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Bending limits of different metals in sheet metal bending

Release time:

2025-05-15

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Abstract

1. Minimum Bending Radius for Different Sheet Metal Bending Metals

The minimum bending radius (inner radius) determines whether the material is prone to cracking during bending, mainly affected by the material's ductility and hardness:

Material Type	Minimum Bending Radius (Inner)	Typical Applications
Mild Steel (e.g., SPCC, 08F)	0.4t (t is the material thickness)	Automotive frames, household appliances
Carbon Steel (Q235, 15F)	0.5t	Structural parts, mechanical housings
Stainless Steel (0Cr18Ni9, 304)	0.5t~1.0t	Medical equipment, chemical containers
Aluminum Alloy (1100-H24, T2)	0.4t~0.6t	Aerospace, lightweight equipment
Copper (Pure copper, brass)	0.4t~0.6t	Electronic heat sinks, precision parts
Titanium Alloy	0.6t~1.0t	Medical devices, sports equipment
High Carbon Steel (45#, 65Mn)	1.0t~2.0t	Springs, high-strength parts

Sheet Metal Bending Precautions ：

If the design requires a smaller bending radius (<0.4t), it needs to be done through Slotting or Annealing to reduce material hardness.
For stainless steel and titanium alloys, due to their higher hardness, it is recommended to use Step Bending or Hot Bending processes.

2. Bending Factor and Development Length Calculation

The bending factor (K value) affects the development length (L), and the K value varies significantly for different materials:

Material	K value (90° bend)	Development Formula	Example (t=2mm)
Iron Plate	1.8t	L = A + B - K	L = A + B - 3.6mm
Aluminum Plate	1.6t	L = A + B - K	L = A + B - 3.2mm
Stainless Steel	1.7t~2.0t	L = A + B - K	L = A + B - 3.4~4.0mm
Copper Plate	1.5t~1.8t	L = A + B - K	L = A + B - 3.0~3.6mm
Titanium Alloy	1.6t~1.8t	L = A + B - K	L = A + B - 3.2~3.6mm

Sheet Metal Bending Formula Explanation ：

L : Development length (total length of the sheet metal before development).
A, B : The outer dimensions of the two sections after bending.
K : Bending deduction value, related to material thickness and V-groove width (V-groove is usually 6~8 times the plate thickness).

3. Bending Limit Dimensions

The bending limit dimensions of different metals (such as minimum edge height, maximum counter-bend size) are limited by the mold and material characteristics:

(1) Minimum L-shaped edge size (Lmin)

Formula : Lmin = (V/2) + 2 + t
- V : Width of the lower mold V-groove (usually 6~8 times the plate thickness).
- Example : When t=2mm, V=12mm, then Lmin = 6 + 2 + 2 = 10mm。

(2) Z-shaped edge center height (Hmin)

Formula : Hmin = (V/2) + 2.5 + 2t
- Example : When t=2mm, V=12mm, then Hmin = 6 + 2.5 + 4 = 12.5mm。

(3) Maximum counter-bend size (Lmax)

Formula : Lmax = 59 + t
- Example : When t=2mm, Lmax = 59 + 2 = 61mm (Limited by the height of the lower mold).

(4) Minimum width of U-shaped edge (H1)

Formula : H1 = 12 + 2t
- Example : When t=2mm, H1 = 12 + 4 = 16mm (Limited by machine travel).

4. Special Material Bending Precautions for Sheet Metal Bending

(1) Aluminum Alloy

Characteristics : Good ductility, but easy to spring back (springback is approximately 2°~5°).
Process Suggestions : Use Overbending Method (e.g., bending to 93° then springing back to 90°) or Elastic Compensation Die 。

(2) Stainless Steel

Characteristics : High hardness, strong work hardening tendency, prone to cracking.
Process Suggestions ：
- Use Blunt Angle Die (R≥0.5t).
- Before bending, perform Annealing (e.g., annealing 1Cr18Ni9 can reduce hardness).

(3) Titanium Alloy

Characteristics : High strength, corrosion resistance, but high cost.
Process Suggestions ：
- Control bending temperature at 150°C~200°C (Hot bending reduces the risk of cracking).
- Use Special Die (Avoid materials that react with titanium, such as graphite-coated steel).

(4) Copper and Copper Alloys

Characteristics : Good conductivity, but prone to sticking to the die.
Process Suggestions ：
- Apply a Anti-stick Coating (such as Teflon) to the die surface.
- Control bending speed at 0.5m/s or less (Reduce frictional heat).

5. Common Problems and Solutions in Sheet Metal Bending

(1) Bending Cracks

Cause : Bending radius too small, high material hardness.
Solution ：
- Increase bending radius (≥0.5t).
- Anneal stainless steel/titanium alloy.

(2) Hole Deformation

Cause : Hole located in the bending deformation zone.
Solution ：
- Hole edge distance ≥2t + R (R is the bending radius).
- Before bending, process Shallow Groove (depth ≤0.3t) at the edge of the hole.

(3) Springback

Cause : Elastic recovery of the material (e.g., springback of carbon steel is approximately 5°~10°).
Solution ：
- Use Overbending Method (e.g., bending to 95° then springing back to 90°).
- Use Elastic Compensation Die (Automatically adjust the angle).

6. Sheet Metal Bending Reference Standards and Tools

National Standard ：
- GB/T 235-2013 : Test method for repeated bending of metal sheet.
- YB/T 5349 : Test standard for mechanical properties of metal bending.
Design Tools ：
- Development Coefficient Table : Baidu Wenku provides development coefficients for different materials (e.g., K=1.8t for iron plate).
- 3D Modeling Software : Use SolidWorks/UG built-in sheet metal module to simulate bending limits.

Sheet Metal Bending The bending limit parameters of different metals need to be considered comprehensively in combination with material properties, die design and process requirements. For high-precision requirements or special materials (such as titanium alloy, stainless steel), it is recommended to use Process Verification or Die Simulation Optimization design to ensure process feasibility and product quality.

Key words:

PT cabinet function and composition

Key points of sheet metal bending

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