Taper drill, and processing method for rib groove of metallic mold

Abstract

To provide a taper drill improved in processing efficiency.SOLUTION: A taper drill is provided with a tip cutting blade positioned at a tip part of a rod-like drill main body extending along a rotary center shaft of a tool, and a chip discharging groove extending along the rotary center shaft of the tool, on an outer peripheral surface of the drill main body. A minimum outer diameter dimension D1 of the drill main body at the tip part of the chip discharging groove and a groove length L1 of the chip discharging groove satisfy both relational expressions of D1≤2 mm and 8≤L1 / D1≤20. The taper drill further has a groove cutting blade positioned at an end portion in a rear side in a rotating direction of the tool of the chip discharging groove and extended along the chip discharging groove. Outer diameter dimensions of the groove cutting blade become larger as going from the tip side of the drill main body toward a rear end thereof.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a taper drill and a method for machining a rib groove in a mold. [Background technology]

[0002] It is known that the rib groove shape of a mold is machined by contour machining as shown in Patent Document 1 or by reciprocating machining as shown in Patent Document 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7152673 [Patent Document 2] Patent No. 4573340 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in recent years, there has been an increasing demand for machining complex mold shapes, which has led to a corresponding demand for thinner and deeper rib grooves than before.To form thinner and deeper rib grooves, the ratio of tool length to tool diameter must be increased. In contour machining, if the ratio of tool length to tool diameter increases, the machining time increases and machining efficiency decreases. Furthermore, in reciprocating cutting, if the ratio of tool length to tool diameter increases, the cutting edge length also increases, which poses a problem of the tool bending and risk of breakage.

[0005] In view of the above circumstances, one of the objects of the present invention is to provide a tapered drill with improved machining efficiency and a method for machining rib grooves in a mold using the tapered drill. [Means for solving the problem]

[0006] (1) A tapered drill according to one aspect of the present invention includes a tip cutting edge located at the tip of a rod-shaped drill body extending along a tool rotation central axis, and a chip flute extending along the tool rotation central axis on the outer peripheral surface of the drill body. A minimum outer diameter D1 of the drill body at the tip of the chip flute and a flute length L1 of the chip flute satisfy both D1≦2 mm and 8≦L1 / D1≦20. The drill further includes a groove cutting edge located at the end of the chip flute on the rear side in the tool rotation direction and extending along the chip flute. The outer diameter of the groove cutting edge increases from the tip end to the rear end of the drill body.

[0007] According to the above configuration, since the tip of the drill body has a tip cutting edge, it is possible to drill a hole in the depth direction without drilling a pilot hole in the workpiece using a separate tool. Furthermore, since the drill body has a groove cutting edge on the outer periphery, it is possible to form a wall with an inclined angle while drilling the hole with the tip cutting edge. By repeating this process using plunge cutting, it is possible to machine rib grooves with sufficient machining efficiency. The groove length L1 and the minimum outer diameter D1 are preferably in the range of 10≦L1 / D1≦20.

[0008] (2) According to one aspect of the present invention, there is provided a method for machining a mold rib groove, which forms a rib groove in a workpiece by repeating plunge machining using the tapered drill of (1). According to this method for machining rib grooves in a mold, deep and narrow rib grooves can be formed simply by moving the tapered drill in the depth direction. Compared to forming rib grooves by reciprocating machining or contour machining, this method enables highly efficient machining of narrow rib grooves.

[0009] (3) The rib grooves formed by the plunge machining may be finished using an end mill other than the taper drill. According to this method for machining rib grooves in a mold, the inner wall surfaces of the rib grooves can be finished to a smoother surface. [Effects of the Invention]

[0010] According to one aspect of the present invention, there are provided a tapered drill with improved machining efficiency and a method for machining a rib groove in a mold using the tapered drill. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a side view of a tapered drill according to an embodiment. [Figure 2] FIG. 2 is a process diagram of a method for processing a mold rib groove according to an embodiment. [Figure 3] FIG. 3 is a process diagram of a method for processing a mold rib groove according to an embodiment. [Figure 4] FIG. 4 is a process diagram of a method for processing a mold rib groove according to an embodiment. [Figure 5] FIG. 5 is a process diagram of a method for processing a mold rib groove according to an embodiment. [Figure 6] FIG. 6 is a process diagram of a method for processing a mold rib groove according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a tapered drill according to one embodiment of the present invention and a method for machining a rib groove in a mold using the same will be described with reference to the drawings.

[0013] (Taper drill) FIG. 1 is a side view of a tapered drill 10 according to an embodiment. As shown in Fig. 1, the tapered drill 10 includes a rod-shaped drill body 1 extending along the tool rotation central axis O. The drill body 1 includes a cutting edge portion 1A and a shank portion 1B connected to the rear end of the cutting edge portion 1A. The cutting edge portion 1A and the shank portion 1B are arranged coaxially with the tool rotation central axis O as a common axis.

