JPS6362323B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a milling tool having a plurality of twisted cutting edges formed on its outer periphery. [Prior art] Conventional milling tools of this type include those shown in Fig. 8A,
There is an end mill shown in B. This end mill is
A plurality of cutting edges 2 are formed on the outer periphery of a blade portion 1a at the tip of a rod-shaped end mill body 1, and the cutting edges 2 are twisted to prevent the end mill body 1 from vibrating greatly. It is formed with That is, if the cutting edge 2 is formed straight along the longitudinal direction of the end mill body 1,
The entire cutting portion of the cutting blade 2 in the axial direction bites into the workpiece at the same time and separates from the workpiece at the same time. When the cutting blade 2 bites into the workpiece, the cutting load acts impulsively on the end mill body 1, while
When the cutting blade 2 separates from the workpiece, the cutting load acting on the end mill body 1 rapidly decreases. Due to this sudden change in cutting load, the end mill body 1
is made to vibrate. In this regard, in the end mill described above, since the cutting blade 2 is formed with a twist, the cutting blade 2 gradually bites into the workpiece and gradually separates from the workpiece. Therefore, the cutting load does not change suddenly, and the end mill main body 1 can be prevented from vibrating. [Problems to be solved by the invention] However, in the above end mill,
Although relatively large vibrations due to rapid changes in cutting load could be prevented, relatively small vibrations did occur. This results in poor surface finish and
In particular, it could not be said to be fully satisfactory in cases where high surface roughness is required, or in cases where heavy cutting (deep cutting) or high feed rate cutting is required. [Searching for the cause of the problem] Therefore, the inventor of this application investigated the cause of relatively small vibrations, and came to the conclusion that the cause lies in the following points. That is, in the conventional end mill described above,
Since the helix angles of each cutting edge 2 are equal to each other and each cutting edge 2 is formed at equal intervals in the circumferential direction, as shown in FIG. The distance between adjacent cutting edges 2 in the axial direction and the circumferential direction is constant in any part. When a cutting load acts on each cutting blade 2 having a constant interval, the vibration of the end mill body 1 caused by the cutting load also always has a substantially constant frequency, and these vibrations resonate with each other. As a result, it was estimated that relatively small vibrations would be generated in the end mill body 1, but to the extent that they would have an adverse effect on the surface roughness. [Object of the Invention] This invention was made based on the above estimation, and can prevent relatively small vibrations from occurring in the tool body, thereby improving the finished surface and improving heavy cutting. An object of the present invention is to provide a milling tool that enables deep cutting and high-feed cutting, and prevents chip clogging. [Means and effects for solving the problem] In order to achieve the above object, the present invention makes the helix angle of at least one of the plurality of cutting edges different from the helix angle of the other cutting edges. In addition to setting the angle, the circumference between two cutting edges that are adjacent in the rotational direction and the helix angle of the cutting edge located at the front in the rotational direction is larger than the helix angle of the cutting edge located at the rear in the rotational direction. The distance in the direction is less than the distance between two cutting edges that are adjacent in the rotational direction, and the helix angle of the cutting edge located at the front in the rotational direction is smaller than the helix angle of the cutting edge located at the rear in the rotational direction. is also set larger at the end of the tool body where the edge located forward in the rotational direction of the two edges of the cutting blade exists. When the helix angle of at least one cutting edge is set to a different angle from the helix angle of the other cutting edges, the circumferential and axial spacing between the cutting edge set to the different helix angle and the adjacent cutting edge changes continuously from the tip of the cutting edge toward the rear end. As a result, the frequency of vibrations generated in the end mill body changes as the end mill rotates, and these vibrations cancel each other out. Therefore,
