Plastic Sheet ExtrusionIn its most basic form, sheet extrusion begins with plastic pellets—often mixed with additives—being introduced into feeders. These pellets are then transported proportionally along a heated barrel by a pair of corotating screws, where they are melted, homogenized, and directed toward the gear pump. The gear pump can boost and maintain the melt pressure to achieve a stable the melt flow. The plastic melt is then pumped into a feedblock (for co-extrusion) or directly into die (for single layered sheet). The state-of-art sheet extrusion line is usually equipment with automatic sheet die, which allows to adjust the sheet thickness automatically to ensure everywhere on the sheet is flat.
The process can vary significantly depending on the applications, with factors such as screw elements design, barrel geometry, barre; temperature, screw rpm, chiller roll temperature, nip gap, nip pressure, linear speed, web tension and etc. Fortunately, FPP have the full knowledge how to adjust these parameters for varieties of materials to obtain satisfactory products.