|Title of Invention||
"A CUTTING INSERT FOR MACHINING OF WORK PIECES AND A TOOL THEREFOR"
|Abstract||This Invention relates to a cutting insert for machining of workplaces namely for the roughing-smoothing machining of gray cast iron by surface milling, having a plurality of cutting edges bounding the rake surface of which two adjoining cutting edges form a cutting corner and at least one trough-shaped indentation interrupting the cutting edges whereby the identation is arranged in the cutting corner region and extends into both of the cutting edges forming the cutting corner, the identation is a part spherical segment and that the rake angle (?0 ) lies between +5' and + 20' in the cutting corner region, whereby the identation has a radius of curvature( Rk) between 4 mm and 10mm and the maximum depth (I) of the identation lies between 0.4mm and 0.6mm.|
CUTTING INSERT AND TOOL HAVING A CUTTING INSERT
The invention relates to a cutting insert for a machining of workpieces, especially the roughing-finishing machining of gray cast iron by surface milling and wherein the rake surface is bounded by cutting edges of which two mutually-adjacent cutting edges form a cutting corner and having at least one trough-shaped indentation interrupting the cutting edges.
The invention relates further to a tool comprised of a tool holder with at least one recess for receiving such a cutting insert.
Milling machining is generally carried out in two working steps, a premilling (roughing) and a fine milling. It can be conceived, in that connection, to provide a combined roughing-finishing tool which has a part of the cutting inserts clamped in the recesses (complete seats) provided in the tool holder utilized as purely roughing tools and the remainder utilized as finishing tools- Examples for finishing cutting inserts are described in DE 197 03 569. The cutting inserts there described, which preferably have rake faces as regular hexagons, comprise a plurality of main cutting edges and auxiliary cutting edges connected thereto. As
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has been described in this publication, a cutting insert of that type can be used in combination with a pure cutting insert for
The cutting inserts described in BE 197 03 569 Al have in conjunction with the auxiliary cutting edges a concave chip-forming groove whose radius lies between 0.5 mm and 0.8 ram. With this chip-forming groove the cutting angle of the auxiliary cutter should be set between 10° and 20°. A chip-forming groove also extends along the main cutting edges and in cross section has a radius of curvature of 0.5 mm measured in cross section. This publication does not describe purely roughing turning cutting plates.
A cutting insert is known from DE 28 40 610 C2 which has indentations in the rake face along the cutting edges and of a width of greatest dimension parallel to the cutting edges which is greater than the distance between two neighboring indentations. Each of these indentations interrupts the cutting edge which here has a shape which changes in the region of the interruption, i.e. no longer forms a straight line, but rather in the region of the interruptions have configurations which lie rearwardly of the straight line cutting edge parts in the chip travel direction. Because of these features, buckling is produced in the chip travelling away from the cut which serves to break up the chip into short pieces. The region of a cutting corner should however be free from indentations and instead should have a planar rake surface portion or a negative consolidation surface to avoid an
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increase in the buckling of the chip in the corner region. The mentioned indentations can, according to DE 28 40 610 C2, also be arranged in a chip-forming trough running along the cutting edge. In these publications a trigonally-shaped cutting insert is described which is unsuitable for rough milling operations.
U.S. Patent 4,710,069 describes a cutting insert which has along its cutting edges a chamfer and in the region of the chamfer remote from the cutting edge, a groove-like recess. The boundary line between the mentioned chamfer and the groove-like recess is interrupted by a multiplicity of equally-spaced recesses whose depths should be less than 0.1 mm. The recesses are substantially partially spherical recesses with a radius of curvature of 0.5 am. Such cutting inserts are however only suitable for turning-type machining operations.
The shapes of roughing-finishing inserts which have been provided up to now have in conjunction with the cutting edges and extending over their entire lengths respective chip-forming troughs. In the region of a cutting edge corner, this chip-forming trough is interrupted by relatively higher lying stiffening surfaces. The roughing-finishing machining is however carried out with cutting depths which lie approximately in the range of 0.5 mm to 1 mm. Thus the rounded cutting corner effects cutting so that a modification of the chip-forming groove to increase the chip-forming angle does not yield any effective improvement. Moreover, a lengthening of a chip-forming groove in the cutting corner region while reducing the width of the stiffening surfaces readily reaches
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limits since remaining sharp edged projections, especially in the cutting corner region, readily tend to crumbling which significantly reduces the life of the cutting insert.
It is thus an object of the present invention to provide a cutting insert for roughing-finishing and with which the axial forces arising in milling use are significantly reduced.
This object is achieved with the cutting insert according to claim 1 which, according to the invention, is characterized in that the indentations are arranged in the cutting-corner regions and interrupt both of the cutting edges which adjoin there.
