WO1993013899A1

WO1993013899A1 - Cutting-tool bit

Info

Publication number: WO1993013899A1
Application number: PCT/DE1992/001092
Authority: WO
Inventors: Wolfgang Hintze; Dieter Rupietta
Original assignee: Krupp Widia Gmbh
Priority date: 1992-01-17
Filing date: 1992-12-28
Publication date: 1993-07-22
Also published as: DE4201112A1; DE4201112C2

Abstract

The invention concerns a cutting-tool bit for metal-cutting, in particular turning, operations, the bit having a flat cutting surface with an undulating cutting edge (25) and a similarly undulating shaft surface. The mutually parallel undulation peaks at right angles to the cutting edge (25) are tangential to the plane (27) which passes through the corners (23) of the cutting edge (25) and which is at right angles to a plane formed by all the cutting edges (25).

Description

description

Cutting insert

The invention relates to a cutting insert for machining, in particular for turning, with an edge-free rake face that is wavy in the direction of the cutting edge.

Such cutting inserts are known, for example, from DE 37 31 426 AI in such a way that the rake face of the cutting insert is not only undulating in the direction of the cutting edge, but also runs straight to undulating perpendicular to it.

DE 25 44 991 C2 already describes a cutting insert with a wave-shaped cutting edge and a plurality of wave-shaped chip breaker stages arranged in terraces. The chip breaker stages are intended to act on the chip in many and in different directions effective chip shape pressures which vary over the chip width, so that it is deformed criss-cross in a strong manner and consequently breaks quickly and briefly.

According to EP 0 166 898 B1, a cutting insert is known in which the cutting edge has indentations in places, which form edges on the rake face and corners on the cutting edge.

A cutting insert is also described in DE 28 40 610 A1, the cutting edges of which are interrupted by grooves or indentations which extend on the rake face and start from the perforated part of the cutting edge. An increased plastic deformation of the chip should be achieved by making the transition between the rake face and cutting edge or the indentation as pronounced as possible, ie by forming the transition zones with sharp edges. Corresponding recesses or notches on the Cutting edges are according to DE 28 50 026 AI he ^¬ aims that the free surface has respective recesses or notches that decrease in the direction away from the associated cutting edge. Even where the open areas run out in the form of a wavy line in a view of the rake face, the wave crests should be cut off so that milling teeth or straight cutting edge sections form between two troughs and the cutting edge ^sections on the opposite rake face complete with the opposite sections on the underside to a full cut, which is achieved in that there is a wave crest on the upper rake face opposite the wave troughs.

US-A-4,681,486 describes further open-space recesses which extend conically from the rake face with a positive open face to the contact surface.

EP 0 414 241 A2 describes a cutting insert with indentations breaking through the cutting edge on the rake face, which continues in corresponding indentations in the free surface, the indentations or indentations having a trapezoidal shape in cross section.

Due to the exposed corners or edges of the cutting inserts described above, they are exposed to increased wear. As far as the cutting inserts show a wave shape, however, this is insufficient or insufficient to ensure safe chip guidance and removal. It is therefore an object of the present invention to improve the cutting insert mentioned at the outset in such a way that chatter vibrations are avoided during turning operations, such as copying out, as is the jamming of broken chips between the free tool surface and the workpiece shoulder. The chip should run on the chip face with as little friction as possible and through its plastic deformation during the cut can be greatly expanded by bending so that it breaks more easily than with cutting inserts known from the prior art.

This object is achieved by the cutting insert described in claim 1, which is characterized in that the respectively adjacent free surface is wave-shaped, the mutually parallel wave crests perpendicular to the cutting edge affecting the plane which runs through the corner points delimiting the cutting edge and which is perpendicular to a plane formed by all cutting edges. Not only the rake face, but also the free face is thus undulating along the cutting edge in the area adjacent to the cutting edge. The open area runs in the area of the cutting corner towards a wave crest. Due to this design, the chip assumes a strongly undulating cross-section, whereby it is stretched more when bent, i.e. breaks more easily. At the same time, with larger chip thicknesses, a softer cut is achieved through lower cutting forces.

Further refinements of the invention are described in claims 2 to 15.

The distance between the wave crests and the wave troughs is a maximum of 5 to 30%, preferably 8 to 16% of the cutting insert thickness, preferably it is between 0.07 and 1.6 mm, in particular between 0.15 and 0, 8 mm. With this dimensioning, the advantage can additionally be achieved that the cutting insert can be clamped in standardized tool holders.

