Method for shaping the cutting edge of a cutting tool

Abstract

To reduce shape errors in the shaping of the cutting edge of cutting tools. [Solution] The cutting edge shaping method for a cutting tool comprises a tool preparation step of preparing a cutting tool having an outer blade, and a cutting edge shaping step of shaping the cutting edge by spraying abrasive material from a nozzle onto the cutting edge of the outer blade so that the angle between the spraying direction of the abrasive material from the nozzle and the central axis of the cutting tool is the same as the helix angle of the cutting tool.

Description

Technical Field

[0001] The present disclosure relates to a method for forming the cutting edge of a cutting tool.

Background Art

[0002] There is known a technique for extending the life of a skiving cutter by forming a chamfer on the cutting edge of a tool cutter for skiving by means of blasting, thereby suppressing damage to the cutting edge (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In blasting on a cutting tool having a twist angle, such as a skiving cutter, for example, when abrasive is sprayed parallel to the central axis of the cutting tool, the shape error of the cutting tool tends to increase. When a workpiece is machined using a cutting tool with a large shape error, the machining quality of the workpiece is impaired. Therefore, a technique for reducing the shape error in forming the cutting edge of a cutting tool is desired.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one aspect of the present disclosure, there is provided a method for forming the cutting edge of a cutting tool. The method for forming the cutting edge of the cutting tool includes a tool preparation step of preparing a cutting tool having an outer peripheral edge, and a cutting edge forming step of forming the cutting edge by spraying the abrasive from the nozzle onto the cutting edge of the outer peripheral edge so that an angle between an injection direction of the abrasive from the nozzle and a central axis of the cutting tool is the same as a twist angle of the cutting tool. This method for shaping the cutting edge of a cutting tool can reduce the shape error of the cutting tool. (2) In the cutting edge shaping method of the cutting tool described above, in the cutting edge shaping step, the cutting tool may be rotated clockwise and counterclockwise around the central axis of the cutting tool. This method for shaping the cutting edge of a cutting tool makes it easier to shape the cutting edges of multiple outer blades by rotating the cutting tool. In addition, it makes it possible to ensure that the quality of each outer blade is the same. (3) In the cutting edge shaping method of the cutting tool according to the above configuration, the cutting tool may be rotated without pausing while the abrasive material is being sprayed. This method for shaping the cutting edge of a cutting tool does not require pausing the rotation of the cutting tool, thus shortening the time required for shaping the cutting edge. (4) In the cutting edge shaping method of the cutting tool according to the above configuration, the cutting tool may be rotated by an angle n (n = 360 degrees / number of teeth) while the abrasive material is being sprayed. According to this method for shaping the cutting edge of a cutting tool, the cutting tool is rotated by an angle n, making it easier to shape the cutting edges of multiple outer blades one by one in sequence. (5) In the cutting edge shaping method of the cutting tool according to the above embodiment, the cutting tool may be rotated in increments of an integer multiple of the angle n (n = 360 degrees / number of teeth) while the abrasive material is being sprayed. According to this method for shaping the cutting edge of a cutting tool, the cutting tool is rotated in integer multiples of the angle n, making it easier to shape the cutting edges of two or more of the multiple outer cutting edges at once. (6) In the cutting edge shaping method of the cutting tool described above, the cutting tool may be rotated by an angle n (n = 360 degrees / number of teeth) or by an integer multiple of the angle n, and the abrasive material may be sprayed toward the cutting edge while the rotation of the cutting tool is temporarily paused. This method for shaping the cutting edge of a cutting tool effectively reduces shape errors in the cutting tool compared to a method in which abrasive material is sprayed onto the cutting tool while it is rotating. This disclosure can also be implemented in various forms other than a method for shaping the cutting edge of a cutting tool. For example, it can be implemented in the form of a method for manufacturing a cutting tool, a method for regrinding a cutting tool, and so on. [Brief explanation of the drawing]

