JP3337804B2 - End mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end mill used for a machine tool such as a milling machine and a machining center.

[0002]

2. Description of the Related Art An end mill disclosed in Japanese Patent Application Laid-Open No. 5-96417 is one having an outer peripheral cutting edge having a convex step on the rake face. By providing lands with a width corresponding to 5 to 20%, cutting resistance is suppressed and sharpness is improved. Also, in JP-A-1-310807, an end mill provided with a negative land is described. The rake angle of the negative outer peripheral cutting edge in the cross section perpendicular to the tool axis is in the range of −70 ° to −20 °, and as one of the embodiments, an example in which a rake face has a convex step is described. next,
In order to cope with this, the cutting efficiency has been improved, and end mills have been designed to respond to this, such as setting the core thickness larger than before and making the rake angle of the outer cutting edge a negative angle, etc. High-speed, high-feed cutting becomes possible in cutting.
There are end mills that enable high-efficiency cutting and can also cut hard materials such as hardened steel.

[0003]

However, the end mill disclosed in Japanese Patent Application Laid-Open No. 5-96417 has insufficient tool stiffness and cutting edge stiffness similarly to a normal end mill. In some cases, chipping occurs due to vibration, chatter, and the like, causing breakage, and there is a problem in stability. In addition, the end mill disclosed in JP-A-1-310807 has a very large negative rake angle for exclusive use in cutting high-hardness materials, has a problem in sharpness, and increases cutting resistance. Further, Japanese Patent Application Laid-Open No. 1-31
The effects of the No. 0807 and the conventional high-efficiency cutting end mill are obtained by light cutting with a small depth of cut. In the case of large depth of cut such as grooving or counterboring, the former is sharp. Deterioration and increased cutting resistance, the latter having narrow chip pockets, causing clogging of chips and making cutting impossible. In addition, by providing the core thickness in a tapered shape with the shape of a normal end mill,
Although there has been a contrivance to obtain tool rigidity, it is insufficient for high-efficiency cutting, and there is a problem in chip dischargeability.

[0004]

[Object of the present invention] In order to solve the above-mentioned problems, the present invention examines various blade shapes to enhance the rigidity of the end mill, improve the chip discharge property, reduce the cutting resistance, and An object of the present invention is to provide a high-efficiency and high-performance end mill in cutting.

[0005]

In order to achieve the above object, the present invention provides an end mill having an outer peripheral cutting edge formed on the outer periphery of an end mill body, wherein the rake angle of the outer peripheral cutting edge in a right angle cross section of the end mill is provided. Exceeds -20 ° and is 0
゜ or less, having a convex step between a part of the rake face or the entire length of the blade, the core thickness on the shank side of the end mill is larger than the core thickness at the tip portion, and the core thickness in the axial direction is An end mill characterized by having at least one part where the rate of change has changed, excluding the end gask and cut-up parts.

In addition, the core thickness at the end of the end mill is less than 70% of the tool blade diameter, and the core thickness near the shank side blade base is 7%.
It may be set in the range of 0 to 90%. Further, by setting the torsion angle of the cutting edge in the range of 20 ° to 65 °, the sharpness can be improved and the chipping resistance can be significantly improved. Still further, as the coating, Al, Si which is excellent in crater wear, 4a, 5a, 6a of the periodic table.
One or more hard substances selected from the group consisting of carbides, nitrides, oxides, borides, and boron carbides, hard boron nitrides, hard carbons, and solid solutions or mixtures thereof of group III transition metals Is further coated with a single layer or a multilayer of two or more layers with a thickness of 0.2 to 20 [mu] m, whereby a further effect can be obtained.

[0007]

The present invention improves the rigidity of the tool and makes it possible to discharge various chips, including groove cutting and spot facing, with higher efficiency and stability by making the structure excellent in chip discharge. Things. Since the rake angle of the outer peripheral cutting edge in the cross section perpendicular to the tool axis is more than -20 ° and 0 ° or less, and a part of the rake face of the outer peripheral cutting edge or a convex step is formed between all the blade lengths, the cutting edge is reduced. While maintaining the edge strength of the blade, the sharpness is improved, and various cutting processes can be performed with high efficiency and high performance. The rake angle of the outer peripheral cutting edge in the cross section perpendicular to the tool axis is inferior in sharpness below -20 ° as described in the above problem to be solved by the present invention, and the blade edge strength is deteriorated when it exceeds 0 °.
It was set above 20 ° and below 0 °.