According to a further embodiment of the invention, the number of wave crests on the open area is at least 3, at most 20, preferably between 3 and 8. This means that ensures that a sufficient contact of the Schneidein ^¬ set is in its holder so that standard holder ver ^¬ are reversible. The number of wave crests on the rake face is between 2 to 20, preferably 2 and 8.

Furthermore, preferably in cross-sectional planes parallel to the rake face and / or to the free face, the shafts on the free face and / or on the rake face run at least partially with a curvature which corresponds to a circle radius between 0.5 to 40 mm.

The open surfaces and rake surfaces formed from wave crests or wave crests and wave valleys and the resulting wavy cutting edge consist of waves of the same dimensions, i.e. the wave crests and troughs are equally spaced from one another and have the same wave depth.

Furthermore, the wave-shaped rake surface along the cutting edge preferably has convex sections falling from the circular or cylindrical segments with radii of 20 to 40 mm and a concave central region with radii of 0.5 to 15 mm, falling towards the center of the cutting edge. The undulating open area consists of circular or cylindrical segments. This can have the effect that the chip segments generated by several shafts of the cutting edge run in different directions, thereby counteracting a knotting of the chip segments with one another.

According to a further embodiment of the invention, the wave ridges are widened into straight sections with a length of 0.1 to 2 mm, preferably 0.3 to 1 mm.

As an alternative to the shafts of the same length, according to a further embodiment of the invention, the wavelength can be along the cutting edge or in a parallel to it Wave crest to be different from the next wave crest, the wavelength preferably being between 2 and 8 times the corner radius. Due to the increasing wavelength towards the sharp corner of the insert, greater stability of the cutting corner is achieved. Larger wavelengths also result in a greater distance between the chip segments being formed, which furthermore prevents the chips from becoming entangled. Preferably, the wavelength increases towards the center of the cutting edge.

Further variants of the principle according to the invention are given in that the convex regions of the shafts have radii of curvature that are 2 to 20 times larger than the concave regions, as a result of which greater cutting edge stability can be achieved. In these embodiments, an approximately sinusoidal wave is deliberately deviated by making the wave crests wider and the wave troughs shorter.

Further variants are possible in that the convex areas of the shafts facing away from the cutting corner have a smaller radius of curvature than the convex areas facing the cutting corner, preferably 1 to 4 mm compared to 8 to 40 mm. It is hereby achieved that, for example, when cutting out, the chip width of the chip segments is reduced and the chip thickness is increased, whereby chip breaking can be further improved compared to a wave cutting edge made of the same radii.

Furthermore, the wavy rake face is preferably additionally inclined by an angle of inclination which is in the range between 2 and 15 °. This positive rake face geometry serves to further reduce the cutting force and prevents damage to the machined workpiece surface by chips. In order to better protect the insert seat against chips and to prevent chips from penetrating between the cutting bodies and the support, the inclined serrated edge in the area of the corner forming an obtuse angle is raised to the height of the corner forming an acute angle in the case of indexable inserts with rhombic or polygonal cutting bodies.

Furthermore, chip-forming steps or chip-forming elements are preferably arranged at a distance from the cutting edge, possibly in a row along a parallel of the cutting edge. If one chooses a chip form step as chip form element, the chip form step outlet is preferably formed by waves corresponding to the wavy cutting edge form. In this way, the contact between the chip and the cutting body and consequently the cutting force is further reduced. When turning longitudinally with a large chip width and a small chip thickness, the guidance of the chip and thus the chip break is improved.

Embodiments of the invention are shown in the drawings. Show it

1 is a perspective view of a cutting insert according to the present invention,

2 is a top view of the cutting insert of FIG. 1,

3 is a side view of the cutting insert according to FIG. 1 or 2,

4 shows a side view of a cutting insert in an alternative embodiment with draining chips,

5 shows a schematic top view of a further cutting insert, 6 shows a perspective view of the further cutting insert according to FIG. 5,

7 shows a further embodiment of the cutting insert according to the invention in a top view,

8 to 10 are perspective views of further cutting inserts according to the invention,

11 is a plan view of a further cutting insert and

FIG. 12 shows a cutting insert corresponding to FIG. 11 in a perspective view.

