JPS62812Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to an end mill whose cutting edge is strengthened by honing into a curved surface. [Prior Art] Cemented carbide has superior wear resistance compared to high-speed steel, but has the disadvantage of inferior toughness. When cemented carbide is used as a cutting tool material, chipping, chipping, etc. are likely to occur on the cutting edge. In particular, end mills are used with sharp cutting edges, which often causes chipping and chipping. Conventionally, the following three methods have been used to strengthen the cutting edge of throw-away tips for turning, and the honing width on the rake face is at least 0.05 mm or more.
0.03mm is necessary. (1) Barrel method in which a throw-away tip and abrasive grains are placed in a container and the container is rotated. (2) Negative branding method in which chamfering is performed using a regular diamond grinding wheel. (3) A buffing stone method in which a resilient buffing stone is pressed onto the rake surface for polishing. However, in the case of end mills, the structure of the cutting blade and the cutting mechanism are not strengthened by honing, etc., and the end mill is currently used with a sharp cutting blade. The cutting mechanism of an end mill has upward cutting and downward cutting, and the thickness of chips varies depending on the rotational position of the cutting blade, producing so-called comma-shaped chips (thicknesses at the tip and end are significantly different). In the case of upward cutting, it is advantageous to have a sharp cutting edge, especially at the starting point of cutting, because if the cutting edge is not sharp, the biting will be poor and chatter will occur. In the case of grooving, the above-mentioned phenomenon occurs at either edge of the groove, so a sharp cutting edge is required. Furthermore, in the case of downward cutting, the cutting edge is susceptible to chipping due to impact caused by interrupted cutting. An end mill has a cylindrical chuck part that is continuous with a cylindrical or conical cutting blade part, and because the chuck part and the cutting blade part are separated, the entire tool bends and deforms due to the cutting resistance generated in the cutting blade, which prevents chatter. This can easily cause the cutting edge to chip or break the tool. Therefore, the conditions required for the end mill cutting edge are:
On the one hand, the shape of the cutting edge is sharp to reduce cutting conditions, and on the other hand, the shape of the cutting edge has chipping resistance that is different from that of turning tools, etc. In order to satisfy these conflicting demands, it is necessary to Strictly accurate cutting edge shape is required. [Problems to be solved by the invention] As a result of experiments, the honing width in the rake face direction as a means of strengthening the end mill cutting edge that satisfies the above requirements is significantly smaller than the cutting edge honing width of the throw-away tip for turning, and the end mill diameter Minimum 0.003mm to 0.005mm, maximum 0.01mm to 0.03 depending on
mm, and found that it was necessary to control the honing width in the flank direction to 1/1 to 1/4 of that of the rake face. However, the three conventionally known methods for strengthening the cutting edge of an indexable tip for turning are not suitable for controlling the minute amount of grinding described above for a cutting edge of a complicated shape such as an end mill. [Means for solving the problem] The present invention can be realized by developing as a result of research a method that allows dimensional control of minute honing as in the previous method for cutting edges of complex shapes such as end mills. Ta. The details of this method will be described in a separate patent application, but the outline will be explained here: It is a method in which the cutting edge is honed using a disc-shaped brush wheel made of filament containing an abrasive. be. (Unexamined Japanese Patent Publication No. 1983-
See Publication No. 115150. ) [Operation] The honing mechanism is shown in Fig. 1. 1 is the cross section perpendicular to the cutting edge of the end mill, 2 is the rake face, 3
4 is the flank, 4 is the cutting edge, and 5 is the filament of the brush wheel. A is the abrasive grains contained in the filament of the brush,
The trajectory of the movement of the abrasive grains due to the rotation of the wheel is A,
Indicated by A', A'', and A. When the brush wheel rotates and the filament hits the cutting edge from the rake surface side, the filament bends and the abrasive grains at the tip rub and wear away the tip of the rake surface, passing through the tip. After that, the filament bends back to its original shape, so the filament tip rubs and wears away the flank side and passes.The filament contains not only A but also many abrasive grains, so many abrasive grains
Similarly, the cutting edge is worn away to form a smooth honed curved surface. By selecting the relationship between the rotation axis of the brush wheel and the position of the cutting blade, it is possible to freely select and manage the ratio of the honing width on the rake face side and the honing width on the flank side. [Example] Fig. 2 shows the honed shape of the cutting edge of an end mill in a cross section perpendicular to the cutting edge. 1 is its cross section, 2 is the rake face, 3 is the flank face, 4 is the cutting edge honing part, a is the honing width on the rake face side, and b is the honing width on the flank side. In order to find out the relationship between honing shape and cutting performance, we conducted a cutting test as shown in Figure 3. In the figure, 7 is an end mill made of cemented carbide, y is its rotation axis, 6 is a workpiece, d is the axial cut, and w is the radial cut. The cutting conditions are as follows. Down cut shoulder cutting Using cutting oil Work material: Carbon steel for machine structures JIS, S50C Hardness Rockwell C23 Cutting speed: 28.5 m/min Feed amount: 0.023 mm/1 tooth d=10 mm w=5 mm End mill: 10 mm outer diameter 2 pieces Blade Cutting edge helix angle 30 degrees Cutting length: 2000 mm As a result of the test, the ratio of the honing width a on the rake face side to the honing width b on the flank side and the size of a,
The relationship between the amount of flank wear and cutting build-up such as chipping of the cutting edge is shown in FIG. 4. In other words, in the figure, the wear amount (indicated by the average wear width on the flank side) was small (0.05 mm or less) and good cutting results were obtained when a was in the range of 3 to 30 μm and a/b was in the range of 1 to 1. The range is 4. Almost similar results were obtained under other cutting conditions. FIG. 5 shows the results of the cutting test under the same cutting conditions as in FIG. 3, with a/b=2. When a is in the range of 10 to 40 μm, the cutting result is better than that without honing. Also the third
FIG. 6 shows the results of measuring the cutting resistance when a/b=2 under the same cutting conditions as shown in the figure. The vertical axis of the graph indicates the magnitude of each cutting resistance of vertical component force, horizontal component force, and axial component force, and the horizontal axis indicates the honing width a on the rake face side. Although the cutting resistance increases somewhat due to honing compared to the conventional one without honing, the increase is not large until a is 0.03 mm, and no defects due to cutting resistance are observed. As mentioned earlier, the following are the results of a study on preventing chipping and chipping of the cutting edge, which is the main purpose of cutting edge honing. That is, according to the cutting conditions shown in Table 1, diameters of 4 mm, 10 mm and 16 mm made of cemented carbide were cut.
The relationship between the chipping rate and the honing width of the three types of end mills was investigated and shown in Figure 7. The chipping rate shown in the figure is the total length of chipped and chipped cutting edges expressed as a percentage of the total length of the cutting blade.

