MXPA96002208A - Cutting insert and cutter for milling - Google Patents

Abstract

An insert for milling applications in which a radial rake face includes a concave conical portion defined to achieve constant positive radial rake throughout the length of a radial cutting edge at the angle of inclination thereof as the insert is intended to be mounted in a cutter body. The insert includes an axial rake face having a sloping portion defined to achieve positive axial rake as the insert is intended to be mounted in a cutter body. The upper surface of the insert includes planar regions and bend surfaces merging smoothly with the radial rake faces and axial rake faces to assist in chip expulsion during cutting.

Description

CUTTING INSERT AND CUTTING TOOL FOR MILLING BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an insert, particularly an insert that is adapted to be removably mounted on a tool holder, for use in milling operations. The cutting inserts of the present invention are generally made of agglomerated metal carbide, such as tungsten carbide, and are formed by pressing techniques, after which the pressed articles are sintered. Description of the Prior Art Cutting inserts for milling are well known in the art. It is known to provide such inserts having polygonal shapes, straight cutting edges and surface configurations to increase chip control. Figures 7 and 8 illustrate a milling tool of known type, with an insert 104 mounted thereon. While only a single insert is illustrated in Figures 7 and 8, tools of this type may include a plurality of grooves, such as groove 120, each providing a recess for mounting an insert. In use, the body 100 of the tool is rotated about the axis 102, and the revolution surfaces generated by the cutting edge (s) of the insert (s) are cylindrical. Figure 9 illustrates the circle circumscribed by a point on a radial cutting edge 108 of the insert 104 by rotation of the body 100 of the tool. An axial cutting edge 106 cuts a face at the base of the cylinder cut by the radial cutting edge 108. So-called positive inserts are proposed for applications in which a. cutting edge gives rise to the face of the recess angle of the insert during chip formation. Such applications depend on a relatively greater shear stress in the formation of chips than applications in which the cutting edge delays the face of the recess angle of the insert in the formation of chips. In order to provide an advancing cutting edge and allow clearance between the flank of the insert and the work during shaving, an included angle between the face with the recess angle of the insert and the surface of the flank of the insert becomes acute. However, the resistance of the cutting edge tends to be directly proportional to the magnitude of the included angle, that is, the greater the included angle, the greater the resistance of the cutting edge. The design of the insert finds a balance between these competent demands, according to the proposed application, and the concessions are dictated by the nature of the material that is going to be cut, and the type of cut. For example, for cutting materials such as aluminum, which are relatively highly machinable, relatively narrow included angles can be used. Conversely, for materials such as steel, which are relatively less machinable, the edge strength must be greater, and hence, relatively long angles included are preferred. Additionally, applications involving a coarse cut, involving relatively thicker chip formation, require a relatively greater edge strength than finishing operations that involve the formation of relatively thinner chips. In the tool of Figures 7 and 8, a so-called positive insert is an insert which provides both a positive radial recess angle and a positive axial recess angle, i.e. cutting edges 108 and 106 are proposed to give Place the faces with radial and axial recess angle respects the insert during cutting. It is known to provide inserts for such applications, in which the configurations on the surface containing the faces with recess angle are proposed to increase the radial and axial recess angle in accordance with the proposed orientation of the insert within the body of a tool of cut. Nevertheless, with such known inserts, at increasing depths in the design of the cut, the concessions result in weakness of the cutting edge which is manifested in the breaking of the edge away from the advancing edge. In addition, such known inserts are provided with material enlarged around the periphery of the mounting opening, which can result in the binding of chips, inhibiting their ejection during cutting. A further drawback of the known inserts comes from the orientation of the insert within the recess of the tool body. In Figure 8 an angle 112 (shown greatly exaggerated) is measured between a longitudinal centerline of the insert and a line parallel to the axis of rotation of the tool. From Figure 8 it will be understood that an insert having a straight cut edge 106 will make point contact with the work when the angle 112 is different from zero. The punctual contact will result in work break when the tool is translated relative to it. Known inserts include convex axial cutting edges, to effectively overcome such point contact. It is an object of the present invention to provide an improved cutting insert for milling. Still another object of the present invention is to provide a milling insert that provides a constant radial recess angle along its radial cutting edge. Another object of the present invention is to provide a milling insert wherein the chip ejection is improved. A further object of the present invention is to provide a milling insert wherein the axial cutting forces are reduced