Patent Application
20050183893
The present invention relates to cutting inserts having cutting edges formed from a superhard abrasive material, and methods of making the same.
In the description of the background of the present invention that follows, reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art with regard to the present invention.
Indexable cutting inserts typically have a polygonal shape with a superhard material disposed generally at the corners. The superhard material, often a cubic boron nitride or polycrystalline diamond material, aids in the cutting of hard workpiece materials such as metals. These cutting inserts are typically mounted in a fixed position to a cutting tool so as to present one of the corners or areas containing superhard material to the surface of a workpiece. After being used for a period of time, the area of superhard material becomes worm. The cutting insert can then be unfastened from the cutting tool and rotated so as to present a new fresh corner or area of superhard material to the surface of the workpiece.
There are two predominant ways of making such inserts. According to one technique, a stacked structure is formed comprising a first layer of hard backing material and a layer of superhard cutting material superimposed onto the backing layer. Cutting tips are then cut from this stacked structure and brazed to a cutting insert body, typically at a corner thereof. U.S. Pat. No. 5,183,362 to Kuroyama et al., the disclosure of which is incorporated herein by reference, in its entirety, describes such a technique.
However, several problems are associated with such techniques. The braze joint connecting the cutting tips to the body of the cutting insert creates an inherent weak point in the structure. This is particularly true due to the high temperatures that tend to exist during use of such cutting inserts, these high temperatures being in close proximity to the braze joint. Another problem posed by such techniques is that the extent of superhard material presented to the workpiece and available for wear is limited, thus limiting the useful operating period for that particular cutting edge.
A second technique for forming indexable cutting inserts involves providing a blank or substrate having pockets formed therein which are filled with superhard material, then subjecting the blank to a sintering operation which bonds the superhard material to the substrate. The blank is then subsequently machined to give the cutting insert its final shape, i.e.—a generally polygonal body with superhard material disposed at the corners thereof. U.S. Pat. No. 5,676,496, the disclosure of which is incorporated herein by reference, in its entirety, describes such a technique.
Such techniques also present certain difficulties. The process by which the superhard material is bonded to the blank or substrate is difficult and costly. In this regard, the cost of the superhard and substrate raw materials are relatively minor when compared with the costs associated with the process cycle necessary to join them. Thus, from a production efficiency point of view it would seem preferable to form an indexable insert with many corners containing superhard material. That way, the number of costly joining process cycles could be minimized while producing inserts that had many cutting corners. However, customers of such cutting inserts seem to strongly favor cutting inserts having relatively few cutting corners, which are more costly to make on a per unit basis using this technique. Most cutting inserts sold have only 2-4 cutting corners.
Another disadvantage associated with this second technique is that if a single pocket of superhard material is defective, the entire insert cannot be sold and may have to be scrapped. Yet another disadvantage or inefficiency is that only a single cutting insert is produced from each costly and difficult process cycle.
French Patent Publication No. 2,691,657 discloses a cutting insert made with a special autocentering shape made of polycrystalline diamond, CBN or other cutting material. The insert is clamped into the tip by a spring without brazing.
French Patent Publication No. 2,706,339, also an insert of similar materials of a shape (including securing lugs) such that the insert can be secured in the corresponding hole in the tip by a mechanical wedging without brazing.
Thus, a need exists in the art to address the problems discussed above and others.
The present invention provides devices and methods that address the above-mentioned problems, and others.
The present invention provides improved indexable cutting inserts and improved methods of producing the same.
According to one aspect, the present invention provides a method of making a cutting insert which includes: (i) forming a blank having a substrate and superhard material, the substrate having more than 4 pockets, the superhard material disposed within the pockets; (ii) removing cutting tips from the blank by cutting the blank along cutting lines; (iii) providing a cutting insert body having a plurality of cavities for receiving a corresponding number of cutting tips; (iv) inserting a cutting tip into each of the plurality of cavities; and (v) brazing the cutting tips to the cutting insert body.
