CUTTING INSERT AND TOOL BODY FOR A MILLING TOOL

Abstract

A cutting insert for a milling tool including an upper side having a central surface, a lower side, a peripheral side surface, and a cutting edge formed between the upper side and the peripheral side surface. The cutting edge having a positively inclined main cutting edge projecting at least partly above the central surface. The upper side includes a rake surface extending inside of and along the at least one cutting edge, sloping downward toward the central surface. A plateau, elevated with respect to the central surface and extending along the main cutting edge, is formed inside the rake surface. A transition between the rake surface and the plateau extends at an angle .sub.2 with respect to an upper extension plane, wherein .sub.2>0.

Claims

1. A cutting insert for a milling tool, comprising: an upper side defining an upper extension plane and including a central surface; a lower side opposite to the upper side defining a lower extension plane, wherein a centre axis extends perpendicularly through the upper and lower extension planes; a peripheral side surface extending between the upper side and the lower side; at least one cutting edge formed in a transition between the upper side and the peripheral side surface, wherein the at least one cutting edge includes a main cutting edge formed in a transition between the upper side and a main part of the peripheral side surface, wherein at least a projecting major portion of the main cutting edge projects above the central surface, wherein the projecting major portion of the main cutting edge is at least in part positively inclined with respect to the upper extension plane and creates forms an angle .sub.1 with the upper extension plane as seen in a direction orthogonal to the main part of the peripheral side surface, wherein the upper side includes at least one rake surface extending inside of and along the at least one cutting edge, wherein the rake surface slopes downward toward the central surface; and a plateau extending at least along the projecting major portion of the main cutting edge formed inside of the at least one rake surface, wherein the plateau is elevated with respect to the central surface, and wherein, as seen in the direction orthogonal to the main part of the peripheral side surface, a transition between the rake surface and the plateau extends at an angle .sub.2 with respect to the upper extension plane, wherein .sub.2>0.

2. The cutting insert according to claim 1, wherein as seen in a top view, the transition between the rake surface and the plateau extends at an angle with respect to the main cutting edge, wherein 55.

3. The cutting insert according to claim 1, wherein the rake surface and/or the plateau are planar surfaces at least along the projecting major portion of the main cutting edge or at least along a part of the projecting major portion of the main cutting edge.

4. The cutting insert according to claim 1, wherein the transition between the rake surface and the plateau extends in parallel with at least the projecting major portion of the main cutting edge or at least with a part of the projecting major portion of the main cutting edge.

5. The cutting insert according to claim 1, wherein a width w.sub.p of the plateau is related to a width w.sub.r of the rake surface as 0.5 w.sub.rw.sub.p2 w.sub.r.

6. The cutting insert according to claim 2, wherein a width w.sub.p of the plateau is the same along at least the projecting major portion of the main cutting edge or at least along a part of the projecting major portion of the main cutting edge, or wherein the width w.sub.p of the plateau does not differ by more than 20% along at least the projecting major portion of the main cutting edge or at least along a part of the projecting major portion of the main cutting edge.

7. The cutting insert according to claim 1, wherein the plateau forms a plane that extends in parallel with the main cutting edge, or at an angle of no more than 5 with respect to the main cutting edge.

8. The cutting insert according to claim 1, wherein, as seen in a vertical section taken perpendicularly to the main cutting edge, the plateau is parallel to the upper extension plane or has an angle of inclination of no more than 5 with respect to the upper extension plane.

9. The cutting insert according to claim 1, wherein a shortest distance between the main cutting edge and the plateau is the same along at least the projecting major portion of the main cutting edge or at least along a part of the projecting major portion of the main cutting edge.

10. The cutting insert according to claim 1, wherein a primary land is provided between at least a part of the at least one cutting edge and the rake surface.

11. The cutting insert according to claim 1, wherein the plateau extends all the way along the at least one cutting edge.

12. The cutting insert according to claim 1, wherein the upper side further comprises a transition surface connecting the plateau and the central surface, wherein the transition surface is positively inclined as seen in a vertical section taken perpendicularly to the main cutting edge.

13. The cutting insert according to claim 1, wherein the cutting insert is indexable with at least two or three or four or five or six or seven or eight identical and alternately usable main cutting edges formed in the transition between the upper side and the peripheral side surface.