during use. Another object of the present invention is to provide a milling insert that reduces or eliminates the grooving of a work piece during cutting with the axial cutting edge. Still a further object of the present invention is to provide a milling insert having improved strength at the axial and radial cutting edges. BRIEF DESCRIPTION OF THE INVENTION This invention achieves these and other objects by providing a polygonal milling insert, comprising an upper surface, a lower surface and a plurality of lateral surfaces, extending from the lower surface to the upper surface, the intersection of each lateral surface with the upper surface forms a cutting edge. As usual, the cutting edges can be sharp or rounded, according to the proposed cutting application. The insert includes a first or radial cutting edge and a second or axial cutting edge, the radial cutting edge and the axial cutting edge extend substantially perpendicularly from each other, from a common edge. On the upper surface of the insert, and inward of the radial cutting edge is a concave conical surface, extending along the radial cutting edge between the apex portions of the upper surface, the tapered surface tapers in the direction of increasing depth of cut along the radial cutting edge. Inwardly of the axial cutting edge is a flat inclined portion of the upper surface, extending between the apex portions thereof, the inclined surface tapers in the direction away from the common edge. Inwardly of the concave conical portion and the flat inclined portion, the upper surface includes a flat region, which is gently fused with the concave conical portion, and a combined surface, which fuses the flat region smoothly with the inclined portion and the ridge common. BRIEF DESCRIPTION OF THE DRAWINGS This invention can be clearly understood by reference to the appended drawings, in which like parts are designated by like reference numerals, and in which: Figure 1 is a perspective view of a cutting insert or milling of the present invention; Figure 2 is a plan view of the milling insert of Figure 1; Figure 3 is an elevation view of Figure 2; Figure 4 is a cross-sectional view of Figure 1, taken along lines 4-4; Figure 5 is a cross-sectional view similar to Figure 4, but of an alternative embodiment of the milling or cutting insert of the present invention; and Figure 6 is a cross-sectional view similar to Figure 4, but of another alternative embodiment of the milling insert of the present invention. Figure 7 is a side view of a cutting or milling tool of known type. Figure 8 is a second side view of the cutting or milling tool of Figure 7. Figure 9 illustrates the circle circumscribed by the rotation of the tool of Figures 7 and 8. DESCRPTION OF THE PREFERRED MODALITY The modality that is described in the drawings it is one that is particularly adapted to achieve the objects of the invention. Figures 1 and 2 describe a cutting insert 2, comprising a lower surface 4 and an upper surface 6. In the embodiment of Figure 1, the lower surface 4 is flat. A plurality of side surfaces are provided, which extend from the lower surface 4 to the upper surface 6, the intersection of each side surface with the upper surface 6 forming a respective cutting edge. For example, in the preferred embodiment described in the drawings, a plurality of peripheral side surfaces 8, 10, 12, 14 are provided, which extend upwards and outwards from the lower surface 4 to the supra-eribr surface 6. side surface 8 extends upwardly and outwardly to a radial cutting edge 18, and side surface 10 extends upward and outward to radial cutting edge 22. Similarly, side surface 12 extends upwardly and outwardly. to an axial cutting edge 26, and the side surface 14 extends upwards and outwards to the axial cutting edge 30. In the preferred embodiment of Figure 1, the side surfaces 8 and 10 are each flat, for providing flat side areas, extending upwards and outwards from the bottom surface 4 to the top surface 6. In an alternative embodiment, the side surfaces 8 and 10 may each comprise more than one porc ion, including flat and curved portions, to provide a composite side surface on each such side surface. A mounting opening 32 extends through the cutting or milling insert 2, from the bottom surface 4 to the top surface 6. A mounting screw 122, such as that shown in Figure 8 typically extends through the opening 32, for mounting the cutting or milling insert 2 in the usual manner. As proposed to be mounted on a milling cutting tool, the cutting edges 18, 22, 26, and 30 of the insert 2 are active in, at most, even, that is, edges 18 and 26 will be engaged in the cutting, while the cutting edges 22 and 30 are located internally of the periphery of the cutting tool body. With the spacing of the insert, the cutting edges 22 and 30 are made active cutting edges. In the illustration of Figure 9, the angle 114 between a radius 116 of the cutting tool body, passing through a point on the radial cutting edge 108, and a tangent 118 to the surface with a recess angle of the cutting tool. The insert passing through the same point on the cutting edge 108 is known as the radial recess angle, also called the radial recess angle. A positive radial recess angle is achieved when the radius 116 gives rise to the tangent 118 in the direction of advance of the cutting edge 108. As proposed to be mounted on the body 100 of the cutting tool, the cutting edge 108 The radial is inclined at an angle 110 relative to a line parallel to the axis 102 of the tool. As a result of the angle 110 of Figure 7, the orientation of the insert in the body 100 of the cutting tool changes the ratio of the spokes of the tool body, such as the radius 116 of Figure 9, to the face