JPH0283109A - End mill - Google Patents

Abstract

PURPOSE:To satisfactorily discharge chips through a discharge groove itself in performing high-efficiency cutting by specifying the relationship between the diameter of a circle inscribed on a core thick section and the diameter of an edge section. CONSTITUTION:A cutting chip discharge groove 4 is formed with recessed faces 5 and 5' with a circular arc shaped cross section perpendicular to an axis, and the radius of curvature R of the recessed faces 5 and 5' is made constant or increased from the edge of the side edge 1 constituting them toward the heel section 2. The size of the radius of curvature R is restricted so that the diameter W of a circle inscribed on a core thick section is made larger than 0.15 times the diameter D of the edge section and smaller than 0.3 times.

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 is because the diameter W of the circle inscribed in the thick core part has the relationship 04D≦W≦0.5D with respect to the diameter of the blade, and those for general steel materials are 0.5D≦W≦ Although it has a relationship of 0.65D, it is of a small thickness type. When cutting the above-mentioned materials, their low hardness results in a small shearing angle, resulting in thick chips that are difficult to curl like steel materials. Furthermore, since the melting point is low, chips tend to be welded to the tool during cutting due to cutting heat. Therefore, in order to prevent chips from clogging the chip discharge groove 4 due to the above-mentioned reasons, the main focus is on making the chip discharge groove 4 as large as possible. The diameter W of the contacting circle is set smaller than that for steel cutting. 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, even though conventional aluminum cutting end mills are designed with chip evacuation in mind as described above, the chip evacuation grooves are often clogged with chips. In many cases, the end mill itself may be damaged in the worst case. This is due to high speed,
In high-feed cutting, the shape of the cutting layer of aluminum is thick as described above and does not curl small. Therefore, at the curvature R6 part of the cross-sectional shape shown in Fig. 2, there is an effect that blocks the outflow direction of chips, resulting in a high-speed cutting. This R2
This is due to stagnation in the department. Therefore, it may be possible to make the core thickness smaller and make the discharge groove larger, but such a shape would significantly reduce the rigidity, resulting in chatter vibration and deflection even when cutting aluminum, making it difficult to use at high feed rates. It becomes unbearable. 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 on 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 extending from the tip toward the rear end with a helix angle on its outer peripheral surface, and a chip discharge groove formed along the side blade. , the chip discharge d4 is formed into a concave surface having an arc-shaped cross section perpendicular to the axis. The radius of curvature seems to be constant and increases from the scoop forming the concave surface to the heel, but the diameter W of the circle inscribed in the thick core part and the diameter of the blade part are 0.15D≦W≦0. ．．
The relationship is 3D. As a result, the concave surface becomes
The radius of curvature is regulated so that it does not increase indefinitely, and the necessary rigidity as an end mill is ensured. Further, in the most preferred embodiment, the arc-shaped concave surface is a single arc concave surface that passes through the cutting edge point of the side blade having a constant rake angle θ and circumscribes a circle inscribed in the thick core portion. formed by. The radius of curvature R of the arc is expressed as R=(D"+W")/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. In other words, the chips that are cut from the side blade and flow out along the rake face are
It flows within the discharge groove along its 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 and extremely large. Because it is a gently 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, less curled shape, that is, it is relatively straight and Even chips flowing out at high speed 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 decrease in rigidity of the end mill itself. However, even if a curved surface with a sufficiently constant radius of curvature cannot be formed 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 ensured in actual use, some increase in the radius of curvature is allowed as long as the radius of curvature does not decrease from the side blade edge side to the heel side. Incidentally, it is not necessarily the case that the radius of curvature of the concave surface is increased; if it is increased, 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 is regulated to 015D≦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 evacuation 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 has decreased, this point can be sufficiently compensated for by the improvement in chip evacuation as described above and the limitation of application to low-hardness materials, and there is no problem in practical terms. 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 diameter of the blade portion of 0.15D. The radius of curvature R is regulated so that the relationship is ≦W≦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 four surfaces 5 into curved surfaces that are much gentler than those of the prior art. 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 main part of each end mill will be listed. Each end mill dimension Shank diameter 10im (straight shank) Total length
75! III Blade outer diameter 10m1! Blade length 2571 Shoulder example end mill (Fig. 1) Heart thickness inscribed circle diameter W-2, Button shoulder groove concave radius of curvature R = 4.321 mπ Conventional technology end mill (Fig. 2) Heart thickness inscribed circle diameter W = 4.0m Shoulder groove concave radius of curvature Rl = 4.0xmRt = 1.8m
Shoulder Rs = 3, 4 shoulders Shoulder cutting conditions (dry cutting) Groove width 1h + shoulder depth 15iz Rotation speed 2235r, p, m Under the above conditions, feed rate 100, 160,
Cutting tests were conducted at 260 xu/min, 400 xu/min, and 650 xu/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 zm/min, no particular problems occurred in either case.
The cutting condition was good. However, if the feed speed is set to 260
xx/min, the conventional end mill broke at a cutting distance of 100ix. When we examined this end mill, we found that the chip discharge groove 4 was clogged with a large amount of chips, and this clogging caused the cutting resistance to become too large, which is thought to be the direct cause of the breakage. . On the other hand, according to this embodiment, the feed rate is 260 mm/min.
Of course, there was no problem with each of 400 and 650 xi/min, and the cutting state was good. When I further increased the feed speed and continued the test to confirm the limit feed speed of this end mill, I found that it was 1030ix/m.
Although the end mill was broken at the end mill, the discharge groove 4 of the broken end mill was not clogged with chips at all, and in this point it is different from the conventional end mill. 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 to an increase in cutting resistance due to an increase in feed rate that 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. Also, the feed per tooth at the time of breakage is 0.2
3 mm/min, but if this is considered to be the upper limit of this embodiment, it is also possible to perform cutting at an even higher feed rate by further increasing the rotational speed. However, if the diameter of the circle inscribed in the thick core is less than 0°15D, chatter vibration occurs not due to chip evacuation but due to lack of rigidity. In the case where the distance from the side edge to the bottom edge is short and the radius of curvature of the concave surface of the discharge groove is small relative to the curl diameter of aluminum chips at high feed rates, the resistance to restrain the chips increases. Although these end mills may be usable depending on cutting conditions, the present invention considers 015D≦W≦0, 3D to be an effective range on the premise of general use at high speed and high feed. 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, their durability is incomparable. In addition, it is possible to perform dry cutting on materials such as aluminum, which has rarely been done in the past, so cleaning processes can be reduced, etc.
You can also improve the content of your work. 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 of 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 the drawing]

