Sand casting is the most versatile of
all processes used to cast aluminum. Pouring molten aluminum alloy into a
sand mold produces a casting. This process is well suited for producing
small quantities of identical castings, complex castings with intricate cores,
large castings and structural castings. Below is a list and description of the equipment
needed to produce castings: - Pattern: An impression is formed in bonded sand by a
pattern (duplicate of actual part) which is made from either wood, metal
or plastic and affixed to a wood board or metal plate.
- Flask: The wood board or metal
plate is housed in a box called a “flask”.
- Core: A core is a chemically
bonded sand shape inserted in to the mold to produce internal features of the
casting such as holes or voids.
- Corebox: Pattern for the mold
that creates the holes or voids inside the castings.
- Riser: A Riser is a whole in
the top of the mold to handle the overflow of molten metal poured in the
mold. This prevents air pockets and avoids shrinkage in the main
casting.
- Sprue: A vertical hole created in the sand by
which the molten metal is introduced to the gates.
- Gates: Multiply points in
the sand where the molten metal is introduced to the mold.
PROCESS A cavity is formed into bonded sand by using a pattern to create an
impression, which is a duplicate of the actual part. The sand is
contained in the flask. If required, a sand core is then placed in
the cavity to create the void or hole in the casting. A core print is the
region added to a pattern that is used to locate and support the core inside
the mold. Sprues are created to introduce the molten metal to the mold,
gates direct the metal to the impression and risers contain excess molten metal
compensate for shrinkage as the casting solidifies. After cooling, the
casting and sand are removed from the flask. The sand core is destroyed
thus revealing the void or hole in the casting. Cleaning operations
include cutting, grinding, and abrasive blasting. Secondary such as
machining, anodizing, plating and balancing can be performed. See
diagram below:
|