[0014] In this embodiment, the direction in which the tool rotation center axis O of the tapered drill 10 extends may be simply referred to as the axial direction. Of the directions extending along the tool rotation center axis O, the direction from the shank portion 1B toward the cutting edge portion 1A is referred to as the front end side of the tapered drill 10 and the drill body 1, and the direction from the cutting edge portion 1A toward the shank portion 1B is referred to as the rear end side of the tapered drill 10 and the drill body 1.

[0015] The direction perpendicular to the tool rotation axis O is called the radial direction. Within the radial direction, the direction approaching the tool rotation axis O is called the radially inner direction, and the direction away from the tool rotation axis O is called the radially outer direction. The direction of rotation around the tool rotation center axis O is called the circumferential direction. Among the circumferential directions, the direction in which the tapered drill 10 is rotated during cutting is called the tool rotation direction T, and the opposite rotation direction is called the side opposite to the tool rotation direction T.

[0016] In the direction along the tool rotation center axis O, the side where the cutting edge portion 1A is located is the tip side of the drill body 1, and the side where the shank portion 1B is located is the rear side of the drill body 1. In the tapered drill 10, the shank portion 1B is attached to a machine tool via an arbor. In this embodiment, the diameter of the shank portion 1B is larger than the diameter of the cutting edge portion 1A. The drill body 1 has a neck portion 1C between the shank portion 1B and the cutting edge portion 1A. The neck portion 1C is tapered toward the tip side.

[0017] In this embodiment, the drill body 1 of the tapered drill 10 is made of cemented carbide. It is preferable to form a hard coating on the surface of the drill body 1 so that it can withstand die machining of high-hardness steel and difficult-to-cut materials.

[0018] The cutting portion 1A includes a tip cutting edge 2 located at the tip of the cutting portion 1A and a chip discharge flute 3 extending on the outer circumferential surface of the cutting portion 1A along the tool rotation central axis O. In other words, the drill body 1 includes the tip cutting edge 2 and the chip discharge flute 3. The tip cutting edge 2 is formed at the intersection of the tip flank 2a, which is the surface facing the tip of the drill body 1 in the direction of the tool rotation central axis O, and the chip discharge flute 3. The tapered drill 10 has two tip cutting edges 2. It is sufficient to have multiple tip cutting edges 2; for example, three tip cutting edges 2 will improve machining efficiency compared to two tip cutting edges. The tip of the tip cutting edge 2 forms a chisel portion. For example, a thinning cutting edge may be formed adjacent to the chisel portion. By having a thinning cutting edge, stable cutting can be performed when cutting is repeated in the -Z direction (vertically downward).

[0019] The chip flutes 3 are grooves that open to the tip flank 2a and the outer peripheral surface facing radially outward of the drill body 1. The chip flutes 3 extend spirally from the intersection with the tip flank 2a toward the rear end of the drill body 1. As the chip flutes 3 extend from the tip flank 2a toward the rear end of the drill body 1, they extend in the opposite direction of the tool rotation direction T. Two chip flutes 3 are provided on the cutting edge portion 1A, spaced apart from each other in the circumferential direction.

[0020] For example, the core thickness of the chip discharge groove 3 is 20 to 50%, and by gradually reducing the core thickness from the front end to the rear end, good chip discharge performance is achieved even when rib grooves are machined. In this case, the reduction in core thickness from the front end to the rear end of the cutting edge portion 1A is preferably about 10%. The chip discharge groove 3 may also be formed in a wave shape or a shape with nicks, which can reduce resistance during cutting.

[0021] A groove cutting edge 4 is formed at the rear end of the chip discharge flute 3 in the tool rotation direction T. The groove cutting edge 4 extends spirally from the outer peripheral end of the tip cutting edge 2 toward the rear end side of the drill body 1.

[0022] The minimum outer diameter D1 of the drill body 1 is 2 mm or less at the tip of the chip flute 3. The ratio of the flute length L1 of the chip flute 3 to the minimum outer diameter D1 of the drill body 1 satisfies 8≦L1 / D1≦20. The groove cutting edge 4 has a shape in which the outer diameter dimension D increases from the front end to the rear end of the drill body 1. The rotation trajectory of the groove cutting edge 4 around the tool rotation center axis O is tapered, as shown by the auxiliary line L2 in Figure 1, with the diameter increasing from the front end to the rear end of the drill body 1.

[0023] In the drill body 1, the taper angle θ, defined by the angle between the auxiliary line L2 and the tool rotation center axis O, is preferably in the range of 0°<θ≦3.0°. When the taper angle θ is greater than 0°, the tapered drill 10 can be used to machine rib grooves simply by advancing in the Z-axis direction on a wall with an inclined angle. By setting the taper angle θ to 3.0° or less, rigidity can be ensured even for a tool that machines a narrow, thin range with an L1 / D1 ratio of 8 to 20. The range of the taper angle θ is preferably θ≦2.0°.

