JP2020040179A - Method of machining wall surface of rib groove and tapered end mill - Google Patents

Abstract

To provide a method of machining a wall surface of a rib groove, which enables elimination of minute steps caused by machining.SOLUTION: There is provided a method of machining a wall surface of a rib groove, by which contour machining is performed with a tapered end mill. The tapered end mill has a tapered blade portion including: a tapered web thickness portion; a spherical portion 23 located at a tip of the web thickness portion; outer peripheral blades 21a which are located at an outer periphery of the web thickness portion, and which spirally extend along an axial direction; and bottom blades 21b located on an outer peripheral surface of the spherical portion. At a boundary between the blade portion and a neck portion, a diameter of the neck portion is less than a diameter of the outer peripheral blade, and greater than a diameter of the web thickness portion, while the ratio of an axial length of the blade portion relative to a diameter of a tip of the outer peripheral blade is 2 or greater and 8 or less. The outer peripheral blades include: first outer peripheral blades 21aa each of which is continuous with each bottom blade; and second outer peripheral blades 21ab disposed circumferentially between the first outer peripheral blades. At a boundary between each second outer peripheral blade and the spherical portion, there is provided a tapered surface 27 inclined to an axis, toward the tip side. A taper angle α of the tapered surface is greater than a taper angle θ20 of the outer peripheral blade.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for processing a wall surface of a rib groove and a tapered end mill.

  2. Description of the Related Art Conventionally, in processing a rib groove of a mold, reciprocating processing is performed using a tapered end mill having a long blade length as shown in FIG.

JP-A-2002-126929 JP-A-2003-94226

  When reciprocating machining using a taper end mill in machining of a rib groove of a mold, there is a problem that as the machined portion becomes deeper, the bending of the end mill increases and the unremoved amount increases. Therefore, in recent years, in the rib groove processing of a mold, it has been proposed to perform contour line processing with a ball end mill having a long neck length as in Patent Document 2. For example, when processing a rib groove having a depth of 16 mm, as a roughing process, first a contour line is formed to a depth of 6 mm by a ball end mill 6 mm below the neck, and then a contour line is formed to a depth of 10 mm by a ball end mill 10 mm below the neck. Then, contour machining is performed to a depth of 16 mm with a ball end mill 16 mm below the neck. Finally, finish processing by contour line processing is performed using a ball end mill 16 mm below the neck. By performing such contour processing, the residual amount tends to be reduced, but a small processing step occurs at the time of tool change in rough processing, and it can be removed by finishing processing unless the axial depth of cut is reduced. It is difficult, and there is a problem in processing efficiency and accuracy (unevenness of the remaining amount along the depth direction). In addition, when the outer peripheral blade includes one that is not connected to the bottom blade, there is also a problem that a fine processing step is formed on a wall surface processed by the tip of the outer peripheral blade.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of processing a wall surface of a rib groove and a taper end mill capable of eliminating a minute processing step.

  A method of machining a wall surface of a rib groove according to one embodiment of the present invention is a method of machining a wall surface of a rib groove using a tapered end mill that rotates along an axis, wherein the tapered end mill has a shank portion held by a machine tool. And a lower part of the neck located on the distal end side of the shank part. The lower part of the neck has a tapered blade part, and the blade part is located on the base end side of the blade part and has an axial length. A tapered neck portion that is equal to or longer than the axial length of the portion, and the blade portion has a tapered core thickness portion, a spherical portion located at the tip of the core thickness portion, and the core thickness portion. An outer peripheral blade that is located on the outer periphery and extends spirally along the axial direction, and a bottom blade that is located on the outer peripheral surface of the spherical portion, and at a boundary between the blade portion and the neck portion, a diameter of the neck portion Is smaller than the diameter of the outer peripheral blade, larger than the diameter of the core thick portion, and is smaller than the diameter of the tip of the outer peripheral blade. The ratio of the length of the blade portion in the axial direction is 2 or more and 8 or less, and the outer peripheral blade is located between the first outer peripheral blade connected to the bottom blade and the first outer peripheral blade in the circumferential direction. A second outer peripheral blade to be disposed, and a boundary portion between the second outer peripheral blade and the spherical portion is provided with a tapered surface that is inclined toward the axis side toward the distal end side, and the taper of the tapered surface is provided. The contour processing is performed using the taper end mill having an angle larger than the taper angle of the outer peripheral blade.

  According to the above-described configuration, at the boundary between the blade and the neck, the diameter of the neck is smaller than the diameter of the outer peripheral blade, and larger than the diameter of the core thick portion. Since the diameter of the neck at the boundary is smaller than the diameter of the outer peripheral blade, interference between the workpiece and the neck can be reliably suppressed in the processing of the wall surface of the rib groove by contour processing. In addition, since the diameter of the neck portion at the boundary is larger than the diameter of the core thick portion, the bending of the neck portion at the time of processing can be suppressed, and the amount left unremoved can be suppressed. Since the neck portion is formed in a tapered shape, the diameter of the neck portion is the smallest at the boundary.

According to the above configuration, the ratio of the axial length of the blade portion to the diameter of the tip of the outer peripheral blade is 2 or more and 8 or less.
By setting the ratio of the axial length of the blade portion to the diameter of the tip of the outer peripheral blade to 8 or less, in the processing of the wall surface of the rib groove by contour processing, the unevenness of the residual amount along the depth direction is eliminated. be able to. On the other hand, if the blade portion is too long, the number of contacts between the outer peripheral blade and the workpiece in the depth direction becomes remarkable. More specifically, as the blade portion becomes longer, the number of times of contact between the outer peripheral blade and the work material near the lower end of the processing region is significantly smaller than the number of times of contact near the upper end. When the number of times of contact with the outer peripheral blade in the work material decreases, the remaining amount relatively increases. For this reason, if the blade portion is too long, there is a possibility that the amount of unprocessed portion on the processed surface on which the finishing process has been performed increases in the depth direction. In addition, by setting the ratio of the length of the blade portion in the axial direction to the diameter of the tip of the outer peripheral blade to 8 or less, the neck portion having a high rigidity at the lower part of the neck can be made relatively long. Thereby, the rigidity of the lower part of the neck is increased, the bending of the lower part of the neck is suppressed, and the unevenness of the remaining amount of the work material in the depth direction can be suppressed.
Further, by setting the ratio of the axial length of the blade portion to the diameter of the tip of the outer peripheral blade to be 2 or more, the remaining amount can be sufficiently suppressed in processing the wall surface of the rib groove by contour processing. In particular, when applied to finishing, it is possible to reliably remove a step caused by roughing. In addition, if the blade portion is too short, the number of times of contact between the outer peripheral blade and the work material decreases, and there is a possibility that the removal of the step caused by the rough machining may be insufficient.
By making the neck longer than the blade, a sufficiently deep rib groove can be machined. As described above, the neck portion has higher rigidity than the blade portion. Therefore, by making the neck portion longer than the blade portion, the rigidity of the lower part of the neck can be increased to suppress the bending and reduce the unretained amount. More preferably, the ratio of the axial length of the blade to the diameter of the tip of the outer peripheral blade is 3 or more and 6 or less.

