JP2018039084A - Manufacturing method of ball end mill and ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball end mill of a smaller diameter than 0.1 mm in an outer diameter.SOLUTION: A rough-processed raw material 20 is set so as to become a negative electrode and a copper system block 35 is set so as to become a positive electrode in a power source 36, and the rough-processed raw material 20 is advanced to the copper system block 35 by a movement mechanism 33 while rotating by a rotary mechanism 31, and a recess is formed in the copper system block 35 by discharge of turning to the copper system block 35 from the rough-processed raw material 20, and is formed in a hemispherical shape by melting a tip corner part of the rough-processed raw material 20 by heat from this recess.EFFECT: In discharge processing, the rough-processed raw material side is daringly set as the negative electrode, that is, the electrode side. As a result, a tip fine pillar of the rough-processed raw material is indirectly gently melted by heat on the copper system block side. Thus, a superfine ball end mill being 0.005 mm in a minimum outer diameter can be manufactured.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a technique for manufacturing a ball end mill having a tip outer diameter smaller than 0.1 mm.

  An end mill is known as a kind of milling tool. Among these end mills, those having a hemispherical (ball) tip are called ball end mills. Various methods for manufacturing this ball end mill have been proposed (see, for example, Patent Document 1 (FIGS. 3 and 5)).

The technique of Patent Document 1 will be described with reference to FIGS.
FIG. 12 is an external view of a conventional ball end mill. The ball end mill 100 is formed integrally with a shank 101, a neck portion 102 having a smaller diameter than the shank 101, and a tip portion of the neck portion 102. The chip portion 103 is included.
The outer diameter of the tool tip portion (tip portion 103) is 0.1 mm to 6.0 mm (Patent Document 1 [Claim 1]).
The ball end mill 100 having such a shape is processed by an apparatus described below.

FIG. 13 is a principle diagram of a conventional three-dimensional processing apparatus. The three-dimensional processing apparatus 110 includes a material holding mechanism 111, a laser beam irradiation mechanism 121, and a control unit 131.
The material holding mechanism 111 supports the columnar material 112 and rotates around the axis, a turning mechanism 114 that supports and rotates the rotating mechanism 113, and the rotating mechanism 113 and the turning mechanism 114 collectively in the x-axis direction. An x-axis stage 115 that moves in the y-axis direction, a y-axis stage 116 that moves in the y-axis direction, and a z-axis stage 117 that moves in the z-axis direction.

The laser light irradiation mechanism 121 includes a laser light source 122 and a galvano scanner 123.
The cylindrical material 112 is made of PCD (diamond sintered body) or the like (Patent Document 1, paragraph 0020).

Laser light is irradiated from the laser light irradiation mechanism 121 to the cylindrical material 112 held by the material holding mechanism 111. The irradiated part is melted by the laser beam.
Since the cylindrical material 112 is moved in the xyz-axis direction by the stages 115 to 117, and is swung by the turning mechanism 114 and rotated by the rotating mechanism 113, the tip is shaped into a hemisphere, and the ball end mill 100 is obtained. .

The rotation mechanism 113 and the turning mechanism 114 of Patent Document 1 are provided with a slight gap between the fixed portion and the moving portion in order to smoothly rotate and turn. This is because when the gap is 0, rotation and rotation are impossible.
In general, a gap of several μm is secured and accumulated by the rotation mechanism 113, the turning mechanism 114, and the like. In the material holding mechanism 111, the accumulated gap is about 5 μm (0.005 mm). This cumulative gap is called backlash.

The outer diameter of the tip portion 103 is 0.1 mm (minimum value). There is a possibility that the outer diameter of the tip portion 103 is finished to 0.095 mm or 0.105 mm due to the above-described play of 0.005 mm. That is, the finishing accuracy is ± 5%. The smaller the outer diameter of the tip portion 103, the worse the finishing accuracy. If the outer diameter of the tip portion 103 is 0.01 mm, the finishing accuracy is ± 50%. This accuracy is not acceptable.
For this reason, in the conventional technique, the minimum outer diameter of the ball end mill is set to 0.1 mm. That is, conventionally, the minimum outer diameter of the ball end mill has been limited to 0.1 mm.