with recess angle along the length of the radial cutting edge 108. Applicants have determined that in order to produce a constant radial recess angle along the length of the cutting edge 108, it is advantageous to vary the direction of the tangent to the surface with recess angle, such as the tangent 118 of Figure 9. Referring to Figures 1 and 2, the upper surface 6 of the cutting or milling insert 2 includes a first conical portion 38 and a second conical portion 40, each of which is concave relative to the upper surface. The conical portion 38 has an axis 58 of the associated cone, and narrows in the direction of the arrow 42. The conical portion 40 has an axis 56 of the associated cone, and tapers in the opposite direction, designated by the arrow 48. In the embodiment of Figure 1, the conical portions 38 and 40 are each defined by cones having a circular cross-section relative to the axes 56 and 58 of the respective cone. In an alternative mode, the conical portions 38 and 40 may be defined by cones having an elliptical cross section relative to the axes 56 and 58 of the respective cone. In accordance with the definition of radial recess angle, and considering the effects on the radial recess angle of the angle 110 of Figure 7, the conical portions 38 and 40 are designed to produce a radial recess angle substantially constant at length of the co-extensive length of the active radial cutting edge at a particular value of inclination angle 110 of Figure 7. By virtue of the concave conical surface, the effective volume of material of the body of the insert that is directly behind the edge Radial cutting is increased in the direction of the increasing cutting depth of the milling cutting tool. Hence, the increasing resistance of the edge is obtained at sites that are along the radial cutting edge associated with the deepening depth of cut. Additionally, the constant radial recess angle along the length of the radial cutting edge results in uniformity of the cutting action, i.e., the angle of the shear stress along the length is constant, and hence, the Shear stress is constant along the cutting edge. In Figure 7, the angle 113 between a vertical 109 passing through a point on the axial cutting edge 106 and a tangent 111 to the surface with recess angle at the same point on the cutting edge 106 is the angle of axial recess, also known as axial recess angle. A positive axial recess angle is achieved when the vertical 109 gives rise to the tangent 111 in the direction of advance of the cutting edge 106. The upper surface 6 includes inclined portions 72 and 74, each of which extends or slopes downwards towards the lower surface 4, as described in Figure 1. The inclined portion 72 extends from the second or axial cutting edge 26 towards the first common edge 44, tapering in the direction away from the common edge 44. An opposite inclined portion 74 extends from the fourth or axial cutting edge 30 towards the second common edge 50, tapering from the common edge 50. The surfaces 72 and 74 serve to reducing the axial cutting forces, increasing the effective axial recess angle at the active edge of the cutting edges 26 and 30 when the insert is mounted on a milling cutting tool, such as that shown in Figures 7 and 8. The narrowing of the inclined portions 72 and 74 in the direction away from the respective common edges 44 and 50 increases the volume of the body of the insert adjacent to the narrow ends of the conical portions 38 and 4. 0 serving to provide additional support, to reinforce the cutting edges 18 and 22 at the ends associated with the greatest depth of cut. The upper surface 6 of the cutting or milling insert 2 also includes a first flat region 60, which extends between and fuses with the first conical portion 38, the second concave conical portion 40, and the inclined portion 72. In a similar manner , a second planar region 66 that is at the opposite end of the cutting or milling insert 2 extends between and fuses with the second concave conical portion 40, the first concave conical portion 38 and the inclined portion 74. By allowing the segments 60 and 66 to merge or merge with the adjacent concave conical portions, without any abrupt change in the contour of the surface, the segments 60 and 66 serve to improve the ejection of chips during the milling operation. The upper surface 6 includes a first combined surface 76, which fuses the inclined portion 72 with the concave conical portion 38 on the common edge 44, and also fuses the concave conical portion 40 with the edge 78 of the upper surface 6. , as described in Figures 1 and 2. A second combined surface 80 is provided, which fuses the inclined portion 74 with the concave conical portion 40 on the common ridge 50, and also fuses the concave conical portion 38 with the ridge 82. of the upper surface 6. The combined surfaces 76 and 80 gently and gradually fuse all the surfaces adjacent to such combined surfaces, to facilitate ejection of the chip. In one embodiment, relatively narrow contact areas are provided, adjacent to at least two cutting edges. For example, in the embodiment described in Figures 1 to 4, all upper cutting edges 18, 22, 26, 30, comprise a contact area 84. Although not necessary, such contact area may be parallel to the surface lower 4, as shown in Figure 4. In an alternative embodiment, shown in Figure 5, a contact area 86 can be provided, which slopes down relative to the lower surface 4, and in this configuration is 11a-m a negative contact area-T. An inclination angle 88 of the negative contact area-T is conveniently defined, relative to a plane transverse to the axis of the mounting opening 32, and has a value in the range of 5o to 20 °. By providing a contact area around