Skiving tools, devices and methods

Abstract

To provide a processing technique which allows skiving to be performed also in a lathe machine tool of biaxial control.SOLUTION: Provided is a skiving tool with a helical tooth for performing skiving without using both ends of a cutting edge of the helical tooth. Further, the helical tooth is manufactured by cutting an end mill. The end mill has three blades or two blades. Further, the helical tooth is an external diameter throwaway tip or an internal diameter throwaway tip.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to skiving tools, devices and methods. [Background technology]

[0002] A known method for cutting the rotationally symmetric surface of a rotating workpiece (object to be machined) is the skiving method, in which a cutting edge (straight blade) arranged at an angle to the workpiece's rotation axis is introduced along the rotating workpiece in a linear feed motion that crosses the rotation axis while making contact with the workpiece. When cutting the workpiece using this method, the inclination angle of the straight blade relative to the rotation axis is set to a range greater than 0° and less than 90°.

[0003] Patent Document 1 discloses a technique for reducing the surface roughness of the outer peripheral surface of a workpiece cut by skiving using a straight blade. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6428919 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the case of skiving using a straight blade, it is necessary to control three axes: the extension direction of the workpiece's rotation axis (Z axis), the direction in which the cutting tool cuts into the workpiece (X axis), and the tangential direction (Y axis) perpendicular to both the Z axis and the X axis. On the other hand, a typical lathe machine tool performs cutting using two-axis control. In other words, there is no Y axis direction, and cutting is performed by controlling the feed rate in the Z axis direction and the cutting depth in the X axis direction.

[0006] The present invention was completed through extensive research focusing on these issues, and its purpose is to provide a machining technology that enables skiving to be performed even on a two-axis controlled lathe machine tool. [Means for solving the problem]

[0007] In order to solve the above problem, the present invention is a skiving tool having a twisted blade, which performs skiving without using both ends of the cutting edge of the twisted blade.

[0008] The present invention is a skiving device using a machine tool that includes a chuck that rotatably holds a workpiece on a first axis and a tool rest that mounts a skiving tool having a helical blade, the feed rate of the helical blade being set in the first axial direction and the cutting depth of the helical blade being set in a second axis perpendicular to the first axial direction, and the skiving tool performs skiving without using both ends of the cutting edge of the helical blade.

[0009] The present invention is a skiving method using a machine tool equipped with a chuck that rotatably holds a workpiece on a first axis and a tool post to which a skiving tool having a twisted blade is attached, in which the workpiece is fixed to the chuck, the chuck is rotated, the skiving tool is aligned with the first axis, the feed rate of the twisted blade is set in the first axial direction, and the cutting depth of the twisted blade is set in a second axis perpendicular to the first axial direction. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a machining technique that enables skiving to be performed even on a two-axis controlled lathe machine tool. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view of a cutting tool according to a first embodiment of the present invention; [Figure 2]3A to 3C are diagrams illustrating a method for manufacturing a twisted blade according to the first embodiment of the present invention. [Figure 3] 1A to 1C are diagrams illustrating skiving using a twisted blade according to a first embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged view of a part of FIG. 3. [Figure 5] 3A and 3B are diagrams for explaining the contact area of ​​the blade according to the degree of twist of the twisted blade according to the first embodiment of the present invention. [Figure 6] FIG. 1 is a front view of a skiving device according to a first embodiment of the present invention. [Figure 7] 1 is a flowchart of a skiving method according to a first embodiment of the present invention. [Figure 8] 10A to 10C are diagrams illustrating a method for manufacturing a twisted blade according to a second embodiment of the present invention. [Figure 9] FIG. 10 is a perspective view of a cutting tool according to a third embodiment of the present invention. [Figure 10] FIG. 10 is a perspective view of a twisted blade according to a third embodiment of the present invention. [Figure 11] FIG. 10 is a view for explaining a cutting tool according to a fourth embodiment of the present invention. [Figure 12] FIG. 10 is a diagram illustrating a twisted blade according to a fourth embodiment of the present invention. [Figure 13] FIG. 10 is a diagram illustrating a cutting tool according to a modified example of the fourth embodiment of the present invention. [Figure 14] FIG. 10 is a view for explaining a cutting tool according to a fifth embodiment of the present invention. [Figure 15] FIG. 13 is a diagram for explaining components of a cutting force according to the fifth embodiment of the present invention. [Figure 16] FIG. 13 is a diagram for explaining components of cutting force according to a helix angle according to the fifth embodiment of the present invention. [Figure 17] 10A and 10B are diagrams for explaining a finished surface and a surface shape according to a fifth embodiment of the present invention. [Figure 18] FIG. 10 is a diagram illustrating surface roughness according to the fifth embodiment of the present invention. [Figure 19] FIG. 10 is a diagram illustrating residual stress according to the fifth embodiment of the present invention. [Figure 20] FIG. 1 is a diagram for explaining an analysis model of inner diameter mill skiving. [Figure 21] FIG. 1 is a diagram for explaining an analysis model of outer diameter mill skiving. [Figure 22] FIG. 10 is a diagram for explaining an end mill model. [Figure 23] FIG. 10 is a diagram for explaining the azimuth angle of a workpiece. [Figure 24] FIG. 13 is a diagram for explaining components of cutting force according to the sixth embodiment of the present invention. [Figure 25] FIG. 10 is a diagram illustrating skiving using a twisted blade according to a sixth embodiment of the present invention. [Figure 26] 13 is a graph of cutting force components according to a comparative example and the sixth embodiment of the present invention. [Figure 27] 10 is a graph of cutting force components according to a sixth embodiment of the present invention. [Figure 28] FIG. 13 is a diagram for explaining the cutting depth and cutting force components according to the sixth embodiment of the present invention. [Figure 29] FIG. 13 is a diagram for explaining the cutting depth and cutting force components according to a comparative example compared to the sixth embodiment of the present invention. [Figure 30] 10A and 10B are diagrams for explaining a finished surface and a surface shape according to a sixth embodiment of the present invention. [Figure 31] 13A and 13B are diagrams for explaining a finished surface and a surface shape according to a comparative example of the sixth embodiment of the present invention. [Figure 32] FIG. 13 is a diagram illustrating residual stress according to the sixth embodiment of the present invention. [Figure 33] FIG. 13 is a view for explaining end face cutting according to a comparative example to the seventh embodiment of the present invention. [Figure 34] FIG. 13 is a view for explaining end face cutting according to a seventh embodiment of the present invention. [Figure 35] 13A and 13B are diagrams for explaining a finished surface and a surface shape according to a seventh embodiment of the present invention. [Figure 36] FIG. 13 is a diagram for explaining a finished surface and a surface shape according to a comparative example of the seventh embodiment of the present invention. [Figure 37] FIG. 13 is a diagram illustrating residual stress according to the seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will be described with reference to the drawings. Common parts in the drawings are designated by the same reference numerals, and duplicated explanations will be omitted. The Z-axis direction is the direction in which the rotation axis of the workpiece extends, the X-axis direction is the direction in which the cutting tool cuts into the workpiece, and the Y-axis direction is the tangential direction perpendicular to both the Z-axis and the X-axis.

