JP6435801B2 - End mill - Google Patents

Description

  The present invention relates to a small-diameter end mill used for machining precision molds and the like.

  The end mill has a cutting edge composed of a bottom blade formed at the tip and an outer peripheral blade formed at the outer peripheral portion, and is used for finishing the bottom surface of the work material and machining the inclined portion. Is done. In particular, as an end mill for finishing, a small-diameter end mill having a small outer diameter is used. In such a small-diameter end mill, a cBN sintered body, a diamond sintered body (PCD), or the like is used to process a material with high hardness. It is formed. A grindstone or the like is used for forming these forms, but a cBN sintered body, PCD, and the like have extremely high hardness and excellent wear resistance, but have a side face that is brittle to impact. For this reason, chipping is likely to occur in the conventional grinding process, and the yield is very poor. Therefore, for some time, the shape of the rake face has been adjusted to facilitate the formation of the form, and the end mill has been improved in chipping resistance and the like.

  For example, in Patent Document 1, by grinding a pair of torsion grooves on the outer peripheral surface, a pair of outer peripheral blades are provided along the torsion grooves, and a gash is ground at an axial tip portion of the torsion grooves. Thus, an end mill (square end mill) in which a straight bottom blade is provided continuously to the outer peripheral blade is disclosed. Further, in Patent Document 1, by using a twisted outer peripheral blade, the edge angle of the corner portion at the tip in the axial direction of the outer peripheral blade can be increased and the blade edge strength can be increased, so that the chipping of the blade can be suppressed. Have been described. However, this CBN end mill has a structure in which the bottom edge and the outer peripheral edge are formed by different rake faces of the gash and the twisted groove, and stress tends to concentrate on the boundary between the gash and the twisted groove. Therefore, the problem is that defects are likely to occur starting from that portion.

  Therefore, Patent Document 2 proposes a radius end mill that has a twisted outer peripheral cutting edge, is formed with only 60% outer peripheral cutting edge by gash, and a rake face is constituted by a certain inclined surface. In this way, stress concentration can be avoided by forming the rake face with a certain inclined surface without forming a boundary portion.

JP 2008-110411 A JP 2010-125594 A

Like the end mill described in Patent Literature 1 or Patent Literature 2, by forming the outer peripheral blade having a twist, the edge angle of the corner portion at the tip in the axial direction of the outer peripheral blade can be increased to increase the strength of the blade edge. . Moreover, since the cutting resistance can be reduced as the helix angle of the outer peripheral blade is increased, it is easier to avoid the occurrence of defects. However, on the other hand, the surface roughness of the processed surface is increased compared to the case where the outer peripheral blade is formed by a straight blade, leading to a reduction in finishing processing accuracy.
In addition, a small-diameter end mill formed of a brittle material with high hardness such as a cBN sintered body or PCD requires a strong mechanical load during grinding when forming the cutting edge of the end mill itself. Therefore, it is difficult to perform the processing described in Patent Document 1 or Patent Document 2, and it is difficult to form a complicated shape.

  The present invention has been made in view of such circumstances, and provides a small-diameter end mill capable of improving the fracture resistance and wear resistance of the tool itself and improving the finishing accuracy of the work material. The purpose is to do.

The end mill of the present invention comprises a cBN sintered body or a diamond sintered body, and an outer periphery disposed on the outer periphery of the tool tip at a tool tip having a diameter of 0.1 mm or more and 6.0 mm or less arranged around the axis. The blade includes at least a pair of cutting blades including a blade and a bottom blade disposed at the tip of the tool tip, and an angle between the axial direction of the rake face of the outer peripheral blade is continuous from the tip end side to the rear end side of the shaft. As for the surface roughness Rz of the rake face, the outer range of 1/50 of the diameter from the outer peripheral edge is less than 0.05 μm, and the inner range inside the rake face is 0. 05μm more than 0.08μm Ru is the following.