  However, a workpiece such as a mold is required to have finer processing and higher accuracy. Therefore, a ball end mill whose outer diameter is much smaller than 0.1 mm is inevitably required.

JP-A-2006-43450

  An object of the present invention is to provide a ball end mill whose outer diameter is much smaller than 0.1 mm.

The invention according to claim 1 includes a shank, a metal column fixed to one end of the shank and having an outer diameter of 0.5 to 1.5 mm, and a sintered diamond layer integrally formed at the tip of the metal column. A method of manufacturing a ball end mill in which the tip of the sintered diamond layer is hemispherical,
A step of obtaining a rough processed material comprising the shank, the metal column, and the sintered diamond layer by forming a fine column having a minimum outer diameter of 0.005 mm on the sintered diamond layer by polishing or electric discharge machining. When,
A rotating mechanism that supports the roughly processed material while rotating, a moving mechanism that moves the roughly processed material along a rotation axis, a copper-based block that is placed stationary at the tip of the fine column, and A preparation step of preparing a rough processed material and a power source connected to the copper-based block;
With the power source, an energization step of energizing the rough-processed material as a negative electrode and the copper-based block as a positive electrode;
While maintaining this energization step, the roughing material is rotated by the rotating mechanism, the roughing material is advanced to the copper block by the moving mechanism, and the discharge is directed from the fine pillars to the copper block. And forming a recess in the copper-based block, and melting the corner portion at the tip of the fine column by heat from the recess to make a hemisphere.

The invention according to claim 2 includes a shank, a metal column fixed to one end of the shank and having an outer diameter of 0.5 to 1.5 mm, and a sintered diamond layer integrally formed at the tip of the metal column. A method of manufacturing a ball end mill in which the tip of the sintered diamond layer is hemispherical,
By forming a fine column having a minimum outer diameter of 0.02 mm on the sintered diamond layer by polishing or electric discharge machining, a first rough processed material comprising the shank, the metal column, and the sintered diamond layer is formed. Obtaining a step;
A step of obtaining a second rough processed material by forming a rough hemisphere by polishing or electric discharge machining at the tip of the first rough processed material;
A rotating mechanism for supporting the second rough processed material while rotating, a moving mechanism for moving the second rough processed material along a rotation axis, and a copper system disposed in a stationary state at the tip of the fine column Preparing a block, a power source connected to the second rough-processed material and the copper-based block;
In a non-energized state, the second roughened material is rotated by the rotating mechanism and the moving mechanism while being advanced to the copper-based block, and an initial depression is formed in the copper-based block;
An energization step of energizing the power source so that the second rough-processed material is a positive electrode and the copper-based block is a negative electrode;
While maintaining this energization process, the second rough processed material is rotated by the moving mechanism while the second rough processed material is rotated by the rotating mechanism until the tip of the fine column enters the initial recess. And a tip shaping step of shaping the rough hemisphere into a smooth hemisphere by advancing to a copper block and discharging from the copper block toward the fine column.

The invention according to claim 3 includes a shank, a metal column fixed to one end of the shank and having an outer diameter of 0.5 to 1.5 mm, and a sintered diamond layer integrally formed at the tip of the metal column. A ball end mill,
The sintered diamond layer has a fine column having an outer diameter of 0.005 to 0.02 mm at the tip, and the tip of the fine column is rounded into a hemisphere.

  In the invention according to claim 4, the sintered diamond layer has a first cone portion whose bottom surface is in contact with the metal column, a bottom surface in contact with the first cone portion, and a cone apex angle which is greater than the cone apex angle of the first cone portion. It further has a large second conical portion, and a fine column extends from the second conical portion.

