JP2011045959A - End mill and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an end mill and its manufacturing method which can obtain a highly accurate working surface having no fall nor swell without deteriorating workability when a working surface such as a high vertical wall is formed in a material to be ground by the end mill large in an L/D, or when a material of high hardness having relatively high cutting resistance is worked or in the case of a working operation by an end mill whose rake angle is negative. <P>SOLUTION: In the end mill, an outer peripheral cutting edge 5 is formed which is twisted around an axis O in an outer periphery of an end of an end mill body 1 rotated around the axis O. A locus of the rotation of the outer peripheral cutting edge 5 on the axis O is cyclically recessed and projected in the diametrical direction relative to the axis O at pitches P (lead of outer peripheral cutting edge 5/number of teeth of outer peripheral cutting edge 5) toward a rear end side from an end of the outer peripheral cutting edge 5. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an end mill in which an outer peripheral blade is formed on the outer periphery of a tip end portion of an end mill main body rotated about an axis, and a method for manufacturing the end mill.

  In an end mill that forms a machined surface such as a vertical wall by subjecting a workpiece such as a mold to side cutting, the vertical wall to be formed is high, and the edge length L of the outer peripheral blade of the end mill is the outer diameter of the outer peripheral blade. When the ratio L / D to D is inevitably large, or when processing with an end mill whose negative angle is easy to machine a hard material with relatively high cutting resistance, In addition, the end mill body easily bends due to cutting resistance, and the machined surface tends to fall or swell in the axial direction of the end mill body (the height direction of the vertical wall). Among these, as described in Patent Documents 1 to 3, for example, as described in Patent Documents 1 to 3, the outer peripheral blade is back-tapered so that the outer diameter D becomes slightly smaller toward the rear end side. It has been.

JP 2004-209559 A JP 2005-319538 A JP 2007-245278 A

  On the other hand, in order to suppress the waviness of the processed surface, for example, it is conceivable to reduce the twist angle of the outer peripheral blade. However, if the torsion angle is reduced, the back component force acting on the end mill main body becomes larger than the thrust force, so that the tilting is likely to occur, and as a result, a good machined surface cannot be obtained. For this reason, if the work surface such as a vertical wall with high height is precisely formed on the work material by an end mill with a large L / D, or if the work is performed by an end mill where the high-hardness material is easy to machine and the corner is negative For example, after forming the processed surface by side cutting, the swell must be removed by finishing the processed surface by reducing the cut depth, and it is inevitable that the processing efficiency is impaired.

  The present invention has been made under such a background. When an end mill having a large L / D is used to form a work surface such as a vertical wall having a high height on a work material, a high cutting resistance is high. Providing an end mill that can provide a highly accurate machined surface that does not fall or undulate without impairing machining efficiency, even when processing hard materials or end mills with a rake angle of negative. The purpose is to do.

  In order to solve the above problems and achieve such an object, the end mill of the present invention has an outer peripheral blade that is twisted around the axis on the outer periphery of the tip of the end mill body that is rotated around the axis. The end mill is configured such that the rotation trajectory of the outer peripheral blade around the axis is periodically rotated at a pitch of the outer peripheral blade from the front end side toward the rear end side (lead of outer peripheral blade / number of outer peripheral blades). It is uneven | corrugated in the radial direction with respect to.

  Further, the manufacturing method of the end mill of the present invention for manufacturing such an end mill cuts a work material by a pre-processing end mill in which the rotation locus around the axis of the outer peripheral blade is parallel to the axis. Measuring the waviness of the processed surface of the work material formed by the outer peripheral edge of the pre-processing end mill, and forming the outer peripheral edge of the end mill of the present invention so that the rotation locus becomes an unevenness obtained by inverting this waviness. It is characterized by.

  Here, in the case of side cutting by an end mill, the waviness of the processed surface by one outer peripheral blade depends on the lead of the outer peripheral blade and the cutting depth in the radial direction. For example, when side cutting is performed by down-cutting with a general right-handed right-handed end mill, the work is not performed until the cutting edge reaches the depth of cut after the tip of the outer peripheral edge bites into the work material. Since the cutting resistance also increases as the length of the outer peripheral blade cut into the material gradually increases along the lead, the end mill body usually bends away from the work material and the deflection becomes larger.

  Next, in a state where the tip of the outer peripheral blade is pulled out of the work material and the outer peripheral blade is cut into the entire cutting portion of the work material, the length of the outer peripheral blade cut into the work material is constant. Therefore, although the cutting resistance is constant, the position where the resistance acts moves from the front end side to the rear end side in the axial direction of the end mill body. The undulation gradually becomes the direction toward the work material side in the height direction.

