Lindholm, Mikael (Cedergrensvägen 25, Hägersten, S-126 36, SE)
Sjögren, Clas (21 Oldway Drive, Solihull, West Midlands B91 3HP, GB)
Lindholm, Mikael (Cedergrensvägen 25, Hägersten, S-126 36, SE)
| 1. | A cutting insert comprising: a cutting insert body having a plurality of cavities formed therein; a plurality of cutting tips, each of the plurality of cut ting 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 an anchor portion with its base substantially spaced away from the cutting edge of the body, further comprising a joint between each of the cutting tips and the cutting insert body with at least one asymmetric feature on the cutting insert. |
| 2. | The cutting insert of claim 1, wherein at least one of the cutting tips is arranged asymmetrically about a bisector through the corners of the cutting insert body. |
| 3. | The cutting insert of claim 1, wherein at least one of the cutting tips is asymmetric about a bisector through the top surface plane of the cutting tips. |
| 4. | The cutting insert of claim 1, wherein at least one of the cutting tips is asymmetric in the cutting edge portion about a line symmetrically dividing the anchor portion of the cutting tips. |
| 5. | The cutting insert of claim 1, wherein at least one of the cutting tips is asymmetric in the rearward anchor portion about a line symmetrically dividing the cutting edge portion of the cutting tips. |
| 6. | The cutting insert of claim 1, wherein each of the cutting tips comprises, at least in part, a super hard cutting material. |
| 7. | The cutting insert of claim 1, wherein each of the cutting tips are entirely made of a superhard cutting material. |
| 8. | The cutting insert of claim 6 or 7, wherein the superhard material comprises cubic boron nitride or polycrystalline diamond. |
| 9. | The cutting insert of claim 8, wherein the su perhard material further comprises at least one of a nitride, carbonitride, oxide or boride of a metal chosen from groups IVa Via of the Periodic Table. |
| 10. | The cutting insert of claim 6 or 7, wherein the superhard material comprises a composite having a first phase comprising cubic boron nitride or polycrystalline diamond particles and a second phase comprising a metal, a metalloid, or alloys thereof. |
| 11. | The cutting insert of claim 1, wherein the cutting edge portion comprises a top surface and an oppos ing bottom surface, and the superhard material extends from the top surface to the bottom surface thereby defining two cutting edges. |
| 12. | The cutting insert of claim 1, wherein at least the cutting edge portion comprises a top surface and an opposing bottom surface, and the superhard material extends from the top cutting edge surface and from the bottom cutting edge surface to at least one interposing material different from the material in the cutting edges. |
| 13. | The cutting insert of claim 1, wherein at least the cutting edge portion comprises a top surface and an opposing bottom surface, and the superhard material extends from the top cutting edge surface and from the bottom surface a material different from the material in the cutting edges. |
| 14. | The cutting insert of claim 12, wherein the interposing material is a part of the cutting tip. |
| 15. | The cutting inserts of claim 12, wherein the interposing material is a part of the cutting insert body. |
| 16. | The cutting insert of claim 1, wherein the anchor portion of the cutting tips have a general trapezoidal shape. |
| 17. | The cutting insert of claim 16, wherein the an chor portion of the cutting tips is substantially flat. |
| 18. | The cutting insert of claim 1, wherein the anchor portion of the cutting tips has a polygonal shape. |
| 19. | The cutting insert of claim 1, wherein the anchor portion of the cutting tips has an oval or circular shape. |
| 20. | The cutting insert any of claim 16 to 19, wherein the cutting tip comprises a rounded forward nose and a pair of converging forward surfaces that meet at the nose. |
| 21. | The cutting insert any of claims 120, wherein the cutting tip is provided with a waisted section of reduced width relative to the anchor portion. |
| 22. | The cutting insert of claim 21, wherein the waisted section comprises a first pair of substantially angled surfaces and a second pair of surfaces that meet at the section of reduced width relative to the anchor portion. |
| 23. | The cutting insert of claim 1, wherein the cutting insert body is formed from a cemented carbide, cer met, or hard metal alloy. |
| 24. | The cutting insert of claim 23, wherein the cutting insert body is formed of a cemented carbide comprising WC and Co, the cemented carbide comprising 520 weight % Co. |
| 25. | The cutting insert of claim 24, wherein the cutting insert body is in the shape of a polygon. |
| 26. | The cutting insert any of claims 1 to 25, wherein the cavities have a shape that is sufficiently complimentary to the shape of the cutting tips. |
| 27. | The cutting insert of claim 1, wherein at least one of the cutting tips comprises a coating disposed on at least a portion thereof. |
| 28. | The cutting insert of claim 1, wherein the cut ting insert body comprises a chipbreaking feature. |
| 29. | The cutting insert of claim 1 wherein the cutting insert body is a parting and grooving tool. |
| 30. | The cutting insert of claim 1 wherein the cutting insert body is a boring tool. |
| 31. | The cutting insert of claim 1 wherein the cutting insert body is a drill. |
| 32. | The cutting insert of claim 31 wherein at least one cutting tip is disposed substantially parallel to the axial direction of the drill. |
| 33. | The cutting insert of claim 31 wherein at least the cutting tip is disposed substantially perpendicular to the axial direction of the drill. |
| 34. | The cutting insert of claim 1 wherein the joint is a brazed joint. |
FIELD OP THE INVENTION
The present invention relates to cutting inserts having cutting edges formed from a superhard abrasive material.
