Cutting tools

Abstract

To provide a cutting tool that can stabilize an outflow direction of chips.SOLUTION: A cutting tool 10 is moved by a processing / feeding amount relatively with respect to an object W to be cut to lathe-turn the object to be cut. The cutting tool 10 comprises a holder part 20 and a chip part 30 fixed to the holder part 20. The chip part 30 includes a rake face 31 formed on one surface, a flank face 32 leading to the rake face 31, a blade ridge-line part 33 positioned between the rake face 31 and the flank face 32, and a guide groove 34 that guides chips flowing out from the blade ridge-line part 33 to the rake face 31. A groove depth of the guide groove 34 is set to be in a range from a first reference value which is equal to a half of a groove depth of the guide groove 34 or more and is equal to a half of a cut-out thickness to a second reference value determined by adding the first reference value to the cut-out thickness.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a cutting tool that turns a workpiece by moving relative to the workpiece at a predetermined processing feed amount. [Background technology]

[0002] BACKGROUND ART Conventionally, a throw-away insert provided with an arc-shaped guide groove for guiding chips flowing from the cutting edge to the rake face has been known as a cutting tool (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-212704 Summary of the Invention [Problem to be solved by the invention]

[0004] The cutting tool described in Patent Document 1 has a shallow groove shape in which the groove depth of the guide groove is 1 / 5 or less of the groove width of the guide groove. When the guide groove has a shallow groove shape like this, the thickness of the chips at the start of cutting the workpiece is thin, and the direction of chip flow is unstable. Unstable chip flow is undesirable because it can lead to chips remaining on the workpiece and an increase in the amount of chips accumulating in the equipment.

[0005] An object of the present disclosure is to provide a cutting tool that can stabilize the direction in which chips flow. [Means for solving the problem]

[0008] Claim 1 The invention described in A cutting tool that turns a workpiece (W) by moving it relative to the workpiece (W) at a predetermined processing feed amount, Holder part (20) and a tip portion (30) fixed to the holder portion, The tip part is A rake face (31) provided on one side; a flank (32) connected to the rake face; a cutting edge portion (33) located between the rake face and the flank face; a guide groove (34) for guiding chips flowing from the cutting edge portion to the rake face, The groove depth of the guide groove is equal to or greater than half of the groove width of the guide groove, The scooping surface is A convex portion corresponding to the shape of the guide groove is formed on the chip, and the chip is curved corresponding to the shape of the rake face. In a direction perpendicular to the extending direction of the guide groove The surface has a convex shape that protrudes upward as it approaches the guide groove.

[0009] In this way, if the guide groove is deep, the rigidity of the chips can be ensured. In addition, if the rake face is curved in a direction perpendicular to the extension direction of the guide groove, the cross-sectional shape of the chips will be curved to match the shape of the rake face. As a result, the rigidity of the chips is improved and chip curling is suppressed, thereby stabilizing the direction of chip outflow.

[0014] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a cutting tool and a workpiece according to a first embodiment. FIG. [Figure 2] FIG. 2 is a schematic side view of a cutting tool. [Figure 3] FIG. 4 is an explanatory diagram for explaining a guide groove. [Figure 4] FIG. 10 is an explanatory diagram for explaining the difficulty of bending chips. [Figure 5] 10 is an explanatory diagram for explaining the relationship between the groove depth and groove width of a guide groove and the minimum curl diameter of chips. FIG. [Figure 6] FIG. 10 is an explanatory diagram for explaining the second moment of area of ​​chips cut by a cutting tool without a guide groove. [Figure 7] FIG. 10 is an explanatory diagram for explaining the second moment of area of ​​chips cut by a cutting tool with a guide groove. [Figure 8] 10 is an explanatory diagram for explaining uncut portions of a workpiece caused by providing a guide groove. FIG. [Figure 9] FIG. 10 is a schematic perspective view of a cutting tool according to a second embodiment. [Figure 10] FIG. 10 is an explanatory diagram for explaining chips produced by the cutting tool of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same as or equivalent to those described in the preceding embodiments will be given the same reference numerals, and their description may be omitted. Furthermore, in the embodiments, when only some of the components are described, the components described in the preceding embodiments can be applied to the remaining components. The following embodiments can be partially combined with each other, even if not specifically stated, as long as there is no particular problem with the combination.

