Several principles that need to be paid attention to in plastic extruders(1)

The extruder has high speed and high output, which enables investors to obtain large output and high return with low input. The high efficiency of plastic extruders is mainly reflected in high output, low energy consumption, and low manufacturing costs. Precision can increase the gold content of products, such as multi-layer co-extruded composite films, which require precise extrusion, and as an important means to achieve precise extrusion, melt gear pumps must be developed and researched. In terms of function, screw extruder is not only used for extrusion molding and mixing processing of polymer materials, but its use has been expanded to food, feed, electrodes, explosives, building materials, packaging, pulp, ceramics and other fields. Achieving large-scale extrusion molding equipment can reduce production costs, which has more obvious advantages in large-scale twin-screw granulation units, film blowing units, and pipe extrusion units. Here are a few principles to pay attention to for plastic extruders:

1. Structural principles

The basic mechanism of extrusion is simple - a screw turns in the barrel and pushes the plastic forward. The screw is actually a bevel or ramp that wraps around the center layer. Its purpose is to increase pressure in order to overcome greater resistance. As far as an extruder is concerned, there are 3 kinds of resistance to overcome: the friction of the solid particles (feed) against the barrel wall and the friction between them during the first few turns of the screw (feed zone); the melt Adhesion on the barrel wall; flow resistance inside the melt as it is pushed forward.

2. Thermal principle

Extrudable plastics are thermoplastics - they melt when heated and solidify again when cooled. Where does the heat to melt the plastic come from? Feed preheat and barrel/mold heaters may work and are important at start-up, however, the motor input energy - generated when the motor turns the screw against the resistance of the viscous melt Frictional heat inside the barrel - is the most important heat source for all plastics, except small systems, low speed screws, high melt temperature plastics and extrusion coating applications.

For all other operations, it is important to realize that the barrel heater is not the primary heat source in the operation and thus has less of an effect on extrusion than we might expect. Back barrel temperature may still be important as it affects the galling or solids conveyance rate in the feed. Die and die temperatures should generally be the desired melt temperature or close to this temperature unless they are used for a specific purpose like varnishing , fluid distribution or pressure control.