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The filter screen is one of the indispensable parts of the film blowing machine, and its main function is to filter the impurities in the plastic raw materials, such as dust, not melted completely plastic particles, etc., and to avoid these impurities causing slippage or irreversible damage in the die head. The function of the filter screen in addition to filtering the impurities in the plastic raw materials, can also increase the friction resistance between the screw and the plastic raw materials in the extruder, and increase the back pressure at the same time to help achieve the complete mixing of raw materials.
The manual plastic extruder screen changer has two filter stations.
When the impurities on the filter screen accumulate to a certain extent and the net needs to be changed, it is necessary to move the filter station out of the main body after slowing down or stopping, and wait for the filter station to enter the main body of the screen changer in extruder.
The advantage of plastic screen changer is to shorten the downtime and reduce the consumption of labor costs, through its own design, it can be very simple to replace the mesh in the filter, if you want to replace only need to turn the side hand to the opposite direction can easily replace the mesh, and its special design and assembly can effectively prevent the occurrence of leakage, the internal Teflon is an important design to prevent leakage. In addition, customers can also install a pressure gauge to detect pressure changes in the filter.
Prepare tools: wrench, tweezers, scraper, etc.
Turn off the power of the film blowing machine, open the discharge port, clean up the material on the funnel, and remove the residue.
Remove the old network. First remove the network nut, open the shell, and then use tweezers to remove the small shaft from the old net head. Pick up the scraper to scrape off the residue on the net, and then remove the old net from the net.
Install the new network. Take out the new net, the net head and the new net face up, use a finger to clamp the shaft in the center of the mesh, and then reverse the net head into the press buckle.
Install the network port. After installing a new net connector, place the network port nut and metal network port in sequence near the net connector, and tighten the network port nut using a wrench until it is close to the net connector.
Test the film blower. Plug in the wire and start to test whether the film blowing machine is normal.
Manual screen changers are the simplest type, requiring the extruder to be stopped for the operator to manually replace the screens. They are cost-effective and straightforward but result in downtime during screen changes, which can reduce productivity.
Hydraulic screen changers use hydraulic power to move screens in and out of the melt flow. This allows for quick screen changes without stopping the extruder, reducing downtime and increasing productivity. However, they come with higher initial costs and maintenance requirements compared to manual screen changers.
Continuous screen changers are designed to allow for uninterrupted operation. They use a rotating or sliding mechanism to replace dirty screens with clean ones while maintaining a constant melt flow. This type eliminates downtime for screen changes, leading to higher efficiency and productivity, but they are more complex and expensive.
Backflush screen changers feature a self-cleaning mechanism that extends screen life. When screens become clogged, a portion of the melt flow is reversed to flush out contaminants, cleaning the screens without stopping the process. This type offers extended screen life and reduced maintenance but is more complex and costly.
Dual-bolt or dual-piston screen changers have two screen cavities, allowing one to be in operation while the other is being changed or cleaned. The system alternates between the two cavities, ensuring continuous filtration with minimal disruption. These systems are more complex and expensive than single-bolt systems.
Contaminant Accumulation: As the molten plastic flows through the extruder, contaminants such as foreign particles, gel particles, and degraded material can accumulate on the screen.
Pressure Buildup: As the contaminants accumulate, the pressure in the extruder increases.
Screen Replacement: When the pressure reaches a predetermined level, the screen changer mechanism is activated. The old screen is replaced with a new, clean screen.
Pressure Release: The replacement of the screen releases the pressure buildup, allowing the molten plastic to flow through the new screen.
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