End mill and method for manufacturing the same

Abstract

To provide an end mill with excellent strength and durability in which a cutting blade is properly attached to a main body although a diameter thereof is small, and a simple manufacturing method for the same.SOLUTION: The end mill according to the invention comprises a main body, provided with embedding parts, which rotates with a rotary shaft as a center and cutting blades, embedded into the embedding parts, which are configured as outermost diameters. In the end mill, the cutting blades include sintered diamond, torsion angles of the cutting blades are 0° and outer diameters thereof are less than 10 mm. The manufacturing method for an end mill includes steps of: embedding the cutting blades into the embedding parts of the main body; and fastening the cutting blades into the embedding parts by vacuum brazing or high-frequency brazing with the cutting blades embedded into the embedding parts.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an end mill and a method for manufacturing the same.

Background Art

[0002] An end mill is widely known as one of cutting tools. Typically, an end mill has a main body that rotates about a rotation axis and cutting edges attached to the surface of the main body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There are many tool materials for end mills, and the inventors of the present invention have considered using a sintered diamond blade as a countermeasure against wear of the cutting edge. A normal end mill is formed by cutting a single piece of metal to form the blade, but it is difficult to cut a sintered diamond blade to form the blade, and it is necessary to separately attach it to the main body of the end mill. Depending on the application, an end mill may be required to have a small diameter (for example, an outer diameter of less than 10 mm). For such a small-diameter end mill, it is often difficult to sufficiently secure an attachment surface for attaching the cutting edge to the main body, and it is often difficult to attach the cutting edge to the main body.

[0005] The present invention has been made to solve the above conventional problems, and its main object is to provide an end mill that has a small diameter but has a cutting edge well attached to the main body and is excellent in strength and durability, and a simple manufacturing method therefor.

Means for Solving the Problems

[0006] The end mill of the present invention has a main body that rotates about a rotation axis and is provided with an embedding portion, and a cutting edge configured as an outermost diameter that is embedded and fixed in the embedding portion. This end mill has a cutting edge that includes sintered diamond, a twist angle of the cutting edge of 0°, and an outer diameter of less than 10 mm. In one embodiment, the cutting edge has a base portion made of a cemented carbide material and a sintered diamond layer provided on one surface of the base portion. In one embodiment, the depth of the embedding portion is 0.30 mm to 1.50 mm. In one embodiment, the cutting edge is an integral body without joints, and the length thereof in the rotation axis direction is 15 mm or more. In one embodiment, in the main body, the upstream side in the rotation direction of the embedding portion as viewed from the rotation axis direction protrudes more than the downstream side in the rotation direction of the embedding portion. In one embodiment, the depth of the upstream side in the rotation direction of the embedding portion is 0.50 mm to 1.50 mm, and the depth of the downstream side in the rotation direction is 0.30 mm to 1.25 mm. In one embodiment, a plurality of the embedding portions are provided in the main body, and a plurality of the cutting edges are provided corresponding to the number of the embedding portions. According to another aspect of the present invention, a manufacturing method of the end mill may be provided. This manufacturing method includes embedding the cutting edge in the embedding portion of the main body, and fixing the cutting edge to the embedding portion by vacuum brazing or high-frequency brazing in a state where the cutting edge is embedded in the embedding portion. In one embodiment, the cutting edge has a base portion made of a cemented carbide material and a sintered diamond layer provided on one surface of the base portion, and the manufacturing method fixes both the base portion and the sintered diamond layer to the embedding portion by vacuum brazing. In another embodiment, the cutting edge is made of sintered diamond, and the manufacturing method fixes the sintered diamond to the embedding portion by vacuum brazing.

Advantages of the Invention

[0007] According to the present invention, in a small-diameter end mill, by providing an embedding portion in the main body and embedding and fixing a cutting edge in the embedding portion, the cutting edge is well attached to the main body, and an end mill excellent in strength and durability can be realized.

Brief Description of Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0009] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. Note that the drawings are schematically shown for easy viewing, and further, the ratios such as length, width, and thickness, as well as angles, etc. in the drawings are different from the actual ones.

