End mill and hole drilling method

Abstract

To provide a technology effective for abandoning removal processing operation of barr generated when hole drilling of a work-piece is performed with an end mill.SOLUTION: An end mill 1 is used for hole drilling of a work-piece, and includes: a first blade part 21 only whose first cutting blade 21a of left torsion relative to a tool central axis line L1 is formed; and a second blade part 22 which is provided on a blade side 20a of the first blade part 21 and only whose second cutting blade 22a of right torsion relative to the tool central axis line L1 is formed. The first blade part 21 is provided with: a general part 21b; and an enlarged diameter part 21c which is provided on the second blade part 22 side of the general part 21b, is beyond the general part 21b, and has an outer diameter d2 identical to the second blade part 22; and a step part 21d connecting the general part 21b and the enlarged diameter part 21c stepwise.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an end mill and a hole drilling method. [Background technology]

[0002] Patent Document 1 discloses an end mill. This end mill is used to drill holes in a workpiece. In drilling a hole in a workpiece, the end mill is rotated around the tool's central axis while revolving (revolving) in a circular direction so that the tool's central axis passes through a circular orbit. A component is assembled in a through hole formed in the workpiece by this drilling. For example, if the workpiece is a bumper for a vehicle, a sensor component is assembled in a through hole formed in the bumper. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-60913 Summary of the Invention [Problem to be solved by the invention]

[0004] When drilling holes while pressing an end mill against the design surface of a workpiece, burrs can form on the opening edge on the back side of the through hole. If a part is inserted into the through hole from the back side of the workpiece while leaving these burrs, the burrs will interfere with the part and become caught in the hole, becoming exposed on the design surface of the workpiece, resulting in poor appearance quality of the workpiece. Therefore, to prevent poor appearance quality of the workpiece, it is necessary to perform a burr removal process after drilling the workpiece. Burr removal work is generally done manually, which can increase the amount of work required.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a technology that is effective in eliminating the need for a process for removing burrs that occur when drilling holes in a workpiece with an end mill. [Means for solving the problem]

[0006] One aspect of the present invention is An end mill used for drilling holes in a workpiece, a first cutting edge portion having only a first cutting edge that is either left-handed or right-handed twisted with respect to a central axis of the tool; a second cutting edge portion provided closer to the cutting edge than the first cutting edge portion and having only a second cutting edge that is either left-handed or right-handed with respect to the tool center axis; an end mill, wherein the first cutting edge portion comprises a general portion, an enlarged diameter portion provided on the second cutting edge portion side of the general portion, the enlarged diameter portion being larger than the general portion and having the same outer diameter as the second cutting edge portion, and a step portion connecting the general portion and the enlarged diameter portion; is located.

[0007] Another aspect of the present invention is A hole drilling method for drilling a hole in a workpiece using the end mill, a through-hole forming step of pressing a cutting edge against a design surface of the workpiece while rotating the end mill in a rotational direction around the tool central axis line, and moving the end mill in a downward direction to a lowered position where the second cutting edge is exposed on the back surface side of the workpiece and the step portion of the first cutting edge is not exposed on the back surface side of the workpiece; and a stepped hole forming step in which the end mill is rotated in the rotation direction around the tool central axis while the stepped portion of the first cutting edge is disposed in the through hole formed in the through hole forming step, and the end mill is rotated in a circumferential direction so that the tool central axis passes through a circular orbit; A hole drilling method comprising: is located. [Effects of the Invention]

[0008] According to the above-described aspects, a hole can be drilled in a workpiece using an end mill. The end mill includes a first cutting edge portion having only a first cutting edge and a second cutting edge portion having only a second cutting edge, and the first cutting edge portion further includes a general portion, an expanded diameter portion, and a stepped portion. In drilling a hole in a workpiece, the end mill is first rotated in the rotational direction around the tool center axis while pressing the cutting edge against the design surface of the workpiece. The end mill is then lowered to a lowered position where the second cutting edge portion is exposed on the back side of the workpiece and the stepped portion of the first cutting edge portion is not exposed on the back side of the workpiece. This allows a through hole to be formed in the workpiece. Then, with the stepped portion of the first cutting edge portion positioned in the through hole, the end mill is rotated in the rotational direction around the tool center axis while rotating in the rotational direction so that the tool center axis passes through a circular orbit. This allows a stepped hole to be formed from the through hole in the workpiece.

