, a corner blade 10 is formed on a portion (corner portion) located on the outer periphery of the tip end of the end mill main body 2 in the wall surface of the chip discharge groove 4 facing the tool rotation direction T. ing. The corner blade 10 smoothly connects the outer end of the bottom blade 9 and the tip of the outer peripheral blade 6, and has a convex curved shape that is convex toward the tip outer peripheral side of the end mill main body 2.

Specifically, of the wall surfaces of the chip discharge groove 4 facing the tool rotational direction T, the corner blade 10 is a chip discharge groove 4 among the rake surface 4c located at the outer peripheral portion of the tip and the outer peripheral surface of the tip of the blade portion 3a. It is formed in the cross ridge line of the corner flank 11 adjacent to the opposite side to the tool rotation direction T of and.
The corner flank 11 smoothly connects the radially outer end of the tip flank 8 and the tip of the outer flank 5 and has a convex curved surface that is convex toward the tip outer circumference of the end mill body 2 ing.

  A corner flank 11 is formed between the chip discharge grooves 4 adjacent to each other in the circumferential direction on the tip outer peripheral surface of the blade 3a. The width (the length in the direction orthogonal to the corner blade 10) of the corner flank 11 is substantially constant along the extending direction of the corner blade 10.

More specifically, corner blades 10 of a number (4 lines) corresponding to the number (4 lines) of the chip discharge grooves 4 are formed in the blade portion 3a at intervals in the circumferential direction.
In the present embodiment, in a front view of the end mill body 2 shown in FIG. 3, the corner blade 10 has a convex curved shape that is convex outward in the tool rotational direction T and in the radial direction. Further, in a side view of the end mill body 2 shown in FIG. 2, the corner blade 10 (see the corner blade 10 disposed close to the axis O) is a convex curve which is convex toward the tool rotation direction T and the proximal end side. It has made a letter.

The rake angle of the corner blade 10 is set to a positive angle. That is, the rake face 4c of the corner blade 10 is gradually inclined toward the opposite side to the tool rotational direction T as it goes radially inward from the tip outer peripheral edge (corner blade 10) to the proximal end side.
The rake angle of the corner blade 10 may be set to a negative angle. In this case, the rake face 4c of the corner blade 10 gradually inclines in the tool rotational direction T as it extends radially inward from the tip outer peripheral edge toward the proximal end. Moreover, the rake angle of the corner blade 10 may be set to 0 °.

[Operation and effect according to the present embodiment]
According to the radius end mill 1 of the present embodiment described above, the end mill main body 2 is formed of ceramic. Further, among the outer peripheral blade 6, the bottom blade 9 and the corner blade 10, at least the radial rake angle (the outer peripheral rake angle, angle α in FIG. 4) of the outer peripheral blade 6 is set to a negative angle. The radial rake angle of the outer peripheral blade 6 is set to -20 ° to -10 °.

  For this reason, at the time of cutting, the cutting resistance of the outer peripheral blade 6 of the radius end mill 1 to the work material becomes large, and the cutting heat (heat generation due to plastic deformation in shear region, frictional heat, etc.) also becomes high accordingly.

When the cutting heat becomes high, the cutting surface (the portion to be processed) of the material to be cut is softened as compared to the peripheral edge 6 of the radius end mill 1 made of ceramic and having high heat resistance. That is, the hardness of the portion to be processed is significantly reduced with respect to the outer peripheral blade 6.
As a result, the outer peripheral blade 6 can cut at a high speed so as to scrape (scraping off) the work material. Further, since the hardness of the radius end mill 1 is relatively increased as compared with the softened work material, the wear (abrasion) of the outer peripheral blade 6 is remarkably suppressed, and the tool life is extended.

That is, the inventor of the present invention conducted intensive studies on the radius end mill 1 made of ceramic, and by setting the radial rake angle of the outer peripheral blade 6 in the above-mentioned numerical range, the cutting heat at the time of cutting is intentionally made. The cutting speed is dramatically increased by cutting the work material to soften the work material while maintaining the hardness of the radius end mill 1 and scraping the work material due to the difference in hardness. It came to gain the knowledge that it was possible.
That is, the cutting mode (processing form) by the radius end mill 1 of the present embodiment is significantly different from the cutting mode of the conventional general radius end mill.

Specifically, according to the radius end mill 1 of the present embodiment, when a heat-resistant alloy such as INCONEL (registered trademark) is cut as a material to be cut, a radius end mill (conventional product) made of general cemented carbide is used. In comparison, it was confirmed that 10 times or more processing efficiency can be realized.
Moreover, with the outer race blade 6 of the radius end mill 1 of the present embodiment, the radial rake angle is set to the above-mentioned numerical range, whereby the blade angle is sufficiently secured, and the edge strength is improved. Therefore, chipping or the like of the cutting edge is less likely to occur.