[0010] A. End Mill Fig. 1(a) is a schematic plan view seen from the axial direction for explaining the structure of an end mill according to one embodiment of the present invention; Fig. 1(b) is a schematic perspective view of the end mill of Fig. 1(a). The end mill 100 in the illustrated example has a main body 20 that rotates about a rotation axis 22 extending in the vertical direction (the stacking direction of the workpiece, and the workpiece is a cutting object on which an optical film is stacked, and details will be described later), and a cutting edge 10 that protrudes from the main body 20 and is configured as the outermost diameter. The end mill is typically a straight end mill. In the embodiment of the present invention, an embedding portion 24 is provided in the main body 20, and the cutting edge 10 is embedded in the embedding portion 24 and fixed to the main body 20. With such a configuration, even if the end mill has a small diameter and it is difficult to sufficiently secure a mounting surface for the cutting edge on the main body surface, the cutting edge can be well mounted on the main body. Therefore, a small-diameter end mill having a practically acceptable cutting ability can be actually manufactured. Furthermore, an end mill excellent in strength and durability can be realized.

[0011] The number of the cutting edges 10 can be set corresponding to the number of the embedding portions 24. In the illustrated example, the embedding portions 24, 24 are provided at two locations, but the embedding portion may be provided at one location, may be provided at three locations, or may be provided at four or more locations. The embedding portion is preferably provided at one to three locations. That is, the number of the cutting edges of the end mill is preferably one to three. With such a configuration, an appropriate interval between the cutting edges is ensured, so that the cutting chips can be well discharged. More preferably, the number of the cutting edges is two. With such a configuration, the rigidity of the cutting edge is ensured, and a pocket is ensured to well discharge the cutting chips. When a plurality of embedding portions are provided, the embedding portions are preferably provided at positions symmetric with respect to the rotation axis 22. With such a configuration, good cutting can be realized, and the strength and durability of the end mill can be further improved.

[0012] In the illustrated example, the depth d of the embedding portion 24 is preferably 0.30 mm to 1.50 mm, more preferably 0.30 mm to 1.00 mm, and even more preferably 0.30 mm to 0.70 mm. If the depth of the embedding portion is within such a range, both the fixing strength of the cutting edge to the main body and the strength of the main body itself can be ensured. When the depth of the embedding portion is less than 0.30 mm, the fixing strength of the cutting edge to the main body may be insufficient. When the depth of the embedding portion exceeds 1.50 mm, the strength of the main body itself may be insufficient.

[0013] In an embodiment of the present invention, the twist angle of the cutting edge 10 is 0°. With such a configuration, the cutting of the optical film described later can be performed favorably. More specifically, when cutting (for example, profiling or non-linear machining) using a cutting edge having a twist angle, the cutting surface may be tapered when viewed from the lateral direction. By using a cutting edge with a twist angle of 0°, it is possible to suppress the cutting surface from becoming tapered. Here, profiling means, for example, processing an optical film into a shape other than a rectangle. In particular, a remarkable effect can be obtained when performing fine non-linear machining (profiling) on an optical film using an end mill with a small diameter. In this specification, "the twist angle is 0°" means that the cutting edge 10 extends in a direction substantially parallel to the rotation axis 22. In other words, the blade is not twisted with respect to the rotation axis. Note that "0°" means substantially 0°, and also includes cases where there is a slight angular twist due to machining errors or the like.

[0014] In an embodiment of the present invention, the outer diameter of the end mill is less than 10 mm, preferably 3 mm to 9 mm, and more preferably 4 mm to 7 mm. According to the embodiment of the present invention, an end mill having such a small outer diameter and having a practically acceptable cutting ability can be actually manufactured. As a result, for example, in fine non-linear machining (contouring) using such a small-diameter end mill, cracks and yellow bands in the optical film can be well suppressed. Further, when the optical film has an adhesive layer, glue shortage can be well suppressed. In the present specification, the "outer diameter of the end mill" means twice the distance from the rotation axis 22 to the cutting edge 10a.

