Dry press molding of alumina ceramic compared to injection molding

Dry pressing forming: The dry pressing forming technology of alumina ceramic is limited to objects with simple shapes and inner wall thickness exceeding 1mm, and a length to diameter ratio of no more than 4:1. The forming methods can be uniaxial or bidirectional. There are two types of presses: hydraulic and mechanical, which can be semi automatic or fully automatic forming. The maximum pressure of the press is 200Mpa. The output can reach 15-50 pieces per minute. Due to the uniform stroke pressure of the hydraulic press, the height of the pressed parts varies when there are differences in powder filling. The pressure applied by the mechanical press varies depending on the amount of powder filling, which can easily lead to differences in size shrinkage after sintering and affect product quality. Therefore, the uniform distribution of powder particles during the dry pressing process is very important for mold filling. The accuracy of filling quantity has a significant impact on the dimensional accuracy control of manufactured alumina ceramic parts. Powder particles larger than 60 μ m. The maximum free flow effect can be achieved between 60 and 200 mesh, achieving the best pressure forming effect.

Injection molding method: Injection molding is the earliest molding method used for alumina ceramic. Due to the use of gypsum molds, the cost is low and it is easy to shape large-sized and complex components. The key to injection molding is the preparation of alumina slurry. Usually, water is used as the flux medium, followed by the addition of glue remover and binder. After thorough grinding, exhaust is discharged, and then poured into the gypsum mold. Due to the adsorption of moisture by the capillary of the gypsum mold, the slurry solidifies inside the mold. When hollow grouting is carried out, when the slurry adsorbed on the mold wall reaches the required thickness, the excess slurry needs to be poured out. To reduce the shrinkage of the billet, high concentration slurry should be used as much as possible. Organic additives need to be added to the alumina ceramic slurry to form a double layer on the surface of the slurry particles, ensuring stable suspension and no precipitation of the slurry. In addition, it is necessary to add adhesives such as ethylene glycol, methyl cellulose, alginate amine, and dispersants such as polypropylene amine and arabic gum, all of which are aimed at making the slurry suitable for grouting and molding operations.