[0013] A typical lathe machine tool performs cutting using two-axis control, meaning there is no Y-axis direction, and cutting is performed using the feed amount in the Z-axis direction and the depth of cut in the X-axis direction.

[0014] (First embodiment) FIG. 1 is a perspective view of a cutting tool according to a first embodiment of the present invention. The cutting tool 100 includes a twisted cutting edge 110, a shank 120 that holds the twisted cutting edge 110, a clamp 130 that fixes the twisted cutting edge 110 to the shank 120, and a screw 140 for tightening the clamp. The cutting tool 100 is also called a cutting tool, and the shank 120 is also called a cutting tool holder. The twisted cutting edge 110 is replaceable and is also called a throw-away tip. The cutting tool 100 is also called a throw-away cutting tool.

[0015] The twisted blade 110 is formed by cutting off the tip of the cutting edge of a three-blade end mill, which will be described later. The twisted blade 110 cuts the outer diameter of the workpiece between point A and point B. For this reason, the twisted blade 110 is also called an outer diameter throw-away tip. In addition, the three twisted cutting edges of the twisted blade 110 can be used by loosening the screw 140 and rotating it around the Y axis.

[0016] In this embodiment, the thickness of the twisted blade 110 is, for example, 5 mm, and the distance between point A and point B is, for example, 1 mm. In this way, the radial cutting depth of the workpiece can be controlled between, for example, 0.05 mm and 0.1 mm.

[0017] FIG. 2 is a diagram illustrating a method for manufacturing a helical blade according to the first embodiment of the present invention. The end mill 200 in FIG. 2(b) is a commercially available three-blade product. In the case of a three-blade product, the helix angle is generally 45°. The diameter of the end mill is 8 to 10 mm.

[0018] The twisted blade 110 shown in Figure 2(a) can be produced by cutting off a portion (shown by a two-dot chain line) approximately 5 mm from the tip of the cutting edge of the end mill 200 shown in Figure 2(b). Chips cut by the twisted blade 110 are discharged along flutes 230. The portion 210 surrounded by a dotted line is the relief groove of the end cutting edge of the end mill 200. The twisted blade is not limited to the tip of the cutting edge of the end mill 200; after cutting the twisted blade 110 shown in Figure 2(b), the next tip portion may be cut off and used as the twisted blade 110'. Unlike the twisted blade 110, the twisted blade 110' does not have a relief groove of the end cutting edge of the end mill 200.

[0019] FIG. 3 is a diagram illustrating skiving using a twisted blade according to a first embodiment of the present invention. FIG. 3(a) shows a state in which a chuck 310 of a machine tool is holding a workpiece W1. The workpiece W1 has a round rod shape. The entire machine tool is not shown, but the chuck 310 holds the workpiece W1 so that it can rotate around the Z axis. When the machine tool rotates the chuck 310, the workpiece W1 also rotates. In FIG. 3(a), the twisted blade 110 is hidden behind the workpiece W1, and is therefore represented by a dotted line.

[0020] Figure 1(b) is a cross-sectional view showing the twist cutting edge 110 cutting the outer diameter of the workpiece W1. The Z axis is the rotation axis of the workpiece W1, and it determines the feed amount of the twist cutting edge 110. The X axis is the cutting axis, and the twist cutting edge 110 is used to cut into the workpiece W1 from point A to point B. The Y axis is a direction perpendicular to both the Z axis and the X axis, and indicates the tangent direction to the cross-sectional circle of the workpiece W1. A typical lathe machine tool moves along only two axes, the Z axis and the X axis, but in the case of a multi-axis machine, the Y axis is also used.

[0021] Figure 4 is an enlarged view of a portion of Figure 3, enlarging the area enclosed by the two-dot chain line in Figure 3(b). Point A indicates the start point where the helical blade cuts into the workpiece rotating around the Z axis. Point B indicates the state where the helical blade has reached the finished surface while cutting into the workpiece. In this way, it is possible to perform outer diameter cutting with a cutting depth of 0.05 mm to 0.1 mm. The cutting depth can also be considered the depth of cut toward the center of the Z axis.

[0022] 3, the helical blade 110 is fed a predetermined distance in the Z-axis direction, thereby cutting the outer diameter of the workpiece W1. In this way, skiving is performed using the tip of the cutting edge of the end mill, so this can be called mill skiving.