[0017] (First embodiment) This embodiment will be described with reference to FIGS. 1 to 8. The cutting tool 10 shown in FIG. 1 is a tool that turns the workpiece W by moving it relative to the workpiece W at a predetermined processing feed rate. FIG. 1 illustrates an example in which the workpiece W is an object having a substantially cylindrical shape, and the outer periphery of the workpiece W is turned by the cutting tool 10. Note that FIG. 1 illustrates an example in which a groove is formed on the outer periphery of the workpiece W by cut-off processing, but other processing modes may also be used. Furthermore, the workpiece W is not limited to an object having a substantially cylindrical shape, and may be an object having a shape other than a substantially cylindrical shape.

[0018] Although not shown, the cutting tool 10 is attached to a tool table of a processing device. The processing device includes a spindle that rotates while holding the workpiece W, a tool table that is movable in two mutually perpendicular axial directions, and a feed mechanism that moves the tool table in the axial direction of the spindle at a predetermined processing feed amount.

[0019] 2, cutting tool 10 includes a holder portion 20 fixed to a tool table and a tip portion 30 fixed to holder portion 20. Cutting tool 10 may be configured such that holder portion 20 and tip portion 30 are integrally formed as a complete tool bit, or tip portion 30 may be configured as a separate, replaceable piece.

[0020] The tip portion 30 has a rake face 31 provided on one surface, a flank face 32 connected to the rake face 31, a cutting edge portion 33 located between the rake face 31 and the flank face 32, and a guide groove 34 for guiding chips CH flowing from the cutting edge portion 33 to the rake face 31.

[0021] The tip portion 30 has a cutting edge 331 provided on the cutting ridge portion 33. The cutting edge 331 is entirely rounded. In other words, the cutting edge 331 has an R-shape. The tip portion 30 is not limited to having one cutting edge 331, and may have multiple cutting edges 331.

[0022] The rake face 31 of the tip portion 30 is flat. One guide groove 34 is formed on the rake face 31. The guide groove 34 extends linearly from the tip 331a, which is the apex of the cutting edge 331, in a direction away from the cutting edge ridge 33. The guide groove 34 has a groove depth Gd, which is the distance from the rake face 31 to the bottom 341 of the guide groove 34, that is, a substantially constant groove depth. In this case, the groove depth Gd may be interpreted as a maximum value, a minimum value, or an average value. The guide groove 34 may be shaped so that the distance to the bottom 341 of the guide groove 34 gradually decreases with increasing distance from the tip 331a until it reaches the rake face 31. In this case, the groove depth Gd can be interpreted as the maximum distance from the rake face 31 to the bottom 341 of the guide groove 34 in the portion that affects the chip CH. In addition, multiple guide grooves 34 may be formed on the rake face 31.

[0023] 3, during machining of the workpiece W, the guide groove 34 is a groove that allows a portion of the chips CH to enter and guides the chips CH in the extending direction of the guide groove 34. By allowing a portion of the chips CH to enter the guide groove 34, deformation in the width direction of the guide groove 34 (i.e., lateral curl) is suppressed. In addition, a protrusion BP corresponding to the shape of the guide groove 34 is formed in the chips CH.

[0024] The guide groove 34 has a groove width Gw, which is the widthwise dimension of the guide groove 34, that is smaller than the width CHw of the chips CH. The cross-sectional shape of the guide groove 34 is approximately arc-shaped. The groove width Gw of the guide groove 34 can be interpreted as the maximum widthwise dimension of the portion that affects the chips CH. The guide groove 34 is formed by grinding, electric discharge machining, laser machining, or the like. Specifically, when the tip portion 30 is made of a cemented carbide material, grinding is suitable for forming the guide groove 34. When the tip portion 30 is made of a sintered diamond body, PCD (Polycrystalline Diamond), electric discharge machining or laser machining is suitable for forming the guide groove 34. The cross-sectional shape of the guide groove 34 may be trapezoidal, elliptical, or the like. Alternatively, the guide groove 34 may be formed during firing of the tip portion 30 by providing a mold for manufacturing the tip portion 30 with an inverse shape to the guide groove 34.

[0025] 4 is an explanatory diagram for explaining the difficulty of bending the chips CH, in which the horizontal axis indicates the elapsed time from the start of machining the workpiece W, and the vertical axis indicates the difficulty of bending the chips CH in a state where a portion of the chips CH is deformed by the guide groove 34 (i.e., a state where the chips CH have the protrusions BP). In this embodiment, the "difficulty of bending the chips CH" is defined as the value obtained by dividing the second moment of area of ​​the chips CH by the cutting resistance.

