PROCESS CYCLE FOR MANUFACTRING
OF TURBINE BEARING
The casting process is usually performed on a
horizontal centrifugal casting machine (vertical
machines are also available) and includes the
following cycle as shown in figure 2 :
Fig 2. Process cycle for manufacturing of turbine bearing
The description of the process cycle as follows:
A. Mold preparation
The walls of a cylindrical mold are first coated
with a refractory ceramic coating, which involves a
few steps (rotation, drying, and baking).[4] Once
prepared and secured, the mold is rotated about its
axis at high speeds (300RPM).
B. Pouring
Molten metal is poured directly into the rotating
mold, without the use of runners or a gating system.
The centrifugal force drives the material towards the
mold walls as the mold fills.[3][ During this process ,
the rotating speed of mould should be low(10 RPM)
so that molten metal cannot come outside to the
mould.
C. Cooling
With all of the molten metal in the mold, the mold
remains spinning as the metal cools. Cooling begins
quickly at the mold walls and proceeds inwards. [4]
D. Casting removal
After the casting has cooled and solidified, the
rotation is stopped and the casting can be removed.
E. Finishing
While the centrifugal force drives the dense metal
to the mold walls, any less dense impurities or
bubbles flow to the inner surface of the casting. As a
result, secondary processes such as machining,
grinding, or sand-blasting, are required to clean and
smooth the inner diameter of the part.