JP6825400B2 - Taper ball end mill - Google Patents

Description

The present invention relates to a tapered ball end mill used for machining a rib groove such as a mold.

As such a tapered ball end mill, for example, Patent Document 1 describes a tapered ball end mill including a tip ball blade (bottom blade), an outer peripheral blade continuous with the tip ball blade, and an outer peripheral blade not continuous with the tip ball blade. Therefore, the total number of outer peripheral blades is an even number of 4 or more, and when viewed from the front of the end mill, a pair of outer peripheral blades at substantially symmetrical positions have two consecutive tip ball blades, and the tip ball blades For the non-continuous outer peripheral blade, the distance between the position of the tip of the outer peripheral blade and the tip of the end mill is the length measured in the axial direction, and 0.05 to 0.5 mm is added to the radius of the ball blade. It has been proposed that the length is set and the core thickness of the radius 45 ° portion of the tip ball blade is 20 to 50% with respect to the blade diameter of the portion.

According to such a tapered ball end mill, the distance between the position of the tip of the outer peripheral blade that is not continuous with the tip ball blade and the tip of the end mill is the length measured in the axial direction, and is the radius of the ball blade. The length added by 0.05 to 0.5 mm, that is, the tip of the outer peripheral blade that is not continuous with the tip ball blade is located closer to the rear end side of the end mill body than the rear end of the tip ball blade, and this outer peripheral blade Since the tip of the blade is deviated from the cutting edge portion where the amount of cutting is large, it is possible to suppress the occurrence of chipping and chipping of the tip of the outer peripheral blade during cutting, and improve the surface roughness of the machined surface and the tool life.

Japanese Patent No. 45733340

By the way, in the rib groove processing by such a tapered ball end mill, reciprocating processing has been the mainstream as described in Patent Document 1, but in recent years, a predetermined axis line is determined by a pick feed set by CAM data. Contour line machining is being adopted in which machining is performed with a tool trajectory that approaches the shape of the workpiece for each depth of direction. Then, in the contour line processing of the rib groove, the outer peripheral portion of the rear end of the hemispherical rotation locus formed by the tip ball blade around the axis of the end mill body is often used for cutting.

However, in the tapered ball end mill described in Patent Document 1, as described above, among the four or more even outer peripheral blades, the outer peripheral blades other than the pair of outer peripheral blades continuous with the two tip ball blades are the tip balls. It is not continuous with the blades, and the outer peripheral portion of the rear end of the hemispherical rotation locus is also formed by the two tip ball blades. For this reason, it is not possible to improve the processing efficiency, and it is also difficult to secure the processing accuracy and the quality of the processed surface, especially in the finishing processing by contour processing.

The present invention has been made under such a background, and provides a tapered ball end mill capable of improving machining efficiency and obtaining high machining accuracy and machined surface quality even in contour line machining of rib grooves and the like. The purpose is.

In order to solve the above problems and achieve such an object, in the present invention, a plurality of chip discharge grooves extending toward the rear end side are formed on the outer periphery of the tip portion of the end mill body rotated around the axis. A cutting edge is formed on the outer peripheral edge of the wall surface of these chip discharge grooves facing the end mill rotation direction, and some of the cutting edges are around the axis at the tip of the end mill body. The center is a hemispherical bottom blade whose rotation locus has a center on the axis, and the axis that extends from the rear end of the bottom blade and gradually expands in diameter as the rotation locus around the axis extends toward the rear end. It is provided with a conical outer peripheral blade, and the remaining cutting blades have a rotation locus around the axis from the rear end outer peripheral portion to the rear end side of the bottom blade rotation locus in some of the cutting blades. It is provided with an auxiliary outer peripheral blade that extends to and overlaps the rotation locus of the outer peripheral blade, and is a hemisphere formed by the intersection of the rotation locus of the tip of the auxiliary outer peripheral blade around the axis and the bottom blade, and the rotation locus of the bottom blade. The straight line connecting the center of the above crosses the axis at the center at an intersection angle within the range of 60 ° to 80 ° .

