Cold Bending of Metal in Manufacturing

Bending is the process by which a straight length is transformed into a curved length. It is one of the most widely used forming process for changing plates (or sheets) into drums, curved channels etc. Bars, rods, wires, tubing and structural shapes as well as sheet metal are bent to many shapes in cold conditions through dies. In all metal bending, the metal stressed beyond the elastic limit is in tension on the outside and in compression on the inside of the bend. Stretching of the metal on the outside makes the stock thinner. Bending a flat strip of metal is commonly done by roll forming.

Roll forming - There are two main types of roll forming ; one uses continuous -strip material for high - production work ; the other uses sheet and plate stock. Materials used for roll forming include carbon steel, stainless steel, bronze, brass, copper, zinc, and aluminum. Among its many products are metal window and screen frame members, bicycle wheel rims, furnace, Jacked rings, trolley rails. Much of the present day tubing is roll-formed cold and then resistance welded.

Continuous roll forming utilizes a series of rolls to gradually change the shape of the metal. As the metal passes between the rolls in a fast-moving continuous strip, the cross-sectional shape is changed to the desired shape. The forms are almost limitless in variation. The intricacy of the shape, the size of the section, the thickness, and the type of material will determine the number of rolls required.

Bending rolls are used for bending sheet and plate stock into cylindrical shapes. A roll-bending machine is made up of three rolls of the same diameter, two of them being held in fixed position and one being adjustable. As a metal plate enters and goes through the rolls, its final diameter is determined by the position of the adjustable rolls. After the part is removed from the rolls, it is placed in fixture to close the gap prior welding. Bending - roll machines range in size from those that are able to roll heavy steel plate 25 mm thick, to small bench models used for light - gauge sheet metal work.

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