JPH046487B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an end mill suitable for highly efficient cutting of low melting point and low hardness materials such as aluminum alloys.

[Conventional technology]

2. Description of the Related Art Conventionally, end mills for cutting materials having a low melting point and low hardness, such as aluminum alloys, have a cross section perpendicular to an axis as shown in FIG. This means that the diameter W of the circle inscribed in the thick core part has a relationship of 0.4D≦W≦0.5D with respect to the diameter D of the blade, and that for general steel materials is 0.5D≦W≦0.65. In contrast to the relationship D, it is of the timid and thick type. When cutting the above-mentioned materials, the shear angle is small because of their low hardness, and the thickness of the chips is therefore thick, making them difficult to curl like steel materials. In addition, due to its low melting point,
During the cutting process, chips tend to adhere to the tool due to cutting heat. Therefore, in order to prevent chips from clogging the chip evacuation groove 4 due to the above-mentioned reasons, the main focus is on making the evacuation groove 4 as large as possible. The diameter W of the circle inscribed in the thick portion is set smaller than that for cutting steel. This is done after considering the balance with the rigidity of the blade. Furthermore, during work, it is common to use cutting oil for cooling and lubrication, and this also attempts to prevent chips from adhering to the tool.

[Problem to be solved by the invention]

In recent years, for the purpose of improving productivity, there has been a need for even more efficient cutting, that is, cutting at high speed and high feed. However, when performing high-efficiency cutting, conventional aluminum cutting end mills are designed with chip evacuation in mind as described above, but the chip evacuation grooves are often clogged with chips. In the worst case, the end mill itself may be damaged. This is due to high speed,
In the curvature R ₂ part of the cross-sectional shape shown in Fig. 2, because the shape of aluminum chips during high-feed cutting is thick as described above and does not curl small,
This is due to the effect of blocking the outflow direction of chips, causing the chips flowing out at high speed to stagnate in this R ₂ section. Therefore, it may be possible to set the heart thickness even smaller and make the discharge groove larger.
With such a shape, the rigidity decreases significantly, and even when cutting aluminum, chatter vibrations and deflections occur, making it impossible to withstand high feed rates. The present invention was created to solve the above problems. Therefore, it is an object of the present invention to provide an end mill that prevents chip clogging and enables good cutting when performing highly efficient cutting of materials with a low melting point and low hardness such as aluminum alloys. .

[Means to solve the problem]

In order to achieve the above object, the end mill according to the present invention is configured as follows. That is, the end mill according to the present invention has a side blade having a helix angle on its outer circumferential surface and extending from the tip toward the rear end, and a chip discharge groove formed along the side blade. The chip discharge groove has a concave arcuate cross section perpendicular to the axis. The radius of curvature is constant or increasing from the rake face constituting the concave surface toward the heel, but the diameter W of the circle inscribed in the thick core portion and the diameter D of the blade portion are 0.15D≦W≦0.3D. They have the following relationship. This restricts the radius of curvature of the concave surface from increasing indefinitely, ensuring the necessary rigidity for the end mill. In the most preferred embodiment, the arcuate concave surface is a single arcuate concave surface that passes through the edge point of the cutting edge having a constant rake angle θ of the side blade and encloses a circle inscribed in the thick core portion. formed by.
The radius of curvature R of the circular arc is expressed as R=( ² −W ² )/{4(W+Dsinθ)}. It should be noted that the fact that this radius of curvature R is determined by the above formula is proven by the following analysis using FIG. FIG. 3 is a diagram showing a cross-sectional shape perpendicular to the axis of the end mill according to the present invention, in which the circumferential surface of the chip discharge groove formed by the arcuate concave surface with the radius of curvature R has a constant rake angle θ. It is given by a circle passing through the cutting edge point P of a given side blade and enclosing a circle inscribed in the thick core portion. Also, in Fig. 3, the rotation axis O of the end mill is
An X-Y coordinate system is given with the origin as , and the coordinates of the center of curvature A of the concave surface are (x, y). Now, if Q is the intersection of a straight line parallel to the X-axis passing through point A and the Y-axis, then ∠PAQ=θ. ∴=Rsinθ Here, |y|=−, so |y|=D/2−Rsinθ Similarly, |x|= Therefore, |x|=Rocsθ The distance between the center of curvature A and the end mill rotation axis O is =R+W /2 From the Pythagorean theorem for right triangle AOQ, |x| ² = ² −|y| ² ∴(Rcosθ) ² = (R+W/2) ² −(D/2−Rsinθ) ² = (R ² +WR+W ² /4) −(D ² /4−DRsinθ+R ² sin ² θ) =R ² (1−sin ² θ)+R(W+Dsinθ) +(W ² −D ² )/4=R ² cos ² θ +R(W+Dsinθ) +(W ² − D ² )/4 ∴R(W+Dsinθ)=(D ² −W ² )/4 ∴R=(D ² −W ² )/{4(W+Dsinθ)}

[Effect]