[0007] [Figure 1] Perspective view of a cutting tool for gear skiving. [Figure 2] Perspective view of the outer cutting edge. [Figure 3] An explanatory diagram showing the gear skiving process. [Figure 4] A flowchart illustrating the steps for manufacturing cutting tools. [Figure 5] An explanatory diagram showing the blade edge shaping process. [Figure 6] An explanatory diagram showing the percentage of shape error in cutting tools. [Modes for carrying out the invention]

[0008] A. First Embodiment: Figure 1 is a perspective view of a cutting tool 10 for gear skiving. The cutting tool 10 has a helical gear-like appearance. The cutting tool 10 has a plurality of outer peripheral blades 20 on its outer peripheral side surface. The plurality of outer peripheral blades 20 are arranged radially around the central axis RT of the cutting tool 10. Each outer peripheral blade 20 extends obliquely with respect to the central axis RT of the cutting tool 10. In this disclosure, the angle between the central axis RT of the cutting tool 10 and the direction of extension of the outer peripheral blades 20 is called the helix angle. The cutting tool 10 rotates around the central axis RT during cutting. For this reason, in the following description, the central axis RT will be referred to as the tool rotation axis RT.

[0009] Figure 2 is a perspective view of the outer peripheral cutting edge 20. The outer peripheral cutting edge 20 has a rake face 21, a front relief face 22, and two side relief faces 23L and 23R. The rake face 21 is the face facing the axial side of the cutting tool 10, the front relief face 22 is the face facing the radial side of the cutting tool 10, and the side relief faces 23L and 23R are the faces facing the circumferential side of the cutting tool 10. In this disclosure, the boundary between the rake face 21 and the front relief face 22 is called the cutting edge Ea, the boundary between the face opposite to the rake face 21 and the front relief face 22 is called the cutting edge Eb, and the boundary between the face between adjacent outer peripheral cutting edges 20 and the rake face 21 is called the cutting edge Ec. In the following description, when the side relief faces 23L and 23R are not specifically distinguished, they are simply referred to as the side relief face 23.

[0010] Figure 3 is an explanatory diagram showing the gear skiving process. Gear skiving is a machining method for forming gear teeth on a workpiece WK. In gear skiving, the cutting tool 10 and the workpiece WK are positioned so that the tool rotation axis RT, which is the rotation axis of the cutting tool 10, and the workpiece rotation axis RW, which is the rotation axis of the workpiece WK, intersect at a predetermined intersection angle α. Then, by the synchronous rotation of the cutting tool 10 and the workpiece WK, slip is generated between the outer cutting edge 20 of the cutting tool 10 and the workpiece WK, thereby forming gear teeth on the workpiece WK. By utilizing skiving, various types of gears, such as external gears and internal gears, can be manufactured.

[0011] Figure 4 is a flowchart showing the procedure for manufacturing a cutting tool 10, including the cutting edge shaping method in this embodiment. First, in step S10, the material for the cutting tool 10 is prepared. The shape of the material is, for example, cylindrical or cylindrical. The material of the material is, for example, high-speed steel or cemented carbide.

[0012] In the shape machining step S20, a plurality of outer peripheral edges 20 are formed on the workpiece. In the present embodiment, the plurality of outer peripheral edges 20 are formed on the workpiece by performing grinding on the workpiece. Note that in the present embodiment, a cutting tool 10 having a plurality of outer peripheral edges 20 is prepared by the steps from step S10 to step S20. For this reason, the steps from step S10 to step S20 may be referred to as a tool preparation step.

[0013] In the cutting edge forming step S30, the cutting edge Ea of the outer peripheral edge 20 is formed by performing blasting on the cutting edge Ea. Forming the cutting edge Ea means adjusting the shape of the cutting edge Ea. Adjusting the shape of the cutting edge Ea includes, for example, removing burrs on the cutting edge Ea, chamfering the cutting edge Ea, honing the cutting edge Ea, and the like.

