JPH0451929Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field of application> The present invention relates to a ball end mill, in particular, avoids chipping of the bottom cutting edge, improves the transverse rupture strength of the cutting edge, and improves the processing range. Expand the
This invention relates to a ball end mill that not only improves workability and productivity, but also has excellent machining accuracy and can significantly extend tool life.

<Prior Art> Conventionally, ball end mills have been used for engraving molds, etc., but they have the drawback of being susceptible to chipping, mainly due to the material of the cutting blades.

That is, the bottom cutting edge of a conventional ball end mill is generally made of a cemented carbide with excellent wear resistance, which is the same as the peripheral cutting edge, for reasons of tool manufacturing and cutting.

By the way, near the center of the shaft where the bottom cutting edge is provided, the circumferential speed is relatively slow and the center is stationary, and the cutting temperature, that is, the temperature of the cutting edge and the temperature of the workpiece surface, are low, so the recrystallization temperature of the workpiece material is low. Not only does a built-up edge occur, but the generated built-up edge grows and is difficult to fall off, so it tends to grow further and increase in size.

As a result, the surface to be cut is not only damaged, but also the properties of the surface are damaged, and the dimensional accuracy is also deteriorated.

Further, when the above-mentioned structured cutting edge falls off, an external force is applied to the cutting edge as an impact force, and if the external force is greater than the transverse rupture force of the cutting edge, the cutting edge will chip (chip). In particular, as the cycle of generation, growth, splitting, and shedding of the built-up cutting edge is repeated continuously, fatigue occurs at the tip of the cutting edge, and even small damage quickly develops into a large one, making it extremely easy to break. There are drawbacks.

Therefore, due to these drawbacks, the cutting speed and feed rate are restricted, resulting in not only low productivity but also poor machining accuracy of the cutting surface, and short tool life.

Therefore, in order to solve these problems, the leading edge is made of a tool material for low-speed cutting (e.g. tough ultra-fine grain cemented carbide alloy or high-speed steel), and the outer edge is made of a tool material for high-speed cutting (e.g. ultra-fine grain carbide). An alloy (alloy or conventional cemented carbide) was proposed (Utility Model Application Publication No. 1977-775). However, this is a series connection between the leading edge and the peripheral cutting edge, which use different tool materials, and the cutting edge materials differ at one point, so the rotation speed within a specific range (e.g. Even if it can be used at rotation speeds (near 1000 rotations), the initial objective cannot be achieved at rotation speeds outside the specified range because the cutting speed is outside the setting conditions that should be applied to the tool material. It is something that exists.

<Problems to be solved by the invention> In view of these shortcomings of the prior art, the main purpose of the present invention is to improve the cutting speed near the shaft center, thereby preventing the formation of a built-up edge at that location. It suppresses growth, prevents breakage of the cutting edge due to falling off of the built-up cutting edge, allows for better cutting, can handle a wide range of rotation speeds, and significantly reduces cutting resistance, making heavy cutting possible. Increased versatility for workpiece materials, high productivity,
Moreover, it is an object of the present invention to provide a ball end mill that has excellent machining accuracy and can further extend tool life.

<Means for solving the problem> According to the present invention, the bottom cutting edge is made of M30, which is a tough cemented carbide among the cemented carbide for general cutting tools, and the peripheral cutting edge is is a highly wear-resistant cemented carbide among the cemented carbide alloys for general cutting tools.
Made of M2M20, and the distance between the ends of the bottom cutting blade is approximately 70% to 90% of the diameter of the ball end mill body.
and the distance between the starting ends of the peripheral cutting blade is about 60% to 80% of the diameter of the ball end mill body, and the terminal end of the bottom cutting blade and the starting end of the peripheral cutting blade are on the rotation trajectory. This is achieved by providing a ball end mill characterized in that the diameter of the ball end mill body overlaps in the radial direction by approximately 5% to 20% of the diameter of the ball end mill body.

<Function> In this way, the materials of the bottom cutting edge and the peripheral cutting edge are made of M30, which is a tough cemented carbide that is the optimal material, depending on the conditions at the time of cutting, and the material of the peripheral cutting edge is used for general cutting tools. It is a highly wear-resistant cemented carbide among the cemented carbide used for
Adopted from M20, the transverse rupture force of the bottom cutting edge is improved, the peripheral speed near the shaft center is increased, and the cutting temperature is increased to suppress the formation and growth of built-up edges. Therefore, damage to the bottom cutting edge due to the falling of the cutting edge can be prevented. Furthermore, despite the increase in cutting speed, the wear resistance of the peripheral cutting edge is improved, making it possible to cut a wide range of work materials without breaking or damaging the cutting edge.

