On the effect of mould temperature on the orientation and packing of particles in ceramic injection moulding

Particle packing and orientation in Ceramic Injection Moulding are caused by shear rate variations along the part, which are complicated by cooling rates and depend on material properties and process parameters. This work studies particle orientation and packing for a ceramic feedstock in relation to mould temperature, with a focus on the influence from Rapid Heat Cycle Moulding (RHCM). A sample part consisting of bars having different thicknesses (0.4 mm to 6 mm) was injection moulded using first ambient mould temperature and then a rapid heating approach; subsequently, green part microstructure was analysed to detect particle orientation and packing. Results show a more uniform orientation at thick sections using RHCM, with a 15% enlargement of a core layer characterised by randomly oriented particles, as well as a higher homogeneity of powder packing between thin and thick sections. Thus, this study demonstrates that not only can RHCM be used to enhance feature replication capability, but also has the potential to improve critical microstructural properties of green components, which highly influence sintered parts quality.