JPH084967B2 - End mill - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an end mill used for groove cutting and side surface cutting, and more particularly to an end mill suitable for finishing a high hardness material such as a mold.

[Prior Art] When processing a plastic mold, a rubber mold, or the like, rib processing for forming a deep groove 2 in a mold 1 is performed as shown in FIG. 6, for example. Since it is difficult to secure the surface roughness of the groove wall surface 3 by a normal cutting process, the finishing process of the groove 2 has conventionally relied solely on electric discharge machining.

However, electric discharge machining has a drawback that it requires a long machining time and the machining cost is extremely high. For this reason, various end mills have recently been provided, which are particularly suitable for finish processing during rib processing.

FIGS. 7 and 8 show an example of an end mill proposed for such rib processing. The end mill 4 shown in these figures is a spindle of a machine tool (not shown).
A blade portion 7 having a regular polygonal shape (regular hexagon in the example shown) in a cross section orthogonal to the tool axis O at the tip of a tool body 6 having a substantially cylindrical shank 5 fitted to the base end. Are formed, and six outer peripheral blades 9 extending over the entire length of the blade portion 7 are formed on the ridge line portion where the respective side surfaces 8 of the blade portion 7 intersect with each other. The taper shaft-shaped rotation locus is drawn around the tool axis O corresponding to the above shape, and the tool axis O is inclined by a predetermined angle.

When the groove 2 is processed by using such an end mill, the tool body 6 is rotated about the axis O in the direction of arrow A, and the groove is formed between the tool body 6 and the groove 2. 2 is given relative movement in the longitudinal direction,
Thereby, each outer peripheral blade 9 cuts the wall surface 3 to form the groove 2. The depth of cut in this case is extremely small and is closer to the area of grinding rather than cutting.
Further, the reason why the blade portion 7 has a polygonal cross section is that the blade edge angle of the blade outer peripheral blade 9 is increased to eliminate chatter vibration during cutting and improve the surface roughness of the finished surface.

Here, the number of the cutting edges 9 is set to 6 in the illustrated example, but the number is not limited to this, and various types of 3 or more are provided.

[Problems to be Solved by the Invention] In any of the rib milling end mills such as the above-described conventional end mill 4, the blade portion 7 is formed in a prismatic shape having a regular polygonal shape in cross section, so that the cutting blade is 9 rake angle θ1, that is, a cross section orthogonal to the axis O of the blade 7 (8th
In the figure), the line segment that connects each cutting edge 9 from the tool rotation center P0
Side face extending from cutting edge 9 to the front side in the tool rotation direction with respect to l1
The angle formed by 8a is half the apex angle in the regular polygonal cross section, and if the number of cutting blades 9 is n and the angle from the line segment 11 to the cutting blade 9 in the counterclockwise direction is positive, then θ1 = −π × (n-1) / n (rad.) ...

Further, the clearance angle θ2 of the cutting edge 9, that is, the angle formed by the side surface 8b extending from the cutting edge 9 to the rear side in the tool rotation direction with respect to the line segment 12 that passes through the cutting edge 9 and is orthogonal to the line segment 11 is 90.゜ (π
/ 2 rad.) Minus the rake angle θ1 and the number of cutting edges 9 is n, then θ2 = π × (2-n) / 2n (rad.).

As described above, in the conventional end mill, the rake angle θ1 and the clearance angle θ2 are determined by the number n of the cutting blades 9 as long as the blade portion 7 is formed in a regular polygonal shape. (Θ1 + θ3) is extremely small, the strength of the cutting edge is insufficient, chatter vibration is likely to occur, and chipping of the cutting edge is likely to occur.

Further, particularly in an end mill in which a bottom blade is provided at the tip of the blade portion 7, even if an attempt is made to send a tool in the axial direction to form a taper groove at a time in order to improve cutting efficiency, the peripheral blade tip portion Since the amount of feed in the tool axis direction cannot be set to a large value due to insufficient strength, after all, after performing the undercutting such as grooving the work material with a tool with a small diameter, expand this with an end mill to form a tapered groove. There was also the problem that it was unavoidable.

This invention was made under such a background,
It is an object of the present invention to provide an end mill that can maintain a constant blade edge angle even if the number of blades changes and is excellent in blade edge strength.

[Means for Solving the Problems] The present invention for solving the above problems, in an end mill having a tool blade tip surface with a bottom blade and a gash, has a rake angle of -30 ° to -50 ° at the outer peripheral blade tip. The clearance angle of the tip of the outer peripheral blade is set in the range of 20 ° to 35 °.