[0008] End mills having a negative rake angle are generally less likely to curl chips than those having a regular angle, and the amount of contact between the rake face and the chips is large and cutting resistance is increased. By providing a step between a part of the surface or the entire blade length, the contact amount is reduced, and the chip pocket is increased, so that the chip dischargeability and sharpness are improved. Here, the angle difference in the section perpendicular to the tool axis of the step portion directly involved in cutting is desirably 10 ′ to 40 °, and the distance from the blade tip to the step in the section perpendicular to the tool axis is 0. It is preferably from 01 to 0.1 times.
Further, the angle difference and / or the distance may temporarily change.

[0009] Further, by having at least one portion where the rate of change of the core thickness changes in the tool axis direction,
At that portion, chip clogging is reduced and / or the function of a chip breaker is achieved, so that cutting such as groove cutting and spot facing can be performed efficiently and satisfactorily. Here, it is desirable that the portion where the core thickness changes sequentially has a smoothly rounded change amount in the tool axis direction. Also, it is within the scope of the present invention to have a portion where the core thickness decreases slightly from the end mill tip toward the cutting edge, and there is no significant difference in performance, but it decreases when the tool rigidity surface is considered. It is desirable not to have a part.

In order to obtain a further effect, the core thickness at the end portion of the end mill may be set to less than 70% with respect to the tool blade diameter, and the core thickness near the shank side cutting edge portion may be set to 70 to 90%.
When the core thickness is 70% or more of the tool blade diameter, the chip pocket is narrow in cutting such as groove cutting and counterbore processing. Therefore, the core thickness near the end of the end mill is set to 70% or less. In addition, the core thickness of the maximum core thickness near the shank-side cutting edge is 70%.
If less, vibration, chatter, etc. are likely to occur, and 90%
Exceeds 70%, sufficient space cannot be obtained in the chip pocket.

Further, the torsion angle of the outer peripheral cutting edge is set to 20 ° or more.
The reason why the angle is set to 65 ° is that when the angle exceeds 65 °, the number of simultaneous interference blades increases, and when the angle is less than 20 °, the length of the simultaneous interference blades increases, and in all cases, the cutting resistance increases and the sharpness tends to deteriorate. . It should be noted that the coating of the hard substance further enhanced the efficiency and the performance due to the synergistic effect with the above.

[0012] Here, not only cutting such as grooving, but also cutting with a large depth of cut, spot facing, etc., as well as light cutting such as side cutting and cutting of a hard material such as hardened steel are possible. Needless to say. In addition, since the end mill of the present invention is complicated in shape, a special end mill manufacturing method may be used.However, the shape can be accurately formed by additional machining with a normal grinder for cutting a groove. Obtained and easy to manufacture the end mill.

[0013]

1 to 4 show an embodiment of the present invention, in which a tool blade diameter of 10 mm, a four-blade, right-hand right-hand twist (helix angle) is used, using an ultra-fine-grain cemented carbide coated with TiN. : 50 °). The rake angle of the outer peripheral cutting edge in the section perpendicular to the tool axis is -15 °, the clearance angle is 10 °, the core thickness at the end mill end is 60% of the tool blade diameter, and the core thickness at the shank side blade base is the tool thickness. 80%, the groove is continuous with a smooth curve at the center of the tool blade length, and about 1/4 and 1 of the tool blade length from the end mill end.
The change rate of the heart thickness is changed at the site of / 2. The rake face of the outer peripheral cutting edge at a position 部位 of the tool blade length from the end of the end mill has a convex step, and the tool axis at a position １ ／ of the tool blade length from the end of the end mill. The distance from the blade tip to the step in the right-angle cross section is 0.6 mm, which is 0.06 times the tool blade diameter, and is gradually increased to a position that is half the tool blade length. Further, the angle difference in the section perpendicular to the tool axis of the stepped portion is set to 1 °.

