Cutting insert having an improved chip breaker

Details Cutting insert having an improved chip breaker Cutting insert having an improved chip breaker

2000-03-20

2001-04-17

Tsai, Henry (Department: 3722)

Cutters, for shaping

Including tool having plural alternatively usable cutting edges

With integral chip breaker, guide or deflector

C407S116000, C407S115000

Reexamination Certificate

active

06217264

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cutting insert, and more particularly to a cutting insert capable of enhancing the surface finish of worked materials and lengthening the durability of a cutting tool which has utilized in conjunction with the cutting insert, capable of efficiently removing cut chips from the cutting region by making a chip breaker into a complete non uniform curved surface to flow the cut chips in the most natural direction and curling, which are formed when performing a desired cutting operation, to also minimize the resistance to chip flow and the occurrence of the adhesion phenomenon.
2. Description of the Related Art
The machine industry such as the automotive industry etc. has been well developed heretofore, and thereby a variety of manufacturing processes have been automatized and performed at high speed. As a result, there exists a need for enhancing the performance of the cutting tool and for lengthening the durability of the cutting tool which has been well utilized in the machine industry.
The cutting tool is mainly used to cut ferrous or nonferrous metals under the state that it is mounted in a machine tool. The processes of cutting the metals using the cutting tool can be classified into two ways. According to the first way, the cutting tool cuts a metal workpiece under the state that an edge of cutting tool is brought into contact with a surface of the metal workpiece when rotating the workpiece, According to the second way, a cutting insert having a cutting edge cuts a metal workpiece, which is fixed at a predetermined position on a work station, when rotating the cutting insert under the state that the cutting insert is mounted in a machine tool using a holder for cutting tool.
The cutting insert is used to cut the workpiece under the state that it is mounted to a portion of the cutting tool directly contacting with the workpiece. The cutting insert is the most important factor in a metal cutting process. Further, the quality and the shape of the cutting insert is the most important factor for determining the durability of the cutting tool and the quality of the worked materials.
However, in the metal cutting process using the cutting insert, it is the most important things that metal chips generated from the workpiece, in the form of chip, when cutting unessential portions of the workpiece are securely and effectively flowed from the cutting region. Accordingly, a variety of endeavors for developing a cutting insert capable of securely flowing the metal chips from the cutting region without interfering with the continuing cutting process and without endangering the operating personnel have been proposed.
As a part of the endeavors, a method of changing the shape of the cutting insert for effectively cutting the workpiece has been proposed. Generally, the cutting insert has a rake surface and a flank surface. The rake surface allows the cut chips for flowing. An angle and a shape of the rake surface play an important role in determining the durability of the cutting insert, the surface finish of worked materials, a chip breaking, cut chip flowing and a cutting resistance, etc. The specific shape of the sloping surface and the surplus surface is called as “chip breaker”. Chip breakers having a variety of shapes have been developed heretofore in the field of the art with respect to manufacturing the cutting insert. A standard of developing the chip breaker in relation to the shape thereof is the quality of the workpiece, the shape of the workpiece, a size of the cut portion of the workpiece, a precision of the cutting process, the quality of the cutting tool, etc.
However, according to the prior art, since a predetermined angle is present between a rake surface and a certain plane, a unnatural cutting phenomenon, which is not associated with a natural cutting mechanism proceed in the metal cutting process, can be generated. Due to this phenomenon, the cutting resistance is increased when cutting the workpiece. Further, the workpiece can be melted and stuck to the cutting edge of the cutting tool at the time that the workpiece begins to be melt. In addition, there are many problems such that the badness of the chip breaking, the excess wear of the cutting tool, the chipping of the cutting edge, the breakdown of the cutting tool, etc.
FIG. 11A
is a top view of a cutting insert according to the prior art, and
FIG. 11B
is a sectional view taken along the line XI—XI of FIG.
11
A.
Referring to
FIGS. 11A and 11B
, a cutting insert
10
according to the prior art includes a main body
12
having substantially parallel an upper surface
11
and a bottom surface
13
. A circle opening
18
is formed through the center of the main body
12
. Circle opening
18
provides a means whereby a holder for cutting tool (not shown) can be fitted into circle opening
18
to secure cutting insert
10
to the holder for cutting tool.
Cutting insert
10
includes four cutting corners
15
. Two cutting edges
16
and two chip grooves
17
adjacent to the cutting edges
16
extend from cutting corners
15
. Cutting edges
16
extend from cutting corners
15
to the middle portion of cutting edges
16
at a predetermined angle. Cutting edges
16
comprise a straight sloping portion
16
a
and a horizontal center portion
16
b
, respectively.
Straight sloping portions
16
a
of cutting edges
16
vary in width, widening from cutting corners
15
to the middle portion of cutting edges
16
.
Chip grooves
17
continuously extend across sections of cutting corners
15
and sections adjacent to straight sloping portions
16
a
. Chip grooves
17
are provided with sloping side surfaces
17
a
,
17
b
. Sloping side surfaces
17
a
,
17
b
uniformly maintain in width at the center portions
16
b
of cutting edges
16
. Sloping side surfaces
17
a
,
17
b
and upper surface
11
of cutting insert
10
form an angle greater than 130°.
Upper surface
11
includes a flat horizontal section
11
a
and flat triangular sections
11
b
. Flat triangular sections
11
b
form a predetermined angle with flat horizontal section
11
a
. Flat horizontal section
11
a
meets with sloping side surfaces
17
a
,
17
b
of chip grooves
17
in an adjoining relationship and accordingly form an angle therebetween. The altitude of flat horizontal section
11
a
is lower than that of cutting edge
16
.
However, in cutting insert
10
as described above, sloping side surfaces
17
a
,
17
b
of the chip breaker allowing the cut chips to flow there through are plane in figure. Further, the common junctures between flat horizontal section
11
a
and flat triangular sections
11
b
, sloping side surface
17
a
and flat triangular section
11
b
, sloping side surface
17
b
and flat horizontal section
11
a
, etc. form an angle therebetween. Accordingly, the cut scraps produced during the metal cutting process undergo compulsive bending stresses while passing through the planes such as sloping side surfaces
17
a
,
17
b
and the common junctures. As a result, the irregular and excess stresses can be applied to cutting edge
16
playing an important role in the cutting process, and thereby the cut chips are melted and stuck to cutting edge
16
. Further, the cut chips cannot smoothly and securely flowed from the cutting region, and the surface finish of worked materials is not good. In addition, the chipping of the cutting edge can be generated. Consequently, the cutting tool has a short life.
U.S. Pat. No. 5,772,366 issued to Jorgen Wiman et al on Jun. 30, 1998 discloses a cutting insert having an integral chip control surface. In this patent, the cutting insert comprises a compound body consisting of a sintered cemented carbide substrate with a surface coating which is a diamond coating with a thickness of 1~20 &mgr;m deposited directly from a gas phase in a reactor by CVD or PVD technique. Therefore, it is necessary to perform any post-processing for a plurality of curved projections and an integral chipformer provided on an upper surface of the cutting

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