[0009] The stepped hole formed in the workpiece has a small-diameter hole portion formed by machining a through-hole with the general portion of the first cutting edge and a large-diameter hole portion formed by machining a through-hole with the enlarged-diameter portion of the first cutting edge. A component is assembled to the workpiece by inserting it into the small-diameter hole portion through the large-diameter hole portion, which is on the back side of the workpiece. Even if a burr occurs on the opening edge of the large-diameter hole portion of the stepped hole, the difference in inner diameter between the large-diameter hole portion and the small-diameter hole portion prevents the burr from interfering with the component and becoming caught in the stepped hole due to interference with the component. This prevents the burr from being exposed on the design surface of the workpiece, which could result in poor appearance quality. As a result, burr removal work before assembling the component to the workpiece is unnecessary.

[0010] As described above, according to the above-described embodiment, it is possible to provide a technique that is effective in eliminating the need for a process for removing burrs that occur when drilling holes in a workpiece with an end mill. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a side view of the end mill of the first embodiment. [Figure 2] FIG. 2 is a side view schematically showing the end mill of FIG. 1. [Figure 3] FIG. 2 is a flowchart of the hole drilling method according to the first embodiment. [Figure 4] FIG. 1 is a side view of an end mill in the process of forming a through hole in a workpiece. [Figure 5] FIG. 10 is a side view of the end mill after forming a through hole in the workpiece. [Figure 6] This is a plan view of Figure 5 as seen from the design surface side of the workpiece. [Figure 7] A side view of the end mill after machining the through hole in the workpiece into a stepped hole. [Figure 8] This is a plan view of Figure 7 as seen from the design surface side of the workpiece. [Figure 9] 10 is a cross-sectional view of the workpiece after a stepped hole has been formed. [Figure 10] 10 is a cross-sectional view showing a state in which a part is being assembled into a stepped hole in the workpiece in FIG. 9. [Figure 11] FIG. 6 is a side view schematically showing an end mill according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the above aspects will be described below.

[0013] In the end mill of the above-mentioned aspect, a cross blade portion is provided between the first blade portion and the second blade portion, where the first cutting edge and the second cutting edge intersect, and it is preferable that the cross blade portion has the same outer diameter as the second blade portion.

[0014] According to this end mill, by providing an intersecting blade portion between the first cutting edge and the second cutting edge, where the first cutting edge and the second cutting edge intersect and have the same outer diameter as the second cutting edge, the range of acceptable product conditions in the axial direction of the end mill can be expanded compared to when the intersecting blade portion is not provided.

[0015] In the hole machining method of the above aspect, it is preferable that the rotation direction of the end mill is the same in the through hole forming step and the stepped hole forming step, and is a direction in which chips are discharged toward the design surface side of the workpiece when the second blade portion cuts the workpiece, and is a direction in which chips are discharged toward the back surface side of the workpiece when the first blade portion cuts the workpiece.

[0016] According to this hole machining method, the end mill can be rotated in the same direction to machine the hole in the workpiece in both the through-hole forming step and the stepped-hole forming step. In the stepped-hole forming step, the through-hole is machined into a large-diameter hole portion by the enlarged-diameter portion of the first cutting edge, and burrs are generated on the opening edge of the large-diameter hole portion.

[0017] Hereinafter, specific embodiments of the end mill and hole drilling method of the above aspects will be described with reference to the drawings.

[0018] In this specification and drawings, unless otherwise specified, a first direction corresponding to the axial direction of the end mill is indicated by arrow X, a second direction corresponding to the radial direction of the end mill is indicated by arrow Y, and a third direction corresponding to the radial direction of the end mill and perpendicular to the second direction is indicated by arrow Z.

[0019] (Embodiment 1) 1. Overall structure of end mill 1 The end mill 1 of the first embodiment shown in Fig. 1 is a tool used to drill holes in a workpiece 2 (see Fig. 4). The end mill 1 extends along a tool central axis L1 and has a shank portion 10 and a cutting edge portion 20. The end mill 1 is attached to a drive unit (not shown) of a processing machine at the shank portion 10.

