Understanding the Three Techniques of Sheet Metal Bending in Metal Fabrication

There are different methods of sheet metal bending used in metal fabrication. Bottoming and air bending methods are the most common and can be done on a single press brake that requires less than 25 tons of pressure. Additionally, press brakes feature a CNC-regulated back gauge that permits bend line accuracy and positioning. 

In this post, we shall discuss three types of sheet metal bending and how they work. They include:

Air Bending

This method uses a punch tool with a V-shaped bottom die. Its profile determines the sheet's bend radius while its stroke-depth determines the bend angle. The stroke depth is usually adjustable; hence during air bending, you can achieve any random angle without die or punch replacement. Choose the bottom die appropriately, depending on the bend radius and sheet metal density.  

The correct choice ensures longer tool life and accurate results. Most professional workshop experts use 2-centimetre bottom die for almost anything. After releasing the punch, the sheet metal slightly springs back, and you'll need to compensate it by overbending. Air bending is not the best method when considering angular precision, but it's perfect for accommodating various materials, depths and angles. 


Just like air bending, bottoming makes use of a V-shaped bottom die and punch. But the punch applies pressure while pressing the sheet metal on the interior surface of the bottom die. Thus, this method requires two different bottom dies, more pressure and the retooling of each bending angle. Contrasted to air bending, bottoming is more accurate and has less of a spring-back effect. 

You'll often find most workshops with brake presses featuring a 90-degree bottoming die. However, for bend angles less than 90 degrees, a similar die can be used for air bending. Remember, bottoming involves significant pressure and force, and it would be wise to use appropriate dies. 


Slotting is another sheet metal bending technique. Slots are vital in minimising the force needed to bend a particular part in the sheet metal down to something you can comfortably handle without the brake press. The slotting technique is perfect for designing custom-made metal enclosures as well as minor robotic frames and extensive unloaded structures. But slotting weakens materials and is thus not preferred for heavy load-bearing parts that precisely obey mechanical integrity of the bent parts. 


These are the three methods commonly used for sheet metal bending and folding. Other methods include coining, folding and rotary bending. Sheet metal folding does not affect the metal thickness but changes its shape. Folding, on the other hand, stresses the sheet metal past its yield power but not above its tensile strength.

To learn more about sheet metal bending and folding, consult a resource in your area.