the periphery of the cutting or milling insert, the upper cutting edge will be reinforced. In another embodiment, the narrow contact area can be eliminated, and the cutting edge can be in the configuration of a sharp edge 89, as shown in Figure 6. To provide a polished finish on the workpiece, the edges axially cutting edges 26, 30 are advantageously curved outwards, relative to the center of the upper surface 6, in the direction of the respective arrows 90, 92. The curve of the axial cutting edges 26, 30 is effective, within a range of values of the angle 112 of Figure 8, to rub or sweep an area of the material of the work piece during cutting, to eliminate the grooving by punctual contact, and with this, improving the workpiece's terminal. The embodiments described herein are but a few of several that use this invention, and are set forth herein by way of illustration, but not of limitation. It is apparent that many other modalities can be made, which will be readily apparent to those skilled in the art, without departing materially from the spirit and scope of this invention.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (19)

1. CLAIMS 1. A cutting or milling insert, characterized in that it comprises: a polygonal body, having an upper surface, a lower surface, and a plurality of lateral surfaces, extending between the upper surface and the lower surface, the lateral surfaces they lean outward from the lower surface, for their intersection with the upper surface; a first radial cutting edge, formed at the intersection of a lateral surface with the upper surface, the first radial cutting edge extends between the edges of the upper surface, wherein the upper surface comprises a first concave conical portion, adjacent to the First the cutting edge, the first concave conical portion extends between the edge portions of the insert, and tapers in a direction associated with the increasing depth of cut, along the first radial cutting edge, and is defined for achieving a constant positive radial recess angle along the length of the first radial cutting edge, at the inclination angle thereof, when the insert is to be mounted on the body of a cutting tool, with the first radial cutting edge positioned as the active radial cutting edge. The cutting or milling insert according to claim 1, characterized in that a narrow contact area is interposed between the radial cutting edge and the concave conical portion. 3. The cutting or milling insert according to claim 2, characterized in that the upper and lower surfaces are quadrilateral. The cutting or milling insert according to claim 3, characterized in that it additionally comprises a first axial cutting edge, which extends substantially perpendicularly from a common edge with the first radial cutting edge. The cutting or milling insert according to claim 4, characterized in that the upper surface further comprises a first inclined portion, adjacent to the first axial cutting edge, the first inclined portion sloping downwardly from the first edge of the cutting edge. axial cut, extends between the edge portions of the insert, and tapers in the direction away from the first common edge, the inclined portion defines a positive axial recess angle when the insert is proposed to be mounted on the body of a tool of cutting, with the first axial cutting edge placed as an active axial cutting edge. The insert according to claim 5, characterized in that it additionally comprises a mounting opening, which extends through the cutting or milling insert, from the lower surface to the upper surface. 7. The insert in accordance with the rei indication 6, characterized in that it additionally comprises a first planar region, adjacent to the first concave conical surface, and inwardly of the first inclined region, extending to the mounting opening, the first planar region it slopes downwardly from the narrower end of the concave conical portion, in the transverse direction thereof, and slopes downwardly along the concave conical portion, in the opposite direction of its narrowing. The insert according to claim 6, characterized in that it additionally comprises a first combined surface, which fuses smoothly with the planar region, the first concave conical portion, the first in-clumped portion, and the edges of the upper surface adjacent to it. the first portion inclined. The insert according to claim 5, characterized in that it additionally comprises a second radial cutting edge, and a second axial cutting edge, the second radial cutting edge and the second axial cutting edge extend from a second one. common edge, diagonally opposite the first common edge, and are substantially perpendicular to each other, wherein the upper surface further comprises: a second concave conical portion, adjacent to the second radial cutting edge, the second concave conical portion extends between the edge portions of the insert, and tapers in the direction away from the second common edge , and is defined to achieve a constant positive radial recess angle along the length of the second radial cutting edge, at the inclination angle thereof, when the insert is proposed to be mounted on the body of a cutting tool , with the second radial cutting edge as an active radial cutting edge; a second inclined portion, adjacent to the second axial cutting edge, the second inclined portion slopes downwardly from the second axial cutting edge, and narrows in the away direction from the second common edge, and is defined to achieve an angle of positive axial recess when the insert is mounted on the body of a cutting tool, with the second axial cutting edge positioned as an active axial cutting edge; and a second planar region, adjacent to the second concave