Drawing is a metalworking operation in which the diameter or thickness of a metal is reduced using tensile forces. Drawing can be done on both cylindrical metals and sheet metals.
In a cylindrical workpiece, drawing is used to reduce the diameter. In sheet metal, it is used to reduce thickness.
In drawing, the metallic workpiece is pulled through a suitable hole in a die, either manually or automatically. This streches the metal by reducing its cross-sectional dimensions.
The following are the common types of drawing:
Deep drawing is a type of sheet metal drawing. In this process, a die with a cavity is used. The sheet metal is heated to a plastic state and is placed above the cavity in the die. A punch is used to force the sheet metal through the cavity and the metal is drawn.
Wire drawing is used for reducing the diameter of a wire. Wire drawing can be done on wires whose diameter is less than 16mm.
In this operation, a series of dies with decreasing hole size are used. Initially the wire is fed into the die with the largest hole and is drawn through it. It is then fed into the second die with a smaller hole and drawn again. This process is repeated using many dies. In each stage, the hole size of the die decreases. In the end, a fine wire with small diameter is obtained. This wire can be coiled using appropriate machines.
Rod drawing is an operation used to reduce the diameter of a rod. It is similar to wire drawing. Here, a rod is pulled through a suitably sized hole in a die. Due to tensile force on the rod, the diameter of the rod decreases. The image above illustrates rod drawing.
In tube drawing, a hollow tube is pulled through a hole in a die. This reduces its cross-sectional dimensions. The following video illustrates aluminium tube drawing: