Green sand moulding is a flexible, fast and low-cost way to produce moulds for high quality ferrous and non-ferrous castings.
Green sand is composed of silica sand mixed with water, bentonite and other additives, such as coal dust for iron applications. Compressing this moist mixture transforms it into a hard block which can securely contain molten metal.
During automatic mould-making, machines squeeze the sand against a pattern plate. This makes an impression of the part to be cast in each of the two mould halves. The mould is then closed, creating a cavity that the molten metal fills. After cooling, the casting is separated from the mould and the green sand can be re-used. The three most popular automated moulding technologies for green sand casting are vertical, matchplate and horizontal flask moulding.
- Vertical moulding is predominately used for high volume, high precision casting due to its excellent efficiency and accuracy. However, it can also produce shorter runs efficiently.
- Matchplate moulding’s lower speeds and less expensive patterns make it very flexible, perfect for shorter series production.
- Horizontal flask moulding is the traditional way to automate mould production. It is especially suited to large and heavy parts.
Steel pattern plates can produce hundreds of thousands of moulds. Depending on the number of moulds to be made, less durable materials such as wood can be used. Setting cores, filters and so on, within the moulding cycle is quick and simple while fast, easily automated pattern changing makes green sand moulding very suitable for short series production.