  Further, the length of the outer peripheral blade cut into the work material becomes shorter and the cutting resistance gradually decreases until the rear end side of the outer peripheral blade bites into the upper end surface side of the work material and then comes out. Since the position where the resistance acts continues to move toward the rear end side, the bending of the end mill body is abruptly reduced and the undulation is reduced, and the bending undulation is also reduced to 0 when the rear end side of the outer peripheral blade comes out of the work material. Become.

  Similarly, when side cutting is performed by up-cutting with a right-blade right-twisting end mill, the end mill body is bent away from the work material for a short time after the tip of the outer peripheral edge bites into the work material. However, the machined surface also protrudes from the work material, but as the outer peripheral edge is cut into the work material, the end mill body acts so as to pull the work material in the radial direction, and the work material becomes the mold. In the case of such a high rigidity, the end mill body is bent so as to bite into the work material, and the waviness of the machined surface suddenly moves toward the work material.

  Next, when the outer peripheral blade is cut into the entire cutting part of the work material, the cutting resistance becomes constant and the position where the resistance acts moves to the rear end side of the end mill body as in the case of the down cut. The bending becomes smaller and the end mill body moves away from the state of being cut into the work material side, and the waviness of the machined surface is also gradually protruded from the direction of biting into the work material side. Furthermore, the length of the outer peripheral blade that is cut into the work material gradually decreases and the cutting resistance decreases until the rear end side of the outer peripheral blade bites into the upper end surface of the work material and then comes out. The bending of the end mill body and the sagging of the processed surface are also reduced, and become 0 when the outer peripheral edge comes out of the work material.

  In addition, the cutting depth in the axial direction in which the outer peripheral blade is cut into the work material after the tip of the outer peripheral blade bites into the work material and then comes out, and the outer peripheral blade is constant over the entire cutting portion of the work material. The depth of cut in the axial direction during the length of the cut and the depth of cut in the axial direction from when the rear edge of the outer peripheral edge bites into the upper end surface of the work material until it is pulled out The rotation of the end mill body determines the radial cutting depth of the workpiece by the rotation of the end mill body and the product of the rotation angle of the end mill body and the lead of the outer periphery blade.

  In other words, one outer peripheral blade forms a swell with a fixed shape on the machined surface by cutting the end mill body while the end mill body is deflected for each rotation of the end mill body. If these outer peripheral blades are formed with equal leads and at equal intervals, the undulations of the outer peripheral blades (peripheral blade leads / peripheral blades) during one rotation of the end mill main body. Are shifted in the height direction of the vertical wall by the pitch of the number of blades) and overlapped to form a processed surface so as to form periodic irregularities in the height direction.

  Therefore, when offsetting such waviness of the machined surface by forming irregularities opposite to the irregularities of the waviness on the outer peripheral blade, the end mill of the present invention has an outer periphery in accordance with the pitch at which the waviness is shifted. The rotation trajectory of the blade around the axis is periodically uneven in the radial direction with respect to the axis at a pitch of the outer peripheral blade from the front end to the rear end side (lead of outer peripheral blade / number of outer peripheral blades). . Therefore, according to the end mill configured as described above, when a work surface such as a vertical wall having a high height is formed on a work material, even if the L / D of the end mill main body is large and bending is likely to occur, It is possible to prevent the surface from waviness or toppling, and thereby it is possible to form a highly accurate processed surface by one side cutting, and it is possible to improve the processing efficiency.

  Here, the size and shape of the unevenness of the outer peripheral blade can be obtained by calculation based on, for example, various processing conditions, but in the manufacturing method of the end mill of the present invention, first, the rotation locus around the axis of the outer peripheral blade. The workpiece is cut in advance by a pre-processing end mill parallel to the axis, and the waviness of the work surface of the work material formed by the outer peripheral edge of the pre-processing end mill is measured to determine the rotation trajectory. The outer peripheral blade in the end mill of the present invention is formed so that the undulation is reversed, and the unevenness of the outer peripheral blade is set on the basis of the undulation actually generated on the machined surface, so the accuracy is further increased. It is possible to provide an end mill capable of forming the processed surface.

  As described above, according to the end mill of the present invention, even if the L / D of the end mill main body is large and easily bends, it is possible to suppress the occurrence of waviness or collapse on the processed surface and smooth the surface by one side cutting. A machined surface can be formed, and machining accuracy and machining efficiency can be improved. In addition, according to the manufacturing method of the present invention, such an end mill can be manufactured accurately and reliably.

It is a side view which shows one Embodiment of the end mill of this invention. It is an enlarged view which shows the rotation locus | trajectory of the outer periphery blade of embodiment shown in FIG. 1 (however, for the sake of description, the unevenness | corrugation of an outer periphery blade is exaggerated and drawn according to FIG. 3). It is an expanded sectional view of the processing surface cut by the end mill for preliminary processing in the manufacturing method of the end mill of the present invention.