[0024] Furthermore, the tapered drill 10 of this embodiment has a neck portion 1C between the cutting edge portion 1A and the shank portion 1B, allowing the tool to have a multi-stage structure. This ensures rigidity even when the tool is used to machine a narrow area with an L1 / D1 ratio of 10 to 20.

[0025] The tapered drill 10 of this embodiment described above has a point cutting edge 2 at the tip of the drill body 1, making it possible to drill a hole in the depth direction without having to drill a pilot hole in the workpiece using a separate tool. Furthermore, because the drill body 1 has a groove cutting edge 4 on the outer periphery, it is possible to form a wall with an inclined angle while drilling a hole with the point cutting edge 2. By repeating this process using plunge cutting, it is possible to machine rib grooves with sufficient machining efficiency.

[0026] Here, plunge machining is a process in which holes are drilled continuously so that they slightly overlap, and the tool moves only in the Z-axis direction, as shown in Figure 3. Therefore, compared to the contour machining and reciprocating machining shown in the prior art, tool deflection can be suppressed and sufficient machining accuracy can be ensured even for a tool that machines a thin and narrow range that satisfies both D1 ≦ 2 mm and 8 ≦ L1 / D1 ≦ 20.

[0027] (Method of processing mold rib grooves) Hereinafter, a method for machining a mold rib groove using a tapered drill according to an embodiment will be described with reference to FIGS. The machining method of this embodiment is a method of forming a rib groove of a predetermined length by performing plunge machining on a solid workpiece W using the tapered drill 10 of this embodiment multiple times.

[0028] As shown in FIG. 2, a solid workpiece W is prepared, and a tapered drill 10 is moved in the −Z direction (vertically downward) relative to the top surface of the workpiece W to form a drilled hole 21 that opens onto the top surface of the workpiece W. Next, the tapered drill 10 is moved in the +Z direction (vertically upward) and withdrawn from the workpiece W. Next, as shown in FIG. 3, the tapered drill 10 is moved in the X direction, and then moved in the −Z direction to form a drilled hole 21 in the workpiece W that partially overlaps with the existing drilled hole 21.

[0029] By repeating the above drilling process, a plurality of drill holes 21 are formed in the workpiece W, as shown in Fig. 4. The plurality of drill holes 21 are connected in the X direction with adjacent drill holes 21 partially overlapping each other. As a result, a rib groove 20 consisting of the plurality of drill holes 21 is formed in the workpiece W.

[0030] According to the above-described method for machining rib grooves in a mold, deep and narrow rib grooves can be formed simply by moving the tapered drill 10 of the embodiment in the Z direction. Compared to forming rib grooves by reciprocating machining or contour machining, this method enables highly efficient machining of narrow rib grooves.

[0031] Furthermore, as shown in Figure 5, by performing finishing processing using another end mill EM on the rib groove 20 formed with the tapered drill 10, the inner wall surface of the rib groove 20 can be made even smoother, as shown in Figure 6. Although rib groove machining using the taper drill 10 of the embodiment alone can provide a machined surface with a certain degree of machining accuracy, a rib groove shape with even better machining accuracy can be obtained by additionally performing finish machining using a separate tool. Compared to forming rib grooves using only reciprocating machining or contour machining, the amount of machining required by the end mill EM can be reduced, making it easier to obtain a machined surface with high accuracy.

[0032] Furthermore, the configurations (elements) described in the above-described embodiments, modifications, and notes may be combined without departing from the spirit of the present invention, and additions, omissions, substitutions, and other modifications of the configurations are possible. Furthermore, the present invention is not limited to the above-described embodiments, but is limited only by the claims. [Explanation of symbols]

[0033] 1...Drill body, 2...Tip cutting edge, 3...Chip discharge groove, 4...Flute cutting edge, 10...Taper drill, 20...Rib groove, D...Outer diameter, D1...Minimum outer diameter, EM...End mill, L1...Flute length, O...Tool rotation center axis, T...Tool rotation direction, W...Workpiece material

Claims

1. The drill includes a tip cutting edge located at a tip end of a rod-shaped drill body extending along a tool rotation central axis, and a chip discharge groove extending along the tool rotation central axis on an outer circumferential surface of the drill body, The minimum outer diameter dimension D1 of the drill body at the tip end of the chip discharge flute and the flute length L1 of the chip discharge flute, D1≦2 mm, 8≦L1 / D1≦20, Both of the above are satisfied. a groove cutting edge located at an end of the chip discharge groove on the rear side in the tool rotation direction and extending along the chip discharge groove; the groove cutting edge has an outer diameter that increases from the front end side to the rear end side of the drill body; A tapered drill characterized by:

2. A method for machining a rib groove in a mold, comprising repeating plunge machining using the taper drill according to claim 1 to form a rib groove in a workpiece.

3. 3. The method for machining a rib groove in a mold according to claim 2, wherein the rib groove formed by the plunge machining is subjected to a finishing process using an end mill different from the tapered drill.

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