[0014] In the coating step S40, a coating layer is formed on the surface of the cutting tool 10. For forming the coating layer, for example, the CVD method or the PVD method can be used. The material of the coating layer is, for example, titanium nitride or titanium aluminum nitride. By forming the coating layer, the wear resistance of the cutting tool 10 can be enhanced. However, the coating step may be performed as necessary, and if it is not necessary to form a coating layer on the surface of the cutting tool 10, the coating step may not be performed.

[0015] FIG. 5 is an explanatory view showing the state of the cutting edge forming step. In the present embodiment, in the cutting edge forming step, the cutting edge Ea of the outer peripheral edge 20 is formed by wet blasting. In wet blasting, a slurry SL is generated by mixing particulate abrasive and liquid, and the slurry SL is jetted from a nozzle (not shown) toward the cutting edge Ea of the outer peripheral edge 20 by compressed air so that the angle between the jet direction Dp of the slurry SL from the nozzle and the tool rotation axis RT becomes the same as the twist angle θ of the cutting tool 1). For the abrasive, for example, zirconia can be used. For the liquid, for example, water can be used.

[0016] In this embodiment, during wet blasting, that is, while spraying the slurry SL containing abrasive from the nozzle onto the cutting tool 10, the cutting tool 10 is rotated at least in one of the clockwise and counterclockwise directions about the tool rotation axis RT, so that the slurry SL impinges on the cutting edges Ea of all the outer peripheral cutting edges 20. The cutting tool 10 is rotated so that the angle between the spraying direction Dp of the slurry SL and the tool rotation axis RT remains the same as the twist angle θ of the cutting tool 10 even during the rotation of the cutting tool 10. From the start to the end of the wet blasting process, the slurry SL is sprayed from the nozzle so that the spraying pressure of the slurry SL is constant, and the cutting tool 10 is rotated so that the rotation speed of the cutting tool 10 is constant.

[0017] In this embodiment, during wet blasting, the spraying of the slurry SL is not temporarily stopped. Therefore, the spraying pressure of the slurry SL from the nozzle in wet blasting can be stabilized. In addition, in this embodiment, during wet blasting, the rotation of the cutting tool 10 is not temporarily stopped. Therefore, in this embodiment, the processing time by wet blasting can be shortened, and the quality of each outer peripheral cutting edge 20 can be made equivalent.

[0018] Regarding the spraying pressure of the slurry SL from the nozzle in wet blasting, the rotation speed of the cutting tool 10, the rotation direction of the cutting tool 10, the number of rotations of the cutting tool 10, the distance between the nozzle and the cutting edge Ea, the types of abrasive and liquid contained in the slurry SL, the processing time, etc., they can be appropriately determined according to the shape and material of the cutting tool 10.

[0019] Here, as shown in the comparative example in Figure 5, when the spray direction Dp of the slurry SL during wet blasting is kept parallel to the tool rotation axis RT, the larger the helix angle θ of the cutting tool 10, the more likely it is that the processing efficiency of the wet blasting will be uneven for each part of the outer edge 20. For example, when the spray direction Dp of the slurry SL is parallel to the tool rotation axis RT, differences occur in the collision angle and collision velocity of the slurry SL between one of the left and right side relief surfaces 23L and 23R. As a result, differences occur in the processing efficiency of the wet blasting between one of the left and right side relief surfaces 23L and 23R, and shape errors of the outer edge 20 are likely to occur. In contrast, in this embodiment, the angle between the spray direction Dp of the slurry SL during wet blasting and the tool rotation axis RT is kept the same as the helix angle θ of the cutting tool 10. Therefore, differences in the collision angle and collision velocity of the slurry SL between one of the left and right side relief surfaces 23L and 23R are less likely to occur.

