Page 209 - Mechanical Engineer's Data Handbook

MANUFACTURING TECHNOLOGY 197

INVESTMENT CASTING

Turbine biada

5.8.2 Shell moulding

This is a form of sand casting done using a very fine
sand mixed with synthetic resin. The pattern is made of
machined and polished iron. The sand mixture is
blown into a box containing the pattern which is
heated to produce a hard, thin (6-10mm) mould
which is split and removed from the pattern and then
glued together. It is a high-speed process, producing
highly accurate castings.

5.8.3 Investment artlng (lost wax
casting)
Wax patterns are made from a permanent metal
mould. The wax patterns are coated with ceramic
slurry which is hardened and baked so that the wax is
melted out. The cavity is filled with molten metal to
give a precision casting. Any metal can be cast using
this process.

Fan impeller
Wax panern
.ylil ofceramic