BACKGROUND OF THE INVENTION
Indexable cutting inserts typically have a polygo- nal 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 work piece 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 work piece. After being used for a period of time, the area of superhard material becomes worn. 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. Patent No. 5,183,362.
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. In addition
relatively complex fixtures have to be used during the brazing process.
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. Patent No. 5,676,496.
Such techniques also present certain difficulties. One disadvantage associated with this second technique is that there is an upper limit of the available volume of superhard material on the finished insert. 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. 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 discloses 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. WO 2004/105983 discloses cutting insert including: 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 symmetric geometry that provides a mechanical retention or lock when inserted
into the cavities of the cutting insert body, the cutting tips further being brazed in the cutting insert body.
Thus, a need exists in the art to address the prob- lems discussed above and others.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
Figure 1 is a top view of a cutting insert formed according to the present invention wherein black areas indicate superhard material.
Figures 2A and 2B are top views showing details of the geometry of a cutting tip formed according to the present invention.
Figures 3A-3G are top and side views of various cutting tips formed according to the present invention.
Figures 4A and 4B are a top view of a threading and thread-milling insert, respectively, formed according to the present invention.
Figure 5 is top view of another type of threading insert formed according to the present invention.
Figures 6A-6E are top and three side sections of other inserts formed according to the present invention. Figures 7A and 7B are side cross-sectional view and top view, respectively, of a drill formed according to the present invention.
Figures 8A, 8B and 8C are side cross-sectional views of drill configurations formed according to the present invention.
Figure 9 is a side view of a tool which can be used for internal turning, boring, slotting or parting formed according to the present invention.
Figure 10 is side view of a parting and grooving tool formed according to the present invention.
Figure 11 is top view of a tool formed according to the present invention.
Figure 12 is a top view of a blank comprising a number of pockets filled with superhard material and cut lines for removal of a plurality of cutting tips therefrom.
DETAILED DESCRIPTION OF THE INVENTION
The cutting inserts 60 for turning, milling, drilling or other machining applications according to the present invention consisting of at least one cutting tip 20 and an insert body 32 are illustrated in Fig. 1. The cutting tips have a geometry that provides a mechanical retention or lock when inserted into cavities of the insert body. The cutting tips 20 are affixed to the cavities is the body 32 by any suitable technique along an interface 40. Suitable techniques include gluing, soldering or brazing. The cavities are preferably provided with a shape or geometry that is complimentary to the shape or geometry of the cutting tips disposed therein. As illustrated in Fig. 1 the cutting tips in top surface plane of the cutting insert are either symmetric 2Ox and asymmetrically arranged in the insert or they are asymmetric 2Oy in at least one way.
More specifically at least one of the cutting tips is arranged asymmetrically about a bisector through the corners of the cutting insert body and/or at least one of the cutting tips is asymmetric about a bisector through the top surface plane of the cutting tips and/or at least one of the cutting tips is asymmetric in the cutting edge portion about a line symmetrically dividing the anchor portion of the cutting tips and/or at least one of the cutting tips is asymmetric in the rearward anchor portion about a line symmetrically dividing the cutting edge portion of the cutting tips and/or at least one of the cutting tips is asymmetric in the plane sym-
metrically dividing the cutting tips between a top surface and a bottom surface.
