Roller application in plastic packaging industrial
Rollers, especially mirror rolls, are an indispensable part of the plastic packaging industry. No matter whether it is calendering, extruding or casting, it is inseparable from the rollers.
The quality of the surface quality of the roller, the reasonableness of the internal flow path structure and the quality of the machining accuracy will directly affect the quality of the plastic product, especially for the plastic film. Therefore, it is particularly important for a plastic film product manufacturer to provide a high quality roller.
Roller has a wide variety of types, and has its own specific role. According to the process flow, there are rolling sticks, pressure sticks, casting rolls, etc. According to the function and use, there are heating roller, cooling roller, lead roller, idler roller and so on.
The structure is divided into seamless steel tube roll, forging and centrifugal casting roll. In short, different processes of plastic products require different rollers. Therefore, as a roller manufacturer in the production process of the receiving roller, the corresponding rollers should be designed for different products and different processes to ensure that the rollers are play its normal role in the production process.
Regardless of the type of process used, the following basic requirements must be met for the structure, design, material selection and processing of the roller:
1. The roller should have sufficient rigidity to ensure that the bending deformation does not exceed the allowable value under heavy load.
2. Roller surface should have sufficient hardness, generally required to reach HRC50 degrees above, with strong corrosion resistance. The coating has the ability to resist spalling, ensuring that the working surface of the roller has good wear resistance and corrosion resistance.
3. The working surface of the roller should be finely processed to ensure dimensional accuracy and surface roughness. Roughness should be Ra0.16 or more, there can be no pores or grooves. The wall thickness of the working surface of the roller should be uniform, otherwise the uneven temperature of the roller surface will be affected and the quality of the product will be affected.
4. Roller material should have good thermal conductivity, usually chilled cast iron, in particular, cast steel or molybdenum-chromium alloy steel, whether heated or cooled, can achieve rapid and uniform.
5. Roller design is easy to process and low cost.
Special Requirements for Rollers in the Production of Film Products In the calendering and extrusion process, the rollers are usually subjected to a large pressing force, which generates a certain separation force relative to the product, so that the roller is supported at both ends.
The cylindrical beam on the bearing cannot be calculated by the bending formula of the general beam, but the maximum deformation value can be calculated by using the formula of the total deflection (including bending deflection and shear deflection). In actual production, it is proved that the total deflection in the middle of the roller is far greater than the allowable tolerance of the product. Therefore, it must be tried to give compensation, otherwise the accuracy of the product cannot be achieved. Because the deflection is the largest in the middle of the roller and the two ends are smaller, the products appear to be thick in the middle and thin at both ends. Therefore, there are usually three ways to compensate the deflection, namely the medium height method, the preload method and the preload device.
In order to eliminate the thin thickness at the middle of the product, the working surface of the roller is consciously processed into a drum shape with a large central diameter and a small diameter at both ends. The difference between the maximum diameter of the middle portion and the minimum diameter at both ends is called the middle height E. Of course, the ideal mid-height curve shape should be the deflection curve of the roller. However, because machining is difficult to do, it is often compensated by using a part of an arc or an ellipse.
In fact, the exact mid-height curve is not necessary, because there are many factors that affect the magnitude of lateral pressure. These factors change, the lateral pressure also changes, and the deflection also changes, so the limitations of the fixed height compensation method Very large, generally not used alone. As the medium-height compensation method is simple and easy to apply, application is more common.
When the roller has no other compensation method, the height is within the range of 0.02 to 0.10mm. When used in combination with other compensation methods, the medium height is in the range of 0.02 to 0.06mm. At present, when manufacturers produce medium-high, the grinding head of the grinding machine is pulled at an angle according to the medium-high requirement, and the grinding is performed from both ends to the middle.
This operation often forms a peak, and the two sides are straight and there is no middle-high curve. Some large-scale CNC roll mills currently used by enterprises have adopted computerized automatic control consoles to perform curve motions. The milled roll surface is a curved shape that can basically conform to the deflection curve and meet the requirements for the production of plastic products.
Strictly implement the roller production process to ensure the quality of the roller
At present, there are a lot of roller manufacturers in China, but only a few manufacturers can really provide high quality rollers. The reason for this is that a high-quality roller must be strictly implemented in the manufacturing process.
In the absence of any intermediate process, the roller can be made on the surface, but it will expose serious quality problems during the actual use. Affect the normal production of the use of the manufacturer.
Therefore, to make a high-quality roller, we must first strictly select the blank blank material, and we should choose seamless steel pipe or forging or centrifugal casting according to different plastic products. In the production process, different blanks should be used accordingly. The heat treatment process such as quenching and tempering, and tempering; secondly, during the processing process, it is also necessary to eliminate stress after the welding process, and to perform surface quenching or nitriding treatment to increase the surface hardness. These processes must not be removed due to high costs.
The process seems to be invisible on the surface, but there are serious hidden dangers in the actual use of the production process, which is absolutely not allowed in the roller production.
Furthermore, the plating thickness and plating thickness should be strictly ensured during the plating and surface treatment process. In the grinding process, especially during the ultra-finishing grinding process, the process steps should be followed strictly.
Our Industry Rollers included Rollers for Plastic film, Rollers For Metallurgy. We supply quality Gearboxes and Electric Motors as well.
May 08, 2024
