WO2004062840A1

WO2004062840A1 - Cutting insert and milling cutter

Info

Publication number: WO2004062840A1
Application number: PCT/IL2003/001068
Authority: WO
Inventors: Rafael Morgulis; Anton Babushkin
Original assignee: Iscar Ltd
Current assignee: Iscar Ltd
Priority date: 2003-01-14
Filing date: 2003-12-15
Publication date: 2004-07-29
Anticipated expiration: 2005-07-14
Also published as: IL153938A0; AU2003288492A1

Abstract

A cutting insert (10) for a milling cutter having the cutting advantages of a large diameter circular cutting insert whilst having the compactness of a small diameter circular cutting insert. The cutting edge comprises an integral number of greater than two identical circular sections (20), each circular section lying on a circle of a first diameter (D1), wherein in a top view the cutting insert has an inscribed circle of a second diameter (D2) smaller than the first diameter (D1).

Description

CUTTING INSERT AND MILLING CUTTER

FIELD OF THE INVENTION

The present invention relates to a cutting insert and a milling cutter for metal cutting operations capable of performing both ramp down and high feed rate face milling operations.

BACKGROUND OF THE INVENTION

Such milling cutters typically comprise a cylindrical cutter body having a plurality of cutting inserts secured in circumferentially spaced insert pockets disposed about the cutting end of the milling cutter. Each cutting insert includes at least one cutting edge. The shape of the cutting edge not only influences the performance of the cutting insert but also the feed rate of the milling cutter. For example, if round (button) inserts are used the feed rate can be increased, for a given smoothness of the milled surface, by increasing the radius of curvature of the cutting edge. However, there is clearly a practical limit to the desirable diameter of cutting inserts used in a milling cutter.

In US 6,413,023 Bl there is disclosed a generally rectangular indexable cutting insert having two arced main cutting edge sections, each one connected to a straight-line section. In order to increase the number of cutting edges, the total number edges has to be reduced do to the constraint that the outer peripheral cutting edge is designed to be back tapered with respect to the center axis of the cutting tool. Hence, the cutting insert disclosed in US '023 with three arced main cutting edge sections, each one connected to a straight line, is generally triangular in shape. A cutting insert with more than three cutting edges cannot be designed in accordance with the teachings of US '023. Similar cutting inserts are disclosed in DE 100 52 963 Al, with the same limitation in the number of cutting edges.

It is an object of the present invention to provide a cutting insert and a milling cutter for high feed rate metal cutting operations that significantly reduce or overcome the aforementioned disadvantages.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a cutting insert comprising a top surface a bottom surface and a peripheral side surface extending therebetween, the top and peripheral side surfaces intersecting at a cutting edge comprising an integral number of greater than two identical circular sections, each circular section lying on a circle having a first diameter, wherein in a top view of the cutting insert the top surface has an inscribed circle having a second diameter smaller than the first diameter. Typically, the peripheral side surface comprises a relief surface adjacent the cutting edge, an abutment surface adjacent the bottom surface and an intermediate surface extending between the relief and abutment surfaces.

Further typically, the abutment surface comprises an integral number of greater than two identical abutment sections. If desired, the relief surface is generally conical in shape extending downwards and inwards from the cutting edge to the intermediate surface. Further if desired, each abutment section is flat.

In accordance with a specific application of the present invention, the cutting edge comprises eight circular sections. If desired, adjacent circular sections are separated by a straight-edge section.

Typically, the straight-edge section has a length in the range of 1 to 2 millimeters. There is also provided in accordance with the present invention a milling cutter comprising a cutter body provided with a plurality of cutting inserts in accordance with the present invention retained in insert pockets; each insert pocket comprising a base surface and two side surfaces extending generally uprightly from the base surface, each side surface being provided with a support surface; wherein the insert bottom surface abuts the base surface, a first support surface abuts a first abutment section and a second support surface abuts a second abutment section.

