JP2007229849A - Endmill, and machining method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an endmill which can accurately and efficiently machine a three-dimensional recessed curved surface to be used in a jet engine, etc., and further to provide a machining method using the same endmill. <P>SOLUTION: A circular arc cutting edge 11 of a cutting edge portion formed on the tip end portion of a shank 13 is formed so as to have a shape to be inscribed to an imaginary body 15 of revolution formed by turning a circular arc 14 about a rotary axis 12. The center of the circular arc is positioned on the shank side so as to separate from the rear end 16 of the circular arc cutting edge by a specified distance. By this configuration, the tilting angle of the rotary axis with respect to the common tangent of the circular arc cutting edge of the endmill 10 and the surface to be machined can be set to be large. Therefore, the shank does not interfere with the edge portion of the recessed curved surface to be machined when, for example, a central flat surface portion of the recessed curved surface to be machined, such as a blade of the jet engine, is being machined by means of the circular arc cutting edge. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an end mill suitable for processing a three-dimensional concave curved surface such as a jet engine blade and a processing method using the end mill.

  Conventionally, when a concave curved surface shape such as a jet engine blade is processed by a 5-axis numerically controlled machine tool, a ball end mill in which a hemispherical cutting edge portion having the same diameter as the shank is formed at the tip of the shank is used. Further, in Patent Document 1, as shown in FIGS. 2 and 3 of Patent Document 1, an end mill body 1 is provided with an arcuate cutting edge 4 at one end in the axial direction and a solid with a shank 7 at the other end. In the end mill, an arc blade end mill is described in which the arc radius of the arc-shaped cutting edge is 0.6 to 3 times the blade diameter.

According to this arc-blade end mill, the radius of the arc-shaped cutting edge for machining the workpiece is larger than the radius of the shank. The height is reduced, and particularly steep slopes such as dies can be processed with high cutting efficiency.
Japanese Patent Laid-Open No. 11-156621 (second page, FIGS. 2 and 3)

  In the above-described arc-blade end mill, as described in paragraph [0006] of Patent Document 1, when the arc radius is 0.6 times the end mill diameter, an inclined surface of about 30 degrees from the end mill axis is allowed. Can be cut.

  However, in such an arc blade end mill, as shown in FIG. 3 of Patent Document 1, the center of the arc of the arc blade 4 is located on a straight line orthogonal to the end mill axis at the rear end of the arc blade 4. The inclination angle of the end mill shaft with respect to the common tangent line between the arcuate blade 4 and the work surface cannot be increased. Accordingly, when the arc-blade end mill is mounted on a spindle of a numerically controlled machine tool having a rotation axis that tilts the spindle relative to the workpiece and used for machining a concave curved surface such as a jet engine blade, FIG. As shown, there is a problem that the shank 7 interferes with the edge of the concave surface when the arcuate blade 4 processes the central horizontal surface portion of the concave curved surface. In other words, the arc-blade end mill is premised on the use of a three-axis numerically controlled machine tool whose main axis is always orthogonal to the workpiece, and the main axis rotates relative to the workpiece. Not suitable for use on numerically controlled machine tools with axes.

   The present invention has been made in view of this point, and it is an object of the present invention to provide an end mill capable of machining a concave curved surface of a jet engine or the like with a high surface accuracy with a high cutting efficiency and a machining method using the same.

  In order to solve the above-described problem, a structural feature of the invention according to claim 1 is that a cutting edge portion having a plurality of arc cutting edges in a shape inscribed in a virtual rotating body in which an arc is rotated around a rotation axis, In an end mill having a shank protruding rearward from the cutting edge portion coaxially with the rotation axis, the center of the arc is located a predetermined amount from the rear end of the arc cutting edge, and the radius of the arc Is larger than the maximum radius of the virtual rotating body.

  In Claim 1, the said cutting blade part is formed so that the outer diameter in the said circular cutting edge rear end of the said virtual rotary body may become larger than the outer diameter of the said shank.