According to further aspect, the present invention provides a cutting insert which includes: a cutting insert body having a plurality of cavities formed therein; a plurality of cutting tips, each of the plurality of cutting tips disposed in a respective cavity, the cutting tips having a geometry that provides a mechanical retention or lock when inserted into the cavities of the cutting insert body, said geometry including a generally trapezoidal anchor portion with its base substantially flat and spaced away from the cutting edge of the body, and further comprising a braze joint between each of the cutting tips and the cutting insert body.
Exemplary arrangements and techniques according to the present invention will now be described by reference to the drawing figures.
According to the present invention, a blank is formed from a hard material and a superhard cutting material. The blank having a number of pockets for receiving superhard cutting material and a superhard cutting material therein. An illustrative embodiment of such a blank is shown in
In the illustrated embodiment, eight pockets 14 are provided in the substrate 12. Other numbers are clearly possible. As previously discussed, it is an advantage of the present invention to form the blank 10 with as many pockets 14 for receiving superhard cutting material as is feasible. Thus, according to one embodiment, the substrate has more than 4 pockets. According to a further embodiment, the substrate has at least 6 pockets. According to another embodiment, the substrate has at least 8 pockets.
While the illustrated embodiment shows an even number of pockets that are symmetrically distributed. It is also within the scope of the present invention to provide an odd number of pockets, such as 7 or 9. It is also contemplated that the pockets can be located in a pattern that is not symmetrical.
The substrate 12 is formed from any suitable hard material. Examples of suitable materials include cemented carbides, cermets, and hard metal alloys. One suitable composition is a WC-Co cemented carbide having 10-20 weight % Co, and preferably having 15-17 weight % Co.
As shown in
The superhard material can comprise a boron nitride, such as cubic boron nitride (CBN), or a diamond material such as polycrystalline diamond (PCD). The CBN or PCD material may have additions of other materials, such as carbides, nitrides, carbonitrides, oxides, and/or borides of metals chosen from groups IVa to VIa of the periodic table. The superhard material 16 can be in the form of a composite of CBN or PCD particles forming a first phase, and at least a second phase of a semiconductor (e.g.—Si), metal (e.g.—Cu, Ti, Al), metalloid, or alloys thereof.
After the superhard material 16 is placed within the pockets 14, the blank 10 is then subjected to a suitable treatment to unite the superhard material 16 and the substrate material 12. The treatment can comprise a sintering type treatment performed at elevated temperatures and pressures. When the superhard material is initially in the form of a loose powder, a pressing operation may be performed before or during the sintering treatment, as described, for example, in U.S. Pat. No. 5,676,496. Examples of suitable processes are described, for example, in U.S. Pat. Nos. 4,991,467 and 5,115,697, the disclosures of which are incorporated herein by reference, in their entirety.
The superhard material 16 preferably extends continuously from a top surface of the blank 10 (visible in
After above-mentioned step of uniting the superhard material 16 to the substrate 12, material is then cut or otherwise removed from the blank. For example, the blank 10 can be cut along lines 18, which define therein the contour of a cutting tip 20.
The cutting tips 20 can be removed by any suitable cutting or material removal/separation procedure. Once such procedure is wire cutting, such as EDM wire cutting.
The cutting tips are provided with a geometry that will provide a particularly efficacious mechanical retention or lock when placed within the body of an indexable cutting insert. A mechanical retention or lock provides a certain amount of stability for the insert within the tip. However, a much greater stability is provided when the insert is also brazed into the body as will be described in more detail. According to the illustrated embodiment, a cutting tip 20 which is removed from the blank 10 includes a rearward portion 21 which is shaped generally as a trapezoid with its base 29 being substantially flat and spaced away from what will be the cutting edge of the insert. This shape at the rear of the cutting tip provides a substantial anchor for the cutting tip in the cutting insert.
A specific illustrative example of this type of cutting tip geometry comprehended by the present invention is illustrated in
Moving in the direction away from the forward nose 24, subsequent to the converging surfaces 22a and 22b is an area of reduced width or a waisted section 25. The waisted section is defined by a first pair of angled surfaces 26a and 26b, as well as a second set of surfaces 28a and 28b. Surfaces 26a and 28a, as well as 26b and 28b meet at the area of reduced width and define a trough-like formation. As described in more detail below, surfaces 28a and 28b can be the same or different lengths. The cutting tip also comprises the generally planar rear surface 29.