  According to the above configuration, the sharpness of the corner located at the end on the tip side of the second outer peripheral blade is suppressed by forming the tapered surface at the boundary between the second outer peripheral blade and the spherical portion. This can suppress the occurrence of a step on the processing surface by the end mill.

  Further, the above-described method of processing the wall surface of the rib groove may be a method of performing the finishing processing of the wall surface of the rib groove having a minute step.

Since the processing method of the present invention can surely remove a step caused by rough processing, it is effective to apply the method to the finish processing of the wall surface of a rib groove having a minute step.
On the other hand, the processing method of the present invention can be applied to rough processing. If applied to the rough processing of rib grooves, it is possible to form a wall surface with a constant remaining amount without steps, so that the load of the finishing process in the next process can be reduced and a more accurate rib groove wall surface can be achieved. it can. In addition, if the processing method of the present invention is applied to each of rough processing and finish processing, processing efficiency can be further improved.

  In the above-described method of processing the wall surface of the rib groove, a method may be employed in which an angle difference between the taper angle of the tapered surface and the taper angle of the outer peripheral blade is 10 ° or less.

  According to the above-described configuration, the sharpness of the corner located at the end on the distal end side of the second outer peripheral blade can be reduced, and the blade length of the second outer peripheral blade can be sufficiently ensured. The generation of a step on the surface can be suppressed.

  Further, in the above-described method for processing the wall surface of the rib groove, the axial cut amount may be 0.025 mm or more.

  According to the configuration described above, even when the cut amount in the axial direction is set to 0.025 mm or more by using the taper end mill, the step caused by the roughing is sufficiently removed when used for finishing. can do. Therefore, when applied to finishing, the processing time required for finishing can be reduced. The axial depth of cut is more preferably at least 0.05 mm, even more preferably at least 0.10 mm, even more preferably at least 0.20 mm.

  In the above-described method for processing the wall surface of the rib groove, a ratio of a length of the neck lower part in an axial direction to a diameter of a tip of the outer peripheral blade may be 8 or more and 20 or less.

  According to the above-described configuration, it is possible to process a sufficiently deep rib groove, and it is also possible to suppress bending of the lower part of the neck and reduce an unretained amount.

  Further, in the above-described method of processing the wall surface of the rib groove, at any point in the axial direction, the diameter of the tapered neck portion is 90% or more of the diameter of the extension surface of the tapered outer peripheral blade. It may be.

  According to the above configuration, since the diameter of the neck portion is configured to be sufficiently large, it is possible to suppress the bending of the neck portion at the time of machining, and to suppress the unretained amount.

  In the above-described method of processing the wall surface of the rib groove, the blade portion may have four or more outer peripheral blades arranged in a circumferential direction.

  According to the configuration described above, the number of times of contact between the outer peripheral blade and the work material is sufficiently ensured, the amount of unretained portion can be reduced, and when used for finishing, a step caused by roughing can be sufficiently removed. .

  Further, in the above-described method of processing the wall surface of the rib groove, the chip portion includes a chip discharge groove which is located between the outer peripheral blades in the circumferential direction and extends spirally along the axial direction, and the outer peripheral surface in the circumferential direction. And a flank extending from the blade to the chip discharge groove, wherein the flank is a series of one-step flank.

  According to the above configuration, the flank is formed in one step (that is, a normal flank without two-stage eccentric blades), so that the remaining amount can be reduced.

  Further, in the above-described method of processing the wall surface of the rib groove, the chip portion includes a chip discharge groove which is located between the outer peripheral blades in the circumferential direction and extends spirally along the axial direction, and the outer peripheral surface in the circumferential direction. And a flank extending from the blade to the chip discharge groove, wherein the flank is a two-step flank.

  According to the configuration described above, since the flank is formed in two steps, the flank of the work material is rubbed in contact with the processing surface at the minute flank of the first step during cutting. Thereby, the scratches and irregularities formed on the processing surface can be smoothed, and the processing surface accuracy can be improved.

  A tapered end mill according to one aspect of the present invention is a tapered end mill that extends along an axis, and has a shank portion held by a machine tool, and a lower neck portion located at a distal end side of the shank portion. The lower portion is provided with a tapered blade portion and a tapered neck portion which is located on the base end side of the blade portion and whose axial length is equal to or longer than the axial length of the blade portion. The part is a tapered core thick part, a spherical part located at the tip of the core thick part, an outer peripheral blade located at the outer periphery of the core thick part and extending helically along the axial direction, and the spherical part A bottom blade located on the outer peripheral surface, wherein at the boundary between the blade portion and the neck portion, the diameter of the neck portion is smaller than the diameter of the outer peripheral blade, larger than the diameter of the core thick portion, and the outer periphery A ratio of an axial length of the blade portion to a diameter of a tip of the blade is 2 or more and 8 or less; The blade includes a first outer peripheral blade connected to the bottom blade, and a second outer peripheral blade disposed between the first outer peripheral blade in a circumferential direction, and the second outer peripheral blade and the spherical portion. A tapered surface that is inclined toward the axial line toward the distal end is provided at a boundary portion between the outer peripheral edge and the outer peripheral blade.

