Skiving tool, skiving device, and skiving method

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] SUMMARY OF THE DISCLOSURE Embodiments of the present invention relate to skiving tools, apparatus and methods. [Background technology]

[0002] As a method for cutting the rotationally symmetric surface of a rotating workpiece (object to be machined), a skiving method is known in which a cutting edge (straight blade) arranged at an angle to the rotation axis of the workpiece is introduced while being in contact with the rotating workpiece in a linear feed motion that crosses the rotation axis. When cutting a workpiece with this method, the inclination angle of the straight blade with respect to the rotation axis is set in the range of more 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 X-axis. On the other hand, a typical lathe machine performs cutting using two-axis control. In other words, there is no Y-axis direction, and cutting is performed by the feed amount in the Z-axis direction and the cutting depth in the X-axis direction.

[0006] The present invention was developed through extensive research with a focus on these problems, and its purpose is to provide a machining technique 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 problems, 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 to which a skiving tool having a twisted blade is attached, the feed amount of the twisted blade being set in the first axial direction and the cutting amount of the twisted 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 twisted 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 on which a skiving tool having a twist blade is attached, the skiving method comprising the steps of fixing the workpiece to the chuck, rotating the chuck, aligning the skiving tool with the first axis, setting the feed amount of the twist blade in the first axial direction, and setting the cutting depth of the twist blade in a second axis perpendicular to the first axial direction. Effect 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 description of the drawings]

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

[0012] An embodiment of the present invention will be described with reference to the drawings. Here, the same reference numerals are used for common parts in each drawing, and duplicated explanations will be omitted. The coordinate axes are the Z-axis direction in which the rotation axis of the work extends, the X-axis direction in which the cutting tool cuts into the work, and the Y-axis direction in which the tangential direction perpendicular to both the Z-axis and the X-axis is.

[0013] A typical lathe machine 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 cutting depth 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 blade 110, a shank 120 that holds the twisted blade 110, a clamp 130 that fixes the twisted blade 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 blade 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 twist 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 twist blade 110 cuts the outer diameter of the workpiece between point A and point B. For this reason, the twist blade 110 is also called an outer diameter throw-away tip. In addition, the three twist blade tips of the twist blade 110 can be used by loosening the screw 140 and rotating the twist blade 110 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 manner, the radial cutting depth of the workpiece can be controlled, for example, between 0.05 mm and 0.1 mm.

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

[0018] The twisted blade 110 in FIG. 2A can be manufactured by cutting off a portion (indicated by a two-dot chain line) about 5 mm from the tip of the cutting edge of the end mill 200 in FIG. 2B. The chips cut by the twisted blade 110 are discharged along the flutes 230. The portion 210 surrounded by the dotted line is the clearance groove of the bottom 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 in FIG. 2B, 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 clearance groove of the bottom cutting edge of the end mill 200.

[0019] FIG. 3 is a diagram for explaining skiving using a twisted blade according to the first embodiment of the present invention. FIG. 3(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. 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] FIG. 2B is a cross-sectional view showing the state in which the twist blade 110 cuts the outer diameter of the workpiece W1. The Z-axis is the rotation axis of the workpiece W1, and the feed amount of the twist blade 110 can be determined. The X-axis is the cutting axis, and the twist blade 110 is used from point A to point B to cut into the workpiece W1. The Y-axis is a direction perpendicular to both the Z-axis and the X-axis, and indicates the tangent direction of the cross-sectional circle of the workpiece W1. A typical lathe machine tool moves on only two axes, the Z-axis and the X-axis, but in the case of a multi-tasking machine, the Y-axis is also used.

[0021] FIG. 4 is an enlarged view of a portion of FIG. 3, enlarging the area surrounded by the two-dot chain line in FIG. 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 becomes possible to perform outer diameter cutting with a cutting depth of 0.05 mm to 0.1 mm. The cutting depth can also be said to be the cutting depth toward the center of the Z axis.

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

[0023] FIG. 5 is a diagram for explaining the contact area of ​​the blade according to the degree of twist of the twist 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 the rotating workpiece W1 without cutting the tip of the end mill 200. The end mill 200 is not rotating, but is only moving in the direction of the rotation axis Z of the workpiece W1 at a predetermined feed amount. Here, the part of the twist blade of the end mill 200 used for cutting the outer diameter is only the part surrounded by the two-dot chain line. This part surrounded by the two-dot chain line corresponds to the twist blade 110. In addition, the end mill 200 is composed of three twist blades, but there is no particular limit to the number of twist blades, and it is sufficient if a part of the twist blade at the tip of the end mill 200 can cut into the outer diameter of the workpiece W1.

