Draw wall wrinkling is one of the most common defects in metal stamping and deep drawing processes. It significantly affects both the appearance and functional performance of stamped parts.

Wrinkling typically occurs in areas where the sheet metal is insufficiently supported, making it more difficult to control compared to flange wrinkling.

This article explains the causes of stamping wrinkling, the role of process parameters, and how simulation can help optimize stamping die design.

Types of Wrinkling in Metal Stamping

In sheet metal forming, three main types of wrinkling are commonly observed:

• Flange wrinkling

• Draw wall wrinkling

• Elastic buckling due to residual stress

Among these, draw wall wrinkling is the most difficult to eliminate because the material is less constrained by tooling.

Causes of Draw Wall Wrinkling

Wrinkling occurs due to compressive stresses in the sheet metal during forming.

1. Insufficient Support in Draw Wall Area

In parts such as tapered square cups and stepped rectangular components, the draw wall is relatively unsupported, making it prone to instability and wrinkle formation.

2. Die Gap

Simulation results show that increasing the die gap significantly increases wrinkling severity.

Once wrinkles occur due to excessive die gap, they cannot be effectively eliminated simply by increasing blank-holder force.

3. Blank Holder Force

Blank holder force plays a critical role in controlling material flow:

• Too low → wrinkling occurs

• Too high → tearing and fracture

This creates a very narrow process window that is difficult to control in real production.

4. Uneven Material Flow

In stepped parts, wrinkling is often caused by unbalanced stretching between the punch and geometric transitions (such as step edges).

Simulation Analysis in Wrinkling Control

Finite-element simulation is widely used to analyze stamping defects and optimize die design.

In this study, a 3D finite-element method was used to evaluate the effects of process parameters on wrinkling behavior :contentReference[oaicite:0]{index=0}.

Simulation Setup

• CAD modeling using PRO/ENGINEER

• Rigid tooling assumption

• Shell element mesh for sheet metal

• Quarter-model symmetry for efficiency

Simulation Findings

• Larger die gap → increased wrinkling

• Blank-holder force alone cannot eliminate wall wrinkles

• Material flow imbalance is a key factor

The simulation results showed strong agreement with actual production data, validating the effectiveness of the method :contentReference[oaicite:1]{index=1}.

Engineering Solutions to Reduce Wrinkling

1. Optimize Die Gap

Maintain appropriate die clearance to avoid excessive material instability.

2. Control Blank Holder Force

Operate within a narrow range that balances wrinkling suppression and fracture prevention.

3. Improve Material Flow

• Adjust draw bead design

• Modify geometry transitions

• Enhance stretching in unsupported areas

4. Use Simulation Tools

Applying CAE tools early in the design stage helps predict defects and reduce trial-and-error.

See also CAE analysis in stamping.

Engineering Insight

In practical stamping production, wrinkling is rarely caused by a single factor. Instead, it results from the interaction between die design, material properties, and process parameters.

Experienced engineers focus on balancing these factors rather than relying on a single adjustment such as increasing blank-holder force.

Conclusion

Draw wall wrinkling is a complex defect that requires careful control of die design and process parameters. Finite-element simulation provides an effective tool for predicting and eliminating such defects.

At Changdong Tool & Die, we apply CAE simulation and advanced die design techniques to optimize material flow and eliminate stamping defects such as wrinkling, ensuring stable production and high-quality parts.