  Further, in the above-described tapered end mill, the angle difference between the taper angle of the tapered surface and the taper angle of the outer peripheral edge may be 10 ° or less.

  In the above-described tapered end mill, a ratio of an axial length of the lower part of the neck to a diameter of a tip of the outer peripheral blade may be 8 or more and 20 or less.

  In the above-mentioned tapered end mill, the diameter of the tapered neck may be 90% or more of the diameter of the extension surface of the tapered outer peripheral blade at any point in the axial direction.

  In the above-described tapered end mill, the blade portion may include four or more outer peripheral blades arranged in a circumferential direction.

  In the above-described tapered end mill, the blade portion includes a chip discharge groove which is located between the outer peripheral blades in the circumferential direction and extends helically along the axial direction, and a chip discharge groove from the outer peripheral blade in the circumferential direction. And a flank extending to the flank, wherein the flank is a series of one-step flank.

  In the above-described tapered end mill, the blade portion includes a chip discharge groove which is located between the outer peripheral blades in the circumferential direction and extends helically along the axial direction, and a chip discharge groove from the outer peripheral blade in the circumferential direction. And a flank extending to the flank, wherein the flank is a two-step flank.

  ADVANTAGE OF THE INVENTION According to this invention, the processing method of the wall surface of a rib groove | channel which can eliminate the unevenness of the remaining amount along the depth direction and a taper end mill can be provided.

FIG. 1 is a front view of an end mill used in the processing method of one embodiment. FIG. 2 is a schematic diagram illustrating a processing step by an end mill according to one embodiment. FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 4 is a perspective view near the tip of the end mill. FIG. 5 is a side view near the tip of the end mill. FIG. 6 is a partial cross-sectional view of a modified end mill. FIG. 7 is a graph comparing the measurement results of the remaining amount of the surface after finishing in Comparative Examples 1 and 2 and Examples 1 and 2. FIG. 8A is a photograph of a finished surface in Comparative Example 2. FIG. 8B is a photograph of a surface after finishing in Example 1. FIG. 8C is a photograph of a surface after finishing in Example 2. FIG. 9 is a schematic view illustrating, as a comparative example, an end mill provided with a blade portion over substantially the entire lower part of the neck.

  Hereinafter, embodiments to which the present invention is applied will be described in detail with reference to the drawings. In addition, in the drawings used in the following description, in order to make characteristic portions easy to understand, portions that do not have features may be omitted for convenience. In the following description, the finishing of the wall surface of the rib groove in which a minute step is generated by the roughing is mainly described.

  FIG. 1 is a front view of a tapered end mill (hereinafter simply referred to as an end mill) 1 used in the processing method of the present embodiment. FIG. 2 is a diagram schematically showing a processing step by the end mill 1. FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 4 is a perspective view of the vicinity of the end of the end mill 1.

As shown in FIG. 1, the end mill 1 is a rod having a substantially cylindrical shape extending along an axial direction about an axis O. The end mill 1 is made of a hard material such as a cemented carbide.
In this specification, a direction parallel to the axis O of the end mill 1 is simply referred to as an axial direction. The direction orthogonal to the axis O is called a radial direction. In addition, a direction that rotates around the axis O is referred to as a circumferential direction. Of the circumferential directions, the direction in which the end mill 1 rotates during cutting is referred to as a tool rotation direction T. In the following description, a region on the rotation direction T side with respect to a specific portion may be referred to as a front side in the rotation direction, and a region opposite to the rotation direction T may be referred to as a rear side in the rotation direction.

The end mill 1 has a shank portion 3 for mounting the end mill 1 on a main shaft of a machine tool 9 and a lower neck portion 2 located at a tip end side of the shank portion 3.
The end mill 1 is gripped by the main shaft or the like of the machine tool 9 at the shank portion 3 and rotated in the tool rotation direction T around the axis O. The end mill 1 is used for cutting (rolling) a work material such as a metal material. Further, the end mill 1 is fed around in a direction intersecting with the axis O together with the rotation about the axis O, and performs the finishing of the workpiece W.

  As shown in FIG. 2, the end mill 1 performs finishing by contour line processing with the neck lower part 2 opposed to a rough processing surface 8 of a work material W which has been rough processed to a predetermined inclination angle. A rough surface 8 of the work material W has a step 8a due to a tool path of a tool for performing rough processing. The end mill 1 removes the step 8a and performs finishing using up to a target surface. The work material W of the end mill 1 is a die, and the groove processed by the end mill 1 becomes a rib. That is, the end mill 1 of the present embodiment is used for finishing the wall surface of the rib groove of the mold having a minute step.

  In the processing method of the present embodiment, the axial cut amount may be 0.025 mm or more. When the end mill 1 described below is used, even when the axial depth of cut is set to 0.025 mm or more, the step caused by the roughing can be sufficiently removed. Thereby, the processing time required for finishing the rib groove can be reduced.

Each part of the end mill 1 will be specifically described.
The shank 3 of the end mill 1 is located on the base end side of the end mill 1. The shank portion 3 is composed of a straight cylindrical portion 3a serving as a portion to be gripped by the main shaft of the machine tool, and a truncated conical portion 3b on the distal end side of the cylindrical portion 3a, the diameter of which gradually decreases. . That is, the shank portion 3 is a portion where the columnar portion 3a and the truncated conical portion 3b are combined. The distal end side of the truncated conical portion 3 b has the same diameter as the base end side of the neck lower part 2 and is connected to the neck lower part 2.

  The neck lower part 2 is located on the tip side of the shank part 3. The neck lower part 2 is tapered. The neck lower part 2 is an area facing a processing surface formed by contour processing using the end mill 1. The length from the boundary between the shank portion 3 and the neck lower portion 2 to the tip of the end mill 1 is the length L of the neck lower portion 2. In the present embodiment, the length L of the neck lower portion 2 is, for example, 17 mm.

