A dobra de chapas metálicas é a espinha dorsal da transformação de chapas planas em funcionais, 3Peças D – de gabinetes elétricos a componentes automotivos. Como engenheiro ou comprador, acertar o projeto de dobra evita retrabalhos dispendiosos, garante durabilidade da peça, e acelera a produção. Este guia detalhasheet metal bending processes, regras de design críticas, e aplicações do mundo real, using insights from Xometry’s precision fabrication services.
1. What Is Sheet Metal Bending?
Before diving into design, vamos esclarecer o básico:
Sheet metal bending is a fabrication process that reshapes flat metal sheets into V, U, or grooved shapes. It uses jigs or dies to apply force—force that must exceed the material’syield strength—to create plastic deformation. Unlike cutting (que remove material) or joining (which connects parts), bending keeps the workpiece’s volume intact.
It’s one of the three core sheet metal processes, and its success depends on two key factors: choosing the right bending method and following design best practices.
2. Common Sheet Metal Bending Methods
Not all bending jobs call for the same technique. Each method has unique strengths for precision, velocidade, e compatibilidade de materiais. Below’s a breakdown to help you pick the right one:
| Bending Method | Como funciona | Principais vantagens | Melhor para |
|---|---|---|---|
| Air Bending | Uses a V-shaped bottom die and a top punch to push metal into the die (no full contact). | Low force, flexible for different angles. | Prototypes or parts where tight precision isn’t critical. |
| Bottoming | Punch presses metal fully against the die’s surface—metal angle matches the die’s angle. | High accuracy for tight angles. | Parts with strict angle requirements (por exemplo, colchetes). |
| Fundição | Similar to air bending but uses 5–30x more force. | Precisão ultra-alta, minimal springback. | Alto volume, high-tolerance parts (por exemplo, componentes aeroespaciais). |
| Folding | Clamps the long side of the metal; a beam bends it around a curved profile. | Can create positive/negative angles, gentle on materials. | Large sheets (por exemplo, cabinet panels) or parts needing smooth edges. |
| Wiping | Clamps the sheet’s long side; a tool moves up/down to bend around a profile. | Faster than folding. | Produção em alta velocidade (note: risk of scratching thin metals). |
| Rotational Bending | Uses a rotating cylindrical upper die and matching bottom die; roller action bends the sheet. | Consistent curves, ideal for rounded parts. | Pipes, tubes, or curved enclosures. |
| Meshing Bending | Creates two opposite bends (each <90°) separated by a “neutral mesh.” | Avoids material distortion in tight spaces. | Complex parts with overlapping bends (por exemplo, caixas elétricas). |
Exemplo: If you’re making 100 aluminum brackets for a furniture project (3mm de espessura), bottoming é ideal. Use a V-mold opening of 18mm (6x the material thickness)—this ensures the bracket’s 90° angle stays precise, with no springback.
3. 10 Critical Bending Design Tips (Evite erros!)
Poor design leads to bent parts that crack, deform, or fail. Follow these rules to ensure your design works for fabrication:
3.1 Keep Wall Thickness Uniform
All parts must have consistent thickness—this prevents uneven bending. Xometry can handle sheets up to6.35mm de espessura, but tolerance depends on geometry. Por exemplo, a 4mm thick laptop chassis can’t have a 2mm thin section near a bend—it will warp during processing.
3.2 Add Clearance for Holes & Sulcos
Holes and grooves near bends deform easily. Follow these gaps:
- Buracos: At least 2.5x the material thickness from the bend (por exemplo, 10mm gap for 4mm thick steel).
- Sulcos: At least 4x the material thickness from the bend edge.
- Both features: At least 2x the material thickness from the part’s outer edge (avoids bulging).
3.3 Choose the Right Bend Radius
A too-small radius causes cracking. The minimum bend radius =1x the material thickness (por exemplo, 3mm radius for 3mm aluminum). Também:
- Keep radii consistent across the part (reduces tool changes and costs).
- Design all bends in the same plane (avoids reorienting the part, economizando tempo).
- Skip small bends on large/thick parts (they become inaccurate—e.g., a 2mm radius on a 10mm thick steel plate will twist).
3.4 Design Curling Carefully
Curling (rounded edges) adds strength but needs space:
- Outer curl radius: At least 2x the material thickness.
- Holes near curls: Distance = curl radius + espessura do material (por exemplo, 5mm radius + 3mm steel = 8mm gap).
