The overfeed rewinder, which feeds paper from the top, serves the purpose of slitting and rewinding jumbo heavy paper rolls. When dealing with low-gram weight paper, the process typically involves two steps: longitudinal cutting and unwinding, followed by slitting and rewinding. Our factory, QINGDAO JIERUIXIN Machinery and Technology Co., Ltd., has successfully employed a 1575mm overfeed rewinder to slit and rewind 26~30g/m2 lightweight coated (LWC) paper after more than a year of testing. The product has proven to meet rewinding requirements, reduce operational steps for rewinding and slitting, and enhance the yield rate.

For our 1575mm overfeed slitting rewinder, the original design of the paper feeding route line and the contact situation between the paper roll and the bottom roller are illustrated in the figure below:

Figure: Schematic diagram of contact between paper roll and bottom roller

As the paper web enters the longitudinal slitting device through the overfeed rewinder, the slitting device moves vertically with the increasing diameter of the paper roll. The slitting device presses on the paper roll, and the paper roll exerts pressure on the two bottom rollers, driven by friction with the paper roll. The 4% speed difference between the front and rear bottom rollers allows for tighter and harder rolling of the paper roll, beneficial for rewinding thick paper. However, when rewinding LWC paper, issues such as cracking, bursting, and wrinkling of the paper web may arise. To address this, the following improvements have been implemented:

1. The rewinder device frame has been moved forward by 9mm, from 162.5mm to 153.5mm. This adjustment ensures that the paper roll is only in contact with the front bottom roller and completely separated from the rear bottom roller. Consequently, the paper roll undergoes only one friction, resulting in a looser roll less prone to cracking and wrinkling.
2. The use of a heavy hammer and control of line pressure have been optimized. Adequate line pressure is crucial, as too little pressure may lead to loose, deformed, wrinkled, and folded lines. Conversely, excessive line pressure may cause tight coils, leading to cracking and knife marks on the surface. It is advisable to maintain line pressure between 0.6~0.7kg/cm.

3. During the initial rewinding of the paper roll, when it is small and light, the unwinding brake should be tightened to increase the tension of the paper web, preventing wrinkles. As the paper roll size and weight increase, gradually release the brake to adapt to the changing tension requirements for paper roll tightness and consistency between the inside and outside.

   

Through the aforementioned improvements and controls, the longitudinal slitting device of the paper machine has been eliminated, and a rewinder has replaced two slitting machines. This modification allows for the production of multiple 26-30g/m2 thin paper reels through a single slitting and rewinding machine, achieving a yield rate of over 90% and ensuring good rewinding quality.