The overfeed rewinder (feeding paper from top) is a device for slitting and rewinding jumbo heavy paper rolls. While slitting the low-gram weight paper, it is generally divided into two steps:after longitudinal cutting and unwinding, then slitting and rewinding. There is an overfeed rewinder machine that can be used to replace the longitudinal cutting device and slitting machine, so as to directly slit and rewind LWC paper below 30g/m2. After more than a year of testing, our factory, QINGDAO JIERUIXIN Machinery and Technology Co., Ltd., finally used the 1575mm overfeed rewinder to slit and rewind 26~30g/m2 web paper successfully. It turns out that the product meets the rewinding requirements, and the operating procedures of rewinding and slitting were reduced, and the yield rate was improved.

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 shown as in the figure below:

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

The paper web enters the longitudinal slitting device through the overfeed rewinder, and the slitting device moves vertically as the diameter of the paper roll increases; the slitting device presses on the paper roll, and the paper roll presses on the two bottom rollers,driven by friction with the paper roll. Due to the 4% speed difference between the front and rear bottom rollers (the bottom roller is the driving roller, the front bottom roller is faster than the rear bottom roller), the paper roll can be rolled tighter and harder, which is beneficial for rewinding thick paper. While for rewinding LWC paper, it is prone to cracking, bursting and wrinkling of the paper web. To this end, we have made the following improvements:

1.Move the rewinder device frame forward 9mm, that is to changed 162.5mm as 153.5mm, there to the paper roll also moves forward by 9mm, so that the roll is only in contact with the front bottom roller and completely separated from the rear bottom roller. In this way, the paper roll is only subject to once friction, and the rolled out paper roll is looser and less likely to crack and wrinkle.

2.Use a heavy hammer well and control the line pressure. If the pressure is too small, the line will become loose, deformed, wrinkled, and folded. To the contrary, if the line pressure is over high, and the coil is too tight, which is prone to cracking, and making a knife mark on the surface.It is advisable to control the line pressure between 0.6~0.7kg/cm.

3.When the paper roll is rewindered at first, it is small in size and weight, and the pressure acting on the bottom roller is also small, so as the friction force.The unwinding brake should be tightened to increase the tension of the paper web and make the paper roll tight to avoid wrinkles. As the paper roll increases, the pressure acting on the bottom roller increases, and the friction force also increases. As the paper roll gradually tightens, it is necessary to gradually release the brake and reduce the tension of the paper web to adapt to the requirements of paper roll tightness and consistency between the inside and outside.

Summary

Through the above improvements and controls, the longitudinal slitting device of the paper machine has been cancelled, and a rewinder has been used instead of two slitting machines. It can produce multiple 26-30g/m2 thin paper reels through one slitting and rewinding machine, with a yield rate of over 90% and good rewinding quality.