What Is Paper Machine Top Former

Paper Machine Top Former

The top former refers to adding a forming fabric above the forming table of foudrinier paper machine before the wet paper sheet is formed. The wet paper sheet passes between two layers of forming fabric, dehydrating the top and bottom sides of the paper web. At the same time, through the compression and hydraulic action between the two layers of forming fabrics, the fiber flocs are dispersed, reducing the fiber flocs in the wet paper sheet, improving the uniformity of the paper sheet, reducing the difference between the two sides of the paper sheet structure, and achieving the goal of significantly improving the quality of the paper sheet.

The current fourdriner paper machine has a large difference between the two sides of the paper, poor uniformity, high mesh load, and short mesh life. An efficient and energy-saving top former that does not require driving and has double-sided dewatering reduces the energy consumption of the wire section, improves the lifespan of the forming fabric, and comprehensively solves the disadvantages of large double-sided differences and poor uniformity in foudrinier paper machines. At the same time, the top wire increases the dewatering capacity of the wire section, greatly increasing the recycling level of white water in the forming  section. On the other hand, it solves the comtamitation caused by the discharge of papermaking white water and provides a new feasible way for zero discharge of papermaking white water.

Structure of Top Former

The top wire former is installed at an appropriate position on the upper part of the fourdrinier paper machine's wire table, consisting of an top forming roll, a bottom forming roll, a turning roll, an outlet roll, an inlet roll, a return roll, a correction roll, a tension roll, a water receiving basket, a suction box, a circular net, and a frame. The position and angle of the inlet,outlet and forming rolls can be adjusted according to actual needs, and the tension of the two wires can be adjusted to achieve the purpose of adjusting the dehydration distribution on both sides of the wire, optimizing the forming process, and improving uniformity.

Working Principle of Top Former

The wet paper enters the wedge-shaped area formed by the top and long webs from the long web section. The pulp layer is compressed in the wedge-shaped area, causing disturbance and dispersion of flocs, forcing them to quickly dehydrate. Then, it enters the clamping area between the lower forming rolls for further forced dehydration.

A doctor blade is installed inside the forming fabric in the clamping area. The white water that comes out of the top forming fabric falls into the water receiving basket and is discharged outside the machine through the doctor blade, while the white water that comes out of the bottom wire is scraped out by the lower blade and falls into the white water tray. A low vacuum board box and a moisture absorption box are installed under the bottom wire of the inlet wedge area to adjust the concentration of the pulp layer entering the wedge area. A vacuum suction box is installed under the bottom wire of the outlet wedge area to allow the suction and transfer of paper pages to follow the bottom wire. The water blade and the water receiving basket on the clamp area can be adjusted up, down, front and back. The forming roll and the wire guide roll are equipped with blade to remove water and fiber on the roll surface in a timely manner. The vacuum degree of the wet suction box and the water receiving tray is formed by a centrifugal exhaust fan, and the white water is discharged into the white water tank after passing through the separator.

In the top forming machine, due to the gradual reduction of the clamping area between the two wires in the forming area, the wet paper sheet is squeezed by the two wires, causing free water in the wet paper sheet to be squeezed out from both sides of the top and bottom mesh. As the spacing between the clamping areas gradually decreases, the squeezing effect continues to increase. In addition, the variable arc curve formed by the dewatering elements such as the forming roll greatly increases the dewatering rate of the top wire part. Experiments and production have shown that the top mesh device can remove 30-45% of the total water volume in the forming section, reducing the number of high vacuum suction box used. However, the top wire does not have transmission, resulting in a decrease in power consumption compared to traditional forming sections. At the same time, it can effectively increase the speed of the paper machine.