Ultimate Guide: Types of Extruders

Among all kinds of plastic machinery, the core is the plastic extruder machine, which has become one of the widely used machines in the plastics processing industry. With the rapid development of the plastic extruder market, new models are constantly being introduced, which play a better role and value in different productions.

According to the number and type of screw

According to the number of screws, extruders can be roughly divided into single-screw extruders, twin-screw extruders, and three-screw extruders.

The twin-screw extruder machines can also be subdivided into coaxial twin screw, conical twin-screw, co-rotating twin-screw, and parallel twin screw.

Single screw extruder is the most basic extruder in production. In the multi-screw extruder, the twin-screw extruder has developed the fastest in recent years, and its application is becoming more and more extensive. Especially in the processing of PVC plastic door and window profiles, twin-screw extruder machines have become the main production equipment.

The single-screw extruder machine is suitable for pellet processing, and the raw materials used are pelletized pellets or crushed pellets. The twin-screw extruder is suitable for powder processing, and can directly use the mixed PVC material, which reduces the process of granulation but adds the process of grinding waste.

Single screw extruder VS twin screw extruder

Twin-screw extruder machines

  1. Large output, fast extrusion speed, suitable for mass production.
  2. The material residence time is short, suitable for powder processing.
  3. With self-cleaning ability.
  4. Twin-screw extruder is widely used in the physical and chemical modification of matrix resin, such as filling, strengthening, toughening, reactive extrusion, etc.
Twin-screw extruder
Twin-screw extruder

Single screw extruder machines

  1. The extrusion speed is slow, and it is generally used for the production of small auxiliary profiles.
  2. The material has a long residence time, which is suitable for the extrusion processing of pellets.
  3. No self-cleaning ability.
  4. Single screw extruder is mainly used in the fields of pipes, plates, sheets, and profiles.

Three screw extruder machines

As the application fields of screw extruders continue to expand, the development and innovation of extruders have been promoted. The three screws of the three-screw extruder are arranged in a line and rotate in the same direction, which is equivalent to two pairs of twin screws. This improves the mastication effect, increases the output, and does not increase the energy consumption much. Due to the existence of the two meshing areas, the doubled increase of the rolling area can shorten the screw length and reduce the negative impact caused by the screw cantilever.

Other design types of screw extruder machines

According to the design improvement on the details of the extruder and the combination of different extrusions, the types of extruders are split twin-screw extruder, two-stage extruder, vented extruder, reciprocating single-screw pin-barrel extruder, planetary roller extruder, etc.

Split twin screw extruder

The split twin-screw extruder machine is based on the original twin-screw extruder. Its barrel is integrated and cannot be opened. The screw and barrel of the split twin-screw extruder adopt an advanced “building block” design. The screw is sleeved on the mandrel screw block in various forms, and the barrel bushing can be adjusted according to the screw block. According to the technical requirements of material types and other technical requirements, combined with the ideal form of the screw element structure, it realizes the processes of material transportation, plasticization, refinement, shearing, exhaust, pressure making, and extrusion, so as to better solve the general difficulty in balancing the contradiction between the so-called screw versatility and specificity.

Vented extruder

The main feature of this machine structure is that there is an exhaust port in the middle of the barrel. When using an ordinary plasticizing extruder, a small amount of gas will be discharged from the feeding port. When the residual gas has a great influence on the processing quality, the IM polymer pellets should be dried in advance. The exhaust extruder can be used to partially or completely replace the labor-consuming and time-consuming drying process. The exhaust extruder is mainly used to process polymer materials with strong hygroscopicity, such as rigid polyvinyl chloride, ABS, nylon, polyoxymethylene, and polymethyl methacrylate.

Non-screw type extruder – ram extruder

A ram extruder is an extruder without a screw. It uses the stamping principle. The material is pushed forward by the strong pushing force of the plunger. The ram plastic extruder extrudes the previously plasticized material from the die with the help of plunger pressure to achieve the molding effect. After the material in the material barrel is extruded, the plunger will return, and the operation will be repeated after a new round of plasticized material is added.

Early ram extruder machines were intermittent extrusion. At present, a continuous ram extruder has appeared, which uses double plungers to minimize the influence of the intermittent feeding on the extrusion process. Ram extruders are divided into horizontal and vertical types.

Advantages of a ram extruder

The piston of the ram extruder compresses the mixture, then uniformly heats and melts it. It is suitable for carrier materials such as drugs and has the advantages of uniform and bubble-free compaction after compression. And the remaining gap between the piston and the die of the ram extruder machine is very small, so there is almost no material loss.

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