The “Internal Bubble Cooling (IBC)” multilayer film blowing production lines produced by our company replaces traditional die heads, and also solves the problem of material leakage from the die head. We also designed a cold and hot air exchange system. When it is operating, it blows cold wind on one side and sucks out hot air on the other side to cool the film and quickly accelerate its formation. We designed the upper traction on the rotating structure to make the film more transparent and thicker.
In addition, our production speed is 4/3 faster than traditional machines and can produce 3-meter-wide film. So far, it has been the widest and fastest multi-layer co-extrusion rotary blown film machine in China because it has made successful innovation in upper traction. We have applied for domestic patents for our products and our technology is leading China.
Wuxi XX Adhesive Tape Co., Ltd. was established in Huishan District, Wuxi City in 2002. Its business scope includes the manufacturing of PE protective films, adhesive tapes, general equipment and accessories. The company purchased our PLASTAR blown film machines to manufacture self-adhesive films.
The customer is a local small- and medium-sized blown film manufacturer in Jiangxi which was established in 2018. Its main business includes production and sales of building materials, decorative materials, and packaging materials; sales of doors and windows, aluminum profiles, and stainless steel films (except hazardous chemicals).
The customers is a large-scale blown film manufacturer in Shenzhen, Guangdong that was incorporated in 2016 and specializes in the manufacturing of plastic protective films; manufacturing of plastic films; promotion of new material technologies; development of new material technologies; wholesale of plastic products; sales of packaging materials; design of packaging decoration; import and export of goods (except for commodities subject to franchise and are exclusively controlled); import and export of technologies; wholesale trade of commodities (except for commodities subject to approval); retail trade of commodities (except for commodities subject to approval).
In October 2017, an Iranian customer bought the ABA blown film machine ABA1200mm. The machine is running very stably. Because of our excellent quality and outstanding service, the customer also introduced a couple of friends to buy our products.
At the end of 2018, a customer successfully purchased the single-layer blown film machine SD-55-700mm, and the machine has been operating well in the customer’s factory.
In the exhibition of 2017, a Turkish intermediary customer chose us amidst many competing suppliers and successfully purchased the 2017 version of Asda equipment. After three years, the customer is still very satisfied with the equipment.
Vietnam in 2019
In October 2019, a Vietnamese customer successfully installed the 1600mm ABCDE five-layer co-extrusion blown film machine.
In October 2018, a Bolivian customer purchased two single-layer LDPE blown film machines.
In February 2018, An Argentina customer bought three SD-50 single-layer 600mm HDPE blown film machines.
In 2017, an Indonesian customer saw our equipment at the exhibition, and later visited our factory to negotiate on cooperation. He purchased three-layer co-extrusion and ABA blown film machines (ABC1700mm and ABA1400mm) that year, which are mainly used to produce PE film and bags.
Vietnam in 2017
In the Vietnam International Plastics & Rubber Industry Exhibition in 2017, we exhibited two blown film machines, i.e. the ABA900 and the MSD-45-600mm, which are mainly used to produce shopping bags. The high-speed equipment deeply attracted many customers and was finally ordered on the spot during the exhibition.
In 2019, A South African customer purchased a three-layer blown film machine ABC1700mm that is mainly used to produce bags. The machine is now operating normally in the factory and the customer is very satisfied.
In the Guangzhou exhibition in 2019, a Ukrainian customer was impressed by our equipment at the first glimpse and trusted in our strength, then he signed a contract on the spot to buy equipment.
In 2017, a Russian customer found us through social media and successfully ordered a two-layer stretch film machine CF-2L1000. Now the machine is operating normally and the customer is very satisfied with our equipment.
At the end of 2018, a Kenyan customer purchased an ABC 1800mm machine through an Indian middleman, which was mainly used to produce bags and shrink films. The customer is very satisfied with our equipment that gives him a head start in the local market.
The customer met with us in the CHINAPLAS in 2018, and was convinced by our product quality and service. They bought our exhibited ABC1800mm machine only 20 days after the exhibition. The machines are mainly used to product self-adhesive films, PE films and other products. They purchased another 3 sets of heavy machines in 2019 and 2020, mainly used to produce PE films and shrink films.
In 2018, a Philippine customer visited our factory and established trust and cooperation relationship with us. They purchased 6 blown film machines (ABC, ABA, AB, twin die, etc.) for the first time, mainly producing banana bags. Now the machines are running well in the customer's factory, allowing the customer to secure its part in the local market.
- Q1. Why do we need a three-way screen exchanger?
- Q2. What is recycled material, and what is the difference between the grades and prices of recycled materials?
