JP2016159379A - Radius end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radius end mill that has a higher cutting speed, improved machining efficiency and a prolonged tool lifetime while sufficiently securing cutting edge strength and wear resistance of an outer peripheral blade although an end mill body is formed of ceramic.SOLUTION: A radius end mill comprises: an end mill body 2 made of ceramic; an outer peripheral blade 6 formed at a ridge of intersection of a wall face, facing a tool rotating direction T, of a chip discharge groove 4 formed on an outer periphery of the end mill body 2 and an outer peripheral surface of the end mill body 2; a bottom blade formed at a ridge of intersection of the wall face of the chip discharge groove 4 and a front end face of the end mill body 2; and a corner blade connecting an outer end of the bottom blade and a tip end of the outer peripheral blade 6 and being in a convex curve shape convex to a tip end outer peripheral side of the end mill body 2. At least the outer peripheral blade 6 among the outer peripheral blade 6, bottom blade and corner blade has a radial rake angle (angle α) set to a negative angle, the radial rake angle of the outer peripheral blade 6 being -20° to -10°.SELECTED DRAWING: Figure 4

Description

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

Conventionally, for example, a radius end mill made of ceramic as shown in Patent Document 1 below is known. This radius end mill has an end mill body having an axial shape, and a chip discharge groove, an outer peripheral blade, a bottom blade (tip blade), and a corner blade are formed in the end mill body.
At the time of cutting, the radius end mill is cut in the work material by being fed in a direction intersecting the axis while being rotated in the tool rotation direction among the circumferential directions along the axis of the end mill body.

  Specifically, in the radius end mill, a plurality of chip discharge grooves extending from the distal end of the end mill main body toward the base end side are formed on the outer periphery of the end mill main body at intervals in the circumferential direction. Moreover, the outer peripheral blade is formed in the intersection ridgeline of the wall surface which faces a tool rotation direction in a chip discharge groove, and the outer peripheral surface of an end mill main body. Moreover, the bottom blade is formed in the intersection ridgeline of the said wall surface of a chip discharge groove | channel, and the front end surface of an end mill main body. In addition, a corner blade having a convex curve shape is formed on the outer peripheral portion (corner portion) of the wall surface of the chip discharge groove by connecting the outer end (radially outer edge) of the bottom blade and the tip of the outer peripheral blade. Has been.

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

  On the other hand, in the radial 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 blade edge strength is ensured.

US Pat. No. 8,647,025

  However, in the radius end mill of Patent Document 1, the outer peripheral edge was worn (worn) at an early stage, and the tool life was short. In order to suppress such wear of the outer peripheral blade, it is preferable to reduce the cutting resistance during processing. That is, as described above, a countermeasure for increasing the sharpness by increasing the radial rake angle of the outer peripheral blade to the positive angle side can be considered.

However, since the radial 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 blade edge strength cannot be ensured.
Further, for this type of radius end mill, it has been required to increase the cutting speed and improve the processing efficiency.

  The present invention has been made in view of such circumstances, and while the end mill body is formed of ceramic, the cutting edge speed of the outer peripheral blade and the wear resistance are sufficiently secured, and the cutting speed is increased to perform processing. An object of the present invention is to provide a radius end mill that can improve efficiency and extend 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 of the present invention has a shaft-like end mill body formed of ceramic, and is formed on the outer periphery of the end mill body, and gradually moves around the axis line from the distal end along the axial direction of the end mill body toward the proximal end side. The outer periphery formed in the intersection ridgeline of the chip discharge groove extended toward the opposite side to a tool rotation direction among the circumferential directions of the above, the wall surface facing the tool rotation direction in the chip discharge groove, and the outer peripheral surface of the end mill body A blade, a bottom blade formed on a crossed ridge line of the wall surface in the chip discharge groove, and a tip surface of the end mill body; and an outer end of the bottom blade and the outer edge of the end mill body, A corner blade that forms a convex curve shape that connects the tips of the outer peripheral blades and protrudes toward the outer peripheral side of the tip end of the end mill body, the outer peripheral blade, the bottom blade, and the 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 cutting edge is characterized by a -20 ° ~-10 °.