In contrast to the teaching disclosed in DE 28 40 610 C2, to the effect that the cutting corner region should be left free from trough-like depressions or indentations, the cutting inserts formed according to the invention show significantly reduced cutting forces and a resulting improved life by comparison with the previous cutting inserts. Through the use of a spherical segmental recess in the cutting corner regions, significantly larger chip [cutting] angles are permitted and for a cutting insert clamped in a tool holder greater effective radial and axial chip angles can be realized. The cutting edges which are linear except in the cutting corner regions are, as a result of the indentations, concavely curved at their rear parts in the direction of the cutting corners and the cutting corners lie approximately at the height of the linearly running cutting edge level or slightly therebelow. This is repeated in a corresponding manner where the cutting edges adjoin the cutting comers. The cutting insert is used in milling
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in that preferably the cutting edge portions falling away in a concave manner at both sides of the cutting corners are effective for cutting purposes. The maximum width of the indentations in the cutting corner region depends upon the desired cutting depth. In the region of the cutting corner which is effective for the cutting operation, a trough can be formed which allows the positive cutting angle to be optionally selected.
Preferably the indentations are symmetrical to the angle bisectors of the cutting corners.
According to a further feature of the invention, the indentations are formed as part spherically segmental, whereby the radius of curvature of the concave indentations lies between 4 mm and 10 mm. The maximum depth of the indentations should preferably not be greater than 0.4 mm to 0.6 mm.
Since the cutting corners should only be used to an effective cutting depth of 0.5 mm to 1 mm, the maximum diameter of the indentation should be 4 mm.
To maintain a sufficient cutting corner stability, the cutting angle ?0 should lie between +5° and+20° in the cutting corner region, preferably between +8° and +15°.
So that the cutting insert can be used not only on one side but also on the top surface as well as the bottom surface, a central rake face plateau can be provided for two-sided support, the cutting edge planes projecting over the rake surface plateau. The intermediate cutting surface plateau has, according to a
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further feature of the invention, nose-shaped projections which extend into the rearward region of the indentations.
Preferably the cutting inserts of the invention are of regular six-corner form in which the respective mutually-adjacent cutting edges are oriented at an obtuse angle of 120°. The cutting edges are rounded so that, according to a feature of the invention, the cutting corner rounding has a radius between 0.4 mm and 3 mm. As has already been indicated, the cutting insert is configured to be useful on both sides so that twelve usable cutting corners are provided for machining.
The cutting insert according to the invention is preferably received in a recess (plate seat) provided therefor in a tool holder configured as a miller body and are fastened in a recess. For fastening, clamping wedges can be used for fixing the cutting insert with respect to the tool axis. Xt is, however, also possible to arrange the cutting inserts in cassettes which can then be affixed in the tool carrier in the desired orientations. According to the invention, an orientation of the cutting insert for roughing is selected in which it has an effective axial cutting angle ?0 of +5° to +10° and/or an effective radial cutting angle ?0 of 0o to +8° in the cutting insert recess.
An embodiment of the invention is shown in the drawing. It shows
FIG. 1 a turning cutting plate according to the invention in a front view, FIG. 2 a partial section through this turning cutting plate.
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FIG. 3 a turning cutting plate with respect to its mounted
PIGS. 4, 5 respective partial views of the turning plate according
to the invention for showing the cutting angle in the corner
FIG. 6 the same part region of FIG. 5 for a milling insert, PIGS. 7, 8 respective partial views of a cutting corner region for illustrating the spherical segmental configuration and orientation, FIG. 9 a partial view of the cutting corner to show the cutting corner cutting angle y at the rake surface, FIG. 10 a cutting corner partial view for illustrating the radial cutting angle ?0.
The cutting insert 11 shown in the drawing is comprised of a regular six-cornered rake surface which is bounded by six cutting edges 12 of which mutually adjacent cutting edges 12 form a cutting corner 13. The cutting corners 13 are rounded such that the cutting edges have respective planar clearance faces 14 and the corners adjoin rounded clearance face segments 15. On the rake face the cutting insert has a central rake face plateau  which is star-shaped and has respective nose-shaped projections projecting in the direction of the cutting corners. Between two cutting corners, further projections 18 are arranged which are oriented approximately to the center so the respective cutting edges 12. The cutting insert 11 comprises, according to the invention, spherically segmental indentations 19 in the region of each cutting corner on the rake face. The chip-forming groove 20
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runs parallel to each of the cutting edges 12 except in the regions of the spherically segmental identation 19. As can be deduced especially from Fig.l, the nose-shaped projections 17 and 18 are comprised of a lower concave part and an upper convex part. The projections can, however, comprise planar descending flanks or convex or concave flanks. The turning cutting plate has a thickness for example, 5.56 mm and an inscribed circle diameter of 16.2 mm. The turning cutting plate which is configured to be double-sided is preferably used for milling in a tool holder which rotates about the rotation axis 21. The cutting insert 11 travels along the milling radius Rf so that the cutting insert is moved in the direction of the arrow 22 along with other rough cutting inserts. The machining operation which is carried out is shown in greater detail in FIG.6. The workpieces 23 is machined with an end surface miller with a cutting depth ap , whereby a plurality of roughing cutting inserts come into play.