[0023] FIG. 5 is a diagram illustrating the blade contact area according to the degree of twist of the helical blade according to the first embodiment of the present invention. FIG. 5(a) shows a state in which the end mill 200 itself is used to cut the outer diameter of a rotating workpiece W1 without cutting off the tip of the end mill 200. The end mill 200 is not rotating; it is simply moving at a predetermined feed rate in the direction of the rotation axis Z of the workpiece W1. Here, the portion of the helical blade of the end mill 200 used for cutting the outer diameter is the portion surrounded by the two-dot chain line. This portion surrounded by the two-dot chain line corresponds to the helical blade 110. Although the end mill 200 is composed of three helical blades, there is no particular limit to the number of helical blades; it is sufficient that a portion of the helical blade at the tip of the end mill 200 can cut into the outer diameter of the workpiece W1.

[0024] Figure 1(b) shows the cutting portion AB of the twisted blade 110-1 when the twist angle is 20°. Figure 1(c) shows the cutting portion AB of the twisted blade 110-2 when the twist angle is 45°. The cutting portion AB is the area where the twisted blade 110 comes into contact with the workpiece W1. When the twist angle is weak (20° in Figure 1(b)), the length of the cutting portion AB is longer than when the twist angle is strong (45° in Figure 1(c)).

[0025] The length of the cutting portion of the twist blade 110 changes depending on the twist angle of the twist blade 110 used in cutting. In this way, the feed amount of the twist blade 110 (or the end mill 200) per rotation of the workpiece W1 can be set by taking into account or calculating the length of the cutting portion of the twist blade 110. Here, it is preferable to set the twist angle of the twist blade between 15° and 50°.

[0026] Fig. 6 is a front view of a skiving device according to a first embodiment of the present invention. Fig. 6(a) shows a state in which a cutting tool 100 is attached to a machine tool 300. The machine tool 300 is a two-axis (X-axis and Z-axis) controlled lathe. A chuck 310 of the machine tool 300 holds a cylindrical workpiece W1 so that it can rotate around the Z-axis. The cutting tool 100 has a helical blade 110, which is the tip of an end mill cut off, attached to a shank 120. The shank 120 is attached from bottom to top (in the X direction) to a tool rest 320 of the machine tool 300.

[0027] The tool rest 320 is movable in three axial directions. The cutting edge of the twist blade 110 is raised in the vertical direction (X direction) from the central axis (Z axis) of the workpiece W1 and aligned with the tangent direction of the circle (Y direction). The cutting depth of the twist blade 110 is set in the X direction, and the feed rate of the twist blade 110 is set in the Z direction. By attaching the twist blade 110 to the machine tool 300 in this way, it is possible to provide a skiving machine.

[0028] FIG. 1(b) is a front view of a skiving device using an end mill 200 instead of the cutting tool 100. The end mill 200 is attached to the tool post 321 from left to right (in the Z direction). As in FIG. 1(a), the cutting edge of the end mill 200 is aligned in the Y direction, the cutting depth of the end mill 200 is set in the X direction, and the feed rate of the end mill 200 is set in the Z direction. In this way, by attaching the end mill 200 to a three-axis controlled machine tool 300 (for example, a machining center or a multi-tasking machine), it is possible to provide a skiving device.

[0029] In Fig. 3(a), a twisted blade with the tip of an end mill cut off is attached to a machine tool 300, and in Fig. 3(b), the end mill 200 itself is attached to the machine tool 300. These skiving machines are collectively called mill skiving machines.

[0030] Fig. 7 is a flowchart of the skiving method according to the first embodiment of the present invention. Here, the explanation will be based on the case of Fig. 6(a). The workpiece W1 is fixed to the chuck 310 of the machine tool 300 (S1). The chuck 310 is rotated by a predetermined amount (S2). The cutting tool 100 attached to the tool rest 320 of the machine tool 300 is aligned in the Z-axis direction (S3). The amount by which the cutting tool is fed in the Z-axis direction (cutting feed amount) is set (S4). The depth of cut is set (S5).

[0031] 6(a) is a two-axis controlled machine tool, so it is necessary to align the cutting tool 100 in the Y direction beforehand, before aligning it in the Z direction in S3. The cutting feed amount in S4 is set per rotation in the Z direction, and also sets the start and end points in the Z direction. The cutting depth in S5 is set as the cutting depth in the X direction.

[0032] The skiving method described in FIG. 7 can be applied not only to two-axis controlled machine tools but also to three-axis controlled machining centers. In this case, the cutting depth of S5 can be set as the cutting depth in either the X or Y direction. The tool rest 320 corresponds to the tool spindle of the machining center. The flowchart in FIG. 7 may be controlled by the hardware of the machine tool 300, or may be controlled as a software program executable by a computer that operates the machine tool 300.

[0033] (Second embodiment) FIG. 8 is a diagram illustrating a method for manufacturing a helical blade according to a second embodiment of the present invention. The end mill 201 in FIG. 8(b) is a commercially available two-blade product. In the case of two blades, the helix angle is generally 30°. The diameter of the end mill is 8 to 10 mm.

[0034] By cutting off a portion of about 5 mm (shown by a two-dot chain line) from the tip of the end mill 201 in Fig. 2(b), the twisted cutting edge 111 in Fig. 2(a) can be manufactured. The portion 211 surrounded by the dotted line is the relief groove for the bottom cutting edge of the end mill 201.

[0035] (Third embodiment) 9 is a perspective view of a cutting tool according to a third embodiment of the present invention. The cutting tool 101 includes a helical blade 112 for cutting the outer diameter of a cylindrical workpiece, a shank 120 for holding the helical blade 112, a clamp 131 for fixing the helical blade 112 to the shank 120, and a screw 140 for tightening the clamp.

[0036] 9 differs from FIG. 1 in that the twisted blade 112 has a single blade and is hollow in the center. Therefore, the tip pin of the clamp 131 is longer than in FIG. 1 and reaches the shank 120, fixing the twisted blade 112 to the shank 120.