It is obvious that the asymmetry referred is other than between the cutting edge portion and the rearward anchor portion.
Cutting tips 20 comprehended by the present invention is illustrated in Figure 2A (symmetric) and 2B (asymmetric) . A pair of converging forward surfaces 22a and 22b meet at a forward nose 24, which is preferably rounded. The nose 24 is presented to the work piece during use of the cutting tip. As illustrated in Figure 2A and 2B, at least a portion of the surfaces 22a and 22b, and the nose 24 comprise superhard cutting material 16. 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 giving an essentially trapezoidal shape. The surfaces denominated x a' and x b' can be of the same length as shown in Fig. 2A or of different lengths and shapes as shown in Fig. 2B. The base portion 29 is substantially flat, but other shapes are possible including oval, circular and polygonal shapes.
The superhard material can comprise a boron nitride, such as cubic boron nitride (CBN) , a diamond material such as polycrystalline diamond (PCD) or a suit- able oxide or nitride ceramic such as alumina or silicon nitride or mixes thereof. The CBN, PCD or Ceramic material can 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 and other elements as known in the art such as Al.
Preferably a CBN composite comprises 40-80, most preferably 55-70, vol-% CBN with an average grain size of less than 30μm, preferably less than 5 μm, more preferably 0.1-4 μm essentially in one or more cBN grain size fractions for example bimodal.
Often, the PCBN material also contains smaller amounts (typically <10 wt% each) of other elements, e.g. Co, Ni, Al, W often as compounds such as WC, AlN and Al 2 O 3 . In another embodiment the PCBN material according to the invention contains more than 60 wt-% CBN, preferably more than 80-wt% CBN, with at least 2 wt% aluminium compound and can include another component, generally Co-based. This material is particularly useful for the machining of cast iron.
Figures 3A-G are illustrative of three alternative cutting tip configurations hereby denominated as symmetric at least in the top surface plane: 20a, 20b and 20c. These cutting tip configurations differ with respect to the amount of superhard material contained therein. As illustrated in said figures, a cutting tip is configured such that the superhard material is a relatively minor component thereof 20a or a cutting tip can be configured such that it is formed entirely from superhard cutting material 20c.
In one embodiment the superhard material 16 is continuous from a top surface of the tips (not visible in Figs 3A, 3B and 3C) to an opposing bottom surface of the tips illustratively shown in Fig 3D. In an alternative embodiment the superhard material 16 is discontinuous from a top surface of the tips (not visible in Fig 3A, 3B and 3C) to an opposing bottom surface of the tips and interposed with at least one layer of a material that differs from the superhard material on the top and bottom surface illustratively shown in
Fig 3E and 3F. The configuration as illustrated is symmetric as 3F or asymmetric as 3E but can be vice versa. In a further embodiment the superhard material 16 is present only on a top surface of the tips (not visi- ble in Figs 3A, 3B and 3C) and the opposing bottom surface of the tips has a layer of a material that differs from the superhard material on the top surface illustratively shown in Fig 3G.
With a material that differs from the superhard ma- terial is herein meant one or more of another superhard material, hard material such as some cemented carbides, and softer materials such as some solder alloys.
The insert body 32 in Fig. 1 is composed of any suitable hard material. Examples of suitable materials include cemented carbides, cermets, and hard metal alloys and can be high speed steel for drilling applications, preferably any suitable composition of a WC-Co cemented carbide as known in the art having 5-20 weight % Co. The illustrated cutting insert body 32 is preferably in the shape of a polygon or a diamond and is configured to receive two cutting tips. However, the shape of the body can be any conventional known in the art. The body 30 can be configured to receive any suitable number of tips. It is not necessary that the tips disposed in the body 30 be identical to one another. The optional central through-hole 36 is to be used for clamping and the actual configurations are dependant of the application as known in the art. Figure 4A is an embodiment of the present invention of a threading insert which can be used in turning operations. In this instance, the cutting tip 2Od is formed and inserted so that it lays asymmetrically with respect to a bisector A-A of the corner of the insert.
Figure 4B is an embodiment of the present invention of a thread-milling insert. In this case, the rear portion of the cutting tip is symmetrically arranged along the cutting insert body with multiple retentions and the cutting edge that will be in contact with the work piece is asymmetrical.
