Cutting insert and cutting tool

Description of the invention

The invention relates to a replaceable cutting insert for milling tools and a milling tool provided with replaceable cutting inserts for machining metal objects, in particular for machining internal corners with a small radius of rounding, and for machining shoulders.

Such cutting tools, generally in the form of end mills, are used to machine metal dies and molds and other parts with complex spatial geometry also provided with shoulders. Such applications often require internal corners with a small fillet radius, sometimes less than 0.5 mm. Typically, geometrically complex surfaces of metal workpieces are machined with shank face mills with a rounded cutting edge or with cutting inserts with a rounded cutting edge. End mills with a rounded cutting edge and replaceable cutting inserts with a rounded cutting edge that can machine internal corners with a fillet radius of less than 0.5 mm are not manufactured.

When machining large workpiece surfaces, it is most economical to use a milling tool with indexable inserts with a large cutting edge radius, and then use a tool with a small cutting edge radius when machining small areas and reducing the radius of the inside corners as needed.

EP 1 157 768 discloses a diamond shaped cutting insert provided with a corner cutting edge with the required small radius of rounding. This indexable insert has a positive cut geometry and only two corner cutting edges.

DE 28 11 086 discloses an interchangeable cutter insert for milling tools, rotatable to the working position, of a parallelepiped shape and of a parallelogram cross-section, having two opposite end faces and two side surfaces between them, and two opposite front surfaces. The front surfaces and front surfaces intersecting with each other form the main cutting edges, while the front surfaces (11, 12) and side surfaces intersect at an angle less than 90 ° and form the edges (17, 18), part of which is the secondary cutting edge. The remainder is in the form of a recess (21, 22) in which the clamping element sits. Each depression is formed by smooth end faces (23, 24), the extension of which is delimited by edges parallel to the minor cutting edge.

The object of the invention is to provide a design for such a cutting insert which has four corner cutting edges which are capable of machining internal corners in the workpiece with a small fillet radius. It is also an object of the invention to provide a milling tool structure in which such cutting inserts can be embedded. Moreover, it is an object of the invention to provide a construction of a cutting insert and a milling tool of the type mentioned, which can be used for the treatment of shoulders.

The cutting insert and milling tool according to the invention are intended for machining objects made of metals and their alloys. Typically, the indexable insert is produced by the method of pressing and sintering carbide powders. However, it can also be produced by an injection molding process.

The object of the invention has been achieved by providing an interchangeable cutting insert structure provided with two identical opposite diamond end faces, a circumferential side surface situated between two opposite end faces, the circumferential side surface being perpendicular to the center plane of the cutting insert, and six component side surfaces, four generally flat major side faces and two diametrically opposite rounded corner side faces, each side face corner being situated between and abutting the two major side faces with the first two cutting edges and the two second cutting edges cuts connected to a defined face, each first cutting edge being inclined with respect to the median plane at a first non-zero angle, and each second cutting edge is inclined with respect to the median plane at a second non-zero angle, the two first cutting edges connected to the predetermined end face are inclined at an angle to each other and are located on respective major side surfaces parallel to each other, and the other two the cutting edges connected to each face are inclined at an angle to each other and are situated on respective parallel to each other, larger side surfaces,

With two corner cutting edges connected to each end face, each corner cutting edge connected to the first cutting edge and to the second cutting edge to form a continuous cutting edge section with them, in two opposing flat face areas, each of which is connected to a corresponding end face and is parallel to the center plane of the cutting insert, and in a through-hole whose axis is equal to the axis of the cutting insert, and the flat end areas form the axially outwardly projecting areas of the cutting insert.

Upon request, the cutting insert preferably has a first angle that differs from the second angle.

Alternatively, if desired, the first angle does not differ from the second angle.

If desired, the peripheral side surface is provided with two diametrically opposed generally flat minor side surfaces, each minor side surface being located between the two major side surfaces.

