What bend radius should I model for sheet metal parts?

We air bend, so each bend forms its own curve across the die opening. The finished inside radius depends on the material, thickness, and die, and it is usually larger than the punch nose. The punch is 1mm (0.039in) for parts under 0.16" thick and 4mm (0.157in) for parts 0.16" and thicker. Our Bending Guidelines list the radius a 90° bend forms in each stocked material, and the bend radius calculator there shows it at any angle. Shallow bends form a larger radius, and bends past 90° a slightly smaller one.

You don't need to model a different radius for every bend. Any radius from the punch radius up to the finished radius works: we keep your flanges where you modeled them, and the radius only changes the shape at the corner. Our software flags a bend only when its radius is far enough outside that range to visibly move the outside corner, for example a 1mm radius on a part we bend with a 4mm punch.

For more detail on our bending capabilities, see the Bending Guidelines or reach out to our support team.