Gelcast forming of ceramic powders results in dried green bodies which are exceptionally strong. Experiments have shown that these green parts are capable of being machined. Although gelcasting was developed as a near-net-shape forming process, green machining of gelcast materials can be particularly useful for producing prototypes, for custom manufacturing, or for adding features to a cast part which would be too difficult or too costly to include in the mold. A computer-controlled 3-axis milling machine was recently acquired by the Ceramic Processing Group to allow in-depth studies of the green machining of gelcast materials. The machine can accept standard CAD files for conversion to machining instructions.

There is presently a great deal of interest and activity in the ceramics community in the area of rapid prototyping of ceramic components. Most of the effort is focused on the use of stereolithography techniques. However, as an alternative to stereolithography, green machining of gelcast ceramics using a numerically controlled machine appears to offer many advantages. Green machining utilizes a solid billet of homogeneously gelcast material, so there are no seams or bond lines between layers which may have different properties than the bulk material. The green machined parts have a high quality surface finish rather than the stairstepped surface which is typical of stereolithographic processes. And, the capital expenditure required to establish machining capabilities is only a fraction of the cost of a stereolithographic system. Projects are currently underway in the Ceramic Processing Group to evaluate the machining parameters for gelcast ceramics to optimize the cutting speed, to minimize tool wear, and to retain a good surface finish. In addition, new organic binder combinations are being evaluated to improve the overall machining characteristics of the gelcast materials.