  In the invention according to claim 1, in the electric discharge machining, the rough processed material side is dared to be the negative electrode, that is, the electrode side. The copper block side becomes hot. The fine column at the tip of the rough processed material is melted gently and indirectly by the heat on the copper block side. This gentle melting changes the corner of the tip of the fine column from a corner to a circle. Therefore, it is possible to manufacture an ultrafine ball end mill having a minimum outer diameter of 0.005 mm.

  In the invention which concerns on Claim 2, the front-end | tip of the fine pillar of a 1st rough processed raw material is rounded roundly. Using such a fine column as a substitute for the end mill, an initial depression is formed in the copper-based block. Next, electricity is applied so that the copper block becomes a negative electrode and the fine column becomes a positive electrode. Such fine columns are advanced while being rotated toward the copper block on the negative electrode side. The tips of the fine pillars are rounded roughly to form a polyhedral hemispherical shape and include innumerable convex portions. The protrusion becomes flat due to heat and mechanical contact. As a result, an ultrafine ball end mill having a minimum outer diameter of 0.02 mm can be manufactured.

  The invention according to claim 3 provides a ball end mill having a tip of 0.005 to 0.02 mm. The minimum radius of the conventional ball end mill is about 0.1 mm. In contrast, the ball end mill of the present invention has a significantly smaller outer diameter. With the ball end mill of the present invention, finer grooves and patterns can be formed in a mold or the like. The finishing accuracy of grooves and patterns is much better.

  In the invention which concerns on Claim 4, it connects to a metal pillar, changing an outer diameter gradually by passing through the 1st, 2nd cone part the fine pillar of a minute diameter (0.005-0.02 mm). Since sudden changes in the cross-sectional area can be avoided, stress concentration can be relaxed and the life of the ball end mill can be extended.

It is a figure explaining the process of obtaining the rough-processed raw material which concerns on this invention. FIG. 2 is an enlarged view of part 2 of FIG. It is a principle diagram of the electric discharge machining apparatus prepared for the first method. It is a figure explaining the tip shaping process concerning the 1st method. It is an external view of the ball end mill obtained by the first method. It is a principle figure of the electric discharge machining apparatus prepared for the 2nd method. It is a figure explaining the shape of the 1st rough processed raw material which concerns on a 2nd method. It is a figure explaining the shape of the 2nd rough processed raw material which concerns on a 2nd method. It is a figure explaining the initial stage hollow formation process and tip shaping process which concern on a 2nd method. It is a comparison figure of a prior art and an Example. It is a figure explaining another form of an Example. It is an external view of the conventional ball end mill. It is a principle figure of the conventional three-dimensional processing apparatus.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.

The first method will be described with reference to FIGS.
As shown in FIG. 1 (a), a multilayer plate 10 comprising a metal plate 11 made of cemented carbide or tool steel and a sintered diamond layer 12 laminated on the metal plate 11 is prepared. Sintered diamond constituting the sintered diamond layer 12 is an abbreviation for PCD (Polycrystalline Diamond), and is formed by sintering fine crystals of diamond at high pressure and high temperature.
The thickness t1 of the metal plate 11 is 5 to 13 mm, the thickness t2 of the sintered diamond layer 12 is 0.5 to 2.0 mm, and the thickness T of the multilayer plate 10 is (t1 + t2). 5.5 to 15 mm is preferable.

The cylindrical member 15 is cut out from the multilayer plate 10 by wire cut electric discharge machining. The outer diameter D of the cylindrical member 15 shown in FIG. 1B is preferably 0.5 to 1.5 mm. That is, the cylindrical member 15 includes a metal column 16 having an outer diameter D and a sintered diamond layer 12 attached to the tip of the metal column 16.
As shown in FIG. 1C, the columnar material 15 is brazed and fixed to the tip of the shank 17.
As shown in FIG.1 (d), the rough-processed raw material 20 is obtained by roughening the front-end | tip of the columnar material 15 by grinding | polishing etc. As shown in FIG.