[Operation] According to the configuration of the present invention, by setting the rake angle and the clearance angle of the outer peripheral blade tip portion within the above ranges, a constant blade edge angle is secured at the outer peripheral blade tip, and the rake angle is negative. Since the clearance angle does not increase excessively on the corner side and the clearance angle is not insufficient, chattering and abnormal wear of the tip of the outer peripheral blade with respect to the feed in the tool axis direction are avoided.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

As shown in FIG. 1 and FIG. 2, in the end mill of this embodiment, a tapered shaft-shaped blade portion 40 having a substantially polygonal cross section is formed at the tip of a tool body (not shown). Side 41
4 outer peripheral blades 42 are formed on the convex ridge portion of
Gash that is depressed toward the base end of the tool at the tip of the blade 40
43 is formed, and each outer peripheral blade 42 is formed on the convex ridgeline portion of the gash 43.
Bottom blades extending from the tip of the tool toward the tool rotation center P0
44 ... are formed.

Each of the outer peripheral blades 42 is formed as a so-called left-handed outer peripheral blade that is twisted counterclockwise around the tool axis O in a front view of the blade portion 40, and the twist angle α is 20 °. Further, the taper angle φ of the outer peripheral blade 42 is set to 1 ° 30 '. The twist angle α and the taper angle φ are appropriately determined according to cutting conditions and the like. Specifically, the twist angle α is in the range of 0 ° to 20 ° and the taper angle φ is in the range of 30 'to 5 °. It

On the other hand, in the above-mentioned gash 43, in the front view of the blade portion 40, each outer blade from the tool center P0 with each bottom blade 44 as a convex ridge portion.
It is formed in a groove shape that extends radially toward the side surface 41 between 42,
The rotation center P0 is provided by retracting a predetermined amount F from the tip of each outer peripheral blade 42 toward the tool base end side. The wall surface of the gash 43 is composed of a rake face 45 that is continuous from each bottom blade 44 to the front side in the tool rotation direction, and a flank face 46 that is continuous from each bottom blade 44 to the rear side in the tool rotation direction.

As shown in FIGS. 1 and 3, the rake face 45 is
The ridge line portion with the blade portion side surface 41 is formed on the inclined surface extending toward the tool base end side at a certain distance to the front side in the tool rotation direction with respect to each outer peripheral blade 42, whereby at the tip portion of the blade portion side surface 41. A rake face 47 having a predetermined width D with respect to each outer peripheral blade 42 is formed in a portion on the front side in the rotational direction of the outer peripheral blade 42. Further, the flank surface 46 with respect to the bottom blade 44 is an inclined surface that is inclined in two steps with a predetermined second clearance angle γ1 and third clearance angle γ2 with respect to the bottom blade 44, whereby the tip of the blade portion side surface 41 is formed. A flank 48 for each outer peripheral blade 42 is formed in a portion of the portion on the rear side of the outer peripheral blade 42 in the rotation direction.

Here, the rake face 47 with respect to the tip of each outer peripheral blade 42
The rake angle θ1 is set in the range of −30 ° to −50 °. This is because if the rake angle θ1 exceeds −30 ° and deviates to the regular angle side, the cutting edge angle (θ1 + θ3) at the tip of the outer peripheral blade 42.
May be insufficient to easily cause chipping,
On the other hand, if the rake angle θ1 exceeds −50 ° and deviates to the negative angle side, the cutting resistance at the tip of the outer peripheral blade 42 becomes excessively large, which may hinder smooth cutting.

The clearance angle θ2 at the tip of the outer peripheral blade 42 is
It is set in the range of 20 ° to 35 °. If the clearance angle θ2 is less than 20 °, abnormal wear may occur between the flank surface 48 and the work material, leading to early wear of the tip of the outer peripheral blade 42, while the clearance angle θ2 exceeds 35 °. And the edge angle (θ1 + θ3) at the tip of the outer peripheral blade 42 may be insufficient, which may cause adverse effects such as chipping.

Further, as shown in FIGS. 2 to 4, the outer peripheral portion of the bottom blade 44 is notched with a predetermined chamfer angle C in order to prevent chipping or the like during cutting. Furthermore, the bottom blade
The reference numeral 44 is formed so as to be inclined toward the tool base end side with a predetermined clearance angle G toward the tool rotation center P0 within a predetermined width H.

Then, the portion of the blade side surface 41 closer to the tool base end side than the tip end portion is an extension surface of each of the rake face 47 and the flank face 48, whereby an intermediate portion and a base end portion of each outer peripheral blade 42 are provided. The rake angle θ1 and the clearance angle θ2 are the same as those of the above-mentioned tip portion.

Thus, according to the end mill configured as described above, the blade portion 40 is centered on the axis O of the blade portion 40 in the direction of arrow B (first
(See Fig. And Fig. 2)
40 is sent forward in the axial direction, and along with this, the bottom blade 43
And the tip of the outer peripheral blade 42 pierces the work material, then the outer peripheral blade
The portion of the intermediate portion and the base end portion of 42 which has been previously perforated is expanded in a tapered shape. Then, after the blade portion 40 is fed out in the axial direction by a predetermined amount, the blade portion 40 is fed out in the direction orthogonal to the axial direction, whereby a tapered groove is formed in the work material.

