JP5381132B2 - Roughing end mill - Google Patents

Description

  The present invention relates to a roughing end mill used for intermediate finishing of a work material, in which an outer peripheral edge that is corrugated in the end mill rotation direction is formed on the outer periphery of a tip end of an end mill body that is rotated around an axis. It is.

  As this type of roughing end mill, for example, Patent Document 1 has a substantially spirally extending cutting edge (outer peripheral cutting edge) positioned at a uniform radial distance from the central axis of the main body, and at least one cutting edge is It has been proposed to have a substantially sinusoidal shape and have rake faces alternately provided with positive and negative rake corners.

  In such a luffing end mill, since the thickness of the chip changes between a convex portion and a concave portion of the sine curve formed by the cutting edge, good chip disposability can be obtained. Further, in this Patent Document 1, if all the sinusoidal blades are located at the same distance from the center axis of the cutting tool (that is, if the height on the radius along the cutting blade is uniform), the workpiece Is also described that the surface is molded relatively smoothly.

JP-A-62-68217

  However, in the roughing end mill described in Patent Document 1, the negative rake angle portion is positioned at the peak of the sinusoidal shape formed by the cutting edge, and the positive rake angle portion is conversely a sinusoidal valley. Is positioned. For this reason, cutting resistance is remarkably increased or the cutting edge bites into the work piece at the peak portion of the sinusoidal shape that generates chips with a large thickness among the cutting edges, that is, the convex portion of the waveform. There is a risk that shocking load may occur and chatter vibration or the like may occur.

  Further, when the cutting edge that is spirally twisted so as to go in the rotational direction of the end mill as it goes toward the rear end side in the axial direction is formed in a waveform like a sinusoidal shape, it is directed toward the rear end side in the axial direction. In contrast, the torsion angle of the cutting edge is maximized between the convex part and the concave part of the corrugation, while conversely, the torsion angle of the cutting edge is minimum between the concave part and the convex part. The cutting resistance increases.

  However, in the roughing end mill described in Patent Document 1, the rake angle of the cutting edge is intermediate between the negative rake angle portion and the positive rake angle portion in a portion where the corrugation becomes convex from concave to convex. Around 0 °. For this reason, the cutting edge strength between the concave and convex portions of the corrugation is less than that of the crest, and chipping and chipping are likely to occur due to the cutting resistance, while the corrugation is between the convex and concave portions. Compared with the part, the sharpness is dull, and the cutting resistance cannot be effectively reduced.

  The present invention has been made under such a background, and can prevent chipping or chipping of the outer peripheral blade and reduce the cutting resistance itself. Further, chatter vibration due to an impact load when the outer peripheral blade bites. An object of the present invention is to provide a luffing end mill capable of preventing the occurrence of the above.

In order to solve the above-mentioned problems and achieve such an object, the present invention provides an end mill rotation direction on the outer periphery of the end portion of the end mill body rotated about the axis line from the front end of the end mill body toward the rear end side. A chip discharge groove that twists to the rear side is formed, and a wall surface facing the end mill rotation direction of the chip discharge groove is defined as a rake face, and a ridge portion on the outer peripheral side of the rake face is directed in a direction in which the chip discharge groove is twisted. a roughing end mill peripheral cutting edge is formed for irregularities in the end mill rotating direction forms a waveform while twisting, the outer peripheral rake angle of the peripheral cutting edge is maximized at the position where the helix angle of the outer circumferential edge is maximum, the It is characterized in that it is changed so as to be minimized at a position where the twist angle of the outer peripheral blade is minimized.

That is, in the roughing end mill of the present invention, the outer peripheral rake angle of the outer peripheral blade is such that the torsion angle between the convex portion and the concave portion of the outer peripheral blade that forms a waveform toward the rear end side in the axial direction. Since it is set to the maximum at the maximum position, the sharpness of the outer peripheral blade can be improved, and the cutting resistance can be reduced. On the other hand, at the position where the torsion angle is minimized between the concave is convex from the portion of the peripheral cutting edge in the opposite, since the cutting edge strength outer peripheral rake angle is minimized is secured, it size as described above It is possible to prevent chipping and chipping even with respect to cutting resistance.

