JP7419059B2 - end mill - Google Patents

Description

The present invention relates to an end mill in which, for example, an outer circumferential cutter and an outer circumferential flute groove are provided on the outer circumferential surface, and a bottom cutter having an R-shaped portion is formed on the distal end surface of the tool body.

Generally, in the field of precision machining, ball end mills, radius end mills, and the like are used to cut molds, parts, and the like. For example, in the ball end mill 100 shown in FIG. It has a peripheral blade 103 disposed on the side. A back tapered blade is formed at the distal end portion of the outer peripheral blade 103. The outer diameter of the R blade 102 is the same as or larger than the diameter D of the tool body.

A gash groove 104 having a rake face 104a of the R blade 102 is formed in front of the R blade 102 in the rotational direction. Furthermore, a flute groove 105 is formed at the front of the peripheral blade 103 in the rotational direction. An intersecting ridgeline portion 107 that forms a boundary between the gash groove 104 and the flute groove 105 is formed at the connection portion 106 between the R blade 102 and the peripheral blade 103.
Then, by cutting the ball end mill 100 into the work material and feeding it laterally, the rotating R blade 102 cuts the work material such as a mold. Chips generated by the R blade 102 are discharged to the outside from a rake face 104a formed in the gash groove 104. Such a ball end mill is also disclosed in Patent Document 1, for example.

Japanese Patent Application Publication No. 2000-117522

However, it has been difficult to accurately form the connecting portion 106 between the R blade 102 and the peripheral blade 103 at the intersection ridgeline portion 107 between the gash groove 104 and the flute groove 105. Therefore, there was a problem in that the machining accuracy of the portion of the R blade 102 near the connecting portion 106 was likely to decrease.
Further, when cutting a workpiece with the ball end mill 100, if there is a contact surface for the workpiece near the connection part 106 between the R blade 102 and the peripheral blade 103, the rake face 104a of the R blade 102 and the peripheral blade 103 Cutting is performed using the R blade 102 near the boundary of the rake face 105a. In this case, since the two rake faces 104a and 105a are separated by the intersecting ridgeline portion 107 and have different rake faces and rake angles, the cutting process by the R blade 102 and the flow of chips from the rake face 104a to the flute groove 105 are prevented. There is also the problem that the machining process does not proceed smoothly, resulting in deterioration of machining accuracy and machined surface roughness.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an end mill that can improve the precision and machined surface roughness of the R-shaped portion of the bottom blade having the R-shaped portion. .

An end mill according to the present invention includes a cutting blade section on the distal end side of a tool body that is rotatable around a central axis, and includes a plurality of bottom cutters formed on the distal end surface of the cutting blade section and having an R-shaped portion; A gash groove formed on the front side in the rotational direction of the bottom blade and having a rake surface of the bottom blade, a peripheral blade connected to the bottom blade and formed toward the base end side, and a gash groove on the front side in the rotational direction of the peripheral blade. A flute groove is formed, and the gash groove is set such that the distance from the tip of the tool body to the intersection with the flute groove is longer than the radius length of the cutting edge, and the gash groove forms a rake surface of the bottom blade. It is characterized by having the following.
According to the present invention, the distance from the tip of the tool body to the intersection with the flute groove of the gash surface of the gash groove is set longer than the radius of the cutting edge, so the accuracy of the R-shaped portion of the bottom blade Even when cutting a workpiece with the proximal end of the bottom blade, which has an R-shaped part, the chips flow smoothly along the rake face of the gash surface and are discharged to the outside. Accuracy and machined surface roughness are improved. Moreover, the precision of the R-shaped portion of the bottom blade is high.

Further, it is preferable that the gash surface forms a rake face of the bottom blade and a rake face of a back taper connecting blade connected to the bottom blade.
Chips cut by the back taper connecting blades of the bottom edge and peripheral edge run on the rake face of the gash surface and flow toward the flute groove side, so the flow of chips is smooth without being hindered. Improves machinability.