  The structural feature of the invention according to claim 3 is that the spindle head is mounted so as to be relatively movable in the directions of the three orthogonal linear axes with respect to the work table holding the workpiece and to be relatively rotatable around at least one rotation axis. A spindle that is rotatably supported by the spindle head and holds a tool at the tip, and a numerical controller that numerically controls linear movement of the spindle head in the three orthogonal directions and rotational movement about the rotation axis; The end mill according to claim 1 or 2 is coaxially held on the main shaft, and the work concave surface to be machined by the end mill and the virtual rotating body are the arc cutting edge portion. The spindle head is moved numerically with respect to the work table so as to come into contact with the workpiece table, and the concave curved surface of the workpiece is machined by the arc cutting edge of the end mill. A.

  In the invention according to claim 1 configured as described above, the arc cutting edge of the cutting edge portion formed at the tip of the shank is formed in a shape inscribed in a virtual rotating body obtained by rotating the arc around the rotation axis, The center of the arc is located on the shank side by a predetermined amount from the rear end of the arc cutting edge. As a result, the inclination angle of the rotation axis with respect to the common tangent line between the arc cutting edge of the end mill and the work surface can be increased, so that, for example, the central horizontal surface portion of the concave work surface such as a jet engine blade is an arc cutting edge. The shank does not interfere with the edge of the concave surface to be processed. Furthermore, since the radius of the arc of the virtual rotating body inscribed by the arc cutting edge is larger than the maximum radius of the virtual rotating body, the end mill is picked between the both ends of the concave surface to be processed at each end and perpendicular to the rotation axis. When a concave curved surface to be processed is processed by an arc cutting edge, high surface accuracy can be obtained even if the pick feed amount is increased to increase the cutting efficiency.

  In the invention according to claim 2 configured as described above, since the outer diameter at the rear end of the arc cutting edge of the virtual rotating body inscribed by the plurality of arc cutting edges is larger than the outer diameter of the shank, the end mill is processed. When feeding between both ends of the concave curved surface in a direction perpendicular to the rotation axis, the height of the cusps left by each arc cutting blade rotating around the rotation axis is reduced, and cutting is performed by increasing the feed movement speed. Even if the efficiency is increased, the concave surface to be processed can be processed with high surface accuracy.

  Furthermore, since the outer diameter at the rear end of the arc cutting edge is processed with the arc cutting edge inscribed in the virtual rotating body larger than the outer diameter of the shank, even if the cutting amount for cutting the cutting edge portion toward the workpiece is increased, The shank does not interfere with the workpiece, and the machining efficiency can be improved.

  In the invention according to claim 3 configured as described above, the end mill according to claim 1 or 2 is configured such that the virtual rotating body inscribed by the arc cutting edge and the concave curved surface to be processed are in contact at the arc cutting edge portion. Since the workpiece is moved by numerical control, the pick feed amount can be increased to process the concave curved surface to be processed with high cutting efficiency and high surface accuracy. When processing the central horizontal surface of the curved surface, the shank does not interfere with the edge of the concave curved surface to be processed.

  Hereinafter, embodiments of an end mill and a processing method using the end mill according to the present invention will be described with reference to the drawings. In FIG. 1, the end mill 10 includes a plurality of, for example, four, arc cutting edges 11 formed by twisting around a rotation axis O, and a shank 13 is coaxial with the rotation axis O from the cutting edge 12. It protrudes backward. Each arc cutting edge 11 has a length L in the rotation axis direction, and the outer peripheral edge of each arc cutting edge 11 is formed in a shape inscribed in a virtual rotating body 15 that rotates the arc 14 around the rotation axis O. .

  The arc cutting edge 11 intersects the outer peripheral surface of the shank 13 at the rear end 16 on the shank 13 side, and the center RO of the arc 14 is positioned on the shank 13 side by a predetermined amount S from the rear end 16 of the arc cutting edge 11. Yes. The radius R of the circular arc 14 is larger than the radius of the shank 13 that is the maximum radius r of the virtual rotating body 15.