[0015] The cutting edge 10 typically includes a cutting edge 10a, a rake face 10b, and a relief face 10c. A pocket 30 may be defined by the rake face 10b and the body 20. The cutting edge 10a may be flat or sharp as shown in the illustrated example (for example, it may have an acute vertex in plan view). The shape of the relief face 10c in plan view may be linear, bent (it may have two relief faces), or a smooth curve as shown in the illustrated example. The relief face 10c is preferably roughened. As the roughening treatment, any appropriate treatment can be adopted. A typical example is blasting. By roughening the relief face, when cutting an optical film and the optical film includes an adhesive layer (for example, an adhesive layer, a pressure-sensitive adhesive layer), the adhesion of the adhesive or pressure-sensitive adhesive to the cutting edge is suppressed. As a result, blocking can be suppressed. In the present specification, "blocking" refers to a phenomenon in which optical films in a workpiece adhere to each other with an adhesive or pressure-sensitive adhesive on the end face when the optical film includes an adhesive layer, and the chips of the adhesive or pressure-sensitive adhesive adhering to the end face contribute to the adhesion of the optical films to each other.

[0016] In an embodiment of the present invention, the cutting edge 10 includes sintered diamond. With such a configuration, fine non-linear machining (contouring machining) using the above-mentioned end mill with a small diameter can be performed well. More specifically, the cutting edge 10 may be composed of sintered diamond (substantially, may be made of sintered diamond), or may be configured to include sintered diamond as shown in the illustrated example. In the illustrated example, the cutting edge 10 has a base portion 11 and a sintered diamond layer 12 provided on one surface of the base portion 11 (the surface on the downstream side in the rotation direction R of the end mill). The surface of the sintered diamond layer 12 becomes the rake face 10b of the cutting edge. With the configuration of the illustrated example, machining and cutting out of the cutting edge are easy. Further, in the illustrated example, the effect by providing the embedding portion becomes remarkable. Details are as follows. When attaching a cutting edge having such a laminated structure to the main body, the attachment is typically performed by brazing. However, due to the laminated structure, the thermal shrinkage properties are different between the base portion side and the sintered diamond layer side. As a result, warping often occurs in the cutting edge during attachment by brazing, making it difficult to attach the cutting edge to the main body. According to the embodiment of the present invention, since the cutting edge is fixed in a state of being embedded in the embedding portion of the main body, attachment is possible even when warping occurs in the cutting edge.

[0017] In the illustrated example, the thickness of the base portion 11 can be, for example, 0.2 mm to 2.0 mm, and also, for example, 0.2 mm to 1.3 mm. Representative examples of the cemented carbide material constituting the base portion 11 include cemented carbides. A cemented carbide typically refers to a composite material obtained by sintering carbides of metals in Groups IVa, Va, and VIa of the periodic table with iron-based metals such as Fe, Co, and Ni. Specific examples of the cemented carbide include WC-Co alloys, WC-TiC-Co alloys, WC-TaC-Co alloys, WC-TiC-TaC-Co alloys, WC-Ni alloys, and WC-Ni-Cr alloys. The thickness of the sintered diamond layer 12 can be, for example, 0.5 mm to 1.5 mm. The sintered diamond constituting the sintered diamond layer 12 is typically a polycrystalline diamond obtained by sintering small diamond grains together with a binder (for example, metal powder, ceramic powder) at high temperature and high pressure. In the present embodiment, the thickness of the base portion 11 is greater than the thickness of the sintered diamond layer 12. By changing the type and blending ratio of the binder, etc., the properties of the sintered diamond can be adjusted.

[0018] The cutting edge 10 is preferably an integral body without joints along the length direction (rotation axis direction) of the main body 20. By the cutting edge being an integral body without joints, the cutting ability, strength, and durability can be further improved. The length of the cutting edge in the rotation axis direction is preferably 15 mm or more, more preferably 20 mm or more. Also, the length of the cutting edge in the rotation axis direction is, for example, 120 mm or less, preferably 100 mm or less, more preferably 50 mm or less. With such a length, when cutting an optical film, a workpiece with a desired number of laminated optical films can be cut, so that the efficiency of the cutting process can be improved.