Generally, the cutting insert has 180 degree rotational symmetry with respect to the first, second, and third symmetry axes, the first axis of symmetry being perpendicular to the flat face regions and aligned with the axis of the through hole, and the second axis of symmetry passing through the smaller side surfaces and the third axis of symmetry. the axis of symmetry passes through the corner side faces.

Each end face preferably includes a rake face connected to each cutting edge section, the rake face extending from the cutting edge section down into the plate towards the center plane.

The rake face preferably contacts along the line of engagement with an inclined plane extending from the line of engagement away from the median plane.

An inclined plane connected to the defined face preferably extends from a connection line to a flat face area of ​​the defined face.

The object of the invention is also achieved by developing a milling tool structure equipped with a number of interchangeable cutting inserts that can be rotated to the operating position. Each cutting insert is seated in the tool seat in such a position that the working first cutting edge is positioned at a predetermined axial rake angle.

Typical axial rake angle is 0 ° to 5 °.

The replaceable cutting insert and the milling tool according to the invention are shown in an example of a constructional solution in the accompanying drawing, in which fig. 1 shows a cutting insert, in a perspective view, fig. 2 - an insert according to fig. 1, in a front view, fig. 3 - an insert according to fig. 1, in a side view, fig. 4 - plate according to fig. 1, in a different side view, fig. 5A - part of the plate according to fig. 2, section VA-VA according to fig. 2, fig. 5B - a fragment of the plate according to Fig. 2, in section VB-VB according to fig.2, fig.5C - section of the plate according to fig.2, section VC-VC according to fig.2, fig.5D - section of the plate according to fig.2, section VD-VD according to fig. 2 and fig. 6, a milling tool, seen from the side.

Figures 1 to 4 show the replaceable cutting insert 10 rotated to the operating position, provided with two identical diamond-shaped opposite end faces 12 and a circumferential side surface 14 therebetween. Each end face 12 is delimited by a circumferential edge 16 along which end face 12 contacts peripheral side surface 14. Each peripheral edge 16 includes two continuous cutting edge sections 18 separated from each other by non-cutting edge sections 20. Adjacent to each cutting edge section 18 is a recess 22 delimited by a generally flat face area 24. Thus, the cutting insert 10 has two opposing flat face areas 24. The two opposing flat face areas 24 are parallel to each other and to a median plane M located centrally between the flat faces 24 of the indexable insert 10.

The circumferential side surface 14 is perpendicular to the median plane M and is provided with eight component side surfaces, four generally flat major side surfaces 26, two diametrically opposite rounded corner side surfaces 28 and two diametrically opposite flat minor side surfaces 30. Each planar minor side surface 30 it is located between the two larger side surfaces 26. Likewise, each corner side surface 28 is positioned between and communicating with the two larger side surfaces 26.

Each cutting edge section 18 includes a first cutting edge 32, a second cutting edge 34, and a corner cutting edge 36 with which the first and second cutting edges 32, 34 engage. Each first cutting edge 32 extends away from the corner cutting edge 36 with which joins, to the adjacent non-cutting edge section 20, and towards the median plane M. The first cutting edge 32 is preferably straight and is inclined at a non-zero first angle Θ1 to

Similarly, each second cutting edge 34 extends from the corner cutting edge 36 with which it connects to the adjacent non-cutting edge section 20 and toward the median plane M. The second cutting edge 34 is preferably straight and is inclined at a second angle Θ2 to the median plane M deviating from zero. The first and second angles θ1, Θ2 may be equal or not equal. The two first cutting edges 32, which engage the defined face 12, are inclined at an angle to each other and are situated on respective, parallel to each other, larger side surfaces (26), and two second cutting edges (34) connected to the defined face. the face (12) are inclined at an angle to each other and are situated on respective larger side faces (26) parallel to each other. The flat minor side surfaces 30 form a pair of diametrically opposed flat corners of the cutting insert 10.

