Parameter Selection Of Curved Roller In Paper Anti-crease Application

During the paper production process, wrinkles often occur during the operation of the paper due to the shrinkage force of the paper cross section. With the continuous improvement of the market's requirements for paper quality, anti-wrinkle has always been a serious problem facing manufacturers. The superiority of the curved roller in the anti-crease application of paper is increasingly accepted by many manufacturers. This article will focus on the selection of the curved roller and the setting of the installation parameters.

The arc roll, also known as the stretch roll, is used in anti-crease applications to reduce the lateral slack of the paper and tension the material. The selection of the curved roller will determine the degree of tightness of the paper, thereby affecting the anti-crease effect. For example, when the paper passes through the curved roller, excessive stretching will cause the elastic deformation of the material. After the paper leaves the curved roller, it will shrink, which often does not provide a good anti-crease effect. This article will discuss the selection of the parameters of the arc roll in combination with the actual situation.

1.Working principle of arc roll
There is a basic rule in the field of coil processing: the coil will always try to stay perpendicular to the roller it approaches, or the coil will adjust itself vertically into the roller it approaches [1]. This criterion is widely used in the coil correction industry. The difference between normal straight rollers and curved rollers is whether the axis has arc. In fact, we can think of a normal straight roller as a special curved roller with an infinite axis radius. In the process of paper production and processing, due to the shrinkage force of the cross section of the paper, wrinkles often occur during the operation of the paper [2]. In the application of curved rolls, when the roll is close to the entrance span L of the curved roll, the edges of the two sides of the paper will start to move sideways towards the corresponding end of the curved roll, slowly stretching the paper to obtain the tension effect. So as to prevent wrinkles. When the paper contacts the curved roller surface, the edge of the paper will be further moved sideways, and finally each point of the paper will be conveyed perpendicular to the roller surface

2.Parameter selection of arc roll

2.1. Stretching characteristics
The stretching characteristics of the arc roll are shown in Figure 1. The theoretical running path of the paper is indicated by a dotted line, and the actual running path is a solid arc. The degree of deviation between the actual running path and the theoretical value depends on the lateral slack of the paper and the elasticity of the paper by the introduction roller and the entrance span. It is assumed that the paper is already tensioned when it is introduced into the roller. After entering the curved roller, the paper will further deform elastically until the running direction of each point on the paper is perpendicular to the axial direction of the roller; or until the tensile force required for deformation exceeds the paper and roller Face friction. Most of the actual operations are in the latter state.

The friction force f between the paper and the roller is determined by the coefficient of friction between the paper and the roller, the wrapping angle of the paper on the roller surface, and the paper tension. The diameter of the roller has little effect on it or can be ignored.

3. Concluding remarks:
The use of curved rollers to reduce the wrinkles caused by the paper during transport must be selected based on the entrance span. It is not necessary to limit the size of the entrance span excessively, nor is it necessary to limit the angle of the paper wrap. The ideal wrap angle is 90 °, which can be appropriately increased, but the stretch performance of the roller will be reduced accordingly. The entrance ratio should be between 15-70, and the exit span can be as short as possible. Generally, 0.1-0.5 paper is selected.