2. Main motor driven by the variable frequency motor, and controlled by the frequency inverter, fast and stable for acceleration and deceleration.
3. Rewinding adopts differential air shafts, driven by the variable frequency control motor, automatic tension control.
4. Unwinding is controlled by the inverter and driven by the variable frequency motors, automatic tension controlled.
5. Unwinding adopts shaft-less loading and unloading, hydraulic lifting, easy for efficient loading and unloading, with web guide system.
Since the BOPP film is biaxially stretched during the production process, its tensile strength and impact strength are excellent, and the stiffness is high and the transparency is high. Therefore, this material is the most commonly used printing material in the packaging industry. However, its heat sealability is poor and cannot be used for the heat seal layer of the composite film. Its melting point is higher, above 160 degrees Celsius, so it has good high temperature resistance; but the glass has a higher glass transition temperature, so it is generally resistant to low temperature. The BOPP film has a certain barrier property, especially for water vapor barrier, but has poor oxygen barrier properties. When used in composite substrates, the common thickness is about 20 microns, and most of the products that require less barrier properties can choose BOPP as the printing composite. Biaxial stretching is a technique developed for subsequent orientation or simultaneous orientation of thermoplastic materials. At present, there are two main types of BOPP film production processes: 1. Tube film method; 2. Flat film method. It is divided into stepwise double pull and synchronous double pull. The product obtained by the simultaneous biaxial stretching in the flat film method has the advantages of isotropy, but it is difficult to manufacture due to complicated equipment, high manufacturing cost, and high development. The stepwise biaxial stretching is the method adopted by most manufacturers at present. Although the obtained products have different longitudinal and transverse properties in terms of tensile strength, fracture productivity, heat shrinkage rate, etc., they have little effect on product quality. However, it has the advantages of large output, fast speed, wide range and stable product quality.