Moreover, since the terminal end of the bottom cutting blade and the starting end of the peripheral cutting blade are configured to overlap in the radial direction by approximately 5% to 20% of the diameter of the ball end mill body on the rotation locus, a specific rotation speed can be achieved. It is possible to handle a wide range of rotational speeds without being limited to , and it is also possible to significantly reduce cutting resistance, making heavy cutting possible and expanding versatility with respect to workpiece materials. Therefore, cutting speed and feed rate can be significantly increased, increasing machining speed,
Not only can productivity be greatly improved, but machining accuracy can also be significantly improved, and tool life can be significantly extended.

In addition, without extending the ends of the bottom cutting blades to the outer periphery of the ball end mill body, the distance between the ends of the bottom cutting blades is approximately 70 mm of the diameter of the ball end mill body.
% to 90%, the difference in circumferential speed between the starting end and the ending end of the bottom cutting blade is possible compared to when the end of the bottom cutting blade extends to the outer periphery of the ball end mill body. This not only reduces the load applied to the entire bottom cutting blade, but also reduces the difference in the load applied to each part of the bottom cutting blade, reducing the stress acting on the bottom cutting blade.

Furthermore, without extending the starting ends of the peripheral cutting blades to the vicinity of the center of the ball end mill body, the distance between the starting ends of the peripheral cutting blades is approximately 60% of the diameter of the ball end mill body.
~ 805, it is possible to create a difference in the circumferential speed between the starting end and the end of the peripheral cutting blade compared to when the starting end of the peripheral cutting blade extends to the vicinity of the center of the ball end mill body. This not only reduces the load applied to the entire circumferential cutting edge, but also reduces the difference in the loads applied to each part of the circumferential cutting edge, reducing the stress acting on the circumferential cutting edge.

Therefore, the tool life is extended and the chances of tool replacement are significantly reduced, resulting in improved productivity.

In addition, by adopting a configuration in which the distance between the terminal ends of the bottom cutting blade and the distance between the starting ends of the peripheral cutting blade are set to a predetermined length, it can be used over a wide range of rotation speeds, and can be used at any cutting speed. Also, stress concentration can be avoided, the strength of the cutting edge can be improved, and productivity and machining accuracy can be improved.

On the other hand, when the bottom cutting edge and the circumferential cutting edge are aligned on a straight line and joined together as in the conventional example, stress concentration occurs at the joint, and the bottom cutting edge and the circumferential cutting edge may peel or break. , not only each blade is destroyed;
There is a problem in that the work material is also damaged. However, in the present invention, the terminal end of the bottom cutting blade and the starting end of the peripheral cutting blade are approximately 5 times the diameter of the ball end mill main body on the rotation trajectory.
%~20% overlap in the radial direction, so the material of the cutting edge does not change suddenly and coexists over a specified length, dispersing stress and avoiding stress concentration. It is possible to solve the above problem. Therefore, it can contribute to extending tool life, and by increasing the cutting speed and feed rate, it is possible to perform heavy cutting and expand the machining range, as well as being able to handle a wide range of rotation speeds. , enables heavy cutting, expands versatility with respect to workpiece materials, and contributes to improved productivity.

<Embodiments> The present invention will now be described in detail with reference to specific embodiments with reference to the accompanying drawings.

In Figures 1 and 2, ball end mill 1
The ball end mill main body 3 has a shank 2 at the rear end, and the tip 4 of the ball end mill body 3 is formed into a hemispherical shape.

The tip portion 4 is provided with a pair of bottom cutting blade tip pockets 5 and a peripheral cutting blade tip pocket 6 facing each other in the intersecting direction when viewed from the bottom.

A bottom cutting blade tip 7 is fixed to the rear side of the bottom cutting blade tip pocket 5 in the rotational direction by means such as brazing, and a peripheral cutting blade tip 7 is fixed to the rotational direction rear side of the peripheral cutting blade tip pocket 6. A chip 8 for use is fixed by means such as brazing.

The bottom cutting edge tip 7 has a bottom cutting edge 9 at the tip in the rotational direction.

The bottom cutting blade 9 has a starting end 9a near the center of rotation (axis center) when viewed from the bottom, and is formed into an arc shape with a radius of curvature R that can cut the workpiece while making point contact with the workpiece. , the radius R is substantially the same over the entire length of the circular arc, and the curve is convex in the direction of rotation. Further, the blade 9 has a starting end 9a and a terminal end 9b located on the same radiation line from the shaft center, and a distance Le between the terminal ends 9b is approximately 80% of the diameter D of the ball end mill body 3. Moreover, it is formed in a circular arc shape, with the tip end (apex) of the blade 9 in the rotational direction located in the vicinity of 1/2 circle of the diameter D of the ball end mill main body 3. The above radius of curvature R is
Approximately 25% to 75% of the diameter D of the ball end mill body 3
(1/4 to 3/4), and this may be changed depending on the material of the workpiece, the material of the bottom cutting edge 9, and other conditions.