  In the radius end mill of the present invention, the end mill body is made of ceramic. The radial rake angle (outer rake angle) of at least the outer peripheral edge of the outer peripheral edge, the bottom edge and the corner edge is set to a negative angle. Specifically, the radial rake angle of the outer peripheral edge is −20. The angle is set to ° to -10 °.

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

Moreover, the radial rake angle is “− (minus)”, that is, a negative (negative) angle means that the rake face 4a of the outer peripheral blade 6 is in the radial direction in the cross-sectional view of the end mill body 2 shown in FIG. Is the angle α when extending toward the opposite side of the tool rotation direction T as it goes outward. In this case, the rake face 4a of the outer peripheral blade 6 is arranged in the tool rotation direction T with respect to the predetermined radial direction D (reference plane).
In addition, although not specifically illustrated, the radial rake angle is “+ (plus)”, that is, a positive (positive) angle, the rake face 4a of the outer peripheral blade 6 in the cross-sectional view of the end mill body 2 is This is the angle α when extending toward the tool rotation direction T as it goes outward in the radial direction. In this case, the rake face 4a of the outer peripheral blade 6 is disposed on the opposite side to the tool rotation direction T with respect to the predetermined radial direction D (reference plane).

  In the present invention, the radial rake angle (the 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 with respect to the work material increases, and accordingly, the cutting heat (heat generation or frictional heat due to plastic deformation in the shear region) also increases.

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

That is, the inventor of the present invention, as a result of earnest research on a radius end mill made of ceramic, by setting the radial rake angle of the outer peripheral edge in the above numerical range, intentionally increasing the cutting heat during cutting, As a result, it is possible to drastically increase the cutting speed by softening the work material while maintaining the hardness of the radius end mill and cutting so that the work material is scraped off due to the difference in hardness. It came to gain knowledge.
That is, the cutting mode (machining 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 work material, compared to a radius end mill (conventional product) made of a general cemented carbide. It was confirmed that a machining efficiency of 10 times or more can be realized.
Moreover, since the radial rake angle of the outer peripheral edge of the radius end mill of the present invention is within the above numerical range, the blade angle is sufficiently secured and the blade edge strength is improved. Therefore, chipping of the blade edge is less likely to occur.

In addition, when the radial rake angle of the outer peripheral blade is smaller than −20 °, that is, when it is larger on the negative angle side, the sharpness of the outer peripheral blade is deteriorated too much, and the work material is softened by the cutting heat. However, 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 positive angle side, and the desired cutting heat cannot be obtained. That is, since the cutting heat cannot be sufficiently increased, the work material is not softened, and the above-described operation and effect of the present invention cannot be obtained.
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, while the end mill body is formed of ceramic, it is possible to increase the cutting speed and improve the processing efficiency while sufficiently securing the edge strength and wear resistance of the outer peripheral blade, and the tool life is also improved. It can be extended.

  In the radius end mill of the present invention, it is preferable that a radial rake angle of the outer peripheral blade is -17.5 ° to -12.5 °.

  In this case, the above-described operational effects of the present invention can be obtained more reliably and stably. The most remarkable effect is obtained when the radial rake angle of the outer peripheral blade is set to -15 °.

  In the radius end mill of the present invention, it is preferable that a twist angle of the outer peripheral blade is 30 ° to 40 °.

According to the above configuration of the present invention, the twist angle of the outer peripheral blade is set to 30 ° to 40 °.
Here, the “twist angle” referred to in the present specification refers to the axis O (or the side view of the end mill main body 2 shown in FIG. 2 (the side view when the end mill main body 2 is viewed from the radial direction orthogonal to the axis O). Among acute angles and obtuse angles formed between the straight line parallel to the axis O) and the outer peripheral edge 6 (twisted helical winding), it indicates an acute angle β.

In general, in a radius end mill (conventional product) made of a cemented carbide, for example, the twist angle of the outer peripheral blade is set to be larger than 40 °. This is because, when the twist angle is set to a large positive angle, the outer peripheral edge cuts sharply into the work material, and the sharpness is enhanced.
On the other hand, in the said structure of this invention, the torsion angle of an outer peripheral blade is set small as 30 degrees-40 degrees, and the cutting resistance of the outer peripheral blade with respect to a workpiece is increased intentionally. Thereby, at the time of cutting, the cutting resistance of the outer peripheral edge of the radius end mill with respect to the work material increases, and the cutting heat (heat generation or frictional heat due to plastic deformation in the shear region) also increases.

