Causes and solutions of broken strips in twin-screw extrusion pelletizer


The screw and barrel of the twin-screw extrusion pelletizer are the two core components of the work of the pelletizer, which have a key influence on the plasticization of materials and production efficiency. After a long period of operation, the screw and barrel are prone to damage, a common fault is the twin-screw extrusion pelletizer’s broken bars, twin screw pelletizer does not eat material, when the twin-screw extrusion pelletizer when these two failures how deal with it? Here to understand the following.

Causes and solutions of broken strips in twin-screw extrusion pelletizer

1. twin-screw extrusion pelletizer breaks the causes and solutions

1. the cause of foreign impurities

(1) should check the equipment in the mixing and discharging link of the dead end is cleaned up, and whether there are impurities mixed in.

(2) Increase the number of filters and pieces.

(3) Try to add less crushed material or manually sieve the crushed material to remove impurities.

(4) Try to cover the holes where debris may fall (solid cover or mesh cover).


2. Causes of internal impurities

The main reason is the serious carbonization caused by the process or equipment, which brings the carbonized material out of the strip and causes the strip to break under traction.


3. Material plasticization is poor

(1) formula system in the low melting point additives (including EBS or PETS, etc.) in the screw shear force is weak or screw and barrel clearance increases, the premise of the shear force decreases, will cause poor plasticization, broken strip weak.

(2) extrusion temperature is too low or screw shear force is too weak, the material is not fully plasticized, appearing agglomerates, in the traction effect caused by the strip break.


4. the difference or change in the physical properties of raw materials

(1) change in viscosity of the blended component: for the same material, if the MFR decreases, the hardness, stiffness and gap become larger, it is possible that the molecular weight of the batch is larger than before, leading to an increase in viscosity. Under the influence of higher processing temperatures and processes, this results in poor participation. This can be solved by increasing the extrusion temperature or reducing the host screw speed.

(2) The difference in fluidity of the blended components at the same temperature is too great, due to a mismatch in fluidity or incomplete compatibility (including physical entanglement and chemical reactions), which is theoretically called “phase separation”. “Phase separation” generally does not occur in the blended extrusion, but more often occurs in the injection molding process, but if the MFR difference is too large, the screw shear force is the relatively weak premise, and may occur fracture.

2, the twin-screw pelletizer does not eat material is what happened

As the twin-screw is hungry extrusion, rarely does not eat material phenomenon, if the pelletizer does not eat material phenomenon, it will affect the production efficiency of plastic pellets, so once appeared to solve as soon as possible. The following is to introduce the pelletizer that does not eat the causes and solutions.

1. the material moisture is not suitable

Too much or too little material moisture will clog the die hole, resulting in the pellet mill does not discharge material. In this case, check the summary material and control the moisture between 10% and 15%.


2. die platen and pressure roller wear serious

Die platen and pressure roller is the main accessory of the granulator, but also vulnerable accessories. If the attachment is aging or malfunctioning, it is also the reason why the granulator does not dispense material. If the pelletizer is new, you only need to see which attachments are not working to be able to tell which problems are present. If you use the granulator for many years, it means that the accessories are aging and can be replaced.


3. the die compression ratio is not appropriate

Different materials require different compression ratios of the die. Choosing the regular large manufacturers will be customized according to the customer on the basis of customer needs. Generally speaking, this problem will not occur. If there is no material, check the compression ratio of the mould. If it is not suitable, replace the material mould.


4. High coarse fiber content of the material

Pelletizing machines are available in different models and powers. For different models of granulators, the granulation requirements are different. Some granulators are suitable for pressing coarse fibers and some for pressing fine fibers. If you choose a small pelletizer to press coarse fiber material, this is also the reason why the pelletizer does not produce material. The solution is to communicate with the manufacturer and replace the granulator.


5. The spacing between the die and the roll is not appropriate

The pellet mill promotes the formation of pellets by squeezing the accessory rolls and dies. If the spacing is not appropriate, it can also lead to the pellet mill not feeding properly. The solution is to adjust the spacing.


6. Pelletizer with accumulated material inside

After the pelletizer has been produced, there will be some accumulation of material and no clean residue will be discharged. The next time the pelletizer runs, it will solidify into a hard mass due to the high temperature, causing the pelletizer to fail to unload properly. The solution is to clean the inside and clear the residue.


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