JP2011177853A - Cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that in an invisible tear line part of an instrument panel, when a thin part of a groove bottom is wide, a surface increases a quantity of deformation to lower a texture, so that a groove having a small bottom width is requested to be worked, however, in a cutting work of the groove, an outside diameter of a cutting tool needs to be increased so as to ensure a strength to prevent the breakage of the cutting tool, so that the width of the groove bottom is hardly reduced. <P>SOLUTION: In the cutting tool having an outer periphery cutting edge part 20 provided in an end of a shank, the outer periphery cutting edge part 20 includes a first tapered cutting edge 21 having an outside diameter smaller toward the end and a second tapered cutting edge 22 continuous to the end side of the first cutting edge and having an outside diameter smaller toward the end. A taper angle α of the first cutting edge is different from a taper angle β of the second cutting edge. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cutting tool for cutting a tapered groove.

For example, an instrument panel of an automobile is provided with a planned airbag deployment fracture line (hereinafter referred to as “tear line”) for inflating the airbag from the instrument panel. In the tear line portion, a groove is formed by cutting or the like so as to break and open when the airbag is inflated.
Conventionally, in order to improve the texture of the instrument panel surface, the groove of the tear line portion is sometimes cut from the back surface.
Conventionally, a cutting with a tapered first blade on the shank side and a second blade parallel to the tool rotation axis on the tip side from the first blade so as to prevent generation of burrs and residual cutting waste. Tools are being developed. (For example, refer to Patent Document 1).

JP 2006-315115 A

However, in the cutting tool having the above-mentioned shape, the second blade for machining the groove bottom is parallel to the tool rotation axis. Therefore, the outer diameter must be increased to some extent to prevent breakage of the cutting tool, and the groove that can be machined. The bottom width becomes wider. Accordingly, as shown in FIG. 8, when the cutting tool having the above shape is applied to the instrument panel 100 and the groove 101A of the tear line portion 101 is machined, the thin portion 101C of the groove bottom 101B becomes wide (W2). As shown in FIGS. 9A to 9C, the amount of deformation of the tear line portion 101 when an external force is applied increases, and for example, wrinkles 101D and dents 101E on the surface become conspicuous. There was a problem that the texture of the instrument panel 100 was lowered.
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a cutting tool that can stably cut a groove having a narrow bottom width while ensuring sufficient cutting performance and strength.

In order to achieve the above object, the present invention provides a cutting tool having an outer peripheral blade portion at the tip of a shank, wherein the outer peripheral blade portion has a tapered first blade whose outer diameter decreases toward the tip, It is composed of a second blade with a tapered shape that continues to the tip side of the first blade and has an outer diameter that decreases toward the tip, and the taper angle α of the first blade is different from the taper angle β of the second blade. It is characterized by.
In this invention, since the outer diameter of the said 2nd blade tip which processes a groove bottom is small, a groove | channel with a narrow bottom width can be processed. Further, since the outer diameter of the second blade on the shank side is large, the cutting tool strength can be ensured and breakage can be prevented.
Furthermore, in the present invention, the taper angle α of the first blade that processes the groove opening is different from the taper angle β of the second blade. When α is larger than β, the thickness of the workpiece at the groove opening is ensured, so that the deformation region of the workpiece tear line can be limited to the thin portion at the groove bottom. .
Therefore, when the groove of the tear line part is machined on the workpiece by the cutting tool according to the present invention, the deformation amount of the tear line part when an external force is applied can be reduced, and the surface texture can be improved. it can.
In the present invention, the groove opening of the workpiece is cut by the first blade having a large outer diameter and high rigidity, so that the deflection of the cutting tool in the groove opening is reduced. Furthermore, since the first blade has a tapered shape whose outer diameter decreases toward the tip, the angle of the corner of the groove opening becomes an obtuse angle. Therefore, the machinability of the groove opening is improved and burrs can be prevented.

In the present invention, the outer diameter of the tip of the second blade is set to be 60% or more and less than 98% of the outer diameter of the boundary between the first blade and the second blade. It is characterized by.
In the present invention, the outer diameter of the tip of the second blade is set to be less than 98% with respect to the outer diameter of the boundary between the first blade and the second blade. The width of the groove bottom is narrower than that of a groove machined by a conventional cutting tool having a second blade parallel to the tool rotation axis. Thereby, the deformation amount of the tear line part when an external force is applied can be reduced, and the surface texture can be improved.
In the present invention, since the outer diameter of the tip of the second blade is set to 60% or more with respect to the outer diameter of the boundary between the first blade and the second blade, the second blade Has a sufficient cutting tool strength that can counter the cutting resistance of the groove bottom and the cutting resistance of the back wall of the groove. Thereby, the breakage of the cutting tool in the groove cutting process can be prevented.

