JP4746339B2 - Cutting tool manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a cutting tool in which a cutting edge is made of a hard material such as a cubic boron nitride sintered body.

  Cutting tools that use hard materials such as diamond, cubic boron nitride, cemented carbide, cermet, and ceramic as the cutting edge material provide high machining accuracy with little wear on the cutting edge, so precision machining of high-hardness metal materials, etc. It is suitably used in the field. In the field of precision processing of hard and brittle materials such as glass, ductile cutting using a diamond tool has been studied, and recently, cBN cutting using cubic boron nitride (cBN) as the cutting edge instead of the diamond tool. Ductile cutting with tools has also been studied. Since the cBN cutting tool is less susceptible to oxidation reaction of the cutting edge material, the cutting edge wear is significantly smaller than that of the diamond tool, and is particularly suitable for ultra-precision machining. As an example, it has been confirmed that a lens surface of an optical element such as an optical element lens can be mirror-finished with a cBN cutting tool.

  By the way, as a manufacturing method of a cutting tool using the hard material as described above as a cutting edge material, a cutting edge material is formed so as to fill a cutout in a corner portion of a chip base made of a cemented carbide or the like. A method of forming a cutting blade having a desired shape by polishing the intersecting ridge line portion between the rake face and the flank face of the cutting edge material after joining is generally employed (see, for example, Patent Document 1).

JP 2003-175408 A

  Cutting tools used for free-form surface machining such as lens surface machining need to form the cutting edge into a curved shape, and the shape error of the cutting edge is extremely small especially in ultra-precision machining such as mirror surface machining. It is necessary to form a highly accurate arc shape. In order to form such an arc-shaped cutting blade by the conventional blade attaching method, it is necessary to give a reciprocating motion along the arc between the polishing surface of the grinding wheel and the cutting edge material. Greatly depends on the motion accuracy of the grinding machine. For this reason, high precision is required for the grinding apparatus, and the manufacturing cost of the tool is pressed. In addition, a swing mechanism such as a link mechanism is required to create a reciprocating motion along an arc, and there is a limit to the accuracy that can be obtained with such a mechanism. It is extremely difficult to form a cutting edge. In addition, since sintered materials such as cBN sintered bodies are weak in force in the pulling direction, the cutting edge tends to be damaged by the tensile stress generated during flank polishing in the conventional blade attaching method, and a highly accurate arc-shaped cutting blade is required. It is even more difficult to form.

  The present invention has been made in view of the above-described circumstances, and provides a method for manufacturing a cutting tool capable of easily and accurately forming an arcuate cutting edge with respect to a cutting edge material made of a hard material. The purpose is to provide.

In the manufacturing method of the cutting tool of the present invention, the cutting edge material is processed into a sphere to form an independent sphere (2A), and a part of the sphere is removed to form a cutting edge (4) on the spherical surface of the sphere. Then, the blade member (2A, 2B) in which at least a part of the spherical portion of the sphere is left is joined to the chip base, and after the joining, a part of the spherical portion of the blade member is removed to form a cutting blade, By pressing the spherical portion of the cutting edge member against the polishing surface (20a) while supporting the chip base, the cutting edge is formed by applying a relative movement between the polishing surface and the cutting edge member , as described above. Solve the problem.

According to the manufacturing method of the present invention, a cutting edge along the spherical surface can be formed at the intersection of the removed portion and the spherical surface by forming a sphere of the cutting edge material and removing a part thereof. For this reason, it is not necessary to create a circular reciprocating rocking motion and perform blade attachment. Conventionally, the method of forming a sphere has been used in the production of various true sphere parts such as rolling elements for bearings and jewelry, and a true sphere processing method for producing a high-precision sphere with a simple mechanism has been established. . There is even a true sphere processing method that forms a sphere with a sphericity on the order of nanometers. By utilizing such a technique for making the cutting edge material into a sphere, it is possible to form an arcuate cutting edge more easily and with higher precision than in the conventional method of creating an arc motion and cutting. Moreover, since the compressive force acts exclusively on the cutting edge material when the sphere is formed, the cutting edge material is not easily damaged. As a result, a highly accurate arc-shaped cutting blade with few chips can be easily obtained. Further, the cutting blade can be provided at a desired position with respect to the chip base by adjusting the direction and depth of removal of the spherical portion of the blade member. For this reason, there are few restrictions regarding the alignment of the tip base and the blade edge member when attaching the blade edge member to the chip base, or the alignment is completely unnecessary. In addition, by supporting the chip base, it is possible to support the workpiece more easily and stably than machining the sphere alone to form the cutting blade, thereby forming the cutting blade with high accuracy. Can do. In particular, the effect is significant when the sphere is small.

