JPH1158119A - Cemented carbide solid ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cemented carbide solid ball end mill capable of cutting a hardened high hardness material which is a hardly machinable material at high speed and high load without blade chipping or work chipping. SOLUTION: A cemented carbide solid ball end mill comprises an approximately semi-spherical ball part 1 having cutting edges 4 which are approximately S-shaped ad symmetrical when viewed from a tip, and a body 2 having a shank 3 on the other end continuous to the ball part. The cutting blade is formed only on the ball part, the cutting edge is formed from the tip of the ball part, and a terminating end of the cutting edge is up to a boundary part 5 between the ball part and the body. The rake angle 12 of the cutting edge is preferably 0-10 deg., and the clearance angle 13 is 6-6 deg., and a titanium-aluminum nitride hard film is covered 17 on the cutting edge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of a solid carbide ball end mill.

[0002]

2. Description of the Related Art A conventional solid carbide ball end mill is, for example, as disclosed in Japanese Patent Laid-Open No. 6-218613, in which a substantially hemispherical ball portion provided with a cutting edge at an end thereof and an outer periphery formed with an outer peripheral blade are provided. And a body having a cylindrical or conical shank at the rear end. Each tip cutting edge forms a symmetrical 2-flute or 4-flute when viewed from the tip, each has a positive rake angle, and the cutting edge further extends to the outer periphery of the end mill and has an outer diameter of 0.5 to 0.5 mm. An outer peripheral blade about three times as long is formed. Further, the surface is often coated with a hard material such as titanium aluminum nitride (TiCN). Such solid carbide ball end mills are frequently used for three-dimensional machining of dies, and higher speed and higher load cutting are required.

[0003]

However, dies and the like are generally difficult-to-cut materials using hardened high-hardness materials.
For this reason, if finishing is performed at a high efficiency such as high speed and high load, there is a problem that the solid carbide ball end mill may cause chipping of the blade or lack processing accuracy.

[0004] The object of the present invention is to achieve more efficient cutting,
It is another object of the present invention to provide a solid carbide ball end mill capable of cutting hardened hardened materials, which are difficult to machine, with higher speed and higher load.

[0005]

Therefore, as a result of research, the present inventor has found that the lack of machining accuracy of a solid carbide ball end mill and the cause of chipping are caused by the fact that the end grooves extending up to the outer peripheral portion have a long cutting edge and a high rigidity. And / or that the rake angle is positive and that the blade is likely to chip. Furthermore, in three-dimensional machining such as die machining, the ball end mill focuses on the fact that the outer peripheral blade is hardly used, and the rigidity is remarkably improved if the cut-off of the groove forming the cutting edge is made extremely short and the outer peripheral blade is eliminated. I learned to improve.

[0006] By these knowledge, in the present invention,
A substantially hemispherical ball portion on which a substantially S-shaped symmetrical cutting edge is formed as viewed from the tip, a main body having a shank at the other end and the other end where the outer peripheral edge is not formed following the ball portion, and A cemented carbide solid ball end mill, wherein the cutting edge is formed only in the ball portion, and the cutting edge is formed from the tip of the ball portion, and the end of the cutting edge is at most the vicinity of the boundary between the ball portion and the main body. The above-mentioned problem has been solved by providing a solid carbide ball end mill having a high hardness.
The length of the cutting edge is set to a length required for a mold surface to be machined.

Preferably, for the same reason, the blade angle of each cutting edge measured in the same manner is set to 80 ° to 90 ° (FIG. 3).
(b) Reference numeral 16). That is, the angle from the ball tip to the boundary between the ball and the main body is 90 ° with respect to the center of the ball.
Then, the end position of the cutting edge is set at an angle of 80 to 90
° is preferred. More preferably, if each cutting edge has a positive rake angle, chipping is likely to occur and the life is shortened, and if each cutting edge has a rake angle of -10 ° or less, sharpness is reduced, so that each cutting edge has The rake angle is 0 ° ~
-10 degrees. When the clearance angle of each cutting edge is 6 ° or less, the cutting heat rises and the life is shortened. When the clearance angle is increased, the sharpness is improved. However, when the clearance angle exceeds 16 °, chipping tends to occur. Since the angle is set to 16 to 16 degrees, chipping hardly occurs and cutting can be performed with higher efficiency. The rake angle and clearance angle of each cutting edge pass through a line passing through the center of the ball portion and at an angle of 45 ° to the axis of the main body (FIG. 3).
Cross section of the cutting edge along the BB line in FIG.
(b)) is measured.