Here, according to the end mill of the present embodiment, the rake face 47 and the flank face which are inclined at the rake angle θ1 and the clearance angle θ2 in the above-described ranges are provided at the tip portion of the blade portion side face 41 which intersects the gash 43 in particular. Due to the provision of 48, the blade edge angle (θ1
There is no adverse effect such as chatter vibration due to lack of + θ3), increase in cutting resistance, or early wear of the outer peripheral blade 42.
As a result, it is not necessary to pre-process the work material in advance, and the cutting efficiency is improved.

In addition, in the present embodiment, in particular, a portion other than the tip portion of the blade side surface 41 is also an inclined surface that is inclined at the same rake angles θ1 and θ2 as the tip portion, but the end mill of the present invention is not limited to this. Instead, like the conventional end mill having a polygonal shape, it may be formed in a planar shape that linearly connects the outer peripheral blades 42. In short, as long as the rake angle θ1 and the clearance angle θ2 are given at the tip of the blade portion 40, the shape of the other portions is not limited.

Further, in the present embodiment, the outer peripheral blade 42 is a left-handed helical blade, but the present invention is not limited to this, and can be appropriately changed such as straight blade and right-handed blade, and the number of the outer peripheral blade 42 and the bottom blade 44 is limited to four. Not a thing.

[Examples] Next, in order to clarify the effect of the present invention, the following cutting test was performed using the end mill according to the present invention and the conventional end mill, respectively.

(Cutting test) Using an end mill according to the present invention and a conventional end mill, a taper groove is finished as shown in FIG.
The cutting conditions at this time were compared. The processing conditions are as shown below, and the results are shown in Table 1.

・ Work material: HPM-1 ・ Groove shape: Depth (L): 14mm: Tip width (W): 1mm: Taper angle (θ): 1 ° 30 '・ Cutting speed: 50m / min. ・ Tool feed rate : 400mm / rev. As is clear from Table 1, when machining a tapered groove with an end mill with a bottom blade, when the number of blades is large in the conventional end mill, the rake angle of the tip of the outer peripheral blade is too biased to the negative angle side and the cutting resistance is increased. Is excessively increased, and the feed amount in the tool axis direction cannot be increased. On the other hand, in the end mill according to the present invention, the rake angle and the clearance angle of the outer peripheral blade tip are set within a certain range regardless of the number of blades, so that chatter vibration and abnormal wear of the outer peripheral blade are avoided while avoiding the tool axial direction. It became clear that the depth of cut can be increased more than twice that of the conventional one.

In the above cutting test, it was also confirmed that the machining time was shortened to about 1/10 of the case where the same machining was performed by electric discharge machining.

[Effects of the Invention] As described above, according to the present invention, since the rake angle and the clearance angle of the outer peripheral blade tip portion are set in the proper range and the blade edge strength is sufficiently secured, the tool is fed in the axial direction. Even when cutting is performed by cutting, chatter vibration is prevented and premature wear of the tip of the outer peripheral blade is avoided, and as a result, especially when machining the taper groove, the under-machining is not required and the cutting efficiency is significantly improved.

[Brief description of drawings]

1 to 4 are views showing an embodiment of the present invention. FIG. 1 is a side view thereof, FIG. 2 is a front view, FIG. 3 is an enlarged front view of the tip of an outer peripheral blade, and FIG. An enlarged side view of the tip of the outer peripheral blade, FIG. 5 is a diagram showing a working form of a cutting test, FIG. 6 is a diagram showing a groove shape of a work material, and FIGS. 7 and 8 are examples of conventional end mills. FIG. 7 is a side view and FIG. 8 is a seventh view.
It is sectional drawing in the II-II line of a figure. 40 …… Blade part, 40a …… Side surface, 47 …… Scoop surface, 48 …… Relief surface, 42 …… Outer peripheral blade, 43 …… Gash, 44 …… Bottom blade,
P0: Tool rotation center, O: Tool axis.

Claims (1)

[Claims] 1. A blade portion (40) having a substantially polygonal cross section orthogonal to an axis (O) of the tool body is formed at a tip portion of the tool body, and each side surface (40a) of the blade portion (40). The outer peripheral blade (42) is formed on the ridge line where the) intersects, and extends from the front end of the outer peripheral blade (42) toward the tool center (P0) at the front end surface of the blade portion (40). A bottom blade (44) is formed, and a gash (43) is formed on the tool tip surface between the bottom blades (44) so as to be depressed toward the tool base end side and open to the side surface of the blade tip end portion. In the end mill consisting of, the side surface of the blade part (40
Of the a), the rake angle (θ in front view of the blade part of the side face (47) connected to the front side in the tool rotation direction from each outer peripheral blade (42)
1) is within the range of -30 ° to -50 °, and the clearance angle (θ2) of the side face (48) connected to the rear side in the tool rotation direction from each outer peripheral blade (42) is 20 ° to 35 ° in front view of the blade. An end mill characterized by being set in a range.