MXPA99001716A - Cutting insert - Google Patents

Abstract

A chip cutting insert has an upper chip surface (2), a lower base surface (4), at least three side surfaces (6, 8) and at least two cutting edges (10) formed at the intersection of the upper surface (2) with two insert side surfaces (6). Each cutting edge (10) has leading and trailing ends (30, 32). The side surface (6) associated with each cutting edge (10) comprises an upper primary relief section (20) inclined to the insert base surface (4) at a first interior angle&agr;1, and a lower secondary relief section (22) inclined to the insert base surface (4) at a second interior angle&agr;2, the second interior angle&agr;2 being acute and being different from the first interior angle&agr;1 at least along a part of cutting edge (10).

Description

CUTTING INSERT DESCRIPTION OF THE INVENTION: The present invention relates to a cutting insert for chip cutting operations in particular for use in milling cutting tools. A cutting insert of the kind to which the present invention particularly relates. invention is presented in US Patent 5,447, 396. The insert is produced by pressure molding and subsequent sintering and is formed with a center through hole adapted to receive a gripping screw to mount the insert in an insert receiving pocket of a cutting tool. The insert has an upper pad surface, a lower base surface and two pairs of opposite major major and minor surfaces extending intermediate and defining the upper surface of the insert with respect to the upper and lower cutting edges. Each larger lateral surface comprises upper and lower relief or relief sections intersecting each other at an intersecting line, the upper relief section is curved with a twist and extends outward from the upper insert surface, and the lower relief section it extends inwardly (positively) towards the lower surface of the insert in a conventional manner to function as the insertion surface of the insert, when the insert is mounted in the receiving pocket of the tool. WO 95/17284 teaches an insert similar to that described above in the specific geometry of the relief section or upper relief of the larger lateral surface. However, in the insert of WO 95/17284 the geometries of the upper and lower relieving or relief sections of the larger lateral surfaces are not separately controlled, but rather the lower and upper relief relief sections are in the form of a single lateral surface extending outwardly from the upper insert surface towards the lower insert surface. The smaller insert side surfaces are oriented in a manner similar to that of the larger side insert surfaces so that, when the cutting insert is mounted in an insert receiving pocket of a tool retainer, to present a cutting edge. operative associated with a larger operative side surface, the non-operative minor and larger lateral surfaces extending outwardly function as position surfaces of the insert, thereby forming an effective dovetail grip of the insert in the bag. Therefore the loads applied to the clamping screw by means of which the insert is mounted on the tool, are essentially reduced. However, in a cutting insert as described in WO 95/17284, the extension of the inclination of the insert lateral surface to the base of the insert is limited by the space or light to be provided between the larger lateral surface of the insert. insert adjacent to the base surface of the insert and a surface of the workpiece being machined, limitation which is especially critical with cutting tools having relatively small cutting diameters. Thus in such tools, the available angles of inclination of the greater lateral surface with respect to the base of the insert are close to 90 °, are not suitable for attaching the insert in a dovetail or pigeon fashion. It is an object of the present invention to provide a novel cutting insert having advantages in the indicated aspect. According to the present invention, there is provided a cutting insert chip or chip having an upper tablet surface, a lower base surface, at least three side surfaces and at least two cutting edges formed at the intersection of the surface upper with the two insert side surfaces, each cutting edge comprises a section of upper primary relief inclined to the base surface of the insert in a first interior angle, a second section of lower secondary relief inclined to the base surface of the insert in a second interior angle, the acute interior second angle and is different from the first interior angle in at least a part what;? a3? go the cutting edge. Preferably the first interior angle is also acute, but if required it can be equal or approximately 90 °. with the first interior angle being acute, it is preferable that it be more acute than the second interior angle. Therefore, the side surface of the insert has a shape that, at least along part of the length of the cutting edge, its acute interior angle with the base surface of the insert varies along its maximum value adjacent to the insert. insert base surface. This allows to retain the lights or separations required between the insert, along its entire height and the surface of the piece being machined, and this with the insert having a maximum possible width in its cross section taken perpendicular to the cutting edge at cutting edge. In a preferred embodiment, the insert has a pair of opposed major lateral surfaces, a pair of opposed lower lateral surfaces and a pair of distributable greater cutting edges associated with the opposed major lateral surfaces. preferably the primary relief section of each major side surface is curved, the first interior angle varies along the associated major cutting edge, so that when the insert is mounted on a tool of an appropriate cutting diameter with its cutting edge operative tilted to the tool axis, its angle of relief or lateral relief is basically invariant along its cutting edge. Preferably the secondary relief section is basically planar and constitutes the largest positional surface of the insert. preferably, each minor side surface of the insert is formed with a smaller position surface extending outwardly in the direction of the base surface of the insert. It is also preferable that each minor side surface forms with the upper surface of the insert a lower cutting angle than in the flat view of the insert, at least slightly protruding beyond the minor surface of the insert position. DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention and to show how it can be done in practice, reference will now be made to the accompanying drawings, in