In this milling operation a positive axial cutting angle is provided via the aforedescribed segmental configuration (see FIB.4). FIG. 5 shows a cutting angle ?0 , referring to a cutting depth ap of for example 10.5 mm at a distance to of about 0.5 mm from the cutting edge over a length which corresponds approximately to the selected 0.5 mm tooth feed fz .
From FIB. 7 it will be clear that the depressed part 19 forms a spherical segment- The sphere or partial sphere 24 can be
seen from FIG. 7.
The corresponding spherical radius Rk lies between 4 mm and 10 mm and the maximum segment depth t has a value below 0.4 ram to 0.6 mat.
FIG. 9 shows the cutting angle ? at which the rake surface region bounding the straight line part of the cutting edge 12 is inclined. The radial rake angle ?e which is given by the mounting of the cutting insert in the tool holder is shown in PIG. 10.
A mill provided with cutting inserts 11 is used for the cutting of a workpiece 23. By contrast to the conventional six-cornered turning cutting plates of the state of the art, there is a reduction in the passive force Fp of about 40%.
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1. Cutting insert (11) for machining of workpieces (23), namely for the
roughlng-smoothing machining of gray cast Iron by surface milling, having
a plurality of cutting edges (12) bounding the rake surface of which two
adjoining cutting edges (12) form a cutting corner (13) and at least one
trough-shaped indentation interrupting the cutting edges ( 12), whereby
the identation (19) is arranged in the cutting corner region (13) and
extends Into both of the cutting edges forming the cutting corner,
Characterized in that
(he identation is a part spherical segment and that the rake angle ( ?0) lies between +5' and + 20' In the cutting corner region, whereby the identation (19) has a radius of curvature( Rk) between 4 mm and 10mm and the maximum depth (t) of the identation (19) lies between 0.4mm and 0.6mm.
2. Cutting insert as claimed in claim 1, wherein the identation (19) is arranged symmetrically to the cutting corner angle bisector.
3. Cutting insert as claimed in claim 1 or 2, wherein the maximum diameter (d) of the depression (19) amounts to 4mm.
4. Cutting insert as claimed in claim 1 to 3, wherein the rake angle (?0) lies between +8' and +15' ,
5. Cutting Insert as claimed in claim 1 to 4, wherein the central rake surface plateau (16) is arranged centrally in the rake surface and has nose-shaped projections (17) in the rearward region of the Identatlons (19).
6. Cutting insert as claimed in claim 1 to 5, comprising a regular six- corner shape, preferably with rounded cutting corners (13).
7. Cutting Insert as claimed in claim 6, wherein the cutting corner rounding has a radius between 0.4mm and 3mm.
8. Tool comprised of a tool holder with at feast one recess for receiving a cutting Insert (11) as claimed in one of claims 1 to 7, characterized in that the cutting insert (11) is arranged with an effective axial cutting angle ( ?f) of 0' to +8' In the cutting Insert recess.
This Invention relates to a cutting insert for machining of workplaces namely for the roughing-smoothing machining of gray cast iron by surface milling, having a plurality of cutting edges bounding the rake surface of which two adjoining cutting edges form a cutting corner and at least one trough-shaped indentation interrupting the cutting edges whereby the identation is arranged in the cutting corner region and extends into both of the cutting edges forming the cutting corner, the identation is a part spherical segment and that the rake angle (?0 ) lies between +5' and + 20' in the cutting corner region, whereby the identation has a radius of curvature( Rk) between 4 mm and 10mm and the maximum depth (I) of the identation lies between 0.4mm and 0.6mm.
|Indian Patent Application Number||IN/PCT/2001/634/KOL|
|PG Journal Number||08/2007|
|Date of Filing||18-Jun-2001|
|Name of Patentee||WIDIA GMBH|
|Applicant Address||MUNCHENER STRASSE 990 D-45145 ESSEN|
|PCT International Classification Number||B 23C 5/20|
|PCT International Application Number||PCT/DE99/03785|
|PCT International Filing date||1999-11-25|