The end mill has different cutting edge strengths required on the front end side and the rear end side of the cutting blade shaft depending on the cutting conditions such as the blade diameter, rotation speed, and feed rate.
In this regard, in the end mill of the present invention, the angle of the rake face forming the outer peripheral blade (the twist angle) with the axial direction is continuously changed from the front end side to the rear end side of the shaft, thereby A cutting blade adapted to the cutting conditions can be formed from the front end side to the rear end side, and the necessary cutting edge strength and the finishing accuracy of the work material can be ensured at each position.
By continuously changing the angle of the rake face of the outer peripheral edge with the axial direction, a rake face that is smoothly connected from the bottom edge to the outer peripheral edge can be formed. It is possible to further improve the chipping resistance and wear resistance of itself.
In addition, the surface roughness of the rake face forming the cutting edge affects the surface roughness of the finished surface of the work material, and thus a smooth surface with a surface roughness Rz (maximum height) of 0.1 μm or less. It is desirable to form with. In this respect, in the end mill of the present invention, the surface roughness Rz of the rake face is a smooth surface with an outer range of 1/50 the diameter (about twice the recommended cutting depth) from the outer peripheral edge and less than 0.05 μm. By forming with, a cutting edge can be formed with a sharp ridgeline. Further, in the inner range inside the outer range, the surface roughness Rz is formed in a range of 0.05 μm or more and 0.08 μm or less, and the surface roughness is reduced from the inner side to the outer side. Then, it is possible to reduce the heat generation by reducing the contact area of the cutting waste, and it is possible to increase the heat dissipation and prevent the welding of the cutting waste, thereby improving the tool life. Furthermore, even if it is a rake face formed with a slight inclination angle, the cutting waste can be smoothly discharged by the smooth face, so that a cutting edge with high machinability can be configured.

In the end mill of the present invention, the angle of the rake face with respect to the axial direction is set smaller on the rear end side than on the front end side of the shaft.
Increasing the angle between the rake face of the outer peripheral edge and the axial direction increases the contact area between the outer peripheral edge and the work material. Emission is also increased. For this reason, by increasing the angle of the rake face with the axial direction on the tip end side of the shaft, the contact area can be increased and the biting of the outer peripheral blade to the work material can be improved. The finishing accuracy can be improved by reducing the resistance.
On the other hand, if the angle with the axial direction of the rake face is excessively increased on the rear end side of the shaft, waviness tends to occur on the finished surface on the rear end side of the shaft, and the angle with the axial direction of the rake face is reduced. It is desirable to do. However, if the angle of the rake face with respect to the axial direction is too small, the cutting resistance is increased and the cutting waste is reduced, so that tool chatter and chipping are likely to occur.
Therefore, by providing the angle of the rake face with the axial direction so as to be smaller on the rear end side than on the front end side of the shaft, resistance is obtained at each position from the front end side to the rear end side of the shaft. The chipping and wear resistance can be improved, and the finishing accuracy of the work material can be improved.

  According to the present invention, by continuously changing the angle of the rake face of the outer peripheral blade from the axial direction from the front end side to the rear end side of the shaft, the necessary edge strength and finishing of the work material are required at each position. Machining accuracy can be ensured, and it is possible to improve the fracture resistance and wear resistance of the tool itself and to improve the finishing accuracy of the work material.

It is the schematic of the tool front-end | tip part of the radius end mill which concerns on this invention, Comprising: (a) is the side view which faced the rake face to the front, (b) is the side view which faced the outer periphery blade to the front. It is a principal part enlarged view of the radius end mill shown in FIG.1 (b). It is a schematic side view of the whole radius end mill. It is a perspective view of the tool front-end | tip part of a radius end mill. It is a schematic diagram explaining the manufacturing method of a radius end mill, (a) and (b) are the figures seen from the different direction. It is a whole block diagram which shows the laser processing apparatus used for the manufacturing method of the end mill which concerns on this invention. It is a schematic diagram explaining the light intensity distribution of a laser beam.

