Meaning
A metal screen or woven wire cloth removes solid contaminants and unmolten particles from the polymer stream inside an extruder. Melt filtration mesh is measured by the number of openings per inch, with higher numbers indicating a finer filter. This component is necessary for producing high quality films and fibers where even a tiny speck can cause a break.
Contamination Removal
Foreign matter like wood, metal, or degraded polymer gels are trapped by the screen. As the polymer flows through the melt filtration mesh, these solids are held back while the clean liquid plastic passes through to the die. This process ensures that the finished product has a smooth surface and a consistent internal structure.
Pressure Build
Blockage of the screen occurs as more contaminants are captured over time. When the melt filtration mesh becomes clogged, the pressure inside the extruder rises, which can affect the throughput and the temperature of the melt. Operators must monitor this pressure and change the screen regularly to prevent damage to the equipment or a drop in production quality.
Product Quality
Finer filters are used for applications that require the highest level of purity. While a coarse melt filtration mesh is sufficient for thick walled parts, thin films and precision tubes need a much tighter weave to prevent defects. Choosing the right mesh size is a balance between the need for clean material and the desire for long run times between screen changes.
High performance filtration systems can utilize multiple layers of different sizes to capture a wide range of particles, ensuring that the final melt is as clean as possible for the most demanding moulding tasks.
