The history of sand casting or moulding can be traced back to 17th century AD, in France. In its most basic format sand casting is the process of creating a metal object by pouring molten metal into a mould made of sand. It is a complicated process with many variables that must only be done by professionals at factories specifically known as foundries, where the process is considered something of an art.
Sand casting is relatively inexpensive and sufficiently refractory even for steel foundry use. In addition to the sand, a suitable bonding agent (e.g. clay) is mixed with the sand. The mixture is moistened, usually with water to develop strength and plasticity of the clay and to make the aggregate suitable for moulding. The sand is typically contained in a system of frames or mould boxes known as flasks. The mould cavities are created by compacting the sand around models, or patterns, or carved directly into the sand. The metal is poured into the cavities, filling up the space, and then left to cool and solidify. The mould is broken off to reveal a perfect metal sand casting. The sand is then recycled and reused for the next mould.
Sand casting is ideal for fairly small production jobs, complex casting shapes and large castings. For mass production, fully automated moulding machines increasingly replace the labour intensive technique of sand casting. Sand casting is the most widely used metal casting process in manufacturing and almost all casting metals can be sand cast. Sand castings can range in size from very small to extremely large. Some examples of items manufactured in modern industry by sand casting processes are engine blocks, machine tool bases, cylinder heads, pump housings and valves.
Sand casting is a specialised field and requires a highly skilled and experienced team to execute. Environmental factors and the volatility of actual materials all play a role in the success of sand casting – it is a science and an art form.