Further, since high heat is generated when cutting a high-hardness material, the heat resistance and welding resistance of a TiCN-based hard film are inferior. Therefore, titanium aluminum nitride (TiAlN) is used at the cutting edge.
Coating the surface of the system hard film.

[0009]

Embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows an embodiment of the present invention.
Side view of single-blade solid carbide ball end mill, Fig. 2 (a)
FIG. 2B is an enlarged top view of the front end portion from the direction of arrow A in FIG. 1, FIG.
FIG. 3 is an enlarged front view of the tip portion viewed from the direction of arrow C in FIG. As shown in a side view of a two-blade solid carbide ball end mill showing an embodiment of the present invention in FIG. 1, a ball end mill of the present invention has a hemispherical ball portion 1 and a ball portion 1.
And a cylindrical body 2 having a shank 3 at the other end.
As can be seen from FIG. 2 (b), two cutting edges 4, 4 are formed on the hemispherical ball portion 1, and the cutting edges 4, 4 are formed on the ball portion 1.
Up to the boundary 5 between the body 2 and the axis 10 of the body 2
It is formed over an angle of °, no more, and does not have a peripheral edge hanging from it as in the prior art.

That is, in FIG. 1, since the outer diameter 6 of the ball portion 1 and the outer diameter 7 of the outer peripheral portion 2 'of the main body 2 are the same,
The cutting edge 2 is formed only in the hemispherical portion of the ball portion 1. For this reason, as shown in FIG. 2A, the length 9 of the cutting edge groove 8 necessary for forming the cutting edge 4 is formed very short, and the rigidity is greatly improved.

As shown in FIG. 2B, the cutting edge 4 is formed in a substantially S-shaped symmetrical shape when viewed from the tip of the cutting edge 4. The cutting edge 4 has a continuously changing twist angle in contact with the S-shaped cutting edge 4. 3 (a), which is a side view in which the tip portion of FIG. 1 is enlarged, and FIG. 3 (b), which is a partially enlarged cross-sectional view showing a cross section taken along line BB of the blade portion 4 in FIG. 3 (a). As shown, 14 is a rake face and 15 is a flank face. As shown in FIG. 3 (b), the rake angle 12 and the clearance angle 13 of each cutting edge 4 pass through the center 20 of the ball portion and are at 45 ° to the axis 10 of the main body 2.
Is measured at the cross section of the cutting edge 4 along the line of the angle (BB line in FIG. 3A, reference numeral 21). In this embodiment, the rake angle 12
Is set to a negative value of −10 °, the clearance angle 13 is set to 12 °, and the blade angle is set to 88 °. Preferably, the blade angle 16 is 80 °
To 90 °, the rake angle 12 is made negative from 0 ° to -10 °, the clearance angle 13 is made to 6 ° to 16 °, and the blade angle 16 is 8
0 ° to 90 °.

As shown in FIG. 1, a titanium aluminum nitride hard film is partially coated from the ball portion 1 to a range 17 of the main body 2 beyond the boundary portion 5, and at least the entire cutting edge 4 is coated with the titanium aluminum nitride hard film. Coated.

[0013]

EXAMPLE A high-speed finishing was performed using a two-blade solid carbide ball end mill shown in FIG. 1 and a comparison test with a conventional product was performed. The rake angle of the tested ball blade of the present invention,
The clearance angle and the blade angle are -10 ° and 12 respectively.
°, 88 °, the outer diameter of the cutting edge is 10 mm, and each cutting edge is coated with a titanium aluminum nitride hard film. The compared conventional product is a two-blade solid carbide ball end mill having a cutting edge up to the outer peripheral portion. Both the cutting edge of the ball portion and the outer peripheral edge are coated with a TiCN hard film, and the rake angle, clearance angle of the ball blade, and the cutting tool Angles are 6 ° and 14 respectively
° and 70 °, and the cutting edge outer diameter is 10 mm.