If the radial rake angle of the outer peripheral blade 6 is smaller than -20 °, that is, if it is larger on the negative angle side, the sharpness of the outer peripheral blade 6 is too low, and the cutting heat softens the cutting material. Even then, it will be difficult to increase the cutting speed.
In addition, when the radial rake angle of the outer peripheral blade 6 exceeds -10 °, the radial rake angle becomes too close to the regular angle side, and desired cutting heat can not be obtained. That is, since the cutting heat can not be sufficiently increased, the work material is not softened, and the above-described effects of the present embodiment can not be obtained, and the outer peripheral blade 6 may wear prematurely to reach the tool life. .
Therefore, the radial rake angle of the outer peripheral blade 6 in the present embodiment is -20 ° to -10 °.

  As described above, according to the present embodiment, although the end mill body 2 is formed of ceramic, the cutting speed can be increased to improve the processing efficiency while sufficiently securing the cutting edge strength and the wear resistance of the outer peripheral blade 6 Tool life can also be extended.

In addition, when the radial rake angle of the outer peripheral blade 6 is −17.5 ° to −12.5 °, the above-described effects according to the present embodiment can be obtained more reliably and stably.
In addition, when the radial rake angle of the outer peripheral blade 6 is set to -15 degrees, the most remarkable effect is produced.

  Further, in the present embodiment, since the twist angle (the angle β in FIG. 2) of the outer peripheral blade 6 is set to 30 ° to 40 °, the following effects can be obtained.

That is, generally, for example, in a radius end mill (conventional product) made of cemented carbide, the twist angle of the outer peripheral edge is set to be larger than 40 °. Thus, by setting the twist angle to a large positive angle, the outer peripheral blade is sharply cut into the work material, and the sharpness can be enhanced.
On the other hand, in the above-mentioned composition of this embodiment, the twist angle of perimeter blade 6 is set small as 30 degrees-40 degrees, and cutting resistance of perimeter blade 6 to a work material is intentionally raised. Thereby, at the time of cutting, the cutting resistance of the outer peripheral blade 6 of the radius end mill 1 with respect to the work material becomes large, and the cutting heat (heat generation due to plastic deformation in a shear region, frictional heat, etc.) also becomes high.

When the cutting heat becomes high, the cutting surface (the portion to be processed) of the material to be cut is softened as compared to the peripheral edge 6 of the radius end mill 1 made of ceramic and having high heat resistance. That is, the hardness of the portion to be processed is significantly reduced with respect to the outer peripheral blade 6.
As a result, the outer peripheral blade 6 can cut at a high speed so as to scrape (scraping off) the work material. Further, since the hardness of the radius end mill 1 is relatively increased as compared with the softened work material, the wear (abrasion) of the outer peripheral blade 6 is remarkably suppressed, and the tool life is extended.

  That is, according to the above configuration, the above-described effects of the present embodiment can be made particularly remarkable.

Specifically, by setting the twist angle of the outer peripheral blade 6 to be larger than 30 °, the outer peripheral blade 6 can secure a sufficient sharpness for scraping off the work material softened by the cutting heat. .
Further, by making the twist angle of the outer peripheral blade 6 smaller than 40 °, the cutting resistance of the outer peripheral blade 6 is increased to such an extent that sufficient cutting heat can be obtained to soften the work material. be able to.

  Further, in the present embodiment, since the end mill main body 2 is made of sialon which is a ceramic material, the end mill main body 2 is excellent in heat resistance, thermal shock resistance, mechanical strength in a high temperature environment, abrasion resistance and the like. Therefore, the above-described effects of the present embodiment become particularly remarkable, and are stably achieved.

  Further, in the present embodiment, dry ice powder is used as coolant supplied toward the blade portion 3a of the radius end mill 1 and the processing surface (the processed portion) of the work material at the time of cutting, as described above Even if the cutting heat is increased, the adhesion of the oxide film can be suppressed.

[Other Configurations Included in the Present Invention]
The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-mentioned embodiment, although sialon was used as a ceramic material of end mill main part 2, other ceramic materials may be used.

Although the twist angle of the outer peripheral blade 6 is 30 ° to 40 °, the reference example of the present invention is not limited to this. That is, according to the reference example of the present invention , the above-mentioned remarkable effects can be obtained when the radial rake angle of the outer peripheral blade 6 is a negative angle and -20 ° to -10 °. The twist angle of the blade 6 may be, for example, less than 30 ° or more than 40 °.
However, it is preferable for the twisting angle of the outer peripheral blade 6 to be in the range of 30 ° to 40 ° because the above-described remarkable effect is exerted. In addition, when the twist angle of the outer peripheral blade 6 is less than 39 °, the above-described effects can be obtained more stably, and more preferably, the twist angle of the outer peripheral blade 6 is 30 ° to 35 °. In addition, as it approaches 30 degrees among 30 degrees-35 degrees, cutting heat is heightened and a favorable result is easy to be obtained.