Generally, when performing high-efficiency cutting, the thickness of chips becomes thicker than in normal cutting, and at the same time, it becomes difficult to curl. This is not an exception when using the end mill according to the present invention, but the discharge of chips in the end mill of the present invention is performed as follows. That is, the chips cut out from the side blade and flowing out along the rake face flow within the discharge groove along the arcuate concave surface. However, in the end mill according to the present invention, the diameter of the circle inscribed in the thick core portion is set to be sufficiently smaller than the diameter of the blade portion, so that the radius of curvature of the arcuate concave surface forming the chip evacuation groove is large. Moreover, because it is given as an extremely gentle curved surface, and the radius of curvature is constant or gradually increases from the side blade edge side to the heel side, it has a thick shape with little curl, that is, a relatively straight shape. Even if chips flow out quickly and at high speed, they can be discharged extremely smoothly without interfering with their linear flow. In other words, the chips are discharged while maintaining their initial curled state, and unlike the conventional method, the discharge direction is not restricted by the discharge groove during the discharge. Here, a case where the radius of curvature gradually increases will be explained. In the present invention, it is most preferable that this radius of curvature is constant, so as not to impede the flow of chips and to minimize the reduction in rigidity of the end mill itself. However, even if it is not possible to form a curved surface with a sufficiently constant radius of curvature due to manufacturing accuracy, manufacturing conditions, or some other problem, the radius of curvature will change from the side blade edge side to the heel side. As long as it increases without being reduced, there is no problem of impeding chip evacuation, but it merely reduces the rigidity of the end mill itself to some extent. Therefore, as long as sufficient rigidity can be secured in actual use, some increase in the radius of curvature is acceptable as long as the radius of curvature from the side blade edge side to the heel side does not decrease. Become. It should be noted that it is not sufficient to make the radius of curvature of the concave surface large; if it is made large, the thick core portion becomes correspondingly thinner, which is disadvantageous in terms of rigidity.
However, in the present invention, the relationship between the diameter W of the circle inscribed in the thick core portion and the blade diameter D is regulated to 0.15D≦W≦0.3D, and the chip evacuation performance is improved as described above. In other words, since the cutting resistance is reduced, if the thickness of the core thickness is maintained to this extent, the rigidity will not be disadvantageous.
Furthermore, since the concave surface of the chip discharge groove has a substantially constant curvature, a thick portion is formed in the heel portion, which has the advantage of increasing rigidity.

【effect】

According to the above configuration, unlike the conventional method, the discharge groove itself does not obstruct the discharge of chips when performing high-efficiency cutting, and therefore no chip clogging occurs. In addition, although the cross-sectional rigidity of the blade part has decreased, this point can be compensated for by improving the chip evacuation performance as described above and limiting the application to low-hardness materials, so there is no problem in practical use. Not only that, but it can also be made more durable than before. Furthermore, since the evacuation of chips is greatly improved, it is also possible to carry out the cutting process in a dry manner.

