Winding requirements

1. At the start of a reel, sufficient sheet tension must be applied to develop a firm core.
—if this precaution is not taken, slack turns adjacent to the core will flatten out when the running tension is subsequently applied causing the roll to become out-of-round.
2. In the winder, winder drums support the roll weight, the weight being split into two components at the nip points.
— the higher the nip pressure becomes, the harder the roll becomes.
— as the roll becomes larger and heavier, the specific nip pressures grow.
— if these conditions are not compensated for, the roll becomes increasingly hard, resulting in roll damage due to splitting.
3. The specific nip pressure between the carrier drums and rewound roll varies inversely as the diameter of the carrier drums, since with larger drums, the weight load is spread over a greater area.
— compensation for the nip pressure as the roll diameter increases may become less critical.
— consequently, uniform density in the rewound roll can be more readily attained.
4. Reduced to its elements, the problem of web tension amounts to the following; when the web has been threaded up on the winder and the carrier drums have begun to revolve, a steady pull is exerted on the web, causing it to unwind from the parent roll on the backstand.
— once inertia of the parent roll is overcome, it revolves freely in the absence of any restraint, thereby reducing web tension to zero as soon as the carrier drums cease to accelerate.
— any deceleration of the carrier drums leaves the parent roll revolving due to its own momentum, paying out excessive quantities of paper and ruining the operation.
5. Excessive web tension at any stage of the winding cycle can cause splitting or breaking of the sheet after it is wound onto the roll.
— too great a tension may distort the sheet by stretching it beyond its elastic limit.
6. Insufficient tension can lead to a soft and “mushy” roll that is apt to telescope or become out-of-round in handling.
— insufficient tension may be responsible for poor slitting and troublesome run-in of the slit webs.
— during acceleration or deceleration, insufficient tension can produce lateral or longitudinal wrinkles.
7. Varying web tension during the winding cycle can cause crepe wrinkles, offsetting and starring of the rewound roll.
8. Control of parent roll sheet tension largely controls the quality of the rewound roll produced.
— at the start of a reel, high sheet tension should be induced to develop a hard-centered roll.
9. Maximum winding speed should be attained as soon as possible.
— maximum speed should be maintained until the parent roll is running near to the reel shell.
— the speed should then be gradually reduced when the rewound rolls are almost up to full diameter and increased braking should be applied to ensure that the sheet remains tight until the winder drums are stationary.
— it is important to slow down the winding speed gradually, as it will otherwise be difficult to control the brake and maintain sufficient tension to prevent overrunning of the parent roll.