JP2023150313A - radius end mill - Google Patents

Abstract

To provide a radius end mill capable of improving, processed surface quality of a finished surface of a cut object, and improving processing dimension accuracy of the cut object.SOLUTION: There is provided a radius end mill 1 which has a cutting blade 20 on a tip side of a tool main body 10 which can rotate around, a rotary axis line O1, the cutting blade comprises: a first bottom blade corner part 22 which is formed on a tip end face 20a of the cutting blade and at outside of the tool main body in a radial direction, and in which a first bottom blade angle is 0° or greater; a second bottom blade corner part 23 which is formed inside of the radial direction relative to the first bottom blade corner part on the cutting blade, and in which a second bottom blade angle is greater than the first bottom blade angle; and a plurality of R blades 24 which is formed on the tip end face of the cutting blade part. A spiral angle α1 of a gash surface 20b on the plurality of cutting blade parts, gradually becomes greater, as advancing to a base end side.SELECTED DRAWING: Figure 1

Description

The present invention relates to a radius end mill.

Conventionally, in the field of precision machining, radius end mills have been used to cut molds, parts, etc. (see, for example, Patent Document 1).
For example, in a radius end mill, an R blade having a radius R and a 1/4 arc shape is formed at the outer peripheral corner of the cutting edge.
When cutting with the radius end mill, the R blade cuts the object (work material).

JP 2021-65949 Publication

However, in the conventional radius end mill described in Patent Document 1, there is room for improvement in the machined surface quality (surface roughness) of the finished surface of the workpiece and the machining dimensional accuracy of the workpiece.

The present invention has been made in view of these problems, and an object of the present invention is to provide a radius end mill that improves the quality of the finished surface of a workpiece and improves the dimensional accuracy of the workpiece. With the goal.

In order to solve the above problems, the present invention proposes the following means.
The radius end mill of the present invention is a radius end mill that is provided with a cutting edge on the distal end side of a tool body that is rotatable around a central axis, wherein the cutting edge is a distal end surface of the cutting edge and is formed on the tool body. a first bottom edge corner portion formed radially outward and having a first bottom edge angle of 0° or more; and a second bottom edge formed radially inwardly than the first bottom edge corner portion in the cutting edge portion. a second bottom edge corner having a larger angle than the first bottom edge angle; and a plurality of R blades formed on the tip surface of the cutting edge, and twisting the gash surface in the cutting edge. The angle is characterized by becoming larger toward the proximal end.

In this invention, the cutting blade rotates around the central axis, and thereby cuts the workpiece using the first bottom edge corner, the second bottom edge corner, and the R blade of the cutting edge. In this case, the cutting edge portion has a first bottom edge corner portion with a first bottom edge angle of 0° or more, and a second bottom edge corner portion with a second bottom edge angle larger than the first bottom edge angle. Therefore, it is possible to improve the quality of the finished surface of the workpiece, suppress wear at the tip of the cutting edge, and reduce cutting resistance. Therefore, the quality of the finished surface of the workpiece can be improved.
Furthermore, since the helix angle of the gash surface at the cutting edge increases toward the base end, the cutting resistance of the R blade is reduced, the chips generated by the R blade are smoothly discharged, and the workpiece is Machining dimensional accuracy can be improved.

Further, in the radius end mill, the cutting edge portion has an outer circumferential edge formed from the plurality of R blades toward the proximal end side, and includes a flank surface of the second bottom edge corner portion, and a flank surface of the second bottom edge corner portion; The flank face of the corner, one of the flank faces of the plurality of R blades, and the flank face of the peripheral blade may be connected to each other so as to be smoothly continuous.
In this invention, for example, the flank of the second bottom edge corner, the flank of the first bottom edge corner, one of the flanks of a plurality of R blades, and the flank of the peripheral edge are seamlessly processed. It can be manufactured by

Further, in the radius end mill, the R blade may have a length exceeding 1/4 arc from the tip of the cutting edge.
In this invention, manufacturing errors in the arc shape of the R blade can be suppressed, the machining accuracy of the R blade can be improved, and the entire R blade can be formed into a highly accurate arc shape.

In the radius end mill of the present invention, it is possible to improve the machined surface quality of the finished surface of the workpiece by the R blade, and to improve the machining dimensional accuracy of the workpiece.

1 is a side view of essential parts of a radius end mill according to an embodiment of the present invention. It is a front view of the same radius end mill. FIG. 3 is a view taken in the direction of arrow A1 in FIG. 2. FIG. FIG. 2 is a perspective view showing the shape of a protrusion cut out with a radius end mill. It is an example of the comparative diagram of the radius end mill of an Example and a comparative example in finishing processing. It is another example of the comparative diagram of the radius end mill of an Example and a comparative example in finishing processing. It is a comparative diagram of the radius end mill of an example and a comparative example after cutting when alloy tool steel DC53 is used as a cut object.

