Bending Guide
Springback Explained
Why a part that looked perfect at the bottom of the stroke opens up slightly once the punch lifts — and what to do about it.
Springback is the tendency of bent sheet metal to relax back slightly toward its original flat shape after the bending force is removed. It's not a defect or a mistake — it's simply how metal behaves — but it means the angle you set the punch to isn't the angle you get on the finished part unless you plan for it.
Why it happens
When sheet metal bends, the outer surface of the bend stretches and the inner surface compresses. Most of that deformation is plastic — permanent — but a thin band of material near the neutral axis (the layer that neither stretches nor compresses) stays within its elastic range. Once the punch retracts and the bending force disappears, that elastic portion tries to return to its original, unbent state. It can't fully undo the plastic deformation around it, but it pulls the whole bend open by a few degrees in the process. That small recovery is springback.
What makes springback worse
- Higher-strength materials. More elastic energy is stored during bending, so more of it releases afterward. Stainless steel and spring steel spring back noticeably more than mild steel.
- Larger bend radius. A gentler bend (relative to thickness) has proportionally more elastic recovery than a sharp one.
- Thinner material. Relative to a given bend radius, thinner sheet has a higher ratio of elastic to plastic deformation.
- Wider V-die. More room for the material to move before contacting the die means more springback, and it becomes harder to predict consistently.
- Air bending vs bottoming/coining. Air bending shows the most springback of the three methods; bottoming and especially coining suppress it substantially. See air bending vs bottoming vs coining.
Typical springback angles (rule-of-thumb ranges)
These vary by grade, thickness and die setup, but as a rough planning guide for a 90° air bend:
| Material | Typical springback |
|---|---|
| Soft aluminium (1xxx/3xxx) | ~0.5-1.5° |
| Mild steel (S235/S275) | ~1-3° |
| Aluminium 5052/6061 | ~2-4° |
| 304 stainless steel | ~4-6° |
| Spring steel / high-strength alloys | 6°+ |
Always trial-bend a sample before committing a full production run — these ranges are a starting point, not a substitute for a test piece.
How to compensate for it
1. Overbending
The most common fix on a press brake: set the punch to travel slightly past the target angle, so the part relaxes back to the correct angle after release. If a part needs to finish at 90° and the material typically springs back 3°, the punch is programmed to hit around 87°. Modern CNC brakes with angle-measurement systems can adjust this automatically; manual setups rely on test bends and operator experience.
2. Bottoming or coining
Switching from air bending to bottoming or coining physically presses the material into the die shape, which suppresses springback directly rather than compensating for it after the fact — at the cost of significantly more tonnage.
3. Adjusting die selection
A narrower V-die (within reason, following the 8×T guidance) tends to produce more consistent, slightly lower springback than an oversized one, since there's less room for the material to move before the die controls it.
4. Test bends before production
Because springback depends on the specific coil, temper and batch of material as much as the nominal grade, a short test bend before a full run is the most reliable way to dial in the right overbend angle for that particular job.
Check your tonnage before adjusting the die
Changing V-die width to manage springback also changes the tonnage you need — check both together.
Frequently asked questions
What causes springback in sheet metal bending?
Bending stretches material past its elastic limit on the outside of the bend and compresses it on the inside, but a thin layer near the neutral axis stays elastic. When the punch retracts, that elastic layer tries to return to its original shape, pulling the bend angle slightly open.
Which materials spring back the most?
Higher-strength, lower-ductility materials spring back more. Stainless and spring steel typically show noticeably more springback than mild steel, and mild steel more than soft aluminium.
How do you compensate for springback?
The most common method is overbending — setting the punch to a slightly sharper angle than the target so the part relaxes to the correct angle. Bottoming or coining reduce springback directly by pressing the material into the die shape.
Does a bigger V-die make springback worse?
Generally yes — a wider die gives the material more room to move before contacting it, increasing springback and making it less predictable.