Sheet Metal Bending Guide Aims to Cut Costs Boost Efficiency

Imagine a meticulously designed sheet metal enclosure rendered useless by a minor bending error. This scenario highlights the critical importance of bending design in sheet metal fabrication—a process that directly impacts product quality, cost efficiency, and performance. This article examines fundamental bending design principles to help engineers avoid common pitfalls and achieve superior results.

Sheet metal bending involves plastic deformation of metal sheets using a press brake with upper punch and lower V-die tooling. This process enhances structural integrity by improving strength, rigidity, and stress distribution while enabling complex geometries. For instance, curved designs significantly increase load-bearing capacity in components.

Effective sheet metal modeling requires careful consideration of three fundamental parameters: material thickness, bend radius, and bend allowance.

Consistent material thickness is essential as components are fabricated from single metal sheets. Standard processing accommodates thicknesses from 0.9mm to 20mm, with thinner materials (<3mm) classified as sheet metal and thicker materials (>3mm) as plate. Actual tolerances vary based on specific part requirements.

The minimum bend radius should equal the material thickness to prevent cracking or deformation. Maintaining consistent bend directions within the same plane reduces repositioning needs, saving time and costs. Uniform bend radii across a component also lower manufacturing expenses.

During bending, the neutral axis shifts inward. The K-factor—representing the ratio of neutral axis position (t) to material thickness (T)—calculates required material compensation. The following table provides K-factor references for various materials and bending methods:

Bend reliefs—small notches at bend junctions—mitigate stress concentration that could otherwise distort adjacent features. Though small, these features are critical for preventing deformation in holes and slots.

Without proper relief, edge-adjacent bends risk tearing and manufacturing failures. Relief notches should measure at least the material thickness in width and exceed the bend radius in length.

Flanges—comprising a face and connecting bend—require appropriate relief types when not adjacent:

• Oval Relief: Rounded ends distribute stress evenly, particularly beneficial near holes/slots by minimizing feature distortion through controlled material movement.
• Rectangular Relief: Simplified cutting requirements make this cost-effective for designs with moderate bend radii and standard material thicknesses.

Specialized edge features enhance component performance, with hemming and seaming being primary examples.

Hems—hollow rolled edges—strengthen components while eliminating sharp edges. Optimal hem design requires:

• External radius ≥ 2× material thickness (varies by manufacturer)
• Bend position ≥ 6×(hem radius + material thickness) from hem feature

Seams—U-shaped folded edges—provide structural reinforcement and assembly capabilities. Three primary types exist:

• Open Seam: Features slight clearance (minimum internal radius = material thickness; return length = 4× thickness)
• Closed Seam: Tightly folded (minimum internal radius = material thickness; return length = 6× thickness)
• Tear-Drop Seam: Balances strength and flexibility (minimum internal radius = material thickness; return length = 4× thickness)

Features near bends risk deformation during forming. Recommended minimum distances:

• Hole edge to bend: ≥ 2.5× material thickness (T) + bend radius (R)
• Slot edge to bend: ≥ 4× material thickness (T) + bend radius (R)

Features near edges may cause bulging. Maintain minimum clearance of 2× material thickness between extruded holes and component edges.