It is possible to prevent vibrations from occurring in the end mill body that would deteriorate the finished surface. By the way, when the helix angles of the cutting blades are set to be different from each other, the circumferential distance between the two cutting blades gradually decreases or increases from one end of the cutting blade to the other as described above. do. Correspondingly, it becomes necessary to gradually decrease or increase the circumferential width of the tip pocket to be formed between the two cutting edges. In this case, there is no problem with a tip pocket whose width gradually increases, but with a tip pocket whose width gradually decreases, there is a risk that chips will become clogged at the end on the side where the width decreases. Therefore, in this invention, between two cutting edges that are adjacent in the rotational direction, the helix angle of the cutting edge located at the front in the rotational direction is larger than the helix angle of the cutting edge located at the rear in the rotational direction. The distance in the circumferential direction is defined as the distance between two cutting edges that are adjacent in the rotational direction, where the helix angle of the cutting edge located at the front in the rotational direction is smaller than the helix angle of the cutting edge located at the rear in the rotational direction. It is set larger at the end of the tool body on the side where the edge located forward in the rotational direction of the two edges of the cutting blade exists. In other words, in the case of a tip pocket whose width gradually narrows from one end of the tool body to the other, the width at one end is made wider in advance than the width at one end of the other tip pocket. This prevents the chip pocket, which gradually becomes narrower, from becoming too narrow. In addition, for milling tools such as flat milling cutters where both ends and the center are used with almost the same frequency, the width of each tip pocket should be set to be the same width at the center of the blade. death,
In milling tools such as end mills, where the cutting edge can be used within a certain range from the tip, the width of each chip pocket is the same from the tip of the tool body to 1/3 of the blade length or the center. It is desirable to set it so that [Example] Hereinafter, an example of the present invention will be described with reference to FIGS.
This will be explained with reference to FIG. In the figure, reference numeral 11 is an end mill main body, and the tip of this end mill main body 11 is a blade portion 12. Four twisted cutting edges 13a, 13b, 13c, and 13d are formed on the outer periphery of this blade portion 12. Cutting blades 13a, 13b, 13c, 1
There are chip pockets 14a, 1 in sequence between each of the 3d
4b, 14c, and 14d are formed. Also,
Each cutting blade 13 is provided on the tip surface of the end mill body 11.
Bottom blades 15a, 15b, 15c, 15 extending from a, 13b, 13c, 13d toward the rotation center O side
d are formed respectively. Each bottom blade 15a-1
5d is formed in a concavely curved shape when viewed from the axial end, thereby improving its cutting performance. The above four cutting edges 13a, 13b, 13c, 13
The helix angle of the two cutting blades 13a and 13c located between the center of rotation O in d is θ ₁ , and the helix angle of the other two cutting blades 13b and 13d is θ ₂ . These θ ₁ and θ ₂ are set to satisfy θ ₁ <θ ₂ . In addition, four cutting edges 13a, 13b, 1
3c and 13d, as shown in FIG. 1A and FIG. 2, at the tip of the blade portion 12, the circumferential spacing is l ₁ between the cutting blades 13a and 13b and l 1 between the cutting blades 13c and 13d. ₁ and wide at l ₂ between the cutting blades 13b and 13c and l ₂ between the cutting blades 13d and 13a (l ₁ <l ₂ ). Moreover, considering that the length of the blade actually used is about 2/3 of the length of the blade part 12, at a position facing backward from the tip of the blade part 12 by about 1/3 of its total length, The spacing between each cutting edge is set to be the same. However, in the end mill with the above configuration,
The helix angle θ ₁ of the two cutting edges 13a and 13c is reduced, and the helix angle θ ₂ of the other two cutting edges 13b and 13d is reduced.
As shown in FIG.
The circumferential and axial intervals between the cutting edges 13b and 13c gradually widen from the tip to the rear end along each cutting edge, and between the cutting edges 13b and 13c and between the cutting edges 13d and 13a. The circumferential and axial spacing between them gradually narrows. Therefore, the frequency of minute vibrations generated by each cutting blade cutting the work changes as the end mill rotates. As a result, the vibrations caused by the cutting of the cutting blade cancel each other out, and it is possible to prevent vibrations from occurring in the end mill body 11 that would deteriorate the surface roughness of the finished surface. By the way, as mentioned above, the reason why the helix angles of the cutting blades 13a, 13c and the cutting blades 13b, 13d are made different from each other in this invention is that the interval between each cutting blade is changed thereby. This is to prevent the end mill main body 11 from vibrating, and the greater the rate of change in the interval between the cutting blades, the greater the vibration prevention effect. In order to increase the rate of change, the difference between the twist angles θ ₁ and θ ₂ may be increased. But on the other hand, also the torsion angle θ ₁
When and θ ₂ are made to have different sizes, the widths of the four tip pockets 14a, 14b, 14c, and 14d vary as the distance between the cutting edges changes. Specifically, chip pocket 14
The widths of the tip pockets 14b, 14c gradually become wider from the tip side to the rear end side.
