METHOD OF VACUUM-FILM MOULDING Russian patent published in 1994 - IPC

FIELD: metallurgy. SUBSTANCE: layer of sand which covers a model coated with a film is packed only in moulding. The remainder part one keeps unpacked. A layer (5-15 cm) of sand between model plate and level which is higher than top parts of the model is packed by vibration. In so doing sand density increases owing to decreasing pores between the sand grains. Then the mould is filled up with sand which is not packed and the mould is sealed with the film. As the result the sand layer adjacent to the model is denser, has high strength and low gas permeability. The remainder sand layer is porous and has high gas permeability. In casting the mould gases which sucking out by side walls are easily flow through the porous sand layer. The porous layer is used as an analogue of additional ribs-vacuum ducts for maintaining optimal pressure drop within the mould. EFFECT: enhanced quality of castings.