  When the cutting edge is formed by polishing, the polishing surface may be a flat surface, and the cutting edge and the flat rake face may be formed by relative movement between the blade edge member and the polishing surface. In this embodiment, it is possible to easily form the cutting edge and the rake face using a planar polishing surface. By causing the polishing surface to move relative to the cutting edge member from the cutting edge to the cutting edge side, it is possible to suppress the generation of tensile stress in the cutting edge portion, thereby further reliably preventing the cutting edge from being damaged.

  Alternatively, the polishing surface may be spherical, and the cutting edge and the spherical rake surface complementary to the polishing surface may be formed on the cutting edge member by relative movement between the cutting edge member and the polishing surface. . In this embodiment, the edge angle formed by the rake face and the flank face can be changed according to the curvature of the polished surface.

  In the present invention, the spherical body is formed of a sintered body, and when the cutting blade is formed, a force (F) for removing the cutting edge material may be applied from the cutting edge toward the cutting edge side. . By applying a force in this way, it is possible to suppress the generation of tensile stress in the cutting edge portion, and thereby more reliably prevent the cutting edge from being lost. In particular, when the sphere is composed of a cubic boron nitride sintered body, the effect is remarkable.

  In addition, in the above description, in order to make an understanding of this invention easy, the reference sign of the accompanying drawing was attached in parenthesis, but this invention is not limited to the form of illustration by it.

  As described above, according to the method for manufacturing a cutting tool of the present invention, the cutting edge material is processed into a sphere to form a sphere, and a part of the sphere is removed to obtain a cutting blade. Therefore, it is no longer necessary to create a reciprocating oscillating motion, and an arcuate cutting edge can be formed easily and with higher accuracy than the conventional method. Moreover, since the compressive force exclusively acts on the cutting edge material when the sphere is formed, the cutting edge material is not easily damaged, and a highly accurate arc-shaped cutting edge with few chips can be easily obtained.

  With reference to FIGS. 1-12, the form which applied this invention to manufacture of the throwaway tip for lathes is demonstrated. FIG. 1 is a plan view of a chip base 1 used for manufacturing a throw-away chip, and FIG. 2 is a side view thereof. The tip base 1 is formed in a polygonal flat plate shape, and a concave portion 1a for attaching a cutting edge member is formed at the tip thereof. Further, the tip base 1 is appropriately provided with mounting holes 1b for fixing the tip base 1 to a tool body (not shown). However, the method of fixing the chip base 1 to the tool main body is not limited to bolt fastening, but may be joining using brazing or mechanical clamping using a clamp piece or the like. The material of the chip base 1 can be a metal such as a cemented carbide, ceramics, or the like, as in a general throw-away chip. The recess 1a is formed so as to constitute a part of a spherical surface. Such a recess 1a can be formed using, for example, a ball end mill.

  As shown in FIGS. 3 and 5, a sphere 2 </ b> A formed by processing a blade tip material into a sphere is joined to the recess 1 a of the chip base 1 as a blade tip member. As the cutting edge material, a hard material such as diamond, cubic boron nitride, cemented carbide, cermet, or ceramics may be appropriately selected. As a joining method, various joining methods such as high-frequency brazing used in conventional diamond tools, cBN tools, and the like may be used. A method of manufacturing the sphere 2A will be described later. Next, as shown in FIGS. 4 and 6, the upper portion of the sphere 2 </ b> A is removed to form the rake face 3 on the blade tip member 2, and the cutting edge 4 is given to the intersecting ridge line between the rake face 3 and the spherical surface. The cutting edge 4 formed in this way exists on the spherical surface, and is curved in an arc shape according to the radius of curvature of the sphere 2A. Accordingly, it is not necessary to adjust the shape of the cutting edge 4 to an arc shape by pressing a grindstone or the like on the cutting edge member 2 after the rake face 3 is formed. In addition, a part of the spherical surface continuous below the cutting edge 4 can be used as the flank 5 as it is. A method of removing the sphere 2A will be described later. What is necessary is just to set the depth which removes the spherical body 2A according to the edge angle given as an intersection angle of the rake face 3 and the flank 5.

