Pneumatic Hemming Die for High-Precision Sheet Metal Flattening

Pneumatic Hemming Die for High-Precision Sheet Metal Flattening

Both spring-loaded and pneumatic hemming dies are designed to perform the same basic task: flattening a pre-bent sheet metal edge. However, when the dimensions of the flattened section require tighter control, the movement and guidance of the lower die become especially important.

For this application, WYS Machinery manufactured a pneumatic hemming lower die system designed for higher-precision sheet metal flattening.

Why Use a Pneumatic Hemming Die?

In a conventional spring-loaded hemming die, clearance is required between the moving and fixed sections so that the mechanism can operate properly. This clearance can allow a small amount of lateral movement during the hemming process.

For general applications this may be acceptable, but it can introduce dimensional variation when tighter tolerances are required.

The pneumatic design uses an air-controlled mechanism to guide the moving section vertically with minimal lateral play. This provides more stable movement and helps improve the dimensional accuracy and consistency of the flattened section.

Pneumatic vs. Spring-Loaded Hemming

Both structures can be effective depending on the application.

A spring-loaded hemming die provides a practical solution for general sheet metal hemming where standard dimensional tolerances are acceptable.

A pneumatic hemming die is better suited to applications where the hemmed dimension requires tighter and more repeatable control.

The appropriate structure should therefore be selected according to the workpiece, material, production requirements and dimensional tolerance.

Lower Die Base and Die Configuration

The tooling shown here is the pneumatic lower die base, which can be combined with a corresponding Double-V lower die to form a complete pneumatic hemming lower die assembly.

If a different configuration is required, WYS Machinery can also modify the design to work with a Single-V lower die or other customized die structures.

Custom Tooling Interfaces

The pneumatic hemming system can be engineered according to the customer's press brake and tooling requirements.

Custom mounting configurations can be developed for different tooling systems, including TRUMPF Type, WILA Type, BYSTRONIC Type and LVD Type interfaces.

Customers can provide their workpiece drawings, material thickness, required hem dimensions and machine tooling interface, allowing our engineering team to develop a suitable hemming solution.