which Figure 1 is an isometric view of a cutting insert according to the present invention. invention; Figure 2 is a side view of the cutting insert shown in Figure 1; Figure 3 is a plan view of the cutting insert shown in Figure 1; Figure 4 is a front view of the cutting insert shown in Figure 1; Figure 5 is a cross-sectional view of the insert taken along the line v-v in Figure 3; Figures 6, 7 and 9 are cross-sectional views of the cutting insert taken along the respective lines VI-VI, VII-VII. VIII-VIII and IX-IX in Figure 3. Figure 10 is a cross-sectional view of the cutting insert shown in Figure 1, being mounted on a tool retainer; Figure 11 shows an enlarged detail A in Figure 10; and Figures 12a and 12b are cross-sectional views of a cutting insert according to the present invention. A wafer cutting insert l according to the present invention is illustrated in Figures 1, 2, 3, and 4. As seen in the cutting insert l, it is an adjustable prismatic insert having an upper wafer surface 2, a lower base surface 4, two opposite major lateral surfaces 6 and two minor lateral surfaces 8. The cutting insert 1 has two major cutting edges 10 and two minor cutting edges 12 formed at the intersection of the larger lateral surfaces 6 and minors 8 with the upper tablet surface 2 of the insert. The insert 1 is formed with a central piercing hole 14 adapted to receive a clamping screw for mounting the insert l in an insert receiving cavity formed in a tool holder of a cutting tool (not shown). As seen in Figures 4 and 5 each major side surface 6 has a primary relief section 20, a second secondary relief section 22 and a third section 24 disposed adjacent to the insert base surface 4, sections that are inclined to the base surface of the insert at different first, second and third interior angles designated respectively a, a2 and ar3 in Figure 5. As seen in Figures 7, 8 and 9, in the modality described, the first and second interior angles to the2 are both cut substantially along the entire length of the associated major cut edge 10, the first angle being more acute than the last. The first internal angle α varies along the length of the cutting edge 10, so that when the insert is mounted on the tool with its greater cutting edge operative, being inclined to the axis of the tool, its angle of relief is substantially invariant along the length of the cutting edge. In the described embodiment, the angle α varies from about β 90 ° adjacent the guide end of the insert 30 associated with the minor cutting edge 12, to its minimum value adjacent to the tail end of the insert 32. The secondary relief section 22 of the larger lateral surface of the insert 6 is flat and adapted to function as the largest positional surface of the insert. Thus, the second interior angle a2 is invariant along the length of the cutting edge 12 and can be substantially in the range of 65 to 87 °, depending in particular on the insertion dimensions and a cutting diameter of the tool. of cut. The third interior angle a3 is approximately 90 °. As seen in Figure 1, each minor side surface 8 has a region 34 associated with the minor cutting edge 12 and each region 36 is associated with an edge 38 that has no cutting function. As seen in Figure 3, the minor cutting edge 12 and the region 34 of the minor side surface 8 protrude with respect to the region 36 thereof. As seen in Figures 1 and 2, the minor side surface 8 has a geometry similar to that of the larger side surface 6 because it extends outwardly from the upper insert surface 2 to the insert base surface 4. As shown in FIG. shown in Figures 4 and 5, similarly to the larger side surface 6, the larger side surface 8 has first second and third sections 40, 42 and 44. the first, primary relief section 40 of the region 34 adjacent to the cutting edge 12, preferably has a relief or negative relief geometry, as shown in Figure 6. The second section 42 of the region 36 of the minor side surface, associated with the non-cutting edge 38, is adapted to function as the surface of minor position of the insert. The insert 1 as described above is adapted to be mounted in the insert receiving cavity in the cutting tool in a dovetail manner, as basically described in US 08 / 360,522 or in its corresponding WO 95/17284 which is Incorporate by reference. When the insert cut 1 is mounted on the cutting tool in such a way, that its larger lateral surface not D] and its minor non-operative side surface, which is away from the operative cutting corner of the insert, converge away from it, with the surfaces of major and minor position touching corresponding side walls of the insert receiving cavity. It can be seen in Figures 10 and 11, that in addition to the advantages connected with the dovetail assembly of the insert in the tool, the geometry of the larger lateral surfaces of the insert allows the insert to retain, during a cutting operation, a distance or necessary light C with respect to the piece W that is machined, along the entire height of the insert. It should be specifically noted that a cutting insert with the geometry of the side surfaces according to the present invention can be easily fabricated in the powder metallurgy processes in a nominal manner, preferably by means of a mold design in a die, without necessity of subsequent polishing. The cutting insert of the present invention may have characteristics different from those described. for example, the cutting insert can be triangular, square or have another suitable configuration and therefore have three or more edges of identical major cuts. Depending on the position of the insert in the tool, the angle α defined by the primary relief section of the larger lateral surfaces may be sharper adjacent the leading or leading edge of the operative cutting edge than the adjacent trailing or trailing end. The angle α does not necessarily need to be sharp but can be rather negative positive as illustrated with respect to Figures 12a and 12b. In general, the angle a may be in the range of 90 ° plus or minus 15 °. It is also necessary that the larger side surfaces of the insert have the specific geometry described above along the entire length of the associated cutting edge but can only have it along a part of the part. In addition, the insert cutting edges can have approximately any geometry and orientation. Thus, for example, the larger cutting edges of the insert can be included in the base of the insert. It will be appreciated that the cutting insert according to the present variation may have variations different from those described above.