[0037] Figure 10 is a perspective view of a twisted blade according to a third embodiment of the present invention. The twisted blade 112 can be manufactured by cutting the material of a throw-away tip into a rectangular parallelepiped shape approximately 5 mm thick, hollowing out the center, and then removing the area indicated by the two-dot chain line through cutting and grinding. The twisted blade has a 45° twist angle. As explained in Figure 4, points A and B are the cutting start point and the point where the cutting reaches the finished surface. The twisted blade 112 can also be called an outer diameter throw-away tip.

[0038] (Fourth embodiment) 11 is a diagram illustrating a cutting tool according to a fourth embodiment of the present invention. Fig. 11(a) is a perspective view of a cutting tool 102. The cutting tool 102 includes a twisted blade 113 that cuts the inner diameter of a cylindrical workpiece, a shank 121 that holds the twisted blade 113, and a screw 141 that fixes the twisted blade 113 directly (without a clamp) to the shank 121.

[0039] The difference between Figure 11(a) and Figure 9 is that a female thread is cut in the center of the twisted blade 113, and that the part of the shank 121 that fixes the twisted blade 113 also has a female thread. The twisted blade 113 is fixed to the shank 121 by tightening a male screw 141. Figure 11(b) is a cross-sectional view of a cylindrical workpiece W2. The figure shows the cylindrical workpiece W2 being inserted into the cutting tool 102, with the twisted blade 113 cutting the inner diameter of the workpiece W2.

[0040] Figure 12 is a diagram illustrating a twisted cutting edge according to a fourth embodiment of the present invention. Figure 12(a) is a view of the twisted cutting edge 113 as seen from the arrow A in Figure 11(a). The twisted cutting edge 113 can be manufactured by cutting the material of a throw-away tip into a rectangular parallelepiped with a thickness of 4 mm, and removing the portion indicated by the two-dot chain line on the outside of the twisted cutting edge 113 by cutting and grinding, in the same manner as described in Figure 10.

[0041] FIG. 12(b) is a view of the helical cutting edge 113 as viewed from the arrow B in FIG. 11(a). As described in FIG. 4, points A and B are the cutting start point and the point where the cutting edge reaches the finished surface. The thickness of the helical cutting edge 113 is 4 mm, and the helix angle is 30°. The helical cutting edge 113 can also be called an internal diameter throw-away tip. As in the first embodiment, the helical cutting edge used to cut the inner diameter of a cylindrical workpiece may be the tip of an end mill or the entire end mill. FIG. 13 is a diagram illustrating a cutting tool according to a modified example of the fourth embodiment of the present invention. This figure is a cross-sectional view of a cylindrical workpiece W2. The figure shows the state in which the end mill 200 is inserted into the cylindrical workpiece W2 and the helical cutting edge 110 is cutting the inner diameter of the workpiece W2.

[0042] (Fifth embodiment) FIG. 14 is a diagram illustrating a cutting tool according to a fifth embodiment of the present invention. FIG. 14(a) is a side view of a cutting tool 103. The cutting tool 103 is an end mill. FIG. 14(a) omits the shank of the end mill and shows the body portion with a helical cutting edge 114 attached to the outer peripheral side surface. Chips cut by the helical cutting edge 114 are discharged along flutes 231. An end cutting edge 221 is attached to the tip surface of the body portion. FIG. 14(b) shows a cross section 1-2 of the cutting tool 103 in FIG. 14(a). FIG. 14(c) shows a cross section 3-4 of the cutting tool 103 in FIG. 14(a).

[0043] FIG. 14 shows the cutting mode of the cutting tool 103 for finishing the inner peripheral surface of a cylindrical workpiece (labeled "Workpiece"). The helical blade 114 makes a cut into the inner peripheral surface of the workpiece and feeds it in the longitudinal direction, removing the cutting area (labeled "Removal area"). Because the helical blade 114 has a helix angle, it bites into the machining surface at point A, and makes a continuous cut in the radial direction of the workpiece toward the right in FIG. 14(a), reaching a predetermined depth of cut at point B. Therefore, the orientation of the bottom cutting edge 220 is set according to the helix angle and the set depth of cut so that the helical blade 114 at point B achieves the set depth of cut. Here, the azimuth angle of the end mill at point A is φ AThen, the cutting edge length L involved in material removal is expressed by the following equation:

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[0044] However, R T , γ are the radius and helix angle of the end mill. When the feed rate per revolution of the workpiece is f, the set depth of cut is achieved at L / f revolutions, and the inner surface is finished. Therefore, as will be described later, a good finished surface is obtained, and the residual stress also tends to be compressive.

[0045] On the other hand, chips are discharged along the flutes of the end mill. Generally, when machining the inner surface of a hollow hole, scraping of the chips against the finished surface is often a problem. In this embodiment, the flutes guide the chips and discharge them out of the hole, thereby suppressing scraping of the chips against the finished surface.

[0046] Fig. 15 is a diagram for explaining the components of cutting forces according to a fifth embodiment of the present invention. Fig. 15 explains the cutting force components when cutting the inner surface of the cylindrical workpiece described in Fig. 14. Fig. 15(a) shows the vector components of the cutting force when a general-purpose turning cermet tool (Kyocera TN620) 400 is used (labeled "Turning"), and Fig. 15(b) shows the vector components of the cutting force when a 10 mm diameter two-flute end mill (UNION TOOL CSS2100-1500, helix angle 30°) 103 is used (labeled "Mill skiving").

[0047] To measure the cutting force, each tool was attached to the turret of a CNC lathe (OKUMA SPACE TURN LB3000 EX) via a piezoelectric cutting dynamometer (Kistler 9251A). z , back force F y , feed force F x Please note that the coordinate axis is different from the case where the extension direction of the rotation axis of the workpiece is the Z-axis direction.

[0048] The workpiece was carbon steel (S45C) with an inner diameter of 26 mm. The cutting conditions were a cutting speed of 150 m / min, a feed rate of 0.1 mm / rev, and a radial depth of cut of 0.05 mm, and the cutting was performed dry.

[0049] In the case of the general turning tool 400 in FIG. 1(a), the normal to the main cutting edge is inclined in the feed direction, so the feed force F x On the other hand, since the normal to the cutting edge of the end mill 103 in this embodiment is inclined in the radial direction of the workpiece, the cutting force is applied in the direction of (b) in the same figure. Therefore, the feed force F x The Y component in the figure is shown as a negative value based on the direction of the measured cutting force component.

[0050] 16 is a diagram illustrating the cutting force components according to the helix angle in the fifth embodiment of the present invention. The diagram compares the cutting force components of the end mill 103 with helix angles of 25°, 30°, and 40°, and the general turning tool 400 (Turning). According to formula (1), when the helix angle γ is small, the cutting edge length L acting in cutting becomes long. Therefore, the cutting force is large at a helix angle of 25°.

[0051] FIG. 17 is a diagram illustrating the finished surface and surface profile according to the fifth embodiment of the present invention. The finished surface roughness was measured using a laser confocal microscope (KEYENCE VX-X100). (a) of FIG. 17 shows the finished surface and surface profile (surface profile) obtained by mill skiving using an end mill 103 with a helix angle of 30°. (b) of FIG. 17 shows the finished surface and surface profile obtained by turning using a general turning tool 400. In turning, cutting marks corresponding to the nose radius and feed rate of the tool can be observed. However, in mill skiving, continuous cutting is performed by rotating the workpiece and moving the tool in the axial direction. This results in a uniform surface profile.

[0052] FIG. 18 is a diagram illustrating the surface roughness according to the fifth embodiment of the present invention. The figure compares the surface roughness in cutting tests using an end mill 103 with a helix angle of 25°, 30°, or 40°, as well as a general turning tool 400 (Turning). (a) of FIG. 18 shows Ra (arithmetic mean roughness). (b) of FIG. 18 shows Rz (maximum height roughness). According to formula (1), the smaller the helix angle γ in mill skiving, the longer the cutting edge length L, and the greater the number of revolutions of the workpiece until the set depth of cut is reached. Therefore, at a helix angle of 25°, the depth of cut per revolution of the workpiece is smaller. This results in a better finished surface.

[0053] Figure 19 is a diagram illustrating residual stresses according to the fifth embodiment of the present invention. Here, residual stresses in the axial and circumferential directions of the finished surface were measured using a residual stress measuring instrument (PULSREC μ-X360n). The figure compares residual stresses in mill skiving with a 30° helix angle and turning. In turning, tensile stresses are generated at the cutting edge, separating the chips from the finished surface. As a result, tensile residual stresses are likely to occur on the surface, as shown in the figure. In contrast, in mill skiving, the depth of cut is gradually increased with the rotation of the workpiece and the feed of the tool, resulting in a smaller depth of cut on the final finished surface. As a result, the pushing force of the cutting edge becomes greater than the chip-forming force. Furthermore, when the depth of cut is less than the minimum chip thickness, no chips are generated, and the cutting edge acts to smooth the finished surface. As a result, the residual stress in the surface layer becomes compressive.

[0054] (Analysis model of mill skiving) The analytical model for mill skiving will be explained separately for inner diameter cutting and outer diameter cutting.

[0055] (1. Internal mill skiving) Figure 20 is a diagram for explaining the analytical model of internal mill skiving. Figure (a) shows the geometric relationships when an end mill (labeled Tool) cuts the internal diameter of a cylindrical workpiece (labeled Workpiece). Figure (b) is an enlarged view of a portion of Figure (a). Figure (c) is a list of symbols showing the geometric relationships. Figure (d) is a diagram for supplementary explanation of the geometric relationships. Note that when the radius R of the cylindrical workpiece (workpiece) is w Please note that is the value obtained by adding the finishing depth of cut d to the inner diameter of the hole, not the value obtained by adding the wall thickness to the inner diameter of the hole.

[0056] First, the geometric relationship of mill skiving will be explained. i Radius r from the center of the workpiece i is a triangle OO'P i Applying the cosine law to

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[0057] Azimuth angle θ from the center of the workpiece i and the angle α between the normal to the cutting speed direction and the rake face Ri is expressed by the following equation according to the sine law:

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[0058] The axial length L of the cutting edge involved in cutting is expressed by the following equation, where the azimuth angle of the bottom cutting edge is φ0. This L corresponds to the length in the Z-axis direction from point A to point B in Figure 4.

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[0059] Next, we will explain the cutting region model. When the cutting starts from the bottom of the end mill, r0 = R in equation (2). w -d is expressed by the following formula.

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[0060] Divide the cutting edge of the end mill into n tiny cutting edges and calculate the point P i (i=0, 1, ..., n) in the cylindrical coordinate system (r i , φ i , z i ) Point P0 corresponds to point A in Figure 4, and point P n corresponds to point B in Figure 4. The length dz of one minute cutting edge in the Z direction is expressed by the following equation using equation (7):

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[0061] Radius R T Point P on the square end mill i+1 and point P i The relative positional relationship is expressed by the following equation:

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[0062] point P i Position r of the cutting edge Pi is expressed by the following equation:

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[0063] Since point P cuts point Q, which was cut an angle (2π+dφ) ago, the following equation is expressed.

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[0064] dφ=φ Q -φ Pi Therefore, from the second equation of equation (12), the following equation is expressed.

