WO1998029210A1

WO1998029210A1 - Cutting insert

Info

Publication number: WO1998029210A1
Application number: PCT/DE1997/002867
Authority: WO
Inventors: Udo KÖNIG; Wolfgang Hintze; Hendrikus Van Den Berg
Original assignee: Widia Gmbh
Priority date: 1996-12-30
Filing date: 1997-12-08
Publication date: 1998-07-09

Abstract

The invention relates to a cutting insert with a break-through opening extending from the first face to the second face. According to the state of the art, cutting inserts are known which have a central fixing hole and an upper bore and in which the fixing hole is used for passing through a draw screw or inserting an eccentric or toggle joint, in each case for clamping purposes. During mechanical pre-cleaning, for example by sandblasting or wet blasting, followed by coating, the central fixing holes also make it possible for the cutting insert to be held well on a mandrel or similar object so that several cutting inserts can be threaded without the aid of magnets, grates or other additional holding devices. According to the invention, a snugly fitting insert made of a material the thermal conductivity of which is better than that of the cutting insert material is placed inside the break-through opening.

Description

description

Cutting insert

The invention relates to a cutting insert with an opening extending from the rake face to the support face.

Cutting inserts with a central fastening hole and an upper countersink are known from the prior art, in which the fastening hole is used for penetrating a clamping screw or for inserting an eccentric or toggle lever, in each case for clamping purposes. The central mounting holes also meet during mechanical pre-cleaning, e.g. a sand or wet blasting treatment and a subsequent coating the purpose that the cutting insert in question can be held well using thorns or the like, so that several cutting inserts can be threaded without the aid of magnets, rust or other additional holders.

In principle, however, the present invention relates to any coated or uncoated cutting insert, which preferably consists of a hard metal, a cermet or a ceramic, which may also be coated with hard materials.

During machining, extremely high temperatures are generated in areas close to the cutting edges, which are partly responsible for shortened tool life.

It is an object of the present invention to provide a cutting insert which enables better heat dissipation. This object is achieved by the cutting insert according to claim 1, which has a precisely fitting insert made of a material with better thermal conductivity than the cutting insert material in the opening. The insert in question can be designed to completely seal the opening, whereby the cutting insert must then be arranged in a holder with a clamping claw, or have a central opening which is adapted to the size of the clamping screw which is used for fixing in a holder in a manner known from the prior art. The opening then has an inner jacket or the insert has an outer jacket which is substantially larger than that of the fastening hole. The cutting insert thickness remaining between the opening inside the wall and the cutting edge then only needs to have a dimension which is sufficient to prevent cracking or cutting plate breakage. This leads to the advantage that less expensive metals or metal alloys than hard metals, cermets or ceramics, which are coated or uncoated, can be used as the material for use.

It is known that hard metals, for example, have a thermal conductivity of less than 1 W / (cm × K). Furthermore, it is known that during cutting work on the cutting edge considerable temperatures occur, which are only dissipated to a small extent according to the prior art, so that even when using the cutting insert for the first time in a cutting operation, it cannot be ruled out that the heat generated during the cutting can be ruled out the cutting edges that are not used are impaired by changes in the temperature of the material structure in such a way that they have significantly shorter service lives or wear properties. If one now uses the breakthrough that is advantageously useful during pre-cleaning and coating by placing an insert with greater thermal conductivity therein, the heat generated in the cutting insert can be dissipated to a correspondingly better extent, in particular via the contact surface, but also via the clamping arm in the holder . The only requirement for this is a surface contact of the insert with the wall of the opening. The dissipation of the heat via this insert into the clamping arm or clamping finger and into the support of the holder can be influenced by a suitable choice of material for the holder and in particular by the material of the insert, which is made from a Metal or a metal alloy with good heat capacity, preferably made of aluminum, copper, an aluminum or copper alloy or a low-alloy steel.

According to a further embodiment of the invention, the insert and the opening have an outer dimension that is substantially similar to the outer contour of the cutting insert, preferably the opening top edge and the outer edge of the insert are arranged parallel to the cutting edges delimiting the rake face. Apart from the better heat dissipation that can be achieved, the cutting insert with “inner” insert has the further advantage that less expensive material can be used for the insert. The cutting insert itself consists of a coated substrate material. The extent of the insert, which is accommodated in the opening of the cutting insert, is practically only limited by the required stability of the cutting insert. In other words, the thickness of the cutting insert from the outer edge or the free surface to the edge of the opening must still be sufficiently stable against cracking.

As already mentioned at the outset, it is not necessary to achieve the object of the present invention that the opening has the same cross section over its entire length. In particular, in the context of the present invention, the opening in cutting inserts with free surfaces can taper conically or stepwise towards the contact surface at a positive clearance angle.

In the context of the present invention, it is also possible to make the opening circular for the most part and to impress a different type of rotation-indexable shape only over a partial area, which e.g. octagonal, star-shaped, but can also be rotationally asymmetrical.

According to the invention, machining is used in the production of coated cutting inserts (without a fastening hole) Cutting insert blank produced by pressing, which has an opening that runs from the rake face to the support surface, the cross-sectional profile of which is at least partially non-circular or at least partially circular, and wherein the opening has the largest possible inscribed circle with a diameter that is either <0.2 x IC or <1.5 mm, preferably <1.0 mm or which has a diameter which is> 0.65 IC or> 13.5 mm, where IC is the inner circle diameter. This opening is used after sintering to thread the cutting insert both for pre-cleaning and for holding during coating. The procedure outlined creates the advantage that the holding of the cutting inserts during the pre-cleaning and the coatings can be simplified and therefore cheaper. In addition, the possibility is created to improve the cleaning or the coating itself or to avoid multiple coating passes. The latter advantages result in particular in the case of low-temperature coating processes and / or processes with directional deposition, such as, for example, the PVD or PCVD process.

