Principle of Sheet Metal Bending

AIR BENDING
Air Bending is a bending process in which the punch touches the work piece and the work piece does not bottom in the lower cavity. As the punch is released, the workpiece springs back a little and 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 will usually range from 5 to 10 degrees. The same angle is usually used in both the punch and the die to minimize set-up time. The inner radius of the bend is the same as the radius on the punch.

In air bending, there is no need to change any equipment or dies to obtain different bending angles because the bend angles are determined by the punch stroke. The forces required to form the parts are relatively small, but accurate control of the punch stroke is necessary to obtain the desired bend angle.

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BOTTOMING
Bottoming is a 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 bottom bending, spring-back is reduced by setting the final position of the punch such that the clearance between the punch and die surface is less than the blank thickness. As a result, the material yields slightly and reduces the spring-back.Bottom bending requires considerably more force (about 50%~60% more) than air bending.

COINING
Coining is a bending process in which the punch and the work piece bottom on the die and compressive stress is applied to the bending region to increase the amount of plastic deformation. This reduces the amount of spring-back. The inner radius of the work piece should be up to 0.75 of the material thickness.

Total Fabrication Solution under one roof.

Phone: +91 22 2764 1236 / 63
Email: info@jjelectrofab.com
Web: www.jjelectrofab.com

Address: Plot No. R-885, M.I.D.C, Rabale
Navi Mumbai – 400701. India