CN113441773A

CN113441773A - End mill and insert therefor

Info

Publication number: CN113441773A
Application number: CN202010228644.1A
Authority: CN
Inventors: 刘东亨
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2020-03-27
Filing date: 2020-03-27
Publication date: 2021-09-28
Also published as: WO2021190418A1

Abstract

The invention provides an end mill and a blade thereof. The blade extends from the rear end to the front end along the rotating shaft and comprises an end face, a front corner face and a cutting edge; the end face is positioned at the front end side of the blade and is provided with a rear corner face; the front corner surface is correspondingly positioned in front of the rotation direction of the rear corner surface; the cutting edge is positioned between the rear corner face and the front corner face and is provided with a passivation face; the cutting edge extends from a center side of the rotating shaft to an outer peripheral side of the insert as being distant from the tip end side; the passivation surface has a first portion and a second portion located on the outer peripheral side of the first portion; the width of the second part is larger than that of the first part. The invention can improve the cutting ability of the blade at the center side and improve the surface processing quality of the workpiece.

Description

End mill and insert therefor

Technical Field

The invention relates to a workpiece machining tool, in particular to an end mill and a blade thereof.

Background

Chinese patent application CN109862983A discloses a ball end mill, in which a cutting insert has an arc-shaped cutting edge projecting toward the outer peripheral side of the tip of the cutting insert, and a rounded portion is formed in the tip of the arc-shaped cutting edge in a range in which the radiation angle is at least 30 ° or less. Thus, when a high-hardness workpiece is efficiently machined, the cutting edge strength near the tip of the arc-shaped cutting edge can be sufficiently ensured, and the chipping of the cutting edge can be prevented.

For the finish machining with high requirements on the surface quality of a workpiece or the machining occasions with small cutting depth and feeding, the rounding on the cutting edge is easy to produce the motion of applying extrusion to the workpiece, the cutting property is poor, the cutting resistance is large, the cutter is easy to slip, the surface of the workpiece has scraping and sliding traces, and the surface quality of the workpiece is influenced.

Disclosure of Invention

It is an object of the present invention to provide an insert for an end mill to improve the surface quality of a machined workpiece.

Another object of the present invention is to provide an end mill having the above-described insert.

In order to solve the technical problem, the invention adopts the following technical scheme:

according to one aspect of the present invention, there is provided an insert for an end mill, which extends from a rear end to a front end along a rotation axis, comprising an end face, a front corner face and a cutting edge; the end face is positioned at the front end side of the blade and is provided with a rear corner face; the front corner surface is correspondingly positioned in front of the rotation direction of the rear corner surface; the cutting edge is positioned between the rear corner face and the front corner face and is provided with a passivation face; the cutting edge extends from a center side of the rotating shaft to an outer peripheral side of the insert as being distant from the tip end side; the passivation surface has a first portion and a second portion located on the outer peripheral side of the first portion; the width of the second part is larger than that of the first part.

According to another aspect of the invention there is provided an end mill comprising a shank extending forwardly and rearwardly along a rotational axis and a blade as described above at a forward end of the shank, the blade being detachably mounted to the shank or the blade being of unitary construction with the shank.

According to the technical scheme, the invention has at least the following advantages and positive effects: in the blade of the end mill provided by the invention, the cutting edge is provided with the blunted surface, and the first part of the blunted surface, which is closer to the center side, has smaller width, so that the part of the cutting edge, which is closer to the center side, is sharper, has better cutting performance, has lower cutting resistance during processing, and is beneficial to the part of the cutting edge, which is closer to the center side and has smaller cutting speed, to cut more stably and smoothly, thereby improving the surface quality of a workpiece. And the second part closer to the outer peripheral side has larger width, so that the strength of the part of the cutting edge closer to the outer peripheral side is better, the working state of relatively larger cutting amount and cutting speed is more favorably kept, and the service life of the blade is prolonged.

Drawings

FIG. 1 is a perspective view of an end mill according to an embodiment of the present invention.

Fig. 2 is a perspective view of an insert of the end mill of fig. 1.

Fig. 3 is a front view of fig. 2.

Fig. 4 is a front end view of fig. 2.

Fig. 5 to 8 are cross-sectional views orthogonal to the cutting edge at D-D in fig. 3, and fig. 5 to 8 illustrate several different configurations of the blunted surface, respectively.

Fig. 9 is a schematic diagram of a selected feature location on the view of fig. 3.

Fig. 10 is a cross-sectional view taken normal to the cutting edge at E-E in fig. 9.

Fig. 11 is a cross-sectional view taken normal to the cutting edge at F-F in fig. 9.

