Sand molding

Mechanical Engineering

Sand molding:

Sand molding is a process of making sand mold with the help of pattern. The mold cavity of required shape and size is formed in sand by using pattern of same size and shape. This cavity is known as sand mold. Molten metal is poured in this mold and allowed to solidify. After solidification, casting is removed by generally destroying the sand mold. The sand mold can be classified as.

(i). Green sand molds (ii). Skin-dry molds (iii). Dry sand molds

Sand molding methods:

Bench molding – It is used for relatively small molds. The mold is prepared on a conventional bench. Any kind of sand molds can be made by this method. The various bench molding methods are

Two box molding – Two boxes known as cope (upper) and drag (lower) are used to make sand mold. These are fitted with suitable clamping and locating device.

Three box molding – In flange type pattern, a third box known as ‘cheek’ is used to facilitate the molding work. All the three boxes are clamped properly during pouring the metal.

Stacked molding – It is used when a number of small castings, each having one flat surface, are to be made. A common passage is there for all molds to pour the molten metal.

Floor molding – It is used to make medium and large molds. Generally two boxes (cope and drag) are used to make a mold. It can be used to make any kind of sand mold. It is a very slow and laborious process.

Pit molding – When the size of pattern for mold is very large to be handled in flasks, pit molding is used. Pit acts as a drag part of flask and a separate cope is used above it. Generally green sand is used in pit molding. This method is quite slow and laborious.

Machine molding – This method can be used for any size and kind of sand molds. It is a very fast method which uses machine to make sand molds but it requires mounted patterns.