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[0065] The position of the cutting edge at point Q is expressed by the following equation:

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[0066] point P i The cutting thickness in the radial direction of h i is expressed by the following equation:

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[0067] In addition, z i < f, there is no cutting mark from the previous rotation, so the cutting edge position is the depth of cut, which is expressed by the following equation.

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[0068] (2. Outer diameter mill skiving) FIG. 21 is a diagram for explaining an analytical model of outer diameter mill skiving. Here, R T is the tool radius, and R w is the workpiece radius, and dθ T is the parting angle on the tool cutting edge, and dθ w is the parting angle of the workpiece surface, φ is the helix angle, and y o is the center of the end mill in the Y-axis direction.

[0069] 22 is a diagram for explaining an end mill model. In the coordinate system of the figure, the azimuth angle θ of the end mill is T The coordinates of the cutting edge relative to the

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[0070] Next, we will explain the time change of the cutting edge coordinates in the workpiece orthogonal coordinate system. The tool origin coordinates in the workpiece coordinate system at time t in the analysis model of Figure 21 are (0, y o , ft), the coordinates of the tool cutting edge are expressed by the following equation:

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[0071] However, y in Figure 21 o is a negative value. In the real model, the workpiece rotates, but in the analytical model, the workpiece is fixed and the end mill rotates at an angular velocity ω w In this case, the (x, y, z) of the cutting edge in the Cartesian coordinate system of the workpiece can be expressed by the following equation:

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[0072] The workpiece is cut when the following conditions are met:

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[0073] The analysis of cutting thickness will be explained. FIG. 23 is a diagram for explaining the azimuth angle of the workpiece. The cutting edge of the end mill is aligned in the axial direction (X axis) at a height x p The preceding cutting point Q is found for point P in the figure. Note that the Y axis (cutting axis) in Figure 23 is the X axis in Figure 5. The azimuth angle θ of point P T,P is expressed by the following equation from the first equation of equation (17):

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[0074] Therefore, referring to the end mill model in Figure 22, (y p , z p ) is expressed by the following formula:

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[0075] Azimuth angle θ of the workpiece relative to the cutting edge point Pi W,P is expressed by the following equation:

number

[0076] Consider the position of the leading cutting edge Q where point P is cutting. Point Q is below point P on the end mill cutting edge (X Q < X P ), and if the helix angle φ is positive, the Z direction is the feed direction (Z Q > Z P On the other hand, assuming point Q, the azimuth angle θ of the workpiece relative to point Q is calculated as in equations (20) to (22). W,Q is obtained.

[0077] The difference in azimuth angle between points P and Q is dθ W is expressed by the following equation:

number

[0078] If the feed per revolution is f, the cutting position at point Q is the angle (2p-dθ W Therefore, point Q is cut in the Z direction by the following equation: w We are ahead.

number

[0079] On the other hand, for point Q, ZT,Q Since we get dz w will satisfy the following equation:

number

[0080] Therefore, point Q is obtained by the following five steps. In step 1, the X coordinate of point P (x P ) and calculate the Y and Z coordinates using equations (21) and (22). In step 2, the X coordinate of point Q (x Q ) and calculate the Y and Z coordinates using equations (21) and (22). In step 3, the azimuth angle q on the workpiece is calculated using equation (22). W,P and q W,Q Calculate dθ using equations (24) and (25). W and dz w Ask for. In step 4, the z calculated in steps 1 and 2 is T,P and z T,Q From equation (26), dz w Ask for. In step 5, dz in steps 3 and 4 w The X coordinate of point Q (x Q ) assumption is repeated.

[0081] Radius R between points P and Q on the workpiece W,P and R W,Q is expressed by the following equation:

number

[0082] Therefore, the radial depth of cut d at point P p is expressed by the following equation:

number

[0083] In the analysis, the cutting edge of the end mill is divided into n small cutting edges, and the cutting edge element P i On the other hand, leading cutting edge Qi is determined, and the distribution of the cutting depth is calculated using equations (27) and (28).

[0084] The finishing surface analysis is explained. The workpiece is divided into minute elements in the circumferential and axial directions, and (r ij , θ ij , z ij ) is considered in the cylindrical coordinate system. In the analysis model, the tool is fixed and the workpiece is considered to move in the -Z direction at a feed rate of f. In other words, the following relationship is satisfied:

number

[0085] The coordinate system of the cutting edge in the model where the tool is fixed is given by the following equation.

number

[0086] The second equation in equation (29) and the third equation in equation (30) give the following equation:

number

[0087] The small element under consideration (r ij , θ ij , z ij ) interferes with the tool when the following formula is true:

number

[0088] At this time, the coordinates of the cutting edge on the XY plane are expressed by the following equation.

number

[0089] where θ T , i,j is expressed by the following equation from equation (31):

number

[0090] This (x T , i,j , y T , i,j ) is on a straight line connecting the center of the workpiece with a point on the circumference rotating at an angular velocity ω, and the workpiece is cut.

number

[0091] (Action and effect) As described above, according to this embodiment, skiving is performed using a portion of the cutting edge of the helical blade (other than both ends). Therefore, unlike a straight blade, it can be performed using two-axis control. In the case of two-axis control, it is necessary to control only the X-axis (cutting direction) and Z-axis (rotation axis), and it is not necessary to control the Y-axis (tangential direction). In this way, skiving is possible using two-axis control because the cutting depth of a portion of the cutting edge of the helical blade increases from the point where it bites into the workpiece to another point. Therefore, it is possible to provide a machining technology that enables skiving to be performed even on a general two-axis controlled lathe machine tool.

[0092] (Sixth embodiment) In the sixth embodiment, we will use the cutting of the outer peripheral surface of a workpiece as an example to explain how mill skiving produces less vibration than general cutting processes. Please note that the coordinate axes are set differently from those in the first to fifth embodiments in order to compare with general cutting processes. The workpiece material used is S45C steel with a diameter of 8.5 mm. The cutting conditions are a cutting speed of 35 m / min, a feed rate of 0.05 mm per revolution, a depth of cut of 0.4 mm, and no cutting fluid. The helix angle of the end mill 201 is 30°.