[0019] FIG. 2 is a schematic plan view seen from the axial direction for explaining the structure of an end mill according to another embodiment of the present invention. According to the present embodiment, in the main body 20, the upstream portion 20u in the rotational direction R of the embedded portion 24 seen from the rotational axis direction projects more than the downstream portion 20d. With such a configuration, the cutting chips can be discharged more favorably. The depth d1 on the upstream side in the rotational direction of the embedded portion is preferably 0.50 mm to 1.50 mm, more preferably 0.50 mm to 1.00 mm. The depth d2 on the downstream side in the rotational direction of the embedded portion is preferably 0.30 mm to 1.25 mm, more preferably 0.30 mm to 0.75 mm. If d1 and d2 are within such ranges, both the fixing strength of the cutting edge to the main body and the strength of the main body itself can be ensured while realizing the above-described excellent cutting chip discharge property. The ratio d1 / d2 of d1 to d2 is preferably 1.20 to 1.67, more preferably 1.33 to 1.67. If the ratio d1 / d2 is within such a range, there is an advantage that the structure is more resistant to the cutting conditions for processing the loaded optical film.

[0020] B. Method for manufacturing an end mill The method for manufacturing an end mill according to an embodiment of the present invention includes embedding the cutting edge 10 in the embedded portion 24 of the main body 20; and fixing the cutting edge 10 to the embedded portion 24 by vacuum brazing or high-frequency brazing with the cutting edge 10 embedded in the embedded portion 24. This will be briefly described below.

[0021] First, a main body is fabricated. The main body can be fabricated, for example, by processing a sintered body obtained by a powder metallurgy method well-known in the art into a cylindrical shape by a method well-known in the art. Next, an embedding portion is formed in the main body. The embedding portion can be formed by any suitable method. Specific examples of the forming method include laser processing and cutting. On the other hand, a cutting edge is fabricated. When the cutting edge has a base portion made of a cemented carbide material and a sintered diamond layer provided on one surface of the base portion, the cutting edge can be fabricated by the following procedure: First, a cutting edge forming piece having a predetermined shape is cut out from a base material having a base portion and a sintered diamond layer. The cutting out is performed, for example, by electrical discharge machining or laser processing. Next, the base portion of the obtained cutting edge forming piece is cut to reduce the thickness to a predetermined thickness, whereby a cutting edge can be obtained. When the cutting edge is made of sintered diamond, the cutting edge can be obtained by cutting a base material of sintered diamond.

[0022] Next, the cutting edge obtained as described above is embedded in the embedding portion formed as described above (typically, the cutting edge is inserted into the embedding portion). Finally, with the cutting edge embedded in the embedding portion, the cutting edge is fixed to the embedding portion. Specifically, the cutting edge can be fixed to the embedding portion by vacuum brazing or high-frequency brazing. Vacuum brazing can satisfactorily fix a cutting edge including sintered diamond to the main body (embedding portion). This is because residual oxygen and moisture during brazing can be removed, thus destroying the oxide film on the main body surface and preventing regeneration of the oxide film, and therefore increasing the wettability of the main body surface. When the cutting edge has a base portion and a sintered diamond layer, both the base portion and the sintered diamond layer are fixed to the main body (embedding portion) by vacuum brazing or high-frequency brazing; when the cutting edge is made of sintered diamond, the sintered diamond is fixed to the main body (embedding portion) by vacuum brazing.

[0023] C. Method of Using an End Mill The end mills described in Items A and B above can typically be suitably used in a method for manufacturing an optical film. The manufacturing method preferably includes cutting the end face of the optical film.

[0024] Specific examples of the optical film include a polarizer, a retardation film, a polarizing plate (typically, a laminate of a polarizer and a protective film), a conductive film for a touch panel, a surface treatment film, and a laminate (for example, a circularly polarizing plate for antireflection, a polarizing plate with a conductive layer for a touch panel) obtained by appropriately laminating these according to the purpose. In one embodiment, the optical film includes an adhesive layer (for example, an adhesive layer, a pressure-sensitive adhesive layer). By using the end mill according to the embodiment of the present invention, even an optical film including an adhesive layer can suppress glue shortage in cutting.

