How to Make a Choise Between Parallel and Conical Twin Screw Extruder?

Is the dual screw extruder better parallel or conical? This is a question that users often ask when purchasing equipment. Today we will discuss it in detail.


Ⅰ. The difference between parallel and conical twin-screw extruder


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


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


3. Length-to-diameter ratio: Parallel twin screw (L/D) refers to the ratio of the length of the useful part of the screw to the outer circle of the screw, and conical twin screw (L/D) refers to the ratio of the length of the useful part of the screw to the diameter of the small end , Conical twin-screw usually only indicates the diameter value (D/d) of the large end/small end of the screw.


From the above, we can see that the significant difference between the parallel and conical dual screw extruder equipment is that the geometry of the screw and barrel is different, which leads to many differences in structure and performance. Although the two characteristics are different, they have their own advantages.


Ⅱ. Parallel twin screw extruder and conical twin screw extruder


1. Parallel twin screw extruder


Due to the small center distance between the two screws, the space for the radial bearings and thrust bearings supporting the two output shafts and related transmission gears in the transmission gear is very limited. Although the designer has tried his best, it cannot be solved. The bearing capacity, the gear module, the small diameter, and the small diameter of the tails of the two screws lead to poor torsion resistance.


The most significant shortcomings of parallel dual screw extruders are low output torque and poor load resistance. The parallel twin-advantage screw's is the plasticity of the length-to-diameter ratio. To meet the requirements of plastic processing technology, it can increase and decrease the length-diameter ratio depending on the molding conditions. It has the potential to broaden the parallel dual screw's application range. Nonetheless, this point is conical. It is difficult to create a dual screw extruder.


2. Conical dual screw extruder


The two conical screws are placed horizontally, and the two axes are installed into the barrel at an included angle. The center distance of the two axes gradually increases from the small end to the large end. The two output shafts of the transmission gearbox have a larger center distance. The gears and gear shafts in these transmission systems and the radial bearings and thrust bearings that support these gear shafts leave a large installation space. It can be equipped with larger specifications of radial bearings and thrust bearings. Each transmission shaft has enough shaft diameter that transmits torque. Large working torque and large load capacity are major features of the conical twin-screw extruder. This parallel twin screw extruder is incomparable.

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