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

  That is, according to the above configuration, the above-described operational effects of the present invention can be made even more remarkable.

Specifically, by making the twist angle of the outer peripheral blade larger than 30 °, the outer peripheral blade can ensure a sharpness enough to scrape off the work material softened by the cutting heat.
In addition, since the twist angle of the outer peripheral blade is smaller than 40 °, the cutting resistance of the outer peripheral blade can be increased to the extent that sufficient cutting heat can be obtained to soften the work material. it can.

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

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

  According to the radius end mill of the present invention, while the end mill body is formed of ceramic, the cutting edge speed and wear resistance of the outer peripheral blade can be sufficiently secured, the cutting speed can be increased and the machining efficiency can be improved, and the tool life can be improved. Can be extended.

It is a perspective view which shows the radius end mill which concerns on one Embodiment of this 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 an outer 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 body]
As shown in FIG. 1 to FIG. 3, the radius end mill 1 of the present embodiment has a shaft shape and has an end mill body 2 made of ceramic. Specifically, the end mill body 2 is made of ceramic material sialon (SiAlON).
The end mill main body 2 has a substantially columnar shape, and a blade portion 3a is formed at least at a tip portion along the axis O direction of the end mill main body 2, and a portion other than the blade portion 3a is a shank portion 3b.

The radius end mill 1 has a cylindrical shank portion 3b in the end mill body 2 that is gripped by a spindle of a machine tool or the like, and is rotated in the tool rotation direction T around the axis O, so that a work material made of a metal material or the like is obtained. Used for cutting (rolling). Further, along with the rotation, a feed is given in a direction intersecting the axis O, and shoulder cutting, grooving, R cutting, copying, and the like are performed on the workpiece by the blade portion 3a.
The radius end mill 1 of this embodiment is particularly suitable for cutting a heat-resistant alloy (hard-to-cut material) such as INCONEL (registered trademark) as a work material.

  Further, when the workpiece is cut by the radius end mill 1, coolant is jetted toward the blade portion 3 a of the radius end mill 1 and the cutting surface (worked portion) of the workpiece. As this coolant, it is preferable to use dry ice powder.

[Definition of direction (direction) used in this specification]
In the present specification, in the direction of the axis O of the end mill body 2, the direction from the shank portion 3b to the blade portion 3a is referred to as the distal end side, and the direction from the blade portion 3a to the shank portion 3b is referred to as the proximal end side.
In addition, a direction perpendicular to the axis O is referred to as a radial direction, and a direction approaching the axis O in the radial direction is referred to as a radial inner side, and a direction away from the axis O is referred to as a radial outer side.
Further, the direction that circulates around the axis O is referred to as the circumferential direction. Of the circumferential directions, the direction in which the end mill body 2 is rotated at the time of cutting is referred to as the tool rotation direction T, and the opposite direction is the tool rotation direction. It is called the opposite side of T.

[Chip discharge groove]
On the outer periphery of the blade portion 3a, a plurality of chip discharge grooves 4 are formed at intervals in the circumferential direction. The chip discharge groove 4 opens at the distal end surface of the end mill body 2 and gradually twists and extends toward the side opposite to the tool rotation direction T from the distal end surface toward the proximal end side. The chip discharge groove 4 is rounded up to the outer periphery of the end mill main body 2 at the end portion on the proximal end side of the blade portion 3a.