  In FIG. 6, the rake face 3 is provided parallel to the upper and lower surfaces of the chip base 1. However, as shown in FIG. 7, the rake face 3 is formed so as to be lowered toward the cutting edge 4, or as shown in FIG. Thus, the rake face 3 can be formed to rise upward toward the cutting edge 4 to change the inclination of the rake face 3 with respect to the chip base 1. By changing the inclination of the rake face 3 in this way, it is possible to adjust the tool rake angle and the relief angle when the workpiece is cut by the throw-away tip.

  As shown in FIGS. 9 and 10, the cutting edge angle is θ, the removal depth of the sphere 2A is Δt, the radius of the sphere 2A is r, and the center of the sphere 2A and the cutting edge (referred to as the apex of the cutting edge 4). If the angle formed by the connected straight line and the rake face is α, these relationships are as follows. 9 shows the case where the removal depth Δt of the sphere 2A is set to be equal to or less than the radius r, and FIG. 10 shows the case where the removal depth Δt of the sphere 2A is set larger than the radius r.

When θ ≧ π / 2, θ = (π / 2) + α as shown in FIG.
α = θ− (π / 2) (1)
Further, from FIG. 9, equation (2) is established.
sin α = (r−Δt) / r (2)
From these equations (1) and (2), Δt = r (1-sin α) = r (1-sin (θ− (π / 2))) (3)

When θ <π / 2, θ = (π / 2) −α as shown in FIG.
α = (π / 2) −θ (4)
Further, from FIG. 10, equation (5) is established.
sin α = (Δt−r) / r (5)
From these equations (4) and (5), Δt = r (1 + sin α) = r (1 + sin ((π / 2) −θ)) (6)

  When the rake face 3 and the cutting edge 4 are formed, the removal depth Δt may be determined by the above formula (3) or (4) according to the target cutting edge angle θ. As described above, the inclination angle α may be set as appropriate according to the tool rake angle or clearance angle required when cutting the workpiece with the throw-away tip.

  FIG. 11 shows an example of a method for processing a sphere 2A into a true sphere. In this example, the pair of grinding wheels 10A and 10B are arranged coaxially such that a gap 11 equal to the diameter of the sphere 2A is generated between them. The grinding wheels 10A and 10B are rotationally driven at different speeds in the same direction around their axes by a rotation mechanism (not shown). The rotational axes of the grinding wheels 10A and 10B are set in the horizontal direction, but may be other than the vertical direction. An introduction hole 12 leading to the gap 11 is provided at the center of one grinding wheel 10A. Through the introduction hole 12, a rough sphere 13 serving as a prototype of the sphere 2 </ b> A is guided to the gap 11 by the guide 14. The rough sphere 13 can be formed into a spherical shape by, for example, sintering the blade edge material that is the material of the sphere 2A. The sphericity is sufficiently lower than the shape accuracy required for the cutting blade 4. The diameter of the coarse sphere 13 is set to be larger than the sphere 2A by the grinding allowance. The rough sphere 13 guided to the gap 11 is gradually moved toward the outer periphery of the grinding wheels 10A and 10B by the centrifugal force and gravity while being polished by the grinding wheels 10A and 10B, and finally falls from the gap 11 To do. Thereby, the sphere 2A can be manufactured. According to such a manufacturing method, a compressive force mainly acts on the coarse sphere 13, so that even when the coarse sphere 13 is formed with a cutting edge material that is weak against a force in the pulling direction such as a cBN sintered body, a defect is not generated. The sphere 2A that hardly occurs and has a high sphericity can be efficiently manufactured.

  In addition, said manufacturing method is an example to the last, and 2A of spheres may be manufactured by various sphere processing methods. For example, a true sphere processing method using a lapping machine, a spherical cutting method using a jig boring machine, or the like can be used for manufacturing the sphere 2A.