Further, it is preferable that the bottom blade has an R blade with a length exceeding 1/4 arc from the tip of the cutting blade, and is connected to the peripheral blade via a back taper connecting blade connected to the bottom blade. .
The terminal end that forms the boundary between the R blade of the bottom blade and the back taper connecting blade is formed to extend toward the proximal end from the 1/4 arc part of the bottom blade, making it easy to process the R blade and have high processing accuracy. The machining accuracy of the cutting process near the 1/4 arc part of the R blade is good.

Further, it is preferable that the back taper connecting blade connected to the bottom blade forms a part of the outer peripheral blade, and the gash surface extends to the connecting portion between the back taper connecting blade and the outer peripheral blade.
Even if the positional accuracy of the terminal end between the bottom blade and the back taper connecting blade or the connecting part of the back taper connecting blade and the peripheral blade is low, the tool will remain stable because these are formed on the back taper connecting blade of the peripheral blade. Does not degrade R accuracy and does not reduce machining accuracy during finishing machining.

Further, it is preferable that the helix angle of the flute groove is set to be the same as or larger than the helix angle of the gash groove.
The chips traveling on the gash surface of the gash groove smoothly travel through the flute grooves twisted at the same or greater helix angle and are discharged.

According to the end mill of the present invention, the gash groove forms a gash surface in which the distance extending from the tip of the cutting edge to the intersection with the flute groove is longer than the radial length of the cutting edge. The chips cut in the radial length portion on the end side run on the rake face consisting of the gash surface and flow to the outside. Therefore, the cutting performance in the radial length portion on the proximal end side of the bottom blade is good, the flow of chips along the gash surface is smooth, and the machining accuracy and machined surface roughness of the workpiece can be improved. Moreover, the machining accuracy of the bottom blade is high.

FIG. 2 is a front end view showing the cutting edge portion of the ball end mill according to the first embodiment of the present invention. 2 is a side view showing gash grooves and flute grooves of the ball end mill shown in FIG. 1. FIG. FIG. 3 is a side view showing the rake face and flank face of the R blade. It is a side view showing the R blade and the peripheral blade in the cutting edge portion of the ball end mill. FIG. 5 is an enlarged view of the R blade and the peripheral blade shown in FIG. 4. FIG. FIG. 3 is a side view of a radius end mill according to a second embodiment of the present invention. FIG. 7 is an enlarged view of the R blade and the peripheral blade shown in FIG. 6; FIG. 2 is a side view of a cutting edge portion of a conventional ball end mill.

EMBODIMENT OF THE INVENTION Hereinafter, an end mill having an R blade according to each embodiment of the present invention will be described based on the accompanying drawings.
1 to 5 show a ball end mill 1 having an outer peripheral flute groove according to a first embodiment of the present invention. In FIGS. 1 to 3, a ball end mill 1 according to the present embodiment includes a tool body 2 that is formed in a substantially cylindrical shape and rotates around a central axis O, and a cutting edge portion 3 that is formed at the tip of the tool body 2. We are prepared.
This ball end mill 1 is used for cutting high hardness materials such as machine parts and molds, nonferrous metals, general steel materials, and the like. In this specification, the side of the cutting edge 3 along the central axis O of the tool body 2 will be referred to as the distal end side, and the opposite side connected to the main shaft will be referred to as the base end side.

In FIGS. 1 and 4, the ball end mill 1 has a plurality of arcuate bottom blades, e.g. two R blades 5, which are formed on the tip surface 4 of the cutting blade 3 at positions facing each other 180 degrees. has been done. When the outer diameter of the tool body 2 is D, and the radius of the R blade 5 is R, 2R≧D is set. Furthermore, the R blade 5 is formed with a raised center. Alternatively, the R blade 5 may have a lower core.
In the cutting edge portion 3 shown in FIGS. 2 and 3, a gash groove 7 is formed on the front side of each R blade 5 in the rotational direction. The R blade 5 is formed in a convex arc shape and has a twist angle α such that it is gradually twisted rearward in the rotational direction from the distal end side to the proximal end side when viewed from the side. The gash groove 7 is similarly twisted rearward in the rotational direction at a twist angle α (see FIG. 2).

