Metal Sheet Bending

Sheet metal is widely used in aerospace, automotive electronics, railway and engineering machinery and other fields. Sheet metal bending is a key process of the most parts forming. The bending quality directly affects the final shape and performance of products.

There are many factors that affect the bending accuracy of sheet metal, such as the size accuracy of accessories when expansion, mold selection and the rationality of bending order, so the research on the bending accuracy of sheet metal must be analyzed from these factors one by one. Sundi is committing to the improvement of bending quality by controlling the bending process from material selection to delivery.

We have decades years of experience in metal sheet bending service to consistently manufacturing high quality and high precision metal sheet bending products including the following process :


Laser Cutting

CNC Stamping



Welding and Assemble

The Common Defects of Metal Sheet Bending Parts

As a widely used bending part in construction machinery products, its quality standard has been gradually improved to meet the needs of product quality and production. In the cold working condition, CNC bending machine can use a special mold to bend a variety of required shape of the workpiece, the reasonable bending process directly affect the final shape of the product size and appearance. According to the bending defects, we can take some effective process measures  to improve the workpiece quality through process control and prevention.

Here are some technological countermeasures to amend the common bending defects:

1: Broken

After cutting or blanking, the edge of the material often appear burr or fine cracks,It’s easy to be for form stress concentration.One way to avoid this problem is to ensure that cutting face inside ,so that it’s in the state of compression,and bending effect is better.Another way make sure the workpiece can be deburred\ after bending, repaired with manual grinding wheel after bending.

2: Rebound.

During the bending process, the plastic deformation and elastic deformation of metal materials are synchronous. At the end of bending, spring back occurs due to the recovery of elastic deformation. Spring back affects the dimensional accuracy of workpiece directly, so some technical measures must be taken at the end of bending.

Angle compensation method. If the bending Angle of the workpiece is 90°, the opening Angle of the lower notch (V-shaped) of the bending machine can be selected as 78°. Pressure time increases the correction rate. After bending, we can increase the plastic deformation of the lower groove corner by prolonging the bending machine die through the pressure correction,so that the rebound of the fiber in the tension and pressure area offset each other, so as to reduce the rebound.


When the thickness of the bending  plate is ≥6mm) , the fiber tissue near the bending line becomes longer, which will result in the bulge on the bending Angle. Through the observation of the workpiece after bending in the workshop, the size of the bulge rounded Angle increases as the plate thickness is increasing.For some workpiece with high quality requirements, rounded corner protrusion will affect the dimensional accuracy of welding or assembly, we need to take some technological measures eliminate this problems.

4: Material slide

The bending line and the edge line of the workpiece are uneven.during cutting the material, the direction of the bending line of the workpiece hasthe slit, the length of the slit is the length of the workpiece bending line offset, offset width is half of the width of the slot selected by the bending machine.After the bending process is completed, according to the product drawings for cutting allowance, grinding incision to meet the product quality requirements.

5:Indentation or skid injure

In the process of bending, the workpiece is squeezed by the upper die and the lower groove of the bending machine and produces different degrees of indentation or skid marks. Common carbon steel parts surface roughness requirements are not high, it will not cause slight damage. But some special materials, such as 430-2B, 12Cr17Mn6Ni5,because of its mirror appearance, we need to take certain technological measures to do some protection.

For carbon steel material, the bending width of the lower groove should be increased, so that the radius of the forming fillet is increased, and reduce the extrusion of the lower groove on the workpiece.

For special stainless steel materials, the preparation work before bending is to lay paper isolation in the lower groove of the bending machine. If both sides of the workpiece need be protected, the workpiece can also be laid paper isolation along the direction of the bending line

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