JP6287343B2 - End mill - Google Patents

Description

  In the present invention, a multi-blade end mill in which a plurality of (many) bottom blades are formed at the tip of an end mill body rotated around an axis, and in particular, a convex curved corner blade is formed at the outer peripheral end of the bottom blade. It relates to a multi-blade radius end mill.

  For example, Patent Document 1 discloses a multi-blade radius end mill in which the number of cutting blades is 6 to 30 as a blade or impeller made of a thin hard-to-cut material such as a turbine or a supercharger. Have been described. Here, when performing high-efficiency machining with high feed mainly using the bottom blade and corner blade of such a multi-blade radius end mill, the bottom blade is equally spaced in the circumferential direction to ensure chip disposal. In this case, the bottom blade periodically bites the work material, so chatter vibration may occur when processing particularly thin portions such as turbine blades. .

  Therefore, in Patent Document 2, chatter vibrations are obtained by alternately increasing or decreasing the rake angle in the axial direction of the even number of bottom knives in two sizes, and smoothing the distribution of cutting resistance around the axis as a whole tool. An end mill (square end mill) that suppresses the occurrence of slag has been proposed. In the end mill described in Patent Document 2, the outer peripheral rake angle (radial rake angle) of the outer peripheral blade continuing to the bottom blade having a small axial rake angle is the outer periphery continuous to the bottom blade having a larger axial rake angle. The outer peripheral rake angles of even-numbered outer peripheral rake angles are alternately increased and decreased in two types so as to be larger than the outer peripheral rake angle of the blades, thereby suppressing the occurrence of chatter vibration more effectively.

Japanese Patent No. 5016737 Japanese Patent No. 4313579

  By the way, in such a radius end mill and a square end mill, usually, a plurality of chip discharge grooves are formed in the outer periphery of the end portion of the end mill body at intervals in the circumferential direction, and a wall surface and an outer peripheral flank surface facing the end mill rotation direction are formed. An outer peripheral blade is formed at the crossing ridge line portion of the disc, and a disc-type grinding wheel having an outer peripheral surface with a convex V-shaped cross section is rotated about the central axis, and along the wall surface facing the end mill rotation direction of the chip discharge groove. By cutting in the radial direction of the end mill body, a gash having a wall surface facing the end mill rotation direction and a wall surface facing the rear side in the end mill rotation direction is formed at the tip of the chip discharge groove, and the end mill rotation of the gash is performed. A bottom blade is formed at the intersecting ridge line portion between the wall surface facing the direction and the tip clearance surface of the end mill body.

  Therefore, since the wall surface facing the end mill rotation direction of the gasche is used as a rake face of the bottom blade, the rake angle in the axial direction of the bottom blade is increased or decreased in two types as in the end mill described in Patent Document 2. To increase the size, the crossing angle formed when the center axis of the disc-type grinding wheel and the axis of the end mill body are viewed from the radial direction of the end mill body is increased or decreased for each bottom edge gash with different rake angles in the axial direction. You can do it.

  However, in the end mill in which the bottom blade is formed in such a manner, the wall face facing the end mill rotation direction of the gasche and the rear side in the end mill rotation direction based on the sandwiched angle of the convex V shape formed by the outer peripheral surface of the disc-type grinding wheel. Gash opening angles formed by the wall facing each other are equal to each other in the gash connected to each bottom blade. Therefore, in the gash connected to the bottom blades having different rake angles in the axial direction, the back edge in the end mill rotation direction of the gash is directed from the bottom blade. The opening widths of the gashes to the intersecting ridge line portion between the wall surface and the tip flank adjacent to the end mill rotation direction are different sizes. Therefore, in the gash with a small opening width, the chips generated by the bottom blade may be clogged.

  Further, particularly when the bottom blades are arranged at equal intervals in the circumferential direction as described above, when the opening widths of the gashes are different in this way, they are viewed from the front end side in the axial direction of the front end flank connected to the bottom blade. The widths also have different sizes, that is, the thickness of the end mill main body at the portion of the bottom blade connected to the rear side in the end mill rotation direction, that is, the thickness of the so-called back blade back metal also has a different size. For this reason, with a bottom blade having a small back metal thickness, the strength of the cutting edge is reduced, and defects or the like are likely to occur. These problems are particularly noticeable in a multi-blade end mill in which the opening width of the gash and the thickness of the back metal must be limited for each bottom blade.