14. The cutting insert according to claim 1, wherein the cutting insert is double-sided with the lower side being identical to the upper side, at least one cutting edge being formed in a transition between the lower side and the peripheral side surface.

15. A milling tool comprising: a tool body provided with an insert seat for receiving a cutting insert; and a cutting insert according to claim 1 arranged in the insert seat.

16. A tool body for a milling tool, the tool body having a central rotation axis around which the tool body is rotatable in a direction of rotation, wherein the tool body comprises a front end and a rear end between which an envelope surface extends; and at least one insert seat being formed in a transition between the front end and the envelope surface, wherein said insert seat includes a bottom contact surface configured to support the central surface of the lower side of the double-sided cutting insert according to claim 14, wherein the insert seat includes a recess extending between the bottom contact surface and the envelope surface, said recess being configured to accommodate the plateau of the lower side of the double-sided cutting insert.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Embodiments of the invention will in the following be described by means of example with reference to the appended drawings, in which:

[0040] FIG. 1 shows a perspective view of a cutting insert according to a first embodiment of the invention,

[0041] FIG. 2 shows a side view of the cutting insert in FIG. 1,

[0042] FIG. 3 shows a top view of the cutting insert in FIG. 1,

[0043] FIG. 4 shows a section along the line IV-IV in FIG. 3,

[0044] FIG. 5a-c show sections along the lines Va-Va, Vb-Vb, and Vc-Vc, respectively,

[0045] FIG. 6 shows a perspective view of a cutting insert according to a second embodiment of the invention,

[0046] FIG. 7 shows a side view of the cutting insert in FIG. 6,

[0047] FIG. 8 shows a top view of the cutting insert in FIG. 6,

[0048] FIG. 9 shows a section along the line IX-IX in FIG. 6,

[0049] FIG. 10 shows a perspective view of a milling tool according to an embodiment of the invention,

[0050] FIG. 11 shows a side view of the milling tool in FIG. 10,

[0051] FIG. 12 shows a detail of the milling tool in FIG. 10, and

[0052] FIG. 13 shows a section along the line XIII-XIII in FIG. 12.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0053] A cutting insert 1 according to a first embodiment of the invention is shown in FIGS. 1-5c and a cutting insert according to a second embodiment is shown in FIGS. 6-9. The cutting insert 1 according to the first embodiment is intended for use in face milling operations at an entering angle of 45 as shown in FIG. 11, wherein the cutting insert 1 according to the first embodiment is mounted in a tool body 101 of a milling tool 100. The cutting insert 1 according to the second embodiment is instead configured for use in a face milling tool 100 at an entering angle of 68. The cutting insert 1 has in both embodiments a square basic shape and is double-sided with an identical upper side 2 and lower side 3, defining an upper extension plane P.sub.U and a lower extension plane P.sub.L, respectively. A centre axis C.sub.1 extends perpendicularly through the upper and lower extension planes P.sub.U, P.sub.L, and a central through hole 4 for screw mounting the cutting insert 1 to a milling tool extends around the centre axis C.sub.1. A peripheral side surface 5, parallel with the centre axis C.sub.1, extends between the upper side 2 and the lower side 3. The peripheral side surface 5 constitutes a clearance surface when the cutting insert 1 is used in a milling operation.

[0054] Four identical cutting edges 6a, 6b, 6c, 6d are formed in a transition between the upper side 2 and the peripheral side surface 5, and four identical cutting edges 6 are formed in a transition between the lower side 3 and the peripheral side surface 5, so that the cutting insert 1 is indexable with a total of eight index positions. Since the upper side 2 and the lower side 3 are identical, only the upper side 2 and the cutting edges 6a, 6b, 6c, 6d extending around the upper side 2 will be described in detail.

[0055] Each cutting edge 6a, 6b, 6c, 6d comprises a chip-removing main cutting edge 7a, 7b, 7c, 7d and a surface-wiping secondary cutting edge 8a, 8b, 8c, 8d. The main cutting edges 7a, 7b, 7c, 7d are formed in a transition between the upper side 2 and main parts 25 of the side surface. At its first end, the main cutting edge 7a of a first one 6a of the cutting edges is connected to the surface-wiping secondary cutting edge 8a belonging to the same first cutting edge 6a, via an active corner cutting edge 17a. At its second end, opposite to the first end, the same main cutting edge 7a is connected to the surface-wiping secondary cutting edge 8b belonging to the second cutting edge 6b, via an inactive corner cutting edge 18b. Since the cutting edges 6a, 6b, 6c, 6d are identical, the remaining cutting edges 6b, 6c, 6d are correspondingly connected. Therefore, reference will in the following mainly be made to the first cutting edge 6a.

