Parallel twin screw extruder, or conical twin screw extruder? It is the problem that users often ask when choosing twin screw extruder.

Classification of twin screw extruder.

According to the rotating direction of double screw, divides into the extruder direction and vision to the two kinds of extruder, synthetic two screw extruder works and rotate in the same direction, different to the extruder is refers to the two screw rotation while working in the opposite direction.

The two extruders can be divided into two kinds, which are parallel to the axis line and the axis line. The axial line is parallel to the twin screw extruder, and the axis line intersects the conical twin screw extruder.

The twin screw extruder also has meshing and non - meshing.

Parallel to conical twin screw extruder:

There is a mechanism for pushing forward the plastic, good mixing and plasticizing capacity, and the ability to dewater, which has basically the same adaptability to the material and plastic molding process.

The difference between parallel and conical twin screw extruders:

1. Diameter: the diameter of the parallel twin screw is the same, and the small end diameter of the conical twin screw is different from the larger diameter.

2. Concentric distance: the center distance of the flat twin screw is the same, the two axes of the conical twin screw are Angle, and the size of the center distance varies along the axis.

3, the length to diameter ratio: parallel twin screw (L/D) refers to the effective part of screw length and the ratio of the screw cylindrical, conical double screw (L/D) refers to the effective part of screw length and diameter of big end and small end diameter ratio of the average.

From the above, we can clearly see the parallel with conical twin screw extruder screw barrel is the most significant difference of different geometric shape, causing many differences of the structure and performance, although both characteristics are different, but have their respective advantages.

Parallel twin screw extruder.

Due to the center distance of two screw size limit, in the transmission gear box, to support two output shaft radial and thrust bearings and related gear space is limited, although the designers had his brains, but also is unable to solve the bearing capacity, the gear modulus, small diameter, the reality of the tail end of the two screw diameter small, lead to the results of the torsion resistance is poor. It is the most significant defect of parallel twin screw extruder. But the plasticity of length to diameter ratio is the advantage of parallel twin screw, it can be based on the differences of processing conditions, can increase and decrease the length to diameter ratio to meet the requirements for plastic processing technology, and can extend the scope of application of parallel double screw, but this conical twin-screw extruder is hard to do.

Conical twin screw extruder.

Two root conical screw horizontal arrangement, two axis in an Angle into the barrel, the center distance of two axis from the small to the big end increases gradually, make the transmission gearbox output shaft have two larger center distance, the transmission system of gear and gear shaft and bearing of the gear shaft radial and thrust bearings have larger installation space, it can device of the radial and thrust bearings of large size, the shaft is enough to meet the diameter of axle torque, so big torque, load bearing ability is an important characteristic of conical twin screw extruder. This parallel twin screw extruder is incomparable.

Check bearing of twin screw extruder.

Twin screw extruder, the melt in the screw head will produce very big pressure (pressure head), usually around 14 mpa pressure size, sometimes even up to more than 30 mpa, the pressure on the screw form the strong axial thrust, resist is to check back thrust bearing.

1, the parallel twin-screw extruder for restricted by two screw center distance is small, check back the size of the bearing capacity and its diameter of bearing diameter big carrying capacity, with large diameter backstop bearing is obviously impossible. This contradictory situation is usually in a number of small diameter backstop bearing together, jointly bear the axial force of strong, using this method is the core issue of each thrust bearing must be under the same load to uniform, otherwise, withstand large bearing early damage due to overload, it should carry the load to the other bearing overload, the continuity of the destruction of the consequences is very serious. It can be seen that the transmission system structure of parallel twin screw extruder is more complicated. Compared with the transmission system structure of conical twin screw extruder, the manufacturing cost of gearbox is high and the maintenance is more complicated.

2, conical double screw extruder with the arrangement of two screw Angle, so the transmission gearbox output shaft have two larger center distance, in the gear box unit before and after the two staggered larger thrust self-aligning ball bearings, enough to stop by the axial force formed by the pressure of the nose, the characteristics of bearing capacity is big, the gearbox manufacturing cost is low, maintenance is convenient.

For users, it is important to the choose and buy of twin screw extruder, the different types of twin screw extruder with different properties and applications, therefore, must want to understand all kinds of performance and the application of the twin screw extruder.

For example, the mesh type synthetic rotating twin screw extruder for its high speed, shear rate, combination of screw, it widely applies to the thermal decomposition of the polymer modification, blending, filling, fiber reinforcement and material of reactive extrusion.

For example, the meshing heterotope rotary twin screw extruder, because of its good mixing plasticizing function, its biggest characteristic is the PVC powder material direct forming processing. If the geometrical structure of screw rod can be changed, it can also be used for the forming process of other materials, but its strength is still PVC forming processing. According to the size of the plastic section, the extrusion quantity is determined and the specification of twin screw extruder is selected.

Under the same conditions of plastic processing and forming process, the conical twin screw extruder ADAPTS to the larger head pressure, and the parallel twin screw extruder ADAPTS to the smaller head pressure.