A flute groove 16 is formed on the forward side in the rotational direction of the outer circumferential cutter 13 formed on the proximal end side of the R cutter 5 . The outer circumferential cutter 13 and the flute groove 16 also have a helical angle β such that they are gradually twisted spirally toward the rear in the rotational direction from the distal end toward the proximal end. The helix angle α of the R blade 5 is set to be the same as or smaller than the helix angle β of the peripheral blade 13. By setting the helix angle β of the peripheral blade 13 to be greater than the helix angle α of the R blade 5, the chips generated by the R blade 5 can be smoothly discharged.

A rake face 8 is formed on the gash surface of the gash groove 7 facing forward in the rotational direction of the R blade 5. The rake face 8 may be formed into a concave arc surface, a flat surface, or a convex arc surface. In this embodiment, it is assumed that the rake face 8 of the R blade 5 is formed in a convex arc shape having a positive rake angle.
A second flank face 9 and a third flank face 10 having a positive clearance angle are sequentially formed as flank faces on the rear side in the rotational direction of the R blade 5. The respective flanks of the back taper connecting blade 13d of the R blade 5 and the peripheral blade 13, which will be described later, are the second flank 9, and are formed with the same clearance angle. The clearance angle of the third flank face 10 is larger than the clearance angle of the second flank face 9. Further, a rake face 17 of the peripheral blade 13 is formed on the forward side of the flute groove 16 in the rotational direction of the peripheral blade 13 .

As shown in FIGS. 4 and 5, the R blade 5 has a proximal cut formed in a substantially 1/4 arc shape with a radius R from the distal end p, which is the intersection with the central axis O, toward the proximal end. It has a blade 5b. Furthermore, in addition to the base cutting edge 5b, the R blade 5 has a circular arc blade 5a having a radius R to a terminal end s that is a predetermined distance longer on the base end side than the 1/4 arc of the intersection r.
The arc blade 5a is a circular arc having a length m centered on the center point q from the intersection r to the terminal end s, and is curved by an angle θ toward the central axis O side from the intersection r. Furthermore, the cutting edge portion 3 has a maximum outer diameter of 2R at the intersection r of the R blade 5.

The terminal end s of the R blade 5 and the outer peripheral blade 13 are connected by a back taper connecting blade 13d. The outer peripheral blade 13 and the back taper connecting blade 13d are connected in the same line through the connecting portion 12. A stepped undercut portion 13a is formed in the longitudinally intermediate portion of the outer peripheral blade 13 formed in a back-tapered shape. The outer peripheral blade 13 between the undercut portion 13a and the connecting portion 12 is a back-tapered blade 13b whose outer diameter gradually decreases toward the base end, and the base end portion 13c of the undercut portion 13a has an outer diameter dimension. is held constant without shrinking. Alternatively, the outer diameter of the proximal end portion 13c may be reduced.
The back taper connecting blade 13d and the back taper blade 13b of the outer peripheral blade 13 have, for example, a linear back taper shape, and are inclined with respect to the central axis O at a back taper angle θ. Here, the arcuate blade 5a and the back taper connecting blade 13d serve as an extension part 14 that extends the R blade 5 and connects to the peripheral blade 13. The back taper connecting blade 13d constitutes a part of the outer peripheral blade 13. In addition, the back taper blade 13b and the back taper connecting blade 13d of the outer peripheral blade 13 may be formed in an arc shape. Further, the back taper connecting blade 13d and the back taper blade 13b may be formed at different angles with the connecting portion 12 as a boundary.

