Type of extruder screws

Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.

Screw refers to the metal rod with screw groove that can rotate in the barrel of extruder or injection molding machine. Screw is the most important part of extruder to transport solid plastic, plasticized plastic and melt, which is often called the heart of extruder. Through the rotation of the screw, the plastic in the barrel can move and get pressurized and friction heat. The geometric parameters of the screw have a great relationship with the characteristics of the extrusion machine. Whether the screw design is reasonable or not directly affects the working performance of the extrusion machine.

A screw with excellent performance should not only have high output, but also have a plasticizing effect that meets the product performance and a good comprehensive performance of temperature, pressure and speed. Therefore, a variety of new screws have come out one after another, which greatly improves the performance of single screw extruders. New type screws are generally divided into five categories: separation type screws, barrier type screws, shunt type screws, variable channel type screws and other new types of screws.

1.  Separation screw

The separation screw is a kind of screw designed according to the principle of separating the solid and liquid phases in the screw groove as soon as possible. Typical separation type screws include BM and XLK screws. BM type screw is widely used. It is a double headed screw designed by Maillefer company in Switzerland. The screw structure is to add a secondary screw edge (thread) at the melting section of the screw, which divides the original screw groove into two screw grooves. One spiral groove is connected with the spiral groove of the feeding section (called solid-phase spiral groove), and the other spiral groove is connected with the homogenizing section (called liquid-phase spiral groove). The gap between the secondary screw edge and the barrel is larger than the gap between the main screw edge and the barrel. The melted materials in the solid-phase spiral groove will cross the gap and enter the liquid-phase spiral groove, while the unmelted solid particles will not cross the gap and remain in the solid-phase groove to achieve the effect of solid-liquid phase separation and make the unmelted solid particles melt faster.

Advantages of separation screw: high plasticizing efficiency, good plasticizing quality, stable melt pressure and small temperature fluctuation.

2. Barrier screw

A "barrier" is set up at a certain part of the screw to hinder the passage of the solid phase and promote the melting of the solid phase, which is called barrier screw.

The advantages of barrier screw are that it improves the plasticizing quality of melt, improves the uniformity of plastic mixing, has good mixing effect and reduces the temperature difference.

3. Mixing section of screw

The mixing capacity of the standard screw (referred to as "mixing" in some data) is relatively low. In order to improve the mixing capacity, many mixing section (mixing section) designs have appeared.

The mixing section of the screw can be divided into dispersive mixing section and distributed mixing section. The dispersive mixing section includes Engan mixing section, UC mixing section, dray mixing section and convex ring mixing section; The distributed mixing section includes pin type mixing section, Dulmage mixing section, Saxton mixing section, pineapple type mixing section, slotted screw rib, groove transfer mixing (CTM), etc.

If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.