In the present invention, the taper angle α of the first blade is twice the angle θ formed by the tool rotation axis and a straight line passing through the intersection of the workpiece surface and the tool rotation axis and perpendicular to the workpiece surface. It is characterized by being set to a larger angle.
In the present invention, the taper angle α of the first blade is larger than twice the angle θ formed by the tool rotation axis and a straight line passing through the intersection of the workpiece surface and the tool rotation axis and perpendicular to the workpiece surface. Since the angle is set, even when the tool rotation axis is not perpendicular to the workpiece surface, the angle of the corner of the groove opening becomes an obtuse angle. Thereby, it is possible to prevent burrs by making the groove opening portion have good machinability.

  In the present invention, the bottom surface of the processing groove is a flat surface. Thereby, halation does not occur in shape measurement using light or sound, and the depth dimension of the groove can be easily measured using, for example, a laser displacement meter. In addition, when the groove is further machined by an ultrasonic cutter or the like after the groove machining by the cutting tool of the present invention, the tool blade edge can be prevented from shifting in the groove width direction, so that the machining is facilitated.

  ADVANTAGE OF THE INVENTION According to this invention, the cutting tool which can cut stably a groove | channel with a narrow bottom width is ensured, ensuring sufficient machinability and intensity | strength. When the cutting tool according to the present invention is used to process the groove of the tear line portion on the workpiece, the deformation amount of the tear line portion when an external force is applied to the workpiece can be reduced. The texture of the material surface can be improved.

It is a perspective view ahead of the compartment of a car. It is the II-II sectional view taken on the line of the instrument panel in FIG. It is a side view of the cutting device in one embodiment of the present invention. It is a front view of the end mill concerning one embodiment of the present invention. It is principal part sectional drawing of FIG. It is a front-end | tip part enlarged view of the end mill which concerns on one Embodiment of this invention. It is sectional drawing which shows the cross-sectional shape of the to-be-processed material groove part processed with the end mill which concerns on one Embodiment of this invention. It is sectional drawing which shows the cross-sectional shape of the workpiece groove part processed with the conventional end mill. It is sectional drawing which shows the deformation | transformation which arose in the tear line part of the instrument panel.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, an end mill that forms a tear line groove in an instrument panel of an automobile is illustrated as an aspect of a cutting tool to which the present invention is applied. However, the present invention is not limited to this.
FIG. 1 is a perspective view in front of a passenger compartment of an automobile.
The airbag device 1 on the passenger seat side is housed inside the instrument panel 2 in the front of the passenger compartment. Further, a tear line 3 is provided in the storage portion of the airbag device 1 of the instrument panel 2.
The tear line 3 is a fragile portion formed in a linear shape on the instrument panel 2 and is broken when the airbag is inflated. This broken portion is an opening through which the airbag bulges from the instrument panel 2. Part.
2 is a cross-sectional view of the instrument panel 2 in FIG. 1 taken along the line II-II.
In order to improve the appearance of the instrument panel 2, the processing of the groove 6 constituting the tear line 3 is performed from the back surface 5.

FIG. 3 is a side view of the cutting apparatus 7 according to the present embodiment.
The cutting device 7 includes a Z-axis guide rail 8 extending in the vertical direction, a processing block 9 movable along the Z-axis guide rail 8, a main shaft 10 that is provided on the processing block 9 and that is rotatable, and is held by the main shaft 10. End mill 11, base 12, X-axis guide rail 13 provided on the base 12 and extending in the X-axis direction, X-axis table 14 movable along the X-axis guide rail 13, and X-axis table 14, a Y-axis guide rail 15 that extends in the Y-axis direction, a Y-axis table 16 that is movable along the Y-axis guide rail 15, and a workpiece support that is provided on the Y-axis table 16 and supports a workpiece. And a jig 17.
When the groove 6 constituting the tear line 3 is processed on the back surface 5 of the instrument panel 2 by the cutting device 7, the X-axis table 14 and the Y-axis table 16 are rotated while the end mill 11 is rotated by the main shaft 10. Then, the machining block 9 is moved to adjust the relative position between the end mill 11 and the instrument panel 2, and the groove 6 is cut with respect to the instrument panel 2 which is a workpiece.

