keywords： Alumina ceramic Zirconia ceramics
There are many kinds of forming methods for alumina ceramics, such as extrusion, injection, dry pressing, hot pressing and so on. In recent years, many new forming technologies have been developed at home and abroad, which can make different forming methods according to different shapes and sizes of products. Here are two most commonly used molding technologies:
Grouting forming method: This is the earliest forming technology of alumina ceramics, with low cost and price. It is suitable for large-scale workpieces with complex shape. The alumina slurry of this forming method is usually water as the medium, and then added with binder and degumming agent. After grinding, the alumina slurry is exhausted and finally introduced into the gypsum mold. If it is hollow grouting, when the formwork wall is adsorbed with slurry of sufficient thickness, it is necessary to pour out the surplus slurry to reduce the shrinkage of the body, so the slurry with high concentration shall be selected as far as possible.
Dry compression molding: this molding technology is only used for workpieces with simple shape, internal thickness of more than 1mm and diameter and length of less than 4:1. The method is divided into single axial and two-way axial. The press is divided into mechanical chamber press and hydraulic press, with full-automatic and semi-automatic forming mode. The maximum pressure of the press is 200MPa, which can produce about 15-50 workpieces per minute. Because the stroke pressure distribution of the hydraulic press is average, the height of the pressed workpieces will be different when there is a difference in the filling powder. The mechanical press is the opposite, it will produce as much pressure as the amount of filling powder, which is easier to shrink the size after sintering and affect the quality of products. Therefore, in the process of dry pressing, the uneven distribution of powder is particularly important for filling, which has a great influence on the precise control of the size of the alumina ceramic parts.