Jetting and weld lines in ceramic injection moulding

A multi-thickness mould cavity incorporating replaceable mould face plates of differing thickness was constructed for assessing the integrity of large section mouldings. The jetting phenomenon, which leads to a moulding replete with weld lines, was overcome for 15 mm thick mouldings by adjusting the nozzle and sprue diameters and by changing the angle of impingement of the melt on the opposite face of the cavity. However, for 25 and 35 mm cavities the formation of multiple weld lines during mould filling could not he completely eliminated. The emergence of cracks near the surface in some sintered parts could he traced back to the formation of weld lines in the injection stage. BCT/324