Hereinafter, one embodiment of a radius end mill according to the present invention will be described with reference to FIGS. 1 to 7.
As shown in FIGS. 1 and 2, for example, the radius end mill 1 of this embodiment is a multi-blade radius end mill (having a plurality of blade portions 21 to be described later). The radius end mill 1 is used to cut, for example, an alloy tool steel (SKD11) or a powdered high-speed tool steel (SKH55, etc.) as a forging die or press die. The radius end mill 1 includes a tool body 10 and a cutting edge portion 20.

Here, the tool body 10 and the cutting edge portion 20 are each formed in a cylindrical shape. The center axes (axes) of the tool body 10 and the cutting edge portion 20 are arranged coaxially with a common axis. Hereinafter, the common axis will be referred to as the central axis O1. In the central axis O1 direction, the side of the cutting edge 20 relative to the tool body 10 is referred to as the distal end side, and the side of the tool body 10 relative to the cutting edge 20 is referred to as the proximal end side. When the radius end mill 1 is viewed along the central axis O1, the direction perpendicular to the central axis O1 is called the radial direction, and the direction of rotation around the central axis O1 is called the circumferential direction. The radial direction is the radial direction of the tool body 10.

The tool body 10 is rotatable around the central axis O1. The base end portion of the tool body 10 is attached to a machine tool such as a machining center (not shown). For example, cemented carbide is preferably used for the tool body 10.

The cutting edge portion 20 is provided on the tip side of the tool body 10. The cutting edge portion 20 has a plurality of (four in this embodiment) blade portions 21. The plurality of blade parts 21 are arranged at equal angles around the central axis O1. When the plurality of blade parts 21 rotate in the rotation direction D1 around the central axis O1, they cut the object to be cut.
As shown in FIG. 3, an imaginary line perpendicular to the central axis O1 on the tip side of the cutting edge portion 20 is defined as a reference line L1. Each blade portion 21 has a first bottom edge corner portion 22 , a second bottom edge corner portion 23 , an R blade 24 , and a peripheral edge 25 . Note that the first bottom edge corner portion 22 , the second bottom edge edge portion 23 , and the R blade 24 are bottom edges of the cutting edge portion 20 .

The first bottom edge corner portion 22 is formed on the tip surface 20a of the cutting edge portion 20, and is formed radially outward from the second bottom edge corner portion 23. The first bottom edge angle θ1 of the first bottom edge corner portion 22 is 0° or more. The first bottom edge angle θ1 is an angle between the tip surface of the first bottom edge corner portion 22 and the reference line L1. It is preferable that the first bottom edge angle θ1 is 2° or less.
The second bottom edge corner portion 23 is formed in the cutting edge portion 20 on the inner side in the radial direction than the first bottom edge corner portion 22 . The second bottom edge corner portion 23 continues inward in the radial direction with respect to the first bottom edge corner portion 22 . The second bottom edge angle θ2 of the second bottom edge corner portion 23 is larger than the first bottom edge angle θ1. The second bottom edge angle θ2 is an angle between the tip surface of the second bottom edge corner 23 and the reference line L1. The second bottom edge angle θ2 is preferably 3° or more and 10° or less.

The R blade 24 is formed in an R shape on the distal end surface 20a of the cutting edge portion 20. As shown in FIG. 1, the twist angle α1 of the gash surface 20b in the cutting edge 20 increases toward the proximal end. As shown in FIG. 3, the gash surface 20b extends from the second bottom blade corner 23, through the first bottom blade corner 22 and the R blade 24, to the base end of a back taper connecting blade 32, which will be described later. It is a surface.
The helix angle (rake angle in the direction of the central axis O1) α1 of the plurality of R blades 24 also increases toward the base end.
A flute groove 31 is formed in the rotation direction D1 of the outer peripheral blade 25 formed on the base end side of the R blade 24. As shown in FIG. 3, the R blade 24 has a base cutting edge 24b and an extended blade 24c.
The base cutting edge 24b is formed into a substantially 1/4 arc shape with a radius R. The tip of the base cutting edge 24b is continuous with the tip surface of the first bottom edge corner portion 22. The extension blade 24c extends from the base end of the base cutting blade 24b toward the base end side while maintaining the radius R. In this way, the R blade 24 having the base cutting edge 24b and the extension edge 24c has a length exceeding 1/4 arc from the tip of the cutting edge portion 20.

