Biaxial stretching and traction winding process and processing technology

1. Processing technology control

1. Function

With the improvement of production level and production speed, the computer process control system is adopted in the entire film production line, the purpose is to improve product quality; improve production efficiency and save labor. The functions of the process control system are roughly divided into 3 points:

①Automatically set operating conditions;
②Central control and data exploration;
③Automatic control of film shape.

2. Features
The technical characteristics of the process control system are:

① The high quality of the product can be maintained in a stable state, especially the minimum thickness of the product can be guaranteed to save materials.
② The product replacement time is reduced, saving time and materials.
③The innovation of production technology leads to the collection of reliable process information to obtain high-quality products.
④ Ordinary operators can operate the machine, and the unstable quality caused by the operator factors is eliminated, saving labor. Operators are freed from tedious operations such as adjusting die bolts under difficult conditions.

3. System configuration
Several units belonging to the distribution system are placed under a centrally located general monitoring system. The system's auxiliary components, production speed, temperature and film thickness controllers are all connected to the central system. In addition, the system is connected with the main computer to realize the total control of the whole film production.

4. Automatic control system for film thickness change
Depending on the required properties, the properties of the produced films are also different. However, the accuracy of the film thickness is the same requirement for them and very important. Therefore, in order to improve film accuracy and achieve this accuracy in a relatively short period of time, various designs and ideas are used for die heads, thickness adjustment equipment, and control systems.

There are 3 types of thickness deviations:
①Medium and short-term thickness deviation in MD direction stretching;
② Medium and long-term thickness deviation in MD direction stretching;
③Thickness deviation in stretching in TD direction.

The short-term thickness deviation in MD direction stretching is mainly caused by mechanical reasons, such as extruder performance, changes in roller peripheral speed, etc. It is theoretically impossible to continuously reduce the deviation without improving the performance of the equipment. Long-term thickness deviations in MD stretching are caused by contamination of melt filters, changes in materials or environmental conditions, etc. The adjustment of the average film thickness is done by the feedback control system, which measures the average thickness stretched in the MD direction, and controls the screw speed of the extruder according to the thickness information. Thickness deviation in TD direction stretching is caused by inhomogeneous molten resin, uneven die temperature or irregular die lip gap, reducing thickness deviation is the main purpose of the automatic control system for thickness variation.
Automatic control system for film thickness change:

① The position of the measured film thickness change in the TD direction stretching should be consistent with the position of the adjusting bolt on the die head.
② It is necessary to adjust the mutual interference between the die lip gap and the adjacent bolts.
③In order to correct the deviation, it is necessary to adjust the clearance of the die lip.
·Method 1 Make a mark on the molten resin at the outlet of the die head, and the position of the mark can be measured on the cast film substrate, the longitudinally stretched film and the biaxially stretched film.

·Method 2 When the die lip adjustment bolt is continuously adjusted at a given rate, the change in film thickness can be measured.

• Method 3 The proper location of bolts can be determined by statistical analysis of control data from production operations.
The requirements of ② can be met by the following methods:

When adjusting a bolt, use the experimental equation to approximate the film thickness change and calculate the control amount. Assuming that several bolts are adjusted at the same time, the change of film thickness is regarded as the superposition of the individual thickness changes when each single bolt is adjusted.

Every step of limited stretch processing from raw material supply to winding. In fact, each processing step is not independent, but related, and the processing conditions are closely related to the finished product and film properties. The biaxially oriented film production machine must be high in speed, wide in width and stable in performance. Therefore, it is very important to conduct basic research on each processing step and the relationship between each processing step.

Nanjing Sumino Seiko Machinery Co., Ltd. is a high-tech enterprise integrating scientific research, production and sales. It has always adhered to the business philosophy of integrity, equality, and customer interests first. production track. We have established independent research and development technologies for seven major types of equipment, including plastic sheet, casting, biaxial stretching, non-woven non-woven melt-blown fabric, laminating compound, regeneration granulation environmental protection recycling system and coating machine manufacturing system. The center and production department provide a complete set of professional technical solutions to meet the special needs of each customer. Among them, the biaxially stretched film manufacturing system includes: BOPP biaxially stretched film manufacturing system, PVC biaxially stretched shrink film production line, PET biaxially stretched film production line, BOPA biaxially stretched film production line, BOPLA biaxially stretched film production line,