[0056] In the first embodiment shown in FIGS. 1-5c, the surface-wiping secondary cutting edge 8a is formed at an angle of 45 with respect to the main cutting edge 7a as seen in a top view. In the second embodiment shown in FIGS. 6-9, the surface-wiping secondary cutting edge 8a is formed at an angle of 68 with respect to the main cutting edge 7a as seen in a top view.

[0057] The main cutting edge 7a is in both embodiments positively inclined with an angle .sub.1 of 10 with respect to the upper extension plane P.sub.U as seen in a side view, and thus slopes downward in a direction from the surface-wiping secondary cutting edge 8. The highest point of the cutting edge 6a is located on the active corner cutting edge 17a. In the shown embodiments, the entire main cutting edge 7a projects above a central surface 9 of the upper side 2, extending around the central through hole 4. The central surface 9 extends in parallel with, and is recessed with respect to, the upper extension plane P.sub.U.

[0058] The upper side 2 comprises a rake surface 10 extending inside of and along the cutting edges 6a, 6b, 6c, 6d. The rake surface 10 slopes downward toward the central surface 9, i.e. it has a positive inclination with respect to the upper extension plane P.sub.U. In both embodiments, a main rake surface portion 11 of the rake surface 10, extending along the main cutting edge 7a, is inclined with an angle of inclination .sub.1 of 25 with respect to the upper extension plane P.sub.U, as shown in FIGS. 4 and 9, respectively. A secondary rake surface portion 12, extending inside the surface-wiping secondary cutting edge 8c, extends at a slightly smaller angle of inclination .sub.2. In the first embodiment, as shown in FIG. 5c, the angle of inclination .sub.2 is 23, while in the second embodiment, the angle of inclination .sub.2 (not shown for this embodiment) is 21.

[0059] The upper side 2 further comprises a plateau 13 extending inside of the rake surface 10 and along the cutting edges 6a, 6b, 6c, 6d. The plateau 13 is elevated with respect to the central surface 9. As seen in a top view, and also in a sectional side view such as shown in FIGS. 4 and 9, respectively, a transition 14 between the rake surface 10 and the plateau 13 extends at an angle =0 with respect to the cutting edge, i.e. in parallel with the cutting edge. The transition 14 between the rake surface 10 and the plateau 13 is herein a radial transition with a relatively small radius of curvature, so that the plateau 13 and the rake surface 10 form separate planar surfaces. Thus, along the main cutting edge 7a, the plateau 13 and the transition 14 extend in parallel with the main cutting edge 7a. As seen in a side view, as shown in FIGS. 2 and 7, the plateau 13 and the transition 14 extend at an angle of inclination .sub.2 with respect to the upper extension plane P.sub.U corresponding to the angle of inclination .sub.1 of the main cutting edge 7a. The hidden transition 14 and the hidden plateau 13, inside the main cutting edge 7a, are in the side views marked with dashed lines. As seen in vertical sections taken perpendicularly to the cutting edge 6c, the plateau 13 is essentially parallel with the upper extension plane P.sub.U along the main cutting edge 7c and the surface-wiping secondary cutting edge 8c. This can be seen in the sectional views in FIGS. 4, 5a, 5b and 5c for the cutting insert 1 according to the first embodiment, and in FIG. 9 for the cutting insert 1 according to the second embodiment.

[0060] Between the rake surface 10 and the cutting edges 6a, 6b, 6c, 6d, a primary land 15 is provided. In the first embodiment, the primary land 15 extends in parallel with the upper extension plane P.sub.U, i.e. at a neutral angle of inclination, along the main cutting edge 7a, 7c and the secondary surface-wiping cutting edge 8a, 8c as shown in the sectional views in FIGS. 4-5c. In the second embodiment, the angle of inclination of the primary land 15 is neutral inside the main cutting edge 7a, but is negative with an angle of 5 inside the secondary surface-wiping cutting edge 8a.