The main part of FIG.1 (d) is expanded and it shows in FIG.
As shown in FIG. 2, in the rough-processed material 20, the sintered diamond layer 12 at the tip is tapered from the metal pillar 16 having an outer diameter D to the first cone portion 21 and the second cone portion 22, A fine pillar 23 having an outer diameter d and a length L is formed at the tip of the second conical portion 22. The minimum value of d is 0.005 mm. L is set to several times d. In addition, d should just be 0.005 mm in the minimum value, and can be selected from the range of 0.005-0.02 mm.

  The cone apex angle θ2 of the second cone portion 22 is set larger than the cone apex angle θ1 of the first cone portion 21.

The rough processed material 20 described above is subjected to electric discharge machining. Next, a basic configuration of the electric discharge machining apparatus 30 used for the electric discharge machining will be described.
As shown in FIG. 3, the electric discharge machining apparatus 30 includes a rotation mechanism 31 that rotatably supports the rough-processed material 20, a moving mechanism 33 that moves the rotation mechanism 31 along the rotation axis 32, and a rough-processed material. 20 (front, lower in the figure), a copper-based block 35, a power supply 36 for energizing the copper-based block 35 and the rough processed material 20, and a machining fluid supply mechanism for supplying a machining fluid 37 38. Here, the positive electrode and the negative electrode are set so that the rough-processed material 20 becomes the negative electrode (−) and the copper-based block 35 becomes the positive electrode (+). The copper block 35 is fixed to the table and is in a stationary state.

  The copper-based block 35 may be pure copper, copper tungsten, tellurium copper, tough pitch copper, or the like. The copper block 35 may be an electrode used for electric discharge machining, for example, tungsten or graphite.

The principle of the electric discharge machining method will be described next.
In FIG. 3, the coarsely processed material 20 is advanced to the copper block 35 by the moving mechanism 33 while rotating the coarsely processed material 20 at a speed of several hundred revolutions per minute by the rotation mechanism 31. The machining liquid 37 is filled with the machining liquid supply mechanism 38 between the copper-based block 35 and the rough-processed material 20.

  As shown in FIG. 4A, a discharge 39 is formed from the tip of the fine column 23 of the rough processed material 20 to the upper surface of the copper-based block 35. Due to the discharge 39, the upper surface of the copper block 35 becomes high temperature.

  As shown in FIG. 4B, a disk-like depression 41 is formed on the upper surface of the copper-based block 35 by the discharge 39. The upper surface of the copper-based block 35 is heated to a high temperature. The fine pillars 23 are heated on the upper surface of the copper-based block 35. At this time, the front surface (lower surface) 23a of the fine column 23 is heated by the upward heat 42 (one surface heating). On the other hand, the corner portion 23b where the front surface and the side surface intersect is heated by the upward heat 43 and the lateral heat 44 (two-surface heating). Since the corner portion 23b has a higher temperature than the front surface 23a, the corner portion 23b is greatly melted.

As a result, as shown in FIG.4 (c), the corner part 23b of the fine pillar 23 begins to become round. The recess 41 also has a rounded shape. The corner portion 23b of the fine pillar 23 is further rounded.
As shown in FIG. 4D, the corner portion 23b of the fine column 23 is further rounded.
As shown in FIG. 4 (e), when the tip of the fine column 23 enters the copper block 35 at a depth 1.0 to 2.0 times the outer diameter of the fine column 23, the tip of the fine column 23 is Becomes hemispherical.

As shown in FIG. 5A, the ball end mill 50 including the fine columns 23 is raised. A deep recess 41 remains in the copper block 35.
As shown in FIG. 5B, the obtained ball end mill 50 includes a shank 17, a metal column 16 that is fixed to one end of the shank 17 and has an outer diameter of 0.5 to 1.5 mm, and the metal column. And a sintered diamond layer 12 integrally formed at the tip of 16.
The sintered diamond layer 12 includes a fine column 23 having an outer diameter d of 0.005 to 0.02 mm at the tip, and the tip of the fine column 23 is rounded into a hemisphere.