As a result, as shown in FIG. 2, the inclination angle α of the rotation axis O with respect to the common tangent line between the arc cutting edge 11 of the end mill 10 and the surface to be machined can be increased. When the arc cutting edge 11 is processing the central horizontal surface portion of the processed concave curved surface 17, the shank 13 does not interfere with the edge portion 18 of the processed concave curved surface 17. Further, as shown in FIG. 3, the radius R of the arc 14 of the virtual rotating body 15 inscribed by the arc cutting edge 11 is larger than the maximum radius of the virtual rotating body 15, so Is picked up at each end and reciprocated in a direction perpendicular to the rotation axis O, and when the work concave surface 17 is machined by the arc cutting edge 11, the pick feed amount Pf is increased in order to increase the cutting efficiency. However, the height h of the cusp 19 left uncut by the arc cutting edge 11 is reduced, and high surface accuracy can be obtained. When the radius of the arc cutting edge 11 is R and the pick feed amount is Pf, the height h of the cusp 19 can be calculated from the formula R ² = (R−h) ² + (Pf / 2) ² .

  When the diameter D of the shank 13 is 20 mm, the radius R of the arc 14 can be 0.6D = 12 mm, 1.0D = 20 mm, 1.5D = 30 mm, 3.0D = 60 mm, 5D = 100 mm, etc. . In particular, when the radius R of the arc 14 is 100 mm, the radius R of the arc 14 is 10 times the radius of the end mill of the hemispherical end mill, so that the concave curved surface 17 to be processed has a high cutting efficiency. And the shank 13 interferes with the edge 18 of the processed concave surface 17 when the arc cutting edge 11 is processing the central horizontal surface portion of the processed concave surface 17. There is no.

  Note that a relief cutting edge may be formed at the tip of the shank 13 following the rear end 16 of the arc cutting edge 11. In this case, the cutting edge portion 12 is constituted by the arc cutting edge 11 and the escape cutting edge.

  In the end mill 21 shown in FIG. 4, the arc cutting edge 11 is formed so that the outer diameter at the arc cutting edge rear end 16 of the virtual rotating body 15 in contact with the arc cutting edge 11 is larger than the outer diameter of the shank 13. ing. Since other configurations are the same as those of the end mill 10, the same reference numerals are assigned to the same elements, and descriptions thereof are omitted.

  As a result, when the end mill 21 is fed and moved in the direction perpendicular to the rotational axis O between both ends of the workpiece concave curved surface 17, the height of the cusp 20 left uncut by each arc cutting edge 11 rotating around the rotational axis O is obtained. Even if the length h is reduced and the feed movement speed v is increased to increase the cutting efficiency, the concave surface to be processed can be processed with high surface accuracy (see FIG. 5). Furthermore, since the outer diameter 2 × r at the rear end of the arc cutting edge 11 is processed by the arc cutting edge 11 inscribed in the virtual rotating body 15 larger than the outer diameter of the shank 13, the virtual rotation at the rear end of the arc cutting edge 11 is performed. The radius r in the cross section perpendicular to the rotation axis O of the body 15 can be machined with the arc cutting blade 11 that is larger than the radius of the largest shank that can be mounted on the main shaft 10, and the cutting edge portion 12 is directed toward the workpiece W. Even if the cutting depth is increased, the shank 13 does not interfere with the workpiece W, and the machining efficiency can be improved.

  In the end mills 10 and 21, the front end portion and the rear end portion of the arc cutting edge 11 are provided with arc portions having a radius smaller than the radius of the virtual rotating body 15 at each end portion, thereby improving the rigidity of the end portion of the arc cutting edge 11. can do.

  Next, hold the end mill coaxially at the tip of the spindle of the 5-axis numerically controlled machine tool, and the spindle is supported so that the workpiece concave surface to be machined by the end mill and the virtual rotating body are in contact with each other at the arc cutting edge. A machining method using an end mill in which the main spindle head is moved relative to the rotary table holding the workpiece by 5-axis numerical control and the workpiece concave surface is machined by the arc cutting blade 11 of the end mill will be described.