Fig. 12 is a cross-sectional view taken normal to the cutting edge at G-G in fig. 9.

Fig. 13 is a schematic view of the machining process of the end mill of the present invention.

Fig. 14 is a schematic view showing a state in which the insert of fig. 13 is cutting a workpiece.

Fig. 15-17 are front views of blade shapes of other embodiments of the present invention.

The reference numerals are explained below: 10. an end mill; 1/1a/1b/1c, blade; 2. a knife handle; 21. a knife jaw; 3. fastening screws; 11. an end face; 111. a rear corner face; 1111. a main rear corner face; 1112. a minor back corner face; 12. a front corner face; 13/13a/13b/13c, cutting edge; 40. and (5) a workpiece.

Detailed Description

Exemplary embodiments that embody features and advantages of the invention are described in detail below in the specification. It is to be understood that the invention is capable of other embodiments and that various changes in form and details may be made therein without departing from the scope of the invention and the description and drawings are to be regarded as illustrative in nature and not as restrictive.

The invention provides an end mill and a blade thereof, wherein the end mill can be a ball end mill, an arc end mill and the like. The insert of the end mill is positioned on the tip side of the end mill, and has a plurality of cutting edges in a planar curve or a spatial curve. When the end mill is used, the end mill rotates around the rotating shaft, each cutting edge performs cutting processing on a workpiece, and a spherical surface or a space curved surface is processed on the workpiece.

Fig. 1 illustrates the structure of an end mill 10 according to an embodiment of the present invention. The end mill 10 includes a shank 2 and an insert 1 located at a forward end of the shank 2. In this embodiment, the end mill 10 is a ball nose end mill.

The shank 2 extends from the rear end to the front end along the rotation axis L, and the front end of the shank 2 is provided with two spaced jaws 21. The insert 1 is mounted between the two jaws 21 and is fixed by a fastening screw 3 penetrating the jaws 21 and the insert 1.

In this configuration, the blade 1 is removably mounted to the handle 2. In other embodiments, the blade 1 may be integral with the handle 2.

The present invention is optimized with respect to the structure of the cutting edge of the blade 1, and is described in detail below with reference to the structure of the detachable blade 1. The same applies to the blade 1 which is formed integrally with the shank 2, as regards the cutting edge.

Fig. 2 illustrates a perspective view of the blade 1 of the present embodiment, fig. 3 illustrates a front view of the blade 1, and fig. 4 illustrates a tip end view of the blade 1.

The insert 1 extends from a rear end to a front end along the rotation axis L, and has an end surface 11 located on the front end side of the insert 1 and having a rear corner surface 111, a front corner surface 12 located at a position corresponding to the front in the rotation direction of the rear corner surface 111, and a cutting edge 13 located between the rear corner surface 111 and the front corner surface 12 and having a blunt surface.

In order to facilitate the installation of the blade 1 and the handle 2, the blade 1 of the present embodiment further has two opposite restraining surfaces 14 and a through hole 15 penetrating the two restraining surfaces 14, the two restraining surfaces 14 are respectively attached to the two jaws 21, and the through hole 15 is used for connecting and matching with the fastening screw 3.

The end surface 11 is located between the two restraining surfaces 14. The relief surface 111 of the end surface 11 is located rearward in the rotational direction of the cutting edge 13 and is connected between the cutting edge 13 and the restraint surface 14. Specifically, the relief surface 111 includes a primary relief surface 1111 and a secondary relief surface 1112, the primary relief surface 1111 contacts the cutting edge 13, and the secondary relief surface 1112 contacts the restraint surface 14.

The rake face 12 is located forward in the rotational direction of the cutting edge 13, and a chip discharge groove (not shown) for discharging chips generated when the cutting edge 13 cuts the workpiece is formed between the rake face and the restraining face 14.

The cutting edge 13 extends from the center side of the rotation axis L to the outer peripheral side of the insert 1 as being distant from the tip side of the insert 1. In the present embodiment, the cutting edge 13 has a spatial arc shape. The cutting edges 13 are provided in two pieces that are centrosymmetric with respect to the rotation axis L. The projections of the two cutting edges 13 are located on the same circle in front view. The profile of the cutting edge 13 is configured to be spherical when the insert 1 is rotated about the axis of rotation L to machine a spherical surface on a workpiece.

The cutting edges 13 may form a blunt surface according to relevant blunting measures in the art, the blunt surface extending from the central side to the peripheral side as well as the direction of extension of the cutting edges 13. Referring to fig. 5 to 8, the passivation surface may be planar or convex according to different passivation methods. The blunt surface of the cutting edge 13 is connected to the rake surface 12 and the main relief surface 1111, respectively.

