The types of flow occurring in the runner, gate and cavity of a cylindrical bar mould have been investigated and the relation between the flow and local modulus of the moulding determined for crystal polystyrene. The results suggest that non‐isothermal shear flow was occurring in the runner while the gate displayed the characteristics of shear flow when heated to the polymer melt temperature and a complex type of flow when cold. The cavity was found, under normal injection rates, to fill by a jetting mechanism which often produced surface irregularities in the product and progressive filling from the gate was only observed at low injection rates. Investigation of local moulding properties revealed that while considerable variations within a specimen existed, these were apparently not due to the mould filling mechanism. They have been attributed tentatively to the small opening of the mould which takes place during injection and to cooling strain.
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Sleeman et al. (1974) studied this question.
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