- Q3. If particles with different characteristics are mixed together, can we produce a film with mixed characteristics?
- Q4. Why do we need a multi-layer co-extrusion blown film machine?
- Q5. Reasons for and solutions to poor openness
- Q6. What is the frost line of the blown film machine?
- Q7. What kinds of traction and transmission rollers are there on a blown film machine?
- Q8. What is the significance of the upper traction speed?
- Q9. What is IBC internal cooling and what is it used for?
- Q10. How to accurately control the temperature of the blown film machine while saving the heating energy of the blown film machine?
- Q11. Why is the temperature control of a blown film machine so important?
- Q12. What are the heating and heat dissipation methods of the screw of a blown film machine
- Q13. What are the types, advantages and disadvantages of a blown film machine's screen exchanger
- Q14. Surface treatment of the screw and barrel of a blown film machine
- Q15. Structural partition of the screw and barrel of a blown film machine
- Q16. Roles of the screw and barrel of a blown film machine
- Q17. What are the raw materials used in a blown film machine
- Q18. The production process of a blown film machine
- Q19. What is the purpose of a blown film machine?
- Q20. What is a blown film machine used for?
- Q21. What are the components of a blown film machine?
In the actual production environment of a blown film machine, dust, impurities in plastic particles and other substances are inevitable. This requires us to add a filter device between the screw and the mold to filter out impurities before they enter the mold, and prevent impurities from entering the mold to affect the transparency of the film.
Since it is being equipped with an additional filter, the three-way screen exchanger can resist the passage of molten plastic particles to a certain extent. The refluxed molten plastic is mixed and refined again so as to improve the fusion of the plastic formula in the screw and the plasticization of plastic particles, and enhance the quality of the film.
The recycled material refers to the plastic particles reshaped from recycled plastic film after being treated and then melted by a pelletizer.
The first-grade recycled material refers to the leftover material that is not contaminated with impurities, such as the edge of the online slitting of the blown film machine, and the plastic punched in the production of vest bags.
The recycled plastic particles processed with these leftover materials have better transparency. The quality of the particles formed by the pelletizer can rival that of the new material, so it is called the first-grade recycled plastic particles or the super-grade recycled plastic particles.
The second-grade recycled material refers to the recycled film that has been used once. It is judged by observing the transparency, brightness and surface roughness of recycled plastic particles formed by the pelletizer.
The third-grade recycled material refers to materials that have been used twice or more. The elasticity, toughness and other properties of the recycled plastic particles formed by the pelletizer are not outstanding, so the material can only be used for injection molding. The first-grade and second-grade recycled plastic particles can be used for film blowing.
Price grades of recycled materials:
First-grade recycled plastic particles: 70-80% of the price of new raw materials;
Second-grade recycled plastic particles: 50-70% of the price of new raw materials;
Third-grade recycled plastic particles: 30-50% of the price of new raw materials;
The above price ratio is for reference only
Different types of plastic particles have different plasticizing temperatures. If different plastic particles are plasticized in a screw at the same time, some plastic particles will not be fully plasticized due to the excessively low temperature, or suffer melting fat rupture due to the excessively high temperature. Therefore, a single screw cannot be used for the production of multi-characteristic plastic film even if it mixes plastic particles with different characteristics.
In addition, simple mixture is not sufficient to produce characteristic films, we need modular lamination of different layers, each of which has their respective functional layer.
Compared with the single-layer blown film machine, the multi-layer co-extrusion blown film machine requires more screws and purchase costs to produce film. Why do we choose a multi-layer co-extrusion blown film machine?
The selection of the multi-layer co-extrusion blown film machine actually depends on the application scenarios of the target film produced. If the film produced is mainly used as the packaging material for heavy packaging, high-end food bags, vacuum packaging bags, liquid packaging bags, etc., it needs the functions including fragrance preservation, freshness preservation, corrosion protection, air tightness, and extended shelf life. A single-layer and single-characteristic film can never live up to these functions.
In order to produce a film that is qualified as a packaging material, and blow and co-extrude materials with a variety of characteristics (such as breathability, heat preservation, toughness, etc.) to form a multifunctional plastic composite film, we have to choose a multi-layer co-extrusion blown film machine.
The purpose we choose a multi-layer co-extrusion blown film machine is to give full play to the advantages of multiple materials and avoid the shortcomings of a single material or single-layer blown film machine. Taking the PP/PE co-extrusion blown film machine as an example, the machine combines the high hardness of the PP material and the high brightness of the PE material to produce a film that has the characteristics of both.