In accordance with a specific application of the present invention, the first and second abutment sections are perpendicular to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which: Fig. 1 is a perspective view of a cutting insert in accordance with a first embodiment of the present invention;

Fig. 2 is a side view of the cutting insert shown in Fig. 1 ; Fig. 3 is a top view of the cutting insert shown in Fig. 1;

Fig. 4 is a side view of a milling cutter in accordance with the present invention; Fig. 5 is a perspective view of an insert pocket of the milling cutter shown in Fig.

4; and

Fig. 6 is a top view of a cutting insert in accordance with a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

Attention is first drawn to Figs. 1 to 3 of the drawings, showing a cutting insert 10 in accordance with a first embodiment of the present invention. The cutting insert 10 comprises a top surface 12 a bottom surface 14 and a peripheral side surface 16 extending between the top and bottom surfaces 12, 14. The cutting insert 10 is typically manufactured by form-pressing and sintering carbide powders, however, injection molding techniques can also be used. The top and peripheral side surfaces 12, 16 intersect at a cutting edge 18 comprising eight identical circular sections 20 and straight-edge sections 22 separating adjacent circular sections 20. Each circular section 20 forms a cutting edge section and is part of a circle Cl having a first diameter Dl. A through bore 24 extends through the cutting insert 10 between the top and bottom surface 12, 14. A rake surface 26 extends from adjacent the cutting edge 18 towards the through bore 24. The particular form of the rake surface 26 and the possible provision of chip breakers is a matter of technical design and does not constitute part of the present invention.

As can be seen in Fig. 3, in a top view of the cutting insert 10, the top surface 12 is generally circular in shape and has an inscribed circle C2 having a second diameter D2 smaller than the first diameter Dl. As will be described in greater detail below, the straight-edge sections 22 are used as wipers and typically have a length in the range of 1 to 2 millimeters, independent of the magnitudes of the first and second diameters Dl, D2. The length of each circular segment 20 is greater than the length of each straight-edge section 22. In accordance with a specific application of the present invention, the first diameter Dl has a value of 30 millimeters and the second diameter D2 has a value of 20 millimeters. In accordance with this specific application, the cutting insert 10 has, in a top view, the overall appearance of a round cutting insert having a radius of 10 millimeters, whereas each cutting edge circular section 20 has a radius of curvature of 15 millimeters. Therefore, the cutting insert 10 in accordance with the present invention has the cutting advantages of a large diameter circular cutting insert whilst having the compactness of a small diameter circular cutting insert.

The peripheral side surface 16 comprises three surface portions 28, 30, 32. An upper surface portion 28 adjacent the cutting edge forming a relief surface, a lower surface portion 30 adjacent the bottom surface forming an abutment surface and an intermediate surface portion 32 extending between the upper and lower surface portions 28, 30. The relief surface 28 is generally conical in shape extending downwards and inwards from the cutting edge 18 to the intermediate surface portion 32. The abutment surface 30 comprises eight identical flat abutment sections 34. A milling cutter 36 for retaining cutting inserts 10 in accordance with the present invention is shown in Fig. 4. The milling cutter 36 has an axis of rotation A and comprises a cutter body 38 having a plurality insert pockets 40 in which cutting inserts 10 in accordance with the first embodiment of the present invention are secured by means of clamping screws 42. Each cutting insert 10 has an operative wiper 22' located between two operative cutting edge sections 20', 20" of the cutting edge. A first operative cutting edge section 20' for face milling operations and a second operative cutting edge section 20" for ramp down operations. The operative wipers 22' of all the cutting inserts 10 retained in the milling cutter 36 are located in an end-face plane P of the milling cutter 36. The end-face plane P is perpendicular to the axis of rotation A.

