Forming techniques

When forming technical ceramic materials from dry powders prepared for processing, the method of forming into the shape required depends upon the method of material preparation and size and shape of the part to be formed. That is, a given customer requirement determines which method can be applied in the expected quality economic relation.

Hereunder you can find several basic forming methods which are available at Bakony Technical Ceramics:

DRY PRESSING

Dry pressing (or Uniaxial) of technical ceramics is a fundamental method of producing high-quality ceramic components. The goals of dry pressing technical ceramics are uniform compact size and green density, consistent part-to-part green density and defect-free compact. Dry pressing is the axial compaction of loosely granulated dry ceramic powders (< 3% free moisture) within a die/punch arrangement. The powder, under pressure, conforms to the specific shape of the punch faces and die. Powder compaction occurs within a rigid-walled die and usually between a top and bottom punch. Press configurations include anvil, rotary, multiple-punch and multiple-action.

ISOSTATIC PRESSING

Isostatic pressing is similar to dry pressing method in the requirements for the powder and in the general steps of the process, but there are several important differences. First, the compaction takes place under hydrostatic conditions. That is, the pressure is transmitted to the part equally in all directions, or very nearly equally. In this way, the die wall friction is significantly reduced or eliminated entirely. Second, the tooling consists of elastomeric molds rather than rigid dies. The powder is loaded into the flexible mold, the mold is sealed and the pressure is applied in a pressure vessel via a liquid. Isostatic pressing is also called cold isostatic pressing or CIP so that it can be distinguished from hot isostatic pressing or HIP, a similar process carried out at high temperature.

EXTRUSION

Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex cross-sections; and to work materials that are brittle, because the material encounters only compressive and shear stresses. It also creates excellent surface finish and gives considerable freedom of form in the design process. In a ceramic relation, extrusion is an excellent molding process for the production of tubes, rods or long parts with different cross-sectional variables. Without attempting to be comprehensive, it is possible to make ceramic insulating tubes, ceramic honeycombs for diesel particulate filters and catalyst supports, or multichannel tubes for ceramic membranes. Although the procedure is relatively simple, it requires a lot of empirical experience, as the process parameters significantly determine the quality of the final results.

CERAMIC INJECTION MOLDING

CIM offers the ability of producing complex three-dimensional components for mass production. If mold design, feedstocks, processing parameters and the postprocessing of green parts are completely controlled, parts with extremely narrow tolerances can be produced without applying other finishing technologies. However, each processing step of the injection molding process is highly sophisticated. However the processing cycle of CIM is more complex than for most other forming and shaping technologies, the advantage of CIM is its capability of producing parts with complex shapes in one step without machining.