DE20014428U1 - Cutting insert - Google Patents

Description

Description cutting insert

The invention relates to a cutting insert for machining workpieces with a plurality of cutting edges, in particular for roughing, wherein a cutting corner is arranged between adjacent cutting edges, either curved or composed of a plurality of short edge sections, each of which is straight and arranged at an obtuse angle to one another.

Such cutting inserts, which may also have a circumferential bevel, are known in the art. In order to achieve a high surface quality as a machining result for combined roughing and finishing, DE 197 03 56 9 A1 proposes that the secondary cutting edge, which is adjacent to a flat flank, be convexly curved. The cutting insert described in this publication can be designed in particular as hexagonal when viewed from above onto the chip face, i.e. it has a total of six cutting edges of equal length, three of which are designed as main cutting edges and three as secondary cutting edges. A concave chip-forming groove extending parallel to the secondary cutting edge is adjacent to the chip face. A raised chip-forming element is preferably arranged approximately at the height of the main cutting edge center perpendicular and at a distance from the main cutting edge, which can be designed in particular as a nose-shaped projection of a central raised chip face plateau. This projection may have a substantially triangular flat roof surface lying in the chip surface plateau plane, the

The tip is directed towards the main cutting edge and the side lines adjacent to this tip have inclined flanks that extend down to the chip face, preferably at a flank angle of 40° to 50°.

It is the object of the present invention to optimize the cutting insert mentioned above, in particular for face milling work on gray cast iron parts.

This object is achieved by the cutting insert according to claim 1, which is characterized according to the invention in that a chamfer is arranged on the chip surface, which extends along the cutting edge, and that this chamfer in the middle of the cutting edge has a chamfer width that is 1.5 to 4 times, preferably 2.5 to 3.5 times larger than the width of the chamfer areas on both sides. This cutting insert is particularly suitable for face milling gray cast iron or cast steel materials whose surface has a cast skin. The position of the chamfer, which is wider than the other areas, is selected such that in the area of the maximum cutting depth a _ptnax , where the cutting edge comes into contact with the cast skin, the cutting edge is protected against premature wear or cutting edge breakage by a wider chamfer.

Further developments of the invention are described in the subclaims.

The widened bevel preferably extends over 1/3 to 1/2 the length of the cutting edge, while still retaining preferential

the bevel widening is arranged symmetrically to the cutting edge center. This measure allows the cutting inserts to be used one after the other for right- and left-turning cutting operations, with the widened bevel always being arranged in the middle area of the cutting edge, i.e. where, depending on the selected maximum cutting depth, the cutting edge comes into contact with the (surface) casting skin or the chip deposited here, e.g. when machining engine blocks. In the area of the cutting edge close to the cutting corner, the bevel width returns to the smaller width b _x and tapers off to the width 0 towards the cutting corner, but can also be designed as a circumferential bevel with the width b _x in the cutting corner.

According to a further embodiment of the invention, the bevel angle is constant over the entire bevel or changes by a maximum of ±10° along the cutting edge. The bevel angles are either 0° or smaller, preferably they are between -10° and -20°.

The transition from the smaller chamfer width to the larger chamfer width is preferably selected such that the widened chamfer tapers to smaller lengths towards the chip surface areas further away from the cutting edge, the extent of the taper being determined by the boundary lines of the widened chamfer, which are arranged at an angle of between 3° and 30°, preferably between 15° and 25°, to the cutting edge orthogonal line lying on the chip surface. This cutting edge taper or the arrangement of the boundary lines in question is preferably also mirror-symmetrical to the cutting edge.

middle. Alternatively, however, chamfer designs are also possible in which a continuous transition of the chamfer widening is selected between the narrower and the wider chamfer.

On the chip face, the widened bevel is followed on the back over its entire length by a first chip forming element with a roof surface at an angle of 0° to -20°, whereby the angle of this roof surface is chosen to be the same or larger than the chip face angles of the adjacent areas, preferably by about 10°. This first chip forming element slopes down on both sides over flat flanks to the chip face surrounding this chip forming element, whereby the flank inclination is preferably between 10° and 30°. Like the bevel widening, this first chip forming element is also arranged mirror-symmetrically to the cutting edge center perpendicular.

The cutting insert preferably has a central raised chip surface plateau which is at a distance from the highest cutting edge elevation. The chip surface plateau has a nose-shaped projection approximately at the height of the main cutting edge central vertical at a distance from the main cutting edge, which preferably projects into the first chip forming element. The nose-shaped projection can have an essentially triangular flat roof surface lying in the chip surface plateau plane, the tip of which is directed towards the cutting edge and from whose side lines adjacent to this tip inclined flanks reach down to the chip surface or to the first chip forming element, preferably at a flank angle of 40° to 50°.