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, and FIG. 2 is a schematic diagram showing a cross-sectional shape perpendicular to the axis of a conventional end mill. l...Side blade, 2...Heel part, 3...Rake face, 4
...Chip discharge groove, 5.5°...concave surface, D...diameter of the blade, radius of curvature of the R-arc-shaped concave surface, W...diameter of the circle inscribed in the thick core part Fig. 2

Claims (2)

[Claims] (1) A side blade (1) extending from the tip to the rear end with a helix angle on the outer peripheral surface of the end mill body, and a chip discharge groove (4) formed along the side blade (1). ), the chip evacuation groove (
4) is formed into a concave surface (5, 5') having an arc-shaped cross section perpendicular to the axis, and the concave surface (5, 5') extends from the edge of the side blade (1) constituting this to the heel portion (2). The radius of curvature is set such that the radius of curvature is constant or increases toward An end mill that is characterized by a regulated temperature. 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 as follows:
It is formed by a concave surface (5) of a single circular arc passing through the cutting edge edge point having a constant rake angle of the side blade (1) and circumscribing a circle inscribed in the thick core part, and the radius of curvature of the circular arc is R The end mill according to claim 1, wherein the end mill is represented by =(D^2+W^2)/4(W+Dsin θ). However, R is the radius of curvature, and θ is the rake angle of the side blade.