The outer peripheral blade 25 is formed from the extended blade 24c of each R blade 24 toward the base end side.
The proximal end of the extended blade 24c and the peripheral blade 25 are connected by, for example, a back taper connecting blade 32 having a linear back taper shape.
As shown in FIGS. 1 to 3, the flank 21a of the blade part 21 is a surface extending from the second bottom blade corner 23, through the first bottom blade corner 22, the R blade 24, and to the outer peripheral blade 25. be. The flank 21 a includes a flank 23 a of the second bottom edge corner 23 , a flank 22 a of the first bottom edge corner 22 , a flank 24 d of the R blade 24 , and a flank 25 a of the peripheral edge 25 . It is preferable that these flank surfaces 23a, 22a, 24d, and 25a are connected to each other in a smooth manner.

As shown in FIG. 2, the plurality of blade portions 21 are formed below the center. Here, the term "center drop" means that the plurality of blade parts 21 do not pass through the central axis O1, but are provided at positions moved in the direction opposite to the rotational direction D1 with respect to the central axis O1.
Note that the plurality of blade portions 21 may be formed with a center upward. The term "centering up" here means that the plurality of blade parts 21 are provided at positions moved in the rotational direction D1 with respect to the central axis O1.

Next, test results using the radius end mill of the example and the radius end mill of the comparative example (conventional) will be explained. Note that the radius end mill of the comparative example does not have the first bottom edge corner portion, unlike the radius end mill of the example.

(1. Verification of machined surface quality of finished surface of workpiece)
Using the radius end mills of Examples and Comparative Examples, the shape of a protrusion 51 as shown in FIG. 4 was cut from a block-shaped workpiece. The protrusion 51 is formed in an X-shape and is arranged on the reference plane 50. The radius end mill has a diameter of 2 mm, a corner radius of 0.2 mm, and an effective length of 6 mm. The object to be cut was made of powdered high-speed tool steel HAP40 (64HRC).
The rotation speed n of the radius end mill in this case was 12,000 revolutions/min. The axial depth of cut a _p is 0.02 mm, the radial depth of cut a _e is 0.05 mm, the feed speed V _f is 1,000 mm/min, and the feed amount per tooth f _z is 0.020 mm/tooth. did. Oil mist was used during cutting.
The workpieces were machined using both radius end mills for 50 minutes each.
The test results are shown in FIG. FIG. 5 shows the result of cutting out the upper surface 51a (see FIG. 4) and wall surface (side surface) 51b of the protrusion 51.

The arithmetic mean roughness Ra when the upper surface 51a was cut with the radius end mill of the comparative example was 0.028 μm (micrometer). The arithmetic mean roughness Ra when the upper surface 51a was cut with the radius end mill of the example was 0.010 μm. The upper surface 51a cut with the end mill of the example had fewer scratches and was in a cleaner state than the upper surface 51a cut with the radius end mill of the comparative example.
The arithmetic mean roughness Ra when the wall surface 51b was cut with the radius end mill of the comparative example was 0.077 μm. The arithmetic mean roughness Ra when the wall surface 51b was cut with the radius end mill of the example was 0.052 μm. The wall surface 51b cut with the radius end mill of the example had fewer scratches and was in a cleaner state than the wall surface 51b cut with the radius end mill of the comparative example.

The processing error amount of the width of the protrusion 51 by the radius end mill of the comparative example was 0.004 mm. The amount of processing error in the width of the protrusion 51 by the radius end mill of the example was 0.003 mm.
The processing error amount of the depth of the protrusion 51 (distance between the reference surface 50 and the upper surface 51a) by the radius end mill of the comparative example was 0.005 mm. The processing error amount of the depth of the protrusion 51 by the radius end mill of the example was 0.002 mm.
It was found that the amount of machining error when cutting with the radius end mill of the example was smaller than the amount of machining error when cutting with the radius end mill of the comparative example.
The reason why the amount of machining error became smaller is considered to be that the radius end mill of the example had a longer life and the R accuracy (corner R accuracy) of the radius end mill became higher.

When cutting with the radius end mill of the comparative example, the burr height at the connection portion between the top surface 51a and the wall surface 51b was 0.006 mm. The burr height of the connection portion when cut with the end mill of the example was 0.004 mm.
It was found that when cutting with the radius end mill of the example, the burr height was suppressed compared to when cutting with the radius end mill of the comparative example.

FIG. 6 shows the wear status of the radius end mills of the example and the comparative example after finishing the protrusion 51. For each radius end mill, photos of the bottom cutter and outer cutter are shown.
In the radius end mill of the comparative example, the flank wear width was 0.026 mm, and the R recession amount was 0.005 mm. In the radius end mill of the example, the flank wear width was 0.023 mm, and the R recession amount was 0.003 mm.
From this result, it was found that in the radius end mill of the example, the wear width of the flank and the amount of R recession were each smaller than that of the radius end mill of the comparative example.

