DE20313042U1 - Cutting insert for a end mill - Google Patents

Abstract

A cutting plate for a milling process has a parallelogram shape with a central hole to secure the plate in various angular settings. All four sides are sharpened as cutting edges and the two corners with smaller angles are radiused (R1) for cutting at slow rates. The centre of shorter sides have convex profiles with large radius (R2) for more rapid cutting. The convex profiles run into the shape of the plate to each side, with a concave profile (4) between the convex profiles and the radiused corners.

Description

PATENT ATTORNEYS gadderbaumer strasse u

D-33602 BIELEFELD

DIPL-ING. BODO THIELKING _{TELEPHONE:(0521) 967820}

DIPL- ING. OTTO ELBERTZHAGEN

ATTORNEY FILE: 6837a

date: 21.08.2003/Sg

Applicant: DEPO Frästechnik GmbH & Co. KG

Von-Liebig-Str. 34
33428 Marienfeld

Description: Cutting plate for a finger milling cutter

The invention relates to a cutting plate for a finger milling cutter for machine milling with the basic shape of a parallelogram, along whose long sides straight cutting edges are formed, to which radius cutting edges are connected, which are located at the parallelogram corners with the smaller corner angles and merge into edges that run in the area of the parallelogram transverse sides.

Such cutting plates are detachably attached to a tool holder of the end mill, so they are interchangeable and also reversible in order to use either one of the two straight cutting edges or one of the two radius cutting edges, which are intended for different milling work. The use of one of the straight longitudinal cutting edges requires an alignment of the cutting plate on the end mill in which the parallel cutting edges are parallel to the rotation axis of the end mill. This corresponds to the so-called vertical position of the cutting plate, with which it is possible to machine a workpiece wall that is aligned parallel to the cutting edges.

- 2 - 6837a

To machine a workpiece using one of the radius cutting edges, the cutting plate is moved from a vertical position to an inclined position so that only the relevant radius cutting edge and not the straight cutting edges or the parallelogram transverse side of the cutting plate comes into contact with the workpiece. Due to the relatively small geometry of the radius cutting edges, only light machining is possible in this operating position, which is why the radius cutting edges are usually used for finishing. When machining a workpiece surface that extends perpendicular to the rotation axis of the end mill, the cutting plate must not build up any pressure on the lower parallelogram transverse side in order to achieve a precise cut with high stability and corresponding running quality during finishing and thus a high surface quality of the machined workpiece surface. For example, the transverse sides of the cutting plate, which correspond to the shorter parallelogram sides of the basic shape, have not been used to date.

The invention is therefore based on the object of creating a cutting plate of the above-mentioned type, in which the transverse sides can also be used for milling processes in accordance with the parallelogram-like basic shape.

This object is achieved in a cutting plate of the type mentioned at the beginning in that cutting edges with a convex curvature are arranged on the parallelogram transverse sides, at least one radius of curvature of which is several times larger than the radius of curvature of the radius cutting edges.

- 3 - 6837a

It is essential for the invention that, with a corresponding, more inclined inclination of the cutting plate, the cutting edge with a weaker curvature on the free transverse side can be brought into engagement with the workpiece, in particular in order to be able to machine a workpiece surface extending perpendicular to the milling cutter axis by roughing. The less curved cutting edges on the transverse sides of the cutting plate not only have a larger radius of curvature than the corner-side radius cutting edges, they can also be made considerably longer than the radius cutting edges. As a result, a much higher level of machining can be achieved with the less curved cutting edges than with the strongly curved radius cutting edges, which is why the cutting edges on the transverse sides of the cutting plate are particularly suitable for roughing work. In this case, the adjacent radius cutting edge is not in engagement with the workpiece, because due to the greater inclination of the cutting plate, this radius cutting edge moves in a free space.

Advantageous design features of the invention emerge from the subclaims.

The invention is explained in more detail below with reference to an embodiment example and the drawing.

Fig. 1 shows a view of a cutting plate according to the invention
in the inclination position for a finishing process
with one of the corner radius cutting edges and

·

·

- 4 - 6837a

Fig. 2 in the same view the cutting plate in the

second inclination position for milling work with a
of the cutting edges on the transverse sides of the plate.

In detail, the outline of the cutting plate can be seen in Figures 1 and 2, which essentially corresponds to that of a parallelogram, apart from the design of the curved transverse sides, which will be discussed below. The cutting plate has longitudinal edges that are parallel to one another and are designed as cutting edges 1. This means that milling work can also be carried out with the cutting plate in a vertical position. In this position, which is not shown in the drawing, the longitudinal center line B of the cutting plate coincides with the axis of rotation A of the milling cutter.

