Extrusion molding is also known as extrusion in plastic processing. In non rubber extruder processing, it uses hydraulic press pressure to extrude the die itself. It refers to a processing method in which materials are heated and plasticized while being pushed forward by the screw through the action between the extruder barrel and the screw, and continuously pass through the machine head to make products or semi-finished products with various sections.
Extrusion molding is a high-efficiency, continuous, low-cost and wide-ranging molding processing method. It is an early technology in polymer material processing. After more than 100 years of development, extrusion molding is a molding processing method with many varieties, changes, high productivity, strong adaptability, wide application and large proportion of output in the field of polymer processing.
Extrusion molding is one of the main forms of plastic material processing. It is suitable for most plastic materials except some thermosetting plastics. Extrusion molding method can produce various forms of continuous products such as pipe, bar, plate, sheet, profile, wire and cable sheath and monofilament. It can also be used for mixing, plasticization, granulation, coloring and blending modification of polymer materials. Moreover, extrusion blow molding technology and extrusion stretch molding technology, which are based on extrusion molding and combined with blowing and stretching methods, are important methods for manufacturing films and hollow products.
The extrusion process can be divided into two stages: one stage is to plasticize the solid plastic (i.e. turn into viscous fluid) and make it pass through the die with special shape under pressure to become a continuum with similar section and die shape; The second stage is to use appropriate methods to make the extruded continuum lose its plastic state and become a solid to obtain the required product.
Extrusion temperature includes barrel temperature, plastic temperature and screw temperature. Generally, we measure barrel temperature. The temperature is controlled by the heating and cooling system. Due to the instability of screw structure, heating and cooling system and the change of screw speed, the temperature of extruded materials fluctuates in both radial and axial directions, which affects the product quality. The strength of each point of the product is different, resulting in residual stress and dull surface. In order to ensure product quality, the temperature should be stable.
