Isostatic Pressing

We inserted this sub-page because if you are yourselves engineers, you may realise that the process we are describing on the 'Shafts' page is not true Isostatic Pressing. Truly isostatic pressing would require that the bag with the powder is surrounded on all sides by the pressurised fluid. When pressing shafts, this does not normally happen because the top and bottom of the bag are usually fixed in a steel frame (for example the pressure-chest of the press) and the pressure is only applied radially to the circumference of the bag. So it would be better to describe our process as 'Quasi-isostatic' pressing.

The ceramic powder immediately next to the end-plates does not get quite as much compaction as the rest of the shaft, due to extra friction in the system in these areas, and the compact usually has what are known in the trade as "elephant's foot" in these areas. These have to be trimmed down prior to firing otherwise the centreless grinding of the shaft would be inordinately expensive.