In the tapered ball end mill configured in this way, among the multiple cutting edges formed on the outer peripheral edge of the wall surface facing the end mill rotation direction of the multiple cutting chip discharge grooves, some of the cutting edges are of the end mill body. A bottom blade (tip ball blade) whose rotation locus around the axis is hemispherical is provided, and the remaining cutting blades are auxiliary outer peripheral blades extending from the rear end outer peripheral portion of the hemisphere formed by the rotation locus of this bottom blade to the rear end side. Therefore, the rear end outer peripheral portion of the rotation locus of the bottom blade is composed of both the bottom blade of some of these cutting blades and the auxiliary outer peripheral blade of the remaining cutting blades. That is, since the number of blades can be increased at the outer peripheral portion of the rear end of the bottom blade, which is often used in contour line machining, it is possible to improve the machining efficiency and obtain high machining accuracy and machined surface quality.

Here, the straight line connecting the intersection of the rotation locus of the tip of the auxiliary outer peripheral blade around the axis with the bottom blade and the center of the hemisphere formed by the rotation locus of the bottom blade is the rear end side of the end mill body. The angle of intersection with the axis of the straight line when it is inclined and intersects the axis at the center in this way is within the range of 60 ° to 80 °. Is desirable. When this crossing angle exceeds the above range and approaches 90 °, the portion of the tip of the auxiliary outer peripheral blade of the remaining cutting blade that overlaps with the bottom blade of some of the cutting blades becomes too short, and is processed during contour line machining. While there is a risk that efficiency, machining accuracy, and machined surface quality cannot be sufficiently improved, if the number is below the above range, especially when the number of cutting edges is large, the chip discharge groove capacity is at the most advanced part of the end mill body. May become smaller, causing chip clogging or insufficient strength.

The rotation locus around the axis of the end mill body is located inside the rotation locus of the bottom blade so as not to interfere with the machined surface formed by the bottom blade on the tip side of the auxiliary outer peripheral blade of the remaining cutting blade. Has been retreated. Here, when the above-mentioned partial cutting edge and the above-mentioned remaining cutting edge are alternately formed in the circumferential direction on the outer periphery of the tip portion of the end mill main body, the auxiliary outer peripheral blade of the remaining cutting edge is formed. The tip side is the flank of the bottom edge of some cutting edges adjacent to the end mill rotation direction of the remaining cutting edge, and some cutting edges adjacent to the opposite side of the end mill rotation direction of the remaining cutting edge. It is desirable that the bottom blade is formed so as to intersect with the gash wall surface and be cut out. By leaving the flank of the bottom blade of some cutting edges at the tip of the end mill body, it is possible to secure the cutting edge strength of the bottom blade at the tip of the end mill body.

As described above, according to the present invention, it is possible to improve the processing efficiency and obtain high processing accuracy and machined surface quality, particularly in contour line processing of rib grooves and the like.

It is a side view which shows one Embodiment of this invention. It is an enlarged side view of the tip part of the embodiment shown in FIG. It is an enlarged front view around the rotation center when the embodiment shown in FIG. 1 is viewed from the tip side in the axial direction.

1 to 3 show an embodiment of the present invention. In the tapered ball end mill of the present embodiment, the end mill body 1 is formed of a hard material such as cemented carbide in a cylindrical shaft shape centered on the axis O as shown in FIG. 1, and is formed on the rear end side (FIGS. 1 and 2). The portion on the right side) is a shank portion 2 that remains cylindrical, and the portion on the tip side (left side in FIGS. 1 and 2) is a cutting edge portion 3. In such a tapered ball end mill, the shank portion 2 is gripped by the spindle of the machine tool and rotated around the axis O in the end mill rotation direction T, while the work material such as a die is subjected to contour line processing to rib. Used to form grooves.

As shown in FIG. 1, the cutting edge portion 3 is formed in a substantially conical outer shape in which the outer diameter gradually decreases toward the tip side, and the end mill rotates on the outer peripheral portion from the tip end side of the end mill body 1 toward the rear end side. A plurality of chip discharge grooves 4 twisting on the side opposite to the direction T are formed. In the present embodiment, the four chip discharge grooves 4 are formed at equal intervals in the circumferential direction. A cutting edge 5 having the wall surface as a rake face is formed on the outer peripheral edge of the wall surface of the chip discharge groove 4 facing the end mill rotation direction T. Therefore, the end mill main body 1 of the present embodiment has 4 The cutting edge 5 of the strip is formed.

