Sand casting

Sand casting is the most versatile among the manufacturing methods and gives the Engineers the freedom to design complex parts from an unlimited number of metals and alloys.

It is a metal casting manufacturing process where the molten metal is poured into the expendable sand mould cavity either by gravity or by force, where it solidifies to form the cavity shape. A 3D object formed by this process is also called casting.  Most common sand casting supplies include pump housing, valves parts, Engine blocks, cylinder heads etc

Characteristics of Sand casting

Over 70% of all metal castings are produced via a sand casting process

Sand casting can be produced in a wide range of sizes from small statues to parts weighs over 100 tons

Very complex parts can be produced easily and in one piece

Low dimensional accuracy

Poor surface finish

Highly adaptable and could be used for handling mass production

How the sand casting process works

The following are the seven main steps of the sand casting cycle

Pattern making step in which a replica of the object to be cast be made of suitable material. The pattern is normally oversized to allow for metal shrinkage during the cooling phase

In mould making step a sand mould is formed by packing sand into the mould around the pattern. The sand mould is divided into two halves, the top half is called the “Cope” and the bottom part is called the “Drag”. When the pattern has removed the cavity it forms remains for pouring the molten metal. Mould will have other features such as Sprue, runners, gate, pouring cup, riser etc which is discussed in detail later.

The clamping step involves the two mould halves Cope and Drag securely clamped together ready for pouring metal.

Pouring molten metal is maintained at a set temperature. Molten metal is poured in quickly to avoid early solidification and

Poured molten metal will begin to cool and solidify once it is inside the cavity. Most of the possible sand casting defects are introduced at this solidification stage

Once the cooling period elapses the mould can be shaken out/broken off and casting

Trimming involves cleaning and removing the section that connected to the main part such as runner, sprue etc

Advantages and disadvantages

Advantages of Sand casting

Large parts can be produced

Complex shapes can be cast easily

Large selection of metal to choose from

Tooling and equipment cost is low compared to some other metal forming processes

Scrap metal can be recycled

Short lead compared to other similar processes

Disadvantages of Sand casting

Low material strength

Low dimensional accuracy

Poor surface finish

High porosity

Secondary machining operation often required

Processing cost is high compared to tooling and material cost

Safety hazards to humans and environmental problems

Removal of the pattern of the thin and small parts is very difficult

HEBEI YOGEM is a supplier of sand casting supplies. if need, contact us!