Abrasive tool making process – material – or composition – With inorganic material
Reexamination Certificate
1999-07-28
2001-08-14
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With inorganic material
C051S309000, C051S308000, C051S293000, C451S540000, C451S546000, C428S221000, C428S408000, C428S293400
Reexamination Certificate
active
06273924
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a tool for machining operations such as grinding, polishing, milling, cutting-off or honing workpieces, particularly for machining workpieces made of metal, where the tool features at least one machining die and where at least the working area of said die consists of a composite material that contains a hard material.
A tool for machining of the aforementioned type is known from the German Patent No. DE-A1 41 06 005. Such tools are used in various applications that basically include the areas of milling, cutting, honing and grinding by means of material removal. Very important in such processes is a precise removal of the material. In addition, such tools should achieve a long service life, that is, it should be possible to use them over a long period with appropriate reproducible and controllable material removal in regard to the desired precision as well. The service life of such tools is basically determined by the hard materials that are present in the working area of the tool. Such hard materials exhibit sharp-edges structures due to the fact that they are crystalline components. Over the duration of machining, this sharp-edged crystalline structure is destroyed such that the abrasive effect of the tool is reduced. Depending on the type of materials being machined with such a tool and, additionally, depending on the machining speed, that is, the speed that the tool exerts on the surface to be machined, and the high temperatures that the tool must withstand, will occur especially in the working area.
The grinding and cutting tool as described in the above referenced German Patent No. DE-A1 41 06 005, includes a substrate body with a synthetic material matrix where the substrate body is carbon fiber enforced. A coating that contains hard materials in the form of diamond or boron nitride abrasive grains in the binding agent is applied to the substrate body itself. An electroplated or electroless deposited metal coating is situated on the substrate body as interim coating between the substrate body and the coating to obtain a better bond of the abrasive coating on the substrate body. The problem with such abrasion tools is that the temperature resistance is limited by that of the synthetic material. The synthetic material tends to become soft or to lose its bonding capacity, especially at high temperature influences, such that, especially at such conditions the inherent stability of the tool can no longer be ensured for precision work. This also results in complicated tool structures, for example, those to manufacture toothings, not being able to be manufactured such that they keep their stability, and thus, their shape, over an extended service life.
The U.S. Pat. No. 4,504,284 discloses a tool with a cubic carrier, where at least one of its edges is built as a cutting edge. The core body or carrier includes a filler material, carbon fibers and carbon black. The at least one cutting edge is located at one edge of the body and consists of diamond or cubic boron nitride crystals and is connected to said carrier body by an interim layer consisting of &agr;- or &bgr;-silicon carbide, or mixtures thereof.
The Japanese Patent No. JP-A-06091541 discloses a grinding wheel whose deformation size is to be reduced when it is rotated under high speed (in relation to the centrifugal forces affecting the grinding wheel). For this purpose, the grinding wheel is made by hardening laminated material through epoxy resins and such, after carbon fibers are wound and laminated in the direction of the circumference. Such coiling strengthens the direction of the circumference of the grinding wheel. Due to the use of epoxy resins as a binding agent to harden the carbon structure, this grinding wheel is not designed for, or cannot be used at high temperatures, because an organic binding agent, such as epoxy resin, softens already at relatively low temperatures and thus loses the strength aimed for.
Finally, the U.S. Pat. No. 4,353,953 relates to an integral composite of polycrystalline diamond and/or cubic boron nitride fibers integrally bonded to a substrate supporting phase. The crystals in the phase of the polycrystalline diamond and/or cubic boron nitride are bonded to the phase of the carrier structure by a medium containing silicon carbide and elemental silicon. Thus, the material is present as a two-layer system, namely the crystals, such as diamonds that are bonded to a carrier body using Si and SiC.
SUMMARY OF THE INVENTION
Based on the aforementioned state-of-the-art and the problems associated with it, it is the objective of the current invention to manufacture a tool for machining that exhibits a high temperature stability, thermal shock resistance and damage tolerance and that can be manufactured with the required precision in any shape and dimension for the desired application.
For a tool with the features stated above, the aforementioned objected is achieved in that the composite material is formed of a fiber structure, which is made of generally continuous carbon and/or ceramic material fibers and is formed of a matrix that contains carbon and hard materials, and in that at least the working area, such as the cutting surfaces of a cutting or milling tool, is made of this composite material.
It is preferred that the fiber structure is made in the form of a web, a weave or a knit.
It is additionally preferred that the hard material is basically made using liquid infiltration of metals in situ.
The basic content of the tool is that at least the working area, for example the cutting edge, is made of fiber structure of continuous fibers comprising the basic structure for binding a matrix that contains the abrasive hard material as a significant component. Preferably, these hard materials are made in situ using liquid infiltration of a metal, that is, liquid metal is infiltrated into a defined open pore structure of the carbon-bound fiber structure. Instead of liquid infiltration, the metal can also be infiltrated in gaseous form, for example, by using the gas phase separation method.
Using this procedure, it is then no longer necessary to use, for example, synthetic materials for embedding the hard materials required for the abrasive effect of the tool surface. The fiber structure made of carbon and/or ceramic material has on the one hand the advantage of withstanding the high temperatures that occur during infiltration of the liquid metal into the porous structure, where said temperatures can be in above 1400° C. with the hard materials under consideration, and on the other hand a preform can made of this fiber structure that prior to liquid infiltration of the metal resembles closely the final contours of the tool to be manufactured, even when said tool has complicated surface structures. This structure of the preform made of carbon-bound carbon fibers and/or ceramic fibers forms an extremely stable basic structure that withstands the operating conditions of a machining tool and that permits sufficient free space, in the area of the working surface, such that the hard materials deposited in the matrix are exposed with their sharp-edged, crystalline structures to carry out the removal of material on the workpiece to be machined, yet are still firmly embedded in the matrix. While this fiber structure forms the stabilizing component during manufacturing, during the material removal, that is, the removal on the material to be machined, the stability of said fiber structure is overshadowed when compared to the embedded hard materials. Still, the fiber structure shows its positive quality and effect in that on the one hand the material strength, material rigidity and thermal shock resistance of the material are increased, and on the other hand, the fiber structures exposed on the work surface, that is, the continuous fibers that end in the surface area of the working area, exhibit a brush-type effect caused by the fiber ends passing over the machined surface and by doing so contribute to a certain degree to the removal of the mater
Friess Martin
Kochendoerfer Richard
Krenkel Walter
Deutsches Zentrum fuer Luft-und Raumfahrt
Marcheschi Michael
Milde Hoffberg & Macklin, LLP
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