Further, in the portion where the waveform of the outer peripheral blade between the portions where the rake angle is maximum and minimum is concave and the portion where the rake angle is convex, the outer peripheral rake angle is intermediate between the maximum value and the minimum value. For this reason, it is possible to prevent an increase in the cutting resistance by preventing the outer peripheral rake angle from becoming larger on the negative angle side than necessary, especially in the portion where the outer peripheral blade is convex, and an impact load acts when biting. The occurrence of chatter vibration and the like can be prevented.

Here, it is desirable that the outer peripheral rake angle is changed within a range of a positive rake angle of 2 to 22 °. That is, as in the roughing end mill described in Patent Document 1, when the outer peripheral rake angle changes from 0 ° to a negative angle, the waveform of the outer peripheral blade is particularly concave from the concave toward the rear end side in the axial direction. Even if the cutting edge strength can be ensured at the position where the twist angle is minimum between the convex portions, the cutting resistance may increase.

  As described above, according to the present invention, generation of chatter vibration, chipping of the outer peripheral edge, and chipping can be prevented, and the overall cutting resistance can be effectively reduced. Can be performed stably and smoothly.

It is a side view which shows one Embodiment of this invention. It is a figure which shows the relationship between the twist angle (dashed line) of an outer periphery blade in an embodiment shown in FIG. 1, and an outer periphery rake angle (dashed line).

  In the luffing end mill of the present embodiment, the end mill body 1 is integrally formed in a substantially cylindrical shape centering on the axis O with a hard material such as cemented carbide, and the rear end side (right side in FIG. 1) is the end mill body. 1 is a shank portion 2 for mounting on a spindle of a machine tool, and a tip end side (left side in FIG. 1) is a cutting edge portion 3, and an end mill rotating direction indicated by a symbol T around an axis O by the machine tool. The workpiece is cut by the cutting blade portion 3 by being fed out while being rotated.

  On the outer periphery of the cutting blade portion 3, there are a plurality of (four in this embodiment) chip discharge grooves 4 that are twisted to the rear side in the end mill rotation direction T around the axis O from the front end toward the rear end. It is formed at equal intervals in the circumferential direction. And the cross ridgeline part of the wall surface which faces the end mill rotation direction T side of these chip discharge grooves 4 and the outer peripheral surface (outer peripheral flank surface) of the cutting edge part 3 connected to the end mill rotation direction T rear side, that is, the above wall surface An outer peripheral edge 6 having this wall surface as an outer peripheral edge rake face 5 is formed on the outer peripheral side ridge portion, as in the case of the chip discharge groove 4, toward the rear side in the end mill rotation direction T around the axis O as a whole. It is formed to be twisted.

  In addition, a gash 7 is formed so that the inner peripheral side of the tip side opening of each chip discharge groove 4 is shaved and widened at the tip of the cutting edge 3, that is, the most distal end of the end mill body 1. A wall surface facing the end mill rotation direction T side of the gasche 7 is a bottom edge rake surface 8. Further, at the tip side ridge portion of the wall surface facing the end mill rotation direction T side of the chip discharge groove 4 including the bottom blade rake face 8, the axis line extends from the tip of the outer peripheral blade 6 toward the axis O in the radial direction. A bottom blade 9 extending to the vicinity of O is formed.

  Here, the outer peripheral blade 6 has a constant twist angle (for example, 30 °) with respect to the axis O, with respect to a reference line that twists toward the rear side in the end mill rotation direction T as it goes toward the rear end in the axis O direction. A waveform is formed on the front side and the rear side in the end mill rotation direction T so as to form a sine curve. However, the rotation trajectory of the outer peripheral blade 6 around the axis O is formed in a cylindrical shape centered on the axis O, that is, the outer diameter of the outer peripheral blade 6 is constant.

  Therefore, the actual twist angle θ of the outer peripheral blade 6 is determined from the peak 6A of the corrugated convex and concave portions formed by the outer peripheral blade 6 in the direction of the axis O with reference to the constant twist angle as shown by a broken line in FIG. The size gradually increases toward the rear end side, and is maximized at an intermediate portion (midpoint) 6a between the peak portion 6A and the valley bottom portion 6B of the concave and convex portions. Further, the torsion angle θ of the outer peripheral blade 6 gradually decreases from the intermediate part 6a toward the valley bottom part 6B of the recess, and after reaching the constant torsion angle at the valley bottom part 6B, the rear end side in the direction of the axis O It becomes further smaller toward the bottom and becomes the minimum at an intermediate portion (midpoint) 6b between the valley bottom portion 6B and the peak portion 6A of the next uneven convex portion.

