Heavy packaging film blowing machine.

The packaging of resin and chemical products also requires a large number of heavy packaging bags. Therefore, the heavy packaging film blowing machine unit is also an indispensable equipment in the rapid development of petrochemicals. The current market demand is very large and the prospects are broad.

Host

The SJ-75¡Á30 plastic extruder is a new product designed by the company based on the material conditions of the user. Compared with conventional extruders, improvements have been made in screw, barrel, reducer, main motor power and other aspects to make it more suitable for plasticizing and extruding raw materials with poor fluidity. In terms of the spatial configuration of the host, two Y75¡Á30 plastic extruders are used, arranged at 90¡ã to each other. As for how many hosts are suitable, there are different opinions. In my opinion, for the heavy packaging bags required by the aforementioned users, it is a more reasonable solution to use two hosts to produce composite packaging films. The reasons are as follows: (1) In terms of performance, the outer surface of heavy packaging bags needs to be wear-resistant, and the surface should be easy to print. Of course, it also needs to be tear-resistant. In order to facilitate palletizing, the greater the surface resistance, the better; the inner layer of heavy packaging bags, undoubtedly, its first performance requirement should be good heat sealing, so as to facilitate the firmness of the seal after loading. Therefore, the performance requirements of the outer layer and the inner layer are different. It is more reasonable to use two main machines to extrude the outer layer material and the inner layer material respectively, and then compound them through the die. (2) Because the width (folding diameter) of the heavy packaging film is only 550mm, the die is small. If a single large extruder is configured, it will look somewhat disproportionate from the appearance; and it is obviously more symmetrical and reasonable to configure two smaller extruders. (3) With two 75¡Á30 plastic extruders, the production capacity can be guaranteed to reach 200-240kg/h. And this output has been verified in practice to be the most ideal parameter value for single-line production of resin packaging bags. Of course, three 65¡Á30 plastic extruders can also be configured, but this configuration, apart from other things, will at least make the production site appear more crowded and will definitely cause many inconveniences.

Main parameters and main parts features of extruder

Model SJ-75¡Á30

Production capacity (when the user's raw material is mixed material) 100¡«120kg/h (single machine)

Screw speed 11¡« 110r/min

Screw material and treatment 38CrMoAlA high-quality nitrided steel is nitrided, with a nitrided layer depth of 0.6¡« 0.7mm and a hardness of 65¡« 67HRC

Barrel material and treatment Double-layer metal, base 45# forged steel.

The thickness of the alloy inner surface is 1.5¡« 2.0mm, the material is SL-100, the hardness is 58¡«64HRC, and the centrifugal casting method is adopted.

Main motor (frequency conversion motor) model YTSP315S-6

Power 75kW

Frequency converter model ACS601-0100-8 (75kW) AC380V

It can be clearly seen from the above parameters that the main machine adopts a high-power frequency conversion motor. This is the main measure for processing low melt flow materials. In addition, in the design of the screw, some key dimensions that affect the shear force are changed accordingly to adapt to low fluidity materials. Under the premise of ensuring full plasticization, the power consumption is minimized.

Design of the reducer

The main machine reducer is also an important component for maintaining long-term stable operation. While meeting the power requirements, the main parts of the reducer¡ªgears, shafts, etc.¡ªare checked according to national standards and mechanical transmission design manuals, and a larger safety factor is taken to ensure sufficient strength, rigidity and service life. A separate oil pump lubrication and oil cooler are configured, as well as an oil temperature display and filter blockage alarm device. In addition, thrust bearings and seals are all matched with similar well-known foreign brands to ensure high-quality performance.