The test method is to attach the product of the present invention and the conventional product to a vertical machining center, and to rotate at 12,000 RPM,
Feed speed 2,400 mm / min, axial depth of cut a
_a = 0.15 mm, pick feed P _f = 0.3 mm,
Under the condition of down-cut 30 ° contour cutting (cut the processing surface inclined at 30 ° to the end mill axis in the lateral direction of the slope), using a water-soluble cutting oil, hardened high hardness steel SKD1
1 (60HRC) was cut.

FIG. 6 shows the result. FIG. 6 shows the measurement of the wear width of the flank 15 of the cutting edge 4 of the ball portion 1 with respect to the cutting length (m). As shown in FIG. 6, the wear width of the conventional two-blade solid carbide ball end mill is 280 μm at a cutting length of 20 m, whereas the wear width of the present invention is 170 μm, which is smaller than that of the conventional product. It has been reduced by about 40%. Further, although chipping occurs in the conventional product, chipping does not occur in the product of the present invention, and a longer life can be expected. In the embodiment, a two-flute super hard solid ball end mill has been described, but it goes without saying that the present invention can be applied to a four-flute blade or the like.

[0016]

As described above, in the present invention, a substantially hemispherical ball portion having a substantially S-shaped symmetrical cutting edge formed from the tip and a shank at the other end following the ball portion are provided. In a solid carbide ball end mill consisting of a main body having a cutting edge, the cutting edge is formed only in the ball portion, and the end of the cutting edge is set to be near the boundary between the ball portion and the main body even at the maximum, so that the blade groove length is A solid carbide ball end mill that can reduce hardened hardened materials, which are difficult to cut, with higher speed and higher load without cutting chips due to insufficient rigidity, significantly improving rigidity, cutting edges due to insufficient rigidity, and lowering processing accuracy. To provide.

Further, the rake angle of the cutting edge is 0 ° to -10.
° and the clearance angle are 6 ° to 16 °, so that chipping hardly occurs and cutting can be performed more efficiently.

Furthermore, since each cutting edge is preferably coated with a titanium-aluminum nitride-based hard film, heat resistance and welding resistance are increased and cutting can be performed with higher efficiency. In addition, since the cutting edge and the surface coating only need to be at the tip end, that is, the ball portion, there is an effect other than the cutting performance that it is inexpensive because there is no outer peripheral edge as in the conventional product, and that re-grinding becomes easy. became.

[Brief description of the drawings]

FIG. 1 is a side view of a two-blade solid carbide ball end mill showing an embodiment of the present invention.

2 (a) is an enlarged top view of the tip portion viewed from the direction of arrow A in FIG. 1, and FIG. 2 (b) is an enlarged front view of the tip portion viewed from the direction of arrow C in FIG. 2 (a). is there.

3 (a) is an enlarged side view of the tip portion of FIG. 1, and FIG. 3 (b) passes through the center of the ball portion of FIG. 3 (a) and is at 45 ° to the axis of the main body. It is a partial expanded sectional view showing a section of a cutting edge along an angle line (BB line).

FIG. 4 shows a comparison test result between the product of the present invention and a conventional product.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ball part 2 Main body 3 Shank 4 Cutting edge 5 Boundary part 8 Cutting edge groove 10 Body axis 12 Rake angle 13 Relief angle 17 Surface coating of titanium nitride aluminum hard film 20 Center of ball part 21 Passing through center of ball part Line at an angle of 45 ° to the body axis (BB line)

Claims (3)

[Claims] 1. A solid cemented carbide comprising: a substantially hemispherical ball portion formed with a substantially S-shaped symmetrical cutting edge as viewed from the tip; and a main body having a shank at the other end following the ball portion. In the ball end mill, the cutting edge is formed only on the ball portion, and the cutting edge is formed from the tip of the ball portion, and the end of the cutting edge is at most the boundary portion between the ball portion and the main body. A solid carbide ball end mill characterized by the following. 2. A rake angle of the cutting edge measured at a cross section of the cutting edge passing through a center of the ball portion and along a line at an angle of 45 ° with respect to an axis of the main body, and a rake angle of the cutting edge is 0 ° to −10 °, 2. The solid carbide ball end mill according to claim 1, wherein the clearance angle is 6 [deg.] To 16 [deg.]. 3. The solid carbide ball end mill according to claim 1, wherein said cutting edge is coated with a titanium nitride-based hard film.