The particular design of the rearward portion, that is, the generally trapezoidal shape with the generally planar rear surface 29 facing away from the cutting edge, provides a solid anchor for the cutting insert within the tip.
The above-described cutting tips of the present invention are affixed to the body of an cutting insert. One illustrative example of an appropriate cutting insert body is shown in
The body 32 is composed of any suitable hard material. Examples of suitable materials include cemented carbides, cermets, and hard metal alloys. One suitable composition is a WC-Co cemented carbide having 10-20 weight % Co, and preferably having 15-17 weight % Co.
Numerous modifications to the illustrated example are contemplated. For example, the illustrated blank 30 is generally in the shape of a polygon or a diamond and is configured to receive two identical cutting tips. However, the shape of the body can be other polygonal shapes, an oval, or circular. The central through hole 36, which can be used for a particular type of mounting, can be omitted. The body 30 can be configured to receive more than two tips. For example, up to four tips can be provided at each corner. It is not necessary that the tips disposed in the body 30 be identical to one another. The cutting tips and/or the body 30 may be machined, prior to, and/or, subsequent to installation of the cutting tips. The cutting insert body 30 and/or the cutting tip(s) 20 may be provided with one or more coating(s). Further, the body 30 may be provided with a “chip-breaker” configuration, such as described in U.S. Pat. No. 5,569,000, the disclosure of which in incorporated herein by reference, in its entirety.
FIGS. 11 A-E show other embodiments of cutting inserts of the present invention.
The present invention and the above-described embodiments thereof provide numerous advantages over conventional cutting inserts and their methods of fabrication.
By forming a blank having a relatively large number of pockets of superhard material, a relatively large number of cutting tips can be produced by each costly and difficult pressing/sintering process cycle, thereby providing an advantage in terms of economy. By removing the tips from the blank and affixing them to the body of a cutting insert, each cutting insert can have a number of tips that is less that the number removed from the blank. Thus, cutting inserts having a relatively few number of cutting tips, for example 2-4 tips, can be manufactured provided to meet the demands of the market, but retain the advantage of being made in an economical manner. The manufacturing costs of producing these indexable cutting inserts according to the method of the present invention can be on the order of 50-60% less than the costs of producing inserts according to the second technique described in the Background of the Invention section herein.
The technique of the present invention also provides the advantage of having an increased yield when compared to techniques such as the second technique described in the Background of the Invention section. When utilizing the technique of the present invention, one defective superhard material pocket may result in one cutting tip being scrapped. By comparison, a single defective superhard material pocket in the second conventional technique described herein can result in the entire cutting insert being scrapped.
According to the present invention, the cutting tips are provided with a geometry that positively locates the tip within the body of the cutting insert upon assembly, thus eliminating the need for complicated fixtures to hold the insert in place during brazing. In addition, the geometry of the cutting tip provides for mechanical retention within the body of the cutting insert in addition to the retention provided by brazing.
A cutting tip formed according to the principles of the present invention also facilitates the formation of a cutting tip wherein the superhard material has a leg length that is greater than that readily attainable by conventional techniques (e.g. 2-3 mm or more). Increased leg length provides more superhard material available for machining the workpiece, thereby adding length to the useful service life of the cutting tip. Moreover, the superhard material of the cutting tip of the present invention extends from the top surface thereof to the bottom surface, thereby providing a first cutting edge surface on the top, and a second cutting edge surface on the bottom of the cutting tip that can be accessed by flipping the cutting insert over.
Additional advantages will be evident to those of ordinary skill in the art. The described embodiments of the present invention are intended to be illustrative rather than restrictive, and are not intended to represent every possible embodiment of the present invention. Various modifications can be made to the disclosed embodiments without departing form the spirit or scope of the invention as set forth in the following claims, both literally and in equivalents recognized by law.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/SE04/00028 | Jan 2004 | WO | international |
This application is a continuation-in-part application of U.S. patent application Ser. No. 10/918,391, filed Aug. 16, 2004 (Attorney Docket No. 024445-308).
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10918391 | Aug 2004 | US |
| Child | 11002664 | Dec 2004 | US |