  1 to 3 show an embodiment of an end mill and a manufacturing method thereof according to the present invention. In the end mill of 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 side portion (the right side portion in FIG. 1) remains cylindrical. The shank portion 2 and the tip side portion (left side portion in FIG. 1) are the cutting edge portion 3, and the shank portion 2 is held by the spindle of the machine tool and rotated in the end mill rotating direction T around the axis O. By being sent out in the direction intersecting the axis O, the cutting material is used to cut the work material.

  On the outer periphery of the cutting edge portion 3, a plurality of chip discharge grooves 4 that are twisted toward the rear side in the end mill rotation direction T around the axis O from the front end to the rear end side are formed. The outer peripheral blades 5 are respectively formed on the outer peripheral side ridges of the wall surface facing the end mill rotation direction T side. Therefore, in the present embodiment, a plurality of outer peripheral blades 5 are spirally formed around the axis O along the end mill rotation direction T rearward in the direction from the front end to the rear end side in accordance with the twist of the chip discharge groove 4 in the same manner as the chip discharge groove 4. It is formed so as to be twisted.

  Here, these outer peripheral blades 5 are formed so as to be twisted at a constant twist angle equal to each other, and extend in the direction of the axis O during one rotation around the axis O along the outer peripheral blade 5, That is, the leads are made equal to each other. Moreover, the circumferential intervals of the outer peripheral blades 5 are also equally spaced from each other.

  A concave groove-like gash 6 extending from the chip discharge groove 4 to the inner peripheral side is formed at the tip of the end mill body 1, and the edge of the wall facing the end mill rotation direction T of the gash 6 A bottom blade 7 extending from the tip of the outer peripheral blade 5 to the inner peripheral side of the end mill body 1 is formed in the portion. Here, the end mill of the present embodiment is a square type end mill in which the outer peripheral blade 5 and the bottom blade 7 are substantially orthogonal to each other in a rotation locus around the axis O. However, in this embodiment, the gash 6 extends until it reaches the outer periphery of the end mill body 1, and the tip 5A of the outer peripheral blade 5 is located on the outer peripheral side ridge of the wall surface of the gash 6 facing the end mill rotation direction T. The tip portion 5A has a length of about 0.3 mm and a taper of about 3/100, for example, as it goes toward the tip side. It inclines toward the side and intersects with the outer peripheral end of the bottom blade 7.

  The rotation trajectory around the axis O of the outer peripheral blade 5 excluding the tip 5A is irregular in the radial direction with respect to the axis O periodically at a predetermined pitch P along the axis O direction as shown in FIG. The pitch P is a length obtained by dividing the lead of the outer peripheral blade 5 by the number of outer peripheral blades, that is, (lead of the outer peripheral blade 5 / number of blades of the outer peripheral blade 5). Further, the shape of the unevenness of the outer peripheral blade 5 that is uneven in the radial direction as described above is obtained when the work material is side-cut by a normal end mill in which the rotation locus around the axis of the outer peripheral blade is a cylindrical surface parallel to the axis. A shape obtained by reversing the waviness of the above-described processed surface is generated.

  Here, FIG. 3 shows a measurement of the waviness of the machined surface when the workpiece is side cut, using such a normal end mill as a pre-processing end mill in an embodiment of the end mill manufacturing method of the present invention. Yes, cutting was done by down-cutting. This pre-processing end mill is the same as the end mill of the embodiment except that the rotation trajectory of the outer peripheral blade is not uneven, and the outer diameter of the outer peripheral blade is 10 mm, the lead is 31.4 mm, the twist angle is 45 °, The number is 6, the rake angle of the outer peripheral edge is negative, the material of the end mill body is ultrafine grain cemented carbide, and the L / D of the cutting edge is 2.5.

The work material was SKD11 (60HRC), and the cutting conditions were an axial depth of cut of 15 mm, a radial depth of cut of 0.2 mm, a rotational speed of 1800 min ⁻¹ , a cutting speed of 57 m / min, and a feed speed of 260 mm / min. Min (feed per blade: 0.024 mm), and dry cutting by air blow.

  As shown in FIG. 3, in one cycle of undulation formed on the machining surface, the work material is moved in the height direction of the machining surface (vertical wall) from the bottom surface (position at a distance of 15 mm from the top surface) of the machining surface. Towards the upper end surface (position at a distance of 0 mm from the upper end surface), a cross-sectional angle is shown with respect to the position where the smooth machining surface is to be formed (the position of the machining surface is 0 mm). The position of the processed surface at the apex is about 0.02 mm. Such waviness is continuous at a pitch of 5.2 mm which is the (rear edge / lead of outer edge) of the pre-processing end mill. However, the portion intersecting with the bottom surface of the processed surface (vertical wall) is tapered toward the bottom surface side because the tip portion 5A of the outer peripheral blade 5 is tapered with the above-described gash land. It is formed so as to gradually protrude.

