JP2014091168A - End mill and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an end mill that when rotated, can improve defect resistance in a fast-moving outer periphery side and reduce cutting resistance in a slow-moving shaft line side so as to cut even an object with a small diameter of 2 mm or less keeping stable strength, thereby improving cutting performance and realizing long service life.SOLUTION: In a ridge line part between a cutting face 14 and a flank face 16 of a bottom blade 13 is formed a honing face 17 with a convex circular cross section that is 2 mm or less in diameter and orthogonal to the longitudinal direction of the ridge line part, and a curvature radius R of the honing face 17 is formed to gradually increase while going toward the outside in a radial direction.

Description

  The present invention relates to a small-diameter end mill used for processing precision molds and the like, and a method for manufacturing the same.

The end mill has a cutting blade portion formed of an outer peripheral blade formed at the outer peripheral portion and a bottom blade formed at the tip, and a shank portion. The end mill rotates around the axis, and the outer peripheral blade cuts a vertical surface along the axial direction, and the bottom blade cuts a horizontal plane perpendicular to the axial direction.
In this type of end mill, if the cutting edge is too sharp, it tends to be damaged, so chamfer honing or the like is generally formed on the cutting edge by grinding using a grindstone to extend the life. Improves deficiency and extends life. In this case, the tool rotating around the axis is different in peripheral speed on the side close to the axis of the bottom blade and on the side close to the outer peripheral part, and the chip must be fracture resistant to prevent chipping on the outer peripheral part where the speed is high. Therefore, it is necessary to reduce the cutting resistance on the axis line side where the speed is slow.

  For example, an end mill disclosed in Patent Document 1 has been proposed as an end mill that has improved chipping resistance and has a long service life. In this end mill, in an end mill having a plurality of rounded blades at the tip, a margin is provided in the rounded blade, and the width of the margin is made variable within one blade to obtain a stable cutting process.

JP 2003-285218 A

However, the end mill of Patent Document 1 attempts to increase the efficiency by reducing the cutting resistance by adjusting the width of the margin. However, since this margin comes into contact with the work material by planar contact during cutting, the cutting resistance Is big.
In recent years, the demand for small-diameter end mills with a diameter of 2 mm or less is expected to increase along with the complexity and miniaturization of the mold shape. It is important to improve deficiency.

  The present invention has been made in view of such circumstances, and improves the fracture resistance on the outer peripheral side where the speed is high during rotation, reduces the cutting resistance on the axis side where the speed is low, and has a small diameter of 2 mm or less. It is an object of the present invention to provide an end mill that can be cut while maintaining a stable strength, and that can improve machinability and extend its life, and a method for manufacturing the end mill.

  The end mill of the present invention has a diameter of 2 mm or less, and a honing surface having a convex arc shape in a cross section perpendicular to the length direction of the ridge line portion is formed at the ridge line portion between the rake face and the flank face of the bottom blade. At the same time, the radius of curvature of the honing surface is formed so as to gradually increase toward the outside in the radial direction of the bottom blade.

  In this way, the radius of curvature of the honing surface is gradually increased toward the outer side in the radial direction of the bottom blade, so that the radius of curvature of the honing surface becomes smaller near the center on the axis side and the cutting edge becomes sharper. The radius of curvature of the honing surface increases as it approaches the outer peripheral side. Therefore, it is possible to improve the cutting performance of the cutting edge to suppress cutting resistance on the axis side where the speed is low, and to improve chipping resistance and prevent chipping on the outer peripheral side where the speed is high. In addition, by continuously changing the radius of curvature of the honing surface, it is possible to form a bottom blade with good balance and good cutting ability that is stable in strength.

  In the end mill of the present invention, the radius of curvature of the honing surface varies with a taper ratio of 1/50 or more and 1/20 or less from the axial direction outward in the radial direction, and is ½ of the standard cutting depth at the outer peripheral end. It may be the following.

To provide a small end mill that can form a sharp cutting edge with an almost pin angle on the axis and a honing surface with a large radius of curvature at the outer periphery, improving both machinability and fracture resistance Can do.
In this case, if the taper ratio is less than 1/50, a desired honing surface cannot be obtained. If the taper ratio is more than 1/20, the resistance on the outer peripheral side and the resistance on the axis side are greatly different and sufficient strength is obtained. I can't. Further, when the radius of curvature of the honing surface at the outer peripheral end exceeds 1/2 with respect to the standard cutting depth, the resistance due to honing becomes too large, and thus sufficient strength cannot be obtained.