  The present invention has been made under such a background, and in particular, in the multi-blade end mill as described above, even when the axial rake angle of the bottom blade is different, the occurrence of clogging of chips is prevented and the bottom blade End mills that can ensure the cutting edge strength even if they are arranged at equal intervals in the circumferential direction, and can perform stable cutting while suppressing the occurrence of chatter vibrations even on thin parts of turbine blades The purpose is to provide.

In order to solve the above-mentioned problems and achieve such an object, the present invention provides an outer periphery of a tip end of an end mill body that is rotated around an axis line, and moves around the axis line from the tip end of the end mill body toward the rear end side. A plurality of chip discharge grooves that are twisted in the circumferential direction are formed at intervals in the circumferential direction, and a wall surface facing the end mill rotation direction and a wall surface facing the rear side in the end mill rotation direction are formed at the tip portions of these chip discharge grooves. The gashs provided are formed so as to extend in the radial direction with respect to the axis, and bottom blades are respectively formed on the intersecting ridgelines of the wall surfaces of the gashes facing the end mill rotating direction and the end flank of the end mill body. Of these bottom blades, at least one bottom blade has a larger rake angle in the axial direction than the other bottom blades, and a gap connected to the at least one bottom blade. Gash opening angle formed between the wall surface facing the wall surface and the end mill rotating direction rear side facing the end mill rotating direction of the Interview is smaller than the gash opening angle gash continuous to the other end cutting edge, an outer peripheral end of the end cutting edge In the end mill body, a convex curved corner blade that protrudes toward the outer periphery of the tip end of the end mill body as viewed from the end mill rotation direction is formed on a wall surface facing the end mill rotation direction of the gasche connected to the bottom blade . It is characterized by.

  In the end mill configured as described above, at least one bottom blade among the plurality of bottom blades formed at the end of the end mill body has a larger rake angle in the axial direction than the other bottom blades, and these bottom blades are covered. The resistance at the time of biting on the cutting material is different. For this reason, vibrations can be prevented from being excited by periodic action of equal resistances, and chatter vibrations can be prevented from occurring even when the thin portion of the turbine blade is cut. can do.

  On the other hand, the gash connected to at least one bottom blade whose axial rake angle is increased in this way has a gash opening angle formed by the wall surface facing the end mill rotation direction and the wall surface facing the rear side in the end mill rotation direction. Conversely, the gouache opening angle of the other bottom blade having a smaller axial rake angle is larger than the gouache opening angle of the at least one bottom blade. Therefore, even in a bottom blade having a small axial rake angle, which is an inclination with respect to the axis of the wall surface facing the end mill rotation direction of the gasche that becomes the rake face of the bottom blade, it can be avoided that the opening width of the gasche becomes small. It is possible to prevent the chips generated by the bottom blade from becoming clogged.

  In addition, by reducing the gash opening angle of the gasche connected to at least one bottom blade whose axial rake angle is increased in this way smaller than the other bottom blades, the opening width of the gash of each bottom blade as described above can be obtained. Since uniformization can be achieved, especially when a plurality of the above-mentioned bottom blades are arranged at equal intervals in the circumferential direction, the width seen from the front end side in the axial direction of the front end flank connected to each bottom blade is also uniform. Therefore, the thickness of the back metal can be made constant between the plurality of bottom blades. For this reason, it is possible to prevent the formation of a bottom blade with a small back metal thickness, to ensure the strength of the cutting blade for all the bottom blades, and to prevent the occurrence of defects and perform stable cutting. It becomes possible. These are particularly effective in a multi-blade end mill in which the gash opening width and the back metal thickness must be limited.

The configuration of the present invention can also be applied to a square end mill as described in Patent Document 2. However, when cutting a curved surface shape such as a turbine blade, Since a radius end mill having a convex curved corner blade that is convex on the outer peripheral end of the end mill body as viewed from the end mill rotation direction is often used at the outer peripheral end, the present invention has the above-described configuration. Applies to radius end mills . And in this case, in the present invention, the corner blade is formed on the wall surface facing the end mill rotation direction of the gasche connected to the bottom blade , whereby the axial rake angle of the corner blade is also Since the corner blades connected to the at least one bottom blade and the corner blades connected to the other bottom blades have different sizes, chatter vibration can be suppressed even when cutting is performed exclusively using the corner blades. .

  As described above, according to the present invention, it is possible to suppress the occurrence of chatter vibration even when the thin portion of the turbine blade is cut, and it is good to prevent the opening width of the gasche from being widened or narrowed. The chip can be easily discharged, and if the bottom blades are evenly spaced, the thickness of the back metal can be made uniform, so the cutting edge strength is maintained and stable cutting is performed. Can do.