[0026] 4, it can be seen that when the guide groove 34 is formed in the tip portion 30, the chips CH of the workpiece W are less likely to bend compared to when the guide groove 34 is not formed in the tip portion 30. In addition, it can be seen that as the groove depth Gd of the guide groove 34 increases, the chips CH become less likely to bend.

[0027] However, according to the research of the present inventors, it was found that when the guide groove 34 has a shallow groove shape, the width of the chips CH at the start of cutting the workpiece W is small, and the chips CH are more likely to curl, which makes the outflow direction of the chips CH unstable.

[0028] For example, when the guide groove 34 has a shallow groove shape in which the groove depth Gd is about 1 / 5 of the groove width Gw, as in the third study example Wc in Figure 5, the minimum curl diameter of the chips CH is smaller than that of the first study example Wa, which does not have a guide groove 34, and the outflow direction of the chips CH is likely to become unstable.

[0029] Furthermore, when the guide groove 34 has a shallow groove shape in which the groove depth Gd is approximately 2 / 7 of the groove width Gw, as in the fourth study example Wd in Figure 5, the minimum curl diameter of the chips CH is smaller than that of the first study example Wa, and the outflow direction of the chips CH is likely to become unstable.

[0030] On the other hand, when the groove depth Gd of the guide groove 34 is equal to or greater than half the groove width Gw, as in the second study example Wb, the fourth study example We, and the fifth study example Wf in Figure 5, the minimum curl diameter of the chips CH is more than twice as large as that of the first study example Wa, and the outflow direction of the chips CH is more likely to be stable.

[0031] In particular, when the cutting edge 331 is rounded as in this embodiment, the width of the chip CH at the start of cutting becomes small, so by reducing the groove width Gw of the guide groove 34 and increasing the groove depth Gd, it is expected that the guide groove 34 will have a curl suppression effect.

[0032] Based on these findings, in the cutting tool 10 of this embodiment, the groove depth Gd of the guide groove 34 is set to be equal to or greater than half the groove width Gw of the guide groove 34. For example, the groove depth Gd of the guide groove 34 is set to 0.04 mm, and the groove width Gw is set to 0.04 mm.

[0033] In addition, the inventors have determined the range of the groove depth Gd of the guide groove 34 in consideration of the second moment of area of ​​the chip CH. A can be calculated based on, for example, the formula F1 shown in Fig. 6. The second moment of area I B can be calculated based on, for example, formula F2 shown in Fig. 7. The formula for calculating the second moment of area of ​​the chip CH varies depending on the cross-sectional shape of the chip CH.

[0034] According to the findings of the present inventors, it has been found that the curl suppression effect of the guide groove 34 is sufficiently large when the rigidity (bending rigidity against vertical curl) of the chips CH produced by the cutting tool 10 with the guide groove 34 is 1.5 times or more the rigidity of the chips CH produced by the cutting tool 10 without the guide groove 34. Then, in the formula F2 of FIG. 7, if X B =4Y B Then, the curl suppression effect of the guide groove 34 becomes sufficiently large when Z>Y B In addition, the thickness of the chip CH is Y B Although it varies slightly depending on the shear angle, it is generally 1 to 3 times the thickness of the workpiece W cut by the cutting tool 10. Note that Z in the formula F2 in FIG.

[0035] Considering these points, it is desirable that the groove depth Gd of the guide groove 34 is set in a range of 1 / 2 to 3 / 2 of the thickness of the workpiece W cut by the cutting tool 10. In the guide groove 34 of this embodiment, the groove depth Gd is set in a range from a first reference value, which is half the thickness of the workpiece W cut, to a second reference value obtained by adding the first reference value to the thickness of the workpiece W. The first reference value is "1 / 2" of the thickness of the cut. The second reference value is "3 / 2" of the thickness of the cut. Regarding the chips CH, X B =4Y B However, for example, X B =8Y B In such a case, by providing two guide grooves 34, the curl suppression effect of the guide grooves 34 can be sufficiently obtained.

[0036] The above-described chip thickness is determined by machining conditions such as the shape of the cutting edge 331 of the cutting tool 10 and the machining feed rate. For example, if the cutting edge is rounded, the chip thickness may not be uniform. In such cases, the "chip thickness" may be interpreted as the chip thickness at the position corresponding to the guide groove 34. For example, in cut-off machining, the chip thickness is the same value as the machining feed rate or the cutting depth CA. That is, in cut-off machining, the chip thickness can be interpreted as the cutting feed rate or the cutting depth CA. The cutting depth CA is the distance the workpiece W penetrates toward the center. In cut-off machining, the cutting depth CA is approximately zero at the moment the cutting edge 331 of the insert 30 begins to contact the workpiece W. Therefore, the cutting depth CA is the value after the workpiece W has rotated once during machining (i.e., the value after the second rotation).