In accordance with the basic shape of a parallelogram, the cutting plate has corners with a corner angle greater than 90 degrees and corners with a corner angle smaller than 90 degrees. At the corners with the smaller corner angles, the cutting plate has radius cutting edges 2 that have a relatively strong curvature. The radius of curvature Rl is correspondingly small. The radius cutting edges 2 represent the continuation of the longitudinal cutting edges 1 and are designed to lead around the respective corner of the cutting plate.

On the shorter, curved parallelogram side of the cutting plate, the radius cutting edges 2, which are convexly curved towards the outside, merge into a concave

6837a

curved edge region 4, which has a corresponding negative radius of curvature. This curved region 4 is followed by a less curved cutting edge 3 on the cutting plate transverse sides, which in the case of a circular curvature has a single radius of curvature R2, which is significantly larger than the radius of curvature Rl of the radius cutting edges 2.

Different milling operations are carried out with the radius cutting edges 2 and the transverse side cutting edges 3 on the cutting plate, which require different inclination positions of the cutting plate. If one of the radius cutting edges 2 is used, the cutting plate is inclined by a smaller angle α, which is shown in Figure 1. The angle α results between the rotation axis A of the milling cutter and the longitudinal center line B of the cutting plate. If milling is carried out with one of the transverse side cutting edges 3, the inclination position of the cutting plate relative to the milling cutter axis A must be increased, and the angle β results between the milling cutter axis A and the longitudinal center line B of the cutting plate, as shown in Figure 2.

In a practical embodiment, a cutting plate of the type in question has a length of approximately 12 mm and a width of approximately 7 mm. The radius of curvature Rl of the radius cutting edges 2 is 1 mm and the radius of curvature R2 of the transverse side cutting edges 3 is approximately 6 mm, i.e. it is six times the radius of curvature

••••••»&Ggr;«

6837a

Rl. The length of the transverse side cutting edges 3 extends over approximately three quarters of the transverse side length of the cutting plate, followed by the negative curvature region 4 with a radius of curvature of approximately 2 mm towards the radius cutting edges 2. With such a geometry of the cutting plate, with an inclination angle α (Fig. 1) of 5 degrees when milling the radius cutting edge 2, there is a distance of approximately 0.2 mm to the workpiece surface to be machined, thus there is sufficient free space below the transverse side cutting edge 3 which is not in use. On the other hand, with an inclination angle β (Fig. 2) of the cutting plate of 15 degrees, there is a distance D of 0.33 mm between the lower vertex of the radius cutting edge 2 and the workpiece surface to be machined, so that in this case there is sufficient free space below the radius cutting edge 2.

Basically, the above-mentioned distances C and D arise at the inclination angle β of the cutting plate because of the two tangents Tl and T2 shown in Figure 2, the tangent T2 is closer to the center M of the cutting plate than the tangent Tl. It is important for this definition that the tangent Tl to the slightly curved transverse side cutting edge is placed in such a way that one of the perpendiculars to this tangent Tl passes through the center M of the cutting plate. Consequently, the base angle of this perpendicular to the tangent Tl is 90 degrees. It is also important for this definition that the tangent T2 to the radius corner edge T2 is the one that runs parallel to the tangent Tl.

Claims (4)

1. Cutting plate for a finger milling cutter for machine milling with the basic shape of a parallelogram, along the long sides of which straight cutting edges ( 1 ) are formed, to which radius cutting edges ( 2 ) are connected, which are located at the parallelogram corners with the smaller corner angles and merge into edges which run in the region of the parallelogram transverse sides, characterized in that cutting edges ( 3 ) with a convex curvature are arranged on the parallelogram transverse sides, at least one radius of curvature (R2) of which is several times larger than the radius of curvature (R1) of the radius cutting edges ( 2 ). 2. Cutting plate according to claim 1, characterized in that the less curved cutting edges ( 3 ) on the transverse sides connect to the radius cutting edges ( 2 ) with a continuous course. 3. Cutting plate according to claim 1 or 2, characterized in that an edge region ( 4 ) with a concave curvature is located between the less curved cutting edges ( 3 ) on the transverse sides and the radius cutting edges ( 2 ). 4. Cutting plate according to claim 3, characterized in that, with respect to the inclination position when working with one of the transverse side cutting edges ( 3 ), the distance of that tangent (T1) to the cutting edges ( 3 ) on the transverse sides whose perpendicular passes through the parallelogram center (M) from this center (M) is greater than the distance of the tangent (T2) parallel thereto to the respective adjacent radius cutting edge ( 2 ).