[0024] Fig. 1B shows the cutting portion AB of the twisted blade 110-1 when the twist angle is 20°. Fig. 1C 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. The length of the cutting portion AB when the twist angle is weak (20° in Fig. 1B) is longer than the length of the cutting portion AB when the twist angle is strong (45° in Fig. 1C).

[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 considering or calculating the length of the cutting portion of the twist blade 110. Here, the twist angle of the twist blade is preferably set 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 the workpiece W1 can rotate around the Z-axis. The cutting tool 100 has a twisted blade 110, which is a cut-off tip of an end mill, attached to a shank 120. The shank 120 is attached to a tool rest 320 of the machine tool 300 from bottom to top (in the X direction).

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

[0028] FIG. 1B 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 rest 321 from left to right (Z direction). As in FIG. 1A, 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. By attaching the end mill 200 to a three-axis controlled machine tool 300 (e.g., a machining center or a multi-tasking machine) in this way, it is possible to provide a skiving device.

[0029] In Fig. 2(a), a twisted blade with the tip of an end mill cut off is attached to a machine tool 300, and in Fig. 2(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 case of Fig. 6(a) will be described. The workpiece W1 is fixed to the chuck 310 of the machine tool 300 (S1). The chuck 310 is rotated by a predetermined amount of rotation (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 cutting depth is set (S5).

[0031] 6(a) shows a two-axis controlled machine tool, so it is necessary to align the cutting tool 100 in the Y direction beforehand, before aligning the Z direction of S3. The cutting feed amount of S4 is set per rotation in the Z direction, and further, the start point and end point in the Z direction are set. The cutting amount of 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 a two-axis controlled machine tool but also to a three-axis controlled machining center. In this case, the cutting depth of S5 can be set as the cutting depth in either the X-direction or the 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 8 is a diagram for explaining a method for manufacturing a twisted 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 twist angle is generally 30°. The diameter of the end mill is 8 to 10 mm.

[0034] By cutting off about 5 mm of the tip of the end mill 201 in Fig. 2(b) (shown by a two-dot chain line), the twisted blade 111 in Fig. 2(a) can be manufactured. The portion 211 surrounded by the dotted line is the clearance groove of 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 twist blade 112 for cutting the outer diameter of a cylindrical workpiece, a shank 120 for holding the twist blade 112, a clamp 131 for fixing the twist 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 one blade and is hollow in the center. Therefore, the tip pin of the clamp 131 is longer than that in FIG 1 and reaches the shank 120 to fix the twisted blade 112 to the shank 120.

[0037] 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 with a thickness of about 5 mm, hollowing out the central portion, and removing the two-dot chain line portion by cutting and grinding. The twisted blade 112 has a 45° twist angle. As explained in FIG. 4, points A and B are the cutting start point and the point where the cutting reaches the finishing surface. The twisted blade 112 can also be called an outer diameter throw-away tip.

[0038] (Fourth embodiment) 11 is a diagram for explaining 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 twist blade 113 for cutting the inner diameter of a cylindrical workpiece, a shank 121 for holding the twist blade 113, and a screw 141 for fixing the twist blade 113 directly (without a clamp) to the shank 121.

[0039] The difference between Fig. 11(a) and Fig. 9 is that a female thread is cut in the center of the twist blade 113, and further, a female thread is cut in the part of the shank 121 where the twist blade 113 is fixed. Then, the twist blade 113 is fixed to the shank 121 by tightening a male screw 141. Fig. 11(b) is a cross-sectional view of a cylindrical workpiece W2. It shows the state where the cylindrical workpiece W2 is inserted into the cutting tool 102 and the twist blade 113 cuts the inner diameter of the workpiece W2.

[0040] Fig. 12 is a diagram for explaining a twisted blade according to a fourth embodiment of the present invention. Fig. 12(a) is a diagram of the twisted blade 113 as viewed from the arrow line A in Fig. 11(a). The twisted blade 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 part indicated by the two-dot chain line on the outside of the twisted blade 113 by cutting and grinding, in the same manner as described in Fig. 10.

