WO1994027768A1

WO1994027768A1 - Cutting insert

Info

Publication number: WO1994027768A1
Application number: PCT/DE1994/000564
Authority: WO
Inventors: José AGUSTIN PAYA; Dirk Retzkowski; Klaus Mader
Original assignee: Widia Gmbh
Priority date: 1993-05-27
Filing date: 1994-05-11
Publication date: 1994-12-08
Also published as: DE4416651A1

Abstract

The invention concerns a cutting insert designed for machining, in particular turning, milling, engraving and drilling, the top surface of the insert on at least one side forming the cleavage plane and the surfaces surrounding it forming the flanks. In order to improve the cutting efficiency, the flank (29) is designed so that it extends in a curve at right angles to the cutting edge (26).

Description

description

Cutting insert

The invention relates to a cutting insert for chip-forming processing, in particular for turning, milling, piercing and drilling, the at least one-sided top surface of which forms the rake face and the peripheral side surfaces of which form the free surfaces.

Cutting inserts of this type usually have a flat free area at a clearance angle between 0 ^C to 30 °.

EP 0 457 488 A1 describes a cutting insert for a drill with four cutting corners, which has two open areas lying on opposite sides of the cutting insert, each with a projection adjoining the cutting corner, a falling flank and a part set back relative to the projection. This recessed part consists of a first area adjoining the cutting edge at a first positive angle of 7 ° to 20 °, a second area adjoining the lower bottom edge and which is inclined at a second positive but significantly smaller angle and a third area connecting the areas mentioned. The second, lower area is large and serves as an abutment on the side wall of the tool support of the drill. With this design a more secure support should be given in small ^¬ rem relief angle.

When drilling with cutting inserts, the cutting inserts are arranged at an angle to the longitudinal axis of the borehole, i.e. tilted slightly, in order to achieve greater drill stabilization and to prevent vibrations.

To stabilize the cutting edge, the arrangement of a negative phase on the rake face or the minimization of the free angle has been proposed. In DE 38 39 804 Al a serköpfe particular for Schlichtmes ^¬ certain indexable insert is illustrated and beschrie ^¬ ben, chen with the particularly smooth groove and groove-free Oberflä ^¬ are to be achieved during the milling. This Wendeschneidplat ^¬ te has curved cutting edge having a substantially size ^¬ ren radius than the cutting edge length with correspondingly gewölb¬ th cutting surfaces and flat contact surfaces whose contour is parabolic or hyperbelähnlich.

It is therefore an object of the invention to optimize the geometry of the cutting insert mentioned at the outset so that its cutting effect is improved. In particular, its cutting behavior should be calmed down by better guidance and a further reduction in vibration. The cutting insert should preferably be able to be produced by powder metallurgy by sintering and / or hot isostatic pressing without post-processing.

This object is achieved by a cutting insert according to claim 1, which according to the invention has a free surface which is curved as seen in a cutting edge normal. For the purposes of the present invention, the term free surface is not only to be interpreted as meaning the surface which faces the cutting surfaces on the tool, but that - with the exception of a wear zone which is caused by wear and tear and which forms after a long cutting operation - everyone on a normal to the cutting edge point lying in the open area has a (positive) distance from the workpiece with increasing distance from the cutting edge, which distance increases essentially with increasing distance from the cutting edge.

According to one embodiment of the invention, the cutting insert is provided with a spherical free surface, which is preferably convex and / or concave, the curvature of the free surface being essentially circular, parabolic, elliptical or descriptive of a first or second order curve can. This creates more space in the support area with advantages in so-called internal machining. A kon ^¬ kave open area will be preferable when cutting aluminum as a material for cutting optimization example. However, it is also possible for a convex free-space section to be connected to the cutting edge and for this to be followed by a concave free-space piece for the edge delimiting the base surface.

According to a further embodiment of the invention, the free ^¬ is surface in a plurality of regions divided, namely a first adjoining flank surface region, when viewed over its height is planar and forms a first positive free angle and a subsequent thereto the second region at a second positive clearance angle, which connects to this. This positive clearance angle is between 5 ° and 30 °, preferably it is 2 ° to 5 ° smaller than the first clearance angle. Said height of said first free surface area is 0.05 mm to 1 mm, before ^¬ preferably 0.05 mm to 2 mm. In the context of the invention also such embodiments are included in which several successive auf¬ free surface areas different Ausge¬ staltungen such as planar, curved portions having identical or different radii union under ^¬ own.

Exemplary embodiments of the invention are shown in the drawings. Show it

1 shows a first cutting insert according to the invention with four cutting edges and its variants,

2 is a partial edge side view of the open area,

3 a lancing tool with a spherical free surface,

3a shows a side view of the tool according to FIG. 3 when piercing a shaft, FIGS. 4 to 11 are side views showing different ^¬ free surface shapes,