Next, the extension portion 14 between the intersection r and the connecting portion 12 in the R blade 5 will be explained in detail with reference to FIGS. 4 and 5.
The R blade 5 extends in an arc shape with a radius R by a length m from the tip p of the cutting edge portion 3 toward the outer peripheral surface beyond the intersection r formed in a 1/4R arc shape to the terminal end s. There is. The R blade 5 has a radial length R from the center point q to the tip p, and in addition to the 1/4 arc length due to the 90 degree angle range from the tip p to the intersection r, the R blade 5 has a circular arc length by an angle θ. It has an arcuate blade 5a with an extended length. Moreover, in the R blade 5, there is no seam between the base cutting edge 5b and the arcuate blade 5a via the intersection r.
The angle θ of the center point q for setting the length m of the arcuate blade 5a is set, for example, in the range of 0°<θ≦10°. In this embodiment, the angle θ is set to 1°. Although the angle θ of the arcuate blade 5a is set equal to the back taper angle θ of the peripheral blade 13, it may be different.

Here, if the angle θ is 0° or less, the position of the terminal end s of the R blade 5 cannot be extended from the intersection r to the base end side. Furthermore, if the angle θ exceeds 10°, the terminal end s of the R blade 5 becomes too long from the intersection r to the proximal end, and the diameter of the cutting blade 3 is reduced, and the diameter under the neck of the cutting blade 3 becomes small. Tool strength decreases.
The back taper connecting blade 13d extends over a length n from the terminal end s of the R blade 5 to the connecting portion 12, and the cutting blade having the length n forms a part of the outer peripheral blade 13. An imaginary line from the center point q to the terminal end s is formed at right angles to the back taper connecting blade 13d.

The extension part 14 of the R blade 5 has a length (m+n) that is the sum of the arcuate blade 5a with a length m and the back taper connecting blade 13d with a linear length n, and is set to an extension width L. There is. The arcuate blade 5a having a radius R terminates at a terminal end s, and further extends toward the base end by a length n of a back-taper connecting blade 13d to reach the connecting portion 12. The connecting portion 12 is connected to an intersecting ridgeline portion 20 between the gash groove 7 and the flute groove 16.

Here, the extension width L is set to a length range of 0.02R to 0.2R of the radius R of the R blade 5. If the extension width L is smaller than 0.02R, it may become zero due to processing errors, making processing difficult. On the other hand, if the extension width L is larger than 0.2R, the diameter D is reduced and the flute groove 16 may become smaller, resulting in poor chip evacuation and increased cutting resistance.

Therefore, the gash surface of the extended gash groove 7 also serves as each rake surface of the extended circular arc blade 5a of the R blade 5 and the back taper connecting blade 13d of the peripheral blade 13, and forms a part of the rake surface 8. . Therefore, the rake face 8 of the R blade 5 made of a gash surface extends smoothly from the arcuate blade 5a of the R blade 5 to the back taper connecting blade 13d of the peripheral blade 13, and there is no seam.
Moreover, the connecting portion 12 between the R blade 5 and the peripheral blade 13 extends from the intersection r forming the 1/4 arc of the R blade 5 to the proximal end by an extension width L (=m+n) of the extension portion 14. The R blade 5 and the outer peripheral blade 13 are respectively extended. In connection with this, the rake face 8 of the R blade 5, which is the gash surface of the gash groove 7, extends from the intersection r to the connection part 12. Since the rake angle of the rake face 8 is the same, the chips generated by the arcuate blade 5a of the R blade 5 and the back taper connecting blade 13d that sandwich the terminal end s are smoothly cut and sent to the base end side.

The ball end mill 1 according to this embodiment has the above-mentioned configuration, and how to use it will be described next.
While rotating the ball end mill 1 around the central axis O, vertical wall processing perpendicular to the workpiece is performed in contour finishing processing. When cutting, the R blade 5 of the cutting edge part 3 cuts the workpiece, and the cut chips travel on the rake face 8 of the gash groove 7, flow toward the base end, and are discharged to the outside. . Moreover, since the flute groove 16 is twisted backward in the rotational direction at the same helix angle α or larger helix angle β as the gash groove 7, chips flow smoothly from the gash groove 7 to the flute groove 16 and are discharged to the outside. Ru.