It is a perspective view which shows one Embodiment of this invention. It is a side view of embodiment shown in FIG. It is an enlarged front view of embodiment shown in FIG. 2A is an enlarged side view showing the vicinity of a first bottom blade, and FIG. 2B is an enlarged side view showing the vicinity of a second bottom blade of the embodiment shown in FIG. 1.

  1 to 4 show an embodiment of the present invention. In this embodiment, the end mill body 1 is formed in a substantially cylindrical shape centering on the axis O by a hard material such as cemented carbide, and the rear end portion (the upper right side portion in FIG. 1 and the right side portion in FIG. 2) is The shank portion 2 remains in a cylindrical shape, and the tip portion (lower left portion in FIG. 1 and left portion in FIG. 2) is a cutting edge portion 3. In such an end mill, the shank portion 2 is gripped by a spindle of a multi-axis NC machine tool or the like and rotated in the end mill rotation direction T around the axis O, and the cutting edge portion 3 makes a thin difficult-to-cut material such as a turbine blade. Used for cutting.

  On the outer periphery of the cutting edge 3 at the front end of the end mill body 1, there is a chip discharge groove 4 extending so as to twist toward the rear side in the end mill rotation direction T around the axis O as it goes from the front end of the cutting edge 3 toward the rear end. Plural strips (12 strips in this embodiment) are formed at intervals in the direction. An outer peripheral edge 5 having a rake face as the wall surface 4a is formed on the outer peripheral side ridge portion of the wall surface 4a facing the end mill rotation direction T of the chip discharge grooves 4, and therefore the cutting edge portion 3 of the end mill body 1 is formed. The outer peripheral blades 5 of the same number as the chip discharge grooves 4 are formed to be twisted to the rear side in the end mill rotation direction T around the axis O as it goes to the rear end side. The twist angle of these outer peripheral blades 5 is equal to each other in every other outer peripheral blade 5 in the circumferential direction and different in the outer peripheral blades 5 adjacent to each other in the circumferential direction. The angle is different from that of the outer peripheral blade 5. The radial rake angles (outer rake angles) of these outer peripheral blades 5 are equal to each other.

  On the other hand, a groove-like gash 6 is formed at the tip of the cutting edge portion 3 so as to cut out the tip surface of the end mill body 1 from the tip of the chip discharge groove 4 toward the inner peripheral side. The gasche 6 includes a wall surface 6a facing the end mill rotation direction T and a wall surface 6b facing the rear side of the end mill rotation direction T, and has a V-shape that opens to the distal end side of the end mill body 1 in a side view as shown in FIG. However, both wall surfaces 6a and 6b are inclined so as to be directed toward the rear side in the end mill rotation direction T toward the rear end side in the axis O direction, and the inclination angle with respect to the axis O is more toward the wall surface 6b than the wall surface 6a. Has been increased.

  Further, on the front end surface of the end mill body 1, a front end flank 7 that is inclined toward the rear end side in the axis O direction is formed between the adjacent gashes 6 in the circumferential direction toward the rear side in the end mill rotation direction T. ing. And the bottom blade 8 is formed in the intersection ridgeline part of these front flank 7 and the wall surface 6a which faces the said end mill rotation direction T of the gasche 6 adjacent to the end mill rotation direction T side of each front flank 7. Yes. Accordingly, the wall surface 6a of the gasche 6 facing the end mill rotation direction T is a rake face of the bottom blade 8, and the inclination angle formed by the wall surface 6a with respect to the axis O is the rake angle θ of the bottom blade 8 in the axial direction. The same number of bottom blades 8 as the outer peripheral blades 5 are formed in the cutting blade portion 3.

  Here, in this embodiment, the bottom blade 8 is formed so as to extend linearly from the position of the axis O to the outer peripheral side as shown in FIG. 3 when viewed from the front side of the axis O direction. The rake angle in the direction is set to 0.4 °, and a plurality of bottom blades 8 are arranged at equal intervals in the circumferential direction. Each bottom blade 8 is positioned on one plane perpendicular to the axis O, or on one concave conical surface slightly recessed toward the rear end side in the axis O direction toward the inner peripheral side. Further, on the front end surface of the end mill body 1, the groove-shaped gash 6 is formed such that the groove depth gradually decreases toward the inner peripheral side, and the front end flank 7 increases in the circumferential direction as it goes toward the inner peripheral side. Is formed so that its width gradually decreases.