FIG. 4 is a front view of the end mill 11 according to the present embodiment.
The end mill 11 according to the present embodiment has a shank 18 and is provided with an outer peripheral blade portion 20 at the tip of the shank 18. The outer peripheral blade portion 20 has a tapered shape in which the outer diameter decreases toward the tip, and is formed continuously from the first blade 21 on the shank 18 side and the tip of the first blade 21, and the outer diameter toward the tip. The taper angle α of the first blade 21 is set to a different angle from the taper angle β of the second blade 22. In the present embodiment, the taper angle α is set larger than the taper angle β.
Both of the outer diameters of the first blade 21 and the second blade 22 gradually increase from the tip side toward the shank side, and a cutting tool in which the outer peripheral blade is provided in parallel with the tool rotation axis as in the prior art ( Compared with Patent Document 1), as will be described later, the strength and rigidity of the cutting tool are high, and even if the outer diameter of the tip 19 of the second blade 22 is reduced, sufficient cutting tool strength can be ensured and stable. Cutting is possible.

Moreover, the length dimension L of the second blade 22 in the direction of the tool rotation axis 23 is set to be smaller than the depth dimension D (see FIG. 7) of the groove 6 to be processed into the workpiece. Therefore, at the time of cutting, the groove opening 28 (see FIG. 7) is processed by the first blade 21 having a large outer diameter, and the groove back side wall portion 29 and the groove bottom 30 (see FIG. 7) are processed by the second blade 22. .
Since the groove opening 28 is processed by the first blade 21, the machinability at the groove opening 28 is improved, and burrs can be prevented. Moreover, since the dimension L of the 2nd blade 22 can be shortened, the rigidity of the 2nd blade 22 can be ensured.

Further, in the end mill 11 according to the present embodiment, the outer diameter C of the tip 19 of the second blade 22 is not less than 60% and 98% of the outer diameter B of the boundary between the first blade 21 and the second blade 22. The dimension is set to less than%.
The present inventors tried a machining test in which the instrument panel 2 is grooved by variously changing the outer diameter C of the tip 19 of the second blade 22. Also, a cutting tool (Patent Document 1) provided with a tapered first blade on the shank side and a second blade parallel to the tool rotation axis on the tip side from the first blade is prepared, and this prepared comparison A machining test using a tool was also attempted. Here, the outer diameter B was the same as the diameter of the second blade of the comparative tool. As a result, in a tool having an outer diameter C of 98% or more of the outer diameter B, wrinkles or dents, for example, as shown in FIG. did. On the contrary, in the tool having the outer diameter C less than 98% of the outer diameter B, the surface 4 of the instrument panel 2 hardly shows wrinkles or dents as shown in FIG. Became inconspicuous and the texture of the surface 4 of the instrument panel 2 could be improved.
In addition, it was found that when the outer diameter C is set to a dimension less than 60% of the outer diameter B, the outer diameter of the second blade 22 is small, so that the strength is low and breaks easily.
When the groove 6 constituting the tear line 3 is cut in the instrument panel 2 having a thickness of 3 mm, the outer diameter C of the end mill 11 is 0.6 mm or more and less than 0.98 mm, and the outer diameter B is 1 mm. When the outer diameter of the shank 18 is 4 mm and the twist angle is 20 °, the end mill 11 can be cut without breakage, and the width W1 of the deformation region is narrowed to improve the appearance.

FIG. 5 is a cross-sectional view of the main part of FIG.
Since the instrument panel 2 is generally a panel component having a curvature, depending on the position, the tool rotation shaft 23 and the workpiece surface may be used when machining is performed using the cutting device 7 in which the direction of the tool rotation shaft 23 is constant. 24 is not vertical, but the angle θ between the tool rotation axis 23 and the straight line 26 passing through the intersection 25 of the tool rotation axis 23 and the workpiece surface 24 and perpendicular to the workpiece surface 24, that is, the workpiece surface 24 tilt angles are generated.
In this case, if the angles of the corners 27a and 27b of the groove opening in the workpiece are φa and φb, respectively, the angles φa and φb are obtained by using the angle θ and the taper angle α of the first blade 21 described above. It is represented by the following formulas (1) and (2).
φa = 90 + α / 2−θ (1)
φb = 90 + α / 2 + θ (2)
By the way, in the present embodiment, the taper angle α of the first blade 21 is set to an angle larger than twice the angle θ.
Therefore, even if the tool rotation shaft 23 and the workpiece surface 24 are not perpendicular and the angle θ is generated, the angles φa and φb of the corners 27a and 27b of the groove opening are obtuse and the machinability is reduced. Burr can be prevented as good.
In addition, since the inclination angle of the work surface of the instrument panel 2 is about 30 ° at the maximum, when the groove 6 constituting the tear line 3 is cut using the cutting device 7 as described above, the angle α Is preferably about 60 °.