  The ball end mill according to the prior art has a minimum outer diameter of 0.1 mm at the tip. On the other hand, the ball end mill 50 according to the present invention has a minimum outer diameter of 0.005 mm at the tip, and therefore can be used for finer finishing. Fine grooves and patterns can be formed by a mold or the like, and the finished accuracy of the formed grooves and patterns is greatly improved.

  Preferably, as shown in FIG. 5A, the sintered diamond layer 12 includes a first conical portion 21 whose bottom surface is in contact with the metal column 16, a bottom surface that is in contact with the first conical portion 21, and a first conical portion 21. And a second conical portion 22 having a conical apex angle θ2 larger than the conical apex angle θ1, and a fine column 23 extends from the second conical portion 22. An external force (such as a polishing resistance force) acting on the fine column 23 is dispersed by the second cone portion 22, further dispersed by the first cone portion 21, and transmitted to the metal column 16. That is, the concentration of stress generated due to a sudden change in the cross section is greatly reduced by adopting the structure shown in FIG. This relaxation extends the life of the ball end mill 50.

The manufacturing method (first method) of the ball end mill 50 described above is summarized as follows.
As shown in FIG.1 (d), by forming the fine pillar (FIG. 2, code | symbol 23) whose outer diameter d is 0.005-0.02 mm to the sintered diamond layer 12 by grinding | polishing or electric discharge machining, A step of obtaining a rough processed material 20 composed of the shank 17, the metal pillar 16 and the sintered diamond layer 12 is performed.

As shown in FIG. 3, a rotation mechanism 31 that supports the rough processed material 20 while rotating it, a moving mechanism 33 that moves the rough processed material 20 along the rotation axis 32, and a fine column (rough processed material 20 ) And a power source 36 connected to the rough-processed material 20 and the copper block 35 are prepared (preparation step).
Then, an energization process is performed with the power source 36 so that the rough-processed material 20 is a negative electrode (−) and the copper-based block 35 is a positive electrode (+).

While the rough processed material 20 is rotated by the rotation mechanism 31, the rough processed material 20 is advanced to the copper block 35 by the moving mechanism 33.
Then, as shown in FIGS. 4A to 4E, a recess 41 is formed in the copper-based block 35 by the discharge 39 from the fine pillars 23 toward the copper-based block 35, and heats 43 and 44 from the recess 41 are formed. As shown in FIG. 5B, the outer diameter d of the tip is 0.005 to 0.02 mm by performing the tip shaping step by melting the corner portion 23b of the tip of the fine column 23 to make a hemisphere. A ball end mill 50 is manufactured.

  Incidentally, as a standard method of using the power supply 36, the copper-based block 35 shown in FIG. Since the discharge is directed from the copper-based block 35 to the rough-processed material 20, the copper-based block 35 is not worn much, and the rough-processed material 20 is actively melted.

In contrast, in the present invention (first method), the copper block 35 is used as the positive electrode, and the rough-processed material 20 is used as the negative electrode.
The reason for this is that the outer diameter of the fine column 23 is as small as 0.005 to 0.02 mm, and with normal heat input, the fine column 23 is melted and melted before becoming hemispherical. Will progress. By making the rough-processed raw material 20 into a negative electrode like this invention, the copper-type block 35 was heated by discharge, and the fine pillar 23 was heated indirectly with this heat. Since the fine column 23 is melted gently, the corner 23b at the tip of the ultrafine fine column 23 having an outer diameter of 0.005 to 0.02 mm was melted to make the tip hemispherical.

On the other hand, when the outer diameter of the fine column 23 exceeds 0.02 mm, problems such as the tip of the fine column 23 not being properly formed into a hemisphere or a long processing time occur.
Therefore, another processing method (second method) is provided for a ball end mill having an outer diameter of the fine column 23 of 0.02 to 0.05 mm.