[0020] Figure 6 is an explanatory diagram showing the percentage of shape error of the outer peripheral blade 20 after cutting edge shaping. In Figure 6, the percentage of shape error of the outer peripheral blade 20 after cutting edge shaping by wet blasting is represented by a bar graph. "Blade shape" shows the percentage of shape error at the measurement point on the dashed line La shown in Figure 2, and "Blade ridge" shows the percentage of shape error at the measurement point on the dashed line Lb shown in Figure 2. In both "Blade shape" and "Blade ridge," "Left" shows the percentage of shape error at the measurement point on the left side relief surface 23L, and "Right" shows the percentage of shape error at the measurement point on the right side relief surface 23R. The shorter the bar in the bar graph, the smaller the shape error. Comparing this embodiment with the comparative example described above, this embodiment has a smaller percentage of shape error.

[0021] According to the cutting edge shaping method of this embodiment described above, when shaping the cutting edge Ea of the outer peripheral blade 20 by wet blasting, the slurry SL is sprayed from the nozzle toward the cutting edge Ea of the outer peripheral blade 20 so that the angle between the spraying direction Dp of the slurry SL from the nozzle and the tool rotation axis RT is the same as the helix angle θ of the cutting tool 10. Therefore, the shape error of the outer peripheral blade 20 in wet blasting can be reduced.

[0022] In this cutting tool 10, which has multiple outer peripheral blades 20, the lifespan of the cutting tool 10 is determined by the lifespan of the outer peripheral blade 20 with the lowest quality. In this embodiment, during wet blasting, the cutting tool 10 is rotated around the tool rotation axis RT, causing the slurry SL to collide with the cutting edges Ea of all the outer peripheral blades 20. In addition, the cutting tool 10 is rotated in such a way that the angle between the slurry SL ejection direction Dp and the tool rotation axis RT remains the same as the helix angle θ of the cutting tool 10. Therefore, the quality of the multiple outer peripheral blades 20 of the cutting tool 10 can be made uniform, thereby extending the lifespan of the cutting tool 10.

[0023] B. Other embodiments: (B1) In the first embodiment described above, the injection of slurry SL and the rotation of the cutting tool 10 are not paused during wet blasting. In contrast, at least one of the injection of slurry SL and the rotation of the cutting tool 10 may be paused during wet blasting. For example, as shown below, the rotation of the cutting tool 10 may be paused without pausing the injection of slurry SL during wet blasting. Alternatively, both the injection of slurry SL and the rotation of the cutting tool 10 may be paused during wet blasting.

[0024] <Method 1 for temporarily pausing the rotation of the cutting tool> In a configuration in which the rotation of the cutting tool 10 is temporarily paused, the slurry SL ejected from the nozzle may be sprayed so as to collide with the cutting edge Ea of one outer peripheral blade 20, and the rotation angle of the cutting tool 10 from the start of rotation to the pause may be set to an angle n (n = 360 degrees / number of blades). In this case, it is suitable for shaping the cutting edges Ea of the outer peripheral blade 20 one by one. However, the slurry SL ejected from the nozzle may be sprayed so as to collide with the cutting edges Ea of multiple outer peripheral blades 20.

[0025] <Method 2 for temporarily pausing the rotation of the cutting tool> In a configuration in which the rotation of the cutting tool 10 is temporarily paused, the slurry SL ejected from the nozzle may be sprayed so as to collide with the cutting edges Ea of two or more outer peripheral blades 20, and the rotation angle of the cutting tool 10 from the start of rotation to the pause may be an integer multiple of the angle n (n = 360 degrees / number of blades). In this case, it is suitable for shaping the cutting edges Ea of two or more outer peripheral blades 20 at once.

[0026] During wet blasting, the cutting tool 10 may be rotated by an angle n (n = 360 degrees / number of teeth), or by an integer multiple of the angle n. The injection of slurry SL from the nozzle may be temporarily suspended while the cutting tool 10 is rotating, and the slurry SL may be injected from the nozzle towards the cutting edge Ea while the rotation of the cutting tool 10 is temporarily suspended. In this case, the rotation of the cutting tool 10 can suppress the collision of slurry SL with the side relief surfaces 23L and 23R from the circumferential direction of the cutting tool 10, thereby effectively reducing the shape error of the outer cutting edge 20.