[0041] FIG. 12(b) is a view of the twisted blade 113 seen from the arrow line B in FIG. 11(a). As explained in FIG. 4, points A and B are the incision start point and the point where the finished surface is reached while incising. The twisted blade 113 has a thickness of 4 mm and a twist angle of 30°. The twisted blade 113 can also be called an inner diameter throw-away tip. As in the first embodiment, the twisted blade for cutting the inner diameter of the cylindrical workpiece may be the tip of an end mill or the entire end mill. FIG. 13 is a diagram for explaining 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 a state in which the cylindrical workpiece W2 is inserted into the end mill 200 and the twisted blade 110 cuts the inner diameter of the workpiece W2.

[0042] Fifth embodiment FIG. 14 is a diagram for explaining 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 composed of an end mill. FIG. 14(a) omits the shank portion of the end mill and shows a body portion with a twisted blade 114 on the outer peripheral side surface. The chips cut by the twisted blade 114 are discharged along a flute 231. In addition, a bottom blade 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 surface of a cylindrical workpiece (labeled Workpiece). In this, the helical blade 114 makes a cut into the inner surface of the workpiece and feeds it in the longitudinal direction, removing the cutting area (labeled Removal area). Since the helical blade 114 has a helix angle, the helical blade 114 bites into the processing surface at point A, and continuously makes a cut in the radial direction of the workpiece toward the right in FIG. 14(a), reaching a predetermined amount 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 is 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 described below, a good finished surface is obtained, and the residual stress also tends to be compressive.

[0045] On the other hand, the chips are discharged along the flutes of the end mill. In general, 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 chips are guided by the flutes and discharged out of the hole, so that scraping of the chips against the finished surface is suppressed.

[0046] Fig. 15 is a diagram for explaining the components of cutting force according to the fifth embodiment of the present invention. Fig. 15 explains the cutting force components when cutting the inner circumferential surface of the cylindrical workpiece explained in Fig. 14. Fig. 15(a) shows the vector components of the cutting force when a general turning cermet tool (Kyocera TN620) 400 is used (shown as "Turning"), and Fig. 15(b) shows the vector components of the cutting force when a 10 mm diameter two-blade end mill (UNION TOOL CSS2100-1500, helix angle 30°) 103 is used (shown as "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 cutting speed 150 m / min, feed rate 0.1 mm / rev, radial depth of cut 0.05 mm, and dry cutting.

[0049] In the case of the general turning tool 400 in FIG. 1(a), the normal line of the main cutting edge is inclined to the feed direction, so the feed force F x On the other hand, since the normal line of 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 FIG. x The Y component in the figure is shown as a negative value based on the direction of the measured cutting force component.

[0050] Fig. 16 is a diagram for explaining the components of cutting force according to the helix angle according to 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 on cutting becomes long. Therefore, the cutting force is large at a helix angle of 25°.

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

[0052] FIG. 18 is a diagram for explaining the surface roughness according to the fifth embodiment of the present invention. The figure compares the surface roughness in each cutting test of the end mill 103 with a helix angle of 25°, 30°, or 40° and a general turning tool 400 (Turning). FIG. 18(a) shows Ra (arithmetic mean roughness). FIG. 18(b) shows Rz (maximum height roughness). According to formula (1), the smaller the helix angle γ in mill skiving, the larger the cutting edge length L becomes, and the more rotations the workpiece has until the set cutting depth is reached. Therefore, at a helix angle of 25°, the cutting depth given per one rotation of the workpiece becomes smaller. This improves the finished surface.

[0053] FIG. 19 is a diagram for explaining residual stress according to the fifth embodiment of the present invention. Here, the residual stress in the axial direction and circumferential direction of the finished surface was measured by a residual stress measuring device (PULSREC μ-X360n). The figure compares the residual stress in mill skiving with a helix angle of 30° and turning. In turning, tensile stress is generated at the tip of the cutting edge, and the chips and the finished surface are separated. Therefore, as shown in this result, tensile residual stress is likely to occur on the surface. On the other hand, in mill skiving, the cutting depth is gradually given with the rotation of the workpiece and the feed of the tool, and the cutting depth of the final finished surface becomes smaller. As a result, the pushing force of the cutting edge becomes larger than the chip generation force. Also, when the cutting depth becomes less than the minimum cutting thickness, no chips are generated, and the cutting edge acts to push the finished surface. As a result, the residual stress in the surface layer becomes compressive.

