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How To Prevent Common Sheet Metal Bending Defects

Sometimes, the process of bending sheet metal can go wrong and result in defective bends. These bends lower the quality of the bent metal. In production, this is a setback that affects the effectiveness of the process. This article discusses some of the common defects and how to prevent them from happening.

What Causes Sheet Metal Bending Defects?

Quality issues can be caused by various factors. In sheet metal bending, the variables that can contribute to bend defects revolve around the machining process. Primarily, the press brake machine must be calibrated correctly to avoid these defects.

Using a press brake with the wrong tonnage can result in bend defects. Overbending and underbending are the two most common defects we will discuss later. These bend defects happen when the press brake has a higher or lower tonnage than required.

While each bend defect has a specific reason for occurring, there are general causes associated with all errors. For instance, unskilled operators contribute significantly to most bend defects. This can be avoided by ensuring the technician is well-equipped to handle the sheet metal bending operation.

Ways of Preventing Sheet Metal Bending Defects

Let us explore the common defects, how they happen, and ways to prevent them in production.

Springback

Springback

Springback is among the most common defects in this metal fabrication process. It is characterized by the metal sheet returning to its original shape after bending. In other words, the bend radius of the bend is not the expected one. It is a deformation error that is common with several types of metals. 

The springback defect happens because of the elastic properties of metals. When a bend is formed, inner and outer bend angles are formed. These two bends are controlled by different forces during the formation. Springback happens when there is a difference between these two forces.

How to prevent springback

While springback is inevitable in most cases, some strategies are utilized to prevent it. One common way of avoiding springback is by overbending. Adding a slight pressure over the desired level helps the bend stay in position. Other strategies include widening the die angle and using a smaller punch radius.

How to prevent springback

While springback is inevitable in most cases, some strategies are utilized to prevent it. One common way of avoiding springback is by overbending. Adding a slight pressure over the desired level helps the bend stay in position. Other strategies include widening the die angle and using a smaller punch radius.

Overbending and underbending

These two defects occur when the bend exceeds or does not reach the expected angle. In overbending, the bend exceeds the desired angle. This can happen due to various issues, including incorrect calculations and tooling.

Before the sheet metal bending process, the technicians calculate the bend radius, factoring in aspects like bend allowance, material thickness, and neutral axis. If these factors are not considered, the resulting bend can be larger or smaller than expected.

How to prevent overbending

Overbending must be prevented unless it is intentionally allowed for reasons such as correcting springback. The standard prevention technique involves using the right tooling and recalibrating the press brake settings.

How to prevent under-bending

Underbending can be prevented in several ways. The correct press brake tonnage is recommended to ensure the die reaches the proper depth and forms the desired bend angle.

Cracking

Cracking

Some metals exhibit cracks at the bend after the bending process. This happens mostly when there is stress concentration at the bend. Cracking affects the quality of the bend and makes it unusable. This defect occurs mostly due to poor ductility, malleability of metals, and tooling issues.

How to prevent cracking

Factoring in the metals’ properties is a good strategy to avoid cracking. To clarify, a particular metal should be handled in a specific way based on its properties. This includes using the right tools, bending techniques, and tonnage.

Sheet surface damage

Some bent parts can exhibit defects such as indentations, gouging, or scuff marks. These issues are not as expected, but they exist. And when they do, they affect the structural integrity and aesthetics of the sheet metal. These defects occur from poor maintenance of the press brake machine and other sheet metal bending tools.

How to prevent sheet surface damage

Preventing surface imperfections on sheet metal bends is easy. This is because they are caused by negligence and easily controllable issues. Ensure that tools are always inspected for lubrication, wear and tear, and other setbacks.

Wrinkling

Wrinkling happens when the sheet metal “bundles up” and forms wrinkles around the bend. The resulting figure looks like the metal has been pushed together or there is excess material overlapping each other. This defect is seen mostly in thin rather than thick metals due to the ability to resist or sustain compression forces.

How to prevent wrinkling

Simulating or prototyping is a strategy that can be used to avoid producing bends with wrinkles. This is because the simulations or prototypes help you identify the correct parameters that you will use to ensure that the bend does not have this defect.

Inconsistent bending

The bend geometry needs to be perfect. This includes the angles, radius, and depth of the bend. However, inconsistent bends are bound to happen in some cases. They appear wavy or rippled, the opposite of perfect bend geometry.

How to prevent inconsistent bending

Inconsistencies in bend geometry emanate from material properties, incompatible bending methods, and the like. The die clearance can also cause this defect. Therefore, you need to ensure that you use the right tools for the specific material and ensure that the tools are properly maintained.

Splitting

Splitting

This is another common defect that results in the sheet metal splitting into multiple parts, partially or fully. Splitting happens predominantly in stamping operations as opposed to bending operations, but it affects the appearance of the metal sheet.

How to prevent splitting

Metals that cannot withstand a certain level of stretching or elongation are susceptible to splitting. Using too much force or pressure on metals that can withstand elongation can also cause splitting. Therefore, it is recommended that a balance be struck to ensure the correct force is used in the fabrication process.

Thickening

This defect is seen in the bend radius of the sheet metal. It happens when improper tools penetrate the sheet metals. The thick cross-sectional area formed by the process makes it hard to deform the sheet metal. A bulging on the outer bend of the sheet metal characterizes thickening.

How to prevent thickening

Press brakes and other machines with a higher tonnage are recommended to prevent thickening. The higher the tonnage, the higher the force exerted on the bend. This will ultimately ensure enough force is distributed to the part. Also, a larger bend radius should be set to avoid this defect.

Conclusion

Defects associated with sheet metal bending are preventable when the right technique and parameters are used. Most of these defects are caused by incorrect settings and tool choices. Therefore, always use the correct tools and settings for a perfect bend with every press. Contact us if you have any questions about the sheet metal bending process.

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