As shown in fig. 5, the passivation surface of the cutting edge 13 is a circular arc surface, and is tangent to the rake angle surface 12 and the main relief angle surface 1111, and may be formed by rounding, and the radius R of the circular arc of the entire passivation surface is kept consistent.

As shown in fig. 6, the blunt surface of the cutting edge 13 is a plane, which may be called a chamfer angle, and the blunt surface has an included angle with the front corner surface 12 and the main rear corner surface 1111, which may be the same or different.

As shown in fig. 7, the blunt surface of the cutting edge 13 is two smoothly connected arc surfaces, the radius of the arc surface connected to the rake surface 12 is R1, the radius of the arc surface connected to the main relief surface 1111 is R2, and R1 > R2.

As shown in fig. 8, the blunt surface of the cutting edge 13 is also a two-stage arc surface in smooth contact, the radius of the arc surface in contact with the rake surface 12 is R3, the radius of the arc surface in contact with the main relief surface 1111 is R4, and R3 < R4.

In practical applications, the specific shape of the passivation surface is not limited to the four listed above, and can be set according to the needs, which is not illustrated.

In some embodiments, not shown, the surface of the insert 1 may be coated with a coating, in which case the passive surface is correspondingly formed on the coating. The coating of the coating can be carried out by physical vapor deposition or chemical vapor deposition, and the specific manner can be referred to the related art. The thickness of the coating can be set as desired, and the thickness and shape of the coating can be different at different positions of the cutting edge 13, so that different sizes of blunted surfaces can be formed at the coating at different positions. The strength of the blade 1 can be increased through the coating mode, the reduction of the size of a blunted surface is facilitated on the basis of ensuring the strength of the blade 1, and therefore the cutting performance of the cutting edge 13 is improved.

Regardless of the form of the passivation means, according to the embodiment of the present invention, the passivation surface has a first portion and a second portion located on the outer peripheral side of the first portion with respect to the extending direction of the cutting edge 13, and the width of the second portion is larger than the width of the first portion.

It will be appreciated that the first and second locations do not represent fixed positions in the direction of extension of the cutting edge 13 and may be selected dynamically. Based on the relationship between the widths of the first and second portions, it is inferred that the blunt surface width at the position closer to the center side is smaller than the blunt surface width at the position closer to the outer peripheral side in the cutting edge 13.

In other words, the cutting edges 13 near the center side position are sharper, while the cutting edges 13 near the outer peripheral side position are duller. Therefore, the portion of the cutting edge 13 closer to the center side can cut into the workpiece more conveniently, has better cutting performance, has lower cutting resistance during processing, and is beneficial to the portion of the cutting edge 13 closer to the center side with lower cutting speed to cut more smoothly and stably, thereby improving the surface quality of the workpiece. And the second part closer to the outer periphery side has a larger width, so that the strength of the part of the cutting edge 13 closer to the outer periphery side is better, the working state of relatively larger cutting amount and cutting speed is more favorably kept, and the service life of the blade 1 is prolonged.

The width of the blunt surface at a certain position of the cutting edge 13 is a distance between two points at which the cutting edge 13 is in contact with the rake surface 12 and the relief surface 111, respectively.

In the cross-sections orthogonal to the cutting edge 13 shown in fig. 5 to 8, the width of the blunt surface can be represented as a in a front view (the view direction shown in fig. 3). In addition, the width may be represented as B if viewed from a front end view (the direction of view shown in fig. 4). Viewed from the perspective view (the direction of view shown in fig. 2), it can be denoted as S.

The cross section orthogonal to the cutting edge 13 is: at a point of the cutting edge 13, an orthogonal plane is perpendicular to a tangent line of the cutting edge 13 passing through the point.

The width of the blunt surface is evaluated by the above-mentioned a, B or S, and the relationship between the width of the first portion and the width of the second portion is established as the cutting edge 13 extends.

Preferably, the width of the passivation surface gradually increases from the first portion to the second portion. This makes the cutting speed of the cutting edge 13 gradually increase from the first portion to the second portion, thereby making the cutting performance more uniform across the cutting edge 13.

In some embodiments, the cutting edge 13 has a blunt surface over the entire edge length extending from the center side to the outer peripheral side, improving the chipping resistance of the entire cutting edge 13. Further, the width of the blunted surface gradually increases from the end portion on the center side toward the end portion on the outer peripheral side.