  In the manufacturing method of the end mill of the present invention, the ridge line portion between the rake face and the flank face of the bottom blade is irradiated with a laser beam having a Gaussian distribution in which the light intensity distribution of the cross section is large at the center in the radial direction and small at the outer periphery, A laser processing step of processing a honing surface having a convex arc shape in a cross section orthogonal to the length direction of the ridge line portion, and the scanning direction of the laser beam in the laser processing step is outward in the radial direction of the bottom blade The laser beam center is gradually inclined from the position away from the ridge line portion in the direction in which the ridge line portion gets into gradually.

The end mill manufacturing method of the present invention uses the light intensity distribution of the Gaussian distribution of the laser beam, can form a honing surface having a continuous radius of curvature while shifting the radial position of the beam with respect to the irradiation position. An end mill having a highly accurate cutting edge can be manufactured from the side to the outer peripheral side.
As described above, the demand for small-diameter end mills having a diameter of 2 mm or less is expected to increase with the complexity and miniaturization of the mold shape. In such small-diameter end mills, conventional grindstones are used. In the processing method, it is difficult to grind while adjusting the grinding amount between the outer peripheral side and the axis side in particular. However, the manufacturing method of the present invention improves the machinability of the bottom blade and suppresses the consumption of the small diameter end mill. And can be applied to complicated and miniaturized molds and the like to improve the manufacturability.

  According to the present invention, even in the case of a small diameter, cutting can be performed while improving the machinability while ensuring stable strength and preventing the cutting edge portion from being worn out or damaged, and the tool can have a long life. .

One Embodiment of the end mill which concerns on this invention is shown, (a) is a perspective view of a tool front-end | tip part, (b) is an expansion perspective view of a honing surface. It is the front view which looked at the tool front-end | tip part from the front-end | tip direction. It is sectional drawing which follows the AA line of FIG. 2, BB line, and CC line. It is the side view which looked at the tool front-end | tip part from the rake face direction. It is a schematic side view of the whole end mill. It is a whole lineblock diagram showing the laser processing device of one embodiment used for the manufacturing method of the end mill concerning the present invention. It is a schematic diagram which shows the positional relationship of the laser beam which processes a honing surface, and a tool front-end | tip part. It is a schematic diagram which shows the scanning state of a laser beam.

Hereinafter, an embodiment of an end mill and a manufacturing method thereof according to the present invention will be described with reference to the drawings.
As shown in FIGS. 1 to 4, the end mill 1 of the present embodiment has a pair of cutting blade portions 11 formed on the opposite side of 180 ° across the axis D on the tool tip 2 rotated around the axis D. Further, the outer diameter of the tool tip 2 is provided with a small diameter of 2 mm or less.
As shown in FIG. 5, the end mill 1 is provided with a columnar shank portion 3, the tip portion of the shank portion 3 is formed with a small diameter, and the tip portion 5 having a substantially circumferential shape is formed at the tip of the neck portion 4 with the small diameter. Are joined. The tip part 5 is a cemented carbide part 6 joined to the neck part 4 and a tool tip part 2 such as a sintered cBN sintered body or sintered diamond connected to the cemented carbide part 6 to form a cutting edge part 11. It consists of and.

The cutting blade portion 11 is formed by an outer peripheral blade 12 disposed at the outer peripheral portion of the tool tip portion 2 and a bottom blade 13 disposed at the distal end of the tool tip portion 2, and the distal end of the outer peripheral blade 12 and the bottom blade 13 are formed. Intersects with a sharp corner. And this pair of cutting-blade part 11 is arrange | positioned in the position 180 degree apart in the circumferential direction.
In this case, the outer peripheral edge 12 is formed by a rake face 14 formed at a distance of 180 ° in the circumferential direction from the tool tip 2 and an outer flank face 15, and the bottom edge 13 is formed by the rake face 14 and the flank edge. Formed by the surface 16.

Then, a honing surface 17 having a convex arc shape in the cross section perpendicular to the length direction of the ridge line portion is formed at the ridge line portion between the rake face 14 and the flank 15 of the bottom blade 13. The radius of curvature R of the honing surface 17 is gradually increased from the axis D of the end mill 1 toward the outer side in the radial direction, as shown in FIGS. Specifically, the taper ratio of 1/50 or more and 1/20 or less from the axis D toward the outside in the radial direction, that is, the radius of curvature is 1 μm or more and 2.5 μm or less (the diameter is 2 μm or more and 5 μm or less as it advances 100 μm). ) And is provided at a radius of curvature R having a radius equal to or less than ½ of the standard cut depth (the cut depth in the axial direction per rotation) at the outer peripheral end.
This standard cutting depth is determined by the diameter of the end mill, the type of work material, cutting conditions, etc. For example, when cutting hardened steel (-55HRC), the standard cutting depth is 0.5 mm for an end mill. 10 μm (rotational speed 50000 mm ⁻¹ , feed speed 750 mm / min). Under this condition, if the taper ratio is 1/50, the honing surface has a radius of curvature at the axis center of 0 μm and a radius of curvature of the outer peripheral end of 5 μm. When the same work material is cut with an end mill having a diameter of 2 mm, the standard cutting depth is 40 μm (rotational speed 20000 mm ⁻¹ , feed speed 800 mm / min), and the honing surface has a radius of curvature of 0 μm at the axis center. The radius of curvature at the outer peripheral edge is 20 μm.