  In addition, without departing from the spirit of the present invention, each configuration (component) described in the above-described embodiment, modification, and note may be combined, and addition, omission, replacement, and other configurations can be made. Changes are possible. Moreover, this invention is not limited by embodiment mentioned above, It is limited only by the claim.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to this embodiment.

[Confirmation test of cutting length]
The radius end mill 1 of the embodiment described above was prepared as an example of the present invention. That is, in the radius end mill 1 of the embodiment, the end mill main body 2 is made of ceramic, and the radial rake angle (outer peripheral rake angle) α of the outer peripheral blade 6 is in the range of -20 ° to -10 °.

  Specifically, a radius end mill 1 in which the radial rake angle α of the outer peripheral blade 6 was set to -18 °, -15 °, -12 ° was prepared, and these were sequentially referred to as Examples 1 to 3. Also, although the end mill main body 2 is made of ceramic in common with the example, prepare a radius end mill with −23 ° and −7 ° in which the radial rake angle α of the outer peripheral blade 6 is out of the range of the present invention. These were made into comparative example 1 and 2 in order.

Then, continuous cutting of the work material is performed using these radius end mills, and the cutting length (total cutting length) until the peripheral blade 6 becomes uncut (tool life) due to chipping, wear, etc. is confirmed. The The cutting conditions were as follows.
Number of blades of radius end mill, size: 4 blades, φ10 mm × R1.25 mm
Work material: INCONEL (registered trademark) 718
Rotation speed: 20000 min ^-1
Cutting speed: 628 m / min
Feeding speed: 2000 mm / min
Feed per blade: 0.025 mm / tooth
Coolant: Dry Cutting method: Down cut Protrusion length: 23 mm
Cutting depth ae: 3.0 mm
Cutting depth ap: 7 . 5 mm

The results of the test are shown in the graph of FIG.
As shown in FIG. 5, in Examples 1 to 3 of the present invention, it was confirmed that the cutting length is sufficiently secured, the cutting process is stable, and the tool life is extended. In particular, in Example 2 in which the radial rake angle α of the outer peripheral blade 6 is in the range of −17.5 ° to −12.5 °, the cutting length reaches 35 m or more, and the effect is particularly remarkable. Was confirmed to play.

  On the other hand, in Comparative Examples 1 and 2, the cutting length was half or less compared to Examples 1 to 3. Specifically, in Comparative Example 1, it is considered that the cutting length was affected because the sharpness of the outer peripheral blade 6 was too low. Further, in Comparative Example 2, it is considered that the cutting edge strength of the outer peripheral blade 6 and the cutting heat at the time of cutting were not sufficiently obtained, and the cutting length was affected.

1 radius end mill 2 end mill main body 4 chip discharge groove 6 outer peripheral blade 9 bottom blade (tip blade)
10 corner blade O axis line T tool rotation direction α angle (radial rake angle of outer peripheral blade)
β angle (twist angle of outer peripheral blade)

Claims (4)

An end mill body made of a ceramic and made of ceramic,
A chip discharge groove which is formed on the outer periphery of the end mill body and extends gradually in the circumferential direction around the axial line from the tip along the axial direction of the end mill body toward the proximal end toward the opposite side to the tool rotation direction;
An outer peripheral blade formed at a cross ridge line between a wall surface of the chip discharge groove facing the tool rotation direction and an outer peripheral surface of the end mill main body;
A bottom blade formed at a cross ridge line between the wall surface of the chip discharge groove and the tip surface of the end mill body;
A corner blade located on the tip outer periphery of the end mill main body, connecting the outer end of the bottom blade to the tip of the outer peripheral blade, and having a convex curved shape convex toward the tip outer periphery of the end mill main body; Equipped
At least the radial rake angle of the outer peripheral blade among the outer peripheral blade, the base blade and the corner blade is set to a negative angle,
Radial rake angle of the peripheral blade, Ri -20 ° ~-10 ° der,
A radius end mill characterized in that a twist angle of the outer peripheral blade is 30 ° to 40 ° . The radius end mill according to claim 1, wherein
A radius end mill characterized in that a radial rake angle of the outer peripheral blade is -17.5 ° to -12.5 °.   A radius end mill according to claim 1 or 2, wherein
  A radius end mill characterized in that a twist angle of the outer peripheral blade is 30 ° to 35 °. The radius end mill according to any one of claims 1 to 3, wherein
The radius end mill, wherein the end mill body is made of sialon.

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