For example, if the brake or motor is undersized, the roll inertia can drive the web materials into slackness at deceleration.Ģ) In slitting draw zone, the tension will follow the unwind tension. Besides, roll inertial torque is another factor, diameter is needed to calculate inertial torque during acceleration and deceleration. The torque applied at the core is transmitted through the radial layers of roll, and futher to produce tension at outside of the roll.Ĭonstant tension is important for unwind porcess, a constant shaft torque will create an increasing tension as the roll diameter decreases, so the torque needs to be varied proportional based on the variation of roll diameter. Each zone is unique and should be controlled independently, that means each zone may have its own tension level.ġ) In unwind zone, an unwinding roll generally is controlled by brake or motor attached to the shaft or core chuck. Most slitting and winding applications include these three types of zones. Tension zones are commonly categorized as unwind, slitting draw, and rewind. Tension zones: unwind, slitting draw, rewind This widening of the web width can cause wrinkles to occur. Materials will shrink in the machine direction and web width will widen in the cross machine direction. When tension is too low, web materials can wrinkle in nips, wrap rollers or cause many other types of troubles. Even worse, high tension breaks will cause the machine to be shut down, rethreaded, restarted and equilibrium be re-established. This narrowing of the web width can cause wrinkles to occur.
Materials will stretch in the machine direction and compress in the cross machine direction. When tension is too high, web materials may bend, break or neck. Improper tension can cause many material faults such as telescoping rolls, roll blocking, crushed cores, material wrinkles, web stretching, etc. On the other hand, different tension level is required in each individual area, you need to isolate and manage it. Importance of web tensionĪt both rewind and unwind stations, proper tension is necessary to a web so it can be handled through the machine and processes without overstretching. Proper tension is required to reduce waste and downtime, and it’s critical to produce high quality materials including paper, film, foil, rubber, plastic, linoleum, etc. Driven rollers can give operator some control over the tension, and undriven rollers can also change the tension because of effects including the drag of bearings and resistance to speed changes. Web tension is the force applied to a continuous web of material in slitting and winding process.
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