Both the figures 4A and 4B are exemplified using the configuration in Fig. 3C referred above.
Figure 5 is another embodiment of a threading in- sert of the present invention. Again, the cutting tip is asymmetrical with respect to a bisector of the corner of the cutting insert and in addition having different cutting tip configurations 20a, 20b and 20c. Within Figure 5 is yet another embodiment since the cutting tip is asymmetrical with respect to a bisector of the cutting edge portion having an asymmetric rearward anchor portion of the cutting tip in 20c. The remaining references are defined in Fig. 2A.
Figures 6 A-E show other embodiments of cutting in- serts of the present invention with exaggerated size of the cutting tips with the configuration in Fig. 3C as example. Figure 6A is a generally square (although it could be rectangular) cutting insert with cutting tips arranged asymmetrically with respect to a bisector of the corner of the insert and also having an asymmetry in the thickness direction of the cutting tip. Figures 6B and D are similar, triangularly shaped inserts in which the cutting tips are arranged symmetrically (Figure 6B) and asymmetrically (Figure 6D) with respect to a bisec- tor of the corner of the insert. In figure 6B the cutting tips are asymmetric in two directions in the cutting edge portion when affixed to the cutting insert body. Figures 6C and 6E are also similar parting-off type tools again with the cutting tips arranged symmet- rical 6C and asymmetrical 6Ξ to a bisector through the
cutting edge. In figure 6C the cutting tips are also asymmetric for example by a tilted top surface with a chip breaking feature.
Figures 7A and 7B show still another embodiment of the present invention. In this case, the cutting tip 52 is located in a drill generally indicated as 50. As shown in Figure 7A, the drill may have a single cutting tip while the drill shown in Figure 7B has 2 cutting tips 52 disposed on either side of the central axis of the drill. Although not shown, the drill can have flutes and is otherwise a conventional product. In Figure 7A, the cutting tip is arranged essentially parallel to a central axis of the drill while in Figure 7B, the cutting tips are disposed essentially perpendicularly to that axis.
Figures 8A-C represent side cross-sectional views of drills of the present invention. For example, Figure 7A is a section taken at A-A of Figure 8A, 8B and 8C. Figures 8B and 8C also are a section B-B of the embodi- ment of the Figure 7B.
Figure 9 represents another embodiment of the present invention in which the surfaces 28a 1 and 28b 1 are of different lengths and are thus asymmetrical. The cutting tip is affixed to a body still refered to as a cut- ting insert body 32. In this particular embodiment, the tool for simplicity reasons still denominated the cutting insert can be used as a boring bar or for internal turning of a work piece and the cutting tip cuts in another direction with reference to the locking feature compared to Fig. 1.
Figure 10 is a side view of an insert of the present invention similar to Figure HC in which the cutting insert is used as, for example, a parting-off tool. The insert is held within a cavity generally indicated as 60, which corresponds in shape to the anchor portion
of the insert. The cutting tip works in another direction with reference to the locking feature compared to Fig. 1.
Figure 11 is a top view of a small part internal boring bar that still is denominated cutting insert with interlock features in the at least partly mutual interface of a divided bar and the cutting tip. The cutting tip cuts in another direction with reference to the locking feature compared to Fig. 1. Further, the insert 60 in Fig. 1 can be provided with a chip-breaker configuration, such as described in U.S. Patent No. 5,569,000.
The cutting insert 60 can be provided with a coating comprising one or more layer(s) as known in the art at least on the functioning surfaces thereof.
In the description the cutting tip has a plane coinciding with the plane of the insert body. It is obvious that the plane of cutting tip can be positioned and/or tilted, below or above the plane of the insert body using adjusted anchor portions and/or cutting tips illustrated in Figs βB and 6C.
Inserts according to the present invention can be made, e.g. according to the method disclosed in WO 2004/105983. Symmetric 'a' or asymmetric 'b' cutting tips are prepared from the blank of Figure 2 of WO 2004/105983 as shown as the blank 10 in Fig 12. The blank contains a plurality of pockets 14 filled with su- perhard material 16. A cutting tip 20 will be defined after cutting along the contour 18 forming a rearward anchor portion 21. The cutting tips will then be arranged and affixed symmetrically or asymmetrically in a cutting insert body.
The methods disclosed in US 4,714,385 or US 5,813,105 are also possible.
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