We have the following models of multi-layer co-extrusion blown film machines:
Two-layer co-extrusion blown film machine,
Three-layer co-extrusion blown film machine,
Five-layer co-extrusion blown film machine,
Seven-layer co-extrusion blown film machine, etc.
For example: The five-layer co-extrusion blown film machine mainly uses plastic particles with gas barrier properties, such as HDPE, MHDPE, LDPE, LLDPE, MLLDPE, PA, EVOH, etc., to produce food packaging films that require fragrance preservation, freshness preservation, corrosion protection, air tightness, and extended shelf life.
Multi-layer co-extrusion is to extrude multiple layers of plastic particles from one die at the same time. Most food packaging films and special films are produced by this co-extrusion lamination.
The reasons of high stickiness and small opening of commonly seen LDPE films are as follows:
1、The grade of the plastic particles is incorrect. The particles used are not dedicated to the blown film machine. The particles contain zero or low content of anti-blocking agent.
2、The temperature of the blown film machine is too high, and the flow rate of the molten particles is too fast.
3、The blow-up ratio is too large, resulting in poor film opening.
4、The cooling speed of the air ring of the blown film machine is too low, and the film is not sufficiently cooled, resulting in mutual adhesion under the action of the upper traction roller.
5、The traction speed of the blown film machine is too fast and the frost line is too high.
Solution:1、Replace the plastic particles, or add a certain proportion of anti-blocking agent to the particles.
2、Appropriately reduce the temperature of the screw and the mold.
3、Reduce the blow-up ratio.
4、Increase the cooling air volume or adjust the temperature of the air cooler.
5、Appropriately reduce the speed of the traction roller.
The frost line of the blown film machine refers to the dividing line of the molten plastic from the fluid state to the solid state.
In the production process of the blown film machine, LDPE is in a melt flow state when it is extruded from the die while maintaining sound transparency. After leaving the die, the cooling air ring cools the inflation zone of the film bubble. When the cooling air blows to the plastic film bubble just extruded from the die, the hot film bubble will contact the cooling air, the heat of the film bubble will be taken away by the cold air, and the temperature will obviously drop below the temperature the LDPE requires to maintain the melt flow state, thus causing the film bubble to cool, solidify and turn blurred. On the film bubble of the blown film machine, we can see a dividing line between transparency and blur, which is the frost line of the blown film machine.
There are many conveying guide rollers on the blown film machine, which assume different roles in their respective positions.
Carbon fiber roller: Mostly used on the stabilizer frame. The film has not completely cooled due to the high temperature near the die (easy to scratch the surface). The carbon fiber roller is characterized by light weight and high temperature resistance. It can easily pass through the film without fearing the long-term effect of high temperature.
EPDM rubber roller: Film conveying requires greater friction. We usually choose a rubber roller as the power transmission roller. In terms of material selection, we will have more considerations and will use EPDM, which is because of the particularity of the blown film machine industry.
Many blown films will be treated to remove static electricity to match the subsequent printing operations, Electrostatic removal by electric shock will generate ozone gas, which will accelerate the aging and cracking of ordinary rubber rollers. The rubber roller made of EPDM is lighter in weight and has heat resistance, aging resistance and ozone resistance. So we will choose a more suitable rubber roller based on many considerations.
Curved roller: Curved rollers are arranged near the winding part of the blown film machine. The curved roller forms an arc on one side of the roller shaft, which stretches the film when it rotates to eliminate wrinkles and prevent possible intertwining during material cutting.
Aluminum guide roller: Aluminum guide rollers are mostly used on one blown film machine due to its low resistance, light weight and flexible rotation.
- A8. The upper traction speed is an important data for blown film machine production. The molten plastic is extruded from the die and pulled up by the upper traction. Under the same extrusion volume, increasing the pulling speed of the blown film machine will make the film thinner. Slowing down the pulling speed of the blown film machine will make the film thicker. Therefore, if you do not want to frequently adjust the pulling speed and waste raw materials when you are switching the blown film specifications, the meter weight controller is an ideal option.
The traditional method of film bubble cooling is to cool down the outside of film bubbles with an air ring. If the film is thick or the film is made of multiple layers of powerful barrier materials, only cooling the outside of film bubbles with an air ring will not be enough. The slow cooling speed, high frost line, unstable film bubbles, and poor film opening will all compromise the quality of films.
The IBC internal cooling uses an inlet fan to send the cooling air from the outside to the film bubble, while an exhaust fan discharges the hot air. Then it uses three ultrasonic probes to align the film, and determine the position of the film and the size of the tube by using the algorithm that the isosceles triangle is tangent to the film circumference. The hot air inside the film is exchanged with the air from the cooler, and the circumferential diameter of the film is stable.