[0037] Incidentally, when the guide groove 34 is present on the cutting edge 331 of the cutting edge portion 33, as shown in Fig. 8, a difference in height (i.e., a step) occurs between the cutting edge 331 and the bottom 341 of the guide groove 34, resulting in an uncut portion LO on the surface of the workpiece W. The height H of this uncut portion LO can be expressed by the following formula F3. H=sinβ×Gd / cos(α+β) ···(F3) In the formula F3, "α" is the angle of the rake face 31 relative to a vertical plane perpendicular to the cutting direction of the workpiece W (i.e., the rake angle). Also, "β" in the formula F3 is the angle of the flank face 32 relative to the cutting direction of the workpiece W (i.e., the clearance angle).

[0038] If the height H of the uncut portion LO exceeds the chip thickness of the workpiece W, the chips CH will be split in the width direction, which is undesirable because it causes the outflow direction of the chips CH to become unstable.

[0039] Therefore, the guide groove 34 is configured so that the height H of the uncut portion LO generated by the guide groove 34 when machining the workpiece W is equal to or less than the chipping thickness of the workpiece W. In other words, the groove depth Gd of the guide groove 34 is set to satisfy the following formula F4. Gd≦TH×cos(α+β) / sinβ (F4) However, "TH" in the formula F4 is the cutting thickness of the workpiece W.

[0040] Furthermore, if the height H of the uncut portion LO exceeds the reference height RH required for the finished surface of the workpiece W, the quality of the finished surface of the workpiece W will be significantly reduced. This reference height is set to, for example, the maximum value of the unevenness dimension allowed by design.

[0041] Therefore, the guide groove 34 is configured so that the height H of the uncut portion LO generated by the guide groove 34 when machining the workpiece W is equal to or less than the reference height RH required for the finished surface of the workpiece W. In other words, the groove depth Gd of the guide groove 34 is set to satisfy the following formula F5. Gd≦RH×cos(α+β) / sinβ (F5)

[0042] Next, a brief description will be given of the operation during machining of the workpiece W. With the spindle holding the workpiece W rotating, cutting processing begins when the cutting tool 10 attached to the tool table is moved to a cutting start position for the workpiece W. In this cutting process, the cutting tool 10 is moved relative to the workpiece W at a predetermined machining feed amount, thereby turning the workpiece W into a desired shape.

[0043] Specifically, the cutting edge 331 of the tip portion 30 comes into contact with the outer periphery of the workpiece W, thereby turning the outer periphery of the workpiece W. At this time, some of the chips CH from the workpiece W enter the guide groove 34 formed in the tip portion 30, causing the chips CH to flow out along the extension direction of the guide groove 34.

[0044] Here, at the start of cutting the workpiece W, the contact width between the cutting edge 331 and the workpiece W is small, and the width of the chips CH is also small. Therefore, if the guide groove 34 has a shallow groove shape, vertical curling is likely to occur in the chips CH, and the outflow direction of the chips CH becomes unstable.

[0045] In contrast, the cutting tool 10 of this embodiment has a deep groove shape in which the groove depth Gd of the guide groove 34 is equal to or greater than half the groove width Gw. This makes it difficult for the chips CH to bend in a cross-sectional shape, ensuring the rigidity of the chips CH and stabilizing the outflow direction of the chips CH.

[0046] In addition, the cutting tool 10 of this embodiment has the following features.

[0047] (1) The groove depth Gd of the guide groove 34 is set within a range from a first reference value, which is half the chip thickness, to a second reference value, which is the chip thickness plus the first reference value. This ensures a sufficient width in the thickness direction of the chips CH, and the guide groove 34 can fully suppress curling.

[0048] (2) The guide groove 34 is configured so that the height H of the uncut portion LO generated by the guide groove 34 during machining of the workpiece W is equal to or less than the uncut thickness of the workpiece W. This makes it possible to stabilize the outflow direction of the chips CH.

[0049] (3) The guide groove 34 is configured so that the height H of the uncut portion LO generated by the guide groove 34 during machining of the workpiece W is equal to or less than the reference height RH required for the finished surface of the workpiece W. This makes it possible to ensure the quality of the finished surface of the workpiece W while stabilizing the outflow direction of the chips CH.

