Bottom bending, or bottoming, is a press brake operation that forms an angle in sheet metal by enclosing the sheet between the punch and the die. WILA offers durable and high quality precision tooling for bottom bending with 90° angles.
Bottom bending is well suited for applications that require a higher accuracy than air bending, for dealing with springback and for bending near cuts and holes. Material tension caused by cutting or punching is less critical in bottom bending. Bottom bending requires more bend force and each bend radius requires a different set of tools.
Bottom bending with WILA’s high quality and multi-faceted New Standard tooling results in higher accuracy compared to air bending. Under optimal circumstances an angle accuracy of ± 0.25° can be achieved.
With bottom bending the bend result is less dependent on material stress caused by cutting or punching. It also reduces the amount of springback.
If holes, notches, or diagonal edges are located close to the bend, the sheet surface will remain flat, as long as the punch and die have matching surfaces that engage and compress the material.
Compared to air bending, bottom bending allows for a smaller inside bend radius, determined by the shape of the punch and the die.
With bottom bending smaller bend radii can be formed and bending is more accurate. There will be less deformation of holes near the bend line. Material tension in the edge of the sheet metal has less influence on the end result.
Compared to air bending, tooling costs are higher and set-ups take longer. You will need a different set of top and bottom tools for each angle and bend radius. Bottom bending typically requires a tonnage that is 3-5 times higher than that required for air bending.
The shortest flange you can bend will depend on the V-opening and shoulder radius of your bottom tool and the angle of your bend. Check out the WILA Smart Tooling App for advice on the minimum flange length.
Check out our ‘Mark-free bending’ applications page, to learn how to minimize part marking while bending sheet metal.