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

[0055] (1. Internal diameter mill skiving) FIG. 20 is a diagram for explaining an analytical model of internal mill skiving. FIG. 20(a) shows the geometric relationships when an end mill (indicated as Tool) cuts the internal diameter of a cylindrical workpiece (indicated as Workpiece). FIG. 20(b) is an enlarged view of a portion of FIG. 20(a). FIG. 20(c) is a list of symbols showing the geometric relationships. FIG. 20(d) is a diagram for supplementary explanation of the geometric relationships. Note that when the radius R of the cylindrical workpiece (material to be cut) 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. An arbitrary point P on the cutting edge of the end mill 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, assuming that 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, the cutting region model will be explained. When the end mill starts cutting from the bottom position, r0 = R 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 Fig. 4. The length dz of one small 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 of the cutting edge at r Pi is expressed by the following equation.

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[0063] Since point P cuts off 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. External diameter mill skiving) FIG. 21 is a diagram for explaining an analysis model of the outer diameter mill skiving process. Here, R T is the tool radius, R w is the radius of the workpiece, 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 end mill center in the Y-axis direction.

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

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[0070] Next, we will explain the change in the cutting edge coordinates in the workpiece Cartesian coordinate system over time. The tool origin coordinates in the workpiece coordinate system at time t in the analysis model of FIG. 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, in Figure 21, y 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 is 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 the cutting thickness will be described. 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 obtained 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 From the first equation of equation (17), it is expressed by the following equation.

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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:

number

[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 that is cut by point P. On the end mill cutting edge, point Q is lower than point P (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 from equation (20) in the same way as equation (22). W,Q is obtained.

[0077] The difference in azimuth 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 of point Q is the angle (2p-dθ W Therefore, point Q is cut in the Z direction by the following formula: dz w We are ahead of the curve.

number

[0079] On the other hand, for point Q, ZT,Q Therefore, dz w satisfies the following equation:

number

[0080] Therefore, we obtain point Q by following the five steps below. 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 andq W,Q Calculate dθ using equations (24) and (25). W anddz w Request. In step 4, the z calculated in steps 1 and 2 is T,P and z T,Q From equation (26), dz w Request. 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 Meanwhile, 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 In the analysis model, the tool is fixed and the workpiece is assumed 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 with the tool fixed is given by the following equation.

number

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

number

[0087] The small element of interest (r ij , θ ij , z ij ) interferes with the tool when:

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 From equation (31), it is expressed as follows.

number

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

number

[0091] (Action and effect) As described above, according to this embodiment, skiving is performed using a portion (other than both ends) of the cutting edge of the twisted blade. Therefore, unlike a straight blade, it may be performed with 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, since the cutting depth of a portion of the cutting edge of the twisted blade increases from the biting point into the workpiece to another point, skiving becomes possible with two-axis control. Therefore, it is possible to provide a machining technology that enables skiving to be performed even with a general two-axis controlled lathe machine tool.

[0092] Sixth embodiment In the sixth embodiment, the mill skiving process produces less vibration than general cutting processes, taking the cutting of the outer peripheral surface of a workpiece as an example. 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 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 cutting depth of 0.4 mm, and no cutting oil. The twist 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 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 force F z , thrust force is F y , the feed force is F x The black arrows indicate the composition of the three component forces, which can be said to be the cutting force. The general cutting tool 400 is a 16 mm square steel bit with a carbide tip for finishing with a nose radius of 0.4 mm.

[0094] FIG. 25 is a diagram for explaining the skiving process using a twisted blade according to the sixth embodiment. FIG. 25(a) shows a state in which the chuck 310 of the machine tool holds the workpiece W1. The workpiece W1 has a round bar 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. Then, the machine tool rotates the chuck 310, so the workpiece W1 also rotates. In FIG. 25(a), the end mill 201 is hidden behind the workpiece W1, so it is shown by a dotted line. As explained in FIG. 8, the end mill 201 is a commercially available product with two blades and a twist angle of 30° (shown as Mill skiving).

[0095] Fig. 25(b) is a cross-sectional view showing the state in which the end mill 201 cuts the outer diameter of the workpiece W1. The X-axis is the rotation axis of the workpiece W1, and the feed amount of the end mill 201 can be determined. The Z-axis is the cutting axis, and the end mill 201 is used from point A to point B to cut into the workpiece W1. The Y-axis is a direction perpendicular to both the X-axis and the Z-axis, and indicates the tangent direction of the cross-sectional circle of the workpiece W1. A typical lathe machine tool moves on 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 the cutting force components according to a comparative example (Turning) of the sixth embodiment. Here, each cutting force is positive in the feed direction, Y in the axial direction of the tool, and Z in the downward direction. In the case of general cutting, the principal 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 the 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 axial direction of the tool, and Z is the positive downward direction. X and Y are negative values ​​for the force applied to the tool (end mill), and the feed force component F x and back force F y In addition, as the cutting depth increases, the principal force F z It can be seen that the following is occurring.