【Example】

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a schematic diagram showing an axis-perpendicular cross-sectional shape of an end mill according to an embodiment of the present invention. As shown in the figure, in the end mill of this embodiment, the chip discharge groove 4 is formed by an arcuate concave surface 5 having a single radius of curvature R. The concave surface 5 is twisted and continuous in the axial direction to form a thick core portion, and the concave surface 5 has a diameter W of a circle inscribed in the thick core portion and a blade diameter D such that 0.15D≦W. The radius of curvature R is regulated to satisfy the relationship ≦0.3D. As is clear from a comparison with the conventional end mill shown in FIG. 2, the diameter W of the circle inscribed in the thick core portion is about half that of the conventional end mill.
Conventional end mills have a thick core inscribed circle diameter that is about half the diameter of the blade in order to emphasize blade rigidity, but in the present invention, the diameter of the inscribed circle of the thick core part is about half the diameter of the blade. Therefore, we focused on chip evacuation rather than blade rigidity. Therefore, it has become possible to form the concave surface 5 into a much gentler curved surface than in the past. A test was conducted on the cutting performance of an end mill configured as described above and a conventional end mill on aluminum material. The results will be explained below. First, the dimensions and cutting conditions of each essential part of each endless are listed. Dimensions of each end mill Shank diameter 10 mm (straight shank) Overall length 75 mm Blade outer diameter 10 mm Blade length 25 mm Example end mill (Figure 1) Core thickness Inscribed circle diameter W = 2.5 mm Groove concave curvature radius R = 4.321 mm Conventional Technical end mill (Fig. 2) Core thickness Inscribed circle diameter W = 4.0 mm Groove concave curvature radius R ₁ = 4.0 mm R ₂ = 1.8 mm R ₃ = 3.4 mm Cutting conditions (dry cutting) Groove width 10 mm Depth 15 mm Number of revolutions Under the conditions of 2235r.pm or more, the feed rate is 100.
Cutting tests were conducted at 160, 260, 400, and 650 mm/min. It should be noted that this test involved deep groove machining and was conducted dry. When cutting tests were conducted at feed speeds of 100 and 160 mm/min, no particular problems occurred in either case, and the cutting conditions were good. However, when the feed rate was set to 260 mm/min, the conventional end mill broke at a cutting distance of 100 mm. When we examined this end mill, we found that the chip discharge groove 4 was clogged with a large amount of chips, and the cutting resistance became too large due to this chip clogging.
This is thought to be the direct cause of the breakage. On the other hand, according to this embodiment, the feed rate is 260 mm/
There were no problems at 400 mm/min, 400 mm/min, or 650 mm/min, and the cutting conditions were good. When we continued the test to confirm the limit feed speed of this end mill by increasing the feed speed, breakage occurred at 1030 mm/min, but the ejection groove 4 of the broken end mill was completely free of chips. It is different from the conventional one in this point. From this, it is thought that the cause of the breakage of the end mill in this example was not due to clogging of chips, but that the increase in cutting resistance accompanying the increase in feed rate exceeded the rigidity of the blade. For example, by shortening the blade length and increasing the blade rigidity as much as possible, it is possible to maintain chip evacuation and achieve higher feed rates. In addition, 1 at the time of breakage
The feed per tooth is 0.23 mm/min, but if this is considered to be the upper limit of this example, it is possible to perform cutting with an even higher feed by further increasing the rotational speed. However, when the diameter of the circle inscribed in the core thickness is less than 0.15D, chatter vibration occurs due to lack of rigidity rather than a problem with chip evacuation, and conversely, when the diameter of the circle inscribed in the core thickness exceeds 0.3D In this case, the radius of curvature of the concave surface of the discharge groove becomes smaller than the curl diameter of aluminum chips when the distance from the side blade edge to the bottom blade is short and the feed rate is high, and the resistance that restrains the chips increases. Although these end mills may be usable depending on cutting conditions, the present invention considers 0.15D≦W≦0.3D to be an effective range on the premise of general-purpose use at high speeds and high feeds. As explained above, if the end mill according to this embodiment is used, the chip discharge groove will not be clogged with chips. In addition, although the rigidity of the blade itself has decreased, the ejection resistance of chips has been reduced, and by limiting the application to cutting soft materials, the decrease in rigidity has been sufficiently compensated for. Cutting can be performed at a feed rate that is about 3 to 4 times faster than the previous one. Of course, under the same cutting conditions,
Its durability is beyond comparison.
In addition, since it becomes possible to perform dry cutting on materials such as aluminum, which has rarely been done in the past, it is possible to improve the content of the work, such as reducing the number of cleaning steps. Note that the heel portion may be chamfered with a curved surface as shown by reference numeral 6 or a flat surface within a range that does not significantly reduce the rigidity. In the above embodiment, as an embodiment of the best mode of the present invention, the case where the radius of curvature of the arcuate concave surface is constant was explained, but for example, from the edge side of the side blade 1 of the concave surface 5 in FIG. It is also possible to gradually increase the radius of curvature toward the heel portion to form a concave surface 5' as shown by the imaginary line in the figure. In this case, although the rigidity of the end mill is slightly reduced, chip evacuation is good, and depending on the cutting conditions, sufficiently effective high-speed, high-feed cutting can be performed.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a cross-sectional shape perpendicular to the axis of an end mill according to an embodiment of the present invention, Fig. 2 is a schematic diagram showing a cross-sectional shape perpendicular to the axis of a conventional end mill, and Fig. 3 is a schematic diagram showing a cross-sectional shape perpendicular to the axis of an end mill according to the present invention. It is a diagram in which a coordinate system is given to . 1... Side blade, 2... Heel part, 3... Rake surface, 4... Chip discharge groove, 5, 5'... Concave surface, D
...Diameter of the blade, R...Radius of curvature of the arcuate concave surface, W
...The diameter of the circle inscribed in the thick heart.

Claims (1)

[Claims] 1. A side blade 1 extending from the tip toward the rear end with a helix angle on the outer peripheral surface of the end mill body;
In a two-blade end mill having a chip discharge groove 4 formed along the side blade 1, the chip discharge groove 4 is formed in a concave portion 5, 5' having an arc-shaped cross section perpendicular to the axis. The concave surfaces 5, 5' extend from the edge of the side blade 1 constituting the heel portion 2.
The radius of curvature remains constant or increases toward
An end mill characterized in that the size of the radius of curvature is regulated so that the relationship between the diameter of the circle inscribed in the thick core portion and the diameter of the blade portion satisfies 0.15D≦W≦0.3D. However, D indicates the diameter of the blade portion, and W indicates the diameter of the circle inscribed in the thick core portion. 2 The cross-sectional shape perpendicular to the axis of the chip discharge groove 4 is formed by a concave surface 5 of a single arc that passes through the edge point of the cutting edge having a constant rake angle of the side blade 1 and circumscribes a circle inscribed in the thick core portion. The end mill according to claim 1, wherein the end mill is formed with a radius of curvature of the circular arc as follows: R=( ^D2 - ^W2 )/{4(W+Dsinθ)}. However, R is the radius of curvature, and θ is the rake angle of the side blade.