[0093] FIG. 24 is a diagram for explaining the components of cutting forces according to the sixth embodiment. Here, the cermet tool 400 for general turning explained in FIG. 15(a) is used as a general cutting tool (indicated as Turning). The workpiece W1 is held in the X-axis direction and can be rotated in the N-axis direction. The general cutting tool 400 performs cutting at a feed rate f in the X-axis direction to cut the outer peripheral surface of the workpiece W1. Each cutting force component has a principal component F z , thrust force F y , the feed force is F x The black arrow indicates the composition of the three component forces, which can be said to be the cutting force. General cutting tool 400 is a 16mm square steel bit with a carbide tip for finishing with a nose radius of 0.4mm.

[0094] FIG. 25 is a diagram illustrating skiving using a helical blade according to a sixth embodiment. FIG. 25(a) shows a state in which a chuck 310 of a machine tool holds a workpiece W1. The workpiece W1 has a round rod shape. As in FIG. 3, the entire machine tool is not shown, but the chuck 310 holds the workpiece W1 so that it can rotate around the X-axis. When the machine tool rotates the chuck 310, the workpiece W1 also rotates. In FIG. 25(a), the end mill 201 is hidden behind the workpiece W1, and is therefore represented by a dotted line. As described in FIG. 8, the end mill 201 is a commercially available two-blade product with a helix angle of 30° (labeled "Mill skiving").

[0095] Figure 25(b) is a cross-sectional view showing the end mill 201 cutting the outer diameter of the workpiece W1. The X-axis is the rotation axis of the workpiece W1, and it determines the feed rate of the end mill 201. The Z-axis is the cutting axis, and the end mill 201 is used to cut into the workpiece W1 from point A to point B. The Y-axis is a direction perpendicular to both the X-axis and Z-axis, and indicates the tangent direction to the cross-sectional circle of the workpiece W1. A typical lathe machine tool moves along only two axes, the X-axis and the Z-axis, but in the case of a multi-axis machine, the Y-axis is also used.

[0096] 26 is a graph of cutting force components according to a comparative example (Turning) of the sixth embodiment. Here, for each cutting force, X is the feed direction, Y is the axial direction of the tool, and Z is the positive downward direction. In the case of general cutting, the principal component of force F z is the feed force F x and back force F y It can be seen that this is larger than the above and causes the workpiece W1 to vibrate (or bend) significantly in the cutting axis direction Z.

[0097] Fig. 27 is a graph of cutting force components according to the sixth embodiment (mill skiving with a helix angle of 30°). Here, for each cutting force, X is the feed direction, Y is the tool axial direction, and Z is the downward direction, which are positive. X and Y are negative values ​​for the force applied to the tool (end mill), and the feed force F x and back force F y In addition, as the cutting depth increases, the principal force F z It can be seen that

[0098] In the case of mill skiving, unlike general cutting processes, it can be seen that the principal force (Z direction) is smaller than the feed force (X direction) and the thrust force (Y direction).

[0099] 28 is a diagram for explaining the cutting depth and cutting force components according to the sixth embodiment (Mill skiving). In the case of mill skiving, when the cutting depth (also called the cutting depth) is increased, the feed force (X direction) and thrust force (Y direction) also increase. However, the principal force (Z direction) remains approximately the same magnitude.

[0100] 29 is a diagram for explaining the cutting depth and cutting force components in a comparative example (Turning) of the sixth embodiment. In the case of general cutting, when the cutting depth is increased, the feed force (X direction), thrust force (Y direction), and principal force (Z direction) all increase. In particular, the principal force (Z direction) becomes the largest.

[0101] Thus, the principal force (Z direction) in Figure 28 (Mill skiving) differs from the principal force (Z direction) in Figure 29 (Turning) in that even if the cutting depth is increased, the principal force (Z direction) remains approximately the same magnitude, and vibration toward the center of the rotation axis of the workpiece W1 can be suppressed.

[0102] 30 is a diagram illustrating the finished surface and surface shape according to the sixth embodiment (mill skiving). The roughness of the finished surface was measured using a laser confocal microscope (KEYENCE VX-X100). The surface roughness was found to be Ra (arithmetic mean roughness) of 0.881 μm and Rz (maximum height) of 9.840 μm.

[0103] 31 is a diagram for explaining the finished surface and surface shape according to a comparative example (Turning) of the sixth embodiment. The surface roughness is Ra (arithmetic mean roughness) of 4.097 μm and Rz (maximum height) of 27.33 μm.

[0104] As can be seen, the surface of Figure 30 (Mill skiving) has a much better finished surface than the surface of Figure 31 (Turning).

[0105] Figure 32 is a diagram illustrating residual stresses according to the sixth embodiment. Here, residual stress in the axial direction of the finished surface was measured using a residual stress measuring instrument (PULSREC μ-X360n). This figure compares residual stresses in mill skiving and conventional turning. In conventional turning, tensile stress occurs at the tip of the cutting edge, separating the chip from the finished surface. Therefore, as shown in this figure, tensile residual stress is likely to occur on the surface. On the other hand, in mill skiving, the depth of cut is gradually increased with the rotation of the workpiece and the feed of the tool, resulting in a smaller depth of cut on the final finished surface. As a result, the cutting edge's pushing force is relatively greater than the chip-forming force. Furthermore, when the depth of cut falls below the minimum chip thickness, no chips are generated, and the cutting edge acts to smooth the finished surface. As a result, the residual stress in the surface layer becomes compressive.