[0020] The workpiece 2 is, for example, a bumper for a vehicle. A sensor, for example, is attached to this bumper as a component 40, which will be described later.

[0021] 2. Structure of the cutting part 20 1, the cutting portion 20 includes a first cutting portion 21, a second cutting portion 22, and a cross cutting portion 23. The first cutting portion 21 is a portion formed with only a first cutting edge 21a that is twisted leftward with respect to the tool center axis L1. The second cutting portion 22 is a portion that is located closer to the cutting edge 20a than the first cutting portion 21 and is formed with only a second cutting edge 22a that is twisted rightward with respect to the tool center axis L1.

[0022] As shown in FIG. 2, the first cutting edge 21a of the first cutting portion 21 is a cutting edge inclined to the left at a helix angle α with respect to the tool center axis L1. The first cutting portion 21 includes a general portion 21b, an expanded diameter portion 21c, and a stepped portion 21d. The general portion 21b is provided on the shank portion 10 side of the first cutting portion 21 and has an outer diameter d1 (dimensions in the second direction Y and the third direction Z). The expanded diameter portion 21c is provided on the second cutting portion 22 side of the general portion 21b and has an outer diameter d2 that is larger than that of the general portion 21b and is the same as that of the second cutting portion 22. The stepped portion 21d connects the general portion 21b and the expanded diameter portion 21c in a stepped manner. An inclined machining surface 24 is provided on the surface of the stepped portion 21d. The machining surface 24 of the stepped portion 21d is also referred to as the "C-surface." The second cutting edge 22a of the second cutting edge portion 22 is a cutting edge inclined to the right with respect to the tool central axis L1 at a helix angle β.

[0023] 2, the cross cutting edge portion 23 is provided between the first cutting edge portion 21 and the second cutting edge portion 22, and is a portion where the first cutting edge 21a and the second cutting edge 22a intersect. The cross cutting edge portion 23 has the same outer diameter d2 as the second cutting edge portion 22. By providing the cross cutting edge portion 23 between the first cutting edge portion 21 and the second cutting edge portion 22, where the first cutting edge 21a and the second cutting edge 22a intersect and which has the same outer diameter d2 as the second cutting edge portion 22, the axial width of the end mill 1 in which a non-defective product can be obtained can be expanded compared to when the cross cutting edge portion 23 is not provided.

[0024] The helix angle α of the first cutting edge 21 a and the helix angle β of the second cutting edge 22 a are not particularly limited and may take any appropriate value as needed. In this case, the helix angle α and the helix angle β may be different values ​​or may be the same value.

[0025] 3. Hole drilling method Next, a hole drilling method for drilling holes in a workpiece 2 using the end mill 1 configured as described above will be described with reference to Figures 3 to 9. This hole drilling method can be achieved by sequentially executing the steps in the flowchart of Figure 3. Note that other steps may be added as necessary.

[0026] In the hole drilling method of the first embodiment, first, in a first step S101 in Fig. 3, the workpiece 2 is set on the pedestal 5 (see Fig. 4). Following this first step S101, a second step S102 in Fig. 3 is executed. The second step S102 is a through-hole forming step in which a through-hole 3 is formed in the workpiece 2 set on the pedestal 5 by an end mill 1 (see Fig. 5).

[0027] As shown in Figure 4, in a second step S102, the end mill 1 is rotated in a rotation direction R1 around the tool central axis L1 while the cutting edge 20a is pressed against the design surface 2a of the workpiece 2 and moved in a downward direction X1 to a lowered position P (see Figure 5). The downward direction X1 is one direction of the first direction X. When one surface in the thickness direction of the workpiece 2 is defined as the design surface 2a, the surface opposite to the design surface 2a is the back surface 2b.

[0028] The lowered position P of the end mill 1 is a position where the second cutting edge 22 is exposed on the back surface 2b side of the workpiece 2, but the step portion 21d of the first cutting edge 21 is not exposed on the back surface 2b side of the workpiece 2. When the end mill 1 is in the lowered position P, the step portion 21d of the first cutting edge 21 remains inside the through hole 3. The rotation direction R1 of the end mill 1 is a rotation direction such that chips W generated when the second cutting edge 22a of the second cutting edge 22 cuts the workpiece 2 are discharged toward the design surface 2a side of the workpiece 2.