The second method will be described with reference to FIGS.
The electric discharge machining apparatus 30B used in the second method is different from the electric discharge machining apparatus 30 shown in FIG. 3 in the following points, and the other parts are the same. Therefore, the reference numerals of the electric discharge machining apparatus 30 are used for the same components. Detailed description will be omitted.
As shown in FIG. 6, the positive electrode of the power source 36 is connected to the second rough processed material 20 </ b> B, and the negative electrode of the power source 36 is connected to the copper-based block 35. A second rough processed material 20B is attached to the rotation mechanism 31.

The second rough processed material 20B is obtained by processing the first rough processed material 20A.
The first roughly processed material 20A shown in FIG. 7A is a material manufactured by the procedure of FIGS. 1A to 1C, like the processed material 20 shown in FIG.

  As shown in FIG. 7B, which is an enlarged view of a portion b in FIG. 7A, the sintered diamond layer 12 is integrally formed on the metal column 16. The outer diameter d2 of the fine column 23 formed at the tip of the sintered diamond layer 12 is 0.02 to 0.05 mm, which is larger than the outer diameter d (0.005 to 0.02 mm) in FIG. is there. Therefore, the metal pillar 16 and the fine pillar 23 can be connected by one conical portion. Of course, the metal pillar 16 and the fine pillar 23 may be connected by a plurality of conical portions. Or it is good also considering the metal pillar 16 and the sintered diamond layer 12 as an elongate cone part as a whole. In this case, the fine column 23 is not a cylinder but a conical column with a small taper angle.

Further roughing is performed on the tip of the first rough processed material 20A by polishing or electric discharge machining.
The obtained second rough-processed material 20B is shown in FIG. 8A, and the tip of the fine column 23 is shown in FIG. 8B, which is an enlarged view of the b part in FIG. 8A. Round the tip roughly. Because it is rough, it looks like a polygon (polyhedral hemisphere). A convex portion 23c is formed at the boundary between the surfaces.

  As shown in FIG. 9A, the second rough-processed material 20B that rotates at a speed of several hundreds of revolutions per minute is advanced to a stationary copper-based block 35 without being energized. Since the convex portion 23c of the fine column 23 serves as a blade and the fine column 23 serves as an end mill, an initial depression 41P is formed in the copper block 35 as shown in FIG. 9B. The initial recess 41P is a recess in the previous stage of the recess 41 in the post process.

  As shown in FIG. 9C, the second rough processed material 20B is moved backward. The initial depression 41P remains in the copper block 35. When the second rough processed material 20B is retracted, the space between the initial depression 41P and the fine pillars 23 is widened, and the processing liquid 37 can be easily and satisfactorily supplied thereto.

As shown in FIG. 9D, the second roughing material 20 </ b> B is advanced while supplying the machining liquid 37 and energizing the copper-based block 35 to be a negative electrode and the fine column 23 to be a positive electrode. Then, a discharge 39 is formed from the copper-based block 35 to the fine pillars 23. Since discharge tends to concentrate on the convex part 23c, the convex part 23c becomes hotter than other parts.
The fine column 23 is rotated while being continuously advanced. The convex portion 23c is mechanically brought into contact with the initial depression 41P to be rounded and melted by heat to be rounded. The convex portion 23c is rounded by a synergistic effect of mechanical grinding and heat melting. During this time, the initial depression 41P is also rounded into a depression (FIG. 9 (e), reference numeral 41).

As a result, as shown in FIG. 9 (e), the tip of the fine column 23 has a smoothed hemispherical shape.
The obtained ball end mill 50B includes a shank 17, a metal column 16 having an outer diameter of 0.5 to 1.5 mm, and a diamond layer 12, as shown in FIG. A fine column 23 having an outer diameter d2 of 0.02 to 0.05 mm is provided at the tip, and the tip of the fine column 23 is shaped into a hemisphere.

The manufacturing method (second method) of the ball end mill 50B described above is summarized as follows.
As shown in FIG. 7B, by forming the fine pillars 23 having an outer diameter d2 of 0.02 to 0.05 mm on the sintered diamond layer 12 by polishing or electric discharge machining, the result shown in FIG. A step of obtaining a first rough-processed material 20A composed of the shank 17, the metal column 16, and the sintered diamond layer 12 as shown is performed.

