What is forming fabric？

What is Forming Fabric?

As the "skeleton" of paper forming, the forming fabric is also an important dewatering equipment in the wet section of the paper machine. It will directly affect the quality and production efficiency of paper. The tasks of the forming fabric in the papermaking process are as follows:

(1) Dewatering and forming: In the wet section of the paper machine, the pulp is quickly dehydrated through the forming fabric, so that the fibers are evenly distributed to form wet paper sheets.

(2) Support and transportation: The forming fabric acts as a transmission medium from the headbox to the press section, and can withstand high pressure and stable transportation to avoid wet paper breakage or deformation.

(3) Improve paper quality: The surface structure of the forming fabric will affect the flatness and strength of the paper.

Working Principle of Forming Fabric

The pulp from the headbox will be sprayed onto the high speed running forming fabric, and the initial shaping of the paper will be completed through gravity dehydration, vacuum suction and other processes, and finally become a continuous paper web.

Sun Hong's forming fabric is made of high performance polyester monofilament material. The mainstream includes polyester monofilament forming fabric and multi layer composite fabric (such as 1.5 layer and 2.5 layer structure). Multi layer composite fabric can effectively optimize dehydration efficiency and paper quality.

How to Choose Forming Fabric?

Key factors for selecting forming fabrics: paper type, gram weight, paper machine speed, width and other information to select the model of forming fabric, which will directly affect the quality, production cost and economic benefits of paper.

Forming fabrics are commonly used as equipment in papermaking production. They are most commonly used for dehydration, shaping and transportation support of paper sheets. The specifications and technical requirements of papermaking forming fabrics are distinguished by width, length, weaving method, mesh number, etc. Generally, the thinner the paper is, the more meshes are selected.

The 4 shelf series single layer forming fabric is suitable for making cultural paper, printing paper and packaging paper.

The 5 shelf series single layer forming fabric is suitable for making sanitary paper, cultural paper and packaging paper.

The 8 shelf series single layer forming fabric is suitable for making paper bags, kraft paper, linerboard, corrugated paper, boxboard, etc. with large quantitative weight.

The 7 shelf series double layer forming fabric is suitable for making high grade printing paper, thin paper, etc.

The 8 shelf series double layer forming fabric is suitable for making surface pulp and lining pulp of high-grade printing paper, offset printing paper, thin paper and board paper.

The 8 shelf and 16 shelf 2.5 layer forming fabric is suitable for making high speed papermaking machines and producing various types of paper.

Common Problems of Forming Fabric in Papermaking

The performance of the forming fabric will also decline due to wear and blockage after long term operation. Next, Sun Hong will briefly explain the common problems and solutions of the forming fabric

(1) Wear on the surface of the forming fabric

When the surface of the forming fabric is partially or completely thinned, broken, or stripes and holes appear on the surface of the paper. This phenomenon may be caused by friction of hard impurities in the pulp, vacuum dehydration box, excessive scraper pressure, and insufficient wear resistance of the forming fabric material.

Solution:

Optimizing raw material filtration and installing high precision slag removers can effectively reduce pulp impurities.

Adjust the dehydration pressure and the vacuum degree according to the pulp concentration to avoid excessive squeezing.

Upgrade the forming fabric material. Choose a wear resistant multi layer forming fabric. (For example: a forming fabric with a 2.5 layer or triple layer composite structure)

(2) Blockage of the forming fabric

The forming fabric partially turns black, the dehydration efficiency decreases, the water content of the paper is high, and the permeability of the forming fabric cannot be restored after cleaning. This is probably caused by fine fibers and colloids adhering to the inner wall of the forming fabric or infrequent cleaning and improper selection of cleaning agents.

Solution:

Regular high pressure flushing is required. It is recommended to use 60-80 degree hot water and neutral detergent to flush the forming fabric surface each time.

Chemical cleaning can also be performed. For resin blockage, soak it with an alkaline cleaning agent of PH10-12.

(3) Deviation of the forming fabric

Deviation of the forming fabric should be handled in time, otherwise it will cause damage to the forming fabric. There may be changes in the positions of various rollers, incorrect vacuum box position, uneven vacuum degree, inconsistent sizing concentration and amount, etc.

The deflection of the forming fabric is generally adjusted by the correction roller. The net guide rule is which side of the advancing net first contacts the correction roller, then the net will move to this side.

If the deviation of the forming fabric is ineffective with the correction roller, the following methods can be used to deal with it:

(1) Reduce the vacuum degree of the vacuum box.

(2) Tension the net. Both methods can enhance the effect of the correction roller.

(3) If these two methods do not work, use the tensioning roller for adjustment.