On the other hand, the circumferential cutting edge tip 8 has a circumferential cutting edge 10 at its tip.

The circumferential cutting blade 10 has a distance Lr between the starting ends 10a in the vicinity of about 70% of the diameter D of the ball end mill main body 3 when viewed from the bottom, and a terminal end 10b on the outer periphery of the ball end mill main body 3. It is located at the rear in the rotational direction from the radial line from the center of the shaft, and is formed at a right-handed helix angle (positive rake angle) in which the terminal end 10b is located at the rear of the starting end 10a in side view, as clearly shown in Fig. 1. has been done.

Therefore, the terminal end of the bottom cutting blade 9 and the starting end of the peripheral cutting blade 10 are in a state in which they overlap (Lo) in the radial direction by about 5% of the diameter D of the ball end mill main body 3 on the rotation locus. is formed.

The tip 7 for the bottom cutting edge and the tip 8 for the peripheral cutting edge are as follows:
Made from a cemented carbide material for general cutting tools whose main component is tungsten carbide (WC).

Among these, tip 7 for the bottom cutting blade (therefore bottom cutting blade 9)
is made from M30 (international standard ISO classification), which is a tough cemented carbide among the cemented carbide for general cutting tools, in order to increase the cutting speed by increasing the circumferential speed near the center of the shaft.

Also, the tip 8 for the peripheral cutting blade (therefore, the peripheral cutting blade 10)
Since the circumferential speed is high compared to the center of the shaft, it is made of M20 (international standard ISO classification), which is a strong wear-resistant cemented carbide among general cutting tool cemented carbides, so that it can withstand high-speed cutting. ing.

As mentioned above, the material of the bottom cutting edge 9 is M30, which is a tough cemented carbide, and the material of the peripheral cutting edge 10 is M20, which is a strong wear-resistant cemented carbide, so that the transverse rupture force can be reduced. Since it is relatively large, it is possible to significantly increase the circumferential speed near the shaft center where the bottom cutting edge 9 is installed, which increases the cutting temperature, that is, the temperature of the cutting edge and the cutting surface temperature, and improves the regeneration of the workpiece. By setting the temperature above the crystallization temperature, the generation and growth of built-up edges can be suppressed.

As a result, not only is the occurrence of a built-up edge at the tip of the bottom cutting blade 9 significantly reduced, but even if the edge is formed, it will fall off in an ungrown and minute state due to softening, so when it falls off, The influence of external force on the tip of the blade 9 is slight;
This prevents tip loss.

Furthermore, by using the above-mentioned material as the material of the bottom cutting edge 9, the refracting force of the bottom cutting edge 9 is also increased, and the resistance force against external force applied to the bottom cutting edge 9 when it falls off is also improved. Together with the rise, the tip of the bottom cutting blade 9 is prevented from being damaged when the cutting edge falls off.

In this example, it is shown that the end 9b of the bottom cutting edge 9 is approximately 80% of the diameter D of the ball end mill body 3, which is optimal for tool manufacturing and work material processing. However, the diameter of the same body is approximately 70
% to around 90% is also suitable.

Similarly, the starting end 10a of the circumferential cutting edge 10 is optimally located at around 70% of the main body diameter D in this embodiment, but is not limited to this, and is approximately 60% of the main body diameter D. % to approximately 80% is also suitable.

In each of the above-mentioned embodiments, the terminal end of the bottom cutting edge 9 and the starting end of the peripheral cutting edge 10 are often formed to overlap in the radial direction on the rotation locus, so that cutting is difficult. This improves the accuracy of the machined surface.

Further, in this embodiment, the tips 7 and 8 are fixed to the ball end mill body 3 with brazing, but the tips 7 and 8 are
may be detachably attached to the main body 3 using a crank bolt or the like (throw-away type).

Furthermore, in this embodiment, the bottom cutting edge 9 and the circumferential cutting edge 10 are each of the two-blade type, but the cutting blades 9 and 10 may be of the single-blade type or three-blade type. It can also be applied to a multi-blade type with more than a blade, and as in this embodiment, the bottom cutting blade 9 and the peripheral cutting blade 10 can be provided in pairs facing each other in the intersecting direction when viewed from the bottom. .

