It is customary to divide the paper machine into long net, round net, clamping net and long net mixing according to the type of paper shaper used; it is also divided into newsprint machine, cultural paper machine, capacitor paper machine according to its main product varieties; or it is divided into thin paper machine, cardboard machine and conventional paper machine according to the thickness of paper production.

　　According to the needs of the papermaking process, the paper machine has various structures, generally consisting of conveying, forming, pressing, drying, finishing, coiling and transmission components and auxiliary systems.

　　Forming part

　　It is composed of headbox, chest roll, forming net, suction tank and volt roll. Headbox pulp distributor sprays the pulp from the conveying system evenly to the forming net, and the pulp speed matches the net speed. Controlling slurry speed and net speed is the main factor in choosing headbox type. Fully enclosed hydraulic headbox adjusts pulp speed by adjusting pulp feeding pressure of pulp pump, which is suitable for high-speed paper machine; air-cushion headbox adjusts speed by adjusting air-cushion pressure, while open high-level headbox adjusts speed by adjusting pulp height in box, which is suitable for medium-speed paper machine; open separator headbox is suitable for low-speed paper machine. Formed net is endless ring net, which forms a horizontal or slightly inclined flat net between breast roll and volt roll. As the working section of pulp dewatering, it is customarily called net case, so it is called long net. If the endless forming net is placed on the circular cage, it becomes the working section of the arc dehydration forming, which is called the circular net. If the steel drum with holes is used to suck the vacuum from the axle end to accelerate the pulp dehydration on the formed mesh surface, it is called vacuum circular mesh or vacuum forming mesh. If the pulp is clamped by two long nets, the two nets are dehydrated at the same time, which is called the clamping net shaper. These shapers adopt different forms of dehydration elements to accelerate the dehydration of pulp on the net. Components can be divided into three categories: static, rotating and both. Static elements such as dewatering plate, arc vacuum box, etc., rotating elements such as case roll, vacuum forming roll, etc. In addition to the single-form forming machine to form a long net paper machine, a circular net paper machine and a web clamping machine, there are also the forming parts which are composed of multi-long net, multi-round net, multi-clamping net and multi-form long net hybrid forming machine.

　　Press Department

　　The formed wet paper is further dehydrated by pressing. It consists of two hard and soft rollers, such as stone rollers and rubber rollers. The pressing section is composed of pressing groups of the same or different forms, including a vacuum suction device customarily. When pressing, supporting paper sheets with appropriate specifications of wool cloth can evenly distribute pressure and take away part of the water squeezed out by pressing. It can also increase pressure and improve the ability of pressing dehydration. Low-speed paper machines mostly use 20-60 kN/m line pressure, high-speed paper machines use up to 210 kN/m line pressure, when using high-impulse press, such as wet press press can reach up to 350 kN/m line pressure; rubber rolls are made into vacuum press rolls, groove press rolls, liner press rolls, blind hole press rolls and so on, so as to more effectively take the press water away from the press zone, these are new methods to improve the efficiency of press dehydration since the 1950s. Technology. After that, a double press structure is used to form a closed paper introduction. It consists of two or three groups of pressing and merging. The vacuum suction roller strips the wet paper from the forming net and feeds it into the compound pressing with the wool cloth support. The paper is then transferred between the pressing rolls, thus eliminating the phenomenon that the paper was broken due to the traction of self-weight and other factors between the pressing rolls in the past. Since the 1980s, there has been a wide-area pressing technology, strong rubber belt or rubber roll, which deforms under strong compression, thus having up to 750 kN/m line pressure and wide contact surface. It has obviously prolonged dehydration time and greatly improved the dehydration capacity of pressing. The effect is more prominent on high-speed paper machine. Now the dryness of pressed paper can be increased from 30-37% to 43-45%, and some can reach 50%. The number of times the paper touches the smooth hard roll surface or the number of times the rough rubber surface and the amount of dehydration will affect the surface quality of the paper. Reasonable treatment can significantly reduce the difference of smoothness on both sides of the paper, and vice versa can also cause the difference of smoothness on both sides of the paper to increase.

　　Drying section

　　Driven by gear or driven by wool cloth, a number of drying cylinders form a group, and a number of drying cylinders form a drying part. The linear speed of each group of dryers can be adjusted separately to maintain a small speed difference between each group of dryers to compensate for the shrinkage of paper sheets during drying. The dryness of the paper out of the drying section is generally about 92-94%. At the end of the drying part, a cold cylinder is usually equipped so that water and gas can condense on the surface of the cold cylinder. Condensate can wet the surface of paper sheet to get better smoothness in finishing. The dryer diameter is 1.5m. Single-sided gloss paper can be obtained by using large diameter dryer with high hardness and high gloss. The diameter of large diameter dryer is generally 3-7.5m.

　　Surface Finishing Department

　　Multi-process treatment is used to obtain good surface quality. Most papers are calendered by a mechanical calender after the paper machine, so that the paper surface is smooth and uniform. The mechanical calender is made of several cold cast iron rollers. The paper surface is flattened by the weight of each roll or by additional pressure. If higher surface smoothness is required, a super calender is used to calender the surface. It is generally composed of paper meal rolls and cold cast iron rolls arranged alternately. According to the different requirements of use, some varieties need surface sizing to improve the surface quality; others need surface coating to improve the appearance quality or printing quality. Surface sizing and coating can be used as paper to be added outside the paper machine through sizing machine and coating machine.