Of these cutting blades 5, every other two cutting blades 5 in the circumferential direction are regarded as a part of the cutting blades 5A in the present embodiment, and the remaining every other cutting blade 5 in the circumferential direction is the present embodiment. The remaining cutting edge 5B in the form. Some of the cutting blades 5A have a hemispherical bottom blade 5a whose rotation locus around the axis O has a center C on the axis O at the tip of the cutting edge portion 3 of the end mill main body 1, and after the bottom blade 5a. A conical outer peripheral blade 5b centered on the axis O, which extends from the end and gradually expands in diameter as the rotation locus around the axis O moves toward the rear end side so as to match the cone formed by the outer shape of the cutting edge portion 3. I have.
The flanks of the outer peripheral blade 5b are a minute second surface (flare surface) having a minute width from the outer peripheral blade 5b to the side opposite to the end mill rotation direction T, and further opposite to the end mill rotation direction T from this minute second surface. It is desirable to provide a large main second surface (clearance surface) having a larger clearance angle than the minute second surface toward the side. By providing such a minute second surface, it is possible to suppress wear on the minute second surface and prevent an increase in the wear width of the outer peripheral blade 5b.

Here, the tip of the chip discharge groove 4 formed on the outer peripheral edge of the wall surface on which the part of the cutting blades 5A faces the end mill rotation direction T has a recess toward the inner peripheral side toward the tip side of the end mill body 1. A groove-shaped gash 6 is formed. The bottom blade 5a is formed on the outer peripheral edge of the wall surface 6a facing the end mill rotation direction T of the gash 6, that is, the intersecting ridge line portion between the wall surface 6a and the flank 7 connected to the side opposite to the end mill rotation direction T of the bottom blade 5a. , The rotation locus is formed so as to form a hemisphere as described above.

In the present embodiment, as shown in FIG. 3 when viewed from the tip side in the O-direction of the axis, the gashes 6 of the bottom blade 5a of some of the cutting blades 5A of the two strips do not intersect with each other and form the axis O. It is formed so that it crosses slightly and crosses. As a result, the chip evacuation property can be further improved. Further, the flanks 7 of the bottom blade 5a have a first flank (second surface) 7a and a second flank (3rd surface) 7b whose flank angles gradually increase toward the opposite side of the end mill rotation direction T. And it is formed by the third flank surface (fourth surface) 7c.

On the other hand, in the remaining cutting edge 5B, the rotation locus around the axis O extends from the outer peripheral portion of the rear end of the rotation locus of the bottom blade 5a in some of the cutting blades 5A to the rear end side, and the same An auxiliary outer peripheral blade 5c that overlaps the rotation locus of the outer peripheral blade 5b of the cutting blade 5A of the portion is provided. That is, the auxiliary outer peripheral blade 5c of the remaining cutting blade 5B has a rotation locus around its axis O extending from the outer peripheral portion in front of the rear end of the bottom blade 5a of some cutting blades 5A to the rear end side. The bottom blade 5a is formed to have the same shape and dimensions so as to overlap the portion other than the tip portion. Further, in the portion corresponding to the tip of the bottom blade 5a of a part of the cutting blades 5A on the tip side of the auxiliary outer peripheral blade 5c where the rotation loci do not overlap, the tip of the end mill body 1 is the rotation of the bottom blade 5a. It is formed by being cut out so as to recede toward the inner circumference side with respect to the locus.
The flanks of the auxiliary outer peripheral blade 5c are also a minute second surface (flare surface) having a minute width from the auxiliary outer peripheral blade 5c to the side opposite to the end mill rotation direction T, and further from this minute second surface to the end mill rotation direction T. It is desirable to provide a large main second surface (relief surface) having a larger clearance angle than the minute second surface toward the opposite side. By providing such a minute second surface, it is possible to suppress wear on the minute second surface and prevent an increase in the wear width of the auxiliary outer peripheral blade 5c.

Here, the straight line L connecting the intersection Q of the rotation locus around the axis O of the tip P of the auxiliary outer peripheral blade 5c and the bottom blade 5a and the center C of the hemisphere formed by the rotation locus of the bottom blade 5a is shown in FIG. As shown in 2, the end mill body 1 is inclined toward the inner peripheral side toward the rear end side and intersects the axis O and the center C. The intersection angle θ formed by the straight line L with respect to the axis O at the center C is preferably in the range of 60 ° to 80 °, and is 70 ° in the present embodiment.

