JP2011020193A - Vibration-proof end mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve stability of machining and accuracy of machining with an end mill by more effectively inhibiting resonance during machining with the end mill than conventional ones. <P>SOLUTION: The end mill includes four or more cutting edges comprising an end cutting edge 3 and an outer peripheral edge 4 with a helix angle or comprising the end cutting edge 3, the outer peripheral edge 4 with a helix angle, and an arcuate corner edge 5. The cutting edges are provided at unequal division points in a circumferential direction, and installation intervals α1-α4 of all cutting edges are made different from one another. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vibration-proof end mill for a torsional blade having a function of suppressing so-called chatter vibration in use to improve processing stability and processing accuracy. The twisted blade here refers to the outer peripheral blade, and in the case of a radius end mill, the arc corner blade may or may not be twisted.

  Among known twisted blade end mills, there are a plurality of outer peripheral blades having different twist angles (unequal lead end mill) and a plurality of blades provided with unequal pitches (unequally divided end mill). The former unequal lead end mill is disclosed in the following Patent Document 1, and the latter unequal division end mill is disclosed in the following Patent Document 2 and Patent Document 3.

  In the latter end mill, the cutting edges are divided into a first group and a second group, and the cutting edges of each group are composed of two pieces arranged at the rotational center symmetrical positions. The cutting edges of the first group and the second group are arranged at unequal division points, and the cutting edges of the first and second groups are alternately arranged in the rotation direction of the tool.

Japanese Patent Publication No. 03-19002 Japanese Patent No. 4060258 JP 2007-136626 A

  The end mills disclosed in the above-mentioned Patent Documents 1 and 2 are said to suppress vibration during use and obtain a finished surface with good surface roughness. However, depending on the processing conditions, vibration is not sufficiently suppressed.

  The chatter vibration of the end mill can be suppressed by making the tool difficult to resonate. As a measure to meet the demand, the inventors have anti-vibration performance compared to the case where the outer peripheral blade is simply made of unequal leads, and the case where two groups of cutting blades are arranged with unequal division (conventional product). The structure which was excellent in was found.

  An object of the present invention is to improve the stability of machining by the end mill and the machining accuracy so that the resonance during the machining of the end mill is more effectively suppressed than the conventional product.

  In order to solve the above-mentioned problems, the present invention comprises a cutting edge composed of a bottom blade and a peripheral blade with a helix angle, or a bottom blade, a peripheral blade with a helix angle, and an arc corner blade. The cutting edges of the end mill provided with four or more cutting edges are arranged at circumferentially unequal division points, and the installation intervals of all the cutting edges are varied.

  In this end mill, it is preferable that the installation intervals of the cutting blades are different from each other in such a state that the installation intervals of the cutting blades are repeated in a large, small, large, and small arrangement in the rotation direction. Further, it is preferable that the rake angle of the outer peripheral edge is different for each cutting edge. The rake angle can also be varied from blade to blade for the bottom blade. Here, each blade does not mean that all the blades have different rake angles, and there may be a plurality of blades having the same rake angle.

  Further, each cutting edge is disposed at a position where the deviation angle from the equally divided point is within 10 °, the core thickness is 0.4D to 0.85D (D is the diameter of the end mill), and the land portion It is also preferable to set the land width of 0.1D to 0.3D.

  Since the conventional unequal lead end mill suppresses resonance only by the difference between the cutting force and the cutting time of each outer peripheral blade, it is difficult to obtain sufficient vibration isolation performance. Conventional non-uniform split end mills are simply not repeating the biting of the cutting edge of the first group and the biting of the cutting edge of the second group. Depending on the processing conditions, chatter vibrations occur.

  On the other hand, in the end mill of the present invention, since the installation intervals of all the cutting edges are different from each other, the period of biting with respect to the work material of each cutting edge becomes irregular. Therefore, compared with the conventional unequal division end mill, the vibration isolating effect is high, and the processing stability and processing accuracy are improved.

  In addition, when the rake angle of each outer peripheral blade is different, the cutting resistance for each cutting edge changes depending on the rake angle, which also contributes to the suppression of resonance. Once the setting interval of the cutting edge is set, it cannot be changed thereafter. On the other hand, there is a degree of freedom in adjusting the rake angle of the cutting edge. Therefore, even when the vibration isolation due to the setting interval of the cutting edges is insufficient, the vibration isolation performance can be improved by adjusting the rake angle of each blade. In particular, it is effective for enhancing the vibration isolation performance after regeneration by regrinding.

  In addition, the end mill in which each cutting edge is arranged at a position within 10 ° from the equally dividing point by repeating the arrangement of large, small, large, and small with respect to the installation interval of each cutting edge does not cause a large disruption of the cutting balance. .