The cutting corner formed between two adjacent cutting edges is rounded or consists of several linear sections, each at an obtuse angle to each other and to the respective adjacent cutting edge.

The cutting insert has a triangular, square or hexagonal shape, preferably with usable cutting edges arranged on both the top and bottom.

The shape of the cutting edges can be straight, concave or convex, whereby the chamfer including the chamfer widening is adapted to or follows the respective cutting edge formation.

Further advantages and embodiments of the invention are explained below with reference to the drawings.

Fig. 1 is a perspective view of a cutting insert according to the invention with a hexagonal basic shape,

Fig. 2 a side view of the cutting insert according to

Fig.1,

Fig. 3 a plan view of the cutting insert according to

Fig. 1 and 2,

Fig. 4 is a partial sectional view along the line A-A

in Fig. 1,

Fig.5

a partial sectional view along the line B-B in Fig. 3,

Fig.6

another embodiment of a cutting insert according to the invention in a partial sectional view and

Fig.7

a partial view of a cutting insert according to the invention according to Fig. 1 to 5 during machining.

As can be seen from Fig. 1 to 3, the cutting insert with a regular hexagonal basic shape has six cutting edges 10 of equal length, which are inclined to the adjacent cutting edge at an obtuse angle of 120° and which each pass over rounded cutting corners 11 to the adjacent cutting edge. The cutting corner radius is between 0.3 and 0.9 mm. The hexagonal cutting insert shown is designed as a double-sided indexable insert, i.e. it has six cutting edges on the top and bottom. The support surface for the cutting insert is a chip surface plateau 12 arranged on the top and bottom, which has several nose-shaped projections 13, the tip of which is aligned with the center of the cutting edge 10. Each of the cutting edges 10 is followed by a bevel on the chip surface, the design of which is the subject of the present invention. This chamfer is not uniformly formed along the main cutting edge, as is the case with cutting inserts known from the state of the art, but has a larger width in the middle area. Over a length I ₁ (see Fig. 3), which is approximately 1/3

of the cutting edge length measured from the cutting corner vertex to the adjacent cutting corner vertex, the chamfer has a width b ₂ which is 1.5 to 4 times, preferably 3 times, the chamfer width b _x of the adjacent chamfers 14 with a respective length I ₂ that run out to the respective cutting corner 11. The widened chamfer 15 is arranged mirror-symmetrically to the cutting edge mid-perpendicular 16, wherein the chamfer angle -1 γ _1# , which is preferably negative, is chosen to be the same for the chamfers 14 and 15. The chamfer angle dimension selected in the exemplary embodiment (see Fig. 4) is J ₁ = 15° . The width dimension b ₂ in the exemplary embodiment is 0.3 mm compared to a chamfer width b _x = 0.1 mm. At the rear of the widened bevel 15, a chip forming element 17 is attached to the chip face, which is raised compared to the surrounding chip face areas 18 due to the wider bevel 15. The lateral boundary lines 19 of the widened bevel 15 are inclined relative to the perpendicular bisector by an angle P ₁ or ß ₂ of between 15° and 25°, whereby the angular dimensions P ₁ = P ₂ are due to the symmetrical design selected for the perpendicular bisector 16. The chip forming element 17 slopes down to the adjacent areas via flanks 20 which are inclined at an angle Ct ₁ of between 10° and 30° and which are flat. In the present case, the angular dimension Oc ₁ is approximately 25°. Each of the nose-shaped projections 13 forms a surface lying in one plane with the central raised plateau 12, which can be used as a support surface. The side flanks 21 of the nose-shaped projection 13 or the corresponding remaining flanks from the central plateau to the chip surface areas effective during cutting are at an angle between 40° and 50°

The respective boundary lines 22 of the chip forming element 17 are inclined at an acute angle with respect to the perpendicular bisector 16, just like the boundary lines 19 already mentioned, the angle dimension B ₁ or B ₂ being equal to the angles P ₁ = ß ₂ mentioned.

The chamfer widening according to the invention can also be implemented in particular on cutting inserts with three or four corners.

The design of the chip forming element 17 can also be seen in Fig. 6, in which a chip surface section 23 is arranged on the chip surface on the rear side of the widened bevel 15, which chip surface section is located higher than the chip surface section 24 and can optionally also be designed concavely in the sense of a groove-shaped curved surface extending parallel to the cutting edge.

The cutting edges 10 can, as shown in the embodiments, be straight or alternatively (viewed in a side view of the flank) concave or convex. In such embodiments too, the cutting edge on the chip surface is followed by a bevel along the cutting edge 10, which is enlarged in the middle of the cutting edge to a wider bevel 15 at the same bevel angle.