Table 1 shows a comparison of the cutting performance between the product of the present invention and the conventional product shown in FIGS. The conventional product has a core thickness of 55% of the tool blade diameter, a rake angle of 0 ° (conventional product 1), a core thickness of 80% of the tool blade diameter, and a rake angle of −20 ° (conventional product 2). Using. Here, for the sake of comparison, a convex step was provided in each case, and portions other than the above were formed in the same shape. In the cutting test, the hardness of S50C was used as the work material, and the hardness was HRC23.
Feed speed 1000mm / min, axial cut 10m
This is the result of performing five groove cuttings with a length of 2 m each for a cutting length of 2 m. The cutting conditions are high-efficiency processing conditions in which the feed rate and the cutting amount are large.

[0015]

[Table 1]

Here, the chipping of the cutting edge or the length of the cutting edge at the part where the cutting edge is lost is expressed by a value expressed as a percentage with respect to the length of the cutting edge required for cutting, using the evaluation criterion as the chipping rate.
The spindle load factor of the machine was used as a value indicating the machinability. Although the chipping rate of the product of the present invention slightly increases with the cutting length, the value is less than 1% when cutting 2 m, and the maximum flank wear width of the outer peripheral cutting edge is 0.05 m.
m, and continuous cutting was possible. In addition, the spindle load ratio was stable at 30% or less, and the cutting state was good.

The defect rate of the conventional product 1 exceeds 10% on average,
Many cutting edges are severely broken, vibration, chatter and cutting noise during cutting are large, and the spindle load factor is 4 when cutting 2m.
Some of them broke beyond 0%, and could no longer be cut. With regard to the conventional product 2, the spindle load factor already exceeded 60% in the early stage of cutting, and the product was broken in the early stage of use.
FIG. 5 shows another embodiment of the present invention in which the core thickness is changed in a two-step taper shape. A cutting test was performed under the same conditions as above, and the same good results as those of the above-described present invention were obtained. Obtained.

[0018]

As described above, by applying the present invention, the rigidity of the end mill can be increased, the chip discharge property can be improved, the cutting resistance can be reduced, and high efficiency and high performance can be achieved in various cutting operations. It was like that.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the vicinity of a tip end portion of the end mill in FIG.

FIG. 3 is a cross-sectional view of the vicinity of the shank side blade base in FIG. 1 in a cross section perpendicular to the blade axis.

FIG. 4 is an enlarged view of an outer peripheral cutting edge portion of FIG. 2;

FIG. 5 is a side view showing another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 outer peripheral cutting edge 2 shank part 3 end gash part 4 cut-up part 5 blade groove 6 core thickness 7 chip pocket 8 convex step part θa torsion angle θb rake angle θc relief angle α angle difference of step part t step difference from blade tip Distance to part

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-48211 (JP, A) JP-A-5-337718 (JP, A) JP-A-6-31519 (JP, A) 23925 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B23C 5/10

Claims (4)

(57) [Claims] 1. An end mill having an outer peripheral cutting edge formed on an outer periphery of an end mill body, wherein a rake angle of the outer peripheral cutting edge in a right-angle cross section of the end mill is more than -20 ° and 0 ° or less, and one side of the rake face is provided. It has a convex level difference between part or total cutting edge length, the axial thickness of the shank of the end mill tip
Is larger than the core thickness of the
Excluding the end gask and cut-up parts
And an end mill having at least one location . 2. The end mill according to claim 1, wherein the center thickness of the tip is set to less than 70% of the end mill blade diameter, and the center thickness of the shank side is set to a range of 70 to 90%. End mill. 3. The end mill according to claim 1, wherein the torsion angle of the outer peripheral cutting edge is set in a range of 20 ° to 65 °. 4. The end mill according to claim 1, wherein the Al, Si, carbides, nitrides, oxides, borides and boron carbides of transition metals of Groups 4a, 5a and 6a of the Periodic Table, hard boron nitride, One or more hard materials selected from the group consisting of hard carbons and solid solutions or mixtures thereof are coated with a single or two or more layers in a thickness of 0.2 to 20 μm. And end mill.