Sand casting is a technique commonly used in metal casting. Molten metal is poured into a mold that is surrounded by silica sand. Silica sand is most used because it is inexpensive. It also comes from river deposits and other large water sources, so it is readily available and can be recycled. Sand casting is widely used in the aluminum castings,gray iron casting,and alloy castingsPermanent Pattern Sand MoldingPermanent pattern sand molding is made from wood, plastic or aluminum. The material is shaped into the shape of the part to be produced. Most times it is made larger than the actual size. During cooling, the metal shrinks. Sand is compacted around the pattern, so the metal will hold its shape when poured into the cavity. The 'Demonstration Guide for Sand Casting of Metals' states that wood is used the most, but has disadvantages. The wood can warp, and the sand abrades it, which makes for a short life span. Metal patterns last longer, but are more expensive to make. Which method to use is based solely on how many castings need to be completed. Full Mold Sand CastingFull mold sand casting is made up of expanded foam. The pattern is created at the same time the metal is poured into the cavity by vaporizing the foam pattern. This technique is faster and gives a better surface finish. Any areas that need to be filled afterward are packed with dry molding sand. According to the mechanical engineering department at Eastern Mediterranean University in Turkey, there are advantages to using sand casting. It's the quickest way from pattern to production. The technique can be used to create complex geometrics, and any metal that can be liquefied can be used in sand castingEastern Mediterranean University also listed some disadvantages. Sand casting creates empty spaces during casting, and this weakens the metal. Also, the surface finish can be poor, and any small or thin parts are hard to remove from the pattern after cooling. Automated Sand CastingAutomated sand casting is performed in a foundry. All the tools and materials are located there, and large quantities of castings are produced. According to the Eastern Mediterranean University mechanical engineering department, this form of production is done by machines. A hydraulic press forms the mold by pressing the pattern into sand, which allows for non-stop casting. valve body casting: http://www.fotaichina.com/products/p290.html