The neck lower portion 2 is provided with a blade portion 20 located on the distal end side (ie, on the side opposite to the shank portion 3) and a neck portion 10 located on the base end side (ie, between the blade portion 20 and the shank portion 3). Have been. In the lower neck portion 2, the length from the boundary between the neck portion 10 and the blade portion 20 to the tip is the length N of the blade portion 20. In the present embodiment, the length N of the blade portion 20 is, for example, 4 mm. The blade 20 and the neck 10 both have a tapered shape. The taper angle θ20 of the blade portion 20 and the taper angle θ10 of the neck portion 10 match each other. The taper angle θ20 of the blade 20 and the taper angle θ10 of the neck 10 are, for example, 0.5 °.
The taper angle θ20 of the blade portion 20 can be rephrased as a taper angle of the outer peripheral blade 21a described later. That is, in this specification, the taper angle θ20 of the blade portion 20 refers to an angle formed between the axis O and a common tangent of the plurality of outer peripheral blades 21a arranged along the axis O when the end mill 1 is viewed from the side. I do.

  The blade portion 20 is formed in a tapered tapered shape that becomes thinner toward the tip end side of the end mill 1 along the axial direction, a spherical portion 23 located at the tip of the core thick portion 22, 22 and a cutting edge 21 provided on the outer periphery of the spherical portion 23.

  The cutting blade 21 is divided into an outer peripheral blade 21 a located on the outer peripheral surface of the tapered core portion 22 and a bottom blade 21 b located on the outer peripheral surface of the spherical portion 23. That is, the blade portion 20 has the outer peripheral blade 21a and the bottom blade 21b. The outer peripheral blade 21a extends spirally along the axial direction. Four outer peripheral blades 21 a are provided on the blade portion 20. The four outer peripheral blades 21a are arranged at equal intervals along the circumferential direction. The bottom blade 21b extends in the radial direction on the outer peripheral surface of the spherical portion 23. Two bottom blades 21 b are provided on the blade portion 20. The two bottom blades 21b are arranged at equal intervals along the circumferential direction. That is, the blade part 20 is located at the tip of the core thick part 22, the tapered core thick part 22, four outer peripheral blades 21a located on the outer periphery of the core thick part 22 and extending spirally along the axial direction. And two bottom blades 21b located on the outer periphery of the spherical portion 23.

  The outer peripheral blade 21a extends spirally along the axial direction. The outer peripheral edge 21 a is spirally twisted at a constant twist angle φ toward the opposite side to the tool rotation direction T from the distal end surface of the end mill 1 toward the proximal end side.

  As shown in FIG. 4, two of the four outer peripheral blades 21a are smoothly continuous with the bottom blade 21b. Further, the remaining two outer peripheral blades 21a are not continuous with the bottom blade 21b and are interrupted near the front end. Of the four cutting blades 21, two cutting blades 21 having an outer peripheral blade 21a and a bottom blade 21b continuous with the outer peripheral blade 21a are called master blades 21A, and two cutting blades 21 having no bottom blade 21b. Is called a child blade 21B. The master blades 21A and the child blades 21B are alternately arranged in the circumferential direction.

  Here, the outer peripheral blade 21a of the master blade 21A is referred to as a first outer peripheral blade 21aa, and the outer peripheral blade 21a of the child blade 21B is referred to as a second outer peripheral blade 21ab. The first outer peripheral blade 21aa is continuous with the bottom blade 21b. In addition, the second outer peripheral blade 21ab is disposed between the first outer peripheral blades 21aa in the circumferential direction.

  In the present embodiment, a tapered surface 27 is provided at a boundary between the second outer peripheral blade 21ab and the spherical portion 23. The tapered surface 27 is a flat surface that is inclined toward the axis O toward the distal end. The tapered surface 27 is formed, for example, by grinding. The taper angle α of the tapered surface 27 is larger than the taper angle θ20 of the outer peripheral blade 21a. In the present embodiment, the tapered surface 27 is a flat surface. However, the tapered surface 27 may be a curved surface. In this case, the taper angle α of the tapered surface 27 is a tangential angle on the tip end side of the tapered surface 27. Further, the tapered surface 27 may be a part of a polyhedron composed of a plurality of surfaces arranged in the axial direction. In this case, the taper angle α of the tapered surface 27 is the taper angle of the surface located at the most distal end side of the polyhedron.

FIG. 5 is a side view of the vicinity of the tip of the end mill 1 of the present embodiment.
As shown in FIG. 5, the provision of the tapered surface 27 removes the end of the second outer peripheral blade 21ab. In the end mill without the tapered surface 27, a sharp corner 26V (indicated by a two-dot chain line in FIG. 5) protruding radially outward of the axis O is formed at the end of the second outer peripheral blade. . Such a corner portion 26V may be a factor that causes a step when the wall surface is processed by the end mill. According to the present embodiment, by providing the tapered surface 27, the base corner 26V is removed, and a new corner 26 is formed at the boundary between the tapered surface 27 and the second outer peripheral blade 21ab. be able to. The new corner 26 is located closer to the base end than the base corner 26V, and is less sharp than the base corner 26V. As a result, it is possible to suppress the occurrence of a step on the processing surface by the end mill 1.

  The angle difference AD between the taper angle α of the tapered surface 27 and the taper angle θ20 of the outer peripheral blade 21a is 10 ° or less. By setting the angle difference AD to 10 ° or less, the blade length of the second outer peripheral blade 21ab can be sufficiently ensured. For the same reason, the angle difference AD is more preferably set to 6 ° or less. Further, the angle difference AD is preferably set to 1 ° or more. By setting the angle difference AD to 1 ° or more, the sharpness of the corner portion 26 can be sufficiently dulled, and the occurrence of a step on the processing surface by the end mill 1 can be suppressed.

  As shown in FIG. 1, a chip discharge groove 24 is formed between the cutting blades 21. In the present embodiment, four chip discharge grooves 24 are provided at a portion corresponding to the core thick portion 22, and two chips are provided at a portion corresponding to the spherical portion 23. The plurality of chip discharge grooves 24 are formed at equal intervals in the circumferential direction. The chip discharge groove 24 is spirally twisted at a constant twist angle along the axial direction. The twist angle of the chip discharge groove 24 coincides with the twist angle φ of the outer peripheral blade 21a. The chip discharge groove 24 is cut up to the outer periphery of the end mill 1 at the base end of the blade portion 20.