  Further, the torsion angle θ gradually increases from the intermediate portion 6b toward the rear end side, and after returning to the constant torsion angle again at the next peak portion 6A, the next peak portion 6A and further next It becomes the maximum in the intermediate part 6a with the valley bottom part 6B of the concave part, and this is repeated. In the present embodiment, the change in the twist angle θ of the outer peripheral blade 6 is a smooth uneven curve as shown in FIG.

Then, with respect to such a change in the twist angle θ of the outer peripheral blade 6, the outer peripheral rake angle α of the outer peripheral blade 6 forms an unevenness combined with the change in the twist angle θ as shown by a one-dot chain line in FIG. It has a curved shape. That is, the outer peripheral rake angle α is also increased or decreased based on a certain rake angle (for example, 12 °). However, in the present embodiment, the outer peripheral rake angle α is changed within a range of a positive rake angle of 2 to 22 °.

Therefore, the outer peripheral rake angle α also gradually increases from the peak portion 6A of the undulating convex portion formed by the outer peripheral blade 6 toward the rear end side in the axis O direction, and the peak portion 6A and the next concave portion It becomes maximum at the position of the middle part (midpoint) 6a with the valley bottom part 6B. Further, the width gradually decreases from the intermediate portion 6a toward the valley bottom portion 6B of the next concave portion, and approximately reaches the constant rake angle at the valley bottom portion 6B.

Subsequently, the outer peripheral rake angle α is further reduced from the valley bottom 6B toward the rear end side in the axis O direction, and an intermediate portion (midpoint) 6b between the valley bottom 6B and the peak portion 6A of the next convex portion. The outer peripheral rake angle α gradually increases from the intermediate portion 6b toward the rear end side, and reaches the predetermined rake angle again at the peak portion 6A of the next convex portion. Thereafter, the outer peripheral rake angle α becomes maximum at the intermediate portion 6a between the next peak portion 6A and the valley bottom portion 6B of the next concave portion, and this is repeated.

The corrugated shape of the outer peripheral blades 6 and the change of the twist angle θ and the outer peripheral rake angle α are common, but the outer peripheral blades 6 adjacent to each other in the circumferential direction form the corrugated shape formed by the outer peripheral blades 6. Are shifted in the direction of the axis O. That is, the peak part 6A, the valley bottom part 6B, and the intermediate parts 6a and 6b are shifted in the direction of the axis O between the adjacent outer peripheral blades 6 with the same interval therebetween.

  For example, in the present embodiment in which the four outer peripheral blades 6 are formed at equal intervals in the circumferential direction, the phases of the outer peripheral blades 6 positioned on opposite sides of the axis O are matched and adjacent in the circumferential direction. In the peripheral blades 6, even if one peak top 6 </ b> A and the other valley bottom 6 </ b> B, and one valley bottom 6 </ b> B and the other peak 6 </ b> A have the same position in the axis O direction. Well, even if the phases of all the outer peripheral blades 6 are shifted so that the positions of the peak portions 6A, the valley bottom portions 6B, and the intermediate portions 6a, 6b of the respective outer peripheral blades 6 are the same in the direction of the axis O. Good.

In the luffing end mill configured as described above, good chip disposal is ensured by the wavyly irregular outer peripheral blade 6, and the outer peripheral rake angle α of the outer peripheral blade 6 is the twist angle θ of the outer peripheral blade 6. Is maximized at the position of the intermediate portion 6a from the peak portion 6A to the valley bottom portion 6B, and the sharpness of the outer peripheral blade 6 is further enhanced in the intermediate portion 6a given a sharpness by a large twist angle θ. be able to. For this reason, it becomes possible to significantly reduce the cutting resistance and perform a smooth intermediate finishing of the work material.

On the other hand, the cutting force acting on the outer peripheral blade 6 tends to increase in the intermediate portion 6b where the twist angle θ is minimum, whereas in the roughing end mill configured as described above, the outer peripheral rake angle α in the intermediate portion 6b. Therefore, the highest cutting edge strength among the outer peripheral blades 6 can be ensured. For this reason, even if a large cutting force acts, it is possible to prevent the outer peripheral blade 6 from being chipped or chipped, and to perform the above-mentioned smooth and intermediate finishing of the work material stably.