The passivation surface has a minimum width at a central end, a maximum width at an outer peripheral end, and the maximum width is (1.5-5) × the minimum width. Thus, a better balance between cutting ability and strength can be obtained.

In some embodiments, it is also possible to form the blunt surface only at a part of the extension of the cutting edge 13, for example only at a part of the cutting edge 13 near the center side, or at a part of the cutting edge 13 in the middle area where the cutting edge 13 is often used, etc.

In addition, in some embodiments, the passivation surface may further have a third portion located closer to the center side than the first portion, and the width of the third portion may be the same as the width of the first portion.

The passivation surface may have a fourth portion located on the outer peripheral side of the second portion, and the width of the second portion may be the same as the width of the fourth portion.

That is, there may be a partial region of constant blunt surface size on the cutting edge 13, and there may be a plurality of such partial regions of constant blunt surface size. In extension, regions of increasing width of the blunt surface and regions of constant width of the blunt surface may alternately be present on the cutting edge 13 over the entire extension of the cutting edge 13.

Referring to fig. 9, in one embodiment, the blunt surface is a circular arc surface, and E, F, G points are sequentially taken in a direction from the center side to the outer peripheral side in the extending direction of the cutting edge 13, where the radiation angle of the cutting edge 13 at E is 20 °, the radiation angle of the cutting edge 13 at F is 50 °, and the radiation angle of the cutting edge 13 at G is 75 °.

The radiation angle means: and taking a point C on the rotating shaft L, wherein the distance from the front end of the point C to the cutting edge 13 is the maximum processing radius, taking a projection straight line of a connecting line of the point C and any point on the cutting edge 13 on a reference plane, and taking the included angle between the projection straight line and the rotating shaft L as a radiation angle.

For the ball nose end mill illustrated in this embodiment, point C is exactly at the center of the through hole 15 in the view of fig. 9, and the reference plane is the restraining plane 14 of the insert 1.

The radius of the blunt surface is R in order from the three positions shown in fig. 10 to 12, respectively, as viewed in a cross section perpendicular to the cutting edge 13_E、R_F、R_GThe relationship between the radius of the passivation surface is: r_E＜R_F＜R_G. For example, R_EMay be 0.02mm, R_FIs 0.025mm, R_GIs 0.03 mm. Accordingly, the radius of the blunted surface at the end portion on the center side is preferably 0.005mm to 0.015 mm. The radius of the blunt surface of the cutting edge 13 in the entire extending direction is preferably in the range of 0.005mm to 0.05mm in order to balance the cutting ability and the strength.

For the passivated surfaces adopting other passivation means, the width numerical range of the passivated surface can be reasonably adjusted according to the radius range of the arc surface.

Fig. 13 illustrates a state of a machining process of the end mill 10. The end mill 10 is fed in the horizontal direction, the single-edge feed is Fz, W1 indicates the position of the first cutting edge 13 of the insert 1 of the end mill 10 at the time of cutting, and W2 indicates the position of the next cutting edge 13 of the insert 1 at the time of cutting.

The thickness of the workpiece 40 actually cut by the cutting edge 13 at a certain position is H, and as can be seen from fig. 13, the relationship between H and Fz depends on the feed angle, i.e., the angle between the tangent line of the cutting edge 13 at the point where the cutting edge 13 contacts the workpiece 40 and the horizontal plane, which is also equal to the radial angle of the cutting edge 13 at that position. From the trigonometric function, H ═ Fz × sin θ.

Fig. 14 shows a cross-sectional structure of the end mill 10 when the cutting edge 13 of the insert 1 is in contact with the workpiece 40. During cutting, the cutting edge 13 and the rake face 12 jointly act on the workpiece 40 to cut the workpiece 40, and the cutting thickness is indicated by H in fig. 13. The width of the blunt surface of the cutting edge 13 in contact with the workpiece 40 is a (see the schematic diagrams of fig. 5 to 8).

The following relationship table is provided for different feed angles θ, different feeds Fz, and different blunting surface widths a.

The cutting resistance in the range of the blunt surface width a is determined by the structure of the blunt surface in view of the shape of the insert 1 contacting the workpiece 40, and in this range, the blunt surface of the cutting edge 13 functions as a very small rake angle (a negative rake angle having a large absolute value), the cutting resistance is large, and the cutting edge 13 has poor cutting performance. The rake face 12 contacts the workpiece 40 beyond the blunted face, and the cutting resistance is determined by the rake face 12, which has a relatively large rake angle, relatively small cutting resistance, and relatively better cutting performance.