Then, when the cut by the vertical feed in the direction of the center axis O of the cutting edge part 3 progresses and is fed beyond the intersection r, and when the work material is cut by the R blade 5 by horizontal feeding, from the intersection r of the R blade 5. The work material is also cut in the region of the arcuate blade 5a and the back taper connecting blade 13d of the peripheral blade 13 up to the terminal end s.
In this case, the rake angles of the circular arc blade 5a from the intersection r to the terminal end s of the R blade 5 and the rake face 8 of the back taper connecting blade 13d are formed at the same angle, so chips can be smoothly transferred to the rake face 8. It flows over the intersecting ridgeline portion 20 and is sent to the flute groove 16 side. Therefore, the machinability of cutting in a 1/4 arc from the tip p of the R blade 5 to the intersection r, and cutting in the extension 14 from the intersection r to the terminal part s and the connecting part 12 is good, Chip discharge is also smooth.

By the way, if there is an error in the formation position of the extension part 14 including the terminal end s of the R blade 5 and the connecting part 12, a machining error may occur in this part. However, the terminal end s of the arcuate blade 5a and the area of the back taper connecting blade 13d from the terminal end s to the connecting portion 12 are recessed inward with respect to the intersection r that protrudes to the outermost side of the R blade 5. . Therefore, since the machined surface is finished at the intersection r that protrudes most in the lateral direction of the R blade 5, no traces of machining errors remain. Therefore, even if there is an error in the formation position of the extension portion 14, the processing error can be absorbed.

As described above, the ball end mill 1 according to the present embodiment provides the following effects.
The R blade 5 is added to the intersection r forming a 1/4 arc from the tip p, and the arc blade 5a is extended by a length m corresponding to the angle θ to the terminal end s. Therefore, manufacturing errors in the arc shape of the R blade 5 can be suppressed, the machining accuracy of the R blade 5 can be improved, and a highly accurate arc shape can be formed up to the terminal end s beyond the intersection r.
Further, the R blade 5 is extended as an arc blade 5a beyond the intersection r of the 1/4 arc to the terminal end s, and furthermore, an extension part 14 having a back taper connecting blade 13d is formed, and the outer periphery is extended through the connecting part 12. It was connected to the blade 13 and the gash groove 7 was extended to the connecting part 12. Therefore, the rake faces 8 of the additional circular arc blades 5a and the back taper connecting blades 13d are formed at the same rake angle without any seam on the gash surface of the gash groove 7, and the generated chips can smoothly travel to the rake face 8. Machining accuracy and machined surface roughness are improved.

Further, the arc-shaped R blade 5 is connected to the outer circumferential blade 13 at the connecting portion 12 by extending the arc blade 5a from the intersection r and via the back taper connecting blade 13d. Therefore, even if there is an error in the formation position of the end portion s or the connecting portion 12, the machining error will not occur on the machined surface of the workpiece because it is retracted inward from the intersection r that protrudes to the outermost side of the R blade 5. There's nothing left. Since the helix angle β of the flute groove 16 is formed to be the same or larger than the helix angle α of the gash groove 7 formed in the cutting edge 3, chips generated by the R blade 5 can be smoothly discharged.
In addition, since the angle θ of the arcuate blade 5a following the R blade 5 is set in a range greater than 0° and less than 10°, cutting performance can be improved and the diameter under the neck of the cutting edge 3 can be suppressed from becoming smaller. This ensures the strength of the tool.

Although the ball end mill 1 according to the embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and various different forms and aspects can be adopted without departing from the spirit of the present invention. Needless to say. All of these are included within the technical scope of the present invention.
Other embodiments and modified examples of the present invention will be described below, and parts and components that are the same as or similar to those of the above-described embodiments will be described using the same reference numerals.