In the present embodiment, the tip of the end mill body 1 cut out as described above on the tip side of the auxiliary outer peripheral blade 5c of the remaining cutting blade 5B with respect to the tip P is the end mill rotation of the remaining cutting blade 5B. The flank 7 of the bottom blade 5a of a part of the cutting blade 5A adjacent to the direction T and the bottom blade 5a of a part of the cutting blade 5A adjacent to the opposite side of the remaining cutting blade 5B in the end mill rotation direction T. By intersecting the gash wall surface (the wall surface facing the side opposite to the end mill rotation direction T of the gash 6) 6b, the rotation locus around the axis O is formed by the rotation locus of the bottom blade 5a of some cutting blades 5A. It is formed so as to form a convex curve that recedes inward from the hemisphere.

In the tapered ball end mill having such a configuration, the bottom blade 5a and the bottom blade 5a form the outer peripheral portion of the rear end of the hemispherical rotation locus formed by the bottom blade 5a of some cutting blades 5A around the axis O. It is composed of the auxiliary outer peripheral blade 5c of the remaining cutting edge 5B having a rotation locus that overlaps with the rotation locus formed at the tip portion. Therefore, the outer peripheral portion of the rear end of the bottom blade 5a, which is often used for contour line machining of rib grooves and the like, can be made multi-blade, and the feed amount per blade can be increased to improve machining efficiency. In addition to this, high machining accuracy and machined surface quality can be obtained even if the feed amount is increased in this way.

On the other hand, at the most advanced portion of the end mill body 1 on the tip side of the auxiliary outer peripheral blade 5c of the remaining cutting blade 5B, the rotation locus is hemispherical in the same manner as the bottom blade 5a in succession to the auxiliary outer peripheral blade 5c. The cutting edge is not formed, and in the present embodiment, it is formed so as to recede inside the hemispherical rotation locus of the bottom blade 5a. For this reason, as in the case of trying to form a bottom blade on the tip side of the auxiliary outer peripheral blade 5c, the number of gashes 6 at the most advanced portion of the end mill main body 1 increases, causing a decrease in strength, or each of the gashes 6 is used. There is no need to make it smaller and cause chip clogging.

Further, in the present embodiment, a straight line L connecting the intersection Q of the rotation locus around the axis O of the tip P of the auxiliary outer peripheral blade 5c and the bottom blade 5a and the center C of the hemisphere formed by the rotation locus of the bottom blade 5a is formed. At this center C, the intersection angle θ with respect to the axis O when intersecting the axis O is within the range of 60 ° to 80 °, which reliably prevents the strength of the cutting edge of the end mill body 1 from decreasing and chip clogging. At the same time, it is possible to further improve the processing efficiency, processing accuracy, and machined surface quality.

That is, when the crossing angle θ exceeds the above range, the portion where the tip portion of the auxiliary outer peripheral blade 5c and the bottom blade 5a overlap becomes too short, and the machining efficiency, machining accuracy, and machining surface quality are sufficiently improved during contour line machining. There is a risk that it cannot be improved. On the contrary, when the crossing angle θ is less than the above range, the auxiliary outer peripheral blade 5c extends closer to the most advanced end of the end mill body 1, and the capacities of the chip discharge groove 4 and the gash 6 become smaller, resulting in chip clogging. It may occur or cause insufficient strength.

Further, in the present embodiment, a plurality of cutting edges 5A and the remaining cutting edges 5B are alternately formed in the circumferential direction on the outer periphery of the tip portion (cutting edge portion 3) of the end mill main body 1. On the other hand, the tip side of the remaining cutting blade 5B with respect to the auxiliary outer peripheral blade 5c is the flank 7 (third) of the bottom blade 5a of a part of the cutting blade 5A adjacent to the end mill rotation direction T of the remaining cutting blade 5B. The flank surface 7c) and the gash wall surface of the bottom blade 5a of a part of the cutting blades 5A adjacent to the side opposite to the end mill rotation direction T of the remaining cutting blade 5B (the side opposite to the end mill rotation direction T of the gash 6). As described above, the rotation locus around the axis O is formed in a convex curve shape that recedes inward from the hemisphere formed by the bottom blade 5a by intersecting and notching the wall surface (wall surface facing) 6b.