[0029] As shown in FIG. 4, in the second step S102, the workpiece 2 is first cut by the second cutting edge 22a of the second cutting portion 22. When the workpiece 2 is cut by the second cutting edge 22a, chips W are generated on the design surface 2a side of the workpiece 2. These chips W are discharged, for example, by a cup-shaped suction member 30 having a suction function. The suction member 30 is provided on the outer periphery of the end mill 1 via a bellows-shaped expansion and contraction member (not shown) so as to be relatively movable in the first direction X. By pressing the suction member 30 against the design surface 2a of the workpiece 2 and applying suction, the chips W discharged on the design surface 2a side of the workpiece 2 are sucked by the suction member 30. This prevents the chips W from scattering toward the design surface 2a side of the workpiece 2.

[0030] As shown in FIG. 5, in the second step S102, the workpiece 2 is cut by the second blade portion 22, then by the cross blade portion 23, and then by the first cutting edge 21a of the first blade portion 21. Because the cross blade portion 23 has a structure in which the first cutting edge 21a and the second cutting edge 22a intersect, almost no chips W are generated when the workpiece 2 is cut by the cross blade portion 23. When the workpiece 2 is cut by the first cutting edge 21a, chips W are generated on the back surface 2b side of the workpiece 2. The chips W are discharged to the back surface 2b side of the workpiece 2 through a small gap between the enlarged diameter portion 21c of the first blade portion 21 and the through hole 3. In other words, because the first cutting edge 21a has a twist direction opposite to that of the second cutting edge 22a, the direction in which the chips W are discharged is switched. At this time, the chips W are not discharged to the design surface 2a side of the workpiece 2, so that the suction process of the chips W using the suction member 30 or the like can be omitted.

[0031] 5 and 6, according to the second step S102, when the end mill 1 reaches the lowered position P, a through hole 3 having an inner diameter d3 corresponding to the outer diameter d2 is formed in the workpiece 2. At this time, the tool center axis L1 of the end mill 1 and the hole center axis L2 of the through hole 3 coincide with each other.

[0032] 3 is a stepped hole forming step in which a stepped hole 4 is formed in the through hole 3 formed in the second step S102. As shown in FIGS. 7 and 8, in the third step S103, with the step portion 21d of the first cutting edge 21 of the end mill 1 positioned within the through hole 3 of the workpiece 2 (with the end mill 1 positioned at the lowered position P), the end mill 1 is rotated in the rotational direction R1 about the tool center axis L1 while being rotated (also referred to as "revolved") in the circumferential direction R2 so that the tool center axis L1 passes through the circular orbit M. Note that, as long as the step portion 21d of the first cutting edge 21 is positioned within the through hole 3, the position of the end mill 1 in the first direction X may be slightly moved up or down from the lowered position P.

[0033] In the third step S103, the rotation direction R1 of the end mill 1 is set to the same direction as in the second step S102. Therefore, the rotation direction R1 of the end mill 1 is the direction in which chips W are discharged toward the design surface 2a of the workpiece 2 when the second cutting edge 22 cuts the workpiece 2, and is also the direction in which chips W are discharged toward the back surface 2b of the workpiece 2 when the first cutting edge 21 cuts the workpiece 2.

[0034] According to the third step S103, a stepped hole 4 is formed in the workpiece 2 (see FIGS. 7 and 8). The stepped hole 4 is a through hole having two different inner diameters in the first direction X. The stepped hole 4 includes a small diameter hole portion 4a, a large diameter hole portion 4b, and an inclined hole portion 4c formed between the small diameter hole portion 4a and the large diameter hole portion 4b.