Embodiments of an end mill according to the present invention will be described below with reference to the drawings.
As shown in FIGS. 3 and 4, the end mill of the present embodiment has a tool tip 2 that rotates about an axis D, and a pair of cutting edges 11 are 180 ° in the circumferential direction at the tool tip 2. This is a two-blade radius end mill 1 arranged at a spaced position. The radius end mill 1 is a small-diameter end mill in which the outer diameter φ of the tool tip 2 is 0.1 mm or greater and 6.0 mm or less.

  As shown in FIG. 3, the radius end mill 1 is provided with a cylindrical shank portion 3, a tip end portion of the shank portion 3 is formed with a small diameter, and a substantially cylindrical tip portion 5 is formed at the tip end of the small diameter neck portion 4. The structure is joined. The tip part 5 is a cemented carbide part 6 joined to the neck part 4 and a tool tip part 2 made of a cBN sintered body or a diamond sintered body connected to the cemented carbide part 6 and having a cutting edge 11 formed thereon. It consists of.

  As shown in FIGS. 1 and 2, the cutting blade 11 includes an outer peripheral blade 12 disposed on the outer periphery of the tool tip portion 2, a bottom blade 13 disposed on the tip of the tool tip portion 2, and a distal end of the outer peripheral blade 12. And an arcuate corner blade 14 disposed between the outer peripheral edge of the bottom blade 13. Further, as shown in FIG. 1B and FIG. 2, the outer peripheral blade 12 is a twisted blade twisted around the axis D, and the bottom blade 13 is the tip of the outer peripheral blade 12 (A positioned at the tip of the cutting blade 11). It is a straight blade heading inward along the radial direction from the point). As shown in FIG. 2, the rake face 15 forming the outer peripheral blade 12 has an angle α (twist angle) with the axial direction from the tip (point A) side to the rear end (point B) side (shank). It is formed so as to become continuously smaller toward the portion 3 side).

  For example, in the radius end mill 1 shown in FIGS. 1 and 2, the outer diameter (diameter) φ of the tool tip 2 (outer peripheral blade 12) is 0.5 mm, and the effective length h (axial distance) of the cutting blade 11 is 0. .4 mm, the rake face 15 is provided in a negative shape. In this case, the angle α of the rake face 15 is provided to change from 5 ° to 2 ° from the tip of the shaft (0 mm) to the position of 0.3 mm in the axial direction, and further from the position of 0.3 mm to 0.4 mm. It is provided by changing to 1 ° over the position. Further, the surface roughness Rz (maximum height) of the rake face 15 is in the vicinity of the ridgeline of the cutting edge 11 (a range indicated by hatching in FIG. 1A, a width 1/50 of the diameter from the cutting edge 11, The outer range of 0.01 mm from the cutting edge 11) is set to be less than 0.05 μm, the inner range inside is set to 0.05 μm or more and 0.08 μm or less, and the surface roughness Rz decreases from the inside to the outside. Thus, it is provided continuously changing.

As shown in FIG. 5, the radius end mill 1 configured as described above forms a shape of the cutting edge 11 or the like by irradiating the columnar material 20 that becomes the tool tip 2 with the laser beam L.
As shown in FIG. 6, a laser processing apparatus 100 used in this manufacturing method irradiates a cylindrical material 20 made of a cBN sintered body or a diamond sintered body with a laser beam L to three-dimensionally process the entire tool tip 2. It is a device to do. The laser processing apparatus 100 includes a laser beam irradiation mechanism 22 that scans the laser beam L while oscillating the laser beam L at a constant repetition frequency, and rotates, swivels, and rotates while holding the columnar material 20. A material holding mechanism 24 that can move in the xyz-axis direction and a control unit 25 that controls these are provided.