Furthermore, in this embodiment, the starting end 9a of the bottom cutting blade 9
Although this is applied to a ball end mill that is slightly spaced apart from the axial center of the main body 3, it may also be a ball end mill that is coincident with the coaxial center.

Further, in this embodiment, each circumferential cutting edge 9 was formed point-symmetrically with respect to the axial center of the ball end mill main body 3, but it was applied to one in which each circumferential cutting edge 9 was formed eccentrically with respect to the coaxial center. You can.

Furthermore, in this embodiment, the terminal end 9b of the bottom cutting blade 9
Although the ball end mill body 3 is positioned inside the diameter D of the ball end mill body 3, the present invention can also be applied to a machine in which the terminal end 9b extends to the outer periphery of the body 3.

Next, an experimental example of this embodiment will be explained.

A comparative cutting test between the conventional example and this example was conducted using a rigid milling machine with the following tool specifications and work material specifications.

(1) Tool specifications Diameter of ball end mill: D=50mm Conventional radius of curvature: r=50mm Curvature radius of this example: R=50mm Distance between bottom cutting edge starting end and shaft center: 1=1mm Bottom cutting blade type: 2-blade type Peripheral cutting blade type: 2-flute type Installing the tip for the bottom cutting blade: Fixing with brazing Material of conventional bottom cutting edge and peripheral cutting edge: Cemented carbide M20 Material of bottom cutting blade in this example: Cemented carbide M30 Material of peripheral cutting edge in this example: Cemented carbide M20 (2) Work material specifications Material: FC−25 The results of the above cutting test are as follows.

Cutting speed Feed Tool life (m/min) (mm/rev) This example 160 1700 2 Conventional example 126 700 1 From the results of the cutting test above, this example
It was found that the circumferential speed near the shaft center increased, the cutting temperature increased, and the feed amount increased compared to the conventional example. As a result, the generation and growth of a built-up cutting edge at the tip of the bottom cutting edge 9 is suppressed, preventing the tip of the bottom cutting blade 9 from falling off due to the cutting edge falling off, and furthermore preventing the peripheral cutting edge 10 from being damaged due to breakage. be done. Therefore, not only the tool life is extended, but also the productivity is improved, and the accuracy of the cut surface can also be improved.

<Effects of the invention> As described above, according to the invention, the material of the bottom cutting blade and the peripheral cutting blade are M30, which is a tough cemented carbide, which is the optimal material, and the peripheral cutting blade is used for general cutting tools. M20, which is a highly wear-resistant cemented carbide, is used to improve the transverse rupture strength of the bottom cutting edge, as well as increase the circumferential speed near the shaft center and increase the cutting temperature. It is possible to suppress the generation and growth of a built-up cutting edge during cutting, thereby preventing damage to the bottom cutting edge.

Moreover, since the terminal end of the bottom cutting blade and the starting end of the peripheral cutting blade are configured to overlap in the radial direction by about 5% to 20% of the diameter of the ball end mill body on the rotation locus, It is possible to handle a wide range of rotational speeds without being limited, and furthermore, cutting resistance can be significantly reduced, heavy cutting is possible, and versatility with respect to workpiece materials can be expanded. Therefore, cutting speed and feed rate can be significantly increased, machining speed can be increased, productivity can be improved, and machining accuracy can also be improved.

In addition, despite the increase in circumferential speed near the outer periphery, the wear resistance of the peripheral cutting edge is improved, so it can handle a wide range of work materials such as steel and cast iron without causing breakage or damage to the peripheral cutting edge. Can be cut.

As a result, tool life is significantly extended, and
By increasing the cutting speed and feed rate, it is now possible to perform heavy cutting, which not only expands the machining range and greatly improves productivity, but also significantly improves machining accuracy. There is a great effect that it can be done.

In addition, the present invention does not extend the terminal ends of the bottom cutting blades to the outer periphery of the ball end mill body, but allows the distance between the terminal ends of the bottom cutting blades to be approximately 70% to 90% of the diameter of the ball end mill body. Because of this structure, compared to the case where the end of the bottom cutting blade extends to the outer periphery of the ball end mill body, the difference in circumferential speed between the starting end and the ending end of the bottom cutting blade is reduced as much as possible, and the bottom cutting Not only is the load applied to the entire blade reduced, but the difference in the load applied to each part of the bottom cutting edge is reduced, and the stress acting on the bottom cutting blade is reduced.