〔effect〕

In this invention, as mentioned above, when strengthening the end mill cutting edge by honing, the cutting edge structure and cutting mechanism are significantly different from turning and other cutting, so micromachining with even higher precision is required.
By using a new honing method that is different from the conventional method, we have developed a honing shape for the cutting edge that prevents chipping, which was considered to be a drawback of conventional end mills, and does not reduce the sharpness of the cutting edge or significantly increase cutting resistance. The condition is that the value of a is 0.003
It has been newly discovered that the a/b value is in the range of mm to 0.03 mm and a/b is in the range of 1 to 4, and it is possible to provide an extremely high-performance end mill.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the honing mechanism of the cutting edge using the brush wheel grinding method, Figure 2 is a cross-sectional view of the honed blade edge, Figure 3 is a diagram showing the end mill cutting test method, and Figure 4 is the honing width and amount of wear. Figure 5 is a graph showing the relationship between honing width and average flank wear amount, Figure 6 is a graph showing the relationship between honing width and cutting resistance, Figure 7 is φ
16 is a graph showing the relationship between honing width and defect rate for three types of end mills, φ16, φ10, and φ4. 1...Cross section perpendicular to the cutting edge of the end mill, 2...
rake face, 3... nipped face, 4... cutting edge honing section, 5... filament of brush wheel, 6...
...Workpiece material, A...Abrasive grain, a...Honing width on the rake face side, b...Honing width on the flank side, d...
...Amount of cut in the axial direction, w...Radial direction.

Claims (1)

[Scope of utility model registration request] In an end mill that has a spiral or straight ultra-hard alloy cutting blade on a cylindrical or conical surface with the rotation axis as its center line, the cutting blade part where the rake face and flank face intersect is chamfered into a curved shape. Then, the amount of chamfering in the direction of the rake face is set to 1 to 4 times the amount of chamfering in the direction of the flank face, and the chamfer width in the direction of the rake face is 0.003 mm to 0.003 mm.
A reinforced end mill with a cutting edge of 0.03mm.