Common problems and solutions for TPE extrusion granulation

Q1.The length is larger than the normal pellet

A: Cause of occurrence:

The main reasons are: starting the machine, pulling or breaking the strip, the direction of the strip is not straight, the strip is not properly soaked in water, and the cutting tool of the granulator is worn or has gaps.

Main solutions

1) During normal production, adjust the direction of the material strip entering the granulator and adjust the immersion length;

2) Severe breakage during production requires adjustment of the extrusion process;

3) Pay attention to the inspection of the cutting blade and replace damaged blades in a timely manner;

4) Suitable vibrating screens can be used to screen the long strips.

Q2. Connecting pellets

A: Cause of occurrence:

The main reasons for the connecting pellets granulation of modified materials are that the strip is not divided or broken in time when pelleting, the length of immersion is not enough, and the temperature of the machine head is too high.

Main solutions:

1) When extruding, select a guide strip nylon wheel with a suitable width, and timely separate the material strips that are stuck together;

2) Adjusting the appropriate cooling immersion length to prevent overheating of the material strip can reduce connecting pellets granulation;

3) Reduce the temperature of the machine head appropriately and adjust the temperature of the material strip;

4) For the occurrence of connecting pellets, a vibrating screen with appropriate mesh size can be used for screening.

Q3. Centipede strip

A: Cause of occurrence:

The main reasons for this are the speed of the pelleting, the discharge port of the twin screw extruder, insufficient immersion length, wear of the cutting tool of the pelletizer, or excessive gap between the fixed and moving blades.

Main solutions:

1) When the operator pulls the strip, it should be done at a uniform speed to avoid excessive thickness of the strip;

2) Adjust the appropriate extrusion process to avoid material overflow at the feeding port;

3) Adjust the appropriate cooling immersion length to avoid overheating of the strip;

4) Adjust the gap between the fixed tool and the moving tool. If not, replace it with a new tool

Q4. Black spot

A :Reason for occurrence:

The screw is not delivered clean;

There are black spots in the raw materials;

Screw carbonization;

Environmental pollution;

Artificially brought in.

Main solutions:

1) During the process of converting the product to a screw, if it is not cleaned thoroughly, it is sufficient to pull the screw again; Cleaning points: "Three ports", the screen behind the filter screen and the large machine head;

2) Strengthen incoming inspection, especially black spots and impurities are more likely to appear in filled mineral powder or flame retardants; For example, Z30S or T30S granules containing wood chips in the package, low-grade filling mineral powder or flame retardant; These cannot be used to produce modified plastics with strict black spot requirements.

3) Pay attention to control and adjust the barrel temperature and the residence time of materials in the barrel to prevent the processing temperature from being too high; That is, the extrusion process corresponding to each product should be designed according to its formulation.

4) It is necessary to pay attention to the hygiene of the surrounding environment and keep the ground moist, and to isolate and protect the machines for producing products of different colors.

5) Regularly clean the auxiliary equipment of the extrusion equipment, such as the sink and pelletizer;

6) Every time the mesh is changed, the remaining materials on the mobile mesh plate and template must be cleaned to prevent carbonization over time;

7) Pay attention to the fact that the ground material strip is strictly prohibited from entering the granulator to prevent dust from entering;

8) Prevent the generation of plastic static electricity, which can easily absorb dust;

Q5. Discoloration

A :Reason for occurrence:

Uneven or incorrect mixing of materials;

The cleaning machine is not clean;

The temperature is too high;

Shear too strong; There are impurities in the backfill material.

Main solutions:

1) Strictly follow the mixing process to ensure the uniformity and correctness of the mixture;

2) After the cleaning is completed, a special person will inspect to ensure that the cleaning is clean;

3) Control the extrusion temperature to prevent excessive temperature from causing color powder decomposition;

4) Choose a suitable combination of screws and avoid too strong shear;

5) Confirm that there are no impurities in the backfill material.

Q6. Poor vacuum

A: Reason for occurrence:

Insufficient vacuum, vacuum return, damaged vacuum system, poor sealing, etc.

Main solutions:

1) Regularly inspect and maintain vacuum pumps and vacuum pressure gauges;

2) Timely clean the vacuum tank, vacuum chamber, and vacuum pipeline.

3) Properly control the flow rate of circulating water in the vacuum pump;

4) Solve vacuum return and ensure the sealing of the vacuum cover.

Q7. Iron filings or other metal particles on the surface or in the middle of plastic pellets

A: Reason for occurrence:   

The screw wears, the knife is broken, and there are iron filings or other metal particles in the raw material.

Main solutions:

1) Check if there is any damage to the screw, moving knife, vibrating screen, etc;

2) Check whether there are corresponding metal particles in the raw materials;

3) For defective products, strong magnetic or other metal separators can be used to screen out metal particles;

4) Add a filter screen to non enhanced machine.

Q8. Poor plasticization

A: Reason for occurrence:

The heating temperature is too low, there are impurities in the raw materials, the feeding speed is too high, the screw shear is too weak, and there is too much lubricant in the formula.

Main solutions:

1) Control the temperature according to the process regulations, and adjust the temperature appropriately when any plasticization defects are found;

2) Check if there are impurities or insoluble substances mixed in the raw materials;

3) Properly control the feeding speed to increase the heating and plasticizing time of the plastic;

4) Choose a combination of screw elements with moderate shear capacity;

5) Adjust the formula appropriately.

Q9. Excessive moisture content

A :Reason for occurrence:

The material strip is soaked too much, and the strip is not divided in time when driving. The speed of the pelletizer is too fast, the wind force of the blade is too small, and the distance between the pelletizer and the blade is too close.

Main solutions:

1) Adjust the immersion length of the strip appropriately;

2) When pulling the strip, the material strip enters the granulator and is immediately divided into strips;

3) Adjust the speed of the pelletizer appropriately, and at the same time, adjust the height of the leveling strip support appropriately;

4) Ensure that the wind force of the wind blade is strong enough, and if necessary, use two wind blades;

5) Adjust the distance between the pelletizer and the air knife appropriately.

Q10. After being cut by a pelletizer, the shredded material strip produces many small, fragmented particles.

A :Reason for occurrence:

The strip is immersed in too much water, the pelletizer tool is worn, the filler is too much, the strip is too hard, etc

Main solutions:

1) Adjust the amount of water soaked in the strip appropriately;

2) Replace the cutting tool with a new one;

3) Adjust the formula appropriately to reduce the distance between the pelletizer and the air knife

Q11. The leaked material at the carbonization die head turns into black material, and granular burnt objects appear on the plastic surface

A :Reason for occurrence:

The heating temperature is too high, causing the melt to scorch;

Long term use of screw without cleaning results in the accumulation of burnt substances;

The shutdown time is too long, and the machine head and screw are not cleaned.

Main solutions:

1) Frequently check whether the heating system is normal, and if there is any problem with the heating system, solve it in time;

2) Regularly pull out the screw or clean the machine head, and thoroughly clean it;

3) The mesh plate, filter screen, and die head should be cleaned in time to prevent carbonization, and the machine head and screw should be cleaned immediately when carbonization is found.Clean and prevent carbonization. If carbonization is found, immediately clean the machine head and screw.