  A rough hemisphere as shown in FIG. 8B is formed at the tip of the first rough processed material 20A by polishing or electric discharge machining to obtain a second rough processed material 20B shown in FIG. Perform the process.

  As shown in FIG. 6, a rotation mechanism 31 that supports the second rough processed material 20 </ b> B while rotating, a moving mechanism 33 that moves the second rough processed material 20 </ b> B along the rotation axis 32, and the fine columns 23. A copper-based block 35 disposed in a stationary state ahead, a second rough processed material 20B, and a power source 36 connected to the copper-based block 35 are prepared (preparation step).

In the non-energized state, as shown in FIG. 9A, the second rough-processed material 20B is advanced to the copper block 35 while being rotated by the rotating mechanism and the moving mechanism, as shown in FIG. 9B. The initial depression 41P is formed in the copper block 35.
Next, as shown in FIG. 9C, the power source is energized so that the second rough processed material 20B becomes a positive electrode and the copper-based block 35 becomes a negative electrode (energization process).

While maintaining this energization process, as shown in FIG. 9D, the second rough processed material 20B is rotated by the moving mechanism while the second rough processed material 20B is rotated by the moving mechanism, and the tip of the fine column 23 is moved. It advances to the copper-type block 35 until it enters into the initial hollow 41P. By the discharge 39 from the copper block 35 toward the fine pillars 23, the projections 23c are melted, and the projections 23c are mechanically contacted with the walls of the initial depressions 41P and flattened. In this way, the rough hemisphere at the tip of the fine column 23 is gradually smoothed. As shown in FIG. 9E, the tip of the fine column 23 is shaped into a smooth hemisphere (tip shaping step).
As a result, as shown in FIG. 9F, a ball end mill 50B having an outer diameter d of 0.02 to 0.05 mm at the tip is obtained.

  In the second method, the initial depression 41P is formed in advance, and the tip is discharged between the multi-columnar fine column 23 and the initial depression 41P. Therefore, a more accurate finished shape can be obtained than in the first method. On the other hand, in the second method, the minimum outer diameter is 0.02 mm.

The method for manufacturing the ball end mill (first method and second method) has been described above. These methods are compared with the prior art based on the outer diameter of the tip.
As shown in FIG. 10, in the comparative example based on the conventional technique, the outer diameter of the tip of the ball end mill was 0.1 to 6.0 mm.
On the other hand, in Example 2 based on the second method, the minimum outer diameter of the tip of the ball end mill was 0.02 mm, and the outer diameter of the tip was 0.02 to 0.05 mm. According to the second embodiment, a ball end mill 50B having an outer diameter sufficiently smaller than 0.1 mm can be obtained.

  Furthermore, in Example 1 based on the first method, the minimum outer diameter of the tip of the ball end mill was 0.005 mm, and the outer diameter of the tip was 0.005 to 0.02 mm. According to Example 1, a ball end mill 50 having an outer diameter much smaller than 0.1 mm can be obtained.

As a result of the experiment, in the first method, if the extension of the processing time was allowed, the outer diameter could be processed to 0.05 mm. Also in the second method, processing was possible until the outer diameter was less than 0.1 mm.
Therefore, as shown in FIG. 11, according to the first method, a ball end mill 50 having a minimum outer diameter of 0.005 mm and an outer diameter of 0.005 to 0.05 mm is obtained.
According to the second method, a ball end mill 50B having a minimum outer diameter of 0.02 mm and an outer diameter of 0.02 to less than 0.1 mm is obtained.

  The present invention is suitable for a ball end mill having an outer diameter smaller than 0.01 mm.