The material holding mechanism 24 has a mechanism that can translate the work material in each of xyz directions, and can perform a turning motion and a rotation motion. Specifically, an x-axis stage unit 31x movable in the x direction parallel to the horizontal plane, and provided on the x-axis stage unit 31x and movable in the y direction perpendicular to the x direction and parallel to the horizontal plane Y-axis stage part 31y, z-axis stage part 31z provided on y-axis stage part 31y and movable in a direction perpendicular to the horizontal plane, and axis D of columnar material 20 provided on z-axis stage part 31z And a turning mechanism 32 for adjusting the angle formed by the laser pulse irradiation, and a rotation mechanism fixed to the turning mechanism 32 and capable of holding the columnar material 20 and rotating the columnar material 20 around the axis D. 33.
For example, a servo motor is used for each of the drive portions of the stage portions 31x to 31z, the turning mechanism 32, and the rotation mechanism 33, and the phase can be fed back by an encoder.

The laser beam irradiation mechanism 22 includes a laser light source 26 that pulse-oscillates a laser beam that becomes a laser beam L by a Q switch, and an optical system that scans the laser beam L to be irradiated and focuses the laser beam in a spot shape on the same plane. And a galvano scanner 27 having.
As the laser light source 26, a light source capable of irradiating laser light having a short wavelength of 190 nm to 550 nm can be used. For example, in this embodiment, a UV-YAG laser (third harmonic: wavelength 355 nm, processing position output: 5 W, 60 kHz) ) Which can oscillate and emit laser light. The galvano scanner 27 is disposed directly above the material holding mechanism 24, and the laser beam L is emitted from the vertical direction (z-axis direction).

  Note that the polarization state of the laser may be controlled according to the material to be processed. For example, a cBN sintered body is a composite material of cBN (cubic boron nitride) particles and a binder, and there is a large band gap difference between cBN particles having a large band gap of about 6 eV and the binder. Similarly, PCD (diamond sintered body) is a composite of micron-sized synthetic diamond powder that is sintered and bonded under high temperature and pressure, and is a composite of diamond crystallites and sintering aids required for sintering. There is a large band gap difference between diamond and a sintering aid, which is a material mainly having a large band gap of 5.47 eV. For this reason, even in the case of processing by multiphoton absorption, when the laser beam is incident on s-polarized light, the change in the absorption rate is increased, so that cBN particles and diamond crystallites are less likely to be processed. Since surface undulations become unstable, radial polarization exhibits the effect of the present invention particularly in cBN sintered bodies and PCD.

A method of manufacturing the radius end mill 1 using the laser processing apparatus 100 configured as described above will be described.
First, outer diameter processing is performed on the columnar material 20 (outer diameter processing step). The outer diameter machining step is performed by moving the laser beam L along the shape of the cutting edge 11 after machining to the rotating columnar material 20 in a state where the columnar material 20 is rotated about the axis x.
At this time, since the laser beam L is irradiated with the cylindrical material 20 rotated around the axis D, the outer peripheral surface of the rotating cylindrical material 20 is randomly irradiated with the laser beam L. The Therefore, the surface roughness Rz of the outer peripheral surface of the columnar material 20 can be formed with a smooth surface of 0.1 μm or less.

  Next, a rake face 15 is formed on the cylindrical material 20 that has been subjected to outer diameter processing, and the flank 16 is processed to produce the radius end mill 1 having the outer peripheral edge 12 and the bottom edge 13 (cutting edge processing step). ). In this cutting edge processing step, as shown in FIG. 2, the rake face 15 has an angle α with the axial direction from the tip (point A) side to the rear end (point B) side (shank portion 3 side). It is formed so as to continuously decrease from 5 ° to 1 °. Further, the surface roughness Rz is formed on a smooth surface of 0.08 μm or less, and is formed so as to gradually decrease from the inside to the outside.

