Parallel Twin Screw Extrusion Machine


Parallel Twin screw Extrusion Machine Introduction

Parallel twin-screw extruder for plastic extrusion

Parallel twin-screw extruder is widely used in the filling, blending, modification, reinforcement of reinforced plastics and engineering resins, devolatilization of chlorinated polypropylene and superabsorbent resins; degradable masterbatch, polyamide poly condensation, extrusion of polyurethane poly addition reaction; granulation of carbon powder, magnetic powder, insulating material for cable, sheath material, low-smoke low-halogen flame-retardant PVC cable material and preparation of various silane cross-linking materials.

Parallel Twin screw Extrusion Machine Parameters  

Model SJP75/28 SJP90/28 SJP110/28 SJP120/26 SJP130/26
Screw diameter(mm) 75 90 110 120 130
Number of screw 2
Screw speed(r/min) 1-45 1-30 1-30 1-45 1-30
Power of main motor(kw) 37 55 75 110 132
Production capacity(kg/h) 240 350 460 550 680
Screw steering Different to the outside


Parallel Twin Screw Extruder Vs Conical Twin Screw Extruder

Which is better, the parallel twin-screw extruder or a conical twin-screw extruder?

It is a question that users often ask when purchasing a twin-screw extruder.

Classification of twin-screw extruder

According to the direction of rotation of the twin-screw, the extruder can be divided into two extruders:

the same direction and the opposite direction.

The same direction extruder rotates in the same direction when the two screws work.

The counter-rotating machine refers to two screws whose directions of rotation are opposite when working.
According to whether the axis of the twin-screw is parallel or not, it can be divided into two extruders in which the axial line is parallel and the axial line intersects.

The axial line that is parallel is the parallel twin-screw extruder while the axial line that intersects is the conical twin-screw extruder.
Twin-screw extruders also have a meshing and non-engaging component.

The common ground of parallel twin screw extruder and conical twin screw extruder:

There is a conveying mechanism for forced advancement of plastics, good mixing plasticizing ability and

dewatering ability and basically the same adaptability to the molding process of materials and plastic products.

The difference between a parallel twin screw and a conical twin-screw extruder:

1. Diameter: The diameter of a parallel twin screw is the same while the diameter of a conical twin-screw extruder is different and the small end of the twin screw is different from the diameter of the large end.

2. Concentric distance: The center distance of the parallel twin screw is the same, the two axes of the conical twin screw are at an angle, and the size of the center distance varies along the axis.

3. Length to diameter ratio: Parallel double screw (L/D) refers to the ratio of the effective part length of the screw to the outer diameter of the screw. The conical twin screw (L/D) refers to the effective part length to the average of the two ends’ diameters.


From the above, we can clearly see that the most significant difference between parallel and conical twin-screw extruders is that the geometry of the screw barrel is different, which leads to many differences in structure and performance. But they have their own advantages.

Parallel twin screw extruder

Due to the small size of the center distance of the two screws, in the transmission gearbox, the space for the radial and thrust bearings supporting the two output shafts and the associated transmission gears is limited.

Although the designer has tried his best, it cannot be solved that the bearing capacity of the bearing, the modulus of the gear, the small diameter, and the small diameter of the tail of the two screws result in poor torsion resistance.

The output torque is small and the load resistance is poor, which is the most significant defect of the parallel twin-screw extruder.

However, the plasticity of aspect ratio is the advantage of parallel twin screw.

It can increase and decrease the aspect ratio to meet the requirements of plastic processing technology according to the difference of molding conditions, and can expand the application range of parallel twin screw, which is difficult for conical twin screw extruders are to achieve.

Conical twin screw extruder

 The two conical screws are horizontally arranged, and the two axes are inserted into the barrel at an angle.

The center distance of the two axes gradually increases from the small end to the large end so that the two output shafts of the transmission gear box have a large center distance.

The gears and gear shafts in the transmission system and the radial and thrust bearings supporting these gear shafts have a large installation space, which can accommodate larger radial bearings and thrust bearings, each of which has sufficient diameter for enough transmission torque, so the large working torque and large load capacity are major features of the conical twin-screw extruder, which is unmatched by parallel twin-screw extruder.

Twin-screw extruder retaining bearing

When the twin-screw extruder is working, the melt will generate a very large pressure (head pressure) at the head of the screw. The pressure is usually around 14MPA, sometimes even as high as 30MPA. This pressure creates a strong axial thrust on the screw. To withstand the thrust is the role of the bearing.

1. Parallel twin-screw extruder

The parallel twin-screw extruder is limited by the small center distance of the two screws. The bearing capacity of the thrust bearing is related to its diameter.

The larger diameter is, the larger the bearing capacity will be achieved. Obviously, it is impossible to use large-diameter anti-backup bearings.

This contradiction is usually resolved by connecting several small-diameter anti-backing bearings in series to withstand strong axial forces.

The core problem of using this method is that the load on each thrust bearing must be uniform, otherwise, it will withstand large load and the bearing is prematurely damaged due to overload.

And the load it should bear is added to other bearings to overload others. The consequences of this continuity of damage are very serious.

It can be seen that the transmission structure of the parallel twin-screw extruder is relatively complicated.

Compared with the transmission structure of the conical twin-screw extruder, the manufacturing cost of the gear box of the parallel twin-screw extruder is high and the maintenance is complicated.

2. The conical twin-screw extruder

The conical twin-screw extruder has an angle between the two screws, so the two output shafts of the transmission gearbox have a large center distance, and two thrust centering balls are arranged in the gear box.

The bearing is sufficient to prevent the axial force formed by the pressure of the head.

Thus its characteristic is that bearing capacity is large, the gear box manufacturing cost is low and the maintenance is convenient.
For the user, the purchase of twin-screw extruders is very important.

Different types of twin-screw extruders have different performances and applications.

Therefore, it is necessary to understand the performance of various twin-screw extruders and application.

For example, intermeshing co-rotating twin-screw extruders are widely used for the modification of non-thermally decomposable polymers due to their high rotational speed and high shear rate, combined with screw—blending, filling, fiber Reinforcement and reaction extrusion of the material. For example, the meshing counter-rotating twin-screw extruder has the characteristics of good mixing and plasticizing.

And its biggest feature is the direct molding of PVC powder. If the geometry of the screw is changed, it can also be used for the forming of other materials, but its strength is still PVC forming.

According to the size of the plastic section, the amount of extrusion is determined, and the specification of the twin-screw extruder is selected by the amount of extrusion.

In the case of substantially the same plastic processing conditions, the conical twin-screw extruder can accommodate larger head pressures, and the parallel twin-screw extruder can accommodate smaller head pressures.

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