conical portion, and internally of the second in-clumped portion, and extending to the mounting opening, the second planar region slopes downward from the narrower end of the second portion. inclined portion, towards the second common edge, and upwards from the second common edge, in the direction of the narrowing of the second concave concave portion 10. The cutting or milling insert according to claim 9, characterized in that a second combined surface is smoothly fused with the second concave conical portion, the second inclined portion, the second flat portion, and the edges of the insert adjacent to the second inclined portion . The cutting or milling insert according to claim 9, characterized in that the first and second cutting edges are bent outwards relative to the upper surface. The cutting or milling insert according to claim 9, characterized in that the cones defining the first and second concave conical portions are circular 13. The cutting or milling insert according to claim 9, characterized in that the cones defining the first and second concave conical portions are elliptical. 14. A milling cutting tool, characterized in that it comprises: a body of the cutting tool; and a cutting insert, comprising a polygonal body, having an upper surface, a lower surface and a plurality of side surfaces, extending between the upper surface and the lower surface, the lateral surfaces sloping outwardly from the surface lower to its intersection with the upper surface; a first cutting edge and a second cutting edge, each cutting edge is formed at the intersection of a lateral surface with the upper surface, the first and second cutting edges extend from a common first edge of the insert, and are substantially perpendicular to each other, wherein the upper surface comprises a first concave conical portion, adjacent to the first cutting edge, the first concave conical portion extends between the edge portions of the insert, and tapers in the direction away from the first common edge, and is defined to achieve a constant positive radial recess angle along the length of the first cutting edge, at the angle of inclination thereof, when the insert is proposed to be mounted on the body of the tool of cutting with the first cutting edge positioned as an active radial cutting edge, a first inclined portion adjacent to the second cutting edge, the first The inclined portion slopes downwardly from the second cutting edge, extends between the edge portions of the insert, and narrows in the direction of the first common edge, and is defined to achieve a positive axial recess angle. when the insert is proposed to be mounted on the body of the cutting tool with the second cutting edge positioned as an active axial cutting edge. The milling cutting tool according to claim 14, characterized in that the insert further comprises a mounting opening, extending through the cutting or milling insert, from the lower surface to the upper surface, and the tool milling cutter additionally comprises a mounting screw. 16. The milling cutting tool according to claim 15, characterized in that the insert further comprises: a first flat region, adjacent to the first concave conical surface, and internally of the first inclined portion, extending to the mounting opening, the first planar region slopes downward from the narrowest end of the portion inclined towards the first common edge, and upwardly from the first common edge, in the direction of the constriction of the first concave conical portion, and a first combined surface, which merges smoothly with the flat region and the first inclined portion and, at the common edge, with the first concave conical portion and the first inclined portion. The milling cutting tool according to claim 14, characterized in that the insert further comprises a narrow contact area, interposed between the first and second cutting edges and the concave conical portion and the inclined portion, respectively. The milling cutting tool according to claim 14, characterized in that the insert further comprises a third and a fourth cutting edge, extending from a second common edge, diagonally opposite the first common edge, and are substantially perpendicular to each other, wherein the upper surface further comprises a second concave conical portion, adjacent the third cutting edge, the second concave conical portion extends between the edge portions of the insert, and tapers in the remote direction from the second common edge, and is defined to achieve a constant positive radial recess angle along the length of the third cutting edge, at the angle of inclination thereof, when the insert is proposed to be mounted on the body of the cutting tool with the third cutting edge placed as an active radial cutting edge, a second inclined portion, adjacent At the fourth cutting edge, the second inclined portion slopes down from the fourth cutting edge, and tapers in the away direction from the second common edge, and is defined to achieve a positive axial recess angle when the insert is It proposes to be mounted on the body of the cutting tool with the fourth cutting edge positioned as an active axial cutting edge, and a second flat region, adjacent to the second concave conical portion, and internally of the second inclined portion. , which extends to the mounting aperture, the second planar region slopes downward from the narrowest end of the second inclined portion, toward the common edge, and upwardly from the second common edge, in the direction of the constriction of the second concave conical portion. The cutting or milling insert according to claim 18, characterized in that the second and the fourth cutting edges are curved outwards, with respect to the upper surface.