Bending is a process by which metal can be deformed by plastically deforming the material and changing its shape. The material is stressed beyond the yield strength but below the ultimate tensile strength. The surface area of the material does not change much. Bending usually refers to deformation about one axis.

Bending is a flexible process by which many different shapes can be produced. Standard die sets are used to produce a wide variety of shapes. The material is placed on the die, and positioned in place with stops and/or gauges. 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 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 specialized applications. Programmable back gages, and multiple die sets available currently can make for a very economical process.


Air Bending is done with the punch touching the work-piece and the work-piece, not bottoming in the lower cavity. This is called air bending. As the punch is released, the workpiece ends up with less bend than that on the punch (greater included angle). This is called spring-back. The amount of spring back depends on the material, thickness, grain and temper. The spring back usually ranges from 5 to 10 degrees. Usually the same angle is used in both the punch and the die to minimize setup time. The inner radius of the bend is the same as the radius on the punch.


Bottoming, or Coining, is the bending process where the punch and the work-piece bottom on the die. This makes for a controlled angle with very little spring back. The tonnage required on this type of press is more than in air bending. The inner radius of the work-piece should be a minimum of 1 material thickness in the case of bottoming; and up to 0.75 material thickness, in the case of coining.



Sinotech offers an exceptionally wide range of secondary processes that are applied to metals formed in hot or cold processes. Sinotech’ Supplier Quality Engineers determine the availability of the process within the metal forming facility, as well as the quality. If the internal secondary processes do not meet Sinotech standards then the processes are carried out in Sinotech-audited and qualified off-site secondary processing facilities. Sinotech has audited, qualified and worked with QS-9000 and ISO certified secondary processing facilities in China, Taiwan and Korea for over 12 years. Sinotech is dedicated to managing your project on-site and delivering parts to you at lower prices but the same quality, service and terms as a domestic supplier.

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