NRC Kraft Thermal Paper Slitting Machine

Kraft paper slitting rewinding machine is designed to transform large, master ("jumbo") rolls of kraft paper into narrower, smaller-diameter rolls that are ready for use in various industries like packaging, printing, and converting.

Main parts

1. Unwind Stand

   • Type: Heavy-duty, capable of handling the significant weight of a full kraft paper roll. Shaftless unwind stands are common for

     operator safety and ease of loading.

   • Feature: Often includes a pneumatic or magnetic brake to control the unwinding tension, preventing the web from running loose

     or snapping.

2. Tension Control System

   • Critical for: Preventing wrinkles, ensuring consistent roll hardness, and avoiding web breaks.

   • How it works: Uses dancers or tension sensors to provide feedback to the drive system, maintaining a consistent pull on the

     paper throughout the process.

3. Slitting Section (The Most Critical Choice)

   • Shear Slitting is the Standard for Kraft Paper.

     • How it works: Uses two opposed circular blades—a top "male" blade and a bottom "female" blade—that work like scissors for a

       clean, precise cut.

     • Why it's best for kraft:

       • Clean Edge: Produces a burr-free, dust-minimized edge, crucial for high-quality printing and bag-making.

       • Handles Thickness: Effectively cuts through heavy-weight and multi-ply kraft.

       • Durability: Carbide-tipped shear blades resist the abrasive nature of kraft paper far better than razor blades.

     
     

4. Web Guide System

   • Purpose: Ensures the web enters the slitting section perfectly straight. This is vital to prevent diagonal slitting, which ruins the entire roll and creates waste.

5. Spreader Rollers

   • Purpose: Located after the slitting knives, these bowed or angled rollers gently spread the narrow strips apart. This prevents the strips from rubbing against each other and ensures they wind onto the core in perfect alignment.

6. Rewind System

   • Type: Center-Surface Winder (Drum Winder) is very common for kraft paper.

   • How it works: The new rolls are wound against a large, driven drum. This provides surface support, ensuring very tight and dense rolls—a key requirement for kraft paper used in automated packaging machinery.

   • Alternative: Center Winders are used when precise tension control is paramount for more delicate kraft-based laminates.

7. Drive and Control System

   • A modern PLC (Programmable Logic Controller) and touchscreen HMI allow the operator to set all parameters: line speed, tension, roll length, and diameter.

   • Automatic Taper Tension: A crucial software feature that gradually reduces tension as the rewind roll gets larger, preventing the core from being crushed or the outer layers from damaging the inner ones.