Bending tools are used for bending the sheet metal to the desired shape and angle. Bending can be performed on sheet metals using bending tools, and bending machines. Normally bending tools and press brakes are used for precision sheet metal bending. For pipe bending and wire bending, suitable bending machines can be used depending upon the size and severity of the bending.
Precision sheet metal bending can be a single stage operation where a single stage or it could be a series of bending done on a progressive bending tool or on a press break to achieve the required profile.
Types of Bending Tools
A bending tool must be decided depending on the shape and severity of bend. Following are the different types of bending commonly used for precision sheet metal bending.
V Bending Dies
V Bending dies have the simplest bending die design. The bending die have the shape of V with an included angle of 90° in most cases. The bending punch is also in the shape of V, but with a lesser angle than the die. And in some cases the bending punches may have a relief after a straight land to a certain length.
L Bending Dies
These are used for 90° bending. L bending dies can produce more accurate and consistent parts compared to V bending. This is due to the presence of spring loaded clamping pads which will hold sheet metal closer to the bending line and then the bending punch pushes the sheet metal into the bending die along the bending line. L bending dies can also be used for bending angles smaller than 90° by providing suitable punch profiles and by controlling the travel of the punch. We may need a series of L bending operations to be done in a progressive metal stamping die to produce complex parts.
These are machine tools designed to do sheet metal bending using a series of simple V bending to create complex shapes.
Sheet Metal Bending Tips
Precision sheet metal bending is not always easy operation. And poor bending tool design and manufacturing can result in the following bending defects.
Insufficient angle on bend part due to spring back
Scratch mark on part
Thinning of sheet metal at bending area
In order to avoid these common defects try one of the following tips mentioned below.
Choose the correct bending operation. For a right angle bend go for L bending rather than V bend, since it is more accurate in most cases.
Verify the clearance between bending punch and die. There should be a clearance of at least one sheet thickness+10% of Sheet Thickness between bending punch and die.
Provide adequate bending radius and polish it to high surface finish. Bending radius is the radius on the bending die on which the sheet material flows to form the desired profile. Therefore it is important to have very good surface finish at this area for smooth flowing of material.
Use corner setting if possible. In case of 90° bending, it is a good idea to provide corner setting to eliminate spring back. Corner setting is the process of coining the material to a small depth along the bending line to overcome spring back. Please note that corner setting may not be possible on very think sheet materials and sheet metals with very high hardness.