Further exemplary embodiments are shown in the figures. Show it

Fig. 1 is a plan view of a clamp holder with a

Cutting insert,

Fig. 2 is a plan view of a cutting insert

Fig. 1

3 to 6 a section along the line A - A after

Fig. 2 in different versions.

1 shows a clamp holder 8 with a clamp claw 9 provided in a manner known from the prior art, by means of which a square indexable insert 10 is held. Even if the invention is only explained with the aid of a cutting plate with a square rake face in FIGS. 2 to 6, the invention can be implemented without exception in any cutting insert shapes known in the prior art. A common feature of the cutting inserts 10 is that they have a rake face 11, which can optionally be provided with elevations and / or depressions, chamfers etc., and a bearing surface 12. The rake face 11 and the support surface 12 are substantially parallel, but this is not a mandatory requirement. Likewise, the cutting inserts can be designed as multi-use indexable inserts, in which both the rake face 11 and the support surface 12 are designed the same, so that after the turning, the support surface can be used as a rake face. The rake face 11 is delimited by cutting edges 17, which also represent the boundary line to open areas 13 and 14, respectively.

The cutting insert 10 has a relatively large opening in which an insert 15 is arranged, the surface of which is flush with the rake face 11 surrounding it and also adjoins it. The same applies to the wall of the opening and to the outer jacket of the insert 15. In the present case, the boundary line roughly follows the course of the cutting edge 17, the free surface 13, 14 additionally being inclined at a positive clearance angle. Depending on the inclination of the clearance angle, the cutting insert 10 can have a step 18; in a corresponding manner, the insert 15 has a reset paragraph. The insert 15 can, as shown in FIG. 6, be rectangular or additionally (see FIG. 3) with an upper chamfer 19. The thermally conductive insert 15 can consist, for example, of aluminum or copper, the thermal conductivities of 2.37 W / (cm x K) or 3.98 W / (cm x K), that is to say substantially greater thermal conductivities than the hard metal used with 0.88 W. / (cm x K). The thermal conductivity of the insert 15, on which both the clamping claw 9 rests, and thus also the cutting insert support of the holder 8 Contact comes to ensure that heat generated during machining can be dissipated, thereby reducing the wear of the cutting plate 10 and extending the service life.

The cross-sectional shape of the insert 15 does not necessarily have to follow the course of the cutting edges in the outer contours; equally, in plan view or in cross section, circular, rectangular, hexagonal, oval or other shaped inserts 15 are possible, which are suitable for heat in the clamping claw or the contact surface of the holder. Irrespective of this, the material of the insert 15 can be selected in particular with a view to minimizing the material costs, i.e. this can be a material that fulfills its placeholder function for machining.

If desired, it is of course also possible within the scope of the present invention to also provide the insert 22 with a central bore 23 (FIG. 5). This should be considered in particular if the cutting insert 10 is already connected to the insert 15 before sintering or coating.

In order to create a better point of attack for a curved dome of the clamping claw 9 of the holder 8, the cutting insert 10 can have a gill recess, which is then part of the insert 15. An opening 16 can be provided centrally in the gill trough, which extends as far as the contact surface 12. The opening in question can either be circular with a small diameter that is at most 0.2 times the diameter of the inner circle 22. As an alternative to this, the opening 16 can also be out of round and have any cross-sectional profiles, in particular those which permit centering and rotation indexing. The opening 16 also has advantages during the sintering. Because of the additional outer surface created in the area of the bore, the cutting insert can be better "degassed" during sintering and thus compressed. This improves the structure quality and thus the cutting properties.

Claims

claims

1.Cutting insert with an opening (16) extending from the rake face (11) to the contact surface (12), so that a precisely fitting insert (15) made of a material with better thermal conductivity than the cutting insert material is arranged in the opening (16).

2. Cutting insert or cutting insert blank according to claim 1, characterized in that the insert (15) consists of Al, Cu, Al or Cu alloys or steel.

3. Cutting insert or cutting insert blank according to claim 1 or 2, characterized in that the insert (15) and the opening has a substantially similar external dimension to the outer contour of the cutting insert (10), preferably in each case arranged parallel to the cutting edges delimiting the rake face (11) .

4. Cutting insert or cutting insert blank according to one of claims 1 to 3, characterized in that the opening (16) viewed across its height has different cross-sectional profile dimensions, in particular in the case of cutting inserts (10) with free surfaces (13, 14) at a positive clearance angle, conical or gradually tapered towards the support surface (12).

5. Cutting insert or cutting insert blank according to one of claims 1 to 4, characterized in that it consists of a coated substrate body made of a cermet, a hard metal, or a ceramic, wherein the single- or multi-layer coating is a hard material, preferably a carbide, nitride and / or carbonitride of the IVa to Vla metals of the periodic table, Al2O3 and / or ZrO2, BN, a diamond-like layer or amorphous carbon.

6. Cutting insert according to one of claims 1 to 5, characterized in that the opening has a diameter or largest diameter which is> 0.65 IC or> 13.5 mm, IC being the inner circle diameter (22).