Furthermore, the present invention does not extend the starting end of the peripheral cutting edge to the vicinity of the center of the ball end mill body.
Since the distance between the starting ends of the peripheral cutting blades is approximately 60% to 80% of the diameter of the ball end mill body, the distance between the starting ends of the peripheral cutting blades is approximately 60% to 80% of the diameter of the ball end mill body. Therefore, the difference in circumferential speed between the starting end and the terminal end of the circumferential cutting edge is reduced as much as possible, and not only the load applied to the entire circumferential cutting edge is reduced, but also the difference in the load applied to each part of the circumferential cutting edge is small. This reduces the stress acting on the peripheral cutting edge.

For this reason, the tool life is extended and the chances of tool replacement are significantly reduced, which has the advantage that productivity can be improved and production costs and tool costs can be reduced.

In addition, by adopting a configuration in which the distance between the terminal ends of the bottom cutting blade and the distance between the starting ends of the peripheral cutting blade are set to a predetermined length, it can be used over a wide range of rotation speeds, and can be used at any cutting speed. Also, there are advantages in that stress concentration can be avoided, the strength of the cutting edge can be improved, and productivity and machining accuracy can be improved.

On the other hand, when the bottom cutting edge and the circumferential cutting edge are aligned on a straight line and joined together as in the conventional example, stress concentration occurs at the joint, and the bottom cutting edge and the circumferential cutting edge may peel or break. , not only each blade is destroyed;
There is a problem in that the work material is also damaged. However, in the present invention, the terminal end of the bottom cutting blade and the starting end of the peripheral cutting blade are approximately 5 times the diameter of the ball end mill main body on the rotation trajectory.
%~20% overlap in the radial direction, so the material of the cutting edge does not change suddenly and coexists over a specified length, dispersing stress and avoiding stress concentration. It is possible to solve the above problem. Therefore, it can contribute to extending tool life, and by increasing the cutting speed and feed rate, it is possible to perform heavy cutting and expand the machining range, as well as being able to handle a wide range of rotation speeds. , it has the advantage of being able to perform heavy cutting, expanding its versatility with respect to workpiece materials, and contributing to improved productivity.

[Brief explanation of the drawing]

FIG. 1 is a side view of a ball end mill provided with a bottom cutting edge and a peripheral cutting edge based on the present invention. FIG. 2 is a bottom view of FIG. 1. 1...Ball end mill, 2...Shank, 3
... Ball end mill body, 4 ... Tip part, 5 ...
...Tip pocket for bottom cutting blade, 6...Tip pocket for circumferential cutting blade, 7...Tip for bottom cutting blade, 8...Tip for circumferential cutting blade, 9...Bottom cutting blade, 9a...Starting end, 9b
...Ending end, 10...Peripheral cutting edge, 10a...Starting end, 1
0b...Terminal end, D...Diameter of the ball end mill body, R...Curvature radius of the bottom cutting blade, Le...Distance between the terminal ends of the bottom cutting blade, Lr...Distance between the starting ends of the peripheral cutting blade,
Lo: Overlap in the radial direction between the end of the bottom cutting edge and the beginning of the peripheral cutting edge on the rotation trajectory.

Claims (1)

[Claims for Utility Model Registration] (1) In a ball end mill in which a bottom cutting blade is provided at the tip of the ball end mill body, and a peripheral cutting blade is provided from the outer periphery of the main body to the tip, The cutting edge is made of M30, which is a tough carbide among the cemented carbides for general cutting tools, and the peripheral cutting edge is made of M20, which is a strong wear-resistant cemented carbide among the cemented carbides for general cutting tools. , furthermore, the distance between the terminal ends of the bottom cutting blade is about 70% to 90% of the diameter of the ball end mill body, and the distance between the starting ends of the peripheral cutting blade is about about the diameter of the ball end mill body.
60% to 80%, and moreover, the terminal end of the bottom cutting blade and the starting end of the peripheral cutting blade overlap in the radial direction by about 5% to 20% of the diameter of the ball end mill body on the rotation locus. A ball end mill characterized by: (2) Utility model registration claim 1, characterized in that the bottom cutting edge and the circumferential cutting edge are provided in pairs facing each other in the intersecting direction when viewed from the bottom.
Ball end mill described in section. (3) Utility model registration claim 1 characterized in that two pairs of bottom cutting blades and peripheral cutting blades are provided facing each other in the intersecting direction when viewed from the bottom.
Ball end mill described in section. (4) Utility model registration claim 1, characterized in that the bottom cutting edge and the peripheral cutting edge are formed point-symmetrically with respect to the axial center of the ball end mill body.
The ball end mill according to any one of Items 1 to 3. (5) Any one of claims 1 to 3 for registering a utility model, characterized in that the bottom cutting edge and the peripheral cutting edge are formed eccentrically with respect to the axial center of the ball end mill body. Ball end mill described in.