The single layer stretch film making machine, as a key equipment for producing stretch films, plays an important role in the packaging industry. Mastering the correct operation methods can not only ensure the production of high-quality stretch film products and improve production efficiency but also guarantee the safety of operators and the normal service life of the equipment. This operation guide will introduce in detail the key points of operations from the preparations before startup to the production process and the maintenance steps after shutdown, aiming to provide operators with comprehensive, accurate, and easy-to-follow operation guidance to help them skillfully operate this equipment and achieve efficient and stable production.
I. Preparations Before Startup
(I) Equipment Inspection
Firstly, conduct an inspection of the machine's appearance to ensure that there is no obvious damage, deformation, or foreign objects attached to the machine body. Check whether the connections of each component are firm. For example, check whether the connecting bolts at the positions such as the connection between the extruder and the die head and between the traction device and the winding mechanism are tightened to prevent loosening during operation, which may lead to equipment failure or safety accidents.
Check the transmission parts, including whether the tightness of the motor belt is appropriate and whether the chain is well lubricated and properly tensioned. For the gear transmission part, check the meshing condition of the gears to see if there are any foreign objects caught or abnormal wear, ensuring smooth and efficient transmission and avoiding affecting the production progress or damaging equipment components due to poor transmission.
(II) Raw Material Preparation
Select appropriate plastic raw materials according to production requirements. Polyethylene (PE) is commonly used. Check the quality of the raw materials to ensure that there are no impurities, moisture, or lumps. Because impurities may clog the filter screen of the die head, affecting the quality of the film and the continuity of production, and moist raw materials may generate bubbles during the processing process, reducing the strength and transparency of the film.
Pour the raw materials into the dry hopper according to the specified amount and ensure that the inlet of the hopper is unobstructed and free of blockages. At the same time, pay attention that the amount of raw materials added should be moderate. Avoid overfilling or underfilling the hopper. Overfilling may cause the raw materials to overflow, affecting the cleanliness and normal operation of the equipment, while underfilling may require frequent addition of raw materials, affecting production efficiency.
(III) Die Installation and Debugging
Select a die head mold that matches the required thickness and width of the stretch film and carefully install it on the die head part of the extruder. Ensure that the installation is firm and the sealing is good to prevent the leakage of plastic melt. After installation, use professional tools to make fine adjustments to the gap of the mold to make it uniform, so as to ensure that the extruded film has a uniform thickness.
Connect the heating system pipelines and temperature control devices of the mold, check whether the heating elements work normally, and set the appropriate heating temperature range through the temperature controller. Generally, depending on the characteristics of the raw materials used and the process requirements of the film, set the temperature between 150 °C and 250 °C and conduct preheating to make the mold reach the predetermined working temperature, ensuring that the plastic raw materials can be fully melted, plasticized, and evenly extruded through the mold to form a film.
II. Startup Operation
(I) Starting the Extruder
Turn on the power switch of the extruder and start the extruder motor to make it run slowly. During the startup period, closely monitor the current change and running sound of the motor to ensure that the motor starts smoothly without abnormal noise or excessive current impact. If it is found that the motor has difficulty starting or there are abnormal situations, stop the machine immediately for inspection, and restart after troubleshooting.
As the extruder operates, gradually adjust the rotation speed of the screw, starting from a low speed and slowly increasing it to the predetermined production rotation speed. Generally, the initial rotation speed can be set at about 20% - 30% of the rated rotation speed. After the equipment runs stably, gradually increase the rotation speed according to the production process requirements to avoid uneven plasticization of raw materials or excessive extrusion pressure caused by too fast a screw rotation speed, which may damage equipment components.
(II) Temperature Control and Adjustment
After the extruder is started, continuously monitor the temperature changes in each heating zone to ensure that the actual temperature matches the set temperature. Since the melting process of plastic raw materials takes a certain amount of time, the temperature may fluctuate during the initial startup period. At this time, operators need to make fine adjustments to the heating power according to the actual situation to make the temperature stabilize within the set range as soon as possible.
Pay special attention to the temperature control of the die head part, as it directly affects the extrusion quality and forming effect of the film. If the temperature of the die head is too high, the film may be burned, affecting its physical properties and appearance quality; if the temperature is too low, the raw materials will not be fully plasticized, and the film surface will be rough and uneven. Use the PID adjustment function of the temperature controller or manually adjust the heating power to precisely control the temperature of the die head within the appropriate range.
(III) Starting the Traction and Winding Systems
When the plastic melt extruded by the extruder begins to be extruded from the die head mold to form a film, start the traction device and the winding mechanism. The speed of the traction device should be reasonably set according to the extrusion volume and the stretching ratio of the film. Generally, first set the traction speed at a level slightly lower than the extrusion speed, and then gradually adjust it to the speed value corresponding to the appropriate stretching ratio, ensuring that the film is moderately stretched during the traction process to obtain the required physical properties, such as tensile strength and elongation at break.
The startup of the winding mechanism should be smooth. Adjust the winding tension so that the film can be evenly and tightly wound on the core. Excessive tension may cause the film to be stretched too much or even break, while too little tension will make the film winding loose, affecting the appearance of the product and subsequent use. The precise control of the winding tension can be achieved by adjusting the rotation speed of the winding motor or the tension controller to ensure the winding quality.