Each insert pocket 40 comprises a base surface 44 and two side surfaces 46, 48 extending generally uprightly from the base surface 44. The base surface 44 is provided with a threaded bore 50 for receiving the clamping screw 42 and each side surface 46, 48 is provided with a support surface 52, 54 for supporting the cutting insert 10. When the cutting insert 10 is clamped in the insert pocket 40 with the clamping screw 42 received in the through bore 24 and screwed into the threaded bore 50, the bottom surface 14 of the cutting insert 10 abuts the base surface 44, a first operative abutment section 34' of the cutting insert 10 abuts a first support surface 52 of the insert pocket 40 and a second operative abutment section 34" of the cutting insert 10 abuts a second support surface 54 of the insert pocket 40. The first and second support surfaces 52, 54 of the insert pocket are perpendicular to each other and consequently, the first and second operative abutment sections 34', 34" are also perpendicular to each other. When either of the operative cutting edges 20', 20" or the operative wiper 22' become dull the clamping screw 42 can be loosened and the cutting insert 10 can be indexed into a new position by rotation of the cutting insert 10 about the clamping screw 42. In Fig. 3 the end-face plane P of the milling cutter is shown. Also shown, in dashed lines, is an outline of the abutment surface 30 and the operative abutment sections 34', 34" of the cutting insert 10. The circle Cl associated with the operative cutting edge section 20' for milling operations is also shown.

A cutting insert 56 in accordance with a second embodiment of the present invention is shown in Fig. 6. In accordance with the second embodiment the cutting edge 18 comprises eight identical circular sections 20. The cutting insert 56 in accordance with the second embodiment has no straight-edge sections separating adjacent circular sections 20. In other details, such as the structure of the peripheral side surface 16, the cutting insert 56 in accordance with the second embodiment is identical to the cutting insert 10 in accordance with the first embodiment. Fig. 6 also shows the orientation of the cutting insert 56 in accordance with the second embodiment relative to the end-face plane P, when the cutting insert 56 is retained in an insert pocket 40 of the milling cutter 36. A small end section of the operative cutting edge 20' for face milling operations is located substantially in the end-face plane P and forms a wiper 58 of the operative cutting edge 20'. Also shown, in dashed lines, is the outline of the abutment surface 30 and the operative abutment sections 34', 34" of the cutting insert 56. Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the scope of the invention as hereinafter claimed. In particular, the abutment surface of the cutting insert and the support surfaces of the insert pocket can be of any convenient shape that will on the one hand maintain the cutting insert in position in the insert pocket and in the other hand will allow for indexing the cutting insert into a new position when required.

Claims

CLAIMS:

1. A cutting insert comprising a top surface, a bottom surface and a peripheral side surface extending therebetween, the top and peripheral side surfaces intersecting at a cutting edge comprising an integral number of greater than two identical circular sections, each circular section lying on a circle having a first diameter, wherein in a top view of the cutting insert the top surface has an inscribed circle having a second diameter smaller than the first diameter.

2. The cutting insert according to claim 1, wherein the peripheral side surface comprises a relief surface adjacent the cutting edge, an abutment surface adjacent the bottom surface and an intermediate surface extending between the relief and abutment surfaces.

3. The cutting insert according to claim 2, wherein the abutment surface comprises an integral number of greater than two identical abutment sections.

4. The cutting insert according to claim 2, wherein the relief surface is generally conical in shape extending downwards and inwards from the cutting edge to the intermediate surface.

5. The cutting insert according to claim 3, wherein each abutment section is flat.

6. The cutting insert according to claim 1, wherein the cutting edge comprises eight circular sections.

7. The cutting insert according to claim 1, wherein adjacent circular sections are separated by a straight-edge section.

8. The cutting insert according to claim 7, wherein the straight-edge section has a length in the range of 1 to 2 millimeters.

9. A milling cutter comprising a cutter body provided with a plurality of cutting inserts according to any one of claims 1 to 8 retained in insert pockets; each insert pocket comprising a base surface and two side surfaces extending generally uprightly from the base surface, each side surface being provided with a support surface; wherein the insert bottom surface abuts the base surface, a first support surface abuts a first operative abutment section, a second support surface abuts a second operative abutment section.

10. The milling cutter according to claim 9, wherein the first and second operative abutment sections are perpendicular to each other.