In the radius end mill 1 of the present embodiment, the four chip discharge grooves 4 are formed at intervals (equal intervals or unequal intervals) in the circumferential direction.
Each chip discharge groove 4 has a wall surface facing the tool rotation direction T, and a portion of the wall surface adjacent to the cutting edge is a rake surface. Specifically, of the rake face of the cutting edge, the portions adjacent to the outer peripheral edge 6, the bottom edge 9, and the corner edge 10, which will be described later, of the cutting edge are the rake face 4 a of the outer peripheral edge 6, The rake face 4b and the rake face 4c 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 cut out in a groove shape in the radial direction. Specifically, the gash 7 of the present embodiment is formed in a trapezoidal groove shape extending along the radial direction at the distal end portion of the chip discharge groove 4, and the radially inner end thereof is on the axis O. Has reached.
In the present embodiment, four gashes 7 are formed corresponding to the four chip discharge grooves 4, and these gashes 7 are radially inwardly end portions (radial direction on the distal end surface of the end mill body 2). In the middle of each other, that is, on the axis O).

[Cutting edge]
The blade part 3a has a plurality of cutting edges at intervals in the circumferential direction. Each of the cutting edges has an outer peripheral edge 6, a corner edge 10 and a bottom edge 9, which form one L-shaped cutting edge and are smoothly continuous.
The radius end mill 1 of the present embodiment has a blade portion 3a having four blades (four cutting blades). However, the number of cutting edges of the radius end mill 1 (the number of sets of outer peripheral blades 6, corner blades 10, and bottom blades 9 that are continuous in an L shape) is not limited to the four blades described in the present embodiment. For example, it may be 3 blades or less, or 5 blades or more. The number of cutting edges corresponds to the number of chip discharge grooves 4.

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

Specifically, the outer peripheral blade 6 includes the rake face 4a located at the radially outer end of the wall surface facing the tool rotation direction T of the chip discharge groove 4 and the chip discharge out of the outer peripheral surface of the blade part 3a. The groove 4 is formed at an intersecting ridge line with the outer peripheral flank 5 adjacent to the opposite side to the tool rotation direction T of the groove 4.
On the outer peripheral surface of the blade portion 3a, outer peripheral flank surfaces 5 are formed between the chip discharge grooves 4 adjacent in the circumferential direction. The width of the outer peripheral flank 5 (the length in the direction perpendicular to the outer peripheral blade 6) is substantially constant along the extending direction of the outer peripheral blade 6.

Specifically, a number (four) of outer peripheral blades 6 corresponding to the number of the chip discharge grooves 4 (four) are formed in the blade portion 3a at intervals in the circumferential direction. The outer peripheral blade 6 is a lead equal to the chip discharge groove 4 and gradually twists and extends toward the side opposite to the tool rotation direction T from the distal end of the end mill body 2 toward the proximal end.
A rotation locus formed by rotating the outer peripheral blade 6 around the axis O is a single cylindrical surface centered on the axis O.

  And in the cross sectional view of the end mill main body 2 shown in FIG. 4 (the cross sectional view perpendicular to the axis O of the end mill main body 2), the radial rake angle (angle α) of the outer peripheral blade 6 is set to a negative angle. . 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 is a predetermined value passing through the outer peripheral blade 6 in the radial direction orthogonal to the axis O in the cross-sectional view of the end mill body 2 shown in FIG. Between the radial direction D (corresponding to a so-called “reference surface”) and the rake face 4a of the outer peripheral blade 6 (the wall surface portion facing the tool rotation direction T of the chip discharge groove 4 adjacent to the outer peripheral blade 6). Among the acute angles and obtuse angles to be made, it indicates the acute angle α.

Moreover, the radial rake angle is “− (minus)”, that is, a negative (negative) angle means that the rake face 4a of the outer peripheral blade 6 is in the radial direction in the cross-sectional view of the end mill body 2 shown in FIG. Is the angle α when extending toward the opposite side of the tool rotation direction T as it goes outward. In this case, the rake face 4a of the outer peripheral blade 6 is arranged in the tool rotation direction T with respect to the predetermined radial direction D (reference plane).
In addition, although not specifically illustrated, the radial rake angle is “+ (plus)”, that is, a positive (positive) angle, the rake face 4a of the outer peripheral blade 6 in the cross-sectional view of the end mill body 2 is This is the angle α when extending toward the tool rotation direction T as it goes outward in the radial direction. In this case, the rake face 4a of the outer peripheral blade 6 is disposed on the opposite side to the tool rotation direction T with respect to the predetermined radial direction D (reference plane).