  FIG. 12 shows an example of a method for partially removing the sphere 2 </ b> A bonded to the chip base 1. In this example, the spherical body 2 </ b> A is polished by using a horizontally disposed disk-shaped polishing plate (skyf) 20 and a feeding mechanism 21 above the polishing plate 20. The polishing surface 20a of the polishing plate 20 is flat, and an appropriate abrasive is applied to the polishing surface 20a. As an abrasive | polishing agent, what dissolved abrasives, such as a diamond powder, in solvents, such as oil, can be used, for example. The feed mechanism 21 includes a support portion 21a and a movable portion 21b. The movable portion 21b is displaced in the vertical direction with respect to the support portion 21a by, for example, an operation of the feed handle 21c. The chip base 1 is attached to the movable part 21b of the feed mechanism 21 in a state where it is turned upside down. The sphere 2A is pressed against the polishing surface 20a by the feed mechanism 21, and in this state, the polishing plate 20 is rotationally driven in a predetermined direction (indicated by an arrow in the figure), whereby the sphere 2A is gradually polished and the rake surface 3 is pressed. And the cutting edge 4 is formed. The rotational direction of the polishing plate 20 may be determined as appropriate, but when a sintered body is used as the blade tip material, the polishing surface 20a should be set to move relative to the sphere 2A from the blade tip to the blade base side. Is desirable. That is, as indicated by an arrow F in FIG. 3, the rotation direction of the polishing plate 20 may be set so that the force for removing the sphere 2 </ b> A acts from the blade edge toward the blade base side. By determining the rotation direction in this way, it is possible to prevent the cutting blade 4 from being broken by suppressing the generation of tensile stress in the cutting edge portion.

  In addition, said removal method is an example to the last, and an appropriate method can be used for removal of the spherical body 2A. For example, the rake face 3 and the cutting edge 4 may be formed by cutting the sphere 2A using a laser or a wire saw. When cutting the sintered sphere 2A using these methods, the cutting direction may be set so that the cutting force acts from the blade edge to the blade base side.

  The present invention is not limited to the above form and can be implemented in various forms. For example, in the above embodiment, the sphere 2A is joined to the chip base 1 without any processing. However, as shown in FIG. 13, a removal surface 2a is formed in advance on the joining portion of the sphere 2A to the chip base 1, The cutting edge member 2B may be bonded to the chip base 1, and after bonding, the spherical portion of the cutting edge member 2B may be removed to form the rake face 3 or the like. That is, as long as the spherical portion of the blade member remains at the tip of the tip base 1 with the blade member joined to the chip base 1, the rake face and the cutting edge can be formed in the same manner as in the above procedure. . In addition, according to the example of FIG. 13, there exists an advantage which can suppress the depth of the recessed part 1a. When the cutting edge member 2B from which the sphere 2A has been partially removed is joined to the chip base 1, the cutting edge member 2B is removed by removing appropriate portions of the sphere 2A as long as the formation of the rake face 3 and the cutting edge 4 is not hindered. It may be formed. For example, not only the lower surface side but also the back surface side, the oblique upper surface side and the like can be removed in advance.

  When the removal surface 2 a is formed by cutting the sphere 2 </ b> A, the removed blade edge material can be used as a blade edge member to be joined to another chip base 1. Further, the spherical body 2A can be divided into two or more pieces, and each of the obtained divided pieces can be attached to the chip base 1 as a cutting edge member. In this case, the cutting edge member by the split piece may be further processed to form a rake face and a cutting edge. However, the split face generated on the split piece is used as the rake face, and the intersecting ridge line between the split face and the spherical surface is cut. It may be used as a blade, respectively, and the processing of the cutting blade after joining to the chip base 1 may be omitted. That is, the cutting blade can be formed in advance before joining to the chip base 1. In this case, the rake face may be further processed after joining. In addition, when forming a rake face and a cutting edge before joining, it is necessary to adjust the joining position and direction of the blade edge member 2 with respect to the chip base 1, whereas when forming the cutting edge 4 after joining. Since the position and orientation of the cutting edge 4 can be appropriately set at the time of formation, the cutting edge member can be more easily joined to the chip base 1. In any case, as long as the cutting edge member is derived from a sphere, an arcuate cutting blade can be formed with high accuracy and easily according to the present invention.

  The rake face is not necessarily limited to a flat one, and the shape of the rake face can be appropriately changed as long as the arcuate cutting edge 4 is obtained. For example, as shown in FIG. 14, the stepped portion 3a can be made to function as a chip breaker or the like by forming a stepped rake face protruding rearward as compared to the blade edge side. In addition, appropriate structures such as grooves and dimples may be formed on the rake face.

