The manufacturing of ceramics is done with powders. These are formed either by moulding or pressing, and then fired at high temperature well above 1200°C – called sintering. It is at this stage that the ceramic acquires its final properties. There also is a certain amount of shrinkage at this point, which alters original dimensions. The final shape can then be achieved by various methods depending upon the required precision. Also known as “green machining”, the shaping of technical ceramics in an unfired state, is a generally more efficient and economical process than machining after firing, which only allows a minimum amount of grinding and shaping, as the ceramic has become too hard and dense. Depending on the type of ceramic being manufactured, most types of common machining processes can be used to turn the pressed ceramic into something a little closer to the end product. But while cutting, milling and grinding may be easy operations to carry out at the green stage, more precise drilling and hard grinding may have to wait until firing is complete.
The various methods of powder forming are:
- Isostatic pressing
- Injection moulding