[0035] The small diameter hole portion 4a is a portion where the through hole 3 is machined by the general portion 21b of the first cutting edge portion 21 of the end mill 1. This small diameter hole portion 4a has an inner diameter d4 that is larger than the inner diameter d3 of the through hole 3. The large diameter hole portion 4b is a portion where the through hole 3 is machined by the expanded diameter portion 21c of the first cutting edge portion 21 of the end mill 1. This large diameter hole portion 4b has an inner diameter d5 that is larger than the inner diameter d4 of the small diameter hole portion 4a. The inclined hole portion 4c is a portion where the through hole 3 is machined by the stepped portion 21d of the first cutting edge portion 21 of the end mill 1.

[0036] 9, burrs 6 are generated on the opening edge of the large-diameter hole portion 4b of the stepped hole 4. The burrs 6 are formed so as to extend in a direction away from the stepped hole 4 toward the back surface 2b of the workpiece 2. The reason why the burrs 6 are formed in this direction is the same as the reason why the chips W are discharged toward the back surface 2b of the workpiece 2.

[0037] 4. How to assemble part 40 As shown in FIG. 10, a part 40 is assembled into the stepped hole 4 of the workpiece 2. The part 40 has a columnar or cylindrical shape with an outer diameter d6 similar to the inner diameter d4 (see FIG. 7) of the small-diameter hole portion 4a of the stepped hole 4. In this case, the outer diameter d6 of the part 40 is smaller than the inner diameter d5 (see FIG. 7) of the large-diameter hole portion 4b of the stepped hole 4. The part 40 is assembled into the small-diameter hole portion 4a of the stepped hole 4 by being inserted into the stepped hole 4 from the back surface 2b side of the workpiece 2 in an insertion direction X2. The insertion direction X2 is the opposite direction of the downward direction X1 in the first direction X.

[0038] 5. Effects According to the above-described embodiment, the following effects can be obtained.

[0039] In drilling the workpiece 2, first, the end mill 1 is rotated in the rotation direction R1 about the tool center axis L1, while the cutting edge 20a is pressed against the design surface 2a of the workpiece 2 and moved in the downward direction X1 to the lowered position P. This allows the through hole 3 to be formed in the workpiece 2. Then, with the stepped portion 21d of the first cutting edge 21 positioned within the through hole 3, the end mill 1 is rotated in the rotation direction R1 about the tool center axis L1 and rotated in the rotation direction R2 so that the tool center axis L1 passes through the circular orbit M. This allows the stepped hole 4 to be formed from the through hole 3 in the workpiece 2.

[0040] The stepped hole 4 formed in the workpiece 2 has a small-diameter hole portion 4a formed by machining the through-hole 3 with the general portion 21b of the first cutting edge 21, and a large-diameter hole portion 4b formed by machining the through-hole 3 with the expanded-diameter portion 21c of the first cutting edge 21. A component 40 is inserted into the small-diameter hole portion 4a through the large-diameter hole portion 4b on the back surface 2b of the workpiece 2, thereby assembling the component 40 to the workpiece 2. Even if a burr 6 is generated on the opening edge of the large-diameter hole portion 4b of the stepped hole 4, the difference in inner diameter between the large-diameter hole portion 4b and the small-diameter hole portion 4a prevents the burr 6 from interfering with the insertion of the component 40 and from being caught in the stepped hole 4 due to interference with the component 40. This prevents the burr 6 from being exposed on the design surface 2a of the workpiece 2, which could result in poor appearance quality for the workpiece 2. This eliminates the need to remove the burrs 6 before assembling the component 40 to the workpiece 2, thereby reducing the number of steps required.

[0041] As described above, according to the first embodiment, it is possible to provide a technique that is effective in eliminating the need for a process for removing burrs 6 that are generated when a hole is drilled in the workpiece 2 with the end mill 1.

[0042] (Embodiment 2) As shown in Figure 11, the end mill 1A of the second embodiment differs from the end mill 1 of the first embodiment in that the first cutting edge 21 and the second cutting edge 22 of the cutting edge 20 are in contact with each other and do not have the intersecting cutting edge 23 (see Figure 2). The other configurations and methods are the same as those of the first embodiment.

[0043] According to the second embodiment, the structure of the end mill 1A can be simplified by omitting the portion corresponding to the cross cutting edge portion 23.

[0044] In addition, the same effects as those of the first embodiment are achieved.