[0061] A width w.sub.p of the plateau 13 is in the shown embodiments the same or essentially the same along the entire plateau 13. It is approximately equal to a width w.sub.r of the rake surface 10, wherein the widths are measured as projected onto the upper extension plane P.sub.U, i.e. in a top view of the cutting insert 1. A width of the primary land 15 in the shown embodiments is significantly smaller than the widths of the rake surface 10 and the plateau 13.

[0062] A shortest distance between the plateau 13 and the cutting edge 6a is in the shown embodiments approximately the same along the entire plateau 13, and it is identical along the positively inclined part of the main cutting edge 7a. The main cutting edge 7a has a negatively inclined part which extends from the lowest point of the main cutting edge, when seen in FIGS. 2 and 7, toward the inactive corner cutting edge 18b. By the lowest point of the main cutting edge, the point which is closest to the lower extension plane P.sub.L is intended.

[0063] In the shown embodiments, the plateau 13 extends along the entire cutting edges 6a, 6b, 6c, 6d. However, this is not necessary. Instead the plateau may be formed such that it extends merely inside of the main cutting edge, or inside a projecting part of the main cutting edge. Moreover, the plateau may have a small variation in width along the plateau, or it may extend at a small angle with respect to the main cutting edge, preferably of no more than 5. The plateau may also form a planar surface that extends at an angle, preferably of no more than 5, with respect to the central surface and/or to the upper extension plane, as seen in a vertical section perpendicular to the main cutting edge. In other embodiments, a gradual transition may be provided between the rake surface and the plateau, such that the plateau does not form a planar surface.

[0064] The upper side 2 further comprises a transition surface 16 connecting the plateau 13 and the central surface 9. The transition surface 16 is positively inclined as seen in a vertical section taken perpendicularly to the main cutting edge 7a.

[0065] A milling tool 100 configured for face milling is shown in FIGS. 10-13. The milling tool 100 comprises a tool body 101 having a central rotation axis C.sub.2 around which the tool body is rotatable in a direction of rotation R. The tool body 101 has a front end 102 and a rear end 103 between which an envelope surface 104 extends. The rear end is configured for mounting the tool body 101 to e.g. a rotating spindle of a machine via e.g. a tool holder (not shown). Six insert seats 105, in which cutting inserts 1 according to the first embodiment described above are mounted by means of screws 200, are formed in a transition between the front end 102 and the envelope surface 104. A chip pocket 106 is provided in front of each insert seat in the direction of rotation R. Each insert seat 105 comprises a bottom contact surface 107 configured to support the central surface 9 of the lower side 3 of the double-sided cutting insert 1. The insert seat 105 further comprises a recess 108 extending between the bottom contact surface 107 and the envelope surface 104. The recess 108 is configured to accommodate the plateau 13 of the lower side 3 of the double-sided cutting insert 1. In the shown embodiment, with square cutting inserts 1, the tool body 101 has a first and a second peripheral surface 109, 110, formed at approximately right angles with respect to one another and at about 45 with respect to the centre axis C.sub.2, extending behind the cutting insert 1 in the direction of rotation R and forming a continuation of the main part 25 of the peripheral side surface 5 of the cutting insert 1. The recess 108 is in this embodiment formed on one hand between the bottom contact surface 107 and the first peripheral surface 109, and on the other hand between the bottom contact surface 107 and the second peripheral surface 110.

[0066] During machining of a workpiece, the active cutting edge 6a of the cutting insert 1, and in particular the main cutting edge 7a, removes material from the workpiece such that a chip is formed. The chip travels over the rake surface 10 and is deflected by the plateau 13. Since the plateau 13 extends in parallel with the cutting edge 6a, the conditions for chip forming are similar along the main cutting edge 7a, i.e. for varying cutting depths.

[0067] The invention is of course not limited to the embodiments disclosed, but may be varied and modified within the scope of the following claims. For example, the shape of the cutting inserts may be varied as well as the number of cutting inserts used in the milling tool. For example, the cutting inserts may be circular, octagonal, hexagonal, triangular, trigonal, heptagonal, square, etc. Instead of screws, other fastening members can be used for mounting the cutting inserts in the tool body, such as e.g. clamping members.