  Further, the corner portion where the bottom blade 8 and the outer peripheral blade 5 intersect with each other is rounded into a convex curve shape contacting the bottom blade 8 and the outer peripheral blade 5 when viewed from the end mill rotation direction T. A convex curved corner blade 9 such as a convex arc that is convex is formed on the outer peripheral side of the tip of the main body 1. That is, the end mill of this embodiment is a radius end mill. Here, the corner blade 9 is formed on the wall surface 6 a facing the end mill rotation direction T of the gash 6 connected to the bottom blade 8. Therefore, the axial rake angle of the corner blade 9 is made equal to the axial rake angle θ of the bottom blade 8 connected to the corner blade 9.

  Of the plurality of bottom blades 8 formed on the cutting blade portion 3, at least one bottom blade 8 has an axial rake angle θ larger than that of the other bottom blades 8, and the at least one bottom blade 8 has The gash opening angle δ formed by the wall surface 6a facing the end mill rotation direction T of the continuous gasche 6 and the wall surface 6b facing the rear side of the end mill rotation direction T is made smaller than the gash opening angle δ of the gash 6 connected to the other bottom blade 8. ing. Accordingly, the axial rake angle of the corner blade 9 connected to the at least one bottom blade 8 is also made larger than the axial rake angle of the corner blade 9 connected to the other bottom blade 8.

  Specifically, in the present embodiment, the first bottom blade 8A having a large axial rake angle θA as shown in FIG. 4A and the axial rake angle θA as shown in FIG. 4B. The second bottom blades 8B having a small axial rake angle θB are alternately arranged in the circumferential direction. Therefore, the first gash 6A connected to the first bottom blade 8A has a small gash opening angle δA, and the second gash 6B connected to the second bottom blade 8B has a gash opening angle larger than the gash opening angle δA. δB. The axial rake angles θA and θB are both smaller than the torsion angle (axial rake angle) of the outer peripheral blade 5. Further, the clearance angle of the bottom blade 8 by the tip flank 7 is made equal between the first and second bottom blades 8A and 8B.

  In the end mill thus configured, first, the axial rake angles θ of the plurality of bottom blades 8 formed at the tip of the end mill body 1 are different from each other between the first and second bottom blades 8A and 8B. , ΘB, and the resistance when the bottom blade 8 bites the work material is the first bottom blade 8A having a larger axial rake angle θA than the second bottom blade 8B having a smaller axial rake angle θB. Are smaller and have different sizes. For this reason, even if the bottom blades 8 are arranged at equal intervals in the circumferential direction, equal resistance does not act periodically, and vibration is excited by such equal resistance and chatter vibration. Can be suppressed.

  Moreover, in the end mill of this embodiment which is a radius end mill, the axial rake angle of the corner blade 9 connected to the outer peripheral end of the bottom blade 8 is also different in size between those connected to the first and second bottom blades 8A and 8B. Therefore, even when such a corner blade 9 is used to cut a curved surface portion, occurrence of chatter vibration can be suppressed. Therefore, in cutting of a thin part of a work material having many curved parts such as a turbine blade, the machining accuracy is reduced due to chatter vibration of the end mill body 1 itself or vibration of the work material accompanying this. Can be prevented.

  Further, in the end mill having the above configuration, the first and second bottom blades 8A and 8B having different axial rake angles θA and θB are connected to the first bottom blade 8A having a large axial rake angle θA. The gash opening angle δA of the first gash 6A is made smaller than the gash opening angle δB of the second gash 6B connected to the second bottom blade 8B having a small axial rake angle θB.

  For this reason, compared with the case where these gash opening angles δA, δB are made equal, for example, as an average, the wall surface 6b facing the back side in the end mill rotation direction T of the gash 6 from the bottom blade 8 and the tip clearance adjacent to the end mill rotation direction T The opening width of the gash 6 up to the intersection ridge line with the surface 7 (for example, as shown in FIG. 3, when viewed from the front in the direction of the axis O, the bottom blade 8 and the end mill rotation direction T of the gash 6 on which the bottom blade 8 is formed. The included angle α) formed by the straight line L connecting the outermost point P of the intersecting ridge line portion between the wall surface 6b facing the rear side and the tip flank 7 adjacent to the end mill rotation direction T and the axis O is a first angle. While it becomes smaller in the gash 6A, it becomes larger in the second gash 6B.

  That is, even with the first and second bottom blades 8A and 8B having different axial rake angles θA and θB, the opening width of the gash 6 can be made uniform, for example, the opening width can be made constant. It is possible to avoid the generation of clogging of the chips generated by the bottom blade 8 in the gash 6 having a small opening width by avoiding the extreme wideness between the two. In order to make the gash opening angle δ different from each other in this manner, the disc-shaped grinding wheel forming the first and second gashs 6A and 6B has a convex V-shaped sandwich angle formed by the cross section of the outer peripheral surface thereof. The center axis of the same grinding wheel may be inclined with respect to the axis O of the end mill main body 1 in different ways.

