Zirconia granulate, with almost zero humidity, is placed in the Widia (tungsten carbide) mould in a precise quantity; the mould is a tank with fix quantity of raw material and movable to increase homogeneity of densification of the products. The powders are compacted through application of pressure in a single direction, using a mobile piston. During pressing, the raw material granulate therefore runs along routes varying in length: shorter in the centre of the product and longer in the peripheral zones. Pressing may vary due to friction of the granules against each other and the granulate against the walls of the mould. This could lead to lower compacting in the so-called neutral compression zone of the product and therefore not uniform distribution of density and shrinkage of the product. Optimisation of the process reduces the differences in shrinkage of the semi-processed product in the different directions.
- high productivity
- high level of automation
- products with relatively simple shape and limited height
- densification and therefore porosity is not uniform, due to not uniform compacting of the powder