Regular cleaning of extruder screens is essential for maintaining product quality and process efficiency. Two primary methods are mechanical cleaning and high-temperature pyrolysis (burn-out). The chosen method often depends on the polymer processed and the available facility equipment.
Mechanical Cleaning is common for less heavily contaminated screens. First, the used screen pack is carefully removed from the breaker plate after the extruder head is disassembled and cooled. The screens are then pre-cleaned by soaking in a solvent or a heated oil bath to soften and dissolve residual polymer. Subsequently, high-pressure air or water jets are used to blast away the loosened debris. This method is effective but requires care to avoid damaging the delicate wire mesh.
High-Temperature Pyrolysis (Burn-Out) is a more thorough method for heavily clogged screens or high-temperature polymers. The screens are placed in a specialized pyrolysis oven. The oven is heated to a temperature significantly above the polymer’s degradation point (often between 800°F and 1000°F), incinerating all organic contaminants into ash. After a controlled cooling period, the screens are removed, and the ash is blown off with compressed air. This process is highly effective and restores screens to a near-new condition.
Regardless of the method, a final inspection against a light source is crucial to confirm all holes are open. Proper handling with gloves is necessary to prevent oil from skin from causing contamination during the next production run.