Thickness alone does not predict a bend
Grade, strength, ductility, surface, rolling direction, cut edge, inside radius, tooling and method all influence the result. Sheets of equal thickness may behave differently.
Specify product standard and grade plus final dimensions, angle, radius, bend length and quantity. Critical parts require engineering and a qualified process.
1. Read material properties
Yield and tensile strength, elongation, chemistry and production route affect bendability and springback. Higher strength can require more force, a larger radius and greater compensation.
Commercial names such as cold-rolled or pickled do not define one exact grade; retain certificate-to-batch traceability where required.
2. Do not guess the minimum radius
A tighter radius raises tensile strain on the outside and may cause thinning or cracking. The permitted minimum depends on grade, thickness, edge and direction.
Use the producer's table and calculate allowance from the real radius and process rather than a generic K factor.
3. Include rolling direction in nesting
Properties can differ parallel and transverse to rolling. Producer guides may specify different minimum radii by bend-line direction.
Mark direction and nest critical parts accordingly instead of optimising scrap alone.
4. Prepare cut edges
Burrs, notches, work hardening and thermal damage can initiate cracks. Coordinate burr direction, cutting and bending; remove defects without excessive thinning.
Assess damaged zinc coating and any repair system against the service environment.
5. Match die opening and method
Air bending, bottoming and coining produce different radius, force and control. A narrow V raises force and marking risk; an excessive opening may not support the geometry.
Required force depends on thickness, bend length, tensile strength and die opening. Stay within tooling and machine limits.
6. Control springback with trials
Elastic recovery opens the bend after unloading. Strength, radius-to-thickness ratio, clearance and friction influence it.
Trial a representative coupon, measure after unloading and record the approved compensation with grade, batch and tooling.
7. Protect coated and visible faces
Clean tooling and compatible protection can reduce marks, but any interlayer can change angle and radius, so repeat the trial.
Define acceptance for coating powdering, flaking and scratches before production.
Production checklist
Provide:
- Sheet standard, grade, thickness and certificate
- Blank, quantity, bend length and tolerances
- Angle, inside radius and datum dimensions
- Rolling direction
- Cutting and edge preparation
- Method, punch, V die and machine capacity
- Springback trial and batch settings
- Surface acceptance criteria