  As shown in FIG. 3, a cutting edge 21 is formed on the edge of the chip discharge groove 24 on the rear side in the rotation direction. That is, the chip discharge groove 24 is located on the rotation direction front side of the cutting blade 21 (the outer peripheral blade 21a and the bottom blade 21b). The wall surface of the chip discharge groove 24 includes a bottom surface 24a and a rake surface 24b.

  The bottom surface 24a is a surface facing radially outward with respect to the axis O in the chip discharge groove 24. The rake face 24b is a wall face in the chip discharge groove 24 that faces the tool rotation direction T. The rake face 24b includes an outer peripheral rake face formed continuously with the outer peripheral blade 21a and a tip rake face formed continuous with the bottom blade 21b.

  The outer peripheral edge 21 a is formed on the outer peripheral surface of the blade portion 20 at the intersection ridge line between the rake face 24 b and the flank 25. The flank 25 is a surface adjacent to the chip discharge groove 24 on the rear side in the rotation direction. The flank 25 extends in a circumferential direction from the outer peripheral blade 21a toward the chip discharge groove 24 at a rear side in the rotation direction of the outer peripheral blade 21a.

  In the present embodiment, the form of the outer peripheral blade 21a is not particularly limited. For example, the flank may be constituted by one step or may be constituted by multiple faces. In addition, it is preferable that the flank 25 is formed in one step from the viewpoint of reducing the amount of uncut material. That is, the flank 25 is preferably a flank of the first-stage eccentric blade without the flank of the second-stage eccentric blade. According to the end mill 1 of the present embodiment, since the flank 25 is a flank of a single-stage eccentric blade, the remaining amount of the work material can be reduced. The flank may be a two-step flank, as shown in a modified example later. By making the flank a two-step flank, it is possible to provide an end mill capable of improving the processing accuracy of the processing surface while increasing the amount of unretained portion as compared with the case of forming a one-step flank.

  The outer peripheral blade 21a is a tapered blade. Therefore, the diameter of the outer peripheral blade 21a decreases toward the distal end along the axis O direction. The rotation locus formed by the rotation of the outer peripheral blade 21a around the axis O is a single conical surface centered on the axis O. In addition, in this specification, the diameter of the cutting blade 21 (the outer peripheral blade 21a and the bottom blade 21b) means the diameter of the rotation locus of the cutting blade 21 in the corresponding portion.

  The bottom blade 21 b has a convex arc shape that is convex toward the outer peripheral side of the end of the end mill 1. In a side view of the end mill 1, a rotation trajectory formed by the rotation of the bottom blade 21b around the axis O is a single hemisphere centered on the center point of the axis O. The diameter of the outer peripheral blade 21a is the smallest at the boundary between the bottom blade 21b and the outer peripheral blade 21a. The minimum diameter D of the outer peripheral blade 21a (see FIG. 2) matches the diameter of the hemispherical surface formed by the rotation locus of the bottom blade 21b.

  In the present embodiment, at the boundary portion 15 between the blade portion 20 and the neck portion 10, the diameter of the neck portion 10 is smaller than the diameter of the outer peripheral blade 21a and larger than the diameter of the core thick portion 22. Since the diameter of the neck portion 10 of the boundary portion 15 is smaller than the diameter of the outer peripheral edge 21a of the boundary portion 15, the interference between the workpiece W and the neck portion 10 can be reliably suppressed in the finishing of the wall surface of the rib groove by contour processing. Further, since the diameter of the neck portion 10 of the boundary portion 15 is larger than the diameter of the core thick portion 22 of the boundary portion 15, the rigidity of the neck portion 10 can be increased as compared with the blade portion 20. Since the neck portion 10 is located on the base end side in the lower neck portion 2, the bending of the lower neck portion 2 can be effectively suppressed by increasing the rigidity of the neck portion 10, and the remaining amount of the work material W on the machined surface is reduced. Can be reduced.

  In the present embodiment, the axial length M of the neck portion 10 is preferably equal to or longer than the axial length N of the blade portion 20. Thereby, the end mill 1 can perform the finish processing of the sufficiently deep rib groove twice or more the length of the blade portion 20. As described above, the neck portion 10 has higher rigidity than the blade portion 20. By making the axial length M of the neck portion 10 longer than the axial length N of the blade portion 20, the rigidity of the neck lower portion 2 can be increased, and the bending of the neck lower portion 2 can be suppressed. Thereby, the uncut amount of the work material W on the processing surface can be reduced.

In the present embodiment, the axial length N of the blade portion 20 is preferably 2 mm or more and 8 mm or less. Further, it is more preferable that the axial length N of the blade portion 20 be 3 mm or more and 6 mm or less.
In the present embodiment, the ratio (N / D) of the axial length N of the blade portion 20 to the diameter D of the tip of the outer peripheral blade 21a is preferably 2 or more and 8 or less. The ratio (N / D) of the axial length N of the blade portion 20 to the diameter D of the tip of the outer peripheral blade 21a is more preferably 3 or more and 6 or less. In the end mill 1 of the present embodiment, the diameter D of the tip of the outer peripheral blade 21a is 1 mm.

  As a comparative example, FIG. 9 is a schematic view of an end mill 901 provided with a blade portion 920 over substantially the entire neck lower portion 902. In the end mill 901 of the comparative example, the length L of the lower neck portion 902 is 17 mm, and the length N of the blade portion 920 is 16 mm. In the end mill 901 of the comparative example, the diameter D at the tip of the outer peripheral blade 921a is 1 mm. Therefore, the ratio (N / D) of the axial length N of the blade portion 920 to the diameter D of the tip of the outer peripheral blade 921a is 16.

  When the wall surface of the rib groove having a depth of 16 mm is finished by contour machining with a cut amount of 0.025 mm in the axial direction using the end mill 901 of the comparative example, the outer peripheral blade and the work material are 640 mm at the upper end of the machined surface. Contact twice. On the other hand, in the vicinity of the lower end of the processing surface (for example, 4 mm above the lower end), the outer peripheral blade comes into contact with the workpiece only 160 times. For this reason, in the finishing processing using the end mill 901 of the comparative example, the remaining amount of the processed surface increases as going downward in the depth direction.