The method for forming the rake face 15 will be further described in detail.
As shown in FIGS. 4A and 4B, the laser beam L is irradiated onto the surface of the columnar material 20, and from the front end side of the shaft to the rear end side along the shape of the rake face 15 to be formed. Process toward.
Light intensity distribution in the radial cross section of the laser beam L, as shown by hatching in FIG. 7, larger in beam center L _0, and has a small Gaussian distribution at the peripheral portion. Compared with the focal position of the laser beam L, the light intensity distribution spreads in the radial direction and becomes a Gaussian distribution with a gentle light intensity at the defocused position. For this reason, the angle of the cutting surface can be changed with respect to the irradiation direction (depth direction) of the laser beam L by changing the irradiation position of the laser beam L to a position shifted in depth from the focal position. Therefore, the laser beam L, taking into account the depth position and the Gaussian distribution, while inclining the beam center L ₀ with respect to the rake face 15, is irradiated onto the cylindrical material 20.

  Specifically, as shown in FIGS. 4A and 4B, the rake face 15 is obtained by moving the columnar material 20 with respect to the laser beam L irradiated from the vertical direction (z-axis direction). Process. At this time, the machining is performed while moving the planned machining position of the rake face 15 to a depth position where the machining angle of the workpiece of the laser beam L is 4 ° (a position indicated by a broken line in FIG. 4A). That is, by moving the columnar material 30 in the z-axis direction and combining the turning angle around the axis D (the turning angle of the rotating mechanism 33) and the turning angle of the turning mechanism 32, a predetermined beam of the laser beam L is obtained. Processing is performed by moving the planned processing position of the rake face 15 of the cylindrical material 20 to the depth position.

As described above, the rotation angle around the axis D of the cylindrical material 20 (the rotation angle of the rotation mechanism 33) and the rotation of the rotation mechanism 32 according to the processing angle of the laser beam L (the light intensity distribution of the laser beam L). By adjusting the angle in combination with the angle, it is possible to machine the rake face 15 having an angle α that changes from the front end (point A) side to the rear end (point B) side of the shaft.
The laser beam L is pulse-oscillated, and the surface roughness of the processed surface can be continuously changed by changing the pulse conditions and scanning speed and the depth position of the laser beam L. For this reason, the rake face 15 can be formed as a smooth surface having a surface roughness Rz of 0.08 μm or less, and can further be formed so that the surface roughness Rz gradually decreases from the inside to the outside.
In addition, by performing laser processing according to the above procedure, even if it is a brittle material such as a cBN sintered body or a diamond sintered body, the end mill with a reduced diameter can be processed with high accuracy. The finishing processing accuracy can be improved.

  In the radius end mill 1 configured as described above, the angle α (twist angle) with the axial direction of the rake face 15 of the outer peripheral blade 12 is continuously extended from the front end (point A) side to the rear end (point B) side. Therefore, the cutting blade 11 adapted to the cutting conditions can be formed from the front end side to the rear end side of the shaft of the outer peripheral blade 12, and the necessary cutting edge strength at each position of the cutting blade 11. And finishing accuracy of the work material can be ensured.

  Specifically, as the angle α with the axial direction of the rake face 15 of the outer peripheral blade 12 increases, the contact area between the outer peripheral blade 12 and the work material increases, but the outer peripheral blade 12 is inclined with respect to the axis D. As a result, the cutting resistance is reduced and the dischargeability of the cutting waste is increased. For this reason, on the tip (point A) side of the shaft, by increasing the angle α with the axial direction of the rake face 15 of the outer peripheral blade 12, the contact area is increased and the peripheral blade 12 bites into the work material. The sticking can be improved, and the cutting resistance can be reduced to improve the finishing accuracy.

  On the other hand, on the rear end (point B) side of the shaft, if the angle α with the axial direction of the rake face 15 of the outer peripheral blade 12 is excessively increased, waviness tends to occur on the finished surface on the rear end side of the shaft. It is desirable to reduce the angle α. However, if the angle α is made too small, the cutting resistance increases and the dischargeability of the cutting waste decreases, so that tool chatter and chipping are likely to occur.