6 and 7 show a radius end mill 25 according to the second embodiment, which has the same configuration as the ball end mill 1 according to the first embodiment.
In the radius end mill 25 according to the present embodiment, the outer corner of the bottom blade 26 formed on the cutting edge 3 of the approximately cylindrical tool body 2 rotatable around the central axis O has a 1/4 arc shape with a radius R. An R-shaped blade 5 (R-shaped portion) is formed. An arcuate blade 5a with a radius R and an angle θ is formed on the extension of the intersection r forming the proximal end of the base cutting edge 5b of the R blade 5 up to the terminal end s.
Further, a straight back taper connecting blade 13d extends to the connecting portion 12 following the terminal end s of the R blade 5, and an outer circumferential blade 13 is formed on the base end side of the connecting portion 12. The back taper blade 13b and the back taper connecting blade 13d of the peripheral blade 13 have a back taper angle θ, and are formed in the same straight line, but may be formed in an arc shape. Alternatively, the back taper angle θ of the peripheral blade 13 may be changed to a different angle directed inward at the position of the connecting portion 12.

Further, a gash groove 7 is formed on the forward side of the R blade 5 in the rotational direction, and the gash surface of the gash groove 7 forming the rake face 8 of the R blade 5 extends to the connecting portion 12 . A flute groove 16 is also formed on the front side of the outer peripheral cutter 13 in the rotational direction.
Therefore, the radius end mill 25 according to the second embodiment also has the same configuration as the ball end mill 1 according to the first embodiment, and has the same effects.

In each of the embodiments described above, the rake face of the additional arcuate blade 5a and the rake face of the back taper connecting blade 13d are set to the same rake angle as the rake face 8 of the base cutting edge 5b of the R blade 5. The rake angle of the rake face 8 of the cutting edge 5b may be different. Further, the rake angles of the rake face of the arcuate blade 5a and each rake face of the back taper connecting blade 13d may be different from each other.
Furthermore, although the arcuate blade 5a of the R blade 5 and the back taper connecting blade 13d of the peripheral blade 13 are formed as the extension part 14, the terminal end s of the R blade 5 is directly connected to the peripheral blade without providing the back taper connecting blade 13d. It may be connected to the thirteen back tapered blades 13b via the connecting portion 12.
In addition, in the ball end mill 1 and the radius end mill 25 according to each of the embodiments described above, the number of bottom blades formed in the cutting edge portion 3 is not limited to two, and may be three or more.

1 Ball end mill 2 Tool body 3 Cutting blade part 5 R blade (bottom blade)
5a Arc blade (bottom blade)
5b Base cutting blade (bottom blade)
7 Gash groove 8 Rake face 9 Second flank face 12 Connection part 13 Peripheral blade 13b Back taper blade (outer peripheral blade)
13d Back taper connecting blade (peripheral blade)
16 Flute groove 17 Rake face of peripheral cutter 20 Intersecting ridge line portion 25 Radius end mill 26 Bottom blade p Tip portion q Center point r Intersecting portion s End portion O Center axis line

Claims (4)

In an end mill that has a cutting edge on the tip side of the tool body that can rotate around the central axis,
a plurality of bottom blades formed on the tip surface of the cutting blade portion and having an R-shaped portion;
a gash groove formed on the front side of the bottom blade in the rotational direction and having a rake face of the bottom blade;
a peripheral blade connected to the bottom blade and formed toward the proximal end;
a back taper connecting blade connected to the bottom blade;
a flute groove formed on the front side of the peripheral blade in the rotational direction;
The gash groove has a gash surface that is set such that the distance from the tip of the tool body to the intersection with the flute groove is longer than the radial length of the cutting edge, and that forms the rake surface of the bottom blade .
The back taper connecting blade forms a part of the peripheral blade,
The end mill is characterized in that the gash surface extends to a connecting portion between the back taper connecting blade and the outer peripheral blade . The end mill according to claim 1, wherein the gash surface forms a rake face of the bottom blade and a rake face of a back taper connecting blade connected to the bottom blade. The bottom blade has an R blade with a length exceeding 1/4 arc from the tip of the cutting blade, and is connected to the outer circumferential blade via a back taper connecting blade connected to the bottom blade. The end mill described in item 1 or 2. The end mill according to any one of claims 1 to 3 , wherein the helix angle of the flute groove is set to be the same as or larger than the helix angle of the gash groove.

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