  In addition, an end mill having an end mill diameter (effective diameter) of D, a core thickness of 0.4D to 0.85D, and a land width of a land portion of 0.1D to 0.3D has excellent rigidity and cutting edge strength. These things also improve the vibration isolation performance of the end mill.

The side view which shows the 1st form of the end mill of this invention Front view of the end mill in FIG. The figure which shows arrangement | positioning of the outer periphery blade of the end mill of FIG. Axis perpendicular cross-sectional view of a peripheral cutting edge 3 _-1 Cross-sectional view perpendicular to axis of outer peripheral blade _3-4 Axis-perpendicular sectional view showing a modification of the outer peripheral edge 3 _-1 Cross-sectional view perpendicular to the axis showing a modification of the outer peripheral edge _3-4 Side view showing a second embodiment of the end mill of the present invention Front view of the end mill of FIG. FIG. 8 is an enlarged cross-sectional view taken along line XX in FIG. (A): Measurement data of main cutting force at cutting speed of 50 m / min, (b): Measurement data of main cutting force at cutting speed of 75 m / min, (c): Cutting at cutting speed of 100 m / min. Main component force measurement data, (d): Cutting main component force measurement data at a cutting speed of 125 m / min.

Embodiments of an end mill according to the present invention will be described below with reference to FIGS. 1 to 5 show a first embodiment in which the present invention is applied to a square end mill. The end mill 1 of the first form has a bottom blade 3 and a gash 6 at the tip of a body 2. Further, the outer periphery 4 of the body 2 is twisted at a predetermined angle, the land portion 7 and the groove 8 are twisted. A shank 9 is connected to the rear part of the body 2. The outer peripheral blades 4 are connected to the radially outer ends of the bottom blades 3 at the corresponding positions. In addition, about the bottom blade 3, the outer periphery blade 4, and the land part 7, in order to distinguish each blade and each land part, the additional symbol of _-1 to _-4 is attached | subjected as needed.

  As shown in FIG. 2, the bottom blade 3 has all the blades arranged at unequal division points, and the installation intervals in the circumferential direction of all the cutting blades are different from each other. For example, in FIG. 2, the installation interval is set to the interval α1 = 86 °, the interval α2 = 94 °, the interval α3 = 88 °, and the interval α4 = 92 °, but is not limited to this value. The installation point of the cutting edge may be deviated forward and backward from the equally dividing point (the dividing point at 90 ° pitch because the illustrated end mill has four blades). In this case, the deviation angle is preferably 10 ° or less from the equally divided point in the forward and backward directions.

The end mill of FIG. 1 sets the core thickness t shown in FIG.
The land width w1 of the land portion _{7 -1} bottom edge 3 _-1 and the peripheral blades 4 _-1 is formed 0.23D, the end cutting edge _3-2 and the land portion _{7 -2} that the peripheral cutting edge 4 _-2 is formed forming 0.2D a land width w2, the land width w3 of the bottom blade 3 _-3 and the land portion _{7 -3} peripheral cutting edge 4 _-3 is formed 0.22D, the end cutting edge 3 _-4 and peripheral cutting edge _4-4 It is set respectively land width w4 of the land portion _7-4 that is to 0.18D. Both the core thickness t and the land width w are within the preferred range of the present invention.

  The outer peripheral blade 4 is connected to the outer end of the bottom blade 3. Therefore, this outer peripheral blade 4 is also in a position that maintains an unequal interval (α1 to α4 in FIG. 3) as with the bottom blade 3. In the illustrated outer peripheral blade 4, all the blades are twisted at the same angle. In addition, the rake angle β (see FIGS. 4 and 5) of all the outer peripheral blades 4 is unified at a constant 12 ° here.

The rake angle β of the outer peripheral blade 4 may be varied for each blade as shown in FIGS. 6 and 7. In that case, for example, a rake angle beta = 12 ° for peripheral cutting edge _{4 -1} and _{4 -3,} may be set such rake angle beta = 10 ° for peripheral cutting edge _{4 -2} and _{4 -4,} status Depending on the case, it is possible to make the rake angles of all the peripheral blades different from each other.

  It is not necessary to vary the rake angle of the outer peripheral blade if the vibration isolation by setting the installation interval of the cutting blade is sufficient. If the rake angle of the outer peripheral blade is made different when it is considered that the vibration isolation by setting the installation interval of the cutting blades is insufficient, the effect which is insufficient in setting the installation interval can be compensated for.

  8 to 10 show a second embodiment in which the present invention is applied to a radius end mill. The end mill 1 of the second form has an arcuate corner blade 5 between the bottom blade 3 and the outer peripheral blade 4.

