Single Screw VS Twin Screw Extruder: What’s The Difference?

Over the years, food manufacturers have invested a lot of money in developing affordable and efficient technology. At present, twin screw extruder systems are the latest development. This technology offers numerous benefits in producing high-quality foods. Single screw and twin screw extruders are often found in the plastics industry.

Therefore, if you want to invest in extrusion technology, it is crucial to understand the differences between single-screw and twin-screw extruders. This article will help you understand the differences between the two and their applications.

What is a single screw extruder?

The main objective of a single screw extruder is to form plastic products into the required shapes. To achieve this, the plastic raw material is heated, for example, polyvinyl chloride (PVC), until it reaches its melting point and then pushed via a die to achieve the desired shape. A single screw extruder relies on a rotating beltway with a constant speed. Understanding that raw material conveying, pumping, melting, and blending occur interdependently and simultaneously is essential. As a result of their difficult process control, single screw extruders have lower productivity.

Application of a single screw extruder

Single screw extruders can be used in:

• Thermal insulation boards, e.g., polystyrene

• Conveyor belt rubber

• Automobile tires

• Plastic sheets or films, e.g., carrier bags, packaging films, or tarpaulins

• Food storage bags or cling film

• Rotor blades used in wind turbines

• Packaging

What is a twin screw extruder?

Depending on the manufacturer and design, the twin screw extruder can be counter-rotating, co-rotating, intermeshing, or non-intermeshing. The machine has two screws parallel to each other rotating inside a barrel. It is essential to understand that the screw plan can determine the efficiency and capability of a twin screw extruder machine. Typically, twin screw extruders are efficient in mixing raw materials and are used to process power blends that need thorough mixing, melting, and formation.

Applications of a twin screw extruder

• Twin screw extruders are used in many industries, for example, manufacturing RPVC pipes, PVS profiles, RPVC dual conduit pipes, and PVC compounding.

• Twin screw extruders can also be used in chemical, food, and polymer industries to mix numerous products such as adhesives, soaps, detergents, cellulose pulps, mastics, sealants, food and feed products, toner, putties, plastics, etc.

 • In response to current environmental protection requirements, twin-screw can be used for one-step sheet extrusion production of some PET  or PLA /PBAT  degradable materials, utilizing the excellent dispersing and mixing ability of twin-screw, supplemented by melt booster pump to output stable and high pressure to produce the sheets directly. This solution can replace the two-steps sheets production process, in which the first step is mixing and granulation by twin-screw (for degraded materials), and the second step is adding the particles to the single-screw and extruding the sheet.

This solution of the one-step sheet extrusion production can reduce equipment energy consumption and avoid such problems of materials contamination that may be caused by secondary melting.

What are the advantages of a twin screw extruder?

Twin screw extruders are better and superior machines than single screw extruders.

Here are the advantages of using twin screw extruders:

• Excellent mixing capability because it has numerous specialized screw designs, for example, reverse screw elements, kneading blocks, and gear mixing elements. With several specialized screw designs, twin screw extruders can complete precise and accurate mixing or shearing.

• Twin screw extruders are flexible because they can effectively handle several processing functions in series, i.e., melting, mixing, cooking, venting, and cooling.

• With the positive pumping action of the screws in the barrel, twin screw extruders can handle vast raw materials and mix formulations.

• Reduce production costs with its high-speed performance and low energy consumption.

• The twin screw extruder is efficient in melting, conveying, and mixing raw materials, thus resulting in high output, high quality, and high efficiency.

Differences between the single screw and twin screw extruders

• Production flexibility – unlike single screw extruders, twin screw extruders are equipped with throughput and screw speed independency to handle multiple processing functions effortlessly.

• Improved mixed capability – twin screw extruders have a wide range of screw designs to enhance mixing raw materials/ingredients. However, single screw extruders have a limited mixing capacity.

• Higher productivity without a doubt, twin screw extruders have higher productivity than single screw extruders because the former can handle numerous materials and complex formulations. Also, the performance of a single screw extruder tends to reduce as the screw wears with time. However, in twin screw extruders, the screw’s wear and tear are compensated by the high operational speed.

• Increased return on investment and business potential – twin screw machines boast higher productivity and flexibility. Also, they can produce a wide range of products, unlike single screw extruder machines.

If you want to invest in an industry that relies on extrusion technology, you must choose between a single screw and a twin screw extruder. In a nutshell, twin screw extruders are the better choice because they offer a wide range of benefits. Single screw extruders are affordable and more economical to operate. However, if you want to produce a wide variety of products and grow your business exponentially, consider investing in a twin screw extruder.