The process of rotational foaming molding of liquid reactive resin was studied, with unsaturated polyester resin as the shell of unfoamed resin moulded part, and polyurethane as foamed core layer.

Mechanisim of hot-core box non-occupying coating process, its practical effects on manufacturing the whorl shell core, and its technical essentials have been summarized in detail.

The intermittent break expansion phenomenon caused by sliding or overturning of clay core during the scouring process of downstream shell break-induced flows is considered.