Solidification in the Cavity

It is interesting to note that successful injection moulding of engineering ceramics has been accomplished in the past with parts of small cross section such as individual small ceramic turbine blades or thread guides. When moulded parts contain large sections such as the hub of a rotor, problems are likely to be encountered, not just at the polymer removal 

Major Binder Minor Binder Temp °C 1/n Pa-ls-1 n d1ogn/dt Pa s ir xIO  

To prolong pressure transmission to the material in the cavity, the sprue, runners and gate should be as large as possible and temperature dependence of viscosity should be low. Mhen the largest moulded section is much larger than the sprue, other methods are needed to keep the sprue molten and these are discussed below. 

Much of the shrinkage of a moulded body may be taken up by mould packing under the influence of post injection pressure, but residua shrinkage may 

Flfnme 111 Optical micrograt of shrinkage voids In an alunlna moulded part. 

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