The IBC internal cooling device exchanges hot and cold air in the bubble, which can not only increase the yield and the opening of the film, but can also exchange and eliminate the peculiar smell generated by the resin raw material at high temperature. The film produced with this method is more suitable for food packaging and medical supplies packaging.
The priority is to save the power loss of the blown film machine, and reduce the loss of electric heating. Nearly 40% of the power loss of the blown film machine is caused by electric heating, so how do we save the heating power of the blown film machine?
Traditionally, we use electric heating coil in combination with fan cooling, which is primitive. PLASTAR uses a smarter algorithm to optimize this process.
When the set temperature is close to the actual temperature, we use the pulse to break the heating screw. Then we heat for several milliseconds, measure the actual temperature after 1 second of stabilization, and repeat the circle over and over. During the operation of the blown film machine, the temperature will continue to decrease due to environmental temperature and heating of plastic particles. The used of the pulse heating method can reduce or eliminate the need of fan cooling and avoid frequent heating and heat dissipation. It not only reduces the power loss, but also reduces the wear and tear of the blown film machine. Eventually, the temperature control will be more accurate, the bubble will be more stable, and the quality of films produced will be improved.
Temperature control is very important for blown film machines. Each plastic particle has a specific melting temperature.
If the heating temperature is less than the melting temperature:
1、After the plastic particles are melted, their flow speed in the screw and the mold will slow down, and the output of the blown film machine will decrease.
2、Because the temperature is lower than the melting temperature, the plastic particles are not completely plasticized, and particles in the screw are not completely mixed and combined. The film will produce crystal points, and the film formula is not completely mixed, resulting in poor film quality.
If the heating temperature is greater than the melting temperature:
1、When the plastic particles are exposed to the temperature higher than the melting temperature, the melting fat will rupture. The transparency of the film will decrease.
2、The melting fat will rupture due to long-term exposure to high temperature. A small amount of black spots will appear on the surface of the film.
3、The bubbles will be unstable, serpentine, twisted and rise.
Therefore, if the temperature of the blown film machine is not accurately controlled, the problems mentioned above will appear alternately, which is a bad sign.
- A12. The screw of the blown film machine has the function of conveying particles, while the plastic particles will not be molten until the heating ring surrounding the screw reaches the target temperature. In order to stabilize the temperature of the heating ring, we have to stabilize the temperature control of the screw by heating with the heating ring and air-cooling with the cooling fan. If the current set temperature is less than the actual temperature, the fan is turned on and starts cooling. If the current set temperature is greater than the actual temperature, the heating ring is turned on and starts heating. By repeating this cycle, the plastic particles inside the screw of the blown film machine are molten at a relatively stable temperature and flow quickly in a molten state.
Due to the production environment of the blown film machine and the defects of plastic particles itself during the film production, many impurities will reach the produced film along the runner, bringing in some impurities such as crystal spots, coke particles, black spots, etc. Therefore, the blown film machine filters impurities by adding a three-way filter, which increases the controllable reflux of the screw, enhances plasticization, and ensures the transparency of the film. There are three modes and structures of the three-way screen exchanger.
Manual screen exchange：The manual screen exchange is a traditional way of exchanging screens. It needs to remove 8-10 screws from the place where the screw and the mold are connected, and remove the “top of the main machine” when the blown film machine is shut down, and then exchange the filter inside. To use this method, we need to stop the machine before replacing the filter. It will waste a lot of time to stop and start the blown film machine. Also, debugging the machine again will waste a lot of plastic and increase production costs, resulting in low production efficiency.
Manual quick screen exchange：The manual quick screen exchange is an alternative to the above method. It allows us to replace the filter screen without shutting down the blown film machine. There are two filter screen ports, allowing the operator to change the filter screen at one port while the other is working. When you need to change the screen, just press down or raise the handle to change to the other port. The entire process is fast and smooth. The filter screen can be replaced when the blown film machine is working, which saves time and wastes no plastic. It is suitable for screws with a diameter below 75mm.
Hydraulic automatic screen exchanger：Similar to the manual quick screen exchange, the hydraulic automatic screen exchanger has two filter ports, allowing the operator to exchange the filter screen at one port when the other is working. When we need to change the screen, just click the screen exchange button, and the screen will be hydraulically pushed to the exchange port. The screen exchanging action is completed rapidly without shutting off the blown film machine or any manual effort. Therefore it is suitable for screws with a larger diameter above 75mm.
