Classification of Threaded Components of Extruder


The types of extruder thread elements can be divided into forward thread elements and reverse thread elements:

1. Forward threaded elements

The positive thread element is mainly used for conveying materials. The groove shape of the forward threaded element may be rectangular or other shape. At present, the shape of spiral groove is mostly used.

2. Reverse thread element

The shape of the reverse thread element in the extruder thread element is similar to that of the normal thread element, except that the spiral direction of the thread groove is opposite. Since the direction of the material conveyed by the reverse thread is opposite, and the material conveyed by the positive thread is the extrusion direction, the material accumulates a high pressure in front of the entrance of the reverse thread section to overcome the resistance generated by the reverse flow and let the material pass through The gap of the reverse thread is transmitted forward. In the extruder, sometimes according to the needs of the process, to form different pressure zones in different positions or closer to the axial direction of the screw, the threaded element can achieve this purpose. For example, a liquid additive or foaming agent is added at a certain position in the axial direction of the screw. The addition location must be in the low pressure area. At this time, a reverse thread element is arranged before the adding zone to form a high pressure and play a sealing role to prevent the liquid additive or foaming agent from flowing in the opposite direction. And a low pressure zone is formed behind the reverse thread element to facilitate the addition of additives or foaming agents. A reverse thread element is installed in front of the exhaust port, which can form a high pressure in front of the exhaust area, and suddenly reduce the pressure in the exhaust area to facilitate exhaust.

The reverse thread element in the extruder thread element itself has no forward conveying capacity, and the forward conveying of the material is at the cost of pressure loss. The pressure drop of the reverse threaded element is an important factor that must be considered when designing and selecting the element. The reverse thread element is a resistance element, and the pressure increases. A positive thread conveying element should be set in front of it to overcome its resistance and convey the material to the direction of the die. One pressure peak will appear with the addition of a reverse thread element, two pressure peaks will appear with the addition of two reverse thread elements: and so on, as many as you need.

classification of extrusion machine thread elements:

1. Conveying element

The conveying element has a positive and negative score, and its function is different according to the lead, the depth of the falling groove and the width of the screw edge. Generally, with the increase of the lead, the amount of extrusion increases, the residence time of the material decreases, and the mixing effect decreases. Reverse thread components are mostly used to seal the melt, establish high pressure, and promote the melting and plasticizing of the material.

2. Engaging block elements

The meshing block mainly produces extrusion, shearing and stretching effects on the material, which can promote the conveying, melting and mixing of the material. Its function is affected by the direction, thickness, angle and number of combined sheets of kneading sheets.

The greater the thickness and length of the kneading disk of the forward kneading element, the more favorable the shearing and plasticizing of the material;

The greater the thickness, length and angle of the kneading disc of the reverse kneading element, the greater the reverse resistance of the material, and the more conducive to the shearing and plasticization of the material;

3. Special components

Tooth shape, mainly to disturb the material flow, accelerate the homogenization of the material. Generally, the more teeth, the stronger the mixing, but pay attention to the destructive nature of high shear when using it.

The above is a detailed introduction to the classification of screw elements of the extruder, and I hope it will be helpful to you.


Keywords: Classification of Threaded Components of Extruder

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