The mode of operation of the bevel design according to the invention can be seen by way of example in Fig. 7. When machining a gray cast iron workpiece 25 with a cast skin 26 on the surface, the cutting insert 27 engages during face milling in the manner shown in Fig. 7. The cutting edge part designated 28 serves as the cutting edge. In the area of the maximum ♦· ·· ·· .; ; i ·**. .**. J &iacgr;·&iacgr;

Cutting depth a _pmax/ namely where the cutting edge 28 comes into contact with the casting skin 2 6 or the chips removed there, there is the widened chamfer 15 which protects the cutting edge 28 against premature wear.

Claims (15)

1. Cutting insert for machining workpieces with a plurality of cutting edges, in particular for roughing, wherein a cutting corner ( 11 ) is arranged between adjacent cutting edges, which is curved or composed of a plurality of short edge sections, each of which is straight and arranged at an obtuse angle to one another, characterized in that a bevel is arranged on the chip surface and extends along the cutting edge ( 10 ), and that this bevel has a larger bevel width (b ₂ ) in the middle of the cutting edge ( 10 ) than the bevel areas ( 14 ) adjoining on both sides , compared to the width (b ₁ ) of the bevel areas ( 14 ) adjoining on both sides, wherein the larger bevel width (b ₂ ) is 1.5 to 4 , preferably 2.5 to 3.5 times as large as the width of the bevel adjoining on the side. 2. Cutting insert according to claim 1, characterized in that the bevel widening ( 15 ) extends over 1/3 to 1/2 the length of the cutting edge ( 10 ). 3. Cutting insert according to claim 1 or 2, characterized in that the bevel widening ( 15 ) is arranged mirror-symmetrically to the cutting edge center perpendicular ( 16 ). 4. Cutting insert according to one of claims 1 to 3, characterized in that the chamfer angle (γ ₁ ) is constant over the entire chamfer ( 14 , 15 ) or changes by a maximum of ± 10 ° along the cutting edge ( 10 ). 5. Cutting insert according to one of claims 1 to 4, characterized by a chamfer angle (γ ₁ ) of ≤ 0°, preferably from -10° to -20°. 6. Cutting insert according to one of claims 1 to 5, characterized in that the widened bevel ( 15 ) tapers to smaller lengths in areas further away from the cutting edge ( 10 ), the extent of the taper being determined by boundary lines ( 19 ) of the widened bevel ( 15 ) which are arranged at an angle (ß ₁ , ß ₂ ) between 3° and 30°, preferably between 15° and 25°, to the cutting edge perpendicular ( 16 ). 7. Cutting insert according to claim 6, characterized in that the boundary lines ( 19 ) are arranged mirror-symmetrically to the cutting edge center perpendicular ( 16 ). 8. Cutting insert according to one of claims 1 to 7, characterized in that a first chip-forming element ( 17 ) with a roof surface at an angle of 0° to -20° is arranged on the rear side of the widened bevel ( 15 ) over its entire length. 9. Cutting insert according to claim 8, characterized in that the first chip-forming element ( 17 ) slopes down on both sides over flat flanks ( 20 ) to the chip surface ( 18 ) surrounding this chip-forming element, wherein the flank inclination (α ₁ ) is preferably between 10° and 30°. 10. Cutting insert according to claim 9, characterized in that the first chip forming element ( 17 ) is arranged mirror-symmetrically to the cutting edge center perpendicular ( 16 ). 11. Cutting insert according to one of claims 1 to 10, characterized by a central raised chip surface plateau ( 12 ) which is at a distance from the highest cutting edge elevation and which has a nose-shaped projection ( 13 ) approximately at the level of the cutting edge center perpendicular ( 16 ) at a distance from the cutting edge ( 10 ), which preferably projects into the first chip forming element ( 17 ). 12. Cutting insert according to claim 11, characterized in that the projection ( 13 ) has a substantially triangular flat roof surface lying in the chip surface plateau plane, the tip of which is directed towards the cutting edge ( 10 ) and from whose side lines adjacent to this tip inclined flanks ( 21 ) extend down to the chip surface, preferably at a flank angle of 40° to 50°. 13. Cutting insert according to one of claims 1 to 12, characterized by a substantially regular hexagonal shape with six cutting edges which delimit the chip surface, preferably with two chip surfaces arranged parallel to one another. 14. Cutting insert according to one of claims 1 to 12, characterized in that the cutting insert has a triangular or square shape. 15. Cutting insert according to one of claims 1 to 14, characterized in that the cutting edge is concavely or convexly curved or straight in a plan view of the adjacent free surface, wherein the chamfer widening ( 15 ) follows the formation of the cutting edge.