Powder Compaction by Dry Pressing

Powder compaction by dry pressing is industry.s preferred and most widely used forming method for ceramic parts. This can be explained by the high efficiency of the process, which has two variants: uniaxial die pressing; and isostatic pressing. Both methods can be automated to a high degree and are used in the mass production of parts such as ceramic cutting tools (via uniaxial pressing) or spark plug insulators (via isostatic pressing). Uniaxial die pressing produces shapes with accurate dimensions in large quantities, in the shortest cycle times. Compared to injection molding, dry pressing requires a relatively small amount of additives (_2%), and thus allows for less expensive additive removal operations. However, as fine powders lack the flowability required for the process, in general they must be transformed into a freeflowing press granulate, by employing a granulation process. A second problem results from the nonuniform pressure transmission, leading to nonuniform particle arrangements and density variations in the compacts, which is a well-known source of nonuniform grain growth and other sintering defects [1]. This chapter provides a brief but current review of the fundamental aspects of dry pressing, the practice of uniaxial die and isostatic pressing, and the granulation of fine ceramic powders to granulates.