7 Common Sheet Metal Bending Problems and How to Solve Them

In CNC Sheet Metal Bending Services, engineers and operators often run into issues caused by bending methods and material behavior. With the right design tips and process adjustments, many of these problems can be avoided, helping reduce material waste and improve production efficiency.

Below, we share practical bending guidelines based on real manufacturing experience, written to help engineers and fabrication teams achieve more reliable results.

Material Bulging at Bend Corners

After bending, material near the bend corners can squeeze outward, making the final part wider than the original design. This bulge becomes more noticeable as the material thickness increases.

Solution: Add semi-circular relief cuts on both sides of the bend line during CNC Sheet Metal Bending processing. The recommended diameter is at least 1.5 times the material thickness. The same approach works well for edge return (hemming) designs.

Inside Bend Radius Design

For sheet metal bending, the inside bend radius should be equal to or greater than half the material thickness. If no radius is specified, repeated stamping and bending will naturally wear sharp corners into a radius over time. This can slightly change the effective length on one or both sides of the bend.

Best practice: Always define the inside R radius clearly in the drawing to keep dimensions consistent.

Preventing Deformation After Bending

Bent sheet metal parts can easily deform under load.

Solution: Add 45-degree reinforcement ribs near the bend area, as long as they don't interfere with other components. This significantly improves stiffness and structural strength.

Maintaining Strength in Long, Narrow Parts

Long and narrow sheet metal parts often struggle to stay straight and are more likely to bend under force.

Solution: Form the part into an L-shape or U-shape whenever possible. If a continuous L or U structure isn't feasible, pressing multiple emboss ribs can also improve rigidity and flatness.

Transition Details and Die Protection

At transitions between flat surfaces and bend areas, it's best to add narrow slots or move edge holes away from the bend line. This helps prevent burrs and edge tearing.
Design tip: Slot width should be at least 1.5 times the material thickness. Always mark R corners in drawings—sharp or right-angle corners can cause punch and die damage, leading to tool repairs and production downtime.

Edge Corners: Safety and Tool Life

In Custom Sheet Metal Forming, unless there's a special requirement, sheet metal edges should include a small radius.
Sharp corners create safety risks and stress concentration. In tooling, sharp die corners are prone to cracking, while sharp punches can chip. Even if they don't fail immediately, wear will eventually create unintended radii, leading to burrs and rejected parts.

Hemming (Edge Folding) Process Details

1. Hemming Types and Accuracy

Hemming can be done on one side or both sides in custom sheet metal forming. For higher precision, double-sided hemming is recommended.
For a material thickness of 1.0–1.2 mm, the hem height should be at least 3 mm. Smaller hems reduce clamping stability and dimensional accuracy.

2. Handling Protrusions on Side Walls

When hemming, internal features or protrusions on the side wall should be kept at least 10 mm away from the bottom surface.
If they're too close, the bend area beneath the protrusion won't be fully formed by the punch, creating a larger and uneven R radius that affects appearance.
A shallow pre-pressed groove along the bend line can help improve consistency.

3. Clearance for Side Wall Holes

Holes near the bottom edge of a hemmed wall should maintain at least 3 mm of distance. Otherwise, they may stretch or deform during bending.
A common solution is to add a relief slot above the bend line, matching the hole length and using a width of 1.5 times the material thickness. This interrupts tensile stress without affecting the visible hole.

Conclusion

These seven questions are challenges that LVMA engineers frequently encounter when providing Sheet Metal Manufacturing Services to customers. By applying these solutions early in the design and fabrication stages, manufacturers can improve quality, protect tooling, and reduce costly rework.

If you'd like to learn more practical sheet metal fabrication tips or need Sheet Metal For Manufacturing Services, feel free to contact LVMA—we're always happy to help.