Shell Moulding

Shell moulding is a process well suited to rapid, automated, repetitive and high-volume production. The most common method for producing shell moulds is to use a dump box as shown in the diagram. The dump box is rotated through 360 degrees, so that the sand contacts the heated surface. An organic thermosetting resin, such as phenol formaldehyde or furane is typically used (2.5-4.5% of sand volume) in conjunction with a catalyst (11- 14% of resin volume). Catalysts include weak aqueous acids such as ammonium chloride or hexamine, a white powder.

The thickness of shell moulding, typically around 10 mm, is determined by the contact time between the sand and pattern. The shell moulding is heated again to cure the sand, causing it to harden. shell moulding is released from the pattern using ejector pins. The entire cycle can be completed in a matter seconds, making it suitable for rapid production. Cores are added to the shell mould and the two halves of the mould are glued and clamped together before the metal is poured. Shell Moulds are relatively robust and can therefore be stored for reasonably long periods of time. Depending on the cores used, spent sand can be reclaimed successfully using thermal reclamation.

Advantages of Shell Molding