JPH10217027A - Rotary cutting tool with vibration control mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary cutting tool capable of controlling vibration and the resonance of a holder caused following cutting by providing a mechanical fixing means at the end part of a shank part. SOLUTION: A cylindrical shank part 1 is provided from a blade body holding part 5, also a cemented-carbide-made shank part 2 is provided on the outer peripheral side of the shank part 1; and the holding part 5 and the shank part 1 are integrally formed to fix the holding and shank parts 5 and 2 also the shank parts 1 and 2 together by a brazing part 3. A screw is provided on another end of the shank part 1 to be fastened by a double nut 4 to give force. Resonance can be reduced, and cutting can be made in a condition where the condition is stabilized as adding a load, by adjusting the fastening force of the nut 4 to about 30, 40, 50, and 70kgfcm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to control of vibration, chatter and the like of a throw-away end mill.

[0002]

2. Description of the Related Art Some throw-away end mills, solid carbide end mills, and the like are used in applications where the protrusion amount is several times to tens of times the diameter. Its application is when a long overhang is required due to interference due to the shape of the part, or when it is a three-dimensional process involving axial cutting. Other processes must be performed with the overhang that can process the deepest part. Efficiency is reduced. Accompanying this, as an improvement of the shank part,
And Japanese Patent Application Laid-Open No. H08-1425, the rigidity of which is partially increased by using a material having a high Young's modulus such as a cemented carbide.

In cutting with a long overhang,
In order to reduce adverse effects on cutting such as vibration and chatter, it is generally performed as a troubleshooting method to reduce cutting vibrations by adjusting cutting specifications, for example, a cutting speed and a feed amount. Such a method is effective by adjusting the resistance associated with cutting, particularly the resistance of the holder to the feed force. However, in the case of cutting with a long protrusion amount, if the shank portion is made only of a material having a high vibration-proof property, the rigidity is reduced, so that chatter is more likely to occur, resulting in a negative result.

[0004]

In order to achieve this, it is necessary to absorb or attenuate the vibrations caused by cutting while utilizing the high rigidity. Carbide with high Young's modulus improves rigidity, but has a limit in preventing vibration and the like.In addition, in the case of a commonly used holder made of only cemented carbide, when the protrusion amount is small, both rigidity and vibration are reduced. Although satisfactory performance is exhibited, as the amount of protrusion increases, high Young's modulus tends to cause high-frequency vibration, and there is a problem that tool performance is significantly reduced due to the vibration.

[0005]

SUMMARY OF THE INVENTION Therefore, in the present invention, rotary cutting for controlling vibration while maintaining high rigidity is provided by utilizing the characteristics of steel and carbide and providing means for adjusting rigidity and natural frequency. It is an object of the present invention to provide a rotary cutting tool in which vibration generated during cutting and resonance of a holder are controlled.

[0006]

As described above, the present invention comprises a blade holder holding a cutting blade at one end of a cylindrical shank 1 and a shank 2 held by a machine tool body. Cutting tool, wherein the other one of the shank portion 1
A mechanical fixing means is provided at the end, and more specifically, is fixed by a method capable of controlling the tightening force, and the vibration is controlled by adjusting the tightening force. The shank portion 1 and the shank portion 2 are made of different materials. For example, for the shank portion 1 and the blade body holding portion, structural steel, high-strength steel, a material excellent in vibration absorption, 13 chrome martensitic stainless steel, and the like. For the shank portion 2, a material having high rigidity such as a cemented carbide is used for the purpose.

[0007]

As a means for adjusting the characteristics, a mechanical fixing means is used for the shank part 1, more specifically, by using a double nut capable of changing the tightening force, the shank part 1 and the shank part 2 can be connected. It is connected so that the load applied to the shank can be adjusted. Even if the shank part 1 and the blade body holding part are provided integrally,
Alternatively, a separately manufactured one may be mechanically fixed. A shank portion 2 is fixed to the outer periphery of the shank portion 1. Since the shank portion 2 is a portion held by the machine tool main body, a material such as a highly rigid cemented carbide is used. The shank part 1
The other end is provided several tens of millimeters longer than the shank portion 2, and mechanical fixing means is provided to apply a load to the shank portion 2. A double nut is used as the mechanical fixing means. The double nut is used to prevent loosening due to vibration or the like during cutting. Hereinafter, the reason for the limitation will be described.