Cooling system

The cooling system should be divided into two parts. One part is the external cooling of the film bubble, and the other part is the internal cooling of the film bubble. When designing, it is considered that the diameter of the heavy-packed film bubble is only 350mm (when the product folding diameter is 550mm), while the thickness of the film bubble reaches 0.15-0.20mm; on the other hand, the diameter of the film bubble is small, so the height from the upper traction roller to the ground should not be too high in design considerations. Under the premise of satisfying the film cooling, the lower the center height, the better, which not only involves the price of the unit equipment and the convenience of equipment operation, but also involves the height of the user's plant and the total investment of the user. However, if the center height is too low, it is obviously impossible to meet the cooling requirements of the film, especially in the south of my country, where the hot and high temperature surrounding environment in summer makes the cooling of the film more difficult to achieve. Therefore, while adopting external cooling of the film bubble, internal cooling of the film bubble is also adopted. And using the cooling air after the air cooler can better meet the requirements of film cooling, which is of course a more reasonable design. Although the cooling system is generally divided into two parts, internal and external cooling, in fact, when cooling air is adopted, it is composed of three parts, namely, double-duct cooling air ring (external cooling), internal cooling system and refrigeration and ventilation ducts.

Double-duct cooling air ring

This new technology and new structure have not been seen in similar domestic units. First, it has a double air duct, that is, the cooling air from the air cooler and centrifugal fan will have two channels after entering the air ring. First, it is blown directly to the die mouth of the machine head through the air circle tray 2 and the air lip 5 to obtain the best cooling effect; second, the cooling air is blown to the film bubble at a certain angle through the channel formed by the inner air circle 1 and the air circle 4, which further strengthens the cooling of the film bubble while supporting the film bubble and shaping the film bubble tube blank. In addition to allowing the wind to enter the two channels, the wind ring also allows the wind to pass through a large number of through holes on the conical surface of the wind bowl 3 to form a high-speed airflow passing through its surface, forming a secondary air intake, which further enhances the cooling effect.

In addition, in terms of structural design, multiple handles 13 are also configured to easily rotate the wind ring to achieve the effect of adjusting the air volume. All parts of the overall wind ring are made of cast aluminum, which is light and beautiful.

Internal cooling system

In the internal cooling system, foreign advanced technology and pneumatic butterfly valves are used, and advanced exhaust temperature gauges are attached, which can directly display the temperature of the gas discharged after cooling the inner layer of the film bubble. The basic principle of internal cooling is as follows.

The cooling air from the air cooler of the refrigeration system is blown to the inner wall (i.e., inner layer) of the film bubble through the fan, automatic control valve (i.e., automatic proportional butterfly valve), machine head, and internal wind ring. After the heat exchange, the wind flow rises to the suction pipe port, is sucked back to the machine head under the action of the fan, and is sucked and discharged to the outside through the manual regulating valve. This is the process of internal cooling.

In internal cooling, the entire process must be maintained as determined by the process requirements, and the role of the photoelectric detection head (i.e., ultrasonic sensor) is crucial. When the cooling air passes through the machine head and the inner wind ring and blows to the inner wall of the film bubble, it not only cools the film bubble, but also blows up the film bubble. When the film bubble diameter is blown to the diameter determined by the process, it is hoped that it will always remain constant at this bubble diameter, and this task is achieved by the photoelectric detection head.

According to the width of the product, the process personnel can first determine the bubble diameter of the film bubble, and then install the photoelectric detection head at the corresponding position of the bubble diameter, that is, within the effective working stroke range of the photoelectric detection head. In this way, the photoelectric detection head will send a corresponding electrical signal according to the change in the distance between it and the film bubble, and through the automatic control valve, the size of the valve opening will be changed accordingly, and the amount of air flowing will be changed, so that the bubble diameter is always stable at the determined value. For example, when the air volume entering the film bubble is slightly more, the bubble diameter of the film bubble will increase accordingly, and the distance between the probe and the film bubble will decrease accordingly. This decrease value will cause the probe to send a corresponding electrical signal. Through the automatic control of the air path, the automatic butterfly valve will reduce the open flow area accordingly, so that the air volume entering the film bubble is reduced, and the increased bubble diameter is restored to the original set value. Vice versa.

The role of internal cooling not only accelerates the cooling of the film bubble, but is also crucial to the quality of the product. A large amount of practice has confirmed that the combined cooling of the inside and outside has significantly improved the appearance quality of the product, especially the transparency of the film. The use of photoelectric detection heads can strictly control the accuracy of the product width while stabilizing the bubble diameter. In addition, according to feedback from users, the film blowing equipment with internal cooling is very easy for workers to operate, especially when the machine is turned on to lift the film, it can automatically reach the required bubble diameter, and the operator does not need to measure the film width many times before gradually forming a stable production.