In this regard, in the radius end mill 1 of the above embodiment, the angle α is set smaller on the rear end side than the front end side of the shaft, in other words, the angle α on the front end side is set larger than the rear end side of the shaft. This improves the chipping resistance and wear resistance at each position from the front end side to the rear end side of the shaft, thereby improving the finishing accuracy of the work material.
Further, by continuously changing the angle α, the rake face 15 smoothly connected from the bottom blade 13 to the outer peripheral blade 12 can be formed, so that stress concentration occurring during cutting can be avoided, and the fracture resistance of the tool itself can be reduced. The wear resistance can be further improved.

  Furthermore, the material of the small-diameter end mill used for precision cutting applications is a high-hardness material such as a cBN sintered body, diamond sintered body, or cemented carbide. Since it can be formed by laser processing without applying a mechanical load, it is possible to prevent a decrease in processing accuracy due to deflection or the like caused by processing with a conventional grindstone.

Further, since the rake face 15 can be formed with a smooth surface having a surface roughness Rz of 0.08 μm or less by laser processing, the ridgeline of the cutting edge 11 can be formed with a sharp ridgeline, and the work material The surface accuracy of the finish can be improved. Further, even if the rake face 15 is formed with a slight inclination angle of 5 ° to 1 °, the rake face 15 is formed as a smooth surface, thereby smoothly guiding and discharging the cutting waste. Therefore, it is possible to configure a cutting edge with high machinability.
Further, in the radius end mill 1, the rake face 15 is arranged in the vicinity of the ridgeline of the cutting edge 11 (a range indicated by hatching in FIG. 1A, a width that is 1/50 of the diameter from the cutting edge 11, here the cutting edge 11 to 0 .01 mm outer range) is less than 0.05 μm, and the inner inner range is formed with a surface roughness Rz of 0.05 μm or more and 0.08 μm or less, and the surface roughness Rz gradually decreases from the inside to the outside. It is formed to become. Thereby, in the inner range, the contact area of the cutting waste can be reduced to reduce heat generation, and the heat radiation can be increased to prevent welding of the cutting waste, thereby improving the tool life. The range shown by hatching (outer range) in FIG. 1A is most effective when the width is about twice the recommended cutting depth (ae, ap) of the tool.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, in the above-described embodiment, an example in which the end mill of the present invention is applied to a radius end mill has been described. The present invention can also be applied to a square end mill that forms a cutting edge that intersects the outer peripheral edge with a sharp corner.

1 Radius end mill (end mill)
2 Tool tip part 3 Shank part 4 Neck part 5 Tip part 6 Cemented carbide part 11 Cutting edge 12 Outer peripheral edge 13 Bottom edge 14 Corner edge 15 Rake face 16 Flank face 20 Columnar material 22 Laser light irradiation mechanism 24 Material holding mechanism 25 Control Unit 26 laser light source 27 galvano scanner 31x x-axis stage unit 31y y-axis stage unit 31z z-axis stage unit 32 turning mechanism 33 rotating mechanism 100 laser processing apparatus

Claims (2)

A tool tip having a diameter of 0.1 mm or more and 6.0 mm or less made of a cBN sintered body or a diamond sintered body,
Comprising at least a pair of cutting edges comprising an outer peripheral blade disposed on the outer periphery of the tool tip and a bottom blade disposed on the tip of the tool tip;
The angle with the axial direction of the rake face of the outer peripheral blade is provided continuously changing from the front end side to the rear end side of the shaft ,
As for the surface roughness Rz of the rake face, the outer range of 1/50 of the diameter from the outer peripheral blade is set to be less than 0.05 μm, and the inner range inside thereof is set to 0.05 μm or more and 0.08 μm or less. End mill.   The end mill according to claim 1, wherein the angle of the rake face with respect to the axial direction is set to be smaller on the rear end side than on the front end side of the shaft.

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