[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 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 almost the same.

[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) is different from the principal force (Z direction) in Figure 29 (Turning). 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 for explaining 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 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 finish than the surface of Figure 31 (Turning).

[0105] FIG. 32 is a diagram for explaining the residual stress according to the sixth embodiment. Here, the residual stress in the axial direction of the finished surface was measured using a residual stress measuring device (PULSREC μ-X360n). The figure compares the residual stress in mill skiving and general turning. In general turning, tensile stress occurs at the tip of the cutting edge, and the chips and the finished surface are separated. Therefore, as shown in this result, tensile residual stress is likely to occur on the surface. On the other hand, in mill skiving, the cutting depth is gradually given with the rotation of the workpiece and the feed of the tool, and the cutting depth of the final finished surface becomes smaller. As a result, the pushing force of the cutting edge becomes larger than the chip generation force. Also, when the cutting depth becomes less than the minimum cutting thickness, no chips are generated, and the cutting edge acts to push the finished surface. As a result, the residual stress in the surface layer becomes compressive.

[0106] Seventh embodiment In the seventh embodiment, the mill skiving process can obtain a better finished surface than general cutting processes, taking the cutting of the end face of a workpiece as an example. The workpiece is S45C 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, a depth of cut of 0.2 mm for turning and 0.1 mm for mill skiving, and cutting is performed on the end face from the large diameter side to the center of the workpiece.

[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 (shown 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 (shown as Mill skiving). A chuck 310 of a machine tool rotatably holds a workpiece W1, and the end mill 201 cuts an end face ES of the workpiece W1.

[0109] 35 is a diagram for explaining 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 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 in Figure 35 (Mill skiving) has a much better finished surface than the surface in Figure 36 (Turning).

[0112] FIG. 37 is a diagram for explaining the residual stress according to the seventh embodiment. Here, the residual stress in the axial direction of the finished surface was measured by a residual stress measuring device (PULSREC μ-X360n). The figure compares the residual stress in mill skiving and general turning. In general turning, unlike the sixth embodiment (peripheral surface machining), tensile stress is not generated at the tip of the cutting edge, and the chips and the finished surface are separated. Therefore, as shown in this result, slight compressive residual stress is likely to occur on the surface. On the other hand, in mill skiving, the cutting depth is gradually given with the rotation of the workpiece and the feed of the tool, and the cutting depth of the final finished surface becomes smaller. As a result, the pushing force of the cutting edge becomes larger than the chip generation force. Also, when the cutting depth becomes less than the minimum cutting thickness, no chips are generated, and the cutting edge acts to push the finished surface. As a result, compressive residual stress is generated significantly in the surface layer.

[0113] Please note that because normal skiving uses a straight blade, unlike a twisted 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, if a straight blade is used, it will only cut the end face thinly.

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

[0115] Furthermore, the present invention is not limited to the above-mentioned embodiment 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, A skiving tool that performs skiving without using both ends of the cutting edge of the twisted blade.

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

3. The skiving tool according to claim 2, wherein the helix angle of the helical blade is 30°.

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

5. A skiving tool as described in claim 4, wherein when the twisted blade is a cut-off 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.

6. The skiving tool according to claim 4, wherein the end mill has three blades.

7. The skiving tool according to claim 4, wherein the end mill has two blades.

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

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

10. The skiving tool according to claim 1 , wherein the twisted blade performs skiving on an end surface of a workpiece.

11. A chuck that rotatably holds a workpiece on a first axis; A tool rest for mounting a skiving tool having a twisted blade, A feed amount of the twist blade is set in the first axial direction; A skiving processing apparatus using a machine tool that sets the cutting amount of the twist blade to a second axis perpendicular to the first axial direction, The skiving tool is a skiving device that performs skiving without using both ends of the cutting edge of the twisted blade.

12. A chuck that rotatably holds a workpiece on a first axis; A skiving method using a machine tool including a tool rest for mounting a skiving tool having a twisted blade, 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; A skiving method in which the cutting depth of the twisted blade is set to a second axis perpendicular to the first axial direction.

Images