  Further, in the present embodiment, since the first and second bottom blades 8A and 8B are arranged at equal intervals in the circumferential direction, by making the opening width of the gash 6 uniform as described above, The width of the tip flank 7 between the opening of the gash 6 and the bottom blade 8 (for example, the crossed ridge line portion L and the bottom adjacent to the end mill rotation direction T in the front view of the axis O direction as shown in FIG. The included angle β) formed by the blades 8 can also be made uniform, for example, by making the tip flank 7 connected to each bottom blade 8 constant, for example. Therefore, the thickness of the back metal portion that supports the bottom blade 8 connected to the rear side in the end mill rotation direction T of the bottom blade 8 can be made uniform, and the cutting edge strength of the bottom blade 8 can be made uniform. Thus, it is possible to prevent the occurrence of defects and the like, and to perform stable cutting even on difficult-to-cut materials.

  In particular, the end mill of the present embodiment is a multi-blade end mill in which 12 outer peripheral blades 5, a bottom blade 8, and a corner blade 9 are formed. Since the circumferential interval between the bottom blades 8 becomes small, the opening width of the gash 6 and the width of the tip flank 7 must be limited. Therefore, in such a multi-blade end mill, it is particularly effective to ensure the chip dischargeability and the cutting edge strength by making the opening width of the gash 6 and the width of the tip flank 7 uniform as described above. is there. Furthermore, in this embodiment, since the rake angle in the radial direction of the outer peripheral blade 5 is also constant, the cutting blade strength can be made uniform.

Furthermore, in the present embodiment, the present invention is applied to a radius end mill in which a convex curved corner blade 9 is formed on the outer peripheral end of the bottom blade 8, and a work material having many curved portions such as a turbine blade is used. For cutting, a radius end mill having a curved corner blade 9 is exclusively used , which is effective.

  In this embodiment, the bottom blades 8A and 8B having two types of axial rake angles θA and θB, and the two types of gashes 6A and 6B having two types of gash opening angles δA and δB connected to the bottom blades 8A and 8B are circumferential. The axial rake angle θ and the gash opening angle δ may be three or more types. Furthermore, such a pair of the bottom blade 8 and the gash 6 may not be arranged in the order of the rake angle θ and the gash opening angle δ alternately in the circumferential direction or in the axial direction. Furthermore, the torsion angles of the outer peripheral blades 5 may be equal to each other.

DESCRIPTION OF SYMBOLS 1 End mill main body 2 Shank part 3 Cutting blade part 4 Chip discharge groove 5 Peripheral blade 6 (6A, 6B) Gash 6a Wall surface which faces end mill rotation direction T of gash 6 6b Wall surface which faces end mill rotation direction T rear side of gash 6 7 Tip Flank 8 (8a, 8B) Bottom blade 9 Corner blade O Axis of end mill body 1 End mill rotation direction θ (θA, θB) Axial rake angle of bottom blade 5 δ (δA, δB) Gash opening angle

Claims (2)

A plurality of chip discharge grooves that are twisted around the axis as it goes from the front end of the end mill main body toward the rear end side are formed on the outer periphery of the end portion of the end mill main body rotated about the axis at intervals in the circumferential direction. In addition, a gash having a wall surface facing the end mill rotation direction and a wall surface facing the rear side in the end mill rotation direction is formed at the front end portions of the chip discharge grooves so as to extend in a radial direction with respect to the axis. A bottom blade is formed at each of the intersecting ridge line portions of the wall surface facing the end mill rotation direction and the tip flank of the end mill body, and at least one of the bottom blades is more axial than the other bottom blades. A wall surface facing the end mill rotation direction of the gasche connected to the at least one bottom blade and the end mill rotation direction while the rake angle is increased Gash opening angle formed between the wall surface facing the square side is smaller than the gash opening angle gash continuous to the other end cutting edge, on the outer peripheral edge of the bottom blade, the tip of the end mill body as viewed from the end mill rotating direction An end mill characterized in that a convex curved corner blade that protrudes toward the outer peripheral side is formed on a wall surface facing the end mill rotation direction of the gasche connected to the bottom blade .   The end mill according to claim 1, wherein the plurality of bottom blades are arranged at equal intervals in the circumferential direction.

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