- Other bends near curls: Distance = (6x material thickness) + curl radius.
3.5 Limit Countersink Depth
Countersinks (for screws) are made with hand tools—don’t go too deep! Maximum depth =0.6x the material thickness (por exemplo, 3mm depth for 5mm thick brass). Também:
- Countersink holes: At least 3x material thickness from bends, 4x from edges, and 8x from each other.
3.6 Get Frills Right
Frills (rounded edge folds) have three designs—follow their rules:
- Open frills: Min inner diameter = material thickness; return length = 4x thickness.
- Teardrop frills: Min inner diameter = material thickness; opening = 1/4x thickness; running length = 4x thickness (after the radius).
3.7 Leave Space for Beveled Flanges
Bevels on flanges need room for bending tools. For a 3mm thick steel flange with a 45° bevel, leave a 5mm gap between the bevel and the bend—this prevents the tool from scraping the bevel.
3.8 Avoid Continuous Bending (If Possible)
Continuous bends (longo, unbroken curves) are hard to assemble to molds. If you must use them, make the middle section longer than the flange (por exemplo, a 100mm long bend on a 50mm flange needs a 60mm middle section).
3.9 Set Gaps for Notches & Tongues
- Notches: Distance from bend = (3x material thickness) + bend radius (por exemplo, 3x4mm + 4mm radius = 16mm gap).
- Tongues (peças interligadas): Space between tongues = max(1milímetros, espessura do material) (por exemplo, 4mm gap for 4mm steel, 1mm for 0.5mm aluminum).
3.10 Use Decompression Cuts
These cuts prevent tearing in tight bends:
- Width of cut = at least material thickness.
- Length of cut = longer than the bend radius (por exemplo, 5mm length for 4mm radius).
4. How to Calculate Bending Force
The right force ensures the metal bends without breaking. Key factors:
- Material’s flexural strength (por exemplo, mild steel S235 = 42 kg/mm²).
- Workpiece thickness (S, milímetros).
- V-mold opening (V, milímetros).
- Minimum internal edge (B, milímetros).
- Internal radius (Ri, milímetros).
Use this table for90° bends on mild steel S235:
| Espessura do material (S) | V-Mold Opening (V) | Minimum Internal Edge (B) | Internal Radius (Ri) | Approx. Bending Force |
|---|---|---|---|---|
| 2milímetros | 12milímetros (6xS) | 5milímetros | 2milímetros | 840 kg |
| 5milímetros | 30milímetros (6xS) | 12milímetros | 5milímetros | 2,100 kg |
| 8milímetros | 64milímetros (8xS) | 20milímetros | 8milímetros | 3,360 kg |
Formula Simplified: Force ≈ (Flexural Strength × S² × Length) / V
(Length = bend length in mm; use this for non-90° bends or other materials.)
5. Yigu Technology’s Perspective on Bending Design
Na tecnologia Yigu, we believe bending design is about “fabrication-first thinking.” Many clients come to us with designs that look good on paper but fail in production—like a 1mm bend radius on 5mm steel (it cracks!). We work with engineers to adjust designs early: por exemplo, a client making stainless steel medical trays needed a 2mm radius (instead of 1mm) and added 8mm gaps for holes—this reduced reworks by 40%. We also recommend leveraging Xometry’s automatic bending tech for high-precision parts (up to ±0.1mm tolerance). The best bending design isn’t just about specs—it’s about making sure your part is easy to make, durável, e econômico.
Perguntas frequentes: Common Sheet Metal Bending Design Questions
- P: Can I bend stainless steel and aluminum the same way?
UM: Não. Stainless steel has higher yield strength—use a larger V-mold opening (8x material thickness vs. 6x for aluminum) and more force. Por exemplo, 3mm stainless steel needs a 24mm V-opening, while 3mm aluminum uses 18mm. - P: How do I prevent springback (parts losing their angle after bending)?
UM: Use a slightly smaller angle than needed (por exemplo, 88° for a 90° part) and choose the right method. Fundição (high force) minimizes springback, enquanto air bending may need angle adjustments. - P: What’s the maximum bend angle I can achieve?
Most methods handle up to 180° (por exemplo, folding for 180° curls on a pan). For angles over 180°, usar rotational bending—it’s ideal for tight curves (por exemplo, 270° bends on a pipe clamp).