Bend Reliefs in Sheet Metal Design

Bending is a crucial part of sheet metal design and fabrication in order to form precise shapes that enhance functionality, strength and aesthetics of your custom parts and enclosures. It reduces welding and assembly needs, lowers costs by minimizing waste and increases versatility for various applications across industries.

Challenges During the Bending Process

During the bending process, the biggest worry is that the material will end up cracking. This often occurs when the stress concentration at the bend exceeds the material’s tolerance.

Another challenge is tearing or distortion at the edges of the material during bending, which often results in irregularities that compromise the structural integrity and visual quality of the design.

What are Bend Reliefs?

One way to overcome this issue is by using bend reliefs. Bend reliefs are small intentional cuts placed at the ends of bends in sheet metal designs to prevent tearing, cracking, or warping during the bending process. They are also known as relief cuts and are used in nearly every custom design.

They are especially important when a bend ends near an edge, a tab, or a corner where the material would otherwise be stretched excessively. By relieving concentrated stress in these areas, bend reliefs allow the sheet to bend cleanly and maintain dimensional accuracy.

Why Bend Reliefs are Useful

The main purpose of using bend reliefs is to prevent cracking and tearing. Bend reliefs provide a break in the material so it doesn’t stretch too far during bending. This is especially important for parts with narrow flanges or tight bends close to edges.

As mentioned earlier, bend reliefs reduce warping as it ensures that the material has a path to deform without bunching or bulging at the bend edge.

Bend reliefs also protect features near the bend. They do so by isolating bending stress from nearby holes or slots, preserving dimensional integrity.

Finally, bend reliefs also improve aesthetics as you get cleaner corners and less visual distortion. This is important for enclosures and parts with visible flanges.

Guidelines for Designing Bend Reliefs

To achieve good results, make sure the relief width matches or slightly exceeds the material thickness. The bend depth should extend just beyond the bend radius to prevent unnecessary stress. And the bend relief can be rectangular, round-ended, or a custom shape, depending on your part design.

There are also some basic rules for sizing these reliefs too:

For laser-cut parts:

• Bend reliefs should be at least 0.015″/0.381mm wide and inset 0.015″/0.381mm from the bend radius.
• Reliefs can have either a rectangular or rounded shape.

For router-cut parts (used in bent aluminum with machined features like pockets or counterbores):

• Bend relief width should increase with material thickness.
• Reliefs should have a rounded shape.
• General rule of thumb: Minimum relief width should be about half the material’s thickness, but no smaller than 0.045″/1.143mm. (For thinner materials, smaller relief widths may be possible in some cases.)

Conclusion

Bend reliefs play a crucial role in preventing issues during bending. Not adding these reliefs can lead to cracking, tearing, or warping of the material, compromising the integrity of your design.

For further reading on sheet metal bending, explore these resources:

• Sheet Metal Bending Guide: This comprehensive guide covers everything from fundamental concepts and bend radii to specialized bends and common challenges.
• Blog Post on Notches: If cutouts are necessary near a bend, learn why adding notches to your design is the way to go. (We a Proto Tech Tip video on this topic too, watch it here!)

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