Sheet metal design for manufacturability (DFM) is essential for reducing production cost, improving quality, and ensuring stable stamping processes.

Proper stamping design guidelines help engineers avoid common defects such as cracking, wrinkling, distortion, and excessive tooling wear.

This guide summarizes key rules for bends, holes, embossing, flanges, and other critical features in metal stamping design.

Bending Design Rules

• Minimum bend radius ≥ 0.5× material thickness or 0.8 mm

• Multiple bends should be in the same direction when possible

• Avoid large parts with very small flanges

Proper bending design reduces cracking and improves dimensional consistency.

Hole Design Guidelines

• Minimum hole diameter ≥ material thickness

• Distance from hole to bend ≥ 2× thickness + bend radius

• Distance from hole to edge depends on geometry and thickness

Incorrect hole placement can lead to distortion or tearing during forming.

Countersinks and Counterbores

• Minimum spacing between features ≥ 8× thickness

• Distance to edge ≥ 4× thickness

• Maintain at least 50% hardware contact

These features require sufficient material support to prevent deformation.

Embossing and Dimples

• Emboss depth depends on thickness and radius

• Dimple diameter ≤ 6× thickness

• Maintain proper spacing from holes and edges

These features improve stiffness but must be carefully designed to avoid stress concentration.

Flanges and Hems

• Minimum flange height depends on thickness and bend radius

• Hem return height ≥ 4× thickness

• Avoid closed hems where fracture risk is high

Proper flange design ensures strength and assembly performance.

Extruded Holes and Threads

• Minimum spacing between extrusions ≥ 6× thickness

• Distance to edge ≥ 3× thickness

Extruded holes are commonly used to increase thread engagement in thin sheet metal.

Lances and Special Features

• Minimum width ≥ 2× thickness

• Maximum length ≤ 5× width

• Maintain sufficient distance from bends and holes

Improper lance design can lead to tool breakage or part deformation.

Stock Utilization and Layout Considerations

Efficient material usage is critical in metal stamping manufacturing:

• Design parts for tight nesting

• Reuse scrap material where possible

• Coordinate with strip layout design

See also progressive die design.

Engineering Insight

In real production, most stamping issues are not caused by machine limitations but by poor part design.

Designing with manufacturability in mind reduces:

• Tooling cost

• Production defects

• Lead time

Conclusion

Sheet metal DFM is a key factor in successful stamping production. By following proper design guidelines, engineers can achieve better quality, lower cost, and more efficient manufacturing.

At Changdong Tool & Die, we support customers in optimizing sheet metal part design for manufacturability. Our engineering team helps reduce tooling cost, improve production efficiency, and ensure high-quality stamping results.