The Fine Art of Steel Bending

Steel curving/bending is a manufacturing process by which metal can be deformed by plastically deforming the material and changing its shape. The material is stressed beyond its yield strength but below its ultimate tensile strength. There is little change to the materials surface area. Bending generally refers to deformation about one axis only. Bending is a flexible process by which a variety of different shapes can be produced though the use of standard die sets or bend brakes. The material is placed on the die, and positioned in place with stops and/or gages. It is held in place with hold- downs. The upper part of the press, the ram with the appropriately shaped punch descends and forms the v-shaped bend. Bending is done using Press Brakes. Press Brakes can normally have a capacity of 20 to 200 tons to accommodate stock from 1m to 4.5m (3 feet to 15 feet). Larger and smaller presses are used for diverse specialized applications. Programmable back gages, and multiple die sets currently available can make bending a very economical process.
Steel Curving/ Bending allows to create various architectural shapes, which is not feasible with traditional way of construction. It also allows considerable savings in the construction cost and the durability aspect of the structure is an added bonus. This story aims to provide the readers with the existing methods of bending, types of bending processes. At the end a few case studies are taken to give readers an over view of what wonders can be created with steel curving/ bending.
Methods of Bending
There are five typical methods of bending in the industry: rolling, incremental bending, hot bending, rotary-draw bending, and induction bending. Each method has its advantages. Some methods are more commonly used in the steel construction industry, while others are more common in the automobile or manufacturing industries:
- Rolling (cold bending) is the typical method of curving steel for construction and is usually the most economical for rolling members with tighter radii. A steel member is placed in a machine and curved between three rolls. Cold bending may also be called “pyramid rolling” because of the three rolls’ pyramid arrangement. Bending occurs when the distance between these rolls is manipulated before each successive pass.
- Incremental bending or gag pressing is usually used for cambering and curving to very large radii. Bending is achieved by applying point loads with a hydraulic ram or press at the member’s third point.
- Hot bending is where a structural member is heated directly and then bent. The heat source could be a direct flame or furnace. This application is used extensively in repair.
- Rotary-draw bending is where the structural member is bent by rotating it around a die. The member is clamped into a form and then is drawn through the machine until the bend is formed. This method produces tight radii and is mainly used for complicated bends in the machine and parts industry.
- Induction bending uses an electric coil to heat a short section of a structural member, and then that member is drawn through a process similar to rotary-draw and cooled with water directly after. In some cases, this process can produce a smaller, tighter radius.