In the present embodiment, the radial rake angle of at least 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 blade 6 has a radial rake angle. The rake angle is in the numerical range described above.
In addition to the outer peripheral blade 6, 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 the side view of the end mill body 2 shown in FIG. 2 (side view when the end mill body 2 is viewed from the radial direction perpendicular to the axis O), the torsion 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 desirably, the twist angle of the outer peripheral blade 6 is 30 ° to 35 °.

  Here, the “twist angle” in the present specification refers to the axis O (or a straight line parallel to the axis O) and the outer peripheral blade 6 (twisted spiral winding) in the side view of the end mill body 2 shown in FIG. ) Between the acute angle and the obtuse angle formed between the first and second angles).

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

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

Specifically, a number (four items) of bottom blades 9 corresponding to the number of chip discharge grooves 4 (four items) 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 (when the front end surface of the end mill body 2 is viewed from the axis O direction to the front), the bottom blade 9 extends along the radial direction, The inner end (the inner edge in the radial direction) of the bottom blade 9 is arranged on the outer side in the radial direction with respect to the axis O.

Moreover, in the side view of the end mill main body 2 shown in FIG. 2, the bottom blade 9 gradually extends toward the proximal end side gradually from the outer end (radially outer edge) toward the radially inner side. . Therefore, the rotation locus formed by the bottom blade 9 rotating around the axis O is a conical surface (tapered surface) that gradually inclines toward the base end side from the outer end of the bottom blade 9 toward the radially inner side. Become.
The bottom blade 9 may extend so as to be included in a plane perpendicular to the axis O. In this case, the rotation locus 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 (substantially equivalent to the axial rake angle) is set to a negative angle close to 0 °, or 0 °. That is, the rake face 4b of the bottom blade 9 is formed so as to be gradually inclined toward the tool rotation direction T from the tip (bottom blade 9) toward the base end side, or to be parallel to the axis O. Yes.
In addition, the rake angle of the bottom blade 9 may be set to a positive angle. In this case, the rake face 4b of the bottom blade 9 is gradually inclined toward the side opposite to the tool rotation direction T as it goes from the distal end to the proximal end 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 peripheral portion of the end mill body 2 on the wall surface facing the tool rotation direction T in the chip discharge groove 4. 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 curve shape that protrudes toward the outer periphery of the end of the end mill body 2.

Specifically, the corner blade 10 has a chip discharge groove 4 out of a rake face 4c positioned at the outer peripheral portion of the tip of the wall surface facing the tool rotation direction T of the chip discharge groove 4 and an outer peripheral surface of the tip of the blade portion 3a. Are formed on the intersecting ridge line with the corner flank 11 adjacent to the opposite side to the tool rotation direction T.
The corner flank 11 smoothly connects the radially outer end of the tip flank 8 and the tip of the outer peripheral flank 5, and has a convex curved surface that protrudes toward the outer periphery of the end of the end mill body 2. ing.

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

Specifically, a number (four items) of corner blades 10 corresponding to the number (four items) of the chip discharge grooves 4 are formed in the blade portion 3a at intervals in the circumferential direction.
In the present embodiment, when the end mill body 2 shown in FIG. 3 is viewed from the front, the corner blade 10 has a convex curve shape that is convex toward the tool rotation direction T and radially outward. Further, in the side view of the end mill main 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 that is convex toward the tool rotation direction T and toward the base end side. It has a shape.

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 side opposite to the tool rotation direction T as it goes radially inward and proximally from the outer peripheral edge (corner blade 10).
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 rotation direction T as it goes radially inward and proximally from the outer peripheral edge of the tip. Further, the rake angle of the corner blade 10 may be set to 0 °.

[Effects of this embodiment]
According to the radius end mill 1 of the present embodiment described above, the end mill body 2 is formed of ceramic. The radial rake angle (outer rake angle, angle α in FIG. 4) of at least the outer peripheral blade 6 among the outer peripheral blade 6, the bottom blade 9 and the corner blade 10 is set to a negative angle, specifically, 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 edge 6 of the radius end mill 1 with respect to the work material increases, and accordingly, the cutting heat (heat generation, frictional heat, etc. due to plastic deformation in the shear region) increases.

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

That is, the inventor of the present invention has intensively studied the radial end mill 1 made of ceramic. As a result, the radial rake angle of the outer peripheral blade 6 is set within the above numerical range, thereby intentionally reducing the cutting heat during the cutting process. This increases the cutting speed by softening the work material while maintaining the hardness of the radius end mill 1 and cutting the work material to scrape off the work material due to the difference in hardness. It came to obtain the knowledge that it was possible.
That is, the cutting mode (machining mode) by the radius end mill 1 of the present embodiment is greatly 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 work material, for example, a radius end mill (conventional product) made of a general cemented carbide is used. In comparison, it was confirmed that a machining efficiency of 10 times or more can be realized.
Moreover, since the radial rake angle of the outer peripheral blade 6 of the radius end mill 1 of the present embodiment is in the above numerical range, the blade angle is sufficiently ensured and the blade edge strength is improved. Therefore, chipping of the blade edge is less likely to occur.

In addition, when the radial rake angle of the outer peripheral blade 6 is smaller than −20 °, that is, when it is larger on the negative angle side, the sharpness of the outer peripheral blade 6 is deteriorated too much, and the work material is softened by the cutting heat. Even so, it becomes difficult to increase the cutting speed.
Further, when the radial rake angle of the outer peripheral edge 6 exceeds -10 °, the radial rake angle becomes too close to the positive angle side, and the desired cutting heat cannot be obtained. That is, since the cutting heat cannot be sufficiently increased, the work material is not softened, and the above-described operation and effect of the present embodiment cannot be obtained. Further, the outer peripheral blade 6 may be worn early and reach the tool life. .
Therefore, in this embodiment, the radial rake angle of the outer peripheral blade 6 is −20 ° to −10 °.

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

Further, when the radial rake angle of the outer peripheral blade 6 is -17.5 ° to -12.5 °, the above-described operational 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 °, the most remarkable effect is obtained.

  Moreover, in this embodiment, since the twist angle (angle (beta) in FIG. 2) of the outer periphery blade 6 is 30 degrees-40 degrees, there exist the following effects.

That is, generally, for example, in a radius end mill (conventional product) made of a cemented carbide, the twist angle of the outer peripheral blade is set to be larger than 40 °. This is because, when the twist angle is set to a large positive angle, the outer peripheral edge cuts sharply into the work material, and the sharpness is enhanced.
On the other hand, in the above-described configuration of the present embodiment, the twisting angle of the outer peripheral blade 6 is set as small as 30 ° to 40 ° to intentionally increase the cutting resistance of the outer peripheral blade 6 with respect to the work material. 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 increases, and the cutting heat (heat generation, frictional heat, etc. due to plastic deformation in the shear region) also increases.

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

  That is, according to the said structure, the effect mentioned above of this embodiment can be made further remarkable.

Specifically, since the twist angle of the outer peripheral blade 6 is larger than 30 °, the outer peripheral blade 6 can ensure a sharpness enough to scrape off the work material softened by the cutting heat. .
In addition, since the twist angle of the outer peripheral blade 6 is smaller than 40 °, the cutting resistance of the outer peripheral blade 6 is increased to the extent that sufficient cutting heat can be obtained to soften the work material. be able to.

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

  Moreover, in this embodiment, since dry ice powder is used as a coolant supplied toward the blade part 3a of the radius end mill 1 and the processing surface (working part) of the workpiece during cutting, as described above. Even if the cutting heat is increased, adhesion of the oxide film can be suppressed.

[Other configurations included in the present invention]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, sialon is used as the ceramic material of the end mill body 2, but other ceramic materials may be used.

Moreover, although the torsion angle of the outer peripheral blade 6 is 30 ° to 40 °, it is not limited to this. That is, according to the present invention, since the radial rake angle of the outer peripheral blade 6 is a negative angle and −20 ° to −10 °, the above-described remarkable effects can be obtained. For example, it may be smaller than 30 ° or larger than 40 °.
However, it is preferable that the torsion angle of the outer peripheral blade 6 is in the range of 30 ° to 40 ° because the above-described particularly remarkable effects are exhibited. Further, when the twist angle of the outer peripheral blade 6 is less than 39 °, the above-described effects can be obtained more stably. More preferably, the twist angle of the outer peripheral blade 6 is 30 ° to 35 °. In addition, among 30 degrees-35 degrees, cutting heat is raised as it approaches 30 degrees, and a favorable result is easy to be obtained.