The outer peripheral blade 4 is also four here. The peripheral blades 4 having different twist angles θ1 and θ2 (in the embodiment, θ1 = 45 °, θ2 = 42 °) are alternately arranged in the tool rotation direction. The outer peripheral edge _{4 -1} and _{4 -3,} rake angle beta of 10 °, and _{4 -4} peripheral cutting edge _{4 -2,} have been respectively set to 8 ° rake angle beta, anti-vibration by unequal lead Anti-vibration effect due to the effect and unequal rake angle is also obtained.

  The bottom blade 3 can also have a different rake angle for each cutting blade. However, the cutting burden on the outer peripheral blade is generally larger than that on the bottom blade. Therefore, a better effect can be expected when the unequal rake angle is applied to the outer peripheral blade.

  A four-blade square end mill having a diameter D = φ10 mm, a core thickness t = 7 mm, and a total length of 75 mm was prototyped. The prototype end mills were three types of samples No. 1 to No. 3. Sample No. 1 is a comparative product in which cutting edges are arranged at equal intervals, the land width of each land portion is 2.1 mm, and the rake angle of each outer peripheral blade is 10 °.

  In Sample No. 2, all cutting edges were arranged at unequal intervals (Invention 1). In the arrangement, the intervals α1 to α4 in FIGS. 2 and 3 are set to 86 °, 94 °, 88 °, and 92 ° in this order, and the land widths w1 to w4 in FIG. .19 mm, 0.22 mm, and 0.18 mm, and the rake angles of the outer peripheral blades are all 10 degrees.

Sample No. 3 is Invention 2 and all cutting edges are arranged at unequal intervals under the same conditions as Invention 1. As for this, the rake angle are both 12 ° of the peripheral blades _{4 -1} and _{4 -3} of FIG. 3, the rake angle of peripheral cutting edge _{4 -2} and _{4 -4} are both set to 8 °. The land widths w1 to w4 in FIG. 3 are sequentially set to 0.23 mm, 0.2 mm, 0.22 mm, and 0.18 mm, and there is no difference from the sample No. 2.

Using the samples No. 1 to No. 3, cutting was performed under the following conditions.
Processing machine: Machining center with BT40 spindle Work material: Ti-6Al-4V
Feed per blade fz: 0.04 mm / blade Axial cutting depth ap: 15 mm
Radial cutting depth ae: 1 mm
Tool protrusion: 50mm

  The cutting principal component force (cutting resistance) when processing using the above-mentioned end mill was measured with a cutting dynamometer. The result is shown in FIG. 11A shows data at a cutting speed Vc of 50 m / min, FIG. 11B shows data at a cutting speed Vc of 75 m / min, and FIG. 11C shows data at a cutting speed Vc of 100 m / min. FIG. 4D shows data when the cutting speed Vc is 125 m / min. In each figure, I is measurement data of sample No. 3 (invention product 2), II is measurement data of sample No. 2 (invention product 1), and III is measurement data of sample No. I (comparative product).

  Compared to sample No. 1, sample Nos. 2 and 3 have a stable main component force and a smaller absolute value of resistance at any cutting speed.

  Further, in comparison between sample No. 2 and sample No. 3, sample No. 3 has a smaller absolute value and amplitude of resistance at any cutting speed, and unequally spaced arrangement of all cutting edges and scooping of outer peripheral blades. A better effect is obtained by using the angle change together.

DESCRIPTION OF SYMBOLS 1 End mill 2 Body 3 Bottom blade 4 Perimeter blade 5 Corner blade 6 Gash 7 Land part 8 Groove 9 Shank D End mill diameter α Cutting blade installation interval β Peripheral blade rake angle θ Peripheral blade twist angle w Land width t Center thickness

Claims (4)

Cutting edge composed of a bottom blade (3) and an outer peripheral blade (4) with a twist angle, or a bottom blade (3), an outer peripheral blade (4) with a twist angle and an arc corner blade (5) An end mill having four or more cutting edges composed of
A twisting blade end mill, wherein the cutting edges are arranged at unequal division points in the circumferential direction, and the installation intervals (α) of all cutting edges are different from each other.   The twisted blade end mill according to claim 1, wherein a rake angle (β) of the outer peripheral blade (4) is varied for each cutting blade.   The twisted blade end mill according to claim 1 or 2, wherein the cutting blade is arranged at a position where a deviation angle from an equal division point is within 10 ° by repeating a large, small, large, and small arrangement for each installation interval. .   The diameter of the end mill is (D), the core thickness (t) is set to 0.4D to 0.85D, and the land width (w) of the land portion (7) is set to 0.1D to 0.3D. The twisted blade end mill according to any one of 3 above.

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