Therefore, on the tip side of the auxiliary outer peripheral blade 5c and on the side opposite to the end mill rotation direction T of the bottom blade 5a, the relief surface 7 of the bottom blade 5a is left as it is, and a part of the cutting blades 5A and Even in this embodiment, which is a 4-flute tapered ball end mill in which two remaining cutting blades 5B are formed, the same as the two-flute tapered ball end mill on the tip side of the auxiliary outer peripheral blade 5c of the remaining cutting blade 5B. Can be configured as. Therefore, it is possible to secure the cutting edge strength of the bottom blade 5a and the strength of the end mill body 1 itself on the tip side of the auxiliary outer peripheral blade 5c, and prevent the occurrence of defects and the like.

Next, an example of the present invention will be given to demonstrate its effect. In this embodiment, the intersection angle θ is set to 70 °, the intersection angle θ is set to 80 ° and 60 °, which are the upper and lower limits within the above range, and the intersection angle θ is slightly lower than the above range. Five types of tapered ball end mills having an intersection angle θ of 55 ° and 85 ° slightly exceeding the above range were produced. These are referred to as Examples 1 to 5 in the order of the smallest crossing angle θ.

Further, as a comparative example with respect to Examples 1 to 5, the intersection angle θ is 0 °, that is, all of the four cutting edges 5 have a bottom blade 5a forming a hemispherical rotation locus, and the intersection angle θ. 90 °, that is, the remaining cutting edge 5B overlaps only the outer peripheral blade 5b without having a portion where the rotation locus overlaps with the bottom blade 5a of a part of the cutting edge 5A, and the intersection angle θ is larger than 90 °. The tip of the outer peripheral blade which is 95 °, that is, which is not continuous with the bottom blade (tip ball blade) like the tapered ball end mill described in Patent Document 1, is closer to the rear end side of the end mill body than the rear end of the tip ball blade. The one that is located was made. Also for these, Comparative Examples 1 to 3 are set in the order of the smallest crossing angle θ.

The tapered ball end mills of Examples 1 to 5 and Comparative Examples 1 to 3 are made of superhard alloy, the radius of the hemisphere formed by the rotation locus of the bottom blade 5a is 0.5 mm, and the tapered single angle of the outer peripheral blade 5b is 0. The blade length in the axis O direction from the tip of the bottom blade 5a on the axis O to the rear end of the outer peripheral blade 5b was 10 mm, and the twist angle of the outer peripheral blade 5b was 25 °.

Then, by using the tapered ball end mills of Examples 1 to 5 and Comparative Examples 1 to 3, rib grooves are formed in the work material made of chrome molybdenum steel (SCM420) by contour processing, and the surface roughness of the groove wall surface at that time is roughened. (Arithmetic mean roughness Ra in JIS B 0601: 2001) and the maximum driving force required to rotate the tapered ball end mill were measured. The results are shown in Table 1 below in order from the one with the smallest intersection angle θ. The processed rib groove has a groove depth of 10 mm, a groove width of 1.1 mm, a rib groove gradient angle of 0.75 °, and a groove length of 50 mm, and the entire groove is 0.3 mm by rough processing in advance. The processing conditions are that the rotation speed of the end mill body 1 is 15,000 rotations / min, the feed rate is 750 mm / min, the depth of cut per time in the axis O direction is 0.03 mm, and the water-soluble cutting fluid It was a wet process using.

From Table 1, regarding the surface roughness, in Comparative Example 1 and Examples 1 to 4 in which the rotation loci of the bottom blade 5a of some cutting blades 5A and the auxiliary outer peripheral blade 5c of the remaining cutting blade 5B often overlap. Approximately the same good results were obtained. Further, in Example 5, the surface roughness tended to be lower than that of Comparative Example 1 and Examples 1 to 4, but the difference was small.

On the other hand, in Comparative Examples 2 and 3 in which the remaining cutting edge 5B does not have a portion overlapping the rotation locus of the bottom blade 5a of a part of the cutting blade 5A, the outer peripheral portion of the rear end of the hemispherical rotation locus is formed. Since only the bottom blade 5a of a part of the cutting blades 5A of the two strips was formed, the surface roughness was significantly reduced as compared with Examples 1 to 5 and Comparative Example 1 at the constant feed rate as described above. It was.