[0050] (4) The cutting edge 331 of the cutting edge portion 33 of the tip portion 30 is curved in a rounded shape over the entire cutting edge. With the cutting tool 10 configured in this manner, the width of the chips CH at the start of cutting the workpiece W is small, and the rigidity of the chips CH tends to be low. However, if the guide groove 34 has a deep groove shape, the chips CH have a cross-sectional shape that makes it difficult for them to bend, thereby ensuring the rigidity of the chips CH.

[0051] (Second embodiment) Next, a second embodiment will be described with reference to Figures 9 and 10. In this embodiment, differences from the first embodiment will be mainly described.

[0052] 9, the rake face 31 of the tip portion 30 is curved in a direction perpendicular to the extension direction of the guide groove 34. That is, the rake face 31 is curved in the width direction of the guide groove 34. Specifically, the rake face 31 is a convex surface that protrudes upward in the width direction of the guide groove 34.

[0053] In the cutting tool 10 configured in this manner, the shape of the chips CH is curved to match the rake face 31. Specifically, as shown in Fig. 10, the chips CH are partially curved in an arc shape, which increases the second moment of area and therefore provides a sufficient curl suppression effect.

[0054] The other points are the same as those of the first embodiment. The cutting tool 10 of this embodiment can obtain the same effects as those of the first embodiment that are achieved by a configuration common to or equivalent to that of the first embodiment.

[0055] (1) In this embodiment, the rake face 31 of the tip portion 30 is curved in a direction perpendicular to the extending direction of the guide groove 34. As a result, the cross-sectional shape of the chips CH is curved to match the shape of the rake face 31, the rigidity of the chips CH is improved, and curling of the chips CH is suppressed, thereby stabilizing the outflow direction of the chips CH.

[0056] (Modification of the second embodiment) The rake face 31 of the tip portion 30 in the second embodiment is a convex surface that protrudes upward in the width direction of the guide groove 34, but is not limited to this. The rake face 31 may be, for example, a concave surface that is recessed downward in the width direction of the guide groove 34. Note that the rake face 31 may be curved, for example, in the extension direction of the guide groove 34.

[0057] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as follows.

[0058] As in the above-described embodiment, it is desirable that the groove depth Gd of the guide groove 34 be set in the range from the first reference value to the second reference value, but this is not limitative and does not have to be the case.

[0059] As in the above-described embodiment, it is desirable that the guide groove 34 is configured so that the height H of the uncut portion LO generated by the guide groove 34 when machining the workpiece W is less than the cutting thickness of the workpiece W, but this is not limited to this and it does not have to be configured that way.

[0060] As in the above-described embodiment, the guide groove 34 is configured so that the height H of the uncut portion LO generated by the guide groove 34 when machining the workpiece W is less than the reference height RH required for the finished surface of the workpiece W.

[0061] In the above embodiment, the cutting edge 331 of the tip portion 30 is illustrated as being entirely rounded, but the cutting edge 331 of the tip portion 30 is not limited to this. The cutting edge 331 of the tip portion 30 may have an angular shape, for example.

[0062] In the above-described embodiment, the cutting tool 10 is used to turn the outer peripheral portion of the workpiece W, but this is not limited to this, and it may also be used to turn, for example, the inner peripheral portion of the workpiece W or the end face of the workpiece W.

[0063] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle.

[0064] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle.

[0065] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., the shapes, positional relationships, etc. are not limited to those unless otherwise specified or when they are fundamentally limited to specific shapes, positional relationships, etc. [Explanation of symbols]

[0066] 10 cutting tools 20 Holder part 30 Tip section 31 Rake face 32 Flank 33 Edge line 34 Guide groove

Claims

1. A cutting tool that turns a workpiece (W) by moving the workpiece relatively at a predetermined processing feed amount, A holder portion (20); a tip portion (30) fixed to the holder portion, The tip portion is A rake face (31) provided on one side; a flank (32) connected to the rake face; a cutting edge portion (33) located between the rake face and the flank face; a guide groove (34) for guiding chips flowing from the cutting edge portion to the rake face, The groove depth of the guide groove is equal to or greater than half of the groove width of the guide groove, the cutting surface is a convex surface that protrudes upward as it approaches the guide groove in a direction perpendicular to the extension direction of the guide groove, so that a convex portion corresponding to the shape of the guide groove is formed in the chip and the chip curves in accordance with the shape of the cutting surface.

2. The cutting tool according to claim 1 , wherein the cutting edge portion has a curved, rounded cutting edge (331) in its entirety.

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