  When the end mill 1 configured as described above is manufactured, a bottom blade groove (hereinafter referred to as a gash) and a rake face 14 are formed in the columnar material 20 serving as the tool tip 2 by laser processing, and the clearance on the outer peripheral side is formed. The surface 15 is formed to form the outer peripheral blade 12, and the tip side flank 16 is formed to form the bottom blade 13. Then, a honing surface 17 is formed at the ridge line portion between the rake face 14 and the flank face 16 of the bottom blade 13.

  As shown in FIG. 6, the laser processing apparatus 100 used in this manufacturing method is an apparatus that three-dimensionally processes the entire tool tip 2 by irradiating a columnar material 20 made of cemented carbide with a laser beam L. 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 workpiece in each of the xyz directions, and can perform a turning motion and a rotation motion. Specifically, an x-axis stage portion 31x that moves in the x direction parallel to the horizontal plane, and a y-axis that is provided on the x-axis stage portion 31x and is movable in the y direction perpendicular to the x direction and parallel to the horizontal plane Fixed to the stage 31y, the z-axis stage 31z provided on the y-axis stage 31y and movable in the direction perpendicular to the horizontal plane, the turning mechanism 32 provided on the z-axis stage, and the turning mechanism 32 The rotation mechanism 33 capable of holding the material 20 is provided. For example, a stepping motor is used for each of the drive units of the stage units 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 collects 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 with a short wavelength of 190 nm to 550 nm can be used. For example, in this embodiment, a laser light source that can oscillate and emit laser light with a wavelength of 355 nm is used. The galvano scanner 27 is disposed directly above the material holding mechanism 24.
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 for manufacturing the end mill 1 using the laser processing apparatus 100 configured as described above will be described.
A laser beam L is scanned while moving the columnar material 20 to form a gash and rake face 14 on the tool tip 2, and a peripheral flank 15 and a tip flank 16 are formed respectively. The outer peripheral blade 12 and the bottom blade 13 having a predetermined shape are formed.
The method for forming the bottom blade 13 will be described in more detail. The rotation axis of the rotation mechanism 33 in the material holding mechanism 24 and the axis D of the columnar material 20 are made to coincide with each other, and the x axis of the galvano scanner 27 is also made to coincide. Install in. In this state, the cylindrical material 20 is moved to a processing region where the cross-sectional intensity distribution of the laser beam L is normal, and unnecessary portions are removed from the tool tip 2 by scanning the laser beam L. Perform morphogenesis. Thereafter, honing is applied to the ridge line portion between the rake face 14 and the flank face 16.

As shown in FIG. 4, an angle (a watermark angle) θ of the bottom blade 13 with respect to the radial direction is normally an angle of 2 ° to 5 °, and the laser beam L as a whole has the bottom blade angle θ. Along the axis D and scanned toward the outer peripheral end. In this case, escape the laser beam center L ₀ is the end cutting edge (rake face 14 in the radial direction of L in accordance with the scanning direction of the laser beam L toward the radially outer end cutting edge 13, as shown in FIG. 8 (a) Slightly incline from the position away from the edge 16 of the surface 16 to the bottom blade 13 gradually. In FIG. 8, a region S indicated by a two-dot chain line is a laser beam irradiation range.

That is, the light intensity distribution in the radial cross section of the laser beam L is a small Gaussian distribution increases the outer peripheral portion at the beam center L ₀ as indicated by hatching in FIG. 7, scanning by slightly inclined Thus, the center side of the tool tip 2 irradiates near the radial edge of the laser beam L as shown by the solid line in FIG. 7, and the radius of the laser beam L as shown by the two-dot chain line in FIG. Irradiate within the range of exceeding. Scanning along the radial direction of the bottom blade 13 while gradually changing the radial irradiation position of the laser beam L as shown by the arrows in FIG. 7, the results shown in FIGS. Thus, it becomes possible to give the honing surface 17 from which the curvature radius R differs from the axis line D side to an outer peripheral end.

