Special requirements for rollers in the production of film products

In the calendering and extrusion process, the roller generally receives a large pressing force, and a certain separation force is generated relative to the product, so that the roller is like a cylindrical beam supported on the bearings at both ends, so ordinary beams cannot be used. The bending theory formula calculates its deformation, but the maximum deformation is calculated by the formula of the total deflection (including bending deflection and shear deflection). In actual production, it has been proved that the total deflection of the middle of the roller is much larger than the allowable duty of the product, so it is necessary to try to compensate, otherwise it will not meet the requirements of the accuracy of the product. Since the deflection is large in the middle of the roller and smaller at both ends, the product is thick in the center and thin at both ends. Therefore, there are generally three methods of deflection compensation, namely the medium height method, the preload method and the preload equipment.

In order to eliminate the situation that the center of the product is thick and the two ends are thin, the working surface of the roller is consciously processed into a waist drum shape with a large diameter in the middle and a small diameter at both ends. . Of course, the ideal mid-height curve shape should be the deflection curve of the roller. However, due to the difficulty of machining, a part of an arc or an ellipse is often used to approximately compensate.

In practice, an accurate mid-height curve is not necessary. Because there are many factors that affect the size of the transverse pressure, these factors change, the transverse pressure also changes, and the deflection also changes. Therefore, the fixed mid-height compensation method has limitations. Very large, generally not used alone. Due to the simple and easy operation of the middle-height compensation method, it is widely used. When the roller has no other compensation method, the middle height is in the range of 0.02~0.10mm. When it is used in cooperation with other compensation methods, the middle height is in the range of 0.02~0.06mm. At present, when making medium and high heights, the general manufacturers will turn the grinding head of the grinding machine to a point of view according to the medium and high requirements, and grind from both ends to the center. This operation often forms an angle peak, and the two ends are straight and there is no medium and high curve. However, the large-scale CNC roll mills currently used by some enterprises use computerized automatic control consoles to perform curvilinear motion, so that the milled roll surface is in a curved shape, which basically conforms to the deflection curve and meets the production requirements of plastic products. Polyurethane roll. Strictly implement the roller manufacturing process to ensure the quality of the roller, tungsten carbide roller.

At present, there are many roller manufacturers in China, but there are very few manufacturers that can really supply high-quality rollers. The reason is that to do a good job of a high-quality roller, it is necessary to strictly perform the manufacturing process. Without any process in the center, it seems that the roller can be made on the surface, but in the process of practical application, serious quality problems will be exposed. Affect the normal production of the manufacturer. Therefore, in order to make a high-quality roller, the material of the roll blank must first be strictly selected. The seamless steel pipe or the forging or centrifugal casting should be selected according to different plastic product processes. In the production process, it is necessary to select different roll blanks. Corresponding heat treatment processes such as quenching and tempering; secondly, in the process of processing, it is also necessary to eliminate stress after the welding process. In order to improve the surface hardness, surface quenching or nitriding treatment processes must not be drawn due to high costs. It seems invisible on the surface, but there are serious dangers in the actual production process, which is definitely not allowed in the production of rollers. In addition, in the process of electroplating and surface treatment, a moderate coating thickness should be strictly ensured. In the grinding process, especially in the ultra-finishing process, the process should be strictly followed, and the normal process should never be neglected. To reduce the process, otherwise it is impossible to make a qualified roller.