Die Clearance

A correct die clearance is required for an optimal shearing effect, high cutting quality and long serviceable life of the tools. The required die clearance depends on the shear strength and the thickness of the sheet.

SEQUENCE OF A PIERCING PROCESS

1. The tool is mounted to a press of a piercing bow.
2. The upper tool with the cutting punch is moved towards the workpiece by the drive.
3. The spring-mounted stripper clamps on the piece part, the springs are compressed.
4. The cutting punch touches the part, the drive further builds-up the force.
5. The cutting punch penetrates into the sheet. The penetration depth depends on the material characteristics and the thickness of the piece part along with optimal die clearance.
6. The piercing slug breaks through into the die and causes the sudden release of the driving system energy. This release of pressure is called “cutting impact”.
7. The punching slug is discharged.

A good cut quality of the tool depends on:

• The kind of tool guidance
• The size of the die clearance
• The kind of coating of the cutting element

The design configuration and operating mode of a cutting tool have a decisive influence on the production result. Among others, a differentiation is made according to their type of guidance. There are three essential types of guidance for cutting tools.

1. Free cutting tools.
2. Column-guided or guided upper tools - rams through guide rail/guide carriage.