  Furthermore, as shown in FIG. 15 or FIG. 16, the rake face 3 may be curved into a spherical shape. FIG. 15 shows an example in which the polishing surface 20a is formed in a concave spherical shape and pressed against the cutting edge member to polish the cutting edge member 2, thereby forming a spherical rake face 3 that swells complementarily with the polishing surface 20a. is there. On the other hand, in FIG. 16, the polishing surface 20a is formed into a convex spherical shape, and this is pressed against the blade edge member to polish the blade edge member 2, thereby forming a spherical rake face 3 that is recessed in a complementary manner to the polishing surface 20a. It is an example. According to these examples, the cutting edge angle of the cutting edge member 2 can be appropriately changed according to the curvature of the polishing surface 20a. Polishing may be performed by offsetting the apex of the polishing surface 20a with respect to the central axis of the sphere 2A. Further, in the example of FIG. 16, the polishing surface 20a may be formed as a complete spherical surface. In other words, the grindstone itself may be formed into a sphere. By rotating such a polishing surface 20a in a fixed direction from the cutting edge toward the cutting edge, a force for removing the sphere 2A is always applied from the cutting edge toward the cutting edge as in the processing method of FIG. Can do.

  The present invention is not limited to the method for manufacturing a throw-away tip, but can be applied to various cutting tools manufactured by joining a cutting edge member made of a hard cutting edge material to a chip base. Moreover, this invention is not limited to the manufacturing method of the cutting tool for lathes, It can apply to manufacture of various cutting tools, such as a milling machine and an end mill.

The top view of the chip base used for manufacture of a throw away chip. The side view of a chip base. The perspective view which shows the state which joined the spherical body to the chip base as a blade member. The perspective view which shows the state which processed the spherical body and formed the cutting blade. Sectional drawing which shows the state which joined the spherical body to the chip base as a blade edge member. Sectional drawing which shows the state which processed the spherical body and formed the cutting blade. Sectional drawing which shows the example which formed the rake face in front-down. Sectional drawing which shows the example which formed the rake face in the front rising. The figure which shows the relationship between the blade edge angle | corner at the time of restrict | limiting the removal depth of a sphere below to the radius of a sphere, a removal depth, a sphere radius, and the inclination angle of a rake face. The figure which shows the relationship between the blade edge angle | corner, removal depth, a spherical body radius, and the inclination angle of a rake face at the time of setting the removal depth of a spherical body larger than the radius of a spherical body. The perspective view which shows an example of the manufacturing method of a spherical body. The perspective view which shows an example of the method of removing a spherical body and forming a rake face and a cutting blade. Sectional drawing which shows the state which joined the blade edge | tip member which removed a part of spherical body to the chip base. Sectional drawing which shows the example which formed the rake face as a stepped surface. Sectional drawing which shows the example which formed the rake face in the convex spherical shape. Sectional drawing which shows the example which formed the rake face in the concave spherical shape.

Explanation of symbols

1 Chip base 2 Cutting edge member 2A Sphere (cutting edge member)
2B cutting edge member 3 rake face 4 cutting edge 5 flank 10A, 10B grinding wheel 11 gap 12 introduction hole 13 rough sphere 14 guide 20 polishing plate 20a polishing surface 21 feed mechanism

Claims (5)

Forming an independent sphere by processing the cutting edge material into a true sphere, removing a part of the sphere to form a cutting edge on the spherical surface of the sphere ,
Joining the cutting edge member in which at least a part of the spherical portion of the sphere is left to the chip base, forming a cutting blade by removing a part of the spherical portion of the cutting edge member after joining,
A cutting tool characterized in that the cutting edge is formed by pressing a spherical portion of the cutting edge member against a polishing surface while supporting the chip base, and applying a relative motion between the polishing surface and the cutting edge member . Production method. 2. The method of manufacturing a cutting tool according to claim 1 , wherein the polishing surface is a flat surface, and the cutting blade and a flat rake surface are formed by relative movement between the blade member and the polishing surface. The polishing surface is spherical, and a spherical rake surface complementary to the cutting blade and the polishing surface is formed on the cutting edge member by relative movement between the cutting edge member and the polishing surface. The manufacturing method of the cutting tool of Claim 1 . With forming the spherical body by the sintered body, when forming the cutting edge of claims 1-3, characterized in that the action towards the blade root side force for removing the cutting edge material from the cutting edge The manufacturing method of the cutting tool as described in any one. The method for manufacturing a cutting tool according to claim 4 , wherein the sphere is formed of a cubic boron nitride sintered body.

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