[0045] 5. Modifications The present invention is not limited to the above-described embodiment, and various applications and modifications are possible without departing from the scope of the present invention. For example, the following embodiments can be implemented by applying the above-described embodiment.

[0046] In the embodiment described above, the first cutting edge 21a of the first cutting portion 21 is left-handed and the second cutting edge 22a of the second cutting portion 22 is right-handed, but instead, the first cutting edge 21a of the first cutting portion 21 may be right-handed and the second cutting edge 22a of the second cutting portion 22 may be left-handed. In this case, the rotation direction of the end mill 1 during hole drilling is set to the opposite direction to the rotation direction R1.

[0047] In the above embodiment, the rotation direction of the end mill 1 during hole drilling is always set to rotation direction R1. However, instead of this, the rotation direction may be changed from the initial rotation direction R1 to the opposite direction to rotation direction R1 during the process of lowering the end mill 1 in the downward direction X1. This makes it possible to suppress the generation of burrs 6 on the back surface 2b of the workpiece 2. Alternatively, the initial rotation direction of the end mill 1 may be set to the opposite direction to rotation direction R1, and then the rotation direction may be changed to rotation direction R1 during the process of lowering the end mill 1 in the downward direction X1. This makes it possible to suppress the amount of chips W discharged on the design surface 2a of the workpiece 2.

[0048] In the above embodiment, the workpiece 2 is a vehicle bumper and the part 40 is a sensor, but the combination of the workpiece 2 and the part 40 is not limited to this, and the types of the workpiece 2 and the part 40 can be changed appropriately as needed. For example, the workpiece 2 may be something other than a bumper, and the part 40 may be something other than a sensor. [Explanation of symbols]

[0049] 1,1A...end mill, 2...workpiece, 2a...design surface, 2b...rear surface, 3...through hole, 4...step hole, 20a...cutting edge, 21...first cutting edge, 21a...first cutting edge, 21b...normal portion, 21c...expansion portion, 21d...step portion, 22...second cutting edge, 22a...second cutting edge, 23...cross cutting edge portion, d1,d2...outside diameter, L1...tool center axis, M...circular orbit, P...descent position, R1...rotation direction, R2...circumferential direction, S101-S103...hole machining method, S102...second step (through hole forming step), S103...third step (step hole forming step), W...chips, X1...descent direction

Claims

1. An end mill used for drilling holes in a workpiece, a first cutting edge portion having only a first cutting edge that is either left-handed or right-handed twisted with respect to a central axis of the tool; a second cutting edge portion provided closer to the cutting edge than the first cutting edge portion and having only a second cutting edge that is either left-handed or right-handed with respect to the tool center axis, The first cutting edge portion comprises a general portion, an enlarged diameter portion provided on the second cutting edge side of the general portion, the enlarged diameter portion being larger than the general portion and having the same outer diameter as the second cutting edge portion, and a step portion connecting the general portion and the enlarged diameter portion in a stepped manner.

2. 2. The end mill according to claim 1, wherein a cross blade portion is provided between the first blade portion and the second blade portion, where the first cutting edge and the second cutting edge intersect, and the cross blade portion has the same outer diameter as the second blade portion.

3. A hole drilling method for drilling a hole in a workpiece using the end mill according to claim 1 or 2, comprising: a through-hole forming step of pressing a cutting edge against a design surface of the workpiece while rotating the end mill in a rotational direction around the tool central axis, and moving the end mill in a downward direction to a lowered position where the second cutting edge is exposed on the back surface side of the workpiece and the step portion of the first cutting edge is not exposed on the back surface side of the workpiece; and a stepped hole forming step in which the end mill is rotated in the rotation direction around the tool central axis while the stepped portion of the first cutting edge is disposed in the through hole formed in the through hole forming step, and the end mill is rotated in a circumferential direction so that the tool central axis passes through a circular orbit; A hole drilling method comprising the steps of:

4. 4. The hole machining method according to claim 3, wherein the rotation direction of the end mill is the same in the through hole forming step and the stepped hole forming step, and is a direction in which chips are discharged toward the design surface side of the workpiece when the workpiece is cut by the second blade portion, and a direction in which chips are discharged toward the back surface side of the workpiece when the workpiece is cut by the first blade portion.

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