[0027] (B2) In each of the embodiments described above, the cutting tool 10 is rotated during wet blasting. However, it is not necessary to rotate the cutting tool 10 during wet blasting. For example, the cutting edges Ea of all the outer cutting edges 20 can be formed by rotating the nozzle or by spraying slurry SL onto the multiple outer cutting edges 20 of the cutting tool 10 from multiple nozzles.

[0028] (B3) In each of the embodiments described above, the type of blasting used in the cutting edge shaping process is wet blasting. In contrast, the type of blasting used in the cutting edge shaping process may be dry blasting. When dry blasting is used in the cutting edge shaping process, particulate abrasive material is ejected from the nozzle by compressed air. Even when dry blasting is used, the abrasive material is ejected from the nozzle toward the cutting edge Ea of the outer blade 20 such that the angle between the ejection direction Dp of the abrasive material from the nozzle and the tool rotation axis RT is the same as the helix angle θ of the cutting tool 10.

[0029] (B4) In each of the embodiments described above, the cutting edge shaping process is performed when the cutting tool 10 is manufactured. In contrast, the cutting edge shaping process may be performed when the cutting edge of a used cutting tool 10 is regrinded.

[0030] (B5) In each of the embodiments described above, the cutting edge shaping process is performed on the cutting tool 10 for skiving. In contrast, the cutting edge shaping process may also be performed on cutting tools that have a helix angle, such as cutting tools for hobbing or cutting tools for gear shaping.

[0031] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0032] 10…Cutting tool, 20…Outer edge, 21…Rake face, 22…Front relief face, 23,23L,23R…Side relief face, Dp…Spray direction, Ea…Cutting edge, Eb…Cutting base, Ec…Cutting base, RT…Tool rotation axis (central axis), RW…Workpiece rotation axis, SL…Slurry, WK…Workpiece, θ…Helix angle

Claims

1. A method for shaping the cutting edge of a cutting tool, A tool preparation step involves preparing a cutting tool having an outer cutting edge, A cutting edge shaping step is performed by spraying the abrasive material from the nozzle onto the cutting edge of the outer blade so that the angle between the spraying direction of the abrasive material from the nozzle and the central axis of the cutting tool is the same as the helix angle of the cutting tool, A method for shaping the cutting edge of a cutting tool, comprising the features described above.

2. A method for shaping the cutting edge of a cutting tool according to claim 1, A method for shaping the cutting edge of a cutting tool, wherein in the cutting edge shaping step, the cutting tool is rotated clockwise and counterclockwise around the central axis of the cutting tool.

3. A method for shaping the cutting edge of a cutting tool according to claim 2, A method for shaping the cutting edge of a cutting tool, wherein the cutting tool is rotated without pausing while the abrasive material is being sprayed.

4. A method for shaping the cutting edge of a cutting tool according to claim 2, A method for shaping the cutting edge of a cutting tool, wherein the cutting tool is rotated by an angle n (n = 360 degrees / number of teeth) while the abrasive material is being sprayed.

5. A method for shaping the cutting edge of a cutting tool according to claim 2, A method for shaping the cutting edge of a cutting tool, wherein the cutting tool is rotated in increments of an integer multiple of the angle n (n = 360 degrees / number of teeth) while the abrasive material is being sprayed.

6. A method for shaping the cutting edge of a cutting tool according to claim 2, The cutting tool is rotated by an angle n (n = 360 degrees / number of teeth), or by an integer multiple of the angle n. A method for shaping the cutting edge of a cutting tool, comprising spraying the abrasive material toward the cutting edge while the rotation of the cutting tool is temporarily paused.

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