Taken together, the smaller the A/H value, the better the cutting performance and the lower the cutting resistance. The larger the A/H is, the larger the influence of the blunted surface portion is, the worse the cutting property of the cutting edge 13 is, the larger the cutting resistance is, and the scratch is liable to occur on the surface of the workpiece 40, which affects the surface quality of the workpiece.

From the data of the above table, in comparison with two positions where the feed angle θ is 20 ° and the feed angle θ is 47 ° under the condition of the same single-edge feed Fz and the same dull surface width a, a/H is larger at a position where θ is 20 ° relatively closer to the center side, indicating that the cutting edge 13 closer to the center side is worse in the cutting property. On the other hand, the same dull surface width a and the same feed angle θ are provided at the same position of the cutting edge 13, and the smaller the single-edge feed Fz is, the larger a/H is, which means that the lower the single-edge feed is, the worse the cutting performance is, and the larger the influence of the dull surface is. In the processing conditions of a smaller feed angle and a smaller feed, a reduction in the width of the blunted surface of the cutting edge 13 is of greater significance for improving the cutting performance.

By combining the scheme of the invention, the passivated surface has relatively smaller width for the first part close to the central side, so that the A/H value can be reduced, the cutting ability of the central side part is effectively improved, the surface processing quality of a workpiece is improved, and the method is particularly suitable for the situations of small cutting feed angle and low feed.

On the other hand, in the second portion close to the outer peripheral side, the cutting speed and the cutting amount of the cutting edge 13 are relatively large, and at this time, the cutting resistance is mainly determined by the rake face 12, and the strength of the cutting edge 13 can be increased instead of being greatly affected by appropriately increasing the width of the blunt face, in accordance with the requirements of the operating conditions of the cutting edge 13.

Referring to fig. 15-17, in other embodiments, the end mill of the present invention may also be a radius end mill, with the cutting edges of the inserts being in the shape of planar curves.

Fig. 15 shows an insert 1a of a radius type end mill, and a corner of the insert 1a is provided with a cutting edge 13a having a radius shape. In the end mill insert 1b shown in fig. 16, the cutting edge 13b includes a circular arc section near the center side and a straight line section extending rearward from the rear end of the circular arc section to the outer peripheral side. In the end mill insert 1c shown in fig. 17, the cutting edge 13c includes a plurality of arcs having different radii and being smoothly connected to each other.

In the insert of each end mill described above, the cutting edges have different extending shapes, and are not limited to the several shapes exemplified here, but in general, the cutting edges extend from the center side to the outer peripheral side in a direction away from the tip. In these cutting edges, it is also possible to improve the cutting ability on the center side of the cutting edge by providing a blunt surface in a manner referred to the ball nose end mill insert and by setting the width of the blunt surface according to the above-described change law, thereby improving the surface processing quality of the workpiece. And will not be described in detail herein.

While the present invention has been described with reference to several exemplary embodiments, it is understood that the terminology used is intended to be in the nature of words of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

Claims

1. An insert for an end mill extending along a rotational axis from a rear end to a front end, comprising:

an end face located on a leading end side of the blade and having a trailing corner face;

a front corner surface located in front of the rotation direction of the rear corner surface; and

a cutting edge between said back corner face and said front corner face and having a blunt surface;

the cutting edge extends from a center side of the rotating shaft to an outer peripheral side of the insert as being distant from the tip end side;

the passivation surface has a first portion and a second portion located on the outer peripheral side of the first portion;

the width of the second part is larger than that of the first part.

2. The insert according to claim 1, wherein the width of the blunt surface increases from the first location to the second location.

3. The insert according to claim 2, wherein the width of the blunt surface gradually increases from the end on the center side to the end on the outer peripheral side.

4. The insert according to claim 3, wherein the blunt surface has a minimum width at an end on the center side, and a maximum width at an end on the outer peripheral side, the maximum width being (1.5 to 5) x the minimum width.

5. The insert according to claim 1, wherein the blunt surface further has a third portion located closer to the center side than the first portion, and the third portion has the same width as the first portion.

6. The insert according to claim 1, wherein the blunt surface further has a fourth portion located closer to the outer peripheral side than the second portion, and the width of the second portion is the same as the width of the fourth portion.

7. The blade of claim 1 wherein the blunt surface is planar or convexly curved.

8. The insert according to claim 1, wherein the surface of the insert has a coating on which the blunted surface is formed.

9. The blade of claim 1 wherein said cutting edge is planar or spatially curved.

10. An end mill comprising a shank extending forwardly and rearwardly along an axis of rotation and a blade as claimed in any one of claims 1 to 9 at a forward end of the shank, the blade being removably mounted to the shank or the blade being of unitary construction with the shank.