The surface treatment of the screw of the blown film machine is divided into three types：
Most of the blown film machine screws are made of nitrided steel 38CrMoAIA. The strength of nitrided steel is 85-90kgf/m㎡. It has sufficient central strength as the screw of the blown film machine. However, the wear resistance and corrosion resistance of its surface are insufficient, which needs to be improved in the following ways.
1、Nitriding treatment: Combine ions with the surface alloy by means of salt bath liquid nitriding, gas nitriding, or ion nitriding, to obtain aluminum nitride with the surface hardness of HV1000-1100, which greatly improves the wear resistance of the screw surface.
Since the output of blown film machines has been increased in recent years, the rotating speed and the internal pressure of the screw are increased, and more importantly a large amount of filler materials are needed. The 0.5mm-thick nitride layer of the nitrided screw destroys the stable operation of the screw under high-speed wear and corrosion.
2、Alloy spraying treatment
The alloy spraying of the screw means spraying a special alloy layer of 0.5-0.8mm on the nitrided screw. After being treated, the wear resistance and load bearing capability of the screw will be further strengthened. It has a certain degree of corrosion resistance to corrosive particles.
3、Double alloy layer treatment
The most reliable screw of the blown film machine on the market nowadays is the double alloy screw. The base material of the screw is the SKD161 alloy. The surface of the screw is pressed with a 3mm-thick wear-resistant and corrosion-resistant alloy layer, which is bound by metallurgical methods and is therefore difficult to fall off. Then an alloy layer is sprayed on its surface. It delivers outstanding performance both in corrosion resistance and wear resistance for the long-term operation of the blown film machine. The life of the bi-alloy screw is 3-5 times that of the ordinary screw.
The screw is partitioned into： the unloading zone, the compaction zone, and the mixing zone.
The barrel is partitioned into: the blanking seat (inner water jacket) and the barrel.
- A16. The screw and the barrel of the blown film machine are mainly responsible for squeezing the plastic particles from the barrel into the mold of the blown film machine, then melting and pushing forward plastic particles under the action of the ever-forward pressure and the barrel’s heating ring.
- A17. The main raw materials of the blown film machine: low-pressure polyethylene HPPE, high-pressure polyethylene LDPE, linear polyethylene LLDPE and other plastic particles. Nylon, EVA, metallocene and other materials will be added for some plastic films with special properties.
Steps to normally start the blown film machine:
1、Heat the extruder body, die head, and maintain the temperature of each point within the target range.
2、If you start the machine after a long stop, the heating temperature of each point needs to be kept constant for 10-30 minutes after reaching the target range. This process is not required if the restart is within 30 minutes after the stop.
3、Start the air compressor and stop it when the cylinder pressure is 6-8kg/cm.
4、After the temperature of each point meets the requirements, put on labor protection supplies and start the tractor, blower, and extruder in order.
5、When the discharge from the die is uniform, you may wear gloves and slowly pull up the tube blank. Meanwhile you may seal the end of the tube blank and slightly open the air inlet regulating valve to blow a small volume of compressed air from the center hole of the mandrel, then carefully guide it through the foam stabilizer, the herringbone plate, and penetrate through the traction roller and the guide roller until it reaches the winder.
6、Check the thickness and width of different parts of the film, and adjust them until they meet specifications
- A19. The blown film machine melts different plastic particles according to the formula in alignment with the final product, and then blows them into a film. The films produced by a blown film machine are suitable for various kinds of high-end packaging. The films are also widely suitable for heavy and light packaging for their sound barrier properties, freshness preservation, moisture prevention, frost prevention, oxygen barrier properties, and oil resistance, including various kinds of fresh fruits, meat products, pickles, fresh milk, liquid beverages, medical supplies, etc.
The blown film machine is a machine that melts plastic particles through a screw, and then blows the melted flowing plastic into a film through a specific mold.
A blown film machine is mainly composed of the following parts:
1.Basic main machine (gear box, electrical motor, lower hopper, barrel screw, heating ring, head flange, frame, etc.)
2.Traction auxiliary machine (upper traction roller, traction motor, herringbone plate, traction bracket, guide roller, etc.)
3.Winding machine (middle traction roller, traction motor, cutting knife holder, winding roller, winding shaft, etc.)
4.Blow molding die head (die head, heater,)
5.Cooling device (cooling air ring, cooling fan, surface cooler, cooling air pipe, etc.)
6. Electrical control system (power distribution cabinet of main machine, including the automatic temperature control, the power distribution cabinet of auxiliary machine and the power distribution device for mold temperature control, etc.)