  In addition, in the range which does not deviate from the meaning of this invention, you may combine each structure (component) demonstrated by the above-mentioned embodiment, a modification, and a remark etc., addition of a structure, omission, substitution, others It can be changed. Further, the present invention is not limited by the above-described embodiments, and is limited only by the scope of the claims.

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

[Cutting length confirmation test]
As an example of the present invention, the radius end mill 1 of the above-described embodiment was prepared. That is, in the radius end mill 1 of the embodiment, the end mill body 2 is made of ceramic, and the radial rake angle (outer 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 edge 6 was set to −18 °, −15 °, and −12 ° was prepared, and these were sequentially set as Examples 1 to 3. Also, although the end mill body 2 is made of ceramic, it is the same as the embodiment, but a radius end mill is prepared in which the radial rake angle α of the outer peripheral edge 6 is outside the scope of the present invention and is set to −23 ° and −7 °. These were designated as Comparative Examples 1 and 2, respectively.

Then, continuous cutting of the work material is performed using these radius end mills, and the cutting length (total cutting length) until the outer peripheral blade 6 becomes incapable of cutting (tool life) due to chipping or wear of the cutting edge is confirmed. It was. In addition, about cutting conditions etc., it was as follows.
Number of radius end mill blades, size: 4 blades, φ10mm x R1.25mm
Work material: INCONEL (registered trademark) 718
Rotational speed: 20000 min ^-1
Cutting speed: 628 m / min
Feeding speed: 2000mm / min
Feed per tooth: 0.025mm / tooth
Coolant: Dry Cutting method: Down cut Protrusion length: 23 mm
Cutting depth ae: 3.0 mm
Cutting depth ap: 75mm

The result of the test is 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 was sufficiently secured, the cutting process was stabilized, and the tool life was extended. In particular, in Example 2 in which the radial rake angle α of the outer peripheral edge 6 is within the range of −17.5 ° to −12.5 °, the cutting length has reached 35 m or more, and a more remarkable effect. It was confirmed that

  On the other hand, in Comparative Examples 1 and 2, the cutting length was half or less compared to Examples 1-3. Specifically, in Comparative Example 1, it is considered that the cutting length was affected because the sharpness of the outer peripheral edge 6 was excessively lowered. 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.

DESCRIPTION OF SYMBOLS 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 T Tool rotation direction α angle (radial rake angle of outer peripheral blade)
β angle (Torsion angle of outer peripheral edge)

Claims (4)

A shaft-shaped end mill body made of ceramic,
A chip discharge groove formed on the outer periphery of the end mill body, and gradually extending toward the opposite side of the tool rotation direction in the circumferential direction around the axis line from the distal end along the axial direction of the end mill body toward the base end side;
An outer peripheral blade formed on a cross ridge line between a wall surface facing the tool rotation direction in the chip discharge groove and an outer peripheral surface of the end mill body;
A bottom blade formed at a crossing ridge line between the wall surface of the chip discharge groove and a tip surface of the end mill body;
A corner blade that is located on the outer peripheral portion of the end mill body and connects the outer end of the bottom blade and the tip of the outer peripheral blade and has a convex curve shape that protrudes toward the outer peripheral side of the end mill body; Prepared,
Of the outer peripheral blade, the bottom blade and the corner blade, at least the radial rake angle of the outer peripheral blade is set to a negative angle,
A radial end mill having a radial rake angle of the outer peripheral edge of -20 ° to -10 °. A radius end mill according to claim 1,
A radial end mill having a radial rake angle of the outer peripheral blade of -17.5 ° to -12.5 °. A radius end mill according to claim 1 or 2,
A radius end mill, wherein the outer peripheral blade has a twist angle of 30 ° to 40 °. It is a radius end mill as described in any one of Claims 1-3,
A radius end mill, wherein the end mill body is made of sialon.

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