Relaxation patterns in powder injection mouldings made with repeated flow reversals

Injection moulding suspensions based on both high and low molecular weight organic vehicles and incorporating both spherical and anisotropically shape d particles were prepared. A double end-gated rectangular bar cavity was us ed for injection moulding. Conventional mouldings were made by injection fr om one gate followed by static hold pressure. Modulated pressure mouldings were made in the same way but reciprocating flow was induced between the ga tes during solidification. The mouldings were sectioned, polished and heat treated whereupon a pattern of rings emerged in relief preserving the histo ry of flow reversals as the solid-liquid interface advanced from the mould walls. (C) 1999 Elsevier Science Limited. All rights reserved.