  On the other hand, in the end mill 1 of this embodiment, as shown in FIG. 2, the length N of the blade portion 20 in the axial direction is 8 mm or less (more preferably, 6 mm or less). The ratio (N / D) of the axial length N of the blade portion 20 to the diameter D of the tip of the outer peripheral blade 21a is 8 or less (more preferably 6 or less). For this reason, it is possible to eliminate the non-uniformity of the remaining amount in the depth direction. In other words, according to the method of finishing the wall surface of the rib groove using the end mill 1 of the present embodiment, the amount of unprocessed surface of the workpiece W can be made uniform along the depth direction. When the remaining amount of the machined surface of the workpiece W is uniform along the axial direction, the pass line of the end mill 1 is offset in a direction to decrease the remaining amount, so that the entire remaining amount is reduced. Can be reduced.

  In the end mill 1 of the present embodiment, the blade portion 20 is 2 mm or more (more preferably, 3 mm or more). The ratio (N / D) of the axial length N of the blade portion 20 to the diameter D of the tip of the outer peripheral blade 21a is 2 or more (more preferably 3 or more). For this reason, in the finishing processing of the wall surface of the rib groove by the contour processing, the remaining amount can be sufficiently suppressed, and the step caused by the rough processing can be reliably removed. In addition, if the blade portion is too short, the number of times of contact between the outer peripheral blade and the work material decreases, and there is a possibility that the removal of the step caused by the rough machining may be insufficient.

In the end mill 1 of the present embodiment, the ratio (L / D) of the axial length L of the neck lower part 2 to the diameter D of the tip of the outer peripheral blade 21a is preferably 8 or more and 20 or less. By setting L / D to be 8 or more, it is possible to finish a sufficiently deep rib groove. Further, by setting L / D to 20 or less, the bending of the neck lower portion 2 can be suppressed, and the amount of the workpiece W left behind on the machined surface can be reduced.
In the present embodiment, the diameter of the distal end of the outer peripheral blade 21a is, for example, 1 mm, and the axial length L of the lower neck portion 2 is, for example, 17 mm. Therefore, the L / D of the end mill 1 of the present embodiment is, for example, 17.

  As shown in FIG. 2, an extension surface VS of the tapered outer peripheral edge 21a is defined. The rotation locus of the outer peripheral blade 21a is a tapered conical surface that tapers toward the distal end side. The extension surface VS is a surface that extends the cylindrical surface formed by the rotation locus of the outer peripheral blade 21a toward the base end. Therefore, the extension surface VS is a tapered conical surface.

In the end mill 1 of the present embodiment, the diameter of the tapered neck 10 is preferably 90% or more of the diameter of the extension surface VS at any point in the axial direction.
As an arbitrary point in the axial direction, a point at a distance X from the distal end of the outer peripheral blade 21a (that is, the boundary between the outer peripheral blade 21a and the bottom blade 21b) to the proximal end side is considered.
The diameter D20 of the extension surface VS at the point of the distance X is expressed by the following equation using the diameter D of the tip of the outer peripheral blade 21a and the taper angle θ20 of the outer peripheral blade 21a.
D20 = D + 2Xtan θ20

  It is preferable that the diameter D10 of the tapered neck portion 10 is 90% or more (that is, D10 ≧ 0.9 × D20) with respect to the diameter D20 of the extension surface VS.

When the diameter D of the tip of the outer peripheral blade 21a is 1 mm (D = 1 mm), and the taper angles θ20 and θ10 of the outer peripheral blade 21a and the neck 10 are 0.5 ° (θ10 = θ20 = 0.5 °), the distance X = 10 mm. , The diameters D20 and D10 of the neck portion 10 are approximately as follows.
D20 = 1.174
D10 ≧ 1.056

  Generally, in a taper end mill, the diameter of the core thick portion 22 is set to about 80% of the diameter of the outer peripheral edge. According to the present embodiment, the rigidity of the neck portion 10 is sufficiently increased with respect to the blade portion 20 by setting the diameter D10 of the neck portion 10 to 90% or more of the diameter D20 of the extension surface obtained by extending the outer peripheral blade 21a. Thus, the rigidity of the entire neck lower portion 2 can be increased. Thereby, the uncut amount of the work material W on the processing surface can be reduced.

  In the end mill 1 of the present embodiment, the blade portion 20 has four peripheral blades 21a arranged in the circumferential direction. It is preferable that four or more outer peripheral blades 21a are provided on the blade portion 20. By increasing the number of the outer peripheral blades 21a, the number of times of contact of the outer peripheral blade 21a with the workpiece W increases. As described above, since the number of contacts between the work material W and the outer peripheral blade 21a affects the remaining amount, by setting the number of the outer peripheral blades 21a to four or more, the remaining amount can be reduced, and rough machining can be performed. Can be effectively removed. In addition, it is most preferable that the number of the outer peripheral blades 21a is four from the viewpoint of sufficiently securing the width of the chip discharge groove 24.

  In the end mill 1 of the present embodiment, the twist angle φ (see FIG. 1) of the outer peripheral blade 21a is preferably set to 40 ° or more. When the twist angle φ of the outer peripheral edge 21a is set to 40 ° or more, the remaining amount can be reduced, and the step caused by the roughing can be sufficiently removed. Note that the twist angle is more preferably set to 50 ° or less. By setting the torsion angle to 50 ° or less, occurrence of chatter vibration during processing using the end mill 1 can be suppressed.

  In this embodiment, the case where the end mill 1 is used for finishing the wall surface of the rib groove has been described. However, the end mill 1 may be used for roughing the wall surface of the rib groove. In this case, the step of the wall surface (rough processing surface) after the rough processing can be reduced, and as a result, the remaining amount of the wall surface (finished processing surface) after the finishing processing can be made uniform in the depth direction. .

(Modification)
Next, an end mill 201 according to a modified example of the above-described embodiment will be described.
FIG. 6 is a schematic cross-sectional view schematically showing an enlarged cross section orthogonal to the axis O of the outer peripheral blade 221a of the end mill 201 of the present modification. In FIG. 6, a work material cut by the outer peripheral blade 221a is schematically illustrated.