LIST OF REFERENCE NUMBERS 1 cutting insert 2 upper surface of the tablet 3 lower base surface 6 larger lateral surfaces 8 smaller lateral surfaces 10 major or major cutting edges 12 minor cutting edges 14 central through hole 20 relief section or primary relief of the larger lateral surface 22 secondary relief section of the larger lateral surface 24 third section of the larger lateral surface 30 leading or leading end of the larger cutting edge 32 trailing end or rear of the larger cutting edge 34 region of the lateral surface minor associated with minor cutting edge 5 36 minor lateral surface region not associated with minor cutting edge 38 non-cutting edge associated with region 36 40 first section of lateral surface 10 minor 42 second section of minor lateral surface 44 third section of the minor lateral surface 15

Claims (10)

1. CLAIMS 1. A cutting pad insert having a top pad surface, a bottom base surface, at least three side surfaces and at least two cutting edges formed at the intersection of the top surface with two side surfaces of the insert, each cutting edge having leading and trailing or trailing ends, the lateral surface associated with each cutting edge comprises a primary relief or relief section inclined to the insert base surface at a first interior angle, and a secondary relief section bottom inclined to the insert base surface at a second interior angle, the second interior angle is sharp and different from the first interior angle at least along a part of the cutting edge.
2. 2. - A cutting pad insert according to claim 1, wherein the first interior angle is sharp at least along a part of the length of the cutting edge.
3. 3. - A cutting pad insert according to claim 2, wherein the first interior angle is more acute than the second interior angle at least along a part of the length of the cutting edge.
4. 4. A cutting pad insert according to claim 1, wherein the first interior angle is it equal to 90 ° at least a part of the length of the cutting edge.
5. 5. A cutting pad insert according to claim 1, wherein the first interior angle is obtuse at least along part of the length of the cutting edge.
6. 6. A cutting pad insert according to claim 1, wherein the insert has a stop of opposed major lateral surfaces, a pair of opposing minor side surfaces and a pair of major or major cutting edges associated with the surfaces. lateralee opposite major.
7. 7. A cutting pad insert according to claim 1, wherein the primary relief section is curved, the first inner angle varies along the associated cutting edge so that a relief angle of the insert, lime mounted on the tool, is invariant along the operative cutting edge of the insert.
8. 8. A cutting pad insert according to claim 1, wherein the secondary relief section is basically planar and constitutes the main position surface of the insert.
9. 9. - A cutting pad insert according to claim 6, wherein each minor side surface of the insert is formed with a smaller positioning surface extending outwardly in the direction toward the base surface of the insert.
10. 10. A cutting pad insert according to claim 9, wherein each smaller lateral surface with the upper surface of the insert forms a smaller cutting edge, which in the flat view of the insert, is eobresale when lesser mae ai ^ e of the area of minor poetry of ineerto.