   In FIG. 6, a column 24 is supported on a bed 23 of a 5-axis numerically controlled machine tool 22 so as to be movable in the Z-axis direction within a horizontal plane, and a feed screw mechanism having a feed screw rotatably supported on the bed 23; The servomotor 25 that rotationally drives the feed screw is reciprocated in the Z-axis direction. A spindle head 26 is supported on the column 24 so as to be movable in the vertical Y-axis direction, and is moved in the Y-axis direction by a pair of servo motors 27 and a feed screw mechanism (not shown). The spindle head 26 is supported by a spindle 28 that detachably holds the end mill 10 or 21 at the tip in the Z-axis direction, and is driven to rotate by a spindle motor (not shown).

   A table 29 is mounted on the bed 23 so as to face the column 24 so as to be movable in a horizontal plane in the X-axis direction, and is reciprocated in the X-axis direction by a pair of servo motors 30 and a feed screw mechanism (not shown). It has become. A tilt table 31 is supported on the table 29 so as to be rotatable about an A axis parallel to the X axis, and is rotated by a servo motor 32. On the tilt table 31, a rotary table 33 as a work table for holding a work is rotatably supported, and is rotated around the B axis by a servo motor (not shown). A pallet 35 to which the work W is attached is detachably mounted on the rotary table 33. The numerical controller 34 numerically controls the rotation of the servo motors 25, 27, and 30 to linearly move the column 24, the spindle head 26, and the table 29 in the X, Y, and Z axis directions, and numerically determines the rotation of the servo motor 32 and the like. By controlling, the tilt table 31 and the rotary table 33 are rotated around the A and B axes. In this way, the spindle head 26 is mounted on the bed 23 so that it can move relative to the rotary table 33, which is a work table holding the workpiece W, in the three orthogonal linear axes and relative to the two rotary axes. It is built.

  When machining the workpiece concave surface 17 of the workpiece W by the end mill 10 or 21, for example, the end mill 10 is coaxially held at the tip of the main shaft 28 of the 5-axis numerically controlled machine tool 22, and the workpiece W is placed on the rotary table 33. Retained.

  The numerical control device 34 relatively moves the spindle head 26 and the rotary table 33 by 5-axis control so that the virtual rotating body 15 in contact with the arc cutting edge 11 of the end mill 10 is in contact with the workpiece curved surface 17 at the arc cutting edge 11 portion. Then, the table 29 is reciprocated in the X axis direction. That is, as shown in FIG. 7, the numerical controller 34 has a slope β (see FIG. 7) of a tangent to a point P on the cross-sectional curve by the XZ plane of the concave surface 17 to be processed and a tangent perpendicular to the tangent. Regardless of the inclination, the column 24, the spindle head 26, and the table are numerically controlled by controlling the servo motors 25, 27, 30, 32, etc. so that the virtual rotating body 15 of the end mill 10 is in contact with the concave curved surface 17 to be processed at the point P. 29 is moved linearly, and the tilt table 31 and the rotation table 33 are rotated.

  The numerical control device 34 simultaneously controls the relative movement of the spindle head 26 and the rotary table 33 every time the end mill 10 reaches both ends of the workpiece concave curved surface 17 in the X-axis direction to simultaneously control the arc cutting blade 11. Is moved by a pick feed amount Pf in a direction perpendicular to the X axis within the workpiece concave curved surface.

   In this way, the end mill 10 is moved by the 5-axis numerical control with respect to the workpiece W so that the virtual rotating body 15 inscribed by the arc cutting edge 11 and the workpiece concave curved surface 17 are in contact with each other at the arc cutting edge 11 portion. Therefore, it is possible to increase the pick feed amount Pf and process the processed concave curved surface 17 with high cutting efficiency and high surface accuracy, and the arc cutting edge 11 processes, for example, the central horizontal plane portion of the processed concave curved surface 17. The shank 13 does not interfere with the edge 18 of the processed concave curved surface 17 when it is in contact.

   In the above embodiment, this end mill is used for a 5-axis numerical control machine tool that numerically controls the relative linear movement of the spindle head and work table in the X, Y, and Z axis directions and the rotational movement about the A and B axes. The numerically controlled machine tool using this end mill may be a 6-axis numerically controlled machine tool in which the spindle head 26 can be further rotated by numerical control around a rotation axis parallel to the X axis. Further, a seven-axis numerical control device in which the main shaft is moved back and forth by numerical control with respect to the main shaft head may be used. Moreover, you may process using this end mill with the 4-axis numerical control machine tool which numerically controls the linear movement of the spindle head and the work table in the X, Y, and Z-axis directions and the rotational movement around the B-axis.

