Unwinding

Unwinding is the first stage of the slitting process, during which the parent roll is fed into the machine. The material must unwind at a stable speed and tension so it can enter the next section smoothly.

Web Guiding

Web guiding keeps the material aligned as it moves through the machine. This supports more accurate slitting and reduces the chance of the web shifting during production.

Slitting

Slitting is the actual cutting stage in which wide material is slit into narrower widths. The slitting result depends on the blade setup, material type, machine speed, and slitting method.

Rewinding

After the material is slit, the slit rolls are rewinding onto separate cores. Stable rewinding tension and pressure help produce rolls with even edges, suitable hardness, and good roll shape.

Uneven Roll Edges (Telescoping/Coning)

Uneven roll edges happen when the finished roll doesn't wind evenly from side to side. The roll may shift outward in a telescope-like shape or form a cone shape instead of a straight roll.

This problem is usually related to the rewinding section. Common causes include improper rewind tension settings, unbalanced torque on the differential shaft, or air trapped between material layers during rewinding.

To improve uneven roll edges, manufacturers can:

• Adjust the taper tension so that the winding tension changes as the roll diameter increases
• Optimize differential shaft settings to balance torque between rolls
• Improve air removal with a lay-on roller or pressure roller during rewinding

For more precise control, load cells can be added to the rewinding section for automatic tension compensation. Load cells measure tension changes during rewinding, so the machine can adjust automatically rather than relying on fixed settings.

Yo Den can configure up to several control points, helping create a more precise and stable tension curve.

Burrs or Rough Edges

Burrs or rough edges are usually a sign that the blade is not slitting the material cleanly. The edge may look uneven, frayed, or slightly torn, which can affect the appearance of the finished roll and create processing problems down the road.

Generally, this happens because of dull blades, insufficient blade overlap, or an incorrect slitting method for the material.

Manufacturers can solve this problem by:

• Replacing or sharpeningblades regularly
• Reset the knife clearance
• Selecting the right slitting method based on material type.

Shear slitting is often used when a cleaner, more precise edge is required, while razor slitting is more suitable for thinner films. The best method depends on the material's thickness, structure, and edge quality requirements.

Excessive Dust Generation

Dust is more than a cleanliness issue in production. It can build up on the machine, affect finished roll quality, and cause problems in later processing.

Excessive dust generation usually happens when the cutting process creates too much friction against the material, the knife pressure is set too high, or the materials are too brittle and break apart during cutting.

To reduce dust generation, manufacturers should:

• Use shear slitting when the material requires a cleaner cut
• Reduce knife pressure to lower friction and avoid crushing the material edge
• Add dust collection equipment, such as suction devices or dust extraction systems, near the cutting section

Wrinkles During Slitting

Wrinkles usually point to a web-handling problem. Tension fluctuations, roller misalignment, or poor web spreading can cause folds to appear before or during slitting. These wrinkles can then carry into rewinding and affect the finished roll.

When wrinkled material is rewound, it can create uneven roll hardness, poor roll shape, trapped folds, or unstable edges.

Some practical ways to improve this problem include:

• Stabilizing tension in each tension zone so the material moves through the machine more evenly
• Correcting roller parallelism to prevent the web from being pulled unevenly
• Adding a spreader roller to help flatten the web before it reaches the slitting section

Roll Blocking or Adhesion

Roll blocking is a common problem where material layers stick together inside the finished roll. When layers don't separate properly, the roll doesn't unwind smoothly in the next process, potentially damaging the material surface.

Excessive pressure during rewinding can press the layers too tightly together, while heat buildup may make the material more likely to adhere to itself. Some film surfaces are also naturally more sensitive to blocking.

Manufacturers can try to reduce roll blocking and adhesion by:

• Reducing rewind pressure to avoid over-compressing the roll
• Controlling temperature rise during production
• Using anti-blocking or release materials when needed