The width of 14d becomes gradually narrower. In this case, there is no problem with the chip pockets 14a and 14c because their widths gradually increase, but the chip pocket 14
For b and 14d, if the width at the rear end side becomes too narrow, it will be difficult to discharge chips. In this respect, in the above end mill, between the cutting blades 13b and 13c where the width is narrower on the rear end side, and between the cutting blades 13d and 13d,
Since the spacing l ₂ at the tips between the cutting edges 13a is made wider than the spacing l ₁ between the other cutting edges, the widths at the tips of the tip pockets 14b and 14d are correspondingly made wider than the widths of the other tip pockets 14a and 14c. can also be made wider. Therefore, it is possible to prevent chip clogging from occurring. Regarding the difference between θ ₁ and θ ₂ , in a 4-flute end mill, the diameter D is about 20 mm, and the blade part 1
If the length of 2 is within 3D, it is desirable that |θ ₁ −θ ₂ |=1° to 10°. Next, another embodiment of the invention will be described. In the embodiment shown below, only the points different from the above embodiment will be explained, and the same parts as in the above embodiment will be given the same reference numerals and the explanation thereof will be omitted. The end mill shown in Fig. 3 has an end mill main body 1
A through hole 16 is formed in the center of the body 1, passing through from the front end surface to the rear end surface. Note that the through hole 16
Due to the relationship between the two bottom blades 13a and 1
3b, 13c, and 13d also do not reach the center O of the end mill body 11, and all have the same length. The end mill shown in FIG. 4 has bottom blades 13a, 13
b, 13c, and 13d are each formed into a straight line. Note that the bottom blade may have a shape that bulges in the direction of rotation. What is shown in FIG. 5 is a ball end mill in which the tip of the blade portion 12 is formed into a hemispherical shape. Furthermore, the one shown in FIG. 6 is a flat milling cutter, in which the cutting edge 17 has a weak twist.
A and strongly twisted cutting edges 17b are formed alternately. The above embodiment is a solid type made entirely of high-speed steel or cemented carbide.
The tool may be of a brazing type in which a cutting tip having a cutting edge is brazed to the tool body. Also,
In the end mill of the above embodiment, four cutting blades are formed, but the number of cutting blades is not limited to four as long as it is plural. In addition, the helix angles of two of the four cutting edges are the same, and the helix angles are alternately large and small.
The helix angles of all the cutting edges may be different from each other, or the cutting edges having different helix angles may be sequentially formed in the circumferential direction from the smallest helix angle. In any case, in the present invention, the helix angle of at least one of the plurality of cutting edges may be set to be different from the helix angle of the other cutting edges. Further, in the above embodiment, the twisting direction is set so that the axial rake angle of the cutting blade is a positive rake angle, but the twisting direction may be reversed. Furthermore, this invention also provides an end mill,
In addition to flat milling cutters, it can also be applied to milling tools such as side milling cutters. [Example] Next, an example of an experiment conducted to confirm vibration prevention, which is one of the effects of the present invention, will be introduced. Note that the cutting state of the experimental example is as shown in FIG. Experimental example End mill used Diameter x total length x blade length x number of teeth = 20 x 120 x 60 x 4 Helix angle, conventional product 40° (4 blades common) Invented product 38° (2 blades) 41° (2 blades) Cutting conditions Cutting Speed 40m/min Feed rate 50, 70, 90, 100 and 120mm/
mm Cutting method Down cut (wet) Axial depth of cut L 40mm Radial depth of cut D 10mm Work material SCM440 Hardness HB250 The experimental results are shown in the table below.

