Film drawing I of the hottest biaxial stretching B

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Biaxial stretching BOPP production line film drawing (I)

I. overview of equipment technology

our company has always taken technology development as the purpose for many years, constantly accumulating technology and improving the technical content in the process of equipment manufacturing. After three years of careful planning and Seiko production. In December, 2002, a complete set of production line equipment close to international similar products was manufactured, and a trial run was successful

the success of BOPP unit of biaxial directional flat film step-by-step drawing method in Far East indicates that the decision of President Xiong of far east company to jointly develop national industry in the field of Bo film production is correct due to cooperation and complementary advantages with Guilin Electric Power Research Institute. On this occasion, I would also like to thank the engineering and technical personnel of a large number of film manufacturers in China who support the localization of Bo film production line for providing valuable experience for the additional research and development of domestic double pull film production line. In the successful BOPP unit of far east company, we can see that the technical level of the production line, which is about to digest and absorb the advantages of world advanced companies and fully consider the characteristics of China's manufacturing technology, is close to the level of similar imported production lines in terms of stability, reliability, automation level and product quality

in the first BOPP production line of our company's production team, we choose a set of series host and two auxiliary machines to form a production line that can produce three-layer coextrusion film. Its varieties include: ordinary flat film, Matt Film, pearlescent film, single-sided heat sealing film, double-sided heat sealing film, etc. Its thickness ranges from 15 to 50 μ m. The width is 4.2 meters, and the maximum mechanical speed is 180m/min. The strength and flexibility of this kind of composite material is equivalent to that of conventional food packaging film. The production capacity is 20 mm thick μ M is the calculation basis, and its output is 5800t/y

II. Overall matching characteristics of the production line:

1. The operation and control of the production line are all controlled by the programmable controller. Speed control and pressure control are implemented for the transmission device of the extruder, and high transmission accuracy is guaranteed for the main extruder and the cold drum, so as to ensure the uniformity of the longitudinal tolerance of the film. Longitudinal stretching adopts small gap single point stretching, and the stretching ratio is arbitrarily set and adjustable from 1:1 to 1:7. Tension sensors are used for speed coordination between cold drum and longitudinal slow roll and horizontal pull, as well as between longitudinal fast roll and horizontal pull. The speed from the cold drum to the traction unit is given in a speed chain relationship to ensure that the line speed of the production line is coordinated. In order to improve the stability and reliability of the whole production line, we use Siemens S7 Series high-level programmable controller. All transmission systems use Siemens semeregkk6r24 full digital speed regulation device, and are equipped with Profibus fieldbus communication card, which can be directly connected with PLC controller to form a fieldbus network. The operator can directly monitor or adjust various process parameters, such as temperature, pressure, speed, draw ratio, etc., by selecting and adjusting the operation keyboard and screen, and the production process requires various forms of rapid speed change, as well as automatic adjustment, proportional adjustment, program operation, front and rear tracking, etc

2. In order to ensure the continuous, stable and reliable production of the production line, the supporting equipment we choose, such as die head, thickness gauge, corona treatment, motor, reducer, etc., are the products of well-known manufacturers at home and abroad

3. It is generally believed that the motion speed of the main working mechanisms of the stretching unit should have an accuracy and stability of about 0.5%. In order to improve the control accuracy of the transmission device of this equipment, we do not use the feedback of the tachometer generator, but the feedback of the encoder, which can improve the speed control accuracy by 10 times. In this way, the stability and accuracy of the movement speed and stretching ratio of the working mechanism can be guaranteed

4. In the process of drawing, whether the crystallization and orientation are uniform and whether the degree is appropriate depends on the uniformity and stability of the material temperature. In order to ensure the accuracy of temperature field. Our longitudinal drawing is heated by heat transfer oil, and the horizontal drawing machine is also heated by oil. The temperature is detected by platinum resistance, input into PLC and calculated by PID. Output 4 ~ 20mA analog signal and control the proportional flow control valve to realize temperature control. The temperature controller adopts S7 ~ 400fm455 temperature control template. Each fm455 can control 16 temperature points at the same time, which can adopt PID control mode and fuzzy logic control. It has adaptive function and temperature control parameters can be self-tuning

III. selection and matching characteristics of production line process plan

1. Raw material configuration and transportation system

in order to ensure the uniformity and stability of ingredients, we have selected the preparation and transportation plan of Marshall company of the United States, and use the capacity method to ensure accurate calculation and measurement. The proportion of main and auxiliary materials shall be strictly controlled. The system is equipped with a perfect mixing device to ensure the uniformity of the mixing of main and auxiliary materials. The system is also equipped with a negative pressure device. The raw and auxiliary materials are transported by means of negative pressure and suction to reduce the formation of powder

2. Extruder system

extruder system we have focused on the main extruder. For the main extruder, we have considered two schemes. First, we adopt the scheme of series extruder; Second, adopt the scheme of single extruder plus metering pump. We believe that these two schemes are feasible, and they are used in the imported production lines abroad. Finally, we tentatively choose the form of series extruder

we have specially designed the belt continuous automatic change device for the main and auxiliary extruders, and the main extruder adopts the column type long-term filter, which has a large filtering area. After taking these two measures, the continuous production cycle of the production line will be well extended, the number of start-up and shutdown will be reduced, the continuous production time will be prolonged, the production efficiency will be improved, the raw material consumption will be reduced, and the production will be greatly improved

3. Casting sheet forming system

in this system, we selected the water tank cold drum air knife casting machine, the diameter of the cold roll is 1.2m, and the two-way countercurrent spiral jacket is used to circulate the chilled water, so as to ensure the uniformity and stability of the surface temperature of the cold roll. According to the requirements of the film drawing process, the flatness and smoothness of the cast sheet is one of the keys to the quality of the film drawing. In the equipment manufacturing, the treatment of the roll surface is the top priority of our manufacturing process. For the forming cold drum, The preheating roll, stretching roll and qualitative roll of longitudinal drawing all adopt our patented technology, ultra precision grinding device, which reliably ensures the high smoothness of the roll surface and the extremely high mirror roller, ensures the smoothness of the diaphragm and improves the film making quality. (to be continued)

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