III. Key Points of Operation During the Production Process
(I) Adjustment of Film Thickness and Width
During the production process, regularly measure the thickness of the film using a thickness gauge, usually once every 15 - 30 minutes, and adjust the film thickness according to the measurement results. If it is found that the film thickness is uneven or deviates from the set value, it can be adjusted by adjusting the screw rotation speed of the extruder, the traction speed, and the gap of the die head mold. For example, when the film thickness is too thick, the traction speed can be appropriately increased or the screw rotation speed can be decreased; when the film thickness is uneven, fine-tune the gap of the die head mold to make the melt extrusion more uniform.
For the adjustment of the film width, it can be achieved by adjusting the positions of the flattening rollers and the guide rollers on the traction device. If the film width is too narrow, the expansion angle of the flattening rollers can be appropriately increased to make the film moderately stretched in the transverse direction; if the film width is too wide, the position of the guide rollers can be fine-tuned to make the film more orderly and tightly wound during the winding process, ensuring that the width of the film meets the product standard requirements.
(II) Quality Monitoring and Problem Handling
Operators should always pay attention to the appearance quality of the film, including whether the surface is smooth and flat, whether there are bubbles, impurities, crystal points, and other defects, and whether the transparency and color are uniform. If bubbles are found on the film surface, it may be that the raw materials contain moisture or volatiles. At this time, check the drying degree of the raw materials and, if necessary, conduct further drying treatment on the raw materials; if impurities or crystal points appear, it may be that the cleanliness of the raw materials is insufficient or foreign objects are mixed in during the processing process. In this case, clean the filter screen of the die head in time and check the quality of the raw materials and the cleanliness of the production environment.
Regularly conduct physical property tests on the produced stretch films, such as the detection of tensile strength, elongation at break, tear strength, and other indicators, to ensure that the product quality meets relevant standards and customer requirements. If it is found that a certain performance indicator is unqualified, timely analyze the cause. It may be caused by unreasonable processing process parameters (such as temperature, stretching ratio, etc.), unstable quality of raw materials, or wear of equipment components. Take corresponding adjustment measures according to the specific reasons, such as optimizing process parameters, changing raw material suppliers, or repairing or replacing equipment components, to ensure the stability and reliability of product quality.
(III) Monitoring of Equipment Operating Status
Conduct a comprehensive inspection of the equipment's operating status at regular intervals (such as once an hour), including the temperature and pressure changes of the screw and barrel of the extruder, the running sound and temperature of the transmission parts, and the current and voltage parameters of each motor. By observing the changing trends of these parameters, timely detect potential problems that may exist in the equipment, such as unstable extrusion pressure caused by screw wear, increased heat and noise caused by lack of oil in the transmission parts, motor overload, etc., and take corresponding preventive and solution measures to ensure the safe and stable operation of the equipment.
Check the operation of the cooling system to ensure that the cooling fan operates normally, the cooling air duct is unobstructed, and the cooling water in the water tank has a moderate temperature and good circulation. The cooling system plays an important role in the sizing and physical properties of the film. If the cooling is insufficient, the film may stick to the rollers or have unstable dimensions; if the cooling is excessive, the film may become brittle and its stretching performance may decline. Therefore, according to the actual production situation, reasonably adjust the parameters of the cooling system to ensure that the cooling effect of the film meets the process requirements.
IV. Shutdown Operation
(I) Stopping Raw Material Supply and Extrusion
When the production task is completed or shutdown is required, first stop adding raw materials to the hopper of the extruder and let the remaining raw materials in the extruder be gradually extruded until there is no melt extruded from the die head. After stopping the raw material supply, the screw rotation speed can be appropriately reduced to make the materials in the extruder be extruded more fully, avoiding excessive residue of materials in the barrel, which may cause material degradation or carbonization when starting the machine next time, affecting product quality and the normal operation of the equipment.
(II) Shutting Down Each System
After the extruder has completely stopped extruding, turn off the heating system of the extruder and the die head in sequence. Wait for the temperature to drop to a safe range. Then turn off the power of the traction device, the winding mechanism, and other auxiliary equipment. Make sure that all electrical equipment is powered off to avoid potential safety hazards.
(III) Equipment Cleaning and Maintenance
After shutdown, clean the equipment in a timely manner. Remove the residual plastic materials on the surface of the extruder, die head, traction device, and winding mechanism. Use appropriate cleaning tools and solvents to clean carefully, but pay attention to avoid damaging the equipment surface. For the die head, especially pay attention to cleaning the internal channels to prevent the accumulation of plastic residues, which may affect the next startup and production quality.
Conduct a simple inspection of the equipment's key parts, such as checking the wear of the screw, the condition of the filter screen, and the tightness of the bolts. Record any problems found for follow-up maintenance and repair work. At the same time, lubricate the necessary parts as required to keep the equipment in good condition for the next startup.
Through following the above operation guide step by step, operators can operate the single layer stretch film making machine correctly and efficiently, ensuring the production of high-quality stretch film products and the normal operation of the equipment.
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