   Further, for example, in the 5-axis numerically controlled machine tool 22 described above, a rotation mechanism that rotates the work table about two axes is provided so that the end mills 10 and 21 and the work W can be rotated relative to each other. A biaxial rotating mechanism that rotates around the axis may be provided. Furthermore, it is good also as a structure which provides the 1 axis | shaft rotation mechanism which rotates a work table, and the 1 axis | shaft rotation mechanism which rotates a spindle head.

   In the above 5-axis numerically controlled machine tool, the spindle head and the work table are linearly moved in the X, Y, and Z axis directions by the linear guide mechanism, and rotated around the A and B axes by the rotation mechanism. The spindle head is supported by three sets of parallel link mechanisms at equiangular positions in the circumferential direction, and each parallel link mechanism is driven by a servo motor so that the spindle head is orthogonal to the work table by three linear axes. The relative movement in the direction and the rotational movement about the two rotation axes may be performed. Furthermore, a spindle head may be attached to the arm tip of the articulated robot, and the spindle head may be moved in the directions of three orthogonal linear axes and rotated about two rotation axes.

The figure which shows the end mill which concerns on this Embodiment. The figure which shows the inclination-angle of a rotating shaft line with respect to the common tangent of the circular arc cutting edge of an end mill, and a to-be-processed surface. The figure which shows the cusp based on the circular arc of a circular arc cutting edge. The figure which shows other embodiment of an end mill. The figure which shows the cusp based on the diameter of an end mill. The perspective view which shows a 5-axis numerical control machine tool. The figure which shows the positional relationship of an end mill and a to-be-processed concave curved surface. The figure which shows that a shank interferes with the edge of a concave surface, if the center horizontal surface part of a concave curved surface is processed with the conventional circular-arc blade end mill.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,21 ... End mill, 11 ... Arc cutting edge, 12 ... Rotation axis, 13 ... Shank, 14 ... Arc, 15 ... Virtual rotating body, 16 ... Rear end, R ... Radius, 17 ... Concave surface to be processed, 18 ... Edge Part, 19, 20 ... cusp, 22 ... 5-axis numerical control machine tool, 23 ... bed, 24 ... column, 25,27,30,32 ... servo motor, 26 ... spindle head, 28 ... spindle, 29 ... table, 31 ... Tilt table, 33 ... Rotation table (work table), 34 ... Numerical control device, O ... Rotation axis, W ... Workpiece.

Claims (3)

A cutting edge portion having a plurality of arc cutting edges inscribed in a virtual rotating body whose arc is rotated around a rotation axis, and a shank protruding rearward from the cutting edge portion coaxially with the rotation axis. In the end mill,
An end mill characterized in that the center of the arc is positioned a predetermined amount on the shank side from the rear end of the arc cutting edge, and the radius of the arc is larger than the maximum radius of the virtual rotating body.   2. The end mill according to claim 1, wherein the cutting edge portion is formed such that an outer diameter of the virtual rotating body at a rear end of the arc cutting edge is larger than an outer diameter of the shank. A spindle head mounted so as to be relatively movable in three orthogonal linear axis directions with respect to a work table holding a workpiece and to be relatively rotatable around at least one rotation axis, and a tip supported by the spindle head so as to be rotatable. A numerically controlled machine tool comprising: a spindle that holds a tool; and a numerical control device that numerically controls the linear movement of the spindle head in the three orthogonal directions and the rotational movement around the rotational axis.
The main shaft is held coaxially with the end mill according to claim 1 or claim 2,
The spindle head is moved numerically with respect to the work table so that the processed concave curved surface processed by the end mill and the virtual rotating body are in contact with the arc cutting edge part,
A machining method using an end mill, characterized in that the workpiece concave curved surface of the workpiece is machined by an arc cutting edge of the end mill.

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