Single screw extruder and twin screw extruder have their own characteristics and applications. In some applications, you can choose either single screw or twin screw.
Extruder can be used in plastics industry, food & Pet food industry, chemicals industry, Pharmaceutical, Minerals and Nonwovens industry. This guide mainly introduces the plastic extruder.
Let’s introduce in detail what are the advantages and differences between single-screw and twin-screw extruders.
About Single Screw Extruder
What's Single Screw Extruder
Single screw extruder means that there is only one screw in the extruder barrel.
It is mainly composed of three parts: extrusion system, transmission system and heating and cooling system. Its basic structure is shown in Figure 1.
Extrusion System
The main function of the extrusion system is to melt and plasticize the polymer material to form a uniform melt, and realize the transition from the glass state to the viscous fluid state.
The extrusion system mainly includes feeding system, screw and barrel. It is the core part of the extruder, and the screw is the key core component of the extruder.
Transmission System
The transmission system is usually composed of a motor, a reducer and a bearing. Its function is mainly to drive the screw and supply the speed and torque required by the screw in the extrusion process.
During the extrusion process, the screw speed is required to be stable to ensure uniform product quality. However, under different circumstances, the screw speed needs to be adjustable so that the same equipment can be adapted to extrude different materials or different shapes products.
Heating and Cooling System
The heating and cooling system of the extruder consists of a heating device and a cooling device, which is a necessary condition for the smooth operation of the extrusion process. The heating device and cooling device must ensure that the temperature conditions meet the process requirements.
Application of Single Screw Extruder
Single screw extruder is mainly used in:
- Pipe extrusionsuitable for PP-R pipes, PE gas pipes, PEX cross-linked pipes, aluminum-plastic composite pipes, ABS pipes, PVC pipes, HDPE silicon core pipes and various co-extruded composite pipes.
- Profile and sheet extrusionsuitable for the extrusion of PVC, PET, PS, PP, PC and other profiles and sheets.
- Profile extrusionAdjusting the speed of the extruder and changing the structure of the extruder screw can be used to produce various plastic profiles such as PVC and polyolefins.
- Modified compoundingIt is suitable for compounding, modifying and enhancing compounding of various plastics.
About Twin Screw Extruder
What's Twin Screw Extruder
The twin-screw extruder is developed on the basis of the single-screw extruder. Due to its good feeding performance, mixing and plasticizing performance, exhaust performance, extrusion stability, etc., it has been widely used in the extrusion and forming of plastic products.
There are two types of twin-screw extruders: intermeshing and non-intermeshing. And, Intermeshing twin screw extruders have two types: co-rotating and counter-rotating.
Segmentation of Twin Screw Extruder
The screw system of a parallel twin-screw extruder is generally divided into 4 sections: conveying section, melting section (exhaust port), plasticizing section (vacuum port), and discharging section.
- Conveying sectionThe function is to transport materials and prevent backing.
- Melting sectionIn this section, the materials are fully melted and mixed through heat conduction and frictional shearing.
- Plasticizing sectionfurther melt and mix the ingredients of the material, with the function of distributing and dispersing mixing.
- Discharge sectionconveying and pressurizing, forming a certain pressure, making the materials more compact, and at the same time further mixing, to achieve the purpose of extrusion and granulation.
Advantages of Twin Screw Extruder
High torque, high speed
The development trend of twin-screw extruders in the world is toward high torque, high speed, and low energy consumption. The effect of high speed is high productivity. It has unique advantages in processing high-viscosity and heat-sensitive materials. At the same time, higher productivity can be achieved.
Wide range of applications
Suitable for processing a variety of materials.
There are many types of twin-screw extruders, and the equipment under various applications has very different characteristics.
For example, the intermeshing counter-rotating twin-screw extruder is excellent in the main application areas of pipe and profile extrusion, especially for PVC materials.
For applications related to compounding and reactive extrusion, the building block self-cleaning co-rotating twin-screw extruder is more excellent and widely used.
Application of Twin Screw Extruder
In the plastic extrusion industry, twin screw extruders are widely used.
Foam extrusion
- XPS extruded board
- Graphite EPS beads
- PET foam
- XLPE foam sheet
PET extrusion
- PET recycling
- PET sheet / PET film
- PET foam sheet/board
Sheet direct extrusion
- PP Compounding with Talc and Sheet Extrusion
- PP Compounding with Wood Fiber and Sheet Extrusion
- HDPE Waterproof Sheet
- BOPP Film Extrusion
- BOPET Film Extrusion
- EVA Film for Solar Cell Encapsulation
- PVB/SGP Film for Laminated Glass
Compounding extrusion
- Color masterbatches
- Filler masterbatches
- Additive masterbatches
- High filling material granulation (such as: PE, PP filled with 75% CaCO₃)
- Glass fiber reinforced, Flame retardant material pelletizing (such as: PA6, PA66, PET, PBT, PP. PC reinforced flame retardant, etc.)
- HFFR/PVC/XLPE cable materials compounding
- XLPE pipe material compounding
- HDPE pipe coating material compounding
- TPE/TPR/TPU/TPV compounding
- Hot melt adhesive, PU reactive extrusion granulation (such as: EVA hot melt adhesive, polyurethane)
- K resin and SBS devolatilization granulation
- Rubber devolatilization compounding
Difference Between Single and Twin Screw Extruder
| Single screw extruder | Twin screw extruder | |
|---|---|---|
| Structure | One screw in the barrel | Two screws, intermeshing (co-rotating or counter-rotating) or non-intermeshing |
| Cost | Simpler and cheaper; sufficient for some applications | Higher investment; more efficient and energy-saving |
| Feeding | — | Good feeding characteristics, suitable for powder |
| Mixing, venting, reaction, self-cleaning | — | Better than the single screw extruder; stronger in blending and reactive extrusion |
| Throughput | Tied to screw speed | Chosen independently of screw speed |
| Heat-sensitive plastics and blends | — | Shows its advantage when thermal stability is poor |
| Typical work | Pipe, sheet and profile extrusion | Compounding, reactive extrusion, foam, PET and direct sheet extrusion |
| Development direction | High speed, high efficiency, specialization | High torque, high speed, low energy consumption |
How to Choose Plastic Extruder
Although there are indeed many differences between single and twin screw extruders, they can also be used for some of the same applications, or they can be used in combination. So how should we choose a plastic extruder?
Generally speaking, within the budget, choose the most cost-effective equipment according to the application requirements.
Application requirements
According to the application direction that you want to put into production, communicate with experts what kind of solution should be adopted, whether it is a mature solution or a customized solution.
Budget range
Money does not fall from the sky. We hope to choose the best equipment within a reasonable budget to maximize the return on investment. Based on the results of communication with experts from multiple potential suppliers, we have to determine which ones are kept on the candidate list.
Brand selection
There are many large and small brands in the extruder industry, internationally known such as Coperion, Kraussmaffei, JSW, CPM and so on.
Whichever supplier you consider, compare reference installations in your material, process know-how and after-sales support, not only the price. USEON has delivered more than 2,500 twin screw extruders.