The cutting insert according to the invention is generally designed as a cutting insert and each has an upper rake face 21 and a lower rake face 22. The rake face has a polygon shape when viewed from above, is generally triangular, square or in particular rhombic or rectangular, square or polygonal educated. In the illustrated embodiment, the rake face 21 forms four cutting corners 23. A common boundary of the respective free surfaces 24 and the rake surfaces 21 and 22 is formed by the cutting edge 25, which has a wave-shaped course following the relevant design of the rake surface and the free surface. The indexable insert has a fastening hole 26 or, at a suitable point, a clamping trough for receiving a clamping claw or a similar fastening means. As can be seen in particular from FIG. 5, the free surface 24 has wave crests reaching from cutting edge to cutting edge and valleys in between, which are arranged in such a way that the crests 25a (in contrast to the valleys 25b) lie in a plane 27 in which the corner points 23 lie and which is perpendicular to a plane formed by all the cutting edges 25. Level 27 can can be seen as the envelope of the open space. This construction means that the wave shape of the open area at the cutting corner tends to a maximum, ie a wave crest or wave crest. The rake face is also wave-shaped along the cutting edge 25, it follows the wave course given by the free face. At a distance from the cutting edge 25, which is either at an angle of inclination of 0 ° (see FIG. 3) or has a positive angle of inclination, is the base point 28 of a central chip-forming element 29 which, with the exception of the circumferential rising surfaces, is flat. This central plateau projects beyond the circumferential cutting edge 25. The maximum distance 30 (see FIG. 5) of the wave crests or wave crests 25a and valleys 25b is between 8 to 16% of the plate thickness 31, preferably in the range between 0.15 to 8 mm . As can be seen in particular from FIG. 3, the cutting insert can be clamped in standardized tool holders without any problems.

The wave shape of the rake face, the cutting edge 25 and the flank face 24 is approximately sinusoidal, with the respective curvatures of the wave crests and / or valleys corresponding to a circle radius between 0.5 to 40 mm in any cross-sectional planes parallel to the rake face or to the flank face. In the present case, each cutting edge or free surface has four valleys 25b and five wave crests 25a, of which the two outer ends end in the corners 23.

With the shape design described above, an indexable insert of the shape CNMG 120408 was used for turning. The corresponding waves on the chip face and the free face are composed of circles with a radius of 2.7 mm. The height of the waves, ie the distance 30 was 0.16 mm. A flat shoulder was machined radially from the inside out on a workpiece made of Ck 45. The measurements on the shoulder were varied in the range from 0.2 to 0.9 mm, the feeds in the range from 0.2 to 0.4 mm. The cutting insert according to the invention each delivered individual broken chips of about 1 mm width.

In comparison to this, a cutting insert which only had a wavy rake surface delivered unbroken, 3 to 4 mm wide spiral chips which tangled. A comparatively investigated cutting insert with a straight cutting edge also produced 3 to 4 mm wide, unbroken, tangled band chips.

The chips 32 which arise in each case when copying out are shown in FIG. 4, for example. The shaping of the rake face by means of circular segments 33 with radii of 20 to 40 mm effectively prevents chips 32 from becoming tangled, since the chips 32 run in different directions.

As can be seen from FIGS. 5 and 6, however, the wavelength along the cutting edge 25 can be variable, a greater stability of the cutting corner being achieved by a wavelength increasing towards the sharp corner of the indexable insert. Here, the wavelength 34a increases over 34b to the longest wavelength 34c in the direction of the pointed corner of a rhombic indexable insert. The rhombic cutting plate shown in FIG. 7 has two opposing pointed cutting corners 23, the convex regions 35 having a radius of curvature at least twice as large as the concave regions 36. In addition, the convex areas 37 facing away from the pointed cutting corner have a smaller radius of curvature than the convex areas 38 facing the cutting corner, for example in a ratio of 1:10. In addition to the embodiment already described in FIG. 7, the cutting insert according to FIG. 8 another inclined serrated cutting edge 25, the inclination angle 39 is about 5 °. When cutting with the respective acute-angle cutting corner 23 the friction of the trailing chip is on ^¬ reason of the inclination angle 39 significantly reduced.

FIG. 9 shows a corresponding embodiment according to FIG. 8, but with a chip-forming element 29, which lies without inclination in a plane perpendicular to the plane defined by the free surfaces 24 and projects beyond the corners 23.