While changing the direction of the cylindrical material 20 and the irradiation angle of the laser beam L as necessary as shown in FIGS. 8A and 8B, the irradiation of the laser beam L is changed as necessary until a desired radius of curvature R is obtained. The honing surface 17 having a desired shape is formed on the bottom blade 13 by repeating the processing on the bottom blade 13.
As a condition for irradiation with the laser beam L at this time, the radius of curvature R of the honing surface 17 of the tool tip 2 is a taper ratio of 1/50 or more and 1/20 or less from the axis D toward the outside in the radial direction. It changes so that it becomes 1/2 or less of the standard cutting depth at the outer peripheral edge.

In the end mill 1 manufactured in this way, the honing surface 17 of the bottom blade 13 has a convex arc shape in cross section, and its radius of curvature gradually increases from the axis side toward the outer peripheral end. A sharp cutting edge and a cutting edge having a large honing on the outer peripheral side. Therefore, cutting resistance can be suppressed by a sharp cutting edge on the axis side where the peripheral speed is slow, and a large honing is applied on the outer peripheral side where the peripheral speed is high, thereby preventing defects and stabilizing the strength.
In this case, if the taper ratio is less than 1/50, a desired honing surface cannot be obtained. If the taper ratio is more than 1/20, the resistance on the outer peripheral side and the resistance on the axis side are greatly different and sufficient strength is obtained. I can't. Further, when the radius of curvature of the honing surface at the outer peripheral end exceeds 1/2 with respect to the standard cutting depth, the resistance due to honing becomes too large, and thus sufficient strength cannot be obtained.
By using the honing surface 17 having continuously different radii of curvature, the life of the end mill 1 can be dramatically improved. For example, the life of 1.5 to 2 times that of the conventional product can be obtained.
Note that the end blade of the end mill is inclined at an angle (a watermark angle) θ of 2 ° to 5 ° with respect to the radial direction as described above. Therefore, the diameter is 0.5 mm and the watermark angle θ is 5 In the end mill at 0 °, when cutting a standard cutting depth of 10 μm, a bottom blade in a range from the outer peripheral end to 114 μm in the radial direction is used as an actual cutting blade. Assuming that the honing surface is formed to the extent that this standard cut depth can be covered, the radius of curvature of the outer peripheral end is set to 5 μm as described above, and the radius of curvature at a position 114 μm in the radial direction from the outer peripheral end is set to 0 μm. Then, the taper ratio is (5-0) / 114≈1 / 20. When the angle θ is smaller than 5 °, the taper ratio becomes small.

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.
In FIG. 1B and the like, the radius of curvature of the honing surface is shown as a single radius. However, the present invention includes a shape in which a plurality of arcs are continuously formed. What is necessary is just to process so that a curvature radius may become large overall toward the direction.
In this embodiment, both the outer peripheral blade and the bottom blade are formed by laser processing. However, forms other than the bottom blade can be processed by a method other than laser.

DESCRIPTION OF SYMBOLS 1 End mill 2 Tool tip part 3 Shank part 4 Neck part 5 Tip part 6 Cemented carbide part 11 Cutting blade part 12 Outer peripheral blade 13 Bottom blade 14 Rake face 15, 16 Relief face 17 Honing face 20 Columnar material 22 Laser beam irradiation mechanism 24 Material holding mechanism 25 Control unit 26 Laser light source 27 Galvano scanners 31x to 31z Stage unit 32 Turning mechanism 33 Rotating mechanism 100 Laser processing apparatus

Claims (3)

  A honing surface having a diameter of 2 mm or less and having a convex arc shape in a cross section perpendicular to the length direction of the ridge line portion is formed on the ridge line portion between the rake face and the flank face of the bottom blade. An end mill characterized in that the radius of curvature is gradually increased toward the outer side in the radial direction.   The radius of curvature of the honing surface varies with a taper ratio of 1/50 or more and 1/20 or less from the axial direction toward the outside in the radial direction, and is 1/2 or less of the standard cutting depth at the outer peripheral end. The end mill according to claim 1.   Irradiating the ridge line between the rake face and flank face of the bottom blade with a laser beam whose light intensity distribution in the cross section is large at the center in the radial direction and small at the outer periphery, and perpendicular to the length direction of the ridge line part A laser processing step of processing a honing surface having a convex arc shape in cross section, and the laser beam center in the laser processing step is directed outwardly in the radial direction of the bottom blade. A method of manufacturing an end mill, characterized by inclining in a direction in which the ridge line portion is gradually recessed from a position away from the ridge line portion.

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