  The outer peripheral blade 221a of the present modification has two flank surfaces. That is, the flank 225 of the outer peripheral blade 221a has the first region 225a and the second region 225b arranged along the circumferential direction. The first region 225a is located on the outer peripheral blade 221a side. The second area 225b is located on the chip discharge groove 24 side. Each of the first region 225a and the second region 225b has a circular shape that is eccentric to an imaginary circle centered on the axis O in the cross section of the end mill 201, respectively. The first region 225a and the second region 225b are formed in mutually different eccentric circular shapes. In the flank 225 of the outer peripheral blade 221a, the clearance angle β of the first region 225a is, for example, 4 °, and the clearance angle γ of the second region 225b is, for example, 11 °. That is, the clearance angle γ of the second region 225b is larger than the clearance angle β of the first region 225a.

  According to the present modified example, since the outer peripheral edge 221a is formed of a two-step flank, the outer peripheral edge 221a has a small flank (first region 225a) on the processing surface at the time of cutting. Contact and rub the work surface of the work material. Thereby, the scratches and irregularities formed on the processing surface can be smoothed, and the processing surface accuracy can be improved.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

  In this test, a rib groove (depth 4 mm, bottom width of the rib groove 0.75 mm, inclination angle of the rib groove 1.0 °) is machined by using a taper end mill having a tip diameter of φ0.6 mm. In this test, NAK80 which is a typical plastic mold steel was used as a work material.

  In this test, first, rough machining was performed based on the tool M and the machining conditions shown in Table 1, and further, using the tool Q, the tool N, the tool O, and the tool P, respectively, Comparative Example 1, Comparative Example 2, and Example The finishing process of Example 1 and Example 2 was performed. That is, the rough machining using the tool M is performed before the finish machining of the comparative examples 1 and 2 and the examples 1 and 2.

  Table 1 summarizes the tapered end mills to be used in this test. The angle difference AD in Table 1 corresponds to the angle difference AD between the taper angle α of the tapered surface 27 and the taper angle θ20 of the outer peripheral edge 21a in FIG. The twist angle of each end mill is 40 °, and the flank of the outer peripheral edge is a two-step flank.

The tool M (for rough machining) and the tools N, O, and P (for finish machining of Comparative Example 2, Examples 1 and 2) have an axial direction of the blade portion with respect to the tip diameter (ie, the diameter of the tip of the outer peripheral blade). The length ratios are all about 5.3, and fall within a range of 2 or more and 8 or less.
On the other hand, for the tool Q (for finishing in Comparative Example 1), the ratio of the axial length of the blade portion to the tip diameter is about 8.3, which is out of the range of 2 or more and 8 or less. I have.

  The tool M (for roughing), the tool Q (for finishing in Comparative Example 1), and the tool N (for finishing in Comparative Example 2) are not provided with a tapered surface. Therefore, the tools M, Q, and N are provided with sharp corners 26V shown in FIG. The angle difference (angle difference ADV in FIG. 5) between the surface of the tools M, Q, and N connected to the tip of the outer peripheral blade and the taper angle of the outer peripheral blade is 20 °. In the tools M, Q, and N, the axial distance from the end of the end mill to the lower end of the second outer peripheral edge is about 0.47 mm.

  The tool O (for finishing in Example 1) and the tool P (for finishing in Example 2) are provided with a tapered surface at the boundary between the second outer peripheral blade and the spherical portion.

  The tool O of the first embodiment is provided with a tapered surface having an angle difference AD of 2 °. In the tool O, the axial distance from the end of the end mill to the lower end of the second outer peripheral edge is 1.12 mm.

The tool P of the second embodiment is provided with a tapered surface having an angle difference AD of 4 °. In the tool P, the axial distance from the end of the end mill to the lower end of the second outer peripheral edge is 0.88 mm.

FIG. 7 is a graph showing the measurement results of the remaining amount of the finished working surfaces of Comparative Examples 1 and 2 and Examples 1 and 2.
Under the processing conditions of Comparative Example 2 and Examples 1 and 2, the amount of residue was sufficiently reduced by the finishing, and no large difference was observed in the amount of residue. The maximum height (Rz) of the processed surface of Comparative Example 2 was 0.60 μm, the maximum height (Rz) of the processed surface of Example 1 was 0.56 μm, and the processed surface of Example 2 was Has a maximum height (Rz) of 0.51 μm.
On the other hand, under the processing conditions of Comparative Example 1, it was confirmed that the unretained amount was large even after the finish processing. This may be because the rigidity of the blade portion was insufficient because the ratio of the axial length of the blade portion to the tip diameter exceeded 8.

  FIG. 8A is a photograph of a processed surface (finished processed surface) after finishing in Comparative Example 2. FIG. 8B is a photograph of the finished processed surface of Example 1. FIG. 8C is a photograph of the finished processed surface of Example 2.

  As shown in FIG. 8A, horizontal streaks as minute steps were observed on the finished surface of Comparative Example 2. The horizontal streak corresponds to the axial position of the lower end of the second outer peripheral edge of the tool N. From this, it is considered that a step occurs due to the corner at the lower end of the second outer peripheral blade of the tool N (corresponding to the corner 26V in FIG. 5). Although not shown, horizontal streaks were observed at the same position on the rough machined surface after the rough machining using the tool M and also on the finished machined surface using the tool Q.

  On the other hand, as shown in FIG. 8B and FIG. 8C, the horizontal streaks observed after the rough machining are removed from the finish machining surfaces of the first and second embodiments, and furthermore, at the position corresponding to the lower end of the outer peripheral blade. No horizontal streak was observed. For this reason, by providing a tapered surface at the boundary between the second outer peripheral blade and the spherical portion, it is possible to suppress the occurrence of horizontal streaks at a position corresponding to the lower end of the second outer peripheral blade on the finishing surface. And a more excellent processed surface can be formed.

  The embodiments and examples of the present invention have been described above. However, each configuration in the embodiments and the examples and their combinations are merely examples, and additions and omissions of the configurations may be made without departing from the gist of the present invention. , Substitutions and other changes are possible. The present invention is not limited by the embodiments.