If it is desired to prevent chips from penetrating between the cutting body and the support and better protecting the insert seat from chip impact, the inclined shaft cutter 25 in the region of the blunt corner can be increased to the height or in the plane by raising 40 the pointed cutting corners 23 are raised.

According to Fig. 11, the chip form stage run-out, i.e. the respective base point 28 or the line formed thereby is formed by a shaft corresponding to the undulating cutting edge 25. According to FIG. 12, this can also be done in conjunction with a chip-forming element 29 which is perpendicular to the plane defined by the free surfaces 24 and thus does not follow the angle of inclination or the falling of the cutting edge. This results in full contact surfaces on the top and bottom of the rake faces 21 and 22.

Claims

1. Cutting insert for machining, in particular for turning, with a wavy edge-free chip face (21, 22) in the direction of the cutting edge, characterized in that the respectively adjacent free surface (24) is wave-shaped, the mutually parallel wave crests perpendicular to the cutting edge (25) tangent to the plane (27) which runs through the corner points (23) delimiting the cutting edge (25) and which is perpendicular to a plane formed by all the cutting edges (23).

2. Cutting insert according to claim 1, characterized gekennzeich¬ net that the distance (30) of the crests (25a) to the troughs (25b) is a maximum of 5 to 30%, preferably 8 to 16% of the cutting insert thickness (31), preferably is between 0.07 and 1.6 mm, in particular 0.15 and 0.8 mm.

3. Cutting insert according to claim 1 or 2, characterized ge indicates that the number of crests on the free surface (24) is at least 3 to at most 20, preferably between 3 and 8 and / or that the number of crests on the rake face (21, 22) is at least 2, at most 20, preferably between 2 and 8.

4. Cutting insert according to one of claims 1 to 3, characterized by the fact that in each case in cross-sectional plane parallel to the rake face (21, 22) and / or to the free face (24) the shafts (25) on the free face (24) and / or extend at least partially on the rake face (21, 22) with a curvature that corresponds to a radius of a circle between 0.5 to 40 mm.

5. Cutting insert according to one of claims 1 to 4, since ^¬ characterized in that the waves each have crests (25a) or valleys (25b) with the same distance from each other and / or the same wave depths or heights Own (30).

6. Cutting insert according to one of claims 1 to 5, da¬ characterized in that the wavelength (34a to c) in a parallel to the cutting edge (25) from Wellen¬ mountain (25a) to the next wave crest (25a) is different, is preferably between 2 to 8 times the corner radius.

7. Cutting insert according to claim 6, characterized gekennzeich¬ net that the wavelength (34a to c) to the cutting corner is greater.

8. Cutting insert according to one of claims 1 to 7, da¬ characterized in that the convex regions (35) of the shafts have 2 to 20 times larger radii of curvature than the concave regions (36).

9. Cutting insert according to one of claims 1 to 8, da¬ characterized in that the undulating Freiflä¬ surface (24) consists of circular or cylindrical segments and / or that the undulating rake face (21, 22) convex, sloping towards the cutting center sections from circular or cylindrical segments with radii from 20 to 40 mm and a concave central region with radii from 0.5 to 15 mm.

10. Cutting insert according to one of claims 1 to 9, da¬ characterized in that the crests are ge to straight sections with a length of 0.1 to 2 mm, preferably 0.3 to 1 mm, widened.

11. Cutting insert according to one of claims 1 to 10, as ^¬ characterized by that the cutting corner zu¬ facing convex portions (38) have from the cutting corner ab¬ facing convex portions (37) of the shafts a ge ringeren radius of curvature than that ^¬ preference, from 1 to 4 mm, compared to 8 to 40 mm.

12. Cutting insert according to one of claims 1 to 11, characterized in that the wavy rake face (21, 22) is additionally inclined by an angle of inclination (39) which is in the range between 2 to 15 °.

13. Cutting insert according to claim 12, characterized by a double-sided rhombic shape or polygon shape, in which the inclined undulating cutting edge (25) in the region of the obtuse angle corner is raised to the height of the corner forming an acute angle.

14. Cutting insert according to one of claims 1 to 13, da¬ characterized in that chip-forming steps or elements (29) are provided at a distance from the cutting edge (25).

15. Cutting insert according to claim 14, characterized gekennzeich¬ net that the chip form step outlet (28) is formed by the corrugated cutting edge (25) corresponding waves.