Further, the shank portion 1 and the shank portion 2 may be fixed by mechanical fixing or joining such as brazing. If the diameter is small, the space is limited, so brazing etc. is easy and sufficient joining strength can be obtained, but if the diameter is relatively large, there is enough space,
Further, in the case of brazing or the like, the bonding area becomes too large, so that mechanical fixing is preferable. The shank 1 and the shank 2 were selected in consideration of the vibration absorption and rigidity. However, the shank 1 and the shank 2 cannot be used for the holder main body because they are rotary cutting tools in terms of damping. If such a material is used in, for example, a gap between the shank portion 1 and the shank portion 2, vibration can be further absorbed.
Furthermore, by applying a film by a physical vapor deposition method, a residual compressive stress can be given. The degree of the compressive stress can be adjusted because it can be changed depending on the quality and thickness of the film. Hereinafter, the present invention will be described in detail based on examples.

[0009]

1 is a partial sectional view of a holder according to the present invention. FIG. 1 shows an example in which the blade diameter is 42 mm. There is a cylindrical shank portion 1 from the blade body holding portion, a shank portion 2 made of cemented carbide is provided on the outer peripheral side, and the blade body holding portion and the shank portion 1 are integrated. The blade body holding portion and the shank portion 2 and the shank portion 1 and the shank portion 2 are both fixed by the brazing portion 3. The other end of the shank portion 1 is provided with a screw, which is tightened by the double nut 4 to apply a force.
In addition, as the blade shape of the example, a radius ball end mill shape using a generally used round tip was used.

[0010] Next, using the holder of Example 1, the protrusion amount was four times the blade diameter (168 mm) and the nut was tightened with a force of 20 kgfcm. The cutting specification is a cutting speed of 10
0m / min, feed amount per blade 0.05mm / blade,
The cutting was performed with a workpiece S50C (HB220) having an axial depth of cut of 5 mm and a radial depth of cut of 2 mm. In order to evaluate the resonance, the cutting noise during the work material length of 300 mm was measured using a sound level meter, and the change (dB) of the cutting noise from the beginning to the end of cutting was measured. For comparison, a carbide shank having the same shape was also tested. At the beginning of cutting, there is no chatter, so it is quiet. However, when cutting is performed to some extent, the sound is loud due to resonance, and a high sound is generated, causing chatter. If the cutting is continued as it is, the cutting edge will be chipped or the chip will be broken, resulting in a much higher sound. This is shown in FIG. From FIG.
In the example of the present invention, although stable cutting was obtained although it became slightly larger from the beginning of cutting, the steel shank was in a state where vibration was increased and cutting could not be performed, and the carbide shank was in a state of chatter which was unique to chatter. ”, The dB value increased.

Next, cutting was performed by changing the feed amount so as to apply a load at the time of cutting. The result is shown in FIG.
Shown in With a tightening force of 20 kgfcm in this embodiment,
Although the resonance is slightly increased by the feed of 0.1 mm / blade and 0.15 mm / blade, it is in a state where it can be used somehow.
At 2 mm / blade, resonance increased and cutting had to be stopped halfway. With the same feed amount, tighten the nut with a force of 30kgfcm, 40kgfcm, 50kgf
By adjusting the height to 70 kgfcm, the resonance is reduced, and cutting can be performed in a more stable state as the load is applied as shown in FIG.

[0013]

By applying the present invention, it is highly rigid and hard to chatter when the amount of protrusion is large.
Satisfactory performance was obtained with vibration. In addition, the weight can be reduced and the processing can be facilitated by forming the superhard portion into a columnar shape. Furthermore, when used for three-dimensional machining, etc., the feed can be set high even with a large protrusion amount caused by interference, and highly efficient machining can be performed.

[Brief description of the drawings]

FIG. 1 is a front view including a partial cross section of an embodiment of the present invention.

FIG. 2 shows the result of measuring the cutting noise with a sound level meter.

FIG. 3 shows the result of measuring the cutting noise with a sound level meter.

[Explanation of symbols]

 1 shank part (steel) 2 shank part (carbide) 3 brazing part 4 double nut 5 blade holder

Claims (2)

[Claims] 1. A cutting tool comprising: a blade holding portion having a cutting edge at one end of a cylindrical shank portion 1; and a shank portion 2 held by a machine tool main body. A mechanical cutting means is provided at the other end of the rotary cutting tool with a vibration damping mechanism. 2. The rotary cutting tool with a vibration damping mechanism according to claim 1, wherein the shank portion 1 is made of 13 chrome martensitic stainless steel.