Further, in the end mill 11 according to the present embodiment, the tip 19 of the second blade 22 is flat as shown in FIGS. 4 and 6.
For this reason, as shown in FIG. 7, the groove bottom 30 of the groove 6 is a flat surface, and no halation occurs in the shape measurement by light. For example, the depth dimension D of the groove 6 can be easily measured using a laser displacement meter. Can do.
In addition, after the groove 6 is cut in the instrument panel 2 by the end mill 11 according to the present embodiment, the groove bottom 30 is not a slope when the groove is further processed by an ultrasonic cutter or the like. Deviation of the tool edge in the groove width direction can be prevented, and additional machining becomes easy.
The tip 19 of the second blade 22 is not limited to a flat surface, and the tip may have a recess having a clearance angle of a predetermined angle (for example, an angle of 3 °), or the tip may be spherically convex. If the tip 19 is convex in a spherical shape, the appearance quality of the instrument panel 2 is improved. If the tip 19 has a recess having a clearance angle, for example, the groove 6 of the instrument panel 2 by an ultrasonic cutter is used. The secondary machining (additional machining) of the groove bottom 30 becomes easy.
The groove bottom 30 of the groove 6 of the instrument panel 2 only needs to be grooved with an appropriate width (for example, the outer diameter C of the tip 19 of the second blade 22 in FIG. 4). It suffices if the groove bottom 30 is nearly flat. This is because if the surface is nearly flat, the groove depth can be measured with a laser displacement meter and the secondary machining (additional machining) of the groove bottom 30 can be performed with an ultrasonic cutter.

  In addition, embodiment mentioned above shows the one aspect | mode of this invention to the last, and a deformation | transformation and application are arbitrarily possible within the scope of the present invention.

  In the embodiment described above, an automobile instrument panel is exemplified as a workpiece, but the present invention can also be applied to a handle member of an automobile, a member in front of a seat of a motorcycle, and the like. Also in this case, since the tool can be prevented from being broken and a groove having a narrow bottom width can be processed, the appearance of the member can be improved.

  Moreover, although resin was illustrated as a material of a workpiece in the embodiment mentioned above, the material of a workpiece may be various materials, such as a metal and glass.

In the embodiment described above, as a mechanism for adjusting the relative position of the end mill 11 and the instrument panel 2, an X-axis table 14 movable in the X-axis direction, a Y-axis table 16 movable in the Y-axis direction, and Z Although the mechanism provided with the machining block 9 movable in the axial direction is illustrated, the relative position and posture of the end mill 11 and the instrument panel 2 can be freely set by separately providing a rotating shaft or an articulated robot. It may be a mechanism that can be controlled.
In the end mill 11 according to the present embodiment, since the tip 19 of the second blade 22 is a flat surface, the relative position and posture of the end mill 11 and the instrument panel 2 are controlled, and the tool rotation shaft 23 is placed on the workpiece surface 24. When kept perpendicular to the workpiece surface 24, the workpiece surface 24 and the groove bottom 30 are parallel at an arbitrary position.
Therefore, the thickness of the instrument panel 2 at the groove bottom 30 can be easily measured. Further, even if the tool cutting edge is displaced in the groove width direction in the above-described additional machining, the remaining thickness becomes equal, and the additional machining work is facilitated.

2 Instrument panel 3 Tier line 6 Groove 18 Shank 19 Tool tip (tip of the second blade)
DESCRIPTION OF SYMBOLS 20 Peripheral blade part 21 1st blade 22 2nd blade 23 Tool rotating shaft 24 Workpiece material surface 25 Intersection of tool rotating shaft and workpiece surface 26 Workpiece passing through intersection of tool rotating shaft and workpiece surface Straight line perpendicular to the surface B Outer diameter of the boundary between the first blade and the second blade C Outer diameter of the tip of the second blade L Length of the second blade in the direction of the tool rotation axis D Groove to be machined in the workpiece Depth Dimension α Taper angle of the first blade β Taper angle of the second blade θ Angle formed by the tool rotation axis and a straight line passing through the intersection of the tool rotation axis and the workpiece surface and perpendicular to the workpiece surface

Claims (4)

In a cutting tool with an outer peripheral edge at the tip of the shank,
The outer peripheral blade portion has a tapered first blade whose outer diameter decreases toward the tip, and a tapered second blade that continues to the distal end side of the first blade and whose outer diameter decreases toward the tip. A cutting tool configured, wherein a taper angle α of the first blade is different from a taper angle β of the second blade.   The outer diameter of the tip of the second blade is set to a dimension of 60% or more and less than 98% with respect to the outer diameter of the boundary between the first blade and the second blade. The cutting tool according to 1.   The taper angle α of the first blade is set to an angle larger than twice the angle θ formed by the tool rotation axis and a straight line passing through the intersection of the workpiece surface and the tool rotation axis and perpendicular to the workpiece surface. The cutting tool according to claim 1, wherein the cutting tool is provided.   The cutting tool according to any one of claims 1 to 3, wherein the cutting tool is an end mill for forming a tear line in an interior part of a vehicle.

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