Further, at the crest portion 6A and the valley bottom portion 6B of the wavy outer peripheral blade 6 between these intermediate portions 6a and 6b, the torsion angle θ is made equal to the constant torsion angle of the reference line, and the outer peripheral rake angle α is also It is made equal to a fixed rake angle as a reference, and is set to an intermediate size between the maximum and minimum rake angles. For this reason, it is possible to prevent a shocking load from acting on the outer peripheral blade 6 and cause chatter vibration around the peak 6A where particularly thick chips are generated, and the cutting resistance is reduced. It is possible to prevent an excessive increase, and it is possible to further reduce the resistance acting on the entire end mill body 1.

Moreover, in the present embodiment, the outer peripheral rake angle α of the outer peripheral blade 6 is changed within a range of 2 to 22 ° positive rake angle, and the rake angle is negative like the roughing end mill described in Patent Document 1. Since there is no corner portion, a certain degree of sharpness can be secured even in the intermediate portion 6b having the minimum outer peripheral rake angle α. Accordingly, the cutting resistance can be reduced over the entire length of the outer peripheral blade 6, so that the smooth cutting process as described above can be promoted more reliably.

That is, if there is a portion where the outer peripheral rake angle α of the outer peripheral blade 6 is smaller than the above range, that is, if the outer peripheral rake angle α in the intermediate portion 6b becomes too large on the negative angle side, the cutting resistance over the entire length is reduced . There is a risk of reducing the reduction. On the other hand, if the outer peripheral rake angle α of the outer peripheral blade 6 is larger than the above range, that is, if the outer peripheral rake angle α in the intermediate portion 6a becomes too large on the positive side, the intermediate blade 6 There is a risk that the strength becomes insufficient and chipping and chipping cannot be reliably prevented. In order to achieve the above effect more reliably, it is more desirable that the outer peripheral rake angle α of the outer peripheral blade 6 is changed within a range of 5 to 20 °, and more preferably within a range of 7 to 18 °. More desirable.

Of course, the position at which the torsion angle θ of the outer peripheral blade 6 is maximized, the position at which the outer periphery rake angle α is maximized, and the position at which the torsion angle θ is minimized and the position at which the outer periphery rake angle α is minimized are exactly the same. Although it is desirable that it be allowed to occur, it is inevitable that some errors will occur. However, if this error becomes too large, the above-described effect may be impaired. Therefore, the error in the direction of the axis O at these positions is caused by the wavelength of the waveform formed by the outer peripheral blade 6 (for example, from the peak 6A to the rear end side). It is desirable that the range is ± 10% or less with respect to (the length along the reference line up to the next peak 6A).

DESCRIPTION OF SYMBOLS 1 End mill main body 3 Cutting edge part 4 Chip discharge groove 5 Peripheral blade scoop surface 6 Outer peripheral blade 6A The corrugated peak part which the outer peripheral blade 6 makes 6B The corrugated trough part 6a which the outer peripheral blade 6 makes 6a Peak toward the rear end side of the axis O direction Intermediate part between the part 6A and the valley bottom part 6B (position where the torsion angle θ and the outer peripheral rake angle α of the outer peripheral blade 6 are maximized)
6b An intermediate part between the valley bottom part 6B and the peak part 6A toward the rear end side in the axis O direction (position where the torsion angle θ of the outer peripheral edge 6 and the outer peripheral rake angle α are minimized)
9 the outer circumference of the end cutting edge O endmill torsional angle α peripheral cutting edge 6 of the axis T end mill rotating direction θ peripheral cutting edge 6 of the main body 1 rake angle

Claims (2)

A chip discharge groove that twists toward the rear side in the end mill rotation direction from the front end of the end mill body toward the rear end side is formed on the outer periphery of the end portion of the end mill main body rotated about the axis. A roughing end mill having a facing wall as a rake face, and an outer peripheral edge that is undulated in the direction of rotation of the end mill by forming a waveform while twisting toward the direction in which the chip discharge groove is twisted at the ridge on the outer peripheral side of the rake face a is, the outer peripheral rake angle of the peripheral cutting edge is maximum at the position where the helix angle of the outer circumferential edge is maximum, are varied to smallest at a position where the helix angle of the outer circumferential edge is minimized Roughing end mill characterized by that. The roughing end mill according to claim 1, wherein the outer peripheral rake angle is changed within a range of a positive rake angle of 2 to 22 °.

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