  DESCRIPTION OF SYMBOLS 1 ... End mill, 2 ... Neck lower part, 3 ... Shank part, 9 ... Machine tool, 10 ... Neck part, 15 ... Boundary part, 20 ... Blade part, 21a ... Outer peripheral blade, 21aa ... First outer peripheral blade, 21ab ... Second Outer peripheral blade, 21b: bottom blade, 22: thick part, 23: spherical part, 24: chip discharge groove, 25: flank, 27: tapered surface, AD: angle difference, D, D10, D20: diameter, G ... Rib groove, L ... Length in the axial direction of the lower part of the neck, M ... Length in the axial direction of the neck, N ... Length in the axial direction of the blade part, O ... Axial axis, VS ... Extended surface, α, θ10, θ20 ... taper angle, φ ... twist angle

Claims (16)

A method of processing a wall surface of a rib groove using a taper end mill that rotates along an axis,
The taper end mill has a shank portion held by a machine tool, and a lower neck portion located on a tip side of the shank portion,
In the lower part of the neck, a tapered blade portion, and a tapered neck portion that is located on the base end side of the blade portion and whose axial length is equal to or longer than the axial length of the blade portion, are provided.
The blade portion includes a tapered core portion, a spherical portion located at the tip of the core portion, an outer peripheral blade that is located on the outer periphery of the core portion and extends spirally along the axial direction, And a bottom blade located on the outer peripheral surface of the portion,
At the boundary between the blade portion and the neck portion, the diameter of the neck portion is smaller than the diameter of the outer peripheral blade, and larger than the diameter of the core thick portion,
The ratio of the axial length of the blade portion to the diameter of the tip of the outer peripheral blade is 2 or more and 8 or less,
The outer peripheral blade,
A first outer peripheral blade connected to the bottom blade;
A second outer peripheral blade disposed between the first outer peripheral blades in the circumferential direction;
At the boundary between the second outer peripheral blade and the spherical portion, a tapered surface is provided which is inclined toward the axial line toward the distal end,
The taper angle of the tapered surface is larger than the taper angle of the outer peripheral blade,
Perform contour processing using the taper end mill,
The method of processing the wall surface of the rib groove. The angle difference between the taper angle of the tapered surface and the taper angle of the outer peripheral blade is 10 ° or less.
The method for processing a wall surface of a rib groove according to claim 1. Perform the finishing process of the wall surface of the rib groove with a minute step,
The method for processing the wall surface of a rib groove according to claim 1 or 2. The cut amount in the axial direction is set to 0.025 mm or more,
The method for processing a wall surface of a rib groove according to claim 3. The ratio of the axial length of the lower part of the neck to the diameter of the tip of the outer peripheral blade is 8 or more and 20 or less.
The method for processing a wall surface of a rib groove according to any one of claims 1 to 4. At any point in the axial direction, the diameter of the tapered neck is at least 90% of the diameter of the extension surface of the tapered outer peripheral edge,
A method for processing a wall surface of a rib groove according to any one of claims 1 to 5. The blade portion has four or more outer peripheral blades arranged in a circumferential direction,
The method for processing a wall surface of a rib groove according to any one of claims 1 to 6. The blade portion is provided with a chip discharge groove located between the outer peripheral blades in the circumferential direction and spirally extending along the axial direction, and a flank extending from the outer peripheral blade to the chip discharge groove in the circumferential direction. And
The flank is a series of one-step flank;
A method for processing a wall surface of a rib groove according to any one of claims 1 to 7. The blade portion is provided with a chip discharge groove located between the outer peripheral blades in the circumferential direction and spirally extending along the axial direction, and a flank extending from the outer peripheral blade to the chip discharge groove in the circumferential direction. And
The flank is a two-step flank,
A method for processing a wall surface of a rib groove according to any one of claims 1 to 8. A tapered end mill extending along an axis,
A shank portion held by a machine tool, and a lower neck portion located at a tip end side of the shank portion,
In the lower part of the neck, a tapered blade portion, and a tapered neck portion that is located on the base end side of the blade portion and whose axial length is equal to or longer than the axial length of the blade portion, are provided.
The blade portion includes a tapered core portion, a spherical portion located at the tip of the core portion, an outer peripheral blade that is located on the outer periphery of the core portion and extends spirally along the axial direction, And a bottom blade located on the outer peripheral surface of the portion,
At the boundary between the blade portion and the neck portion, the diameter of the neck portion is smaller than the diameter of the outer peripheral blade, and larger than the diameter of the core thick portion,
The ratio of the axial length of the blade portion to the diameter of the tip of the outer peripheral blade is 2 or more and 8 or less,
The outer peripheral blade,
A first outer peripheral blade connected to the bottom blade;
A second outer peripheral blade disposed between the first outer peripheral blades in the circumferential direction;
At the boundary between the second outer peripheral blade and the spherical portion, a tapered surface is provided which is inclined toward the axial line toward the distal end,
The taper angle of the tapered surface is larger than the taper angle of the outer peripheral blade,
Taper end mill. The angle difference between the taper angle of the tapered surface and the taper angle of the outer peripheral blade is 10 ° or less.
The tapered end mill according to claim 10. The ratio of the axial length of the lower part of the neck to the diameter of the tip of the outer peripheral blade is 8 or more and 20 or less.
The tapered end mill according to claim 10. At any point in the axial direction, the diameter of the tapered neck is at least 90% of the diameter of the extension surface of the tapered outer peripheral edge,
The tapered end mill according to any one of claims 10 to 12. The blade portion has four or more outer peripheral blades arranged in a circumferential direction,
A tapered end mill according to any one of claims 10 to 13. The blade portion is provided with a chip discharge groove located between the outer peripheral blades in the circumferential direction and spirally extending along the axial direction, and a flank extending from the outer peripheral blade to the chip discharge groove in the circumferential direction. Have been
The flank is a series of one-step flank;
The tapered end mill according to any one of claims 10 to 14. The blade portion is provided with a chip discharge groove located between the outer peripheral blades in the circumferential direction and spirally extending along the axial direction, and a flank extending from the outer peripheral blade to the chip discharge groove in the circumferential direction. And
The flank is a two-step flank,
The tapered end mill according to any one of claims 10 to 15.