Next, when the maximum rotational driving force is compared, contrary to the case of surface roughness, in Comparative Example 1 in which all of the four cutting edges 5 have a bottom edge 5a forming a hemispherical rotational locus. In order to perform contour line processing while satisfying the above processing conditions, the result is that an extremely large driving force is required as compared with other Comparative Examples 2 and 3 and Examples 1 to 5. Further, when observing the tapered ball end mill of Comparative Example 1 after the processing was completed, chip clogging and significant wear were observed in the bottom blade 5a especially around the center of rotation of the inner peripheral portion of the tip of the end mill main body 1.

On the other hand, in Examples 2 to 5 and Comparative Examples 2 and 3, contour line processing satisfying the above processing conditions can be performed with substantially the same driving force without requiring a large driving force as in Comparative Example 1. We were able to perform efficient processing. Further, in Example 1, a larger driving force was required as compared with Examples 2 to 5 and Comparative Examples 2 and 3, but the difference was not as large as the difference from Comparative Example 1.

Therefore, based on the results of these surface roughness and the maximum rotational driving force, according to Examples 1 to 5, it is possible to achieve both machining efficiency, machining accuracy, and machined surface quality in contour line machining, and further, the intersection angle θ is According to Examples 2 to 4 within the above range, it is recognized that it is possible to more reliably improve the processing efficiency, processing accuracy, and processed surface quality.

1 End mill body 2 Shank part 3 Cutting edge part (tip of end mill body 1)
4 Chip discharge groove 5 Cutting blade 5A Partial cutting blade 5B Remaining cutting blade 5a Bottom blade 5b Outer blade 5c Auxiliary outer blade 6 Gash 6a Gash 6 end mill Rotation direction T facing wall surface 6b Gash wall surface (Gash 6 end mill rotation) Wall surface facing the opposite side of direction T)
7 Flood surface of bottom blade 5a 7a 1st flank surface (2nd surface)
7b 2nd flank (3rd surface)
7c 3rd escape surface (4th surface)
O Axis of the end mill body 1 T End mill rotation direction C Center of hemisphere formed by the rotation locus around the axis O of the bottom blade 5a P Tip of the auxiliary outer peripheral blade 5c Q Rotation locus and bottom around the axis O of the tip P of the auxiliary outer blade 5c Intersection point L with the blade 5a Straight line θ connecting the intersection point Q and the center C The intersection angle formed by the straight line L with respect to the axis O

Claims (2)

Multiple chip discharge grooves extending toward the rear end are formed on the outer periphery of the tip of the end mill body that is rotated around the axis, and each of these chip discharge grooves is cut on the outer peripheral edge of the wall surface facing the end mill rotation direction. The blade is formed and
Some of the cutting blades are a bottom blade having a hemispherical rotation locus around the axis at the tip of the end mill body and having a center on the axis, and a bottom blade extending from the rear end of the bottom blade. It is equipped with a conical outer peripheral blade centered on the above-mentioned axis whose diameter gradually increases as the rotation locus around the axis gradually increases toward the rear end side.
In the remaining cutting blades, the rotation locus around the axis extends from the outer peripheral portion of the rear end to the rear end side of the rotation locus of the bottom blade in some of the cutting blades to form the rotation locus of the outer peripheral blade. Equipped with overlapping auxiliary outer peripheral blades ,
The straight line connecting the intersection of the rotation locus of the tip of the auxiliary outer peripheral blade around the axis with the bottom blade and the center of the hemisphere formed by the rotation locus of the bottom blade intersects within the range of 60 ° to 80 °. At the corner, it intersects the axis at the center,
Tapered ball end mill. On the outer periphery of the tip of the end mill main body, a plurality of the above-mentioned partial cutting edges and the above-mentioned remaining cutting edges are alternately formed in the circumferential direction, and the remaining cutting edges are more than the above-mentioned auxiliary outer peripheral blades. On the tip side, the flank surface of the bottom blade of the remaining cutting edge adjacent to the end mill rotation direction of the remaining cutting edge and the partial cutting adjacent to the opposite side of the remaining cutting edge in the end mill rotation direction. The tapered ball end mill according to claim 1 , wherein the bottom of the blade is cut out so as to intersect with the gash wall surface of the blade.

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