[0025] Hereinafter, a manufacturing method in the case of adopting a polarizing plate with an adhesive layer as an example of the optical film will be described. Specifically, each step in the manufacturing method of a polarizing plate with an adhesive layer having a planar shape as shown in FIG. 3 will be described. It is obvious to those skilled in the art that the optical film is not limited to a polarizing plate with an adhesive layer, and the planar shape of the polarizing plate with an adhesive layer is not limited to the planar shape of FIG. 3. That is, the end mill according to the embodiment of the present invention can be applied to a manufacturing method of an arbitrary optical film having an arbitrary shape.

[0026] C-1. Formation of the workpiece FIG. 4 is a schematic perspective view for explaining the cutting process of an optical film, and a workpiece 200 is shown in this figure. As shown in FIG. 4, a workpiece 200 is formed by stacking a plurality of optical films (polarizing plates with an adhesive layer). Since the polarizing plate with an adhesive layer can be manufactured by methods well-known and commonly used in the industry, a detailed description of the manufacturing method is omitted. The polarizing plate with an adhesive layer is typically cut into any appropriate shape when forming the workpiece. Specifically, the polarizing plate with an adhesive layer may be cut into a rectangular shape, a shape similar to a rectangular shape, or an appropriate shape according to the purpose (for example, a circular shape). Further, the polarizing plate with an adhesive layer may be cut so that an opening is provided in the polarizing plate with an adhesive layer. In the illustrated example, the polarizing plate with an adhesive layer is cut into a rectangular shape, and the workpiece 200 has outer peripheral surfaces (cutting surfaces) 200a, 200b facing each other and outer peripheral surfaces (cutting surfaces) 200c, 200d orthogonal to them. The workpiece 200 is preferably clamped from above and below by clamping means (not shown). The total thickness of the workpiece is preferably 10 mm to 50 mm, more preferably 15 mm to 25 mm, and even more preferably about 20 mm. With such a thickness, damage due to pressing by the clamping means or impact during cutting can be prevented. The polarizing plates with an adhesive layer are stacked so that the workpiece has such a total thickness. The number of polarizing plates with an adhesive layer constituting the workpiece can be, for example, 20 to 100. The clamping means (for example, a jig) may be made of a soft material or a hard material. When made of a soft material, its hardness (JIS A) is preferably 60° to 80°. If the hardness is too high, pressing marks may remain due to the clamping means. If the hardness is too low, displacement may occur due to deformation of the jig, resulting in insufficient cutting accuracy.

[0027] C-2. End milling Next, a predetermined position on the outer peripheral surface of the workpiece 200 is cut by the end mill 100. The end mill 100 is typically held by a machine tool (not shown), rotated at high speed around the rotation axis of the end mill, and used by bringing the cutting edge into contact with the outer peripheral surface of the workpiece 200 and making a cut while being fed in a direction intersecting the rotation axis. That is, the cutting is typically performed by bringing the cutting edge of the end mill into contact with the outer peripheral surface of the workpiece 200 and making a cut. When manufacturing a polarizing plate with an adhesive layer having a planar shape as shown in FIG. 3, chamfered portions 200E, 200F, 200G, and 200H are formed at four corners on the outer periphery of the workpiece 200, and a recess 200I is formed at the center of the outer peripheral surface connecting the chamfered portions 200E and 200H. When the polarizing plate with an adhesive layer is cut so that an opening is provided in the polarizing plate with an adhesive layer, the periphery of the opening may be cut by an end mill.

[0028] The cutting process of the workpiece 200 will be described in detail. First, as shown in FIG. 5(a), the portion where the chamfered portion 200E in FIG. 2 is formed is chamfered. Next, as shown in FIGS. 5(b) to 5(d), the portions where the chamfered portions 200F, 200G, and 200H are formed are sequentially chamfered. Finally, as shown in FIG. 5(e), the recess 200I is cut and formed. In the illustrated example, the chamfered portions 200E, 200F, 200G, and 200H, and the recess 200I are formed in this order, but they may be formed in any appropriate order.

