Ceramic article and method of manufacture therefor

Abstract

A ceramic article resulting from a chemical interaction between a particulate ceramic material and a ceramic matrix material is described. The ceramic matrix results from at least partial chemical transformation of a precursor material. A chemical bond between the ceramic matrix and the particulate ceramic material is developed during manufacture. The configuration of the ceramic article is developed through use of a rapid prototyping process. A ceramic article comprising different compositions in two or more regions of the article is described. A manufacturing process comprising the steps employed to produce such a ceramic article is also described. The ceramic article described herein is particularly suited for use as a mold for metal casting. The manufacturing process disclosed herein enables production of such a mold within a matter of hours, rather than days, as required by prior art casting technologies.

Description

RELATED PATENT DOCUMENT [0001] This application is a divisional application of pending application Ser. No. 10 / 357,053, filed Feb. 3, 2003. Priority is claimed for this application, based on the filing date of said pending application.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates generally to ceramic articles and methods for the manufacture thereof. The invention is particularly suited for use in manufacturing ceramic molds for metal casting processes. [0004] 2. Description of Related Art [0005] The origins of many of the commonly used methods of manufacturing ceramic articles have been lost in antiquity. Naturally, many of these methods have been updated over the years, but the essential elements of many methods of manufacturing ceramic articles haven't changed very much in centuries. Most of the common methods employ a vehicle, typically water, for facilitating manipulation of ceramic particles into whatever configuration is appropriate...

AI Technical Summary

Benefits of technology

[0019] Briefly, the present invention provides a ceramic article that can be produced in a short time, employing a novel combination of chemical transformations and rapid prototyping processes. The key feature of the invention is the use of a precursor material that is amenable to processing by one of a variety of rapid prototyping processes. The precursor material is typically provided as a liquid that can be transformed to a solid, either during or immediately following fabrication of an article by a rapid prototyping process. This attribute of the precursor material can be achieved by employing a monomeric resin that is polymerized during processing. The polymerized resin is subsequently transformed into a ceramic matrix material, preferably by oxidation. Particulate ceramic material that had been intermixed with the liquid precursor material becomes embedded in the ceramic matrix material. Further chemical interaction between the particulate ceramic material and the ceramic matrix material develops a chemical bond therebetween. Still further chemical interaction therebetween can create a new chemical species. The sequence of chemical interactions typically results in transformation of substantially all of the precursor material into ceramic matrix material. Depending upon the nature of the specific materials selected for a particular application, formation of the new chemical species may consume part, or all, of either the particulate ceramic material or the ceramic matrix material.

[0022] One particularly useful application of the ceramic article of the present invention is as a mold for casting metallic articles. Through the technology disclosed herein, a ceramic mold can be produced in a matter of hours, rather than the several days that might be required to produce such a mold by conventional investment casting technology. Further, a mold made by the process of the present invention can have a core as an integral part thereof, thus avoiding the need for a separate core, as is required in conventional investment casting technology.

Problems solved by technology

Naturally, many of these methods have been updated over the years, but the essential elements of many methods of manufacturing ceramic articles haven't changed very much in centuries.

Removal of such water is a slow process, particularly if the ceramic article has substantial thickness.

Such shrinkage can be a significant problem if the nature of the ceramic article mandates close dimensional tolerances.

In such applications, the slow process of removing water from the ceramic can significantly lengthen the process of developing a new product.

Note that in either process, casting design is limited by the requirement for removing the pattern, which is typically made from aluminum, brass, plastic and the like.

While SLA is useful in making a pattern for investment casting, it does not address the matter of making a mold for investment casting.

However, the localized heating to cause sintering can also cause sufficient thermal shock to crack the workpiece.

However, both the Deckard method and the variation described by Langer et al are vulnerable to considerable shrinkage during manufacture.

However, considerable shrinkage can occur during sintering, so that an article that is dense enough to have useful strength can be too distorted to serve its intended function.

However, this variation is still subject to shrinkage during sintering.

Notwithstanding advocates of SLS and 3D printing, none of the above-referenced RP technologies, nor any other known RP technology, is fully appropriate for the manufacture of ceramic metal casting molds.

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