Figure 12 view. A rhombic cutting insert in a top ^¬,

12a shows a section along line A - A of FIG. 12,

12b shows a section along line B - B of FIG. 12,

12c shows a section along line C - C of FIG. 12,

13a to c each cut side views of different open space shapes,

The cutting inserts that come into consideration in the sense of the present invention can have different shapes when viewed from the top, such as, in particular, rectangular-square 20, rhombic 21, triangular 22, round 23 or hexagonal 24. Likewise, designs as piercing tools 25 (see Fig. 3) possible. Each of the cutting inserts mentioned has at least one cutting edge 26, which can be designed either as a straight line 261, as a convex curve 262 or concave curve 263 or in wave form 264. The cutting edge is laterally delimited by cutting corners 27 and is also the boundary line between the rake face 28 and the free face 29, which in the sense of the invention is curved in a direction perpendicular to the cutting edge. The cutting inserts 20 to 25 can have chip form elements in the form of grooves or raised chip form elements 30 on their rake face. The rake face can be lowered towards its center or can be designed as a raised central part 31. According to FIG. 1, the raised central part 31 is mirror-symmetrical to a rake diagonal longitudinal ribs 30 which point in the direction of the cutting edge 26. The formation of these longitudinal ribs and wedges 30 is the subject of DE-P 41 36 417.1, to which reference is made here. The sectional view of FIG. 2 shows an angled Freiflä ^¬ surface with a first flank surface region 33 h over a height and a subsequent thereto second zone 33 'at a second clearance angle ot2 • Also in this open space design with two flat areas in the transition region through a If the rounded edge merges into one another, the condition is met on a cutting edge normal in each free space area that the greater the distance from the cutting edge, the greater the distance between the cutting edge normals and the workpiece or the cutting plane to be machined.

The lancing insert 25 according to FIG. 3 has a spherical open area. At the start of the turning operation, the machining of a Werk¬ piece 36, at a speed n in the direction of arrow 37 is rotated, the cutting insert is located only with its cutting edge on the workpiece 36, whereas the spherical free ^¬ surface thereof - depending on the distance from the cutting edge - protrudes with increasing distance from the cutting edge. After a certain machining time, a wear zone 47 of height k forms on the cutting tool as a result of the wear.

The cutting insert has secondary cutting edges 38 which converge at an acute angle. The cutting insert can also be provided with a chamfer or, as shown, have rib-shaped chip-forming elements 30, of which only one is arranged here, which points perpendicularly to the center of the main cutting edge. Behind the chamfer 39, which has a greatest width in the cutting corners and initially tapers both towards the main cutting edge center and in the direction of the secondary cutting edges, a chip-forming trough 40 is provided. The lancing insert 25 is moved with the feed f. As shown, the wear zone 47 on the workpiece 36 forms a sliding zone 41 when a groove is inserted. The height k of the wear zone 47 increases with increasing wear of the open area. FIGS. 4 through 11, the different possible Freiflä ^¬ show chenformen. The spherical shape 291 according to FIG. 4 has already been mentioned above. Here, the flank has a convex, ^uniform curvature as seen in the direction perpendicular to the cutting edge, the angles of inclination 292, 293 and 294 being tangential angles of the flank in the region adjacent to the cutting edge, so that the cutting conditions differ in each case optimally adjusted clearance angle results. However, the curved free surface can also have a convex curvature 295 (FIG. 6). If necessary, alternating curvatures are also possible, for example as shown in FIG. 7, from convex to concave or concave to convex (curvatures 296 and 297 according to FIGS. 7 and 8).

The cutting inserts according to FIGS. 9 to 10 each have the same size top surfaces 31 and bottom surfaces 42, so that there is a negative clearance angle (as tangential angle 43) in the crowned free area 298 according to FIG. 9. A positive clearance angle can be achieved if, as shown in FIG. 10, the clearance surface 299 is concave. In addition, the cutting insert can also have a flank chamfer 44 (see FIG. 11), which in the present case is perpendicular to the rake face. This chamfer 44 can be followed by a convex or concave curved or wavy free surface. 9 to 11 can be used as indexable inserts in such a way that both the roof surface 31 and the bottom surface 42 can be used as a rake surface.

With reference to the rhombic cutting plate 21 according to FIG. 12 and the section A - A, B - B and C - C, it is clear that the curvature of the free surface 29 along the cutting edge can also vary or bevels of different widths or be different during turning operations wear zones which adjust after wear can be provided. It can be seen from FIGS. 12a to 12c that the width h ^, h_2, I13 of the chamfer or wear zone grows continuously towards areas away from the cutting corner. In the same Measurements take the clearance angle to 45 and the curvature of Freiflä ^¬ che from.

13a to 13c illustrate different constructions of a cutting insert. The theoretical center line is denoted by 46 from an imaginary center point. The cutting edge forms at the same time the tangent point to Tangentialfreiwin ^¬ kel.

13b illustrates the enlarged tangential clearance angle for the machining of aluminum by displacing the center line (tangential point) above the cutting edge.

Fig. 13c illustrates the stable, soothing shape of the open area by displacing the center line (tangent point) below the cutting edge, e.g. for cast machining.

Claims

1. Cutting insert for chip-forming processing, in particular for turning, milling, piercing and drilling, the at least one-sided top surface of the rake face (28) and the ^¬ running side surfaces form the free surfaces (29), characterized in that the free surface (29) in a vertical Direction to the cutting edge (26; 34) is curved.

2. Cutting insert according to claim 1, characterized in that the free surface (29) is convex and / or concave.

3. Cutting insert according to claim 1 or 2, characterized labeled in ^¬ characterized in that the curvature of the free surface (29) in Wesent ^¬ union circular, parabolic, elliptical or curve 1st or 2nd order is formed descriptive.

4. Cutting insert according to one of claims 1 to 3, characterized in that the on the cutting edge (26) angren¬ free space area (33) is seen substantially over its height h and forms a first positive angle (oi) and that at these Freiflächenbe¬ rich (33) a second zone (33 ') at a second positive clearance angle, if necessary as a variable Tangentialwin¬ kel (0-2) connects, which lies between 5 ° and 30 °, preferably before ^¬ 2 Is up to 5 ° smaller than the first clearance angle.

5. Cutting insert according to claim 4, characterized in that the height (h) is 0.05 mm to 1 mm, preferably 0.05 mm to 2 mm.