[0106] (Seventh embodiment) In the seventh embodiment, we will use the cutting of the end face of a workpiece as an example to explain how mill skiving can produce a better finished surface than general cutting. The workpiece is made of S45C steel with a diameter of 35 mm. The cutting conditions are a cutting speed of 35 m / min, a feed rate of 0.1 mm per revolution, and a depth of cut of 0.2 mm for turning and 0.1 mm for mill skiving. The end face of the workpiece is cut from the large diameter side to the center.

[0107] 33 is a diagram for explaining end surface cutting according to a comparative example to the seventh embodiment. Here, as in the sixth embodiment, a cermet tool 400 for general turning is used as a general cutting tool (indicated as "Turning"). A chuck 310 of a machine tool rotatably holds a workpiece W1, and the general cutting tool 400 cuts an end surface ES of the workpiece W1.

[0108] 34 is a diagram for explaining end face cutting according to the seventh embodiment of the present invention. As in the sixth embodiment, an end mill 201 is used as a mill skiving tool (denoted as Mill skiving). A chuck 310 of the machine tool rotatably holds a workpiece W1, and the end mill 201 cuts the end face ES of the workpiece W1.

[0109] 35 is a diagram illustrating the finished surface and surface shape according to the seventh embodiment (mill skiving). The roughness of the finished surface was measured using a laser confocal microscope (KEYENCE VX-X100). The surface roughness was found to be Ra (arithmetic mean roughness) of 0.452 μm and Rz (maximum height) of 4.824 μm.

[0110] 36 is a diagram for explaining the finished surface and surface shape according to a comparative example (Turning) of the seventh embodiment. The surface roughness is Ra (arithmetic mean roughness) of 0.918 μm and Rz (maximum height) of 7.63 μm.

[0111] As can be seen, the surface of Figure 35 (Mill skiving) has a much better finished surface than the surface of Figure 36 (Turning).

[0112] Figure 37 is a diagram illustrating residual stresses according to the seventh embodiment. Here, residual stress in the axial direction of the finished surface was measured using a residual stress measuring instrument (PULSREC μ-X360n). This figure compares residual stresses in mill skiving and conventional turning. Unlike the sixth embodiment (peripheral surface machining), conventional turning separates the chips from the finished surface without generating tensile stress at the cutting edge. Therefore, as shown in this result, slight compressive residual stresses tend to occur on the surface. On the other hand, in mill skiving, the depth of cut is gradually increased with the rotation of the workpiece and the feed of the tool, resulting in a smaller depth of cut on the final finished surface. As a result, the pushing force of the cutting edge becomes greater than the chip-forming force. Furthermore, when the depth of cut is less than the minimum chip thickness, no chips are generated, and the cutting edge acts to smooth the finished surface. As a result, large compressive residual stresses occur in the surface layer.

[0113] Please note that because regular skiving uses a straight blade, unlike a helical blade, it is not possible to cut the end face of the workpiece from the large diameter side to the center. In other words, even if the workpiece is sufficiently thin, using a straight blade will only result in a thin cut at the end face.

[0114] Although the embodiments of the present invention have been described above, two or more of these examples may be combined and implemented, or one of these examples may be partially implemented.

[0115] Furthermore, the present invention is not limited to the above-described embodiments of the invention, and various modifications within the scope of the claims and within the scope that can be easily conceived by a person skilled in the art are also included in the present invention. [Explanation of symbols]

[0116] 100, 101, 102, 103 cutting tools 110, 110', 111, 112, 113, 114 Twisted blade 120, 121 shank 130, 131 Clamp 140, 141 screws 200, 201 End Mill 210, 211 End cutting groove 220, 221 Bottom blade 230, 231 Flute 300 Machine tools 310 Chuck 320, 321 Tool holder 400 General turning tools W1, W2 work

Claims

1. A skiving tool having a twisted blade used for skiving, The cutting edge of the helical blade is twisted in the cutting direction of the skiving process, A skiving tool characterized in that the cutting edge of the helical blade has different azimuth angles at a first point and a second point in the cutting direction.

2. The skiving tool according to claim 1 , which is integral with the helical blade.

3. The skiving tool according to claim 1, wherein the helix angle of the helical blade is between 15° and 50°.

4. The skiving tool according to claim 3, wherein the helix angle of the helical blade is 30°.

5. The skiving tool according to claim 1, wherein the helical blade is manufactured by cutting a portion of an end mill.

6. A skiving tool as described in claim 5, wherein when the twisted blade is formed by cutting the tip of the end mill, one end of the peripheral blade of the tip on the bottom blade side of the tip is used for the skiving.

7. The skiving tool according to claim 5, wherein the end mill has three blades.

8. The skiving tool according to claim 5, wherein the end mill has two blades.

9. The skiving tool according to claim 1, wherein the helical blade is an outer diameter throw-away tip.

10. The skiving tool according to claim 1, wherein the helical blade is an internal diameter throw-away tip.

11. The skiving tool according to claim 1, wherein the helical blade performs skiving on the end surface of the workpiece.

12. a chuck for rotatably holding the workpiece on the first axis; A tool rest for mounting a skiving tool having a twisted blade used for skiving, a feed amount of the twist blade is set in the first axial direction; A skiving processing device using a machine tool that sets the cutting amount of the twist blade to a second axis perpendicular to the first axis direction, A skiving device characterized in that the cutting edge of the helical blade is twisted in the cutting direction of the skiving.

13. a chuck for rotatably holding the workpiece on the first axis; A skiving method using a machine tool including a tool rest to which a skiving tool having a twisted blade used for skiving is attached, The workpiece is fixed to the chuck; Rotating the chuck; Aligning the skiving tool with a first axis; a feed amount of the twist blade is set in the first axial direction; The cutting amount of the twisted blade is set to a second axis perpendicular to the first axial direction, so that the skiving tool performs the skiving process, A skiving method, characterized in that the cutting edge of the helical blade is twisted in the cutting direction of the skiving.

Images