(2. Verification of life during rough machining)
Using the radius end mills of Examples and Comparative Examples, the workpieces were rough-milled. The radius end mill has a diameter of 2 mm, a corner radius of 0.2 mm, and an effective length of 6 mm.
The material forming the cut object was alloy tool steel DC53 (60HRC). Note that the standard for determining the life of a radius end mill is that the wear width of the flank face exceeds 0.15 mm. If the flank wear width exceeds 0.15 mm, cutting with a radius end mill will be difficult.

The test results are shown in FIG. Note that the rotational speed n of the radius end mill in this case was 15,000 revolutions/min (minutes). The axial depth of cut a _p is 0.05 mm, the radial depth of cut a _e is 0.5 mm, the feed speed V _f is 1,800 mm/min, and the feed amount per tooth f _z is 0.03 mm/tooth. did. Oil mist was used during cutting.
In the radius end mill of the comparative example, the wear width of the flank surface became 0.184 mm after cutting time of 110 minutes, and the end mill reached the end of its life.
On the other hand, in the radius end mill of the example, the wear width of the flank face at a cutting time of 110 minutes was 0.062 mm. In the radius end mill of the example, the wear width of the flank surface became 0.150 mm after cutting time of 200 minutes, and the end mill reached the end of its life.

From this result, it was found that the radius end mill of the example had a longer life during rough machining than the radius end mill of the comparative example.

As explained above, in the radius end mill 1 of the present embodiment, the cutting blade part 20 rotates around the central axis O1, so that the first bottom blade corner part 22 and the second bottom blade corner part of the cutting blade part 20 are rotated. 23 and the R blade 24 cut the object to be cut. At this time, the cutting edge portion 20 includes a first bottom edge corner portion 22 in which the first bottom edge angle θ1 is 0° or more, and a second bottom edge portion 22 in which the second bottom edge angle θ2 is larger than the first bottom edge angle θ1. It has a corner 23. Therefore, the machined surface quality of the workpiece can be improved, wear at the tip of the cutting edge portion 20 can be suppressed, and cutting resistance can be reduced. Therefore, the quality of the finished surface of the workpiece can be improved.
Furthermore, since the helix angle α1 of the gash surface 20b in the cutting edge portion 20 increases toward the base end, the cutting resistance of the R blade 24 is reduced, and the chips generated by the R blade 24 are smoothly discharged. , it is possible to improve the machining dimensional accuracy of the workpiece.

The flanks 23a, 22a, 24d, and 25a are connected to each other so as to be smoothly continuous. Therefore, the flanks 23a, 22a, 24d, and 25a can be manufactured by seamless processing.
The R blade 24 has a length exceeding 1/4 arc from the tip of the cutting edge portion 20. Therefore, manufacturing errors in the arc shape of the R blade 24 can be suppressed, the machining accuracy of the R blade 24 can be improved, and the entire R blade 24 can be formed into a highly accurate arc shape.

Although one embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and modifications, combinations, and deletions of the configuration within the scope of the gist of the present invention. etc. are also included.
For example, in the embodiment described above, each blade portion 21 of the radius end mill 1 does not need to have the peripheral blade 25. The length of the R blade 24 may be less than 1/4 arc from the tip of the cutting edge portion 20.

1 Radius end mill 10 Tool body 20 Cutting blade portion 20a Tip surface 20b Gash surface 22 First bottom blade corner portion 22a, 23a, 24d, 25a Flank surface 23 Second bottom blade corner portion 24 R blade 25 Peripheral blade O1 Center axis α1 Torsion Angle θ1 1st bottom edge angle θ2 2nd bottom edge angle

Claims (3)

In a radius end mill that has a cutting edge on the tip side of the tool body that can rotate around the central axis,
The cutting edge portion is
a first bottom edge corner portion that is a tip surface of the cutting edge portion and is formed on the outside in the radial direction of the tool body, and has a first bottom edge angle of 0° or more;
a second bottom edge corner portion that is formed radially inward than the first bottom edge corner portion in the cutting edge portion and has a second bottom edge angle larger than the first bottom edge angle;
a plurality of R blades formed on the tip surface of the cutting edge portion;
has
A radius end mill in which the helix angle of the gash surface in the cutting edge portion increases toward the proximal end. The cutting edge portion has an outer peripheral edge formed toward the base end side from the plurality of R blades,
The flank of the second bottom blade corner, the flank of the first bottom blade corner, one of the flanks of the plurality of R blades, and the flank of the peripheral blade are connected to each other so as to be smoothly continuous. The radius end mill according to claim 1, wherein: The radius end mill according to claim 1 or 2, wherein the R blade has a length exceeding 1/4 arc from the tip of the cutting edge portion.

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