The headbox in bank note and security paper production serves several critical functions:

1. Stock Distribution: It evenly distributes the pulp suspension across the machine width to ensure uniform sheet formation.

2. Velocity Control: The headbox controls the velocity of the stock jet to match the wire speed, crucial for proper web formation.

3. Pressure Regulation: Maintains consistent pressure to ensure stable operation and uniform basis weight distribution.

4. Fiber Orientation: Helps align fibers properly through precise control of turbulence and flow characteristics.

5. Consistency Management: Provides uniform stock consistency by minimizing fiber flocculation and preventing segregation.

6. Jet Angle Control: Allows precise adjustment of the stock jet angle for optimal sheet properties.

7. Profile Control: Equipped with actuators to maintain cross-directional profile uniformity.

8. Contaminant Removal: Often includes cleaning systems to prevent debris from affecting paper quality.

9. Security Features Integration: In security paper production, allows for precise incorporation of special fibers or features.

These functions are vital for producing high-quality banknotes and security papers with consistent physical properties and security characteristics.