Each face 12 includes a rake face 38 communicating with each cutting edge section 18. The rake face 38 extends from the cutting edge section 18 down the plate towards the median plane M, to the joint line 40 along which it meets an inclined plane 42 extending from the joining line 40, in a direction from the median plane M to the flat face area 24. The rake face 38 (Figures 2 and 5A through 5D), proximate to the first cutting edge 32, has a varying length (measured perpendicular to the first cutting edge 32) along the cutting edge. It has the first length L1. (in section VA-VA) near an adjacent non-cutting edge section 20, and a second length L2 (in section VB-VB) near an adjacent corner cutting edge 36, the second length L2 being greater than the first length L1 and varying in a manner continuous between the two values ​​along the cutting edge. In contrast, the rake face 38 close to the second cutting edge 34 has a third length L3 that is approximately constant along the length of the second cutting edge 34. For the sake of clarity of the image, it should be noted that the connection line visible as line 40 (Figs. 1 and 2) is only conventional. As can be seen in Figures 5A through 5D, the line of connection 40 is in the form of a folded area of ​​limited width forming part of the recess 22.

The cutting insert 10 has 180 degree rotational symmetry with respect to the first, second, and third symmetry axes R1, R2, R3. The first symmetry axis R1 is perpendicular to the planar face regions 24, the second symmetry axis R2 passes through the flat minor side surfaces 30, and the third symmetry axis R3 passes through the corner side surfaces 28. The second and third symmetry axes R2, R3 lie in the median plane M, while the first symmetry axis R1 is perpendicular to the second and third symmetry axes R2, R3. The cutting insert 10 is provided with a through hole 44 with an axis coincident with the first symmetry axis R1. Through hole 44 is located between the flat face areas 24, and its length is also the axial width of the cutting insert. As shown in Figs. 3 and 4, the cutting insert 10 is axially widest in the areas where the flat face areas 24 are directly opposite each other. The flat face regions 24 define the axially most protruding regions of the cutting insert 10. The rounding radius R of the corner cutting edges 36 is typically 0.2 mm to 6.36 mm.

Fig. 6 shows a milling tool 46 according to the invention. The milling tool 46 is an arbor milling cutter 48 machining recesses of the workpiece 48 with a small fillet radius consistent with the radius R of the corner cutting edge 36 of the cutting insert 10. The milling tool 46 may also machine the shoulders with the second cutting edge 34 of the cutting insert 10. The milling tool 46 has an axis of rotation A and is equipped with a body 50 in which there are mounted in seats 52 replaceable cutting inserts 10. Each cutting insert 10 has two working cutting edges, a working first cutting edge 32 ', a working second cutting edge 34', and working corner cutting edge 36) The seats 52 are shaped such that the working first cutting edge 32 'is positioned with an axial rake angle γ of typically nearly 0 °, but generally not greater than 5 °. Since the working first cutting edge 32 'is positioned at a first angle względem1 with respect to the median plane M of the cutting insert 10, between the cutting insert 10 and the parts of the workpiece surface 48 close to the working second cutting edge 34', the clearance angle α is usually close to the angle α Θ1, but generally not less than the angle Θ1 - 5 °.

The first working cutting edge 32 'may be divided into a front portion approximating the working corner cutting edge 36, a rear portion remote from the working corner cutting edge 36', and an intermediate portion therebetween. When performing machining operations, including making small radius shoulders, such as when making dies and molds, the corner cutting edge 36 is mainly involved. Even though the front portion of the operative first cutting edge 32 'is also involved in such machining, the recess 22 should extend , Near

The entire length of the working first cutting edge 32 ', from the front portion to the rear portion, to maintain a clearance between the front face 12 close to the rear portion of the working first cutting edge 32' and the workpiece 48. If, instead of exclusively flat minor side surfaces 30, the cutter insert has corners extending beyond the flat minor side surfaces 30, a portion of the cutter insert extending beyond the flat minor side surfaces 30 and engaging the working first cutting edge 32] may adversely engage the cutting circle delimited by the working first cutting edge 32 '. This is especially important when machining protruding parts and also when machining the shoulders of the workpiece.

The invention has been presented by way of example only, and all variations and modifications of the solution falling within the scope of the inventive idea and the patent claims should also be considered protected.