Bend relief is a cutout near the end of a bend that gives material room to deform. It can prevent a flange from dragging an adjacent edge into the bend.
Identify the local conflict
A bend ending at an inside corner can stretch or tear the nearby material and distort the neighboring flange. A relief separates the deforming zone from the constrained material. The shape might be a slot, rounded cutout or another geometry suited to the part and process.
The relief must extend through the region that needs to move. A short cosmetic notch at the edge may leave the actual deformation zone constrained. Width, depth and corner treatment should reflect thickness, inside radius, cutting capability and the fabricator’s guidance.
An illustrative design review
Suppose a 2 mm-thick bracket uses a 2 mm inside bend radius. A trial relief might be sketched with width on the order of thickness and enough depth to pass the bend transition. This is a starting sketch for supplier review, not a universal 2 mm-wide or 4 mm-deep acceptance rule. Inspect the developed flat pattern and the formed solid together.
Ask whether the relief leaves adequate ligament to a nearby mounting hole and whether it creates an unwanted opening in a sealed enclosure. Moving a hole or splitting a flange can sometimes solve the design conflict more cleanly than enlarging a relief indefinitely.
| Review point | Question |
|---|---|
| Bend end | Does the relief separate the moving material? |
| Cut process | Can the slot be cut consistently without excessive burr? |
| Strength | Is enough material left around loaded features? |
| Appearance / enclosure | Is the resulting opening acceptable? |
| Inspection | What tearing or distortion is unacceptable? |
Validate the formed part
Evaluate tearing, flange distortion and local fit on a representative sample. Record the material, direction and tooling used. A relief does not correct every bend problem: inappropriate radius, short flange support or a wrong flat pattern can still cause defects. Link the relief design to the actual bend process and drawing revision.
Locate the relief in the flat pattern
A relief that ends before the bend transition leaves a ligament resisting the flange’s movement. A slot that extends farther can release that ligament but also removes more load-carrying material. That is the design trade-off; making every cutout as large as possible is not a complete solution.
For one supplier-specific reference, Protolabs’ bend-relief article describes a cut at least 0.030 in (0.762 mm) wide and extending at least 0.015 in (0.381 mm) beyond the bend-radius region. Its 90° example combines 0.100 in thickness and 0.030 in radius to obtain 0.130 in. These are that article’s process guidelines, not universal minimum dimensions for every alloy or cutting method. Confirm the datum used for depth with the fabricator.
| Shape | Useful design question |
|---|---|
| Round-ended slot | Can a smooth root release the flange without leaving a sharp termination? |
| Rectangular cutout | Are corner stress, burr and the opening after forming acceptable? |
| Larger corner opening | Will sealing, strength or a nearby hole require redesign? |
Check both the flat and folded models for remaining ligament and adjacent features. A design review should retain the material, tooling and inspection criteria, then record actual tearing or distortion on a trial part. No before/after production trial is implied by this schematic.
Content updated October 8, 2026. Sources and numerical examples are explained above; examples are not production test results. Editorial method · Report a correction.
References and verification
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