Introduction to Basic Manufacturing Processes and ... - always yours

Foundry Tools and Equipments 203
removed and replaced by a steel jacket. Thus, a number of molds can be prepared using the
same set of boxes. As an alternative to the wooden snap boxes the cast-aluminum tapered
closed boxes are finding favor in modern foundries. They carry a tapered inside surface which
is accurately ground and finished. A solid structure of this box gives more rigidity and
strength than the open type. These boxes are also removed after assembling the mould.
Large molding boxes are equipped with reinforcing cross bars and ribs to hold the heavy mass
of sand and support gaggers. The size, material and construction of the molding box depend
upon the size of the casting.
Hinge
Fig. 11.2 Open molding box
(b) Closed molding boxes. Closed molding boxes
are shown in Fig. 11.3 which may be made of wood,
cast-iron or steel and consist of two or more parts.
The lower part is called the drag, the upper part the
cope and all the intermediate parts, if used, cheeks.
All the parts are individually equipped with suitable
means for clamping arrangements during pouring.
Wooden Boxes are generally used in green-sand
molding. Dry sand moulds always require metallic
boxes because they are heated for drying. Large and
Drag
heavy boxes are made from cast iron or steel and
carry handles and grips as they are manipulated by
cranes or hoists, etc. Closed metallic molding boxes
may be called as a closed rectangular molding box
(Fig. 11.3) or a closed round molding box (Fig. 11.4).
Cope
Fig. 11.3 Closed rectangular
molding box
Lugs
2. Crucible
Crucibles are made from graphite or steel shell lined with suitable refractory material like
fire clay. They are commonly named as metal melting pots. The raw material or charge is
broken into small pieces and placed in them. They are then placed in pit furnaces which are
coke-fired. In oil- fired tilting furnaces, they form an integral part of the furnace itself and
the charge is put into them while they are in position. After melting of metals in crucibles,
they are taken out and received in crucible handle. Pouring of molten is generally done
directly by them instead of transferring the molten metal to ladles. But in the case of an oilfired
furnace, the molten metal is first received in a ladle and then poured into the molds.