[Table] As is clear from the table above, vibration occurs with the conventional product under all cutting conditions, especially when the feed rate is 100
When the vibration exceeded mm/min, the vibration became too large and the experiment had to be stopped.However, with the invented product, cutting can be carried out smoothly without vibration under any cutting conditions. Ta. The invented product also requires less power than the conventional product, but this is because the conventional product vibrates and the radial depth of cut changes in size, and when the depth of cut increases, the required power increases. On the other hand, with the invented product, there is no such change in the depth of cut, and the required power is thought to be reduced accordingly. [Effects of the Invention] As explained above, according to the milling tool of the present invention, the helix angle of at least one of the plurality of cutting edges is set to a different angle from the helix angle of the other cutting edges. ing. At the same time, the circumferential distance between two cutting edges that are adjacent in the rotational direction, and the helix angle of the cutting edge located at the front in the rotational direction is larger than the helix angle of the cutting blade located at the rear in the rotational direction. , with two cutting edges adjacent in the rotation direction,
The helix angle of the cutting blade located at the front in the rotational direction is smaller than the helix angle of the cutting blade located at the rear in the rotational direction.The cutting edge is located at the front of the two edges of the cutting blade in the rotational direction than the distance between the two cutting blades. Since the gap is set larger at the end of the tool body where the edge exists, the circumferential and axial distances between cutting edges with different helix angles and adjacent cutting edges are larger from one end of the cutting edge. The vibration frequency changes continuously toward the other end, and as a result, the frequency of vibrations generated in the tool body changes as the tool rotates, and these vibrations cancel each other out. Therefore, it is possible to prevent vibrations that would deteriorate the finished surface from occurring in the tool body, and a remarkable effect can be obtained particularly in heavy cutting (deep cutting) from low feed to high feed.
In addition, the required power can be reduced, and the occurrence of chip clogging can be prevented. In addition, since the circumferential spacing of the cutting blades is set equally from the end of the tool body to 1/3 of the blade length to the center, chips can be efficiently discharged without causing chip clogging at the rear end of the tool body. It has the advantage of being able to

[Brief explanation of drawings]

FIGS. 1A and 1B show an embodiment of the present invention;
The figure is a side view, the B figure is a view taken in the direction of the X arrow in figure A, the second figure is a developed view of the blade of the end mill shown in figure 1, and the third figure is a side view of the end mill.
Figures to Figures 6 each show other embodiments of the present invention, where Figure A is a side view thereof, Figure B is a view in the direction of the X arrow of Figure A,
Fig. 7 is a diagram showing cutting conditions in an experiment conducted to confirm the effects of the present invention, Fig. 8 shows an example of a conventional end mill, Fig. A is its side view, and Fig. B is A.
9 is a developed view of the blade portion of the end mill shown in FIG. 8. 11... End mill body, 13a, 13b, 1
3c, 13d...cutting blade.

Claims (1)

[Claims] 1. In a milling tool in which a plurality of twisted cutting blades are formed on the outer periphery of a tool body, the helix angle of at least one of the plurality of cutting blades is set at a different angle from the helix angle of the other cutting blades. , and two cutting edges adjacent in the rotation direction,
The circumferential spacing between two cutting blades in which the helix angle of the cutting blade located at the front in the rotational direction is larger than the helix angle of the cutting blade located at the rear in the rotational direction is determined by rotating two cutting blades that are adjacent in the rotational direction. The helix angle of the cutting blade located at the front in the direction of rotation is smaller than the helix angle of the cutting blade located at the rear in the direction of rotation.The cutting edge is located at the front of the two edges of the cutting blade in the direction of rotation than the distance between the two cutting blades. The cutting edge is set large at the end of the tool body on the side where the edge exists, and the spacing in the circumferential direction of the cutting blade is equal in the range from 1/3 of the blade length to the center of the tool body from the end. A milling tool.