  DESCRIPTION OF SYMBOLS 12 ... Sintered diamond layer, 16 ... Metal pillar, 17 ... Shank, 20 ... Rough processed material, 20A ... 1st rough processed material, 20B ... 2nd rough processed material, 21 ... 1st cone part, 22 ... 2nd cone part, 23 ... fine pillar, 23b ... corner part, 23c ... convex part which exists in rough hemisphere, 30 ... electric discharge machining apparatus used for the first method, 30B ... electric discharge machining apparatus used for the second method, 31 ... rotating mechanism, 32 ... rotating shaft, 33 ... moving mechanism, 35 ... copper block, 36 ... power supply, 39 ... discharge, 41 ... depression, 41P ... initial depression, 50, 50B ... ball end mill, D ... outside metal pillar Diameter, d1, d2 ... outer diameter of the fine column, θ1 ... cone apex angle of the first conical part, θ2 ... cone apex angle of the second conical part.

Claims (4)

A shank, a metal column fixed to one end of the shank and having an outer diameter of 0.5 to 1.5 mm, and a sintered diamond layer integrally formed at the tip of the metal column. A method for manufacturing a ball end mill having a hemispherical tip,
A step of obtaining a rough processed material comprising the shank, the metal column, and the sintered diamond layer by forming a fine column having a minimum outer diameter of 0.005 mm on the sintered diamond layer by polishing or electric discharge machining. When,
A rotating mechanism that supports the roughly processed material while rotating, a moving mechanism that moves the roughly processed material along a rotation axis, a copper-based block that is placed stationary at the tip of the fine column, and A preparation step of preparing a rough processed material and a power source connected to the copper-based block;
With the power source, an energization step of energizing the rough-processed material as a negative electrode and the copper-based block as a positive electrode;
While maintaining this energization step, the roughing material is rotated by the rotating mechanism, the roughing material is advanced to the copper block by the moving mechanism, and the discharge is directed from the fine pillars to the copper block. Thus, a method of manufacturing a ball end mill comprising: forming a recess in the copper-based block, and melting the corner portion at the tip of the fine column with heat from the recess to make a hemisphere. A shank, a metal column fixed to one end of the shank and having an outer diameter of 0.5 to 1.5 mm, and a sintered diamond layer integrally formed at the tip of the metal column. A method for manufacturing a ball end mill having a hemispherical tip,
By forming a fine column having a minimum outer diameter of 0.02 mm on the sintered diamond layer by polishing or electric discharge machining, a first rough processed material comprising the shank, the metal column, and the sintered diamond layer is formed. Obtaining a step;
A step of obtaining a second rough processed material by forming a rough hemisphere by polishing or electric discharge machining at the tip of the first rough processed material;
A rotating mechanism for supporting the second rough processed material while rotating, a moving mechanism for moving the second rough processed material along a rotation axis, and a copper system disposed in a stationary state at the tip of the fine column Preparing a block, a power source connected to the second rough-processed material and the copper-based block;
In a non-energized state, the second roughened material is rotated by the rotating mechanism and the moving mechanism while being advanced to the copper-based block, and an initial depression is formed in the copper-based block;
An energization step of energizing the power source so that the second rough-processed material is a positive electrode and the copper-based block is a negative electrode;
While maintaining this energization process, the second rough processed material is rotated by the moving mechanism while the second rough processed material is rotated by the rotating mechanism until the tip of the fine column enters the initial recess. A ball end mill manufacturing method comprising: a tip shaping step of shaping the rough hemisphere into a smooth hemisphere by advancing to a copper block and discharging from the copper block toward the fine column. A ball end mill comprising a shank, a metal column fixed to one end of the shank and having an outer diameter of 0.5 to 1.5 mm, and a sintered diamond layer integrally formed at the tip of the metal column,
The sintered diamond layer includes a fine column having an outer diameter of 0.005 to 0.02 mm at a tip, and the tip of the fine column is rounded into a hemisphere.   The sintered diamond layer includes a first conical portion whose bottom surface is in contact with the metal column, and a second conical portion whose bottom surface is in contact with the first conical portion and whose cone apex angle is larger than the cone apex angle of the first conical portion. 4. The ball end mill according to claim 3, wherein the fine column extends from the second conical portion.

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