  Therefore, the end mill of the present embodiment is formed so that the rotation trajectory of the outer peripheral blade 5 is uneven with a shape and dimensions in which the waviness of the processed surface is substantially reversed. Here, in the present embodiment, the outer peripheral blade 5 protrudes gradually from the front end side toward the rear end side with a steep slope with respect to the axis O except for the front end portion 5A to which the gash land is applied. , And then gradually forms a mountain shape that gradually slopes toward the axis O (inner circumference), and further inclines toward the axis O with a steeper slope than this. It has been repeated.

  Therefore, the pitch P of the unevenness is 5.2 mm as described above (lead of the outer peripheral blade 5 / number of blades of the outer peripheral blade 5), and from the concave portion of the concave and convex portion to the most convex vertex. The amount of protrusion in the radial direction is about 0.014 mm, and the rotation trajectories of the plurality of outer peripheral blades 5 are made to coincide with each other. However, as described above, the rotation trajectory of the outer peripheral blade 5 is a concavo-convex curve in a portion where the peak or slope of the waviness of the machining surface having a mountain shape changes, or in a portion corresponding to a valley portion which is a concave between adjacent mountains. It is rounded more smoothly.

  When the side milling of the work material is performed by down-cutting under the same conditions as the cutting conditions by the pre-processing end mill by the end mill of this embodiment having such an outer peripheral blade 5, the tip of the outer peripheral blade 5 becomes the work material. Since the end mill body 1 bends until it reaches the cutting depth in the radial direction after it bites and exits from the work material, the outer diameter of the outer peripheral blade 5 gradually increases toward the rear end side. This portion can be cut smoothly.

  Further, in a state where the tip of the outer peripheral blade 5 has come out of the work material and the outer peripheral blade 5 has been cut into the entire cutting portion of the work material, the bending of the end mill body 1 is gradually reduced, and the machining surface becomes gentle. Although the outer peripheral blade 5 is gradually retracted to the axis O side while trying to go to the work material side, the processing until the rear end side of the outer peripheral blade 5 bites on the upper end surface side of the work material and then comes out. In the portion where the undulation of the surface decreases with a steep slope, the outer peripheral blade 5 also moves toward the axis O side with a steep slope, and as a result, the smoothness of the processed surface can be maintained.

  As described above, according to the end mill having the above-described configuration, it is possible to form a smooth processed surface regardless of the bending of the end mill main body 1, and this is because the corner of the high hardness material having a relatively high cutting resistance is easily processed. Even if the machining by the end mill or the L / D of the cutting edge portion 3 is large, it does not change. For this reason, even when a vertical wall with a high height is formed on the work material, it is possible to obtain a highly accurate processed surface by one side cutting, which can improve both the processing accuracy and the processing efficiency. it can.

  Further, in the above manufacturing method when manufacturing such an end mill, the work material is cut in advance under the same cutting conditions by a pre-processing end mill in which the rotation locus of the outer peripheral blade is parallel to the axis, and the processing surface Since the unevenness with the undulations reversed is given to the outer peripheral blade 5, it becomes possible to manufacture an end mill that can form the smooth processed surface as described above more reliably.

  In the present embodiment, the end mill that performs cutting by down-cutting has been described, but even in the case of up-cutting, the unevenness obtained by reversing the waviness of the above-described processing surface is directed from the front end of the outer peripheral blade toward the rear end side, What is necessary is just to form an outer periphery blade so that the rotation locus | trajectory which may be periodically repeated with the pitch of (lead of outer periphery blade / number of blades of outer periphery blade) may be made. In this case as well, the workpiece can be cut by up-cutting with a pre-processing end mill whose outer track is parallel to the axis, and the outer track can be set based on the waviness of the machined surface at that time. .

DESCRIPTION OF SYMBOLS 1 End mill main body 2 Shank part 3 Cutting blade part 4 Chip discharge groove 5 Outer peripheral blade 6 Gash 7 Bottom blade O End mill main body 1 axis T End mill rotation direction P The pitch at which the rotation locus of the outer peripheral blade 5 is uneven

Claims (2)

  An end mill in which an outer peripheral blade that is twisted about the axis is formed on the outer periphery of a tip end portion of an end mill main body that rotates about an axis, and the rotation trajectory of the outer peripheral blade about the axis is on the tip side of the outer peripheral blade An end mill characterized in that it is uneven in the radial direction with respect to the axis periodically at a pitch of (lead of outer peripheral blade / number of blades of outer peripheral blade) toward the rear end side.   The work material is cut by a pre-processing end mill whose rotation trajectory around the axis of the outer peripheral blade is parallel to the axis, and the undulation of the work surface of the work material formed by the outer peripheral blade of the pre-processing end mill The end mill outer peripheral blade according to claim 1 is formed so that the rotation trajectory becomes irregularities obtained by inverting the waviness.

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