在塑料挤出过程中，不管是挤出吹膜还是挤出型材、片材、薄膜、造粒等其它制品，由于塑料中可能存在的杂质，其它异物，以及未塑化的细微塑料颗粒，如果没有使用换网器进行过滤，往往会造成次品甚至挤出制品中断，产生很大的浪费，使生产成本增加。
In the plastic extrusion process, whether it is extrusion blown film or extrusion profile, sheet, film, granulation and other products, due to the possible impurities in the plastic, other foreign bodies, as well as the fine plastic particles that have not been plasticized, if the screen changer is not used for filtering, it will often cause defective products or even extruded products to interrupt production. Great waste is produced, which increases the production cost.
换网系统是挤出生产过程中重要的组成部分，尤其对于塑料回收和填充料生产来讲，更是必不可少。换网系统一般由换网器和动力系统组成，其中换网器又由本体、密封组件、多孔板、过滤网、切换装置组成。
Screen-changing system is an important part of extrusion production, especially for plastic recycling and filler production. The net-changing system is generally composed of a net-changing device and a power system, in which the net-changing device is composed of a body, a sealing component, a porous plate, a filter screen and a switching device.