[0029] The cutting conditions can be appropriately set according to the configuration of the polarizing plate with an adhesive layer, the desired shape, etc. For example, the rotational speed (number of revolutions) of the end mill is preferably less than 25,000 rpm, more preferably 22,000 rpm or less, and even more preferably 20,000 rpm or less. The lower limit of the rotational speed of the end mill can be, for example, 10,000 rpm. Also, for example, the feed rate of the end mill is preferably 500 mm / min to 10,000 mm / min, more preferably 500 mm / min to 2,500 mm / min, and even more preferably 800 mm / min to 1,500 mm / min. Also, for example, the depth of cut of the end mill is preferably 0.8 mm or less, more preferably 0.3 mm or less. The number of cutting passes at the cutting location by the end mill can be one pass, two passes, three passes or more.

[0030] As described above, a polarizing plate with an adhesive layer that has been cut using the end mill according to an embodiment of the present invention can be obtained. In the illustrated example, a polarizing plate with an adhesive layer including a non-linearly processed portion can be obtained.

Industrial Applicability

[0031] The end mill of the present invention can be suitably used for cutting optical films. The optical film cut using the end mill of the present invention can be used, for example, in a deformed image display portion typified by an instrument panel of an automobile or a smart watch.

Explanation of Reference Numerals

[0032] 10 Cutting edge 10a Cutting tip 10b Rake face 10c Relief face 11 Base 12 Sintered diamond layer 20 Body 22 Rotation axis 24 Embedded portion 30 Pocket 100 End mill 101 End mill 200 Workpiece

Claims

**Claim 1**: A main body that rotates about a rotation axis, the main body being provided with an embedding portion configured as a groove portion extending radially from the outer periphery toward the rotation axis; a cutting blade that is embedded and fixed in the embedding portion and protrudes radially from the main body to form an outermost diameter. Two embedding portions are provided at positions symmetric with respect to the rotation axis of the main body, and the cutting blade has two cutting blades corresponding to the number of the embedding portions. The cutting blade has a base portion made of a cemented carbide material and a sintered diamond layer provided on one surface of the base portion, the thickness of the sintered diamond layer being 0.5 mm to 1.5 mm, and the thickness of the base portion being larger than the thickness of the sintered diamond layer. The twist angle of the cutting blade is 0°. The outer diameter is less than 10 mm. An end mill for processing an adhesive layer-containing optical film. **Claim 2** The end mill for processing an adhesive layer-containing optical film according to claim 1, wherein the depth of the embedding portion is 0.30 mm to 1.50 mm. **Claim 3** The end mill for processing an adhesive layer-containing optical film according to claim 1 or 2, wherein the cutting blade is an integral body without joints along the length direction of the main body, and the length thereof in the rotation axis direction is 15 mm or more. **Claim 4** The end mill for processing an adhesive layer-containing optical film according to any one of claims 1 to 3, wherein the upstream side in the rotation direction of the embedding portion as viewed from the rotation axis direction of the main body protrudes more than the downstream side in the rotation direction of the embedding portion. **Claim 5** The end mill for processing an adhesive layer-containing optical film according to claim 4, wherein the depth of the upstream side in the rotation direction of the embedding portion is 0.50 mm to 1.50 mm, and the depth of the downstream side in the rotation direction is 0.30 mm to 1.25 mm. **Claim 6** A method for manufacturing an end mill for processing an adhesive layer-containing optical film according to any one of claims 1 to 5, comprising: Embedding the cutting blade into the embedding portion of the main body; and Fixing the cutting blade to the embedding portion by vacuum brazing or high-frequency brazing in a state where the cutting blade is embedded in the embedding portion. The method includes: The cutting blade has a base